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light primer stikes

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I just fired my dpms platform ar308 today that was built by some bozo. I guess im the bozo for buying it. Anyways, I just replaced the entire buffer assembly, and I haven't been able to tighten the castle nut all the way.

But out of 20 rounds of walmart zq1 Turkish ammo, 2 hailed to fire due to light primer strikes. Do I need a heavier hammer spring, or is the headspace off? Any advice is appreciated!


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Everything has been well cleaned, and well oiled.

I am thinking I am going to give all my parts an oil bath.

All rounds that fired ejected about at the 3 o clock, and had what looked to me to be good primer strikes. Recoil was very light.

I dont know how many rounds have been fired through the rifle. I dont think the original builder put many through. I have put 20 rnds.

The ammo I am using is Turkish zq1 from walmart. $17 a box.

The two rounds that failed to fire had light primer strikes.

This is all I know. I hope it helps!

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Remember that mil surplus ammo (it doesn't matter what caliber you pick) is designed to be stored and transported in large metal ammo cans. Because of this, the mil primers are a bit thicker and stronger than a commercial primer, due to the banging around inside the cans. This is a contributing factor to why "mil spec" triggers are generally so rough and tough. Those heavier hammer springs are needed for popping the heavy duty primers.


I'll bet if you grabbed some off-the-shelf .308 commercial ammo from <insert your LGS here>, you would be absolutely fine.


If you're looking for an inexpensive trigger assembly upgrade, take a look at the ALG triggers. They are made by Geissele and designed for to be a "mil-spec" upgrade. Nothing too fancy, but you can often grab one for $35-$50 depending on the deal.

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  • 5 months later...

Your cheapest fix is get a basic ar 15 trigger kit that you like. replace trigger trigger spring and keep your hammer and replace hammer spring. The dpms units are a bit weak and long pulls. You can use a cmng I prefer the FN kits myself.

Not really, man - the real fix is to break it in with a couple hundred rounds of .308 Winchester commercial off-the-shelf ammo, with the upper receiver wet with lube, and get the function of the rifle down.  After that, move to some military 7.62x51 ammo, and have at it.


These big fuckers need to be broken in, and parts meshed.  Bearing surfaces on the BCG, inside the upper receiver, bolt lugs-to-barrel extension - all that stuff needs to be properly pounded into place, whilst wet with lube.


Hell, even magazines need to be broken in - don't go load your brand new 20-rd mag with 20 rounds, and expect perfection.  Load light in the mags, break those bastards in, too.


These things ain't AR-15s... 

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  • 5 months later...

I also have a light primer strike problem with a new dpms lr 308 upper. Started immediately today with first round as I started to break in the 24 inch stainless bull barrell. FTF because of light primer strikes every other round. Cycles fine, ejects land at about 10 feet at 2:OO  Loading by hand single hornady match 168 grain ammo. Gave up after 8 rounds. Silent capture buffer assembly. Jard #3 trigger. Prs stock. Cmmg LPK. Detroit Gunworks lower. Took it home stripped it down scrubbed everything with Ballistol lubed it up and reassembled. Try again next week. I'm gonna lube the livin bejesus out of it this time. Also JP says in their literature you might have to add a quarter as an extention in the buffer tube or a different spring which they sell. I'm hoping it's just a break in problem with the BCG and the extra lube will help.

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    How do you know your getting light primer strikes ?


     FTF   , Failure to feed or Failure to fire ?


    The rifle fires, after you hand load the cartridge in the chamber & dropped the BCG ?


    Just dropping the BCG on a cartridge in the chamber will more than likely produce an indentation on the primer .


    Follow JP"s advice or get there spring , to start out with. 


    If the BCG is not fully driven back far enough & the BC is feeding the cartridge from the magazine , instead of the Bolt , that is one circumstance that would cause FTF ( failure to feed ) & it would not be the first I have heard from that Captured Spring assembly .

Edited by survivalshop
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Good questions and points. The rifle fires sometimes when I hand load a cartridge and drop the bcg. When it does the spent primer has a nice healthy dent in it. When it dosnt fire the primer has a small shallow pin prick dent in it. Good point about the indentation on the primer from just dropping the bcg on it. Anyway I went back out today after lubing it up good and working the action about 50 times and dry firing the rifle. Big improvement in that there were a lot less of failure to fire. But I had to work the action a couple times every time before I fired it or the ft fire would start again. This is all going on as I'm following DPMS barrel break in procedure so I havent tried putting muliple rounds through it useing a magazine. That's up on the next trip out. Appreciate and value your opinion.

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