Que?


...

i shot 60 rounds of this same IMI lot through a BA "556" chambered 16" pencil middy yesterday and shagged most all my brass and not one loose primer. the spent cases ejected in the same spot as some prvi 193 i had too.

Have a similar issue with ZQI 5.56 when shooting my 11.5" SBR suppressed.  No issues unsuppressed or out of a 16" barreled AR suppressed.  Brass had loosish primer pockets (even with the crimp) and it started popping them, jamming up the FCG.  There's also some moderate pressure signs when shot suppressed.  No issues with any other ammo or handloads.  Haven't tried IMI though.

Not the same load... but same issue with another type of IMI 5.56 ammo:



http://www.ar15.com/forums/t_3_16/696873_Problems_with_IMI_77_gr_razor_core_update_7_20_16.html

My guess is that's a gas port.

That's the only thing I could figure.  I wasn't sure if it was some sort of imperfection and ol' Molon was showing us a stinker from a reputable manufacturer.

 
He's showing you what a gas port with no tearing looks like on a high-quality Krieger barrel - with zero rounds fired.

If you look at his other bore-scope photos, you can see a tear will start at the gas port (even with as little as 500 rounds down the tube, or less IIRC) on some barrels.





ETA: Link to his gas port erosion thread: http://www.ar15.com/forums/t_3_118/687750_.html




 

Have you seen actual mil-spec (chrome-lined, 1x7) Colt barrels that were not true 5.56 chambers? Will armorer's go/no go gauges tell the truth?

From memory...  Yes and no.  Military gauges are not SAAMI spec...and I'm not sure what the exact spec is on mil gauges.  Additionally, Colt reportedly has slightly different chamber specs for various SBR 5.56 guns.  From years back, I recall that actual mil spec gauges were somewhat hard to come by.  

I haven't gauged enough rifles to say definitively.  I have seen commercial rifles that would not close on a Go Gauge.  

Some of the DOD Armorers on here could likely chime in with better info.  

I always start with the gauges...bought a set of 10 years back for one of my first ARs that go from super short to waaaay too long plus a throat length measurement tool.  It at least gives me a baseline.  YMMV.

Minor update:

I fired a few more rounds this weekend and all had signs of excess pressure and several blew primers.  One primer got up on top of the bolt carrier group and was flattened between the cam pin and bolt carrier.  It completely seized up my AR and required a cleaning rod and a big hammer to get unstuck.  Even through another Colt AR there was a flat primer, ejector mark, and bent rim.  That makes two LaRue, one Noveske, one PSA, and one Colt (all marked 5.56) that had pressure issues with this ammo.

I've been in contact with the importer (thanks for putting us in touch, Metro6) and he offered a refund or replacement.

i have 1200 round of this same lots and shot through almost 100 without issue, i'll trade you 2 boxes. i wanna try it out.

I took some pictures of it, I'll try to post them up tonight.

Here are pictures of his BCG. The primer is wedged in front of the cam pin.

If there is problem with IMI lot 212G, then I would expect a recall, followed by refunds or replacement.

Had similar problem with Hirtenbergers. Primers popped out. Was overpreassure in the 20 inch barrel. In the 16 inch barrel the popping out of the peimers dissapeared. (Both barrels 5.56)
Using a Chronograph the hirtenbergers were too hot. If a lot  peoblem, I do not know. I suggest you to check the speed.

shot 3 full mags of this suspect lot today thru a LWRC M6 IC 14.7" with ZERO popped primers.

I got 1200 of this from lot 235/F, guess I need to go try some out

Still interested to hear the resolution. Now that I look closer, (and others have already pointed it out) iI do see the high pressure signs.

3 1200 rd cases of 212/G here.  Haven't had time to test. Let us know how it works out, Cap.

As an aside, does anyone know when IMI will import the next run of M193 1200 rd cases? I was planning on getting a few more, but it seems all dealers are out of it.

Today, I had the opportunity to shoot 150 rounds of IMI Lot 212G M193 through two different uppers.
A RRA lower was used for both uppers.  Roughly half the 150 rounds were put through each upper.  It was 86 degrees F out today in Iowa during the range session.  I bought a 1200 round case of this ammunition from SG Ammo a few months ago.

First, I fired a Colt M4 upper with fixed extended FH.  I had 3 popped primers.  None of the 3 popped primers resulted in a stoppage.

Second, I  used a BCM M4 upper with fixed extended FH.  There were no popped primers or stoppages.







 

Interesting. I was a member at one of the largest indoor ranges in CO up until about a year ago. Right around that time they decided to quit selling IMI due to all of the "loose primers and bullets" they were seeing with it. I figured it was just some LGS rumor/myth, but this thread has me wondering if IMI has some legit quality issues from lot to lot.

Has anybody seen over pressure in 212/G lot that came in the commercial boxes vs the mil ones?

loose bullets? really?

i've gone through plenty of this stuff dating back to the lots in 2014 and havent had any problems, in the M193 and 77gr razor core.

Me =  Not a DOD armorer but...

Headspace gauges won't tell you much of anything if it's a simple .223 vs. 5.56 chamber difference problem.

The major difference between .223 and 5.56 isn't headspace, it's throat dimensions and freebore and that's what potentially causes a high pressure situation.

Look at the reamer Michiguns has listed here - http://www.m-guns.com/tool_new.php?product=reamer

Notice this line in the description - Popped primers are due in part to the tighter, shorter freebore and shorter, more abrupt throat of the .223 chamber, causing a pressure spike with the hotter, mil- spec ammo. This reamer will address these areas as well as making sure the neck diameter is not too tight or short, without changing headspace. It does not cut the shoulder or anything behind it; it stops off on the shoulder..

No cut on shoulder = no change in headspace.

If we're still unsure, lets look here -

http://www.ar15barrels.com/data/headspace.pdf

And if we're really really still  unsure lets look for the reloading die makers that list different dies for .223 vs. 5.56... They pretty much don't? Correct. That's because the shoulder dimensions and headspace are effectively identical between the 2 cartridges. How to deal with the freebore and throat differences are left up to the person doing the reloading.

NOW we are getting somewhere. that makes more sense that anything else i've read abotu the 223 vs 556 chamber issues.

is it possible companies make a chamber in 556 but have 223 type freebore in order to increase accuracy, while retaining the "556 chamber"?  in which case, makes the 556 chamber useless...

thanks for posting that.

PSA:  The freebore is part of "the chamber".  Basically speaking, a chamber consists of:

>  the body

>  the shoulder

>  the neck

>  the freebore

>  the leade

So to answer your question, any particualar chamber can have combinations of the above dimensions.  

Also, freebore isn't just a matter of length, it's also a matter of diameter.  For example, the freebore of the 223 Wylde chamber is narrower than the freebore of a 5.56mm NATO chamber, lending to its improved accuracy over a NATO chamber.

Additionally, the angle of the leade can come into play in the various chambers along with all the other variables.





5.56mm NATO versus 223 Remington:  Chamber Differences


A SAAMI spec .223 Remington chamber will have a shorter leade with a sharper angle to the leade and a shorter amount of effective freebore than a 5.56mm NATO chamber. The freebore itself will also be narrower in the .223 Remington chamber.


raw pics courtesy of Ned Christiansen


With all other things being equal, the 5.56mm NATO chamber with its longer and shallower angled leade and longer amount of effective freebore will produce less chamber pressure than a .223 Remington chamber, when firing .223 Remington SAAMI Spec ammunition. Because of this, 5.56mm NATO amunition can be loaded to a pressure that would be considered excessive in a .223 Remington chamber, yet acceptable in a 5.56mm NATO chamber. (Pressures are measured using different methods between the two systems.)


The leade of a SAAMI 223 Remington chamber.






The official SAAMI 223 Remington drawing.








From Jeff Hoffman, co-owner of Black Hills Ammunition

“The 5.56 IS a higher pressure/velocity cartridge, but it is made to a military standard, with different test methods, (and therefore is not easily directly comparable to .223 pressures) . . . the general spec for US 5.56 ammo is 58,700 psi max, measured at case mouth. . . Please note this is a different method than SAAMI transducer or copper crusher, as used on commercial ammunition. 5.56 ammunition spec results in ammunition loaded to a higher pressure level than commercial .223, but the test methods specified are different . . .The spec calls for a different pressure test method than SAAMI spec ammo, and is not directly comparable . . . “


Here's a very interesting quote posted by Ned Christiansen on M4carbine.net:


". . . In short, you can safely fire all 5.56 AND 223 ammunition in a gun properly chambered for 5.56. You MUST NOT fire 5.56 ammunition in a 223 rifle. As case in point, I fired XM193 5.56 ammunition in a 223 test barrel with average pressures (conformal transducer) of 72,550 psi, and peak pressure registered at 76,250 psi. . ."

Since the SAAMI MAP for the .223 Remington is 55,000 PSI, that puts XM193 fired from a minimum spec .223 Remington chamber at 17,550 PSI over the maximum.


(The following is just a generalization to give a graphical demonstration of concept. DO NOT hold me to the exact numbers as they are not correct and they ignore the difference due to the different methods used to measure chamber pressure.)

Consider the left graph pictured below; M193 fired in a 5.56mm chamber. The pressure is within the MAP limit. Now, take the exact same round, (same powder, same charge of powder) and fire it from a .223 Remington chamber; pictured in the right graph below.

Because the .223 Remington chamber has a shorter and sharper angled leade compared to the 5.56mm chamber as well as a shorter effective free-bore, the bullet engages the rifling sooner in the .223 chamber than it would have in a 5.56mm chamber. This causes the pressure to rise faster, peak sooner and reach a higher (and per SAAMI, unsafe) level than it would have if the round had been fired from a 5.56mm chamber.






.....

Thanks!

As usual, Molon comes along to explain...

This thread is very informative. Thanks to all.

I checked my 2 cases of IMI 193 neither were the lot in question, I'll try to fire some from my Colt and Larue to see if there is any difference. I'll report back with any issues.

Late to this thread, sorry, but I was able to shoot about 15 rounds of the ammo in question (lot 00212/G), and I had no issues from my 10.5 SBR.  I inspected all the fired cases thoroughly, and there were no popped primers, and no signs of over pressure that I can tell.  They did produce the smallest group of the day.  I'm shooting at 50 yards so basically it was one ragged hole at about 3/4" in diameter.  This was slightly better than Wolf Gold and Federal (LC) XM193.  I think most of the variance came from my poor shooting than the ammo.  I'll keep looking for problems with this IMI M193 lot, but yesterday it was great.

Update:  shot another 60 rounds (2 boxes) of lot 00212/G yesterday and all went bang with good groups (for me) and had no issues with primers.  All primers were still in the cases with a nice dimple, cases show no sign of over pressure.  I'll still be on the lookout for anomalies on this lot, but right now, from my 10.5" SBR, I'm calling this ammo good.
ETA: Barrel is a 10.5"  BAD Ultra Match Lightrigid barrel chambered in .223 Wylde

Update:

I fired another 60 rounds of this lot through a third LMT MRP barrel with no issues.  Function and accuracy were good, with no signs of high pressure or loose primers.

FINALLY!! i got some popped primers today with my 212G lot.

it was about 90 degrees and ammo had been sitting in the sun on the tail gate. barrel was a noveske 16" double chrome. i was shooting paper and shot 15 rounds and had 3 popped primers.

guess this ammo will be relegated to other barrels or wait until winter time when its colder.

think i'll try some older lots i have from 2012 and 14 thru this noveske too...

Has it been decided that the primer problem was only with the lots mentioned concerning the M193 and 77 gr, and did not affect other lots? I really want to buy a case of 77 gr but this keeps nagging at me.. I really do not think CBC is coming back any time soon and want to buy before the rush is on...

i have IMI m193 in lots from 2012 and 2014 that have not had problems in this same nosveske barrel that popped primers today in with the 212G/2015 lot. and as i said in other paota here, i have run the "bad lot" 212G in 2 other barrels without popped primers.

after seeimg molon's post about chambers, i wonder if certain barrel companies are playing around with specs in order to get better accuracy, at the expense of over pressure with hot 556 rounds. maybe?

i can say this particular noveske barrel i have is by far the most accurate chromelined barrel i have ever had.

Just shot a box of the problem Lot#
SR 15 Mod 1
ran great, basically a mag dump and no hiccups...i know it's not a huge number of rounds but it is my "stash" ammo so i'm not blowing thu 100s of it (i have previously run 5 boxes in variuos outings but never paid specific attention to it)

alrighty now.....here is some new info.

i had good luck running this lot thru a BA nitrided and an LWRC nitrided without any popped primers.

i did experience popper primers thru a noveske 16" middy chrome. now today i had a case actually get stuck and ripped the rim off shooting it thru a BCM 20" GI profile chrome lined.

so 2 good barrels, both nitrided.
and 2 barrels with issues, both chrome lined.

No issues in my 10.5" BAD SS .223 Wylde Barrel (neither chrome lined nor nitrided).  I no longer have my 16" Bushmaster which had a chrome lined 5.56 barrel.  Would have liked to try that rifle to see if chrome lining is really correlated.  Given your experience, you have to say it is a strong possibility.  Thanks for the info.

i sure would expect the wylde chamber to have pressure issue but good to hear you dont. one poster mentioned alot of 556 NATO marked barrels bay not be cut right too. i suppose there is the possibility that companies could be using chamber reamers too long and they get worn down, making chambers titghter than they should be.  

i have a couple other chrome lined barrels to try this ammonin too, a 12.5" noveske and 2 FN barrels,  20" GI amd 16" middy that i'll try too.

update on 2 more barrels i have.

FN 16" midgas chrome lined: no troubles in 30 rounds.

FN GI m16a2 profile chrome lined: popped primers within 5 rounds, then a stuck case on number 6.

This a more serious reliability issue than I originally thought.  The manufacturer, importer, and distributors need to step up to the plate.  I have never had this problem with older

I'm the OP in the thread about the IMI 77 gr razor core issues.  All issues occurred in a couple Colts and 4 LMT's - all 5.56, 14.5" chrome lined barrels    Temp,was in 60s and no ammo was out in direct sunlight. All were slow fire as this was zeroing new irons and optics

This is really going to piss me off. I bought a fuck ton of this ammo, to STORE AWAY, so I haven't been shooting it really. I spent A LOT OF MONEY on this ammo.....bought 20 cases......I guess I need to break some out and shoot it and see what I get.....

IMI (like ATK-Lake City Army Ammunition Plant) loads an incredible number of rounds per year.  Some lots don't pass inspection.

ATK sells the stuff as XM- and PD- ammo.  I imagine this may be IMI's way of divesting itself of SURPLUS ammo that didn't pass.

Blue-white box Independence ammo loaded by IMI using Lake City and Federal components is outrageously high-pressure and flashy.  I've seen it routinely drop primers in carbines, rifles, and M249s.

I asked that question of IMI and they say this is all first quality milspec ammo   No seconds or rejects

I read the whole thread to make sure no one had already pointed it out ,but the two fired rounds in the above picture are DEFINITELY over pressure!

See the black staining around the primer crimp?  That is gas leakage and happens JUST before the primers begin to fall out!

Federal has said otherwise about XM-labeled ammo.  On the other hand, they have also said that the XM lines are inspected to civilian standards, not GI specs.  That could mean more variation between rounds, and it almost certainly says LESS intense inspection.

When a GI ammunition lot fails inspection, my understanding is that it's already in DoD's posession.  It isn't sold as "seconds," it's demilled.

Goddamned it... Read thread title as "Prices falling out..."  

Not sure of the niceties and fine points.  While the equipment is Uncle Sam's it is run by the contractor (Government Owned - Contractor Operated, or GOCO).

Uncles Sam pays the contractor for finished product.  If it doesn't pass compliance Uncle Sam doesn't pay -- Sam's not going to be stuck with wasted components assembled into "Stuff" that doesn't meet contractually-agreed drawings and specs.

When Remington ran Lake City they used IMR and Olin powders.  When Olin ran it they used Winchester-Olin powders.  Now that ATK runs it they use ATK and General Dynamics powders.

I've been dealing with Federal on this issue with Independence IMI XM193, lot no. FC15J001-152.  Blowing primers in a 16" mid suppressed Daniel and a factory spikes (which was a very pissed off customers gun).

We sent Federal a 500rd sleeve of it, they had it for months with no contact.  I called today and was told it tests within specs, that it isn't meant for suppressed guns, and they would replace the ammo we sent for testing.  Wow.

I'm going to call IMI and see what they can do, I'm sitting on a lot of this stuff and I don't want to sell it.