AR feed problems

[Viperdoc]

My service rifle and my match rifle in 223 are having feeding problems. They won't lock back on the last round, but most of the time the match rifle will try to double strip two rounds from the magazine, causing a consistent jam. However, sometimes it will short stroke and not strip a round at all. Mostly, it tries to double strip two rounds.

I have an M-16 bolt carrier group (heavier), and an olympic arms air buffer. I called OA and they said the double stripping was likely a mag problem, while others have suggested that perhaps it was cycling too quickly. I did note that with somewhat hotter loads the function was better, suggesting that the buffer was set too high, but it is already turned out all the way.

Could this be a mag problem as well as a buffer problem? I ordered some new mags today. I like the feel of the pneumatic buffer, but need better function.

Any ideas?

 

[fdshuster]

Viperdoc: I had many of the same problems you describe when using H4198 powder in an "as issue" Colt H-Bar. Stopped using H4198, switched to H335 & Varget and have never had the problem(s) since.

 

[Viperdoc]

I tried a bunch of different powders as well, but it seems to be a common problem. I should have mentioned that I added an Olympic arms hydraulic buffer as well, and am seeing the same behavior in both guns. However, with some hot loads of varget, the gun will function. I ordered some new magazines to try, but all of the ones I have don't seem to make the difference.

I'm wondering whether the hydraulic buffer is part of the culprit, or that it's not getting enough pressure through the gas system.

I did notice that on both of my rifles there is some sooting around the gas blocks- is this normal or perhaps this is a sign of a leaky gas system. I was thinking of trying an adjustable gas block.

Any thoughts about the logic of this approach?

 

[Ledge]

I'd replace the hydraulic buffer with a conventional spring and buffer, and shoot some m193 ball through it out of a magazine that functions well in another rifle.

 

[Kenny474]

While the buffer isn't a bad idea, if the rifle is chambered in .223 running 5.56 military ammo through it is going to cause pressure problems. If it is .223 and doesn't have a wylde chamber, or other chamber compatible with 5.56 ammo, try some stout factory loads and see if they operate it properly.

 

[effendude]

Take out the buffer system and get new mags is my first suggestion. If your rifle feeds rounds properly except the last two, it sounds like weak mag springs and worn feed lips.
There are so many "mil-spec" mags being sold out there that won't even function as paperweights. Buy some mags from Brownells or Mag-pul.

Do you have a Bob-sled, the one piece single round loading device? If so, does the bolt stay back after you shoot a single round with the Bob-sled? Does your bolt stay back when a single round is loaded into a standard mag? If so, you have enough gas/bolt pressure to run the bolt.

 

[Viperdoc]

Was running a CWS carrier weight in addition to the air buffer. Together the gun would double feed and jam each round. (somewhat less than max H335 with either 53SMK or 69SMK). Then loaded up some Hornady Vmax 55 and Berger varmint 63's, but same problem with double feeds.

Took out the weight, and also then ran some pretty hot Varget loads. With these loads the gun would cycle, but the brass was showing some ejector marks, but no primer issues. Gun would cycle and even lock back with these loads. Seems like it could be a lack of gas problem, (standard Krieger 0.096 hole), but the buffer is set for the lowest resistance.

So, I ordered some new Pmags from Magpul to try, and may remove the buffer and go back to the spring. What about using an adjustable gas block- open for lighter loads, and close for heavier?

Beginning to think it is a combination of cheapo mags and the hydraulic air buffer in combination, but other ideas and suggestions welcome.

 

[Kenny474]

I think you need to work on one problem at a time. There are too many variables when you are looking at the buffer, a mag issue, and not knowing if the loads will operate the rifle. Start off with trying some factory ammo. If that wont' operate the rifle, than you either have a gas leak or an issue with the buffer. Narrows it down quite a bit. Then deal with the feeding issue, as it could clear up once you get the rifle to properly cycle. One step at a time.

 

[Viperdoc]

Just went to the range- think I learned a little more. Tried both my service rifle, and a carbine length bull barrel but full length stock (with the same lower that failed to feed before, another story). Had three different loads- a hot varget load with 69SMK's, and a moderate load with the same bullets but H335, and then some H335 and Sierra 53gr MK's. I brought only two magazines.

Both rifles were generally better (86 degrees out), but the Varget (hottest) loads functioned the best, as before. The two mags (one from brownells, and one steel) made no difference. Still, there were jams. In the match rifle lower (with the carbine bull barrel) there were jams, where most were short strokes- the bolt never locked back except with the hot loads, and it short stroked most frequently with the 53SMK's.

The service rifle FTF mostly by double feeding, regardless of mag. Again, better function with the hotter loads.

Both were shot off a bench, with a light hold, When shooting offhand, or with the rifle completely off of the rest, the cycling was clearly more reliable.

I am going to remove the hydraulic buffers from both, and then go back to the range with the same combo of guns, mags, and ammo- is this still making sense or not?

 

[jonbearman]

How clean do you keep the gas system,sometimes you have to clean the gas tube out with bore solvent .The other problem alot of people overlook is running the boltand carrier group way too dry.You need to lube it up liberally with break free or any high quality lube on the market.The next thing to do is take the carrier group completely apart and scrape the carbon off the carrier and the back of the bolt.I shoot mild loads through all of my 6 ar style rifles and have zero problems.The next thing I would do is try a standard buffer and change the spring to the tubb style spring. These guns function pretty reliable with great care to maintenance.To heck with the super hot loads as this will only wear out barrels and parts. Get a copy of the GI How to maintain the M-16,it is elementary my dear watson,lol lol! Good luck,pm me if you have any questions.

 

[jonbearman]

One other note,mags are mags,the most overlooked problem with feeding issue's with any type box magazine is seating the bullet out as far as you can gn the bench the mag works fine ,however in recoil slamming the crtridge's around it can set the bullet farther forward if the neck tension is overlooked,there is a reason uncle sam use's a stout crimp to stop that from happening or stoving it in when the feed angle is off slightly.I suggest you freebore the bullet a little and use a mild taper crimp.All your case's must be the same length to get the crimp to be standard on each round.

 

[Viperdoc]

The FTf is happening in both my sr as well as my match rifle. The mags are from brownells, but I just got some pmags today. Cleaned the bcg thoroughly. All rounds are new lapua fl resized, neck tension 0.003, trimmed and chamfered. Took out the hydraulic buffers and put in old springs today but need to try. Seems like the hydraulic buffers are the common factor.

Am running a heavier m16 bcg. No binding of key on gas tube. Thanks for all of the great ideas!

 

[kentuckytroutbum]

How clean do you keep the gas system,sometimes you have to clean the gas tube out with bore solvent .The other problem alot of people overlook is running the boltand carrier group way too dry.You need to lube it up liberally with break free or any high quality lube on the market.The next thing to do is take the carrier group completely apart and scrape the carbon off the carrier and the back of the bolt.I shoot mild loads through all of my 6 ar style rifles and have zero problems.The next thing I would do is try a standard buffer and change the spring to the tubb style spring. These guns function pretty reliable with great care to maintenance.To heck with the super hot loads as this will only wear out barrels and parts. Get a copy of the GI How to maintain the M-16,it is elementary my dear watson,lol lol! Good luck,pm me if you have any questions.

To add to what johbearman said, clean the bolt/carrier group very well. After a match, I disassemble the group, and soak it overnight in mineral spirits. You'd be amazed at the amount of carbon that get dissolved.

Also, after cleaning, check to make sure that the gaps in the gas rings are off set from each other. If you don't, gas will blow by the rings and it will short cycle.

 

[Doc Bob]

Hydraulic buffers were developed for full auto and suppressed weapons in response to the increased pressures from both. While they smooth the recoil on semi auto, this can cause short stroking.

Place new mag in rifle with one round loaded and see if the bolt locks back after firing. This will show if the bolt cycles fully. If you continue to have problems replace with original buffer and action spring and repeat.

The hotter powders are adding gas pressure and that is why a hot load will cure short stroking, but is defeating the purpose of a tuned system as related in the attached linkhttp://www.ar15.com/forums/topic.html?b=3&f=66&t=266108

There are also different weight buffers designated as H1 (Rifle) H2 (Carbine) H3 (SBR or Pistol.) Each one increasing the weight in relation to the increased gas pressure from each from low to high respectively. These are generally the choices for reliable AR function.

 

[15Tango]

I'm risking pointing out the obvious here, but what stock are you running? I only ask because Olympic Arms's site states: "Note: The AC4 will NOT function in AR-15 rifles or carbines with collapsible stocks. The AC4 will only function in A2 buttstocks and buttstocks with full length extension tubes."

If the tube's not long enough it doesn't allow the action to go back far enough to engage the bolt catch. I had the same issue when I installed a Wolf extra power spring into my service rifle, too many coils and the action wouldn't go back far enough.

I'm also not much of a believer in M16 carriers, especially with high spring rates, it can be too much for the 5.56 to kick back. High spring rates work well with the lighter carrier it seems. The M16 carrier's designed as it is because that extra portion of material is what trips the auto sear - as far as I know it wasn't meant to tune the firing or buffer rate.

I second what Ledge said, put a standard buffer and spring in and try that, at least it'll eliminate your air buffer as being the problem.

Good luck,

Wayne

 

[Viperdoc]

Problem solved (at least with the service rifle). Removed the hydraulic buffer from Oly, and reinstalled stock buffer and spring. Also tried pmags. Result: absolutely no feeding problems- shot over 100 rounds two different bullets, two different powders, and no feeding or locking problems at all. Using a heavier M-16 BCG along with the carrier weight system.

Still, no problems with any of the ammo, where it used to jam at least every other round. My previous mags were good ones purchased from Brownells, but I think the Magpul followers are better.

However, the problem clearly was with the Olympic arms hydraulic buffer. I think in combination with the heavier BCG and the CWS, there simply wasn't enough oomph to overcome the air piston, even with hot loads. In the 100 rounds we shot today of varying loads, there were absolutely no FTF's, which is the first time in a very long time.

Even with a standard AR BCG and no carrier weights, I still do not think any reasonable loads would work with the hydraulic piston. There were no obvious differences in the feel of the recoil pulse as well- it simply did not work in either of my two AR's.