View Full Version : Gas to Piston
I searched around, and couldn't find much on the subject. Anyhow, I recently purchased a Smith & Wesson M&P15-T for duty use at my Department. I was curious to hear what peoples thoughts were on changing a gas system to a piston system. I know Adam Arms makes such a system for around $350.00.
Since this would be a duty rifle I was wondering if it would be beneficial to perform such a conversion? Would there be any risk, or possible complications down the road. Any major pros or cons? Am I better off not messing with it?
Robb Jensen
01-08-11, 06:13
Our search feature pulled up more than 11 pages.
https://www.m4carbine.net/search.php?searchid=2638404
Just my take on it... I am a Police Officer who is assigned to a Tactical Team as both an operator and K9 handler. I have both weapons systems.. And there is nothing wrong with the good old gas system. If you bought the weapon configured as a gas system, I wouldn't mess with it. The cons out way any Pro.
Althought the Piston System does have its place IE; Short barrel weapon!! Having said that, my favorite weapon platform is my LMT MRP Piston System. If your heart is set on having a Piston System then buy a piston system that is already designed to run as such. IE; LMT MRP Piston, POF System or the LWRC System. Hope this helps some...
Be Safe Out There!!!
My M&P15T has been flawlessly reliable over thousands of rounds. Can't really improve on that....100% reliable is 100% reliable, period.
Personally I'm also not even a fan of gas piston systems. I was brought up on the British SA80 family of rifles....I found cleaning the gas piston assembly to be much more of a pain in the ass than cleaning the ARs DI system, IMO.
Doesn't S&W offer piston system from the factory based on the Adams Arms unit? Answered my own question after I posted:
http://www.smith-wesson.com/webapp/wcs/stores/servlet/Product4_750001_750051_765756_-1_757785_757784_757784_P
Am I better off not messing with it?
Bingo. I would never want or recommend installing one of those on a real-use gun. The DI system is a proven performer. What problems have you had with it that warrant a change?
(Unless you just want more moving parts, more weight, and a cycling system that require more cleaning in more places, requires added parts be installed in your upper receiver, limits your handguard options, uses inferior or unknown quality steels, and limits you to a clamp on gas block, and after going out of business you won't be able to find their proprietary parts to maintain your rifle, then go for it.)
Bingo. I would never want or recommend installing one of those on a real-use gun. The DI system is a proven performer. What problems have you had with it that warrant a change?
(Unless you just want more moving parts, more weight, and a cycling system that require more cleaning in more places, requires added parts be installed in your upper receiver, limits your handguard options, uses inferior or unknown quality steels, and limits you to a clamp on gas block, and after going out of business you won't be able to find their proprietary parts to maintain your rifle, then go for it.)
I think your 'assessment' is a bit overstated. There is one more moving part, a piston/oprod. Requires LESS cleaning, period. One non-moving part in the upper. Quality of steel statement is unfounded. Several manufacturers use top grade materials and manufacturing processes in their piston systems. Does NOT limit you to a 'clamp-on' gas block depending on manufacturer.
There are other issues though like carrier tilt. Some say they have remedied it. I do agree that there is currently no standardization amongst the manufacturers.
William B.
01-08-11, 11:04
I searched around, and couldn't find much on the subject. Anyhow, I recently purchased a Smith & Wesson M&P15-T for duty use at my Department. I was curious to hear what peoples thoughts were on changing a gas system to a piston system. I know Adam Arms makes such a system for around $350.00.
Since this would be a duty rifle I was wondering if it would be beneficial to perform such a conversion? Would there be any risk, or possible complications down the road. Any major pros or cons? Am I better off not messing with it?
Why don't you shoot the crap out of it with the standard DI gas system first? Let it prove itself to you before you consider fundamentally changing the operating system.
Raven Armament
01-08-11, 11:08
I love the "DI vs GP" threads. Many people don't realize the "DI" system is a piston system. In the "DI" system, the piston is the bolt carrier. In the "GP" system, the piston is located above the barrel in a separate unit. The major difference is how far the gas travels to operate the action.
Failure2Stop
01-08-11, 11:09
If going to a piston gun, I highly recommend getting one that was designed from the ground up to be piston operated.
The AR simply isn't.
There isn't anything wrong with piston operation, and it does offer advantages over DI, especially if you want to run it with and without a suppressor. Some piston designs/executions are better than others, just like overall designs, and I have seen no data that puts any piston AR over contemporary piston designs.
Littlelebowski
01-08-11, 12:00
Can we lock this, mods?
Magic_Salad0892
01-08-11, 13:56
We need a piston v. DI sticky thread, and just lock all the other ones.
:|
This is getting really... not so smart... these DI v. GP threads are better left to TOS.
I still regret arguing for the pistons in 87GN's thread, as I am wholeheartedly a DI believer now.
Robb Jensen
01-08-11, 14:30
The problem with stickies and that NO ONE reads them. The SEARCH feature is hardly used as well.
Thanks for all the replies gentlemen. The feedback was definitely useful. I'm a LEO out here in California. So besides the department AR's we never really get to play with them, or customize them that often. So forums like this help me out greatly. I'm just happy to finally be able to get my hands on my own AR. It amazing how many things they make for it.
So far for my M&P15-T I've bought Eotech 553, Vickers Blue Force Sling, and some other minor sling mounts. For duty use. Does anyone suggest any other upgrades? I was thinking about another stock, and charging handle. Like I said, there are so many options.
pilotguyo540
01-08-11, 20:32
Thanks for all the replies gentlemen. The feedback was definitely useful. I'm a LEO out here in California. So besides the department AR's we never really get to play with them, or customize them that often. So forums like this help me out greatly. I'm just happy to finally be able to get my hands on my own AR. It amazing how many things they make for it.
So far for my M&P15-T I've bought Eotech 553, Vickers Blue Force Sling, and some other minor sling mounts. For duty use. Does anyone suggest any other upgrades? I was thinking about another stock, and charging handle. Like I said, there are so many options.
Buy ammo and shoot the hell out of it. You will only then know what you want.
Forget this silly nonsense about piston conversions.
Where are you in Kali? One of us would probably be willing to burn brass with you.
I love the "DI vs GP" threads. Many people don't realize the "DI" system is a piston system. In the "DI" system, the piston is the bolt carrier. In the "GP" system, the piston is located above the barrel in a separate unit. The major difference is how far the gas travels to operate the action.
Right.
The creators did a dis-service by calling it the "direct impingement" operating system.
They should have called it "integrated piston" or "inline piston" or something like that.
As a piston owner...don't bother. Not that there is anything wrong with my piston gun (LMT), but because you won't really get any benefit from the $350. Unless you get in a firefight so long you shoot the gun dry (which isn't likely in LE, and .mil guns are still DI anyway), the piston can't really help.
Spend the $350 on ammo or towards training. BCM Gunfighter charging handles sure are handy tho...and only $44.
Magic_Salad0892
01-09-11, 00:10
I would say throw in a BCM Gunfighter.
If you do spend money on ammo, the CH will break eventually if you run it kind of violently. Standard GI handle is kind of flimsy.
I think your 'assessment' is a bit overstated. There is one more moving part, a piston/oprod. Requires LESS cleaning, period. One non-moving part in the upper. Quality of steel statement is unfounded. Several manufacturers use top grade materials and manufacturing processes in their piston systems. Does NOT limit you to a 'clamp-on' gas block depending on manufacturer.
There are other issues though like carrier tilt. Some say they have remedied it. I do agree that there is currently no standardization amongst the manufacturers.
Less cleaning my eye. You now get to clean not only your receiver and bcg, butalso your handguard or rail and front sight and whatever other crap is hanging up front. Still have a bolt and carrier to clean. Still have crap in the upper. The 'so much easier to clean!' nonsense is just that.
Types of steel. Who uses what? Is somebody using 8620 or 158 in their carriers or bolts? Could yougivean example of a piston manufacturer using the same or better quality as a gi counterpart? Fair enough on the clamp gas block comment, however a popular piston system does rely on it.
I just don't see why some view this idea as an 'upgrade'. It's a step backwards in my opinion.
typing on a mobile device, please excuse the errors.
Wasnt even aware they had kits that offered method conversions. I would be impressed if it wasnt for just buying a piston system off the bat. I wouldnt feel too secure about changing out my stock operating system. Not on a reliable weapon i routinely use/rely on anyways. Maybe on one i dont care much for (wheres that little Red Ryder BB gun:p)
Less cleaning my eye. You now get to clean not only your receiver and bcg, butalso your handguard or rail and front sight and whatever other crap is hanging up front. Still have a bolt and carrier to clean. Still have crap in the upper. The 'so much easier to clean!' nonsense is just that.
Dude, I think it is pretty clear you have little or no experience with a piston system. They are in fact much easier to clean, particularly the internals, no comparison to DI. To say anything else is ludicrous and demonstrates a complete lack of understanding of both piston and DI systems.
of steel. Who uses what? Is somebody using 8620 or 158 in their carriers or bolts? Could yougivean example of a piston manufacturer using the same or better quality as a gi counterpart? Fair enough on the clamp gas block comment, however a popular piston system does rely on it.
You could try a bit of research on your own time to educate yourself, but in the interest of discussion, try Barrett, LWRC, HK, LMT.......
just don't see why some view this idea as an 'upgrade'. It's a step backwards in my opinion.
typing on a mobile device, please excuse the errors.
I don't think anyone said it was an upgrade, you wanted to interpret it as such I guess for the argument. What was said were your inaccurate claims as follows:
(Unless you just want more moving parts, more weight, and a cycling system that require more cleaning in more places, requires added parts be installed in your upper receiver, limits your handguard options, uses inferior or unknown quality steels, and limits you to a clamp on gas block, and after going out of business you won't be able to find their proprietary parts to maintain your rifle, then go for it.)
I am not saying they are better or worse because don't care either way. If you don't like a piston system that is your prerogative, but base your opinion on facts and personal experience, not on supposition and the 'experience' or lack thereof of internet website participants, particularly when you haven't investigated the merits nor faults of the system.
I searched around, and couldn't find much on the subject. Anyhow, I recently purchased a Smith & Wesson M&P15-T for duty use at my Department. I was curious to hear what peoples thoughts were on changing a gas system to a piston system.
Ares Defense GSR-35: gas system retrofit range report.
Since I personally have never had any reliability issues with my direct gas impingement system AR-15s, my interest in a gas piston system is due mainly to curiosity. (Isn’t that what killed the cat?) The possibility of having to spend less time cleaning the bolt carrier group and upper receiver is also rather appealing.
Proponents of the gas piston system for the AR-15 claim it is more reliable than the direct impingement system, (which seems rather ironic since the gas piston system not only adds more parts to the overall system, but adds more moving parts as well.) Opponents of the gas piston system state the AR-15 does not have reliability issues as long as proper cleaning and maintenance procedures are followed. They also claim that the gas piston system causes a decrease in the accuracy of the AR-15.
There are a few different gas piston systems for AR-15s on the market, but most of them are proprietary affairs. The allure of the Ares Defense GSR-35 is that it is user installable on your existing AR-15. The GSR-35 kit comes with everything you need to convert your existing system to a piston system, including a set of modified M4 handguards.
http://www.box.net/public/static/fu24c9zfc4.jpg
You use the bolt from your existing system but remove the gas rings to run with the gas piston system. I chose to use a Smith Enterprise chrome plated bolt as this would more easily show the fouling on the bolt for comparison. I also chose to use a 16” HBAR for my testing and evaluation of the GSR-35 with the rationale that a heavy barrel would be the least likely profile to show a decrease in accuracy (if it actually did occur). If a substantial decrease in accuracy was found using the gas piston system with an HBAR, there would be no point in even testing the system with a government profile or light-weight profile barrel. The 16” HBAR I used for the conversion is a new chrome-moly barrel (not chrome lined) of uncertain pedigree. (I think it was made from a Douglas blank, but it’s been sitting on my spare parts shelf for so long I’m not sure.) The barrel is stamped as having a 5.56mm chamber and a 1:9” twist.
Upon removing the GSR-35 kit from the box, I was disappointed to see that the gas spigot was bent. It was only slightly angled away from the gas cylinder, but you would think Ares Defense would hold a higher level of quality control on such a crucial piece of their system.
The Ares defense literature states their gas system is designed to work with “mil-spec” AR-15s. I decided to deviate a bit from the “mil-spec” by using a JP Enterprises adjustable gas block, for three reasons.
1.The JP gas block uses an extra long roll pin to secure the gas tube/gas spigot. I thought this would help to mitigate any problems with the roll pin walking-out during firing, (as has been reported.)
2.The JP gas block is secured to the barrel using set screws. I wanted to see if a set screwed gas block could withstand the additional forces applied to it by a gas piston system.
3.The JP gas block is adjustable. I thought this might prove for some interesting experiments if the gas piston system proved useful. (The gas adjustment was left “wide open” for this evaluation.)
Before installing the GSR-35 system on my carbine, I performed some informal accuracy testing from a distance of 50 yards using the direct impingement gas sytem. The forearm of the rifle was placed on a sandbag resting on a wobbly table. There was no support for the butt-stock (nor for my elbows.) The ammunition used was one of my hand-loads, using Sierra 52 grain MatchKings and VihtaVuori N135 powder. As well as being an extremely accurate load, this load has functioned flawlessly in every AR-15 I own.
I fired three 10-shot groups in a row that measured, 0.558”, 0.408”, and .570” for an average group size of 0.512”. The targets are pictured below.
http://www.box.net/public/static/2jn8sv8um0.jpg
Dennysguns has done a great job of describing the installation of the GSR-35, so I’ll not go into that here. As I mentioned earlier, the gas spigot from my kit was slightly bent. When installed on the carbine, this caused the gas cylinder to angle very slightly to the starboard side of the barrel. This in turn caused some very slight binding at the juncture of the gas cylinder/gas piston/connecting link.
before conversion
http://www.box.net/public/static/sb8xgcjvq4.jpg
after conversion
http://www.box.net/public/static/uknfhbli69.jpg
http://www.box.net/public/static/9l2rosnoqp.jpg
I began function testing of the newly converted carbine by loading and then firing a single round at a time from a magazine for the first ten rounds and then 3 rounds at a time for the next several magazines. I experienced multiple failures of the bolt to lock back after the last round of the magazine was fired. I don’t know if this was do to the slight binding of the mechanism I mentioned above, or if the system just needs a little “breaking in.” After approximately 30 rounds the bolt began to lock back consistently. There were no further malfunctions during testing.
I performed informal accuracy testing with the GSR-35 system installed on the carbine in the same manner as described above. The three 10-shot groups that I fired from 50 yards measured, 0.677”, 0.501” and 0.879” for an average of 0.685”. (targets pictured below) This does demonstrate a decrease in accuracy (larger average group size) using the gas piston system compared to the direct impingement system, albeit a rather small one at approximately 0.35 minutes of angle with this 16” HBAR.
http://www.box.net/public/static/zu0xyd4xfh.jpg
I fired a total of 90 rounds for this first test session of the GSR-35 and here is what the bolt and carrier looked like afterwards; (pictured below) not nearly as much fouling as would have been present with a direct impingement system. Below is a picture of the inside of the upper hand-guard. This is where the fouling goes with the gas piston system. I was pleased to note that the JP gas block had not shifted forward at all during testing; nor was there any sign of rotational shifting. Also, the roll pin securing the gas spigot held tight.
http://www.box.net/public/static/7p9uyme6ud.jpg
http://www.box.net/public/static/ion0ma72ij.jpg
Over the next few months, I plan to fire 1,000 rounds of ammunition from the GSR-35 converted carbine without cleaning the gas system. If there are no further malfunctions/problems, I will be doing some formal accuracy testing of the system from 100 yards. If the results from that testing are acceptable, I’m going to repeat this course of testing with a GSR-35 installed on a 16” government profile barrel.
Here’s a pic of my GSR-35 carbine.
http://www.box.net/public/static/szhlz50xgr.jpg
The highest part of the GSR-35 above the barrel on my carbine is the section on the gas cylinder just aft of the spigot. It's the shiny spot on the gas cylinder with the red arrow pointing to it in the picture below. The shiny spot was caused by the gas cylinder rubbing against the the underside of the upper handguard.
http://www.box.net/public/static/htx28ncl8l.jpg
Here are some pics showing the differences between the two sets of handguards from the inside.
http://www.box.net/public/static/15lncuh2k7.jpg
http://www.box.net/public/static/ms1kzohvc6.jpg
Today I fired 90 rounds through one of my direct impingement 16” uppers. Here are some pics showing the Smith Enterprise bolt carrier group from that upper compared to the Ares GSR-35 bolt carrier group after firing 90 rounds.
http://www.box.net/public/static/eh60ogatao.jpg
http://www.box.net/public/static/dluz4n39bb.jpg
I fired an additional 89 rounds through the Ares equipped carbine without a single malfunction. When pulling the trigger on the 90th round, all I heard was the dreaded “click.” I kept the carbine pointed downrange for 20 seconds and then examined the ejection port. The bolt had failed to close completely on the round going into the chamber. The bolt carrier still had 1/8" to 1/4" of forward travel to go.
I dropped the magazine and attempted to clear the chamber by pulling back on the charging handle, several times. The action was locked up tight. The lugs on the bolt had just barely started to turn and therefore were engaged with the lungs of the barrel extension. I finally had to slam the buttstock against the ground while pulling on the charging handle to clear the weapon.
At that point, I chose to pause the testing until I could determine the cause of the malfunction. Upon returning home, a quick visual inspection of the bolt carrier group, chamber and gas system revealed no obvious abnormalities. I cycled a couple of dummy rounds through the action with no malfunctions.
I next turned my attention to the cartridge involved with the malfunction. I dropped the cartridge into a JP Enterprises chamber gauge and the cause of the malfunction became painfully clear. The cartridge failed to completely seat in the gauge. Here is a pic of a cartridge properly seated in the chamber gauge and then one of the cartridge that caused the malfunction.
http://www.box.net/public/static/qekudabaou.jpg
Scharch case.
http://www.box.net/public/static/qie009q1p2.jpg
I checked the headspace of the abnormal cartridge using an RCBS Precision Mic. The headspace measured +0.008”. That’s 8 thousandths of an inch longer than nominal headspace for the caliber. Obviously the case had not been properly resized and that is why it failed to completely chamber in the Ares carbine. I checked the headspace on the remaining 30 rounds that I had loaded for this test session and found two more cases that were not properly resized.
Since RVO is no longer a reliable source for once-fired and resized Lake City cases, I had decided to give the once-fired and resized cases from Scharch Mfg. a try. That is the source of the cases that I had used in this test session. This is the first time that I have ever had one of my hand-loads fail to chamber.
Since I am confident that the malfunction was due to the ammunition and not the Ares gas system, testing will continue. However, I will be chamber checking all the cases before heading to the range. Here’s a pic of the bolt and carrier after a total of 180 rounds fired.
http://www.box.net/public/static/o157zifk7q.jpg
300 rounds
I fired another 120 rounds through the Ares equipped carbine today without a single malfunction. (I used virgin Lake City brass for the handloads this time.) Here are a couple of pics showing the bolt/carrier group and Ares gas system after a total of 300 rounds.
http://www.box.net/public/static/nyfk4lek3u.jpg
http://www.box.net/public/static/jc9zq5kfje.jpg
The inside of the lower receiver looks as if it has hardly been used. The magazines are still remarkably clean also.
Just for kicks (and to prove a point) I fired some 75 grain A-MAX loaded rounds from the Ares upper from a distance of 25 yards. The 10-shot group is pictured below. Check out the key-holing!http://www.ar15.com/images/smilies/anim_shock.gif
http://www.box.net/public/static/0n9igns8zi.jpg
400 rounds
I fired another 100 rounds through the Ares upper today without a single malfunction. After a total of 400 rounds there has been no walking-out of the gas tube pin nor any movement of the JP Enterprises gas block.
Something I noticed today after doing some close range reflexive shooting drills is that the handguards seem to heat up quicker with the Ares system than with the DI system; particularly near the front of the handguards where the gas vents from the gas cylinder. I may have to invest in an infrared thermometer to determine if this is actually the case.
Here is a pic of the bolt and carrier group after the accumulated 400 rounds of firing and below that a pic showing a comparison from the individual test sessions.
http://www.box.net/shared/static/htsf2cnziu.jpg
http://www.box.net/shared/static/0mkq9o57st.jpg
One of the attractive aspects of the Ares unit is that you can easily convert back to the DI system if you so desire with no adverse affect to your weapon (and then use the Ares unit to convert another DI system to the piston system if you like.) It's too soon for me to make recomendations for the system. For example, I perceived the handguards heating up quicker with the Ares system in my recent test session. I don't know what affect, if any, this will have during extended shooting sessions or long term usage. For my next test session I plan to put a lot more rounds downrange in one outing.
I will tell you this, I definitely like the decreased fouling in the receivers and bolt carrier group. Also, while there may be a slight decrease in accuracy when using the Ares system, the accuracy is still more than adequate for my intended use. In the last test session I fired the 10-shot group pictured below from 50 yards in an informal accuracy check, using handloaded 55 grain V-MAX bullets. The group measures 0.632”. While not minute of angle, it is certainly good enough for government work.
http://www.box.net/shared/static/5m8tvj1pyq.jpg
550 rounds
I ran 150 rounds through the Ares upper today without a single malfunction for a total of 550 rounds. The bolt is getting fouled at this point, but I can still see shiny chrome on it!
http://www.box.net/shared/static/burd8k3kv3.jpg
700 rounds
Another 150 rounds went through the Ares upper today with almost monotonous reliability. That makes a total of 700 rounds through the Ares upper with no additional malfunctions since the 180th round. Remember, that malfunction was due to the ammunition.
Using the Ares upper and 55 grain FMJ handloads, I fired a quick 10-shot group from 50 yards on a 300 yard E2 silhouette target reduced for 50 yards. The results are pictured below, showing that while the Ares system might not produce MOA accuracy, it is certainly good enough for practical shooting situations even when using FMJ rounds.
http://www.box.net/shared/static/m98jvh4935.jpg
Here's a pic of the bolt carrier group after 700 rounds.
http://www.box.net/shared/static/vyhr0xy9iy.jpg
800 rounds
800 rounds and counting with no further malfunctions to report. 200 rounds to go!
http://www.box.net/shared/static/vmrrj5cvbc.jpg
920 rounds
As I mentioned in a previous post, I wanted to let the Ares carbine sit idle for a few weeks without cleaning as part of the testing. I've read that even the gas piston on the AK can freeze-up and need a little kick start on the charging handle if the weapon is not fired for a while.
So, after letting the carbine sit for 4 weeks I headed back to the range. I fired another 120 rounds through the upper without a single malfunction. At this point, I decided to end the reliability testing. I didn't think another 80 rounds would uncover any new problems that haven't been discovered in the last 920 rounds and I was eager to begin the formal accuracy testing.
Here's a pic of the bolt carrier group after 920 rounds.
http://www.box.net/shared/static/j92tgxmet1.jpg
Here's a compilation of bolt carrier group pics.
http://www.box.net/shared/static/el013xnc0m.jpg
http://www.box.net/shared/static/t6objhybhh.jpg
Here's a look at the bolt carrier group broken down. Look at the tail on that bolt! Did you ever see one so clean after firing 920 rounds?
http://www.box.net/shared/static/c8bp2jattb.jpg
Most of the fouling on the bolt and carrier was wet fouling and wiped off with a paper towel. The rest came off with a little Break-Free and a nylon brush. There was none of the typical cacked-on, hardened carbon fouling normally encountered when cleaning a direct impingement AR-15.
Here's a look at the Ares gas system after 920 rounds.
http://www.box.net/shared/static/8cjnb96mu5.jpg
http://www.box.net/shared/static/0d4adyxqsg.jpg
Here is the gas system broken down.
http://www.box.net/shared/static/425znm6gs4.jpg
I was surprised as to the absence of cacked-on carbon fouling on the gas piston and in the gas cylinder. Again, this fouling came off easily with some Break-Free and a nylon brush. The gas spigot did have the typical hardened carbon fouling on it, but that would not normally be removed from the gas block for cleaning. Here's a close up of the gas piston after 920 rounds.
http://www.box.net/shared/static/piomgdm0mx.jpg
Here's a pic showing the inside of the gas cylinder after 920 rounds (it was difficult to get a decent picture of the inside of the cylinder.)
http://www.box.net/shared/static/pd16gs91o8.jpg
Here's where a lot of the fouling from the Ares system ends up; deposited on the inside of the handguards.
http://www.box.net/shared/static/lybbh6zjf8.jpg
On a totally unrelated note, here's what 1040 rounds of brass tracking on the case deflector look like.http://www.ar15.com/images/smilies/smiley_abused.gif
http://www.box.net/shared/static/it1jefcug4.jpg
As a recap of the reliability testing of the GSR-35, my unit experienced multiple failures of the bolt to lock back during the first 30 rounds. After the initial 30 rounds, there was no further occurence of this malfunction. Round number 90 failed to go into battery, but this was conclusively determined to have been caused by the ammunition. No other malfunctions occured from that point on.
100 Yard Accuracy Test
Formal accuracy testing of the Ares carbine upper was done following my usual protocol. Three 10-shot groups were fired from a distance of 100 yards off a concrete bench using front and rear bags to support the rifle. A Leupold VARI-X III was used for sighting. The ammunition used was one of my standard handloads using Sierra’s 52 grain MatchKing. Wind conditions were monitored using a “Wind Probe” (and it’s a good thing because it was quite windy during testing.)
I fired three 10-shot groups in a row from the Ares carbine with the extreme spread of the groups measuring:
1.04”
0.99”
1.20”
The average extreme spread for these three groups is 1.08”. This is right on par with what my direct impingement 16” Colt HBARs will do.
http://www.box.net/shared/static/4dhprxa9ar.jpg
The three 10-shot groups from the Ares upper were overlayed on each other using RSI Shooting Lab to form a 30-round composite group. The mean radius for this composite group was 0.32”. The composite mean radius of three 10-shot groups fired from my 16” Colt HBAR was also 0.32”! Shown below is a comparison of the accuracy of the Ares upper with three different 16” Colt barrels.
http://www.box.net/shared/static/fen0jd6clo.jpg
This Is Rumor Control
There have been a lot of rumors floating around the Internet (including some on this web-site) that gas-piston uppers possess some magical ability to propel a bullet “up to 200 fps faster" than a direct impingement upper with the same length barrel. A simple application of science shows this is not the case.
I converted the Ares upper I’ve been using in the testing for this thread back to a direct impingement upper (16” barreled, carbine gas system upper.) Using hand-loaded 69 grain Sierra MatchKings, I fired three 10-shot strings of this ammunition over my Oehler 35-P chronograph positioned 21 feet from the muzzle. I let the barrel cool and then converted the DI upper back to a gas-piston upper using the Ares GSR-35 system. Now, using the exact same barrel with the gas-piston conversion and the exact same lot of hand-loaded ammunition, I fired three more 10-shot strings over the chronograph, for a total of 30 rounds through each different gas system.
Here Are The Facts
http://www.box.net/shared/static/bzxoid3z74.jpg
As you can see from the table above, using 30-round samples for comparison, there is only a 7 fps difference between the direct impingement gas system and the Ares gas-piston system when using the same ammunition and the same 16” barrel.
Temperature- 63 degrees F
Humidity - 34%
Barometric pressure – 30.20
Elevation - 960 feet above sea level
Winds – variable
Skies – partly cloudy, Jupiter aligned with Mars
Government Profile Barrel Testing
For the next phase of testing of the Ares GSR-35 gas piston conversion, I wanted to install the unit on a government profile barrel. I chose one of my Colt 6922 barrels as the test vehicle. (The 6922 is a 16” M4 profile barrel with a 1:9” twist.)
Ares GSR-35 on Colt 6922
http://www.box.net/shared/static/cqyf7e5r4g.jpg
The first thing I noticed when installing the Ares unit on this barrel is that the gas spigot binds on a portion of the barrel near the front sight base. This did not occur with the heavy barrel that I used in the original test. One has to wonder what effect this might have on accuracy.
Arrow indicating area where gas spigot binds with barrel.
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Original HBAR setup without any barrel binding.
http://www.box.net/shared/static/m5gmvp5ncs.jpg
I wanted to use a free float hand-guard with this set-up to avoid the problem of the unit binding on the Ares M4 hand-guards. Since Ares still has yet to release their “upside-down KAC” free-float rail designed for this unit, that was not an available option. The only commercially available free-float hand-guard that I’m aware that will work with the Ares unit without requiring an alteration of the hand-guard is the A.R.M.S. SIR system. I used the #50 slim-line, bi-level military version SIR. The highest portion of the Ares unit clears the underside of the SIR rail by approximately 0.030”.
A.R.M.S. SIR with Ares GSR-35.
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100 Yard Accuracy Comparison
Prior to installing the Ares GSR-35 unit on the 16” M4 barreled upper with the ARMS SIR free-float rail, I tested the accuracy of that upper in its direct impingement configuration from a bench-rest at 100 yards. Using hand-loaded 52 grain Sierra MatchKings, three 10-shot groups were obtained which had extreme spreads of: 1.59”, 1.55” and 1.73” for a 10-shot group average extreme spread of 1.62". While not the most accurate barrel I own, it’s still perfectly suitable for “government work.”
The three 10-shot groups were over-layed on each other using the RSI Shooting Lab software program to obtain a 30-round composite group. The mean radius of the composite group was 0.54”.
After the upper was converted to the GSR-35 piston system, accuracy testing continued in the same manner as above. Three 10-shot groups were obtained using the same load of 52 grain Sierra MatchKings. Those groups had extreme spreads of: 1.77”, 2.54” and 1.85” for an average 10-shot group extreme spread of 2.05". The mean radius of the 30-round composite group created from those three groups was 0.69”. This demonstrates a decrease in accuracy of approximately 0.45 MOA for the ARES system.
http://www.box.net/shared/static/1aelmah032.jpg
On the outside chance that the increase in group size was caused by the Ares configuration simply “not liking” the 52 grain MatckKing load, I fired an additional three 10-shot groups using a hand-load of 55 grain V-MAX bullets charged with a different powder. Those groups had extreme spreads of 2.65”, 2.14” and 1.78” for an average 10-shot group extreme spread of 2.19" with a 30-round composite mean radius of 0.72”. As I mentioned earlier on this page, one has to wonder if the Ares unit binding against the barrel is having a negative effect on accuracy.
http://www.box.net/shared/static/mz2gel5i5j.jpg
Shortly after conducting the accuracy evaluation, the Ares upper began to have failures of the bolt to lock back after the last round in the magazine was fired. Next, I noticed that the cases were being ejected less effectively to the point that they were just barely falling out of the upper receiver. Finally, the upper completely failed to cycle. I hand cycled a few rounds that fired but my Ares upper was now a one-shot AR-15!
After a quick examination of the gas piston system, I found that the gas tube pin had been sheared in half and the gas spigot had shifted slightly in the front sight base causing a misalignment with the gas port. I haven’t used the small spring that is supposed to go in the gas tube channel from the period after my initial testing was completed since it was initially reported that the spring is not needed on the newer units, so this is the most likely cause of the shearing of the gas tube pin. ARES later clarified that “the small spigot spring (is) essentially obsolete in most cases when the kit is installed in a standard carbine. If the sheet metal handguard cap is not used such as with some rail forends, then the spigot spring must be used to eliminate impact loading of the retaining roll-pin.
http://www.box.net/shared/static/fra4krx05n.jpg
Here is a pic of the underside of the ARES M4 handguard showing the the channel worn into the heat sheild from rubbing against the gas cylinder.
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Also interesting to note, is that when I installed ARMS SIR on the upper with the ARES system, there was a definite clearance between the gas cylinder and the underside of the SIR rail. Yet, after firing there were clearly signs on the underside of the SIR rail that the ARES gas cylinder had been making contact with it during the firing cycle.
http://www.box.net/shared/static/xy0gzg280h.jpg
Great post and thanks for taking the time. I am curious as how say an Adams Arms conversion (Sabre, S&W, Stag) would do versus the Ares. I have a hard time giving Ares much love after the well documented Shrike debacle. Also, how a piston system 'designed' as such i.e. Barrett, LWRC, etc. would do against both the conversion kits and DI in testing as you did.
If going to a piston gun, I highly recommend getting one that was designed from the ground up to be piston operated.
The AR simply isn't.
There isn't anything wrong with piston operation, and it does offer advantages over DI, especially if you want to run it with and without a suppressor. Some piston designs/executions are better than others, just like overall designs, and I have seen no data that puts any piston AR over contemporary piston designs.
My thoughts exactly! Every Piston AR is still a modified DI AR. If a Piston you must have......Buy a rifle designed as a piston.
I agree, but not entirely. F2S has a valid point, but I believe the jury is still out on the merits and long term potential of the AR pistons. I think the major drawback at this time is the number of different manufacturers. Nevertheless, a DI if properly maintained will serve you well.
Otherwise, if you want a 5.56 piston, try the SIG 550 series if you can find one.
Dude, I think it is pretty clear you have little or no experience with a piston system....
I'm basing my opinion completely on my experience with them, not just "well I read...." I'm very biased against them now, after using them. They've caused more problems for me than fixes. Maybe it's the particular system I've had the most experience with (adams arms), maybe not. But some of the issues with it are inherent in the piston AR concept. Carrier tilt, bolt cam pin dragging causing a significant increase in wear in the upper, the piston system affecting the timing on full-auto fire causing it to cycle too fast and click on an empty chamber, the bolt carrier being too large in the rear (to accomodate for carrier tilt) to properly fit and cycle in some buffer tubes, systems being problematic on short barrels, only working with 2 rail systems, and bushings/sleeves coming loose in the upper receiver causing cycling to stop, are all things I've run into with piston systems. And noticeably stiffer recoil. What are you basing your opinions on?
And adding more places on the rifle that need cleaning, making it more time consuming for me. But I've read online that they're easier to clean. :rolleyes:
Magic_Salad0892
01-11-11, 10:34
My experience with the LWRCi system says that they're cool, and one that's well made (IE: LWRCi, or LMT) will work well.
But there is absolutely no reason for them to even exist.
justin_247
01-13-11, 16:28
NICE, NICE write-up Molon! Thank you for posting it... very informative and goes to show the weaknesses of the Ares system.
Any chance you're going to do a similar write-up on the Adams Arms system? Lots of companies are using that now and it seems to be the most popular of the conversion kits.
Thanks!
Dirtyboy333
01-13-11, 23:11
Very interesting and thank you for your work.......I'm not familiar with the piston conversions and i want to know if (when firing) the op rod pushes on the carrier key and continues to push it until the rearmost of the cycle and then returns OR does the op rod just violently smack the carrier key at the beginning of the cycle and the momentum cycles the bcg??? Thank you
Robb Jensen
01-14-11, 06:01
I didn't have such good luck with the ARES kit. Mine shit the bed in less than 600 rounds when used on a full auto lower.
https://www.m4carbine.net/showthread.php?t=9308&highlight=ARES
Very interesting and thank you for your work.......I'm not familiar with the piston conversions and i want to know if (when firing) the op rod pushes on the carrier key and continues to push it until the rearmost of the cycle and then returns OR does the op rod just violently smack the carrier key at the beginning of the cycle and the momentum cycles the bcg??? Thank you
Short stroke piston systems operate off inertia, (just smacking the BCG), long stroke systems feature oprods that are somehow attatched to or part of the BCG. Neither is generally better than the other, each are produced by decent and not so decent manufacturers alike. Short stroke systems are a bit more popular than long stroke systems for use on ARs.
Any major pros or cons? Am I better off not messing with it?
The smarter conversion is going piston to gas. Less problems by far with direct gas, Babe.
El Pistolero
01-14-11, 22:21
I actually like both systems, I think they both have their pros and cons and while I believe there is nothing wrong with the DI system, I also have seen first hand how simple some pistons systems are, such as the Osprey Defense one and I myself want a Colt 6520 w/ Osprey Defense piston kit for a KISS carbine. I don't see how the gas piston kit, whether retrofit or factory, can be detrimental to reliability if designed correctly. As for factory pistons, the ones I like best are the offerings by LMT and LWRC.
1st can I ask why your interested in doing the switch? The gun giving you problems etc.? If you just want a piston system I would suggest buying a gun designed around the piston system.
Just to add if you have a good DI gun already why mess with it?
I own a LWRC with zero problems and over 10k rounds. So take everything you read in hear as an opinion, there's some very biased people on this forum.
I didn't have such good luck with the ARES kit. Mine shit the bed in less than 600 rounds when used on a full auto lower.
https://www.m4carbine.net/showthread.php?t=9308&highlight=ARES
They replaced your bent parts correct?
The Bushmaster version of this system has a clamp that holds the piston housing in alignment over the barrel. When I installed mine, a buddy made a solid steel pin to replace the roll pin as a "just incase" measure. We were a couple thousandths off and the pin actually backed out during firing but the clamp held everything in place. Later replaced with a larger solid steel pin.
If you can work on your firearms a retrofit system is easily a doable project.
For all the nay sayers I say THANK YOU ! ! ! I LOVE mine and have two more systems sitting in boxes ready to go. People bought them and never installed them because they had read negative comments on them and sold them off cheap.
I have run my system for well over 3 thousand rounds. In that time I experienced three failures and they were in the first 2000 rounds with NONE SINCE.
In the first 2000 rounds fired, which was a mix of Wolf 75 grain, Privi 75 grain and some PMC bronze, these were the faliures.
1. Double feed from a Beta C that hasn't been graphited since I got it. I will choke that one to the mag.
2. Stuck Case of Wolf 75 grain. This was after firing 500 rounds of the stuff with out scrubbing the chamber. I am going to say that was my fault for not swabbing the chamber sooner when shooting Wolf for practice ammo.
3. Double feed from a brand new GI OKO magazine that had never been run before.
All three failures I think I can safely say were not the fault of the piston system. I like piston systems and I don't feel they are a step down from the Current DI/Piston inside to bolt.
The problems with them have been addressed
Carrier tilt? Seth Harnesses buffer.
Wear in the upper from the cam pin? POF roller cam pin.
If your worried about possible break down in the system, by some spare parts. If your still worried about it keep the DI parts on hand to convert back if the world is gonna end.
All in all the piston in an AR platform is in MY OPINION an improvement.
IPSC_GUY
SIERRA II ALPHA
Wow, that's got to be the most detailed reply to a thread I've ever seen! Thanks again Molon.
ForTehNguyen
01-17-11, 15:13
i dont see any major savings in any category going to piston. Especially heat. With DI you have some of hte heat going back to the BCG and upper receiver. Someone did a test back then that compared the bolt temperature of DI vs piston. There was negligible difference in temperature like ~20 something degF but the barrel and chamber temperatures on the piston where noticeable higher.
The same amount of heat is produced in either gas system, one of them concentrates the heat in the barrel more than the other. Also piston adds weight and additional complexity for debatable gains.
i dont see any major savings in any category going to piston. Especially heat. With DI you have some of hte heat going back to the BCG and upper receiver. Someone did a test back then that compared the bolt temperature of DI vs piston. There was negligible difference in temperature like ~20 something degF but the barrel and chamber temperatures on the piston where noticeable higher.
The same amount of heat is produced in either gas system, one of them concentrates the heat in the barrel more than the other. Also piston adds weight and additional complexity for debatable gains.
Here is a study done using a FLIR Thermal Imager. The temp in the Piston Driven AR chamber was ACTUALLY LOWER than the DI system. So it would seem that piston systems do not concentrate heat in the barrel.
Big thanks to Hootiewho for doing this test.
https://www.m4carbine.net/showthread.php?t=62889
http://i135.photobucket.com/albums/q153/hootiewho6933/Scar/irspreadsheat.jpg
IPSC_GUY
SIERRA II ALPHA
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