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Posted: 3/13/2005 5:00:22 AM EDT
Bought a new BM 16" A3 last week. Took it to the range yesterday, loaded a Mag and Charged the weapon. Just when I was getting ready to shoot, the range called a cease fire to change out targets. So I removed the Mag and tried to pull the charging handle but it was stuck. After I pull and pulled the live round finally ejected. I retrieved the round, the casing had slight scratching down the side and a minor dimple on the primer. Once the cease fire was over, I examived the chamber and all looked good so I tried it again with a new round and the same thing happened. Being new to AR-s but not guns I started examining the situation and was looking at the rotatory bolt mechanism. The bolt fully closes without a round but with a round it looks like the bolt should rotate a few more degrees to fully engage the locking mechanism. I was using some reloaded ammo from a friend ( who also was shooting a new bushmaster with no problems). So today I am off to get some new quality ammo and see if that makes a difference. But clould my head space be wrong, should I send this to Bushmaster or am I missing some thinghinking.gif
Link Posted: 3/13/2005 5:06:37 AM EDT
What kind of mag?
Link Posted: 3/13/2005 5:13:28 AM EDT
Brand New Bush Master. But even if I dropped a round into the chanber and closed the bolt with out a mag it does the same thing
Link Posted: 3/13/2005 5:37:06 AM EDT
maybe I'm talking out of school here, but I believe that's normal.  The firing pin in the ARs freefloat.  Inertia from the bolt slamming home allows the pin to slightly hit the primer.  (one of the reasons it's not recommended to cycle live ammo off range)  5.56 ammo has hard primers for this reason.

As far as the scratches, it's from the feed ramps.  It happens on my DPMS, my wife's Doublestars, (all 3) my RRA, and just about every new AR rifle I've ever shot.  If it bugs you, you could polish the sharp edges, but it won't hurt anything as long as it's not causing it to hang up.  It will also shoot out over time as the sharp edges wear.

For the charging handle being stuck--Probably the locking lugs/cam pin being a little tight.  They will also wear in (I use NO lube for the first 100 rds to 'encourage' the wear process.  After the first 100 rds, I clean it and put a little dab of moly lube on the lugs and cam pin, lube everything per the manual)   If it were my rifle, I'd just shoot the hell out of it and have some fun.  If it gives you trouble, post again....the hive mind will hook you up!
Link Posted: 3/13/2005 6:08:58 AM EDT

It IS NOT uncommon to see a dimple on the primer of a round chambered in an AR.  

Other than the usual safety rules of never let your muzzle cover anything you would not want destroyed... it is not a concern.  I am not saying it is impossible for a "slam fire"... I am saying this is common in ARs.  If it ever happens... and you follow safety rules... there is little concern... BECAUSE... you always have the muzzle in a safe direction.  Right?
Link Posted: 3/13/2005 6:40:21 AM EDT
Not so much worried about the dimple as the fact that I can't get the charging handle to pull back without great force and the rotary bolt is not fully engaged when the bolt is closed with a round in it. I am afraid that when the cartridge is fired that undue force will be applied to only part of the locking lugs inlieu of the full width of the lugs. Will find out today. My thought is that the cartridges are to long or the headspacing is too short as the bolt closes correctly without a shell in it.
Link Posted: 3/13/2005 6:41:27 AM EDT
dent on primer?  normal.

double check the chamber.   make sure it's clean.

maybe a dirty and/or rough chamber.
Link Posted: 3/13/2005 7:43:18 AM EDT
Dimple is normal.  90% chance the reaoad is not sized correctly. 5% chance of rough spot ot chip on bolt or chamber, close to 0% chance it's a headspace problem.

You are headed in the right direction.  Check it out with new USA made ammo.  Should extract unfired rounds very smoothly with no additional force required.
Link Posted: 3/13/2005 11:07:27 AM EDT
Bought new 3131A ammo and all is well. Trashed the reloads. Thanks for the help guys
Link Posted: 3/14/2005 10:06:22 AM EDT
I was using some reloaded ammo from a friend

Yep, he probably did not full length resize.
Link Posted: 3/14/2005 10:41:12 AM EDT

I was using some reloaded ammo from a friend

Yep, he probably did not full length resize.

That is exactly what I was thinking. Either that or the brass is not trimmed to the proper length. But trimming does not explain the hard charging handle pull. It does however, explain the bolt not fully closing.
Link Posted: 3/16/2005 7:31:51 PM EDT
ditto on the resizing.  sounds like the case overall length or neck length is too long.  best way to check is to hand place a round into the chamber and then SLOWLY let the bolt in.  you should be able to push the forward assist slightly and the bolt will lock.  if not the brass is out of spec.  by letting the bolt slam shut you are forcing the brass into the chamber which can cause it to stick. if it were to cause the case to collapse or bend in severely an overpressure issue could result.
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