Home Forums Hunting & Shooting AR and Tactical Rifles Head scratching problem

Most of you have seen the new upper I'm playing with on another thread. However, there seems to be a problem. I think I have figured out why but I have not figured out the solution. Suggestions are welcome.

Problem: With each of 2 different types of accurate ammo, the upper shoots two different groups in the .3's but they are 1 inch apart. The bullets are 55g BT and 60g V-Max.

Additional facts: The start of the chamber has A4 cuts to aid in feeding and the cuts have been deburred. I have not yet tried a different mag.

Maybe why: Seems to depend on which side of the magazine the round is fed from! One group is from rounds from the right side and 1 group is from the left side of the mag.

Any suggestions on getting only 1 group?

The gun shoots a knot then if you shoot single shots hand chambered into the chamber without puttnig them in the mag?

"The gun shoots a knot ..."

I load up a mag, in this case a 10 rounder, let the bolt slam down from the release, the shots will alternate from one group to the other depending on which side of the mag they are from. More clear?

Is your gun a 5.56 chamber, or a 223 Rem chamber?

I cannot see how it would matter what side the round fed from unless you have a loose chamber and the case is tilted, or the bullets are getting deformed upon feeding.

It is a 5.56 (Wyde sp) chamber. BTW, I have seen different points of impact depending on weither or not the the round was chambered by the bolt release or by hand release of the bolt for the first shot from a mag.

Its actually a very common issue with an M14.

Have never heard of it in the AR though and I'm way familiar with it. Nothing is impossible though.

Tried 10 different mags? Thats what we did with M14 mags. Not sure if it'll help. I see you only tested the one and hence the suggestion to try others. The M14 ones sometimes had to be "numbered and attached" to a certain rifle.

Jeff

We used to load magazines in Viet Nam with 18 rounds to keep from stretching the lips and also (they told us) so the first round would come off on the correct side.

I couldn't tell any difference, but that's what we did.

Doesn't matter what side the first round comes from these days anyway.

Not at all sure about feed lips, ramps, mags etc... back then.

Jeff

I'm not sure it mattered back then, but you know how legends get started. One legend was that the ChiCom pistol, in 7.62 caliber, was a 9mm. The one that looked like a Colt automatic. We almost never saw 9mm, what did we know?

Whether it mattered, it was, however, Brigade SOP. So, that's how my unit did it.

The lips of the magazine were very problematical, however. We kept footlockers full of loaded magazines back at base, in case we needed emergency resupply, and I think the lips were softer, or maybe they got dinged around more from mishandling, whatever.

Also, there wasn't a really good way to carry mags back then...we used M 14 pouches, which were OK, but were not especially protective. Plus, they were canvas, wet, and heavy. Most additional ammo was carried in bandoleers made of thin cotton. Falling down on them was definitely not a good thing for the mags.

The mag follower was definitely different from the one today. Can't remember how, though. I still like the 20 round mags because you can get closer to the ground with them. I've got both, but the 20 is the one I carry in my patrol rifle.

I don't think I have 4 of the 30 rounders. I don't like them either.

I like the surplus 20s with the metal followers. Not all the happy about the new ones, but having said that I had to buy some new ones for my 6mm WOA upper and they are very well built, don't recall the brand, but they were not cheap, around 45 bucks or so.

That aluminum on the lips, easy to bend, fatigue, crack etc.... Combat wise I suspect the M14 mags were a better deal all around but heavier.

Jeff

Rost: have you tried the Orlites? I bought one of those and it has worked flawlessly so far. That, and my 10 round plastic DPMS have always worked great. My 30's and 20's are so-so.

Nope never tried plastic ones. Disallowed in highpower matches as not OEM so I've never tried them.

May have to by your suggestion though.

Jeff

DON'T get the plastic mags near Gunscrubber, ChemTool, any brake or carb cleaner! The plastic melts in a heartbeat. How do I know? Guess.

Bend, I'm not sure 'bout this, but in since I don't have any specific AR armorer experience, I'm just trying to use a "basic physics" approach to troubleshooting. Here's my thought. Is it possible that the ejector plunger is over-sprung and placing too much force on the chambered round? OR, as a second possiblility, the extractor is slightly out of spec and not grabbing the cartridge rim consistently? To my inexperienced noggin, this makes more sense than a mag problem, although the two could be intertwined. To ME, it seems that once the round is chambered, something is fouling up the consistency from shot to shot. Too much ejector tension could be pushing the cartridge cockeyed in the chamber. Just a SWAG, but hopefully gets some smarter people thinking along different lines-------------my smarts are all used up now.........

222, you are truly thinking it through.
I had not remembered some of those issues.
Simple test. Remove the ejector totally and see what gives. If that solves it.... If not, remove the extractor after that.

I don't think it can be either of them and would be much quicker to blame the mags, at least from my competition shooting background with M14s first.

Jeff

I really like my little 10 round plastic mag from DPMS. Never got solvents on it, not sure how I would, but I have gotten Breakfree on it and it didn't do anything.

222-

Found a guy in the area with the tools and knowledge to take the upper down to its major parts. We did not find any particular problem but were very carefull when tighting the barrel nut and aligning the gas tube when putting it back together. We shot it yesterday and it did fine. No change in POI noted!

Thanks all for the suggestions and support.

Excellent news!<img src="/ubbthreads/images/graemlins/cool.gif" alt="" />