I've been contemplating my next build and decided on a 14.5" DD or BCM LW Middy with a permed Battlecomp.
Has anyone documented any accuracy loss in the LW barrels, CHF or CMV during long strings of fire?
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I've been contemplating my next build and decided on a 14.5" DD or BCM LW Middy with a permed Battlecomp.
Has anyone documented any accuracy loss in the LW barrels, CHF or CMV during long strings of fire?
Personally I cannot tell any difference
I've asked this question before. From what I understand, barrel heats up and the point of impact changes, but not a whole lot. I have no first hand experience, just what I've been told. I dont know the accuracy differnce at a distance over 100 yards but I hope this helps.
I think in concept that is whats suppose to happen. But I cannot tell the difference. Maybe if you were doing mag dumps in full auto, then trying to make a precise shot? I don't know, I wouldn't be concerned with it though.
Point of impact change as opposed to what?
As opposed to group size increasing.
The disadvantage of a pencil barrel is that once you get one, you will feel all your other AR15s are too heavy and want to change them over too. And now I feel that an M1A is a complete pig.
It would seem to me that high volume firing and high level of accuracy are somewhat mutually exclusive. I'm not going to deploy the same gun for the two different roles.
I would never use a pencil barrel for anything.
It would be interesting to have someone run a controlled test. Shoot a 5 round group for accuracy slow fire, fire a 30 round mag and then shoot another 5 round group, with a couple different barrel profiles. Then compare the before and after on each one.
Do they make a ransom rest for AR's?
I've 2 true pencils, 1 govt. profile, and a SS mid weight that I shoot regularly and other than precision type shooting I can't tell much of a difference. I've run the 2 pencils in the last 2 classes I took. One was maxed at 50 tards, the other 200 yards. I never felt I was at a disadvantage accuracy wise, if anything the lack of a pound or so of weight over several days made me feel kind of spry:laugh:.
I also averaged about 400 rounds a day so what would someones definition of high volume shooting be?
Lots of guys say they don't see much of a difference, but my inner scientist would love to see what the real difference is.
Then I hope you are using full heavy barrels because Government Profile is a joke as far as heat dissapation. It is worse than a lightweight because you are putting weight on the muzzle end that will encourage the barrel to sag more under gravity as the barrel heats.
It is heavy on the wrong end to work. The chamber end is where the bulk of the heating occurs and where you want to sink away most of the heat.
Good to know :sarcastic:
Back on topic, I have no problem with lightweight barrels. Any barrel will shoot larger groups as it gets hot. A lightweight barrel simply has less surface area and less heat sink volume, so it gets hot faster.
Don't shoot your barrel red hot, and it'll be fine.
400 rounds a day might or might not be considered a lot. I think what's more important is how many rounds per minute you were going through, and for how long. One mag dump will get a gun hot, but not HOT hot. Dump 4 or 5 magazines back to back, and you're really pushing it.
I'd still like to see a quantifiable comparison done that would us tell us exactly what that translates to at 100 yards, and the difference between the barrel profiles.
Kartoffel, Different types of classes are geared towards different goals. My point was that for that class 50 yards was as far as we shot. FWIW the class in question was one of Pat Rogers very highly esteemed Carbine Operator Class. When you combined the accuracy with the speed requirements and target size it is one of the more difficult classes I've taken.
I understand and agree with your thoughts on 4-5 mag dumps. I really don't understand why anyone other than a service member shooting Uncle Sugars peashooters would ever need or want to do this? What's the point? As a civilian or LEO it's not relevant to anything.
I have lugged 17+ lb. precision rifles around for many years before building my current 11+lb. rifle. This is a Remington bolt gun but is still relevant to this conversation if we're talking extreme accuracy. My current rifle has a 20" Rock 5R Remington Varmint contour and will shoot with my old 26" much heavier profile Walther Lothar out to 800. I believe the comparison is similar to a Govt. profile vs. pencil. If you carry one all day or attend classes that have long hours a 6.0-6.5lb carbine will make a difference over a 7.0-7.5lb carbine.
Didn't Molon do a test of a Colt LW either here or at TOS?
I searched for a thread like that from Molon, but all I found before posting this thread was where he tested a Colt LW with an unmentioned brand of ammo with an ES of 1.32".
That's great if it's bulk M193 or M885, not so great if those were a tailored handload. Also doesn't really answer the question if the barrel was cool to begin the test.
I have asked on TOS for someone to try this and couldn't get a single person to take me up on the test I asked to be performed.
I was hoping for a 10 shot group at 50yrds with a RDS then shoot 100rnds rapidly to get the barrel HOT and then a second 10 shot group at 50yrd and simply post the results.
I have been looking at the smartgunner DD deal and have been debating heavily between the gov profile and lightweight 16" middy. I am not looking to build a match grade bench gun in my mind a lightweight barreled rifle is going to be for HD/SD/SHTF.
Here is a great article on the subject:
http://www.highbeam.com/doc/1G1-71323936.html
In it's original configuration right up to the A2s, the barrel profiles were light weights. They're rifles, not belt feds.
After gaging A-1's, A-2's, A-4's and M-4's that have been used in combat for extensive periods of time, I found the A-1's needed the barrels replaced more often than those with heavier barrels, while I've only worked on government models, I am sure match barrels and true heavy barrels would not lose their accuracy as much as the others.
Actually it was done to prevent bending when the GIs used it as a crowbar for breaking straps off C ration cases during the VN war.
Another contributing factor was that a large part of the development of the A2 rifle was done by an ex sniper and match shooter. He was a Marine (Maj. Bruce Wincentsen) and wanted a target rifle with a heavier barrel and more adjustable sights. He also disliked the short stock and made it longer. They forgot that the M203 had to fit, so later turned down the section between the front sight castle and the upper to be like the A1. That's why it is thin under the handguard and thick out in front.
so how more difficult would it be to hit a 2ft by 2ft target at 250 or 300 meters with a hot pencil barrel than with an m4 profile barrel? I'm thinking probably not a whole lot harder... As far as I know this could be considered practical accuracy.
I have found this phenomenon when shooting my service rifles for extended periods. The group tends to wander from zero upon initial heating. The shots maintain a tight grouping...the group just moves from previous POI. As the barrel gets hot the group then opens up some. These are strictly observations from several USGI semi-auto rifles and decades of popping 'em off the dirt.
A barrels resistance to heating induced drift is proportional to overall weight. Much of the mass is placed closer to the chamber where highest temperatures are generated. You see this in heavy match barrels.
Many match barrels are smaller in diameter than conventional barrels. Several of my high end service rifles...M1s and 03a3s have a MW less than zero. This may be minute, only a thousandth of an inch, but they are extremly accurate. A .308 Win barrel when new is actually only .300 of an inch in diameter. As the barrel reaches the end of its usable life this diameter is .304 - 305 of an inch. The barrel now has a MW of 3.0 or more. It's garbage. I only say this b/c these smaller diameter barrels tend to have a reduction in heating drift.
I wonder if projectile bearing surface interaction comes into play when the barrel is hot. Not during heating, as at some point a mechanical stress will be relieved and accuracy will somewhat stabilize as to zero. A tight group....just a different place. Group opens up when hot, but perhaps the zero doesn't drift further.
Eye candy...
http://i219.photobucket.com/albums/c...e/IMAG0071.jpg
Thats a very informative post, thanks
Alright I bit the bullet and ordered a 16" lightweight Daniel Defense upper from smartgunner. Just waiting for it to show up and I will perform the test that I requested myself watch for results I will make sure to post here.
Found the same article, but without having to do the "Free Trial":
http://findarticles.com/p/articles/m...7/ai_71323936/
I am still waiting for delivery of my order. I was able to find exactly what we are all looking for though google search pencil barrel flex and look for a thread from TOS results and test are on page 2. I will still post my results just waiting on my upper.
Not really an apples to apples comparison. A2s, A4s and many M4s have 3 round burst......
I've used, owned and still own some ARs with very lightweight barrels. .565" barrel on one rifle (Project Featherweight) and .640-645" or so (my micrometer sucks) on my KAC SR15E3.
I've never noticed the accuracy drop off when the gun heats up. I've always found them to shoot with the error of the optic meaning 1MOA for an EOTech, 2 or 4 MOA for an Aimpoint. I think accuracy is more based on the quality of the barrel than anything else.
I would like to think that I'm a little more accurate than your average rifles shooter but what do I know?
I have 3 CL pencil barrels and 2 CL non-pencil barrels. One of these days I will do an accuracy test and report it here (but please do not expect the quality of a Molon report).
Until then, I can only suggest that each of you place an order with G&R Tactical for both barrels and build guns from each. I can just about guarantee that you will soon prefer to shoot the lighweight barrel gun for any carbine course (at least after the first morning) and for any activity in which you end up carrying your gun or using your gun continuously for several hours at a time.
For the purpose of this assertion, I am considering rifle use scenarios in which an entry rifle would be more suitable than a sniper-type rig.
Accuracy Evaluation of a Colt 16" Light-weight Barrel, ak47.net/forums/