Recently I purchased a BCM 11.5 BFH upper, loved it, and decided to go ahead and installed a mount for my M4 2000. I tried it out tonight and it would fire one round, chamber a live round, and fail to fire.
I’m also running a H3 buffer. Any suggestions?
What type of ammo are you using. Did you build the lower or is it factory built?
If the round is chambered and the hammer falls when the trigger is pulled, how is it failing to fire? Is there an indent on the primer?
Sorry, I forgot to list the ammo. It’s Wal Mart Federal .223 value pack. I did build the lower. It’s a Spikes with a Geissiele 3gun trigger.
The chambered rounds do have dimpled primers but I think that’s just from being chambered. The hammer doesn’t fall. I don’t think it’s being cocked. I was thinking maybe the bcg wasn’t traveling fat enough to cocktail the hammer, but if it was short stroking would it still strip a round from the mag?
If it strips a new round the bcg is going far enough to cock the hammer. I don’t know anything about that trigger, are you sure you installed it correctly?
Yes, it’s correct. It’s Geissiele’s single stage trigger. I’ve got thousands of rounds on it. It’s my only SBR’d lower so I switch it between uppers.
I also need to mention that it’s run flawlessly until I tried it out with the suppressor
Lets see if i have this straight. You fire a round, the bolt cycles, ejecting the spent case and strips a fresh round from the mag then chambers the round.
When you pull the trigger on the following shot you get nothing, no click, just a dead trigger.
Does the hammer follow the bolt carrier as it moves back into battery?
Does it do the same thing when you do a function check?
If you remove the can, does it work again?
I had the identical problem with my sbr and the SD3G trigger while shooting suppressed. Geissele recommended switching to the heavier hammer spring. I did not want a heavier trigger pull, so I switched triggers.
This happened with my bcm 11.5 and also my dd 10.3 upper, but only when using the suppressor.
P.s. my suppressor is a m4-2000 also.
Did they say why this would fix the issue?
Is this something inherent with the SD3G trigger?
I think you are inadvertently bump firing, but the hammer is following faster than the bolt is locking up so it doesn’t fire.
It would slow the hammer down as it travelled rearward. Geissele’s thought was that the sbr with can was making the recoil impulse so fast that the hammer was not engaging the sear and then would follow the bolt forward.
I refused to mess with the feel of the trigger, but experimented with various buffer weights and springs. I never found a combination that would work. This problem did not happen to me with every squeeze of the trigger, I would have the problem maybe 1 out of 10 rds and then sometimes more.
The sd3g is different from the s3g trigger only in that it has a flat face. All internals are the same.
Thats kind of what i was thinking. The hammer is outrunning the disconnector and following the bcg back into battery.
not adding a thing, just saying I love this forum for issues like this
I recently sbr’d another lower. I purchased another sd3g trigger. They now come with the standard hammer spring and the heavier one as well. I have installed the heavier spring. I do not care for the feel of the trigger as much with the heavier spring.
I have not shot suppressed with this lower yet. I will try to do that this weekend and report back.
Yes, this is exactly what happens. There are no problems when I do a function check or when the suppressor is taken off.
What is the difference in the feel? A lot heavier? Not as crisp?
Heavier. Which, in my opinion goes against the biggest thing that this trigger has going for it.
That’s true. That’s why I love the trigger, but I might have to try a heavier spring to get my gun running with a suppressor. It works fine with my 14.5, just not the 11.5.