DPMS LR 308 Slam Fire

P

PaPa 260

New member
I thought I would pass along what happened yesterday during load testing with a DPMS LR 308. I was firing single shot off the bench doing load development. I placed a round in the rifle, pushed it into the chamber with my finger, and pushed the bolt release. It fired, scared the chit out of me.

I was using Lake City match brass that had been totally prepped, to include primer pocket uniforming. The primers were all below flush. My finger was nowhere near the trigger. The primer was a Federal 210M. The load was 44.5 gr. of Varget behind a 155 Hornady AMax.

I called DPMS about it and got the answer I was expecting, "we don't recommend the use of reloads in our rifles". So I called a very experienced service rifle shooter, and gunsmith. His first words were, you were using Federal 210M's weren't you? He said use either CCI or WLR and that won't happen.

Has any one else had this happen while shoot an AR 10 style of rifle?

PaPa 260
 
Last edited:
I've heard the same thing about Winchester primers. In my opinion it can't be nailed down to a single manufacture. A weapon with a floating firing pin has to be used in extreme caution. Accidents happen and thats why we always practice proper gun safety!
 
It could be that the primer was a little bit high in the seating process....It happens. The Fed. 210M's may be a little easier to punch too.
It helps to clean the bolt as well. Powder build-up in the firing pin hole may cause more resistance if the pin is in the forward position.
 
I was told to use either wlr or the or the cci's by a really good friend that has shot and reloaded for an ar10 for yrs the only time he had problems was when he used federal primers. I have not had one single issue using wlr primers.
 
I had a slam fire on a 6.8 SPC. I don't recall the primer,
but I did find a site that calls out primer cup thickness,
and the primer was one of the thinner material primers. I
have switched to Winchester primers, for AR-15s, and have not
had an issue since. But I always keep my muzzle pointed in
a safe direction, and only charge the firearm when I am
some place a slam fire won't freak any one out...Including me.
scared.gif


I have had slam fires on SKS, and other AR-15, rifles loaded
with commercial ammo, too. Always obey the rules of firearms
safety!

Squeeze
 
Originally Posted By: SqueezeI had a slam fire on a 6.8 SPC. I don't recall the primer,
but I did find a site that calls out primer cup thickness,
and the primer was one of the thinner material primers. I
have switched to Winchester primers, for AR-15s, and have not
had an issue since. But I always keep my muzzle pointed in
a safe direction, and only charge the firearm when I am
some place a slam fire won't freak any one out...Including me.
scared.gif


I have had slam fires on SKS, and other AR-15, rifles loaded
with commercial ammo, too. Always obey the rules of firearms
safety!

Squeeze

This the one?

www.jamescalhoon.com

on left side, scroll down to "informative articles" click on that and scroll down to the article "primers and pressure".
 
I was told or read somewhere a while back (several years ago) that the AR 10 platform used a spring on the firing pin to help prevent slam fires. Was I informed wrong, or is it on the armalite rifles and not the dpms based platforms? I realize this may not have prevented your situation. Also not intended to hijack your thread either.
 
Loading an AR single shot like you were doing can cause a slam fire also.The small amout of resistance of the bolt stripping a case from the mag supposedly keeps this from happening,or was designed to not be an issue anyway.I will have to do some looking to find it in print again,but I think it was in the Speer #13 reloading manual.
 
Well I checked the Speer manual and its not in there.When I got my AR I was reading alot on firing out of battery and which primers to use ect. so it must have been on the web somewhere.Google Single shot loading an AR,its out there.You could also do a test and see if the primers look any different mag fed or single load in the chamber.
 
Originally Posted By: mikeygLoading an AR single shot like you were doing can cause a slam fire also.The small amout of resistance of the bolt stripping a case from the mag supposedly keeps this from happening,or was designed to not be an issue anyway.I will have to do some looking to find it in print again,but I think it was in the Speer #13 reloading manual.

I was thinking the same thing but figured I'd get flamed for it... I know I have read that but can't remember where. Probably part of the reason they make a single shot follower.
 
Ar type rifles can always have a slam fire happen,can be caused buy dirty firing pin,broken firing pin ect.I don't think it happens often but it happens.In this case it may have happened because it was not taking the cartridge from the mag which makes the bolt slam harder as you know.It is good to bring this up now and then because it happens rarely but it can happen anytime.It is not only Ar's that this can happen to,I have known M1's to do it also.As MPFD said that is one reason for single shot follower.Good post,many new AR owners now that might not know this.
 
Originally Posted By: MPFDOriginally Posted By: mikeygLoading an AR single shot like you were doing can cause a slam fire also.The small amout of resistance of the bolt stripping a case from the mag supposedly keeps this from happening,or was designed to not be an issue anyway.I will have to do some looking to find it in print again,but I think it was in the Speer #13 reloading manual.

I was thinking the same thing but figured I'd get flamed for it... I know I have read that but can't remember where. Probably part of the reason they make a single shot follower. Thanks for letting me take the flame this time!!!!
 
Originally Posted By: mikeygThanks for letting me take the flame this time!!!!

Aww come on, you got off pretty easy and I was right here to back you up...
tongue.gif
 
Did you have a mag in the mag well?

The rifle was not made to be loaded the way you were loading it. I suspect if you shoot your same reloads fed through the magazine you won;t have any problems.

There is much more moving mass and inertia in the larger LR308/AR10 platform.
 
I appreciate all the responses. Yes the mag was in the rifle. It is the Armalite AR 10 rifles that have the spring to cure this problem. I have found that out since this happened to me. I did some testing today using the CCI BR-2 primer in resized brass that was not loaded and compared it to the 210M in resized brass that was not loaded. The CCI was not dented as deep by the firing pin when the bolt slammed shut.

The smith I talked to about this told me if it is single loaded it has a better chance of slam firing vs. being fired using a loaded magazine. Especially with the 210M primer. He said the same thing is true of the M1A. For the same reason he didn't use the 210M in it when he shot the M1A in service rifle competition. As stated there is a lot more moving mass in the AR 10/LR 308/M1A as compared to the AR 15 platform.

I cleaned the rifle each time I shot and I always clean the bolt face as well the B/C group.

Again thanks for all the responses. I learned something in working this rifle. I have reloaded for over 40 years now and am still learning. Luckily I learned on my range with the rifle on a bench pointed at my berm, and that is where the bullet struck. Still scared the chit out of me.

PaPa 260
 
Back
Top