problems with 5.56 Prvi Partizan 55gr. M-193 FMJ Ammo

[jmart]

Take some fired cases and some new cartridges into a nearby gun shop and ask if they'll let you measure a couple of cases just above the extractor groove, at the solid head location. Use a micrometer, and if you're not familar with them, ask for help from someone who is. The catridges should measure several ten thousandths smaller than your empties.

Or, if they have a solid headspace guage tool (Dillon, Wilson, but typically nobody carries these), ask them if you can drop a couple of your cartridges in those. They should drop all the way in and not hang up. If they do hang up you probably have ammo that's out of spec. If they don't hang up, you might have a tight chamber or a tight neck/leade area.

But given that you're shooting: (a) a LMT (which is good qulaity), and (b) other ammo works fine, I suspect you have an ammo problem.

[Shihan]

Gents,

I just bought my first M4, YAY! I built it on a stag lower, with a LMT 14.5" upper and a LMT BCG. My blaster shoots great and I haven't had any malfunctions with it yet, to date I've probably put 500 rds through it. I have no problem shooting green tip, or the cheap remington .223 ammo from walmart, or Prvi ammo for that matter. The problem though is manually extracting the Prvi rounds.

I can easily manually eject all the other rounds except the Prvi ones and I have no idea why. I can pull the handle out about a 1/2 inch and then it gets stuck and at times I have to collapse the buttstock and bang it into the ground to eject the round. The actual rounds shoots fine and cycles fine but I just can't manually eject it easily. Its almost as if the bolt lugs and the star chamber lugs are catching on eachother somehow, but cycling the action unloaded and with any other ammo is smooth. What is wrong? I've read great things about Prvi ammo on this board but is it possible that the case rim is just a little thicker or larger than normal brass and is forcing the extractor to lock against one of the star chamber lugs when I am trying to unload it? anyone have any idea what the problem is or what I should do? I also noticed that I've got quite a bit of brass shavings on my bolt face after shooting so I suspect my extractor is kind of sharp. No problems ejecting during firing though.

Its not a huge deal but it is annoying for unloading after I'm done shooting and if I was ever in a match or real shooting and I get a hard primer on a round I'd like to be able to do SPORTS without problems. Thanks in advance for your help.

CZ

Whats the head stamp year?

[coldzero4545]

Whats the head stamp year?

07

Before I start, thank you all for our input and help. I have really appreciated all the help thus far...

As an update: I just tried the ammo that I have in my buddy's bushmaster M4, it cycled with no problem, a little "rough", but but little I mean barely noticeable. Nothing at all like the hang ups I get. I also tried putting his BM bolt in my LMT and no difference on my end, hangs up just the same. THoughts? I'm thinking that I have a slightly "tight" chamber (if thats the proper description, not sure of the technical term) and the prvi ammo may be a little thick. I haven't gotten to the gun shop yet to measure the difference but thats on my list of things to do tomorrow if work allows. Fortunately I don't have any problems with other ammo to date? any postulations as to why?

Anyway until then please keep the comments coming. I really really want to be able to shoot Prvi ammo because of the price so HELP!

BTW, while we're talking about ammo, do any of you know of a "cheaper" alternative to .75 gr TAP practice rounds that closely mimics the trajectory of .75 gr TAP? Thanks in advance!

CZ

[RogerinTPA]

Never had a problem with the 07 Privi ammo. It shoots great in my ARs (4k round count). Maybe you just got a bad lot? It happens...

[Shihan]

Never had a problem with the 07 Privi ammo. It shoots great in my ARs (4k round count). Maybe you just got a bad lot? It happens...

Good point.

Sub Z what lot numbers did it come out of?

[markm]

Never had a problem with the 07 Privi ammo. It shoots great in my ARs (4k round count). Maybe you just got a bad lot? It happens...

Are you talking about the M193 though? It seems that stuff is pretty good, but the M855 knock off is what's getting several complaints on the gun boards recently.

[RogerinTPA]

Are you talking about the M193 though? It seems that stuff is pretty good, but the M855 knock off is what's getting several complaints on the gun boards recently.

Yup..M193.

[dzhitshard]

I've got a fair amount of recent production Privi 55gr & the thing that likens it most to M193 was the sales ad.

It sounds to me like your experiencing some tolerance stacking if the ammo chambers in your buds rifle but sticks in yours yet you are running fine with other factory loads in your LMT.
I've seen more than one LMT that chamber reaming didn't hurt.
good luck

[coldzero4545]

I've got a fair amount of recent production Privi 55gr & the thing that likens it most to M193 was the sales ad.

It sounds to me like your experiencing some tolerance stacking if the ammo chambers in your buds rifle but sticks in yours yet you are running fine with other factory loads in your LMT.
I've seen more than one LMT that chamber reaming didn't hurt.
good luck

What is tolerance stacking? I haven't gotten a chance to measure the ammo, or to take a look at the lot number, I threw away the boxes of all my old ammo because I loaded them all. I'll get back to you guys on that.

So what is the consensus? is it my chamber? or the ammo? what do I need to do to shoot prvi ammo? should I contact LMT? I really hate having to take my rifle apart to send them the upper. Oh well...thoughts?

I'm thinking of buying some .75 gr TAP for HD and 55 gr wolf for practice any predictions as to whether these two loads will work before I go order it off the internet?

Thanks again for your help!

CZ

[jmart]

What is tolerance stacking?

Bad luck. Chamber is within manufacturing/specification tolerance, but it is on the tight/small end of the spec. Ammunition is within manufacturing/specification tolerance, but it is on the large end of the spec. A "biggish" cartridge in a "smallish" chamber, and you get what you are getting.

So what is the consensus? is it my chamber? or the ammo? what do I need to do to shoot prvi ammo? should I contact LMT? I really hate having to take my rifle apart to send them the upper. Oh well...thoughts?

If you have other ammo that chambers and extracts reliably, then you could relegate the Prvi to another carbine. But if you want to shoot that in your LMT, then you need to figure out if the problem is insufficient headspace (i.e., a jam fit), too tight of a body, or if the problem is a tight throat. If headspace or body dimensions is the issue, I'd send it back to LMT. If tight throat, then either send it back or have someone who has one of Ned's Throat Reamers have a go at it. Since you said you were getting marks on the bullet, I'm more inclined to believe it's a throat problem than a HS problem.

I'm thinking of buying some .75 gr TAP for HD and 55 gr wolf for practice any predictions as to whether these two loads will work before I go order it off the internet?

No idea. there's no way anyone on this board can answer this with any degree of accuracy w/o knowing dimensions of what you're dealing with. But if you knew those dimendaions, you wouldn't need to ask.

Thanks again for your help!

CZ

Not really sure we were much of a help.