So i just put together my AR308, first one i've done and i have an issue thus far, and no i don't have pictures, as usual i forgot to take them.

every 2-3 shots i'd have a spent primer in the chamber that prevents the bolt from seating and causes issues.  I've searched the internet and i've seen 3 things come up commonly as people saying it is the issue
1) headspace (honestly haven't checked that, working on getting some loaners to help trouble shoot)
2) bolt/ firing pin issue; maybe the FP goes too far beyond the bolt causing a gap for expansion (i emailed KAK to discuss with them, we'll see what they say)
3) Adjustable gas block issues (yes i have a black rain adjustable gas block, first one i've ever used, and i didn't do any adjusting because of the primer issues i was having, and besides that it functioned well enough to not futz with yet, cycled reliably, locked back when empty.)

So if you have any advice let me know, especially about how #3 could cause this and if its over/under powered or whatnot, because if it is the issue i hope i can just tune it and be good.  but until then i'll be working on ruling out #1 and #2.

thanks for the help

Are you using factory ammo?  If so what ammo?  I had this same problem with "factory" ammo that was some off brand I never heard of but purchased at the range... My loads had no problems at all, and I've had no problems with good factory ammo.

I would not even think of firing a 308 weapon that the headspace had not been checked on.
Excessive FP protrusion results in pierced primers.
There is a lot more powder in a 308 round than a 5.56mm round and KB’s with 5.56mm ammo have been known to tear things up pretty good.
I would check the headspace and try 7.62 NATO ammo with crimped primers.
7.62 NATO ammo cases are thicker than 308 WIN cases.
There is some overlap in the headspace specs, but for compatibility with both keep the headspace under 1.638”.
There is a FAC on 308/7.62 headspace on the Fulton Armory website you should read.

What load is being used? - list all components

What CASE GAGE are you using to confirm the correct base-to-shoulder dimension on your resized brass?

shame on me for coming in half cocked, and sorry but i wont be able to answer all the questions

WEG - i'm not loading my own, have a lot of bulk ammo that was handed down from my dad, best I can say is it is lake city with the cross stamp LC 02; there is some other random stuff in there so again, shame on me for not being more precise, but i'll learn (hopefully)

PFC - thanks for that resource, i'll check into that (fulton armory) and do some research there before i move forward


as far as a list of the components

AERO M5 paired upper/lower with aero LPK, w/ CMMC 2 stage trigger
KAK heavy buffer and spring
KAK complete BCG w/ double ejector
mega maten 16" barrel

so thats what i've got.  looks like i'll read up on fulton, check the headspace and go from there.

Sounds like BAD AMMO.

Try the gun again with known good ammo.

Old school M1-A competitors routinely loaded 41.5 grains of IMR-4895 in Lake City brass when using 168 grain Sierra Match Kings. This "standard" load is 1.0 full grain over maximum. If Dad substituted H4895 instead of IMR-4895 with these components his ammo is loaded 1.5 grains over maximum.

Many M1-A rifles were chambered for 7.62x51mm NATO which lowers pressures when compared to standard .308 chambers. What may have been fine in his rifle is not in yours. But you know that already. Don't shoot that ammo in that rifle.

My current general purpose 168 grain loads using IMI or Lake City brass are:

41.0 grains of IMR-4064
40.0 grains of IMR-4895
42.0 grains of VihtaVuori N150

They all achieve just under 2500 fps from my Super Match M1-A's and have been 100% reliable and safe from my AR10's and bolt actions. Each of these loads are within .5 grain of maximum when using Lake City brass. They run between 2550 and 2575 fps from 24" bolt actions.

Lake City brass will not tolerate powder charges normally associated with Lapua or Winchester commercial cases. The standard rule-of-thumb is to reduce powder charges 2.0 whole grains when using this brass.

yea when assembling I was aware of the two types, I made sure all the parts fit DPMS pattern. so at least i got that right.

I have seen blown primers from AR's that are shot with excess oil in the chamber. Make sure you dry the chamber out before use.

So it was the first time I shot the rifle so I did lube it up pretty well.  I really dont thin I put TOO much (never thought that'd be a thing!) but really i dont think it was too much, but who knows.  next time i'll use a bit less and hopefully that helps.

thanks for the tip

You can run the bolt carrier wet just make sure the chamber, barrel and bolt face are dry. I run a dry chamber mop to soak up any excess oil there and dry patches down the barrel prior to a range trip.