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Page AR-15 » Ammunition
AR Sponsor: bravocompany
Posted: 5/11/2017 5:36:07 PM EDT
I recently purchased a new AR upper from PSA.  It's an mid-gas upper with SS pencil barrel and BCG.  I cleaned the upper and put it on one of my Anderson lower and started shooting it. I was using  Guatemalan IMG ammo from 1997 production.  I still have several thousand rounds of this ammo from about 16 years ago when they were $100 per 1k and it's my regular plinking ammo.  After 6 or 7 round I get my first FTE.  The fired bass is left in the chamber and when I drop a cleaning rod from the muzzle the brass falls out of the chamber easily.  Upon examining the brass it's obvious that the extractor had ripped through the rim leaving the brass in the chamber.  I used a chamber brush to clean out the chamber and clean the bore with bore snake.  I load up the rifle and start firing again and on the 5th shot it happens again...extractor had torn off the rim.  This time I change ammo and use Federal XM193 ammo and it goes through 18 rounds without problem.  Then I loaded IMG ammo again and within 6 round I get the same FTE problem.  Next I try CCI Gold Dot 64gr ammo and no problem for 18 rounds.  Finally I tried IMG again and within 6 rounds I get the same FTE problem.

Are there any known problem with IMG ammo that could be causing this problem?  I have fired several thousand rounds of IMG ammo through various AR weapons in past with only 2 bad rounds...both were duds.  

What's going on here?!?!?!

--------- UPDATE ---------

I finally had some time this past weekend to do some test with this rifle/ammo combo.

First I fired 30 rounds of Federal M193 ammo pretty fast (1 shot per second) in this rifle and had no problem.
Next I fired 20 rounds of CCI Gold Dot 64gr pretty fast (1 shot per second) in this rifle and had no problem.
Then I fired IMG ammo and on the 2nd round I get the same FTE/double feed problem.  I clear the FTE/Double feed and try again and on the 1st shot I get the same FTE/double feed.
Then I fired 15 rounds of Federal M193 and 15 rounds of CCI Gold Dot loaded alternately without any problem.
Finally I used the RRA carbine lower (from the RRA carbine below) with this upper and fired IMG ammo and on the 3rd or 4th round I get the same FTE/double feed problem and once cleared it happens again 1 or 2 rounds later.

Next used my 17 y/o RRA carbine with the same IMG ammo and I go through 50 rounds with no problem.

Then I used my 2 y/o PSA carbine (SS with pencil profile) with the same IMG ammo and I go through 50 rounds with no problem.

Finally I used my 10 y/o Bushmaster A2M4 rifle with the same IMG ammo and I go through 50 rounds with no problem.

I don't know what it is but this combo of IMG M193 ammo and the PSA SS midgas pencil barrel carbine just doesn't work.  I assume there may be a slight difference in the chamber dimension which is causing the problem.   There may be some issue with the ammo too but evidently other AR's can overcome the ammo "issue" but this upper is not able to.  This upper has worked reliably with all other factory ammo I've tried.
Link Posted: 5/11/2017 6:47:25 PM EDT
[#1]
From the information provided it sounds like you have a tight chamber. IMG could have excessive case-wall thickness causing them to fit tighter in the chamber upon extraction but given another couple thousandths of a second is cool enough to extract without issue. Possible fixes could include a heavier buffer, installing an o-ring in your extractor, installing an HD extractor spring, or all of the above.
Link Posted: 5/11/2017 7:05:41 PM EDT
[#2]
Your IMG all corroded and shit or is it shiny?
Link Posted: 5/11/2017 7:12:39 PM EDT
[#3]
Discussion ForumsJump to Quoted PostQuote History
Quoted:
Your IMG all corroded and shit or is it shiny?
View Quote
No, these are all shiny and clean.
Link Posted: 5/11/2017 10:28:07 PM EDT
[#4]
I am going with tight chamber. Dang. Sorry, but you probably will end up changing the barrel out. Your barrel will most likely run .223 fine though, just not 5.56.
Guat. ammo was often used to test function, so that is not it.
Link Posted: 5/12/2017 7:45:14 AM EDT
[#5]
Link Posted: 5/12/2017 7:57:31 AM EDT
[#6]
Discussion ForumsJump to Quoted PostQuote History
Quoted:
From the information provided it sounds like you have a tight chamber. IMG could have excessive case-wall thickness causing them to fit tighter in the chamber upon extraction but given another couple thousandths of a second is cool enough to extract without issue. Possible fixes could include a heavier buffer, installing an o-ring in your extractor, installing an HD extractor spring, or all of the above.
View Quote
I would do what this man says.... in this order. If you have a H2 or H3 buffer in another rifle, try swapping them and see if that makes any difference. The problem *might* go away after you break the gun in good, but you'll have to burn some more ammo to find out.
Link Posted: 5/12/2017 10:13:14 AM EDT
[#7]
I had a similar problem when I built my blackout pistol. Swapped BCG into my RRA carbine and problem followed.  Replaced extractor spring and added a "D" ring to it and problem was solved. 
Link Posted: 5/12/2017 1:13:30 PM EDT
[#8]
People saying its the case are more than likely wrong since it shoots everything else. My guess is powder is wrong for the rifle

ammo is bad, wrong powder for your rifle/gas system,

either trade it to someone, or shoot it in a different gun.


You might try a heavier buffer as mentions, but its just a bandaid
Link Posted: 5/12/2017 1:14:22 PM EDT
[#9]
Discussion ForumsJump to Quoted PostQuote History
Quoted:
I had a similar problem when I built my blackout pistol. Swapped BCG into my RRA carbine and problem followed.  Replaced extractor spring and added a "D" ring to it and problem was solved. 
View Quote
its ripping the rims, the extractor is GTG, the powder burn is wrong
Link Posted: 5/12/2017 2:54:20 PM EDT
[#10]
I have shot over 3k rounds of this IMG ammo (same lot number) in over a dozen other AR pistols/carbines/mid-length/rifles with pistol, carbine. mid length and rifle gas systems in past 6 or 7 years...even in 2 bolt rifles and I've never had any problem before.  This is the first and only time I've had this problem happen.  
I don't think the issue is with the extractor as it's is holding the rim hard enough to take a chunk of brass off the rim during failed extraction.
Link Posted: 5/12/2017 5:54:31 PM EDT
[#11]
Is the IMG the only ammo you have tried so far in quantity in the new rifle ?  If so, try the different ammo in higher quantity to see if issue crop up with it too.  PSA may or may not want to do something about it if only happens with older surplus ammo.

Rob
Link Posted: 5/12/2017 7:11:46 PM EDT
[#12]
Link Posted: 5/12/2017 7:33:51 PM EDT
[#13]
Discussion ForumsJump to Quoted PostQuote History
Quoted:
From the information provided it sounds like you have a tight chamber. IMG could have excessive case-wall thickness causing them to fit tighter in the chamber upon extraction but given another couple thousandths of a second is cool enough to extract without issue. Possible fixes could include a heavier buffer, installing an o-ring in your extractor, installing an HD extractor spring, or all of the above.
View Quote
This.
Link Posted: 5/13/2017 10:03:53 AM EDT
[#14]
You bought a precision barrel, shoot precision ammo, problem solved
Link Posted: 5/16/2017 9:00:40 PM EDT
[#15]
I'll bet the chamber is tight either way, is it 5.56 or 223 Wylde?
Link Posted: 5/17/2017 3:46:46 PM EDT
[#16]
Discussion ForumsJump to Quoted PostQuote History
Quoted:
I'll bet the chamber is tight either way, is it 5.56 or 223 Wylde?
View Quote
It's 5.56 NATO chamber
Link Posted: 5/21/2017 10:59:45 AM EDT
[#17]
Before jumping to the conclusion that it's the chamber I would try treating it as if it were over-gassed. It could be that the BCG is moving too quickly and the extractor is trying to pull the case out while it is still expanded and clinging to the chamber walls.

I would try moving to a heavier buffer and maybe even an extra-power buffer-spring and see if that doesn't fix the issue for you. You aren't running a lightweight BCG are you?  It could be a tight chamber but IMHO it is more likely that it is over-gassed...
Link Posted: 5/23/2017 4:16:54 PM EDT
[#18]
Discussion ForumsJump to Quoted PostQuote History
Quoted:
Before jumping to the conclusion that it's the chamber I would try treating it as if it were over-gassed. It could be that the BCG is moving too quickly and the extractor is trying to pull the case out while it is still expanded and clinging to the chamber walls.

I would try moving to a heavier buffer and maybe even an extra-power buffer-spring and see if that doesn't fix the issue for you. You aren't running a lightweight BCG are you?  It could be a tight chamber but IMHO it is more likely that it is over-gassed...
View Quote
No the lower is just standard PSA carbine lower with standard weight spring and buffer.  I checked my notebook last night and according to my notes I used this lower with my 300 BLK upper for couple months (about 500 rounds fired) and I never had any problem and before that I used it with my PSA's PTAK 5.56 caliber 16" carbine upper for about 2 months (about500 rounds fired)...again without any problem.
Link Posted: 6/19/2017 12:53:51 PM EDT
[#19]
Finally got around to do some testing on this upper and IMG ammo.
See OP for update.
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