Blown Primer in Wilde Chamber (Update w/range results)

hm1996

hm1996

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Staff member
Blew a primer in my Bushmaster Predator today. Temperature was in the low 90's, ammo had not been in sun and barrel was not hot. It is supposed to have a Wilde chamber and handle both .223 and 5.56 ammo.

35352697480_54441d5cac_c.jpg


Previously had fired only handloads in the rifle, w/o any problems.
Purchased some American Eagle XM193BL, 55 gr. FMJ 5.56 ammo and the fourth round blew a primer. The problem became apparent when the 5th round wouldn't chamber. Tipped rifle and it fell out, so tried to chamber another round and bolt still wouldn't close, but this time the round stayed in chamber. Dropped bolt again to try to catch and eject 6th round unsuccessfully. That's when I discovered the blown primer. It was wedged between ejector and rim around bolt face:

35352543110_3929a80661_z.jpg


At this point I felt quite fortunate that I did not have a slamfire as the primer on bolt face slammed against head of loaded rounds 3 times before I realized what the problem was!

On closer examination of the ammo, I find at least two different cases have been used (only opened one box so far).

The two cases used are: LC 11 w/o NATO symbol and no primer crimp, and LC 11 w/crimped primer and NATO symbol. I suspect the cases w/o NATO symbol to be softer brass of the two because both of those cases show ejector indentation on case head, one blew primer, other didn't.

34930942933_a08c06e96e_c.jpg


Here are case stats on the 5 fired rounds.

LC 11 w/o NATO stamp, blew primer: Exp. ring = .377", case wt.= 92.6 gr.
LC 11 w/0 NATO stamp, no blown primer: Exp ring=.376", case wt.= 93.0 gr.
Both cases showed distinct ejector imprint on case head.

Three LC 11 w/NATO stamp, no blown primers: All three Exp. rings=.375", case wt. 92.0; 92.7; 92.7 gr. respectively w/no ejector marking on case head.

Checked a couple of WW cases which have been fired ? times w/warm handloads and case exp. ring measured .3745" on both. Primer pockets still snug.


Anyone else have similar problems?

Regards,
hm
 
Because it's stamped ".223-5.56MM" doesn't mean it's a Wylde chamber. The unfortunate thing is that each of the manufacturers ream their own barrels to their own specifications, and from what I've seen, there are some differences from manufacturer to manufacturer.

I would check the barrel marking also and not just go by what's stamped on the lower...could be a different upper on it.

Sounds like either way, the 5.56 is going to be tight and you might want to just shy away from that.

http://ar15barrels.com/data/223-556.pdf
 
here we go again. 223 vs 5.56

my ar-10t used to blow primers. i fought with armalite to get them to fix the gun, they said there was nothing wrong with it, that i just needed to use factory ammo. so i ran a box of remington through it. it blew some of those primers too. then they said i needed to used better quality ammo like federal match, so i ran a box of that, it still blew primers. i sent it to them, then bushed the gas port down and it helped but did not fix it. finally i made the gas block adjustable and never had a problem again. it would sometimes blow primers, but even when it didnt, the case heads were expanded and the brass was junk. but they would always have an ejector mark/ smear.
 
Check for copper fouling in the throat area of your barrel. That can cause overpressure in the chamber and blow primers.
 
The OP wrote: "Purchased some American Eagle XM193BL, 55 gr. FMJ 5.56 ammo and the fourth round blew a primer."

I'd be on the horn with Federal, personally. It sounds like this ammo is loaded WAY too hot for safety, and they should be made aware of it. They'll probably offer to replace the ammo; if they don't, suggest it to them.
 
webopper is correct, it isnt the lower you need to look at its the barrel. Some of those are even marked wrong. I would have it checked before I shot any more 5.56 ammo through it. Just my 2 cents
 
Originally Posted By: WebopperBecause it's stamped ".223-5.56MM" doesn't mean it's a Wylde chamber. The unfortunate thing is that each of the manufacturers ream their own barrels to their own specifications, and from what I've seen, there are some differences from manufacturer to manufacturer.

I would check the barrel marking also and not just go by what's stamped on the lower...could be a different upper on it.

Good advice, thanks, but this is a factory Bushy Predador (as opposed to a parts gun of unknown pedigree) and their ammo recommendation which accompanied rifle states it is chambered to fire both .223 and 5.56 ammo. I am unable to find the chambering info but pretty sure I read somewhere it had the Wylde chamber. May be mistaken, but obviously it is chambered for both rounds.

BushmasterAmmoRecommendations.jpg


Originally Posted By: Webopper
Sounds like either way, the 5.56 is going to be tight and you might want to just shy away from that.

http://ar15barrels.com/data/223-556.pdf


You sure have that right! That's a great chart re: different chambering reamer dimensions; thanks again! Originally Posted By: JerrySchmitt In your case I would worry more about the ammo you are using than the rifle for now. When you shoot junk ammo you get problems.


The ammo was purchsed from Midway and is supposed to be manufactured to mil spec. Bushmaster literature above states, "Bushmaster personnel have used the following ammunitions.....American Eagle (manufactured by Federal) and Midway stated on their web page:

" XM193 product is first run, first quality product manufactured at Lake City Army Ammunition Plant for Federal Cartridge and is made to Federal specifications typical for commercial ammunition. "

Have no experience w/factory ammo as I have shot virtually nothing other than my handloads for the past 60 years, but based on all available literature, I would not have considered the XM193 ammo to be "junk" although it does seem to meet that criteria in my rifle . I was surprised that this "newly manufactured" ammo used two different headstamped cases and still suspect the cases w/o the NATO headstamp may be soft brass allowing for expansion of head of case based on the measurements of the only two cases fired and the fact that both of these rounds had ejector marks on case heads.
I don't plan to shoot any more of the ammo in that rifle.

Originally Posted By: CAFRCheck for copper fouling in the throat area of your barrel. That can cause overpressure in the chamber and blow primers.

No fouling in the barrel.

Originally Posted By: Terry N.The OP wrote: "Purchased some American Eagle XM193BL, 55 gr. FMJ 5.56 ammo and the fourth round blew a primer."

I'd be on the horn with Federal, personally. It sounds like this ammo is loaded WAY too hot for safety, and they should be made aware of it. They'll probably offer to replace the ammo; if they don't, suggest it to them.


Excellent suggestion. Think I will give them a call and ask about mixed headstamps as well as get their thoughts as to the possibility that the failure could have been a soft brass case as opposed to higher pressure??
smile.gif


Thanks, guys for your thoughts on the matter. Have an old sayin' around my place to the effect that "Two heads is better than mine."

Regards,
hm
 

"Have no experience w/factory ammo as I have shot virtually nothing other than my handloads for the past 60 years, but based on all available literature, I would not have considered the XM193 ammo to be "junk" although it does seem to meet that criteria in my rifle . I was surprised that this "newly manufactured" ammo used two different headstamped cases and still suspect the cases w/o the NATO headstamp may be soft brass allowing for expansion of head of case based on the measurements of the only two cases fired and the fact that both of these rounds had ejector marks on case heads.
I don't plan to shoot any more of the ammo in that rifle."




hm1996, that is exactly your problem I would bet.
I saw the exact same thing hapeen with a box of factory Hornady 22-250 ammo and once it was returned to the factory they said it was too soft brass and replaced it.
 

What this sounds like to me is timing. The bolt head is to lock until the bullet passes the gas block. Then the gases knock back the bolt that unlocks the bolt head.

Your barrel breach and you bolt head are not locking.

The head space is not set correctly.
Bolt head is worn.
Breach is worn.

I own a Bushmaster 20" Predator Upper Receiver/Barrel Assembly Model #F1007682. That has nothing to do with the lower; it will fit any lower RRA or even a Plum Crazy.

Just because your lower is marked with 5.56/223 does not have anything to do with the upper. My Bushmaster 450 or 6.8mm upper will work with your lower.

Where did the upper come from? Send it back to ever made it or find a AR Armor. You are getting a straight blow back and your rifle is unsafe to fire.

An AR Armor can tell you what is wrong in about five minutes.
 
Originally Posted By: You sure have that right! That's a great chart re: different chambering reamer dimensions; thanks again! Originally Posted By: JerrySchmitt In your case I would worry more about the ammo you are using than the rifle for now. When you shoot junk ammo you get problems.


The ammo was purchsed from Midway and is supposed to be manufactured to mil spec. Bushmaster literature above states, "Bushmaster personnel have used the following ammunitions.....American Eagle (manufactured by Federal) and Midway stated on their web page:

" XM193 product is first run, first quality product manufactured at Lake City Army Ammunition Plant for Federal Cartridge and is made to Federal specifications typical for commercial ammunition. "

Have no experience w/factory ammo as I have shot virtually nothing other than my handloads for the past 60 years, but based on all available literature, I would not have considered the XM193 ammo to be "junk" although it does seem to meet that criteria in my rifle . I was surprised that this "newly manufactured" ammo used two different headstamped cases and still suspect the cases w/o the NATO headstamp may be soft brass allowing for expansion of head of case based on the measurements of the only two cases fired and the fact that both of these rounds had ejector marks on case heads.
I don't plan to shoot any more of the ammo in that rifle. Thanks, guys for your thoughts on the matter. Have an old sayin' around my place to the effect that "Two heads is better than mine."

Regards,
hm [/font





When I called it junk I meant as a "lot" of ammo. I would expect all case head markings to be the same and all primers to be staked or not staked the same. It looks like they grabbed a handful of this and a handfull of that and tossed it in a box. I haven't bought or shot a round of factory ammo in years except in my 9 MM pistol.

Over the years I have shot a ton of LC brass in my rifles with never a problem. The fact that Federal is using LC brass to re-manufacture ammo to Mil Spec leads me to believe that they are cutting corners to sell junk ammo. Mil spec and fly specks don't mean nutten.
 
Originally Posted By: willy1947
What this sounds like to me is timing. The bolt head is to lock until the bullet passes the gas block. Then the gases knock back the bolt that unlocks the bolt head.

Your barrel breach and you bolt head are not locking.

The head space is not set correctly.
Bolt head is worn.
Breach is worn.


Where did the upper come from? Send it back to ever made it or find a AR Armor. You are getting a straight blow back and your rifle is unsafe to fire.



Huh? If it fired one time unlocked he would likely have been posting from the ER and his rifle would be in pieces. It worked fine with reloaded ammo, this is almost surely an ammo problem.
 
Originally Posted By: willy1947
What this sounds like to me is timing. The bolt head is to lock until the bullet passes the gas block. Then the gases knock back the bolt that unlocks the bolt head.

Your barrel breach and you bolt head are not locking.

The head space is not set correctly.
Bolt head is worn.
Breach is worn.


Where did the upper come from? Send it back to ever made it or find a AR Armor. You are getting a straight blow back and your rifle is unsafe to fire.

An AR Armor can tell you what is wrong in about five minutes.

If rifle had fired out of battery, there would have been much more damage than a blown primer.

As stated two posts above yours, the rifle is a factory built, Bushmaster Predator; not a parts gun. It has relatively low round count, somewhere in the neighborhood of 600-700 rounds through it. When I first purchased the rifle, I did shoot one box ea. of different factory loads down to and including Win. white box to establish a base line and all functioned perfectly and grouped 1 moa or less. It has since seen an exclusive diet of my handloads which also function flawlessly.
I think we have pretty well established that there is no fault with the rifle, just an ammo problem.


Originally Posted By: JerrySchmittWhen I called it junk I meant as a "lot" of ammo. I would expect all case head markings to be the same and all primers to be staked or not staked the same. It looks like they grabbed a handful of this and a handfull of that and tossed it in a box. I haven't bought or shot a round of factory ammo in years except in my 9 MM pistol.

Over the years I have shot a ton of LC brass in my rifles with never a problem. The fact that Federal is using LC brass to re-manufacture ammo to Mil Spec leads me to believe that they are cutting corners to sell junk ammo. Mil spec and fly specks don't mean nutten.

Sure can't disagree with that, Jerry! Based on description, I did expect this to be newly manufactured ammo, not reloads, but looks like maybe the floor sweepings at the end of the week.
lol.gif
I'm wondering if the brass is new or once fired mil-surplus???

I really believe the problem to be soft brass due to the ejector imprint on the case heads of both of the non-NATO marked cases. Another factor that could affect the case hardness is the staking of the primer on the NATO brass as this would tend to harden the case head a bit more than the uncrimped LC 11 brass. Lots of unknowns, but the fact remains that it is this lot of ammo that is causing the problem in this rifle.

I notice that this particular ammo is no longer listed @ Midway; can't help but wonder if others may have had issues, or maybe they just sold out????

I, too have used lots of LC brass (mostly in 30-06) over the years and was my favorite brass.


Originally Posted By: 204 ARHuh? If it fired one time unlocked he would likely have been posting from the ER and his rifle would be in pieces. It worked fine with reloaded ammo, this is almost surely an ammo problem.

I agree, 204.

Intersting discussion, guys, thanks for your thoughts.

Regards,
hm
 
Originally Posted By: hm1996I think we have pretty well established that there is no fault with the rifle, just an ammo problem.

HM, I wouldn't automatically rule out the rifle as a contributing factor in this. It sounds like this is the first time you have shot the 5.56 in it, and that would be quite the coincidence to have that giving you problems. As you mentioned, it could be soft brass in the batch of ammo you ran, but don't rule out that it could also be that your chambering is just tight enough to increase the pressures on the 5.56 loads. I know you said you have run a bunch of handloads through it, but I'm assuming those were .223 loads, and again, the 5.56 could be just enough different to increase the pressures to the levels you are seeing.

Hopefully you find out that it is just a thing with the batch of ammo you were running...

This is an interesting conversation. I'm curious now to see what it really is.
 
5.56, 223, Wylde, has NOTHING to do with it.

Said ammo is some of the softest brass ever made by anyone, loose primer pockets occur regularly. The fact that it was 90° may have been a contributing factor also. Take that and run with it........
 
Originally Posted By: JerrySchmittIn your case I would worry more about the ammo you are using than the rifle for now. When you shoot junk ammo you get problems.


+1
 
Originally Posted By: 2muchgun5.56, 223, Wylde, has NOTHING to do with it.

Agreed; I'm convinced it is an ammo problem. The reason for bringing chamber up in the first place was to establish the fact that this rifle is indeed chambered to accept that ammo (5.56mm).

Originally Posted By: 2muchgunSaid ammo is some of the softest brass ever made by anyone, loose primer pockets occur regularly.


Really!? That is the type of input I was looking for and was not aware of. For the most part I use Win. brass in the .223 so was not aware of the soft reputation of LC 5.56 brass.
Does that apply to both the NATO headstamped LC cases as well as non-NATO cases? My entire experience with this ammo is the 5 rounds fired up to and including the one that blew primer.

I feel sure the 90* temp. contributed to a bit higher pressures than might be the norm, but you would think that "mil spec" ammo would be loaded for safe use even at much higher temps encountered in the sandbox, especially ammo that is often fired in full auto mode.

Regards,
hm
 
You guys are probably right, but to automatically assume that is short sided and dangerous in my opinion.

I'm sure there are a lot more issues with that ammo than there are issues with the weapon itself, but it does happen...that's all I'm saying.

If you jump to page 2, you'll see where he sent his back in and BM said the chamber and headspacing was too tight. They fixed it up for him, and it's all good.

http://www.ar15.com/forums/t_3_16/479900...html&page=1
 
the problem i had with my armalite ar10t was too large of a gas port. there was enough gas being applied to the bolt that it was opening before the pressure dropped enough. so when the bolt was unlocking, the pressure was still high enough to expand the case head. all ammo did this, some more than others.
my above statement is my THEORY of my situation. however, your situation may be similar. i would fire it with some different ammo and see what happens. if that blows primers or expands case heads, then i would suggest that it is the rifle.
 
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