I installed the grip screw but removed it. I pull then wait. It doesn't usually happen immediately afterwards. More like when I start to reset the trigger.

Anyways, I decided that the slam fire problems were with my trigger. I shot the PMC Bronze ammo and had a few slam fires, so it's probably not just the Federal primers. Interestingly, I only had two slam fires out of the 100 rounds of TAC and Fed primers I shot. I plan to replace the trigger soft springs I installed with the stock springs and see if the problem goes away.

What trigger do you have installed?  Did you do any modifications? 

That will help research of anyone else has been having similar problems.  And provide information to help determine what is happening. 

What trigger do you have installed?  Did you do any modifications? 
That will help research of anyone else has been having similar problems.  And provide information to help determine what is happening.

I replaced the lower trigger with a flat trigger and replaced the trigger and hammer springs with softer ones. I'm saving my money for a drop in trigger so maybe in a couple months.

I replaced the lower trigger with a flat trigger and replaced the trigger and hammer springs with softer ones. I'm saving my money for a drop in trigger so maybe in a couple months.

You started with std USGI trigger group? Or other base trigger group?


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Standard. Suggestions?

What type of flat trigger?  May be it's not compatible with the standard sear angle or disconnecter.

Maybe stacking of tolerance, mixed with the light springs is causing the issue.

It's a cheap replacement until I save up for a real trigger assembly so could be. The slam fires started happening months after I installed the trigger. If it had started immediately, I would have swapped it back then. Perhaps the soft springs have lost their springiness. 

It's not really a slam fire if the problem is your trigger.

The RRA "NM" trigger is a good priced option and performs well. Had one for years. If you shop around you can get one for around $80.

I replaced the hammer spring with the stock spring. It's now at 3# pull. I fired 90 rounds on the 300BLK today with no problems. The trigger return feels a lot stiffer now. Thanks for everyone's help. 

I have about 300 Fed primers left then switch over to the CCI 450 primers I bought.

Just to be a little bit pedantic:
Bump fires are the result of a shooting technique, and are usually deliberate. Bump firing is a way to fire a semi-auto very rapidly, at speeds approaching that of full-auto. It's possible to have a negligent bump fire, either with a very light trigger or amazingly sloppy trigger control.
Slam fires, on the other hand, are a malfunction of the gun. Inertia drives the firing pin into the primer when the bolt closes. While people tend to associate this malfunction with guns that use floating firing pins, it can happen to pretty much any gun.

On a side note, the concept of slam fire is pretty close to how machine guns that fire from the open bolt position are designed. The "firing pin" doesn't move at all; it's welded to the front of the bolt. When the bolt closes, it ignites the round.

Good information. I agree that it's a slam fire. I kept the bump fire in the title because it was part of the discussion.

The hammer spring feels a lot more substantial now that I reinstalled the stock spring. I surmise that the heavier spring is holding the hammer back enough to prevent the firing pin from hitting the primer with enough force to set it off.

Good information. I agree that it's a slam fire. I kept the bump fire in the title because it was part of the discussion.

The hammer spring feels a lot more substantial now that I reinstalled the stock spring. I surmise that the heavier spring is holding the hammer back enough to prevent the firing pin from hitting the primer with enough force to set it off.

no the sear holds the hammer back
those trigger parts look out of the ordinary

I'm referring to when the trigger is released which pushes the disconnector off the hammer and onto the sear. There is a noticeable clunk sound unless it's the last round in the mag. With the heavier hammer spring, the "clunk" is more distinct.

https://youtu.be/xh2FjzVVIZY?t=2m9s

I appreciate the feedback. This helps me figure out what's happening in the trigger.

I'm referring to when the trigger is released which pushes the disconnector off the hammer and onto the sear. There is a noticeable clunk sound unless it's the last round in the mag. With the heavier hammer spring, the "clunk" is more distinct.

https://youtu.be/xh2FjzVVIZY?t=2m9s

I appreciate the feedback. This helps me figure out what's happening in the trigger.

i think what ren is trying to say is that you're experiencing neither a slamfire nor a bumpfire.

i think he's also trying to say that, if you were experiencing a true slamfire, then it wouldn't matter how strong of a hammer spring or trigger spring you put into your fire control group.  even the heaviest springs would not remedy a slamfire problem.

i personally think you should stop screwing with your fire control group until you have a solid understanding of the mechanics of it and how it plays with everything else in the rifle (e.g. the bolt carrier group).  if you continue to own/possess/use a firearm that occasionally fires multiple shots with the press of a trigger, you're opening yourself up to criminal liability under state and federal laws that pertain to "machine guns."

please don't interpret my post as a personal attack.  i just think it is a little unwise to document your use and possession of something that could potentially result in jail time.

i think what ren is trying to say is that you're experiencing neither a slamfire nor a bumpfire.

i think he's also trying to say that, if you were experiencing a true slamfire, then it wouldn't matter how strong of a hammer spring or trigger spring you put into your fire control group.  even the heaviest springs would not remedy a slamfire problem.

i personally think you should stop screwing with your fire control group until you have a solid understanding of the mechanics of it and how it plays with everything else in the rifle (e.g. the bolt carrier group).  if you continue to own/possess/use a firearm that occasionally fires multiple shots with the press of a trigger, you're opening yourself up to criminal liability under state and federal laws that pertain to "machine guns."

please don't interpret my post as a personal attack.  i just think it is a little unwise to document your use and possession of something that could potentially result in jail time.

Amen TFP!





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LOL, thank you for the warning. It's a good thing I didn't mention the taxes I'm cheating on.

Both are probably right that its neither a slam or bump fire. I'm hopeful the issue has been solved.

that trigger assembly looks nothing GI or anything OE
a standard GI spec trigger is heavier than 3# a GI is ~9# single stage
Where'd you get those trigger parts anyways? Did you file any surfaces? If you did - trash it and get a GI trigger assembly.
The trigger surfaces are surface hardened only. Once you break that surface the trigger material underneath is soft and will wear quickly.
Get a Geissele, Larue, Milazzo-Krieger or RRA. Proven triggers. I doubt you will find or make anything better than what Wisconsin Trigger Company or Geissele already has.
Don't reinvent the wheel because there are already solutions for your quest. Just like reloading recipes for ARs. Many shooters before you & I found proven solutions.