New ACR Slam fires .223 rounds

[IXLR8]

A little off topic but I can tell you that in one of my ar15s with youngMF national match expensive ass BOLT when I charge and load the weapon if I eject the shell I can see a pretty deep primer dimple and they are reinforced primers. I have not had one slam fire but it is kinda dis heartening to say the least.
I have had 2 ar-15s slam fire on me over the years and one Galil sporter do it.

The one theme that I heard over and over is to make sure the firing pin is dry. It should not have any oil or lubrication on it at all. The ACR has a return spring, but your Colt does not. Another popular fix for that, is to reduce the mass of the firing pin by using a titanium firing pin which is lighter, and less likely to strike the primer. When it does, it produces less kinetic energy due to reduced mass.

 

[AusTex]

Thanks for the info. Do you think the face that I had these on sbr lower with heavy duty spring and buffer could also increase that forward momentum?

Jeremy

 

[IXLR8]

This sounds like it should be a new thread. You will probably get more and better information in a new thread.

Being an SBR, you may try the class III forum. There are a lot of very savvy people on here.

 

[IXLR8]

Resolved

Range report:

I took the repaired ACR to the range. I tried 5 types of .223, and a few boxes of 5.56, without any problems. Today at least 200 rounds of several different types were fired without any feed problem or failure. It appears as though there was a repairable problem, and Bushmaster repaired it to my satisfaction.

I shot 3 types of Hornaday ammo, Remington, Winchester, and some surplus.

 

[MR Redneck]

They put a heavier pin return spring in it or what?

 

[IXLR8]

Repair Notes:
D101.1
D140
ADJUSTED FIRE CONTROL GROUP. BOLT HAD A SMALL CHIP BY CAM PIN. EXCHANGED BOLT ASSEMBLY AS WELL. TEST FIRED OK 90 ROUNDS WITH NO MALFUNCTION.

I did not see anything different in the BCG disassembly then before. As far as I can tell, it had a factory flaw.

 

[Texas42]

Glad you got your gun fixed. Have fun. : )

 

[AusTex]

Glad you got it fixed, glad bushmaster did what they needed to do, and glad no one was hurt!

I think people need to get the word out about this potential problem sooner rather than later!

 

[Texas1911]

Thanks for the info. Do you think the face that I had these on sbr lower with heavy duty spring and buffer could also increase that forward momentum?

Jeremy

An H1 / H2 buffer should decrease the chance of a slam fire. It's arresting the bolt more and has a slower return. It improves feeding by principle of inertia. The big buffer has a bit more punch when the bolt tries to slow down.

 

[navyguy]

I think that is good info Texas1911 offered. In my limited experience, slam fires are caused by the firing pin not being held at rest when closing the action (Inertia more than the spring can hold back). Be it a weak spring, or over aggressive buffer spring. Problems with the firing pin protruding for what ever reason not with-standing as that's a different issue). It dosen't happen too often (I've never had that condition) but it does from time to time, and another reason to always keep pointed in a safe direction when closing the bolt.

 

[bigkracka]

The bad thing is, when you get the rifle back, you'll probably have a 14# trigger and light primer strikes on every other shot.

LOL That's what I was thinking!

 

[M. Sage]

There are some other plus sides to running a heavy buffer in your AR, especially a carbine. But I'll try not to threadjack...

I think that is good info Texas1911 offered. In my limited experience, slam fires are caused by the firing pin not being held at rest when closing the action (Inertia more than the spring can hold back). Be it a weak spring, or over aggressive buffer spring. Problems with the firing pin protruding for what ever reason not with-standing as that's a different issue). It dosen't happen too often (I've never had that condition) but it does from time to time, and another reason to always keep pointed in a safe direction when closing the bolt.

I'm not sure I'm reading that right, because it sounds like you're talking about a firing pin spring in an AR.