View Full Version : Ok let's play Diagnose the Franken upper
This is a long winded post as I wanted to make sure all important info was included. There is a summary at the end of the long winded narative you may want to read first.
I aquired a 14.5 inch upper in a trade. There are no marking on the barrel at all. It is cut in the M4 profile. The are no M4 feed cuts. It has the DPMS copy a Phantom flash hider. The reciever has no marks other that the splintered A forge mark. Seems to be well assembled. The BCG is DPMS. Gas key has an excellent staking job done to it. There are no issues visible with the gas system but have'nt removed the FSB. When I recieved the upper it looked to have little use. Now here begins my story.
I put the upper on my bushy lower with no name M4 extension. The lower also had the geissle DMR installed. I had several FTE and shortstroke like malfunctions. I also had a few double fires. So I proceded to start "fixing things". I tried to adjust the triger assuming this was causing my doubles and found the second stage adjustment screw stripped by the "professional" I had instal it. I removed the trigger and replaced the stock trigger. I stripped the bolt and found a worn or weak extractor spring with blue insert. So I replaced it with the BCM bolt upgrade kit. I then read up on short stroke and over funtion and decided the cheap no name buffer and spring had to go. So I purched a CS spring from brownells and an H2 buffer. While waiting for my buffer parts I installed the A2 stock and buffer. I ran 200 rounds of a mix of wolf, reloads and M193. I had one failure to eject on the M193. I put the rifle up dirty and walked away from it for a little while in frustration.
This saturday I took the carbine to the range after the local 3 gun match as there were tools and input to be found there. We test fired the rifle and on the first round the case got stuck inthe chamber. This was the first time this had happened. After banging the case outwith a GI rod I inspected it. It was abvious the brass had failed to seat properly an gas had blown by and left streaks on the outside of the case. The extractor ripped a chunk off the rim too. The rifle was dirty but... not that darn dirty. After the same thing happened on the next round we cleaned the chamber. Now we were back to running. However we still had some occasional failures to eject. Note since I replaced the extracor spring with the BCM kit my brass has been flying to 1 to 2 o'clock and there are visible signs of chewing at the front of my ejection port.
It was then suggested that I had too much extractor tension so I removed the O-ring and the rifle ran the next 40 rounds but still trying to eject brass through the front edge of my ejection port. When I got home I ran 30 rounds of M193 with my Bushmaster BCG and it ran well but with the same forward ejection.
Summary:
Patient discription: 14.5 mystery upper. No manufacturers marks just a splintered A forge mark. Barrel 1x9 chrome lined. BCG by DPMS. Round count est 1000. Geissle trigger improperly installed.
Symptoms past: Bolt bounce, freaquent fail to eject, occational double fire, sticking chamber when not really that dirty.
Corrective actions taken: Replaced no name CAR buffer and spring with H2 buffer and CS spring. Replaced extractor spring and insert with BCM bolt upgrade kit. Seriously cleaned the hell out of the chamber. Returned trigger to giessle for rework and installed stock trigger.
Symptoms current: Still occational fail to eject last 50 rounds have been fine will call it cured after 200. Ejection at one to two o'clock with visisible chewing at front of ejection port.
Any and all considered input invited please help the noob get his carbine working without it chewing up the ejection port or failing to eject. 200 round tests at $.40 per round cost $80 and I could buy a new upper with the cost of a few of these test runs.
Is your chamber .223 or 5.56? Sounds like you are having issues with it firing the M193. Try some quality .223 and see if it runs right. If it works fine with that I would get it reamed with Ned's tool to proper 5.56 specs and it should fire that M193 without problems.
Does this ned's tool work ok with a chrome lined chamber? What is the best way to determine if it is indeed a .223 chamber? This had crossed my mind but I discounted it as I had not heard of .223 barrels being chrome lined very often.
edit* found the neds tool website neat stuff! After reading the info I found there I would certainly like to give it a try if I do have an underspec chamber. I just need to find out how to verify this is the issue and a way to borrow or rent the tool. This is a case of a tool I should only need once so investing $250 makes no sence to me.
Does this ned's tool work ok with a chrome lined chamber? What is the best way to determine if it is indeed a .223 chamber? This had crossed my mind but I discounted it as I had not heard of .223 barrels being chrome lined very often.
edit* found the neds tool website neat stuff! After reading the info I found there I would certainly like to give it a try if I do have an underspec chamber. I just need to find out how to verify this is the issue and a way to borrow or rent the tool. This is a case of a tool I should only need once so investing $250 makes no sence to me.
I think Grant at G&R Tactical has one and can do it but I would ask him to be sure. Maybe ADCO once again I'm not sure. The only way I know for sure as to check what your chamber is, is to do a chamber cast and measure from there. But the odds are since whoever made your rifle barrel didn't even bother to mark it probably didn't bother to use a true 5.56 chamber either. Also from what I've heard Ned's tool will handle chrome lining just fine. I've been toying with the idea of purchasing one of his tools and using it on my rifles and borrowing it out to members here but am a little short of funds myself at the moment. My Stag is marked as a 5.56 but even still I will eventually have the reamer run through it just in case as I've heard very few manufacturers even ones labeled 5.56 are to spec save Colt, LMT, and other top tier ones. I would try and get ahold of Grant if I were you and see what he has to say about the situation as he is very knowledgeable about these types of things.
Zydeco,
I have been using Ned's chamber reamer here in Iraq for approx. 2 months. This is due to the fact that the Bushmaster carbines we have though marked 5.56, were in fact not truly 5.56. Yes, they are chrome lined chambers and bores. The chamber reamer seems to have helped reduce the issues we were having with the Prvi Partizan and Bulgarian Arsenal manufactured SS109 ammo. Typically we saw failures to extract and blown primers.
The money it costs may not be worth it to you, but in our situation it was a necessity. This really goes to the heart of the point of knowing what you are buying ahead of time and refusing to buy stuff from companies that have a track record of not producing stuff that is "MILSPEC" or that is to say doesn't even meet the TDP. We also know that some companies that do not meet the TDP per se do produce a better mousetrap (Noveske being a prime example).
In the case of your upper I have no idea what you paid for it, or who makes it, but it is obviously not working like it should. It's also one reason that I am very hesitant to buy anything AR related unless I can verify the who, why, what, where and when.
Does this ned's tool work ok with a chrome lined chamber? What is the best way to determine if it is indeed a .223 chamber? This had crossed my mind but I discounted it as I had not heard of .223 barrels being chrome lined very often.
edit* found the neds tool website neat stuff! After reading the info I found there I would certainly like to give it a try if I do have an underspec chamber. I just need to find out how to verify this is the issue and a way to borrow or rent the tool. This is a case of a tool I should only need once so investing $250 makes no sence to me.
Did you by any chance try to check it the extractor on both BCGs have signs of wear? Did you transfer your BCM extractor spring to your Bushy BCG?
How do you know it's a 1/9 if it doesnt have any markings on it??
Stab in the dark, what about an improper port job on the gas tube? Or a gas tube misalignment?
ryan,
Unfortunately, there are so many variables here. Gas rings, barrel port size (as you mentioned) gas tube, no idea who put it together, etc...etc...Then of course we don't know exactly what type of ammo he is using either. This is a problem when you buy something used especially with an AR type upper and parts.
Gas tube port size chart and gas system length to barrel length query...
Does the 14.5" barrel require a different port size than a 16" with a standard length carbine gas system? I vaguely remember reading somewhere on the forum about differing port diameters and how that associates with the gas system length as well as barrel length. I also understand there is some variation between manufacturers on this.
Definitely alot of variables in play here, but I was thinking if it was a custom built upper--the guy might have bought a standard carbine gas tube with an incorrect port diameter for the 14.5" barrel. That's assuming there isn't something else fundamentally flawed with the upper.
Found the link
http://m4carbine.net/showthread.php?t=1481
Ammo has been a mix of Privi, win, fed M193 with some reloads and wolf thrown in aswell. This upper is intended to be a three gun match upper and not something I would bet my life on. That being said I still want it to work. I have not pulled the FSB yet to measure the port size. I am hesitant to take this step on my own but will as last resort. Gas rings are new. Extractor is in good order. I have 3 bolts and 2 carriers. I am dumping the DPMS BCG. I have upgraded my Bushy BCG and have a colt spare bolt that I have also upgraded. At this point I believe I have these options.
Option:
1. pull FSB measure gasport and remedy if out of spec with adjustable gas block or tube.
2. Find somebody willing to lend or rent me neds reamer.
3. Ad more weight to the buffer.
Any other options out there?
With the problems you are having, ream the chamber. That would be the first thing I would do. What is your location, as I have one of Ned's reamers and if you are close, I could try and help you out.
I am in South MS. Its a bit far for a comute to SC I am afraid. Carolinas still give me a chill anyway since I had basic training there and a freak moster of a drill Sgt still haunts my dreams. :eek:
If anyone would be willing to send me one. We could work out a collateral type of trade to ensure I wont run off with it and start a chamber reaming buisness.
BravoCompanyUSA
02-23-09, 22:44
Lots a good info here, so my post is an echo....
First, insure you have a 5.56 chamber.
Quickest way is Ned's chamber reamer. We have one in the shop. It's on the large end of the NATO spec, but that's ok. You will be good to go.
After #1 is confirmed/complete, you may have a short stroke issue.
Here is some info:
Short stroking (Failure to cycle)
Short stroking on an AR rifle is when the bolt carrier group does not cycle far enough to the rear to be able to strip a round from the magazine and chamber the next round. After firing a round, you will notice that the bolt is closed on an empty chamber, thereby forcing you to manually cycle the rifle to feed the next round. This occurs when there is an issue with the gas system.
To see if you have a short stroking problem and not a “Failure to Feed” problem, please perform this test first (assuming your bolt catch and magazine is functioning properly). Insert one round into a magazine that you know to be performing well. Insert the magazine into the magazine well, pull the charging handle to the rear, then release the charging to load the round into the chamber. Safely discharge that round. After the round has been fired the bolt should automatically be locked to the rear by the bolt catch and the empty magazine. If the bolt is closed on the empty chamber, then it did not travel far enough to the rear to be held by the bolt catch, and your rifle has short stroked.
Short stroking is a symptom of a problem with the gas system in the rifle. There are 7 parts of the AR gas system. In the upper receiver group, you have the barrel (gas port), front sight base, and gas tube. In the bolt carrier group you have the gas key, the carrier, the bolt, and the gas rings.
Assuming the rifle was running correctly previously (in the exact configuration it is currently) The following is a basic trouble-shooting checklist.
1) Ammo issue ? Commercial ammo does not run as hot as Milspec ammo, and some lots of commercial ammo may not be strong enough to cycle the weapon. Try a completely different type of ammo. If the weapon works correctly then you may have some bad ammo. This is becoming a more common problem with some of the low cost imported ammo, especially with milspec sized gas ports.
2) Lube and clean the rifle. Pull out your GI manual and properly clean the weapon. As a note, a little bit of dirt and carbon should not stop the proper cycling of your rifle.
3) Check the carrier (gas) key. If the carrier key is loose, the gas system will not hold enough pressure to fully cycle the weapon. Try a different carrier that you know to be working in another properly functioning weapon. If the weapon runs well with the other carrier, you may have an issue with your carrier key. The carrier key bolts should not be loose. It should be staked from the factory. Check to make sure the bolts securing the key did not rotate past the staking. The bolts should be torqued to 35-40 in/lbs.
4) Check the gas rings. (or just go ahead and change them – they are very inexpensive) Mythbuster: The gaps in the gas rings do not need to be staggered. I know we were all taught otherwise in recruit training, and yes I know it says they must be staggered in the GI manual. But this is a myth. As a note; it will not hurt the system to stagger the gaps in the rings, but if this single change makes the difference – you need new gas rings ASAP. Inspect the rings, make sure there are 3 of them, and that they are installed properly. Disassemble the carrier group, insert the bolt into the carrier, and hold the carrier vertically in the air. The bolt should not fall out of the carrier.
5) Change the gas tube.
Full verions here:
https://www.m4carbine.net/showthread.php?t=139
Tnx for the input Bravo. I have performed the short stroke test as this was my first thought. However the bolt has never failed to lockback after the last round. My practice drill involves Loading all my mags to 6 rounds. I fire two "2 and 1's" then do a mag change. The upper has already locked back %100 for 300 mag changes or so.
One question just crossed my mind though. Were you saying that short stroke could occur because of the chamber changing spec? This would not even slow me down from doing it as I want to fix the problem rather than compensate for it. I do still have that CAR buffer aswell as the abilty to make it an H buffer.
hey I don't supposed you provide shop services do you?
BravoCompanyUSA
02-25-09, 07:58
Tnx for the input Bravo. I have performed the short stroke test as this was my first thought. However the bolt has never failed to lockback after the last round. My practice drill involves Loading all my mags to 6 rounds. I fire two "2 and 1's" then do a mag change. The upper has already locked back %100 for 300 mag changes or so.
One question just crossed my mind though. Were you saying that short stroke could occur because of the chamber changing spec? This would not even slow me down from doing it as I want to fix the problem rather than compensate for it. I do still have that CAR buffer aswell as the abilty to make it an H buffer.
In your first post you said it was short stroking. How did you determine that ?
If the bolt is locking back on the empty mag, then it is doing a full stoke.
Also, if you find the carbine is short stroking, a heavier buffer will make it worse.
If you have a good NATO chamber, and you are getting FTEx problems, a heavier buffer (along with new extractors, and stronger Extractor springs) will help.
BravoCompanyUSA
02-25-09, 07:59
hey I don't supposed you provide shop services do you?
Sorry, but we do not.
Thanks,
Hey again Bravo if I stated that it was short stoking I did'nt mean to. I have been known to write in a very unclear manner though so I can understand why you may have read it like that. Rightnow the only issue I have is a rare but occational failure to EJECT. Visible battering of the front edge of my ejection port.
My original problem I believe was what I called overstroke. Guess bolt bounce would have been a better term. I had a CAR buffer that was lighter than a car should be and a really cheap spring. Also the Giessel hammer was much lighter than a standard one. All these factors I combined to offer less resistance to the rear movement of the bolt. The info on this forum lead me to those conclusions and helped me go from 1 malfuntion in every 3 rounds to one in 200.
I am interested in sending this upper to somebody that has the tools and knowlege to really look it over and see if everything is in spec. The chewing at the front of the ejection port has me baffled.
Does your ejector spring feel strong when you push down on it or does it feel spongy? I think I would change it out and see what happens.
Corrective actions taken: Replaced no name CAR buffer and spring with H2 buffer and CS spring. Replaced extractor spring and insert with BCM bolt upgrade kit. Seriously cleaned the hell out of the chamber. Returned trigger to giessle for rework and installed stock trigger.
This is a band aid fix and does not get to the bottom of the real problem.
Does your ejector spring feel strong when you push down on it or does it feel spongy? I think I would change it out and see what happens.
Agreed but, I'd replace the whole ejector - plunger and spring.
Try putting an empty case on it under the extractor lip and see if you can push it down flush. If its tough to do (or since you said you had a Colt bolt - feel the difference).
Since your gun is trying to eject too early its either the ejector tension being to high, or your bolt speed is way low.
On the bushy bolt it is seems to catch a little on the otherside of the bolt face as in not smooth. On the colt it is smooth with no catching. The colt tension on the plunger may be a little higher than the bushy. The colt bolt was used when I got it with worn out gas rings. I have never messed with the ejector spring as they seem to feel the way they are supposed to. I cant push either all the way down with my thumbnail. With the tip of a bullet I can push both below the bolt face. I also dug out the DPMS bolt and it feels about the same as the other 2 as far as ejector tension. Both BM and colt have been upgraded to HD ext springs and orings.
What could cause the bolt to be moving too slow but not cause shortstroke?
On the bushy bolt it is seems to catch a little on the otherside of the bolt face as in not smooth. On the colt it is smooth with no catching. The colt tension on the plunger may be a little higher than the bushy. The colt bolt was used when I got it with worn out gas rings. I have never messed with the ejector spring as they seem to feel the way they are supposed to. I cant push either all the way down with my thumbnail. With the tip of a bullet I can push both below the bolt face. I also dug out the DPMS bolt and it feels about the same as the other 2 as far as ejector tension. Both BM and colt have been upgraded to HD ext springs and orings.
What could cause the bolt to be moving too slow but not cause shortstroke?
If all the parts seem normal you really need to move onto the barrel. That is probably where your problem is.
Heavy duty springs, tension inserts, H buffers, and M4 ramps are band aid fixes. You should not need any of these for your gun to run properly.
Failure2Stop
02-26-09, 04:57
I saw this thread when you first posted and meant to add my thoughts but was unavailable.
I think that you are looking at 2 potential issues-
Tight chamber
Ejector Issues
This very well could be an and/or issue.
What I would do-
Clean and lubricate the ejector by placing a few drips of your favorite lubricant on the ejector allowing a little pool of lube to stand around the ejector. Repeatedly press the ejector fully in and out. Watch for brass flakes/carbon to float out of the ejector channel. Once you have done this for a few minutes hook a spend case under the extractor, pressing it fully flat on the bolt face. Release the case- it should be forcefully and immediately flung from the bolt. If there is any hesitation or if the case just dribbles off the bolt face you either need to continue cleaning/lubricating the ejector or replace the ejector spring or entire bolt assembly. Try it with and without the o-ring. If it works without the o-ring but not with the o-ring you may have excessive extractor tension, which is a problem with worn/dirty ejector springs/ejectors.
Go to the range with your Colt bolt and known good ammo. Test-fire the gun with your newly cleaned and lubed bolt. If the problem persists, switch bolts with the Colt and shoot again.
This will at least eliminate the bolt/ejector as your problem part.
I had already done the fling the brass thing and all looked well. However I did spray break cleaner into and around the ejector plunger and worked it then sparyed more etc... for a few mins. A fellow on another board mentioned the term "short release". I then remebered the chewing of the front of the ejection port began after I installed the BCM extractor upgrade. I removed the oring "again" as I had done this once before but maybe the the ecector had too much gunk? Well I just ran 300 rounds. No function issues at all. I used fed XM193 WinM193 some privi and a box of 75grn wolf. The only problem I had was gross inaccuracy. I rember the first time I fired this upper I had a hell of a time getting the buis lined in. I ended up setting the eotech then just adjusting the BUIS to the eothech. This time I was using the carry handle. I guess I was just shooting like crap as I had an extremely physical day. Incedently the wolf hit the best "still not good" groups so I guess I am gtg on 75 grain wolf. Now I am ready to play at the next match though.
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