Hey guys, I've been working on my 9mm build more lately and have a couple of problems that I'd like some recommendations on what to tweak.

Specs:
Aero Precision Lower
Spikes mag block
RRA two stage trigger (with a high round count)
KNS pins
Spikes ST-9x
CMMG ramped bolt
TROS 5" 3-lug barrel
BCM charging handle



If I'm deliberately firing single rounds I don't have a problem.  I've had great success with bumpfiring it and can get off whole magazines accurately from the shoulder. Recently, when I try to bumpfire it and hold it loosely, the hammer won't catch and will follow the bolt forward.  This does not happen all the time. It's intermittent and I don't know why. This doesn't ignite the primer on the round that was just chambered but leaves me with a live round in the chamber and the hammer forward.  

The next time I shoot it I'm going to bring a mil-spec trigger with me and swap them out and see if there are any issues. I like the RRA 2-stage because it's super easy to bump. Any recommendations on a new trigger if I need to go that route?

This leads me to my second problem. When I forcefully pull the charging handle back to eject that round and re-cock the hammer the bullet gets separated from the case and stuck in the chamber.  This leaves me with an ejected empty case (primer not touched), unburt powder all over the inside of my rifle, and me with a cleaning rod pushing the bullet out.  If I try to slowly pull the charging handle back and take my time with it, the complete round comes out and looks fine.

Could this be the inerta of the heavier bolt / buffer forcing the bullet a little out of the case upon chambering? This mostly happens with Freedom Munitions 115gr.  Maybe too light a crimp? I don't know.  

Thanks for any insight,
Tom

Are you using reloaded ammo that might not be seated deeply enough, or perhaps more likely, not crimped properly?

I dont want to sidetrack this thread or start a "crimping" debate, but I barely crimp my handloads. Usually just enough to get rid of the belling.  I believe the OP has something else going on here.  The hammer profile might be a reason why its following the bolt home sometimes.  I think its a good idea to try a different TG.  Also, it might be shortstroking.  What spring are you running?

Is your hammer notched like this one
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If so, that is most likely the problem

This profile works best with the cmmg ramped bolt


If you are doing your own reloads, try a shorter OAL, the projectile may be engaging the rifling

Mostly Freedom Munitions 115gr round nose.  I think it's their remanufactured stuff.  I'm working on going through a case of the stuff.  I have some 124gr and 147gr as well but have been waiting for my stamp to use it.  



Standard carbine buffer spring.  What do you recommend for an aftermarket buffer spring? Slash? Wolff?




This is what I have. Looks like I'm on the hunt for a new trigger

Yes, definitely try a different hammer.  I run mine 100% suppresed and I use a Slash heavy buffer(9Q-T) and Wolf XP spring.  I would leave your spring/buffer combo alone for now.   Try just swapping out the hammer and see what happens.  I also run a TROS 5" barrel and have never had a problem with extraction.  If you have some calipers, check the overall length of the ammo thats giving you problems.  Im curious to see what it is.

Update

Got a chance to go to the range after swapping the triggers out.  I took a Giessele SSA-E out of another rifle. I also got my TiRant9.


I shot about 120rds of  Freedom Munitions 115gr REMAN (trying to get through it, I won't be buying it again). I also took a 50rd box of HPA EMCON subsonic 147gr 'suppressor-specific' ammo that I wandered upon at Academy sports.

Everything shot well until I tried to bump it. It did the same thing where it would chamber a round but the hammer would be forward. When I tried to charge the weapon the bullet would stay in the throat and the case would eject with powder everywhere. You can see the bullet still in there.



The EMCON shot great and I was able to bump a whole 20rd mag without issue.  

After the third falure with the FM ammo I just packed it up and went to the house.  I took the rest of that ammo, loaded it into magazines and then just hand cycled the action and had two more failures. Giving me 5 out of 150.


I'll keep working on it and trying different kinds of ammo to see what it does.

Well, that's your problem right there... No powder.

Kidding aside, I'd hand cycle everything, and any rounds that have issues measure out to make sure they're in-spec to SAAMI, if they are, compare the measurements to ammo that cycles. You might have some tolerance overlap going on.

Well, the good news is the completed gun with can looks great! Lol

Ramped Bolt with a after market trigger might be the problem.  As the Bold ramping was a fix for the standard AR trigger your after market triggers might not reset after bump firing due to short stroking?     Just a guess


And the ammo might be underpowered since the gun is blow back maybe try an h2 buffer...    (I don't know if that will work but a guess)

I wouldn't, you run the risk of bullet setback. Possibly increasing pressure, giving one other issues.  Call FM and tell them what's happening. The should make you a happy camper.  
Now if it were me, i'd throw throw the FM rounds on the press and give them a tad more crimp then they have. That's AFTER you talk with FM. Or save the bullet & brass then use what ever pistol powder one has on hand.
I have 3 -4  mfg's of 9mm ammo. Throw a caliper on each to see OAL, you'll come up with 4 different measurements, sometimes 6 (in one box of Bulk 9)

If some are sticking in the chamber, they may be too long.   They are getting up into the rifling.   If you have a 9mm pistol, take the barrel out of it and do the plunk test.  If the case sticks up above the barrel hood, then that is the problem.

Can't read the headstamp on the one you have pictured but the one's that are empty on the table look like ammoland brass with the ridge on the inside. The bullet may not have been seated all the way due to this as they were reloads. If I am correct cull all those headstamp reloads out and see if your problem is fixed. Also I'd let Freedom Munitions know about this.