Good morning,
I have a BCM lower with a Geissele SSA trigger. The lower was purchased from Grant with the SSA already installed. The lower is NFA registered and setup with a 10.5” piston upper and only used suppressed. Approximately 1500 – 2000 rounds through it before last weekend. No issues at the range, typically shooting 100 -200 rounds per session.
Last weekend I took Defensive Rifle at the Sig Academy. The rifle performed well, except the Trigger Pin kept creeping out. I had to push it back in about 6 times throughout the weekend. There was enough tension on the pin that I could not push it back in or tap it back in with a piece of brass until I lowered the hammer. It would then push back into position easily with my finger.
My troubleshooting plan is to remove the trigger. I hope to borrow a set of pin gauges to check the diameter of the holes and use calipers to measure the pin. I will also confirm the trigger was correctly installed (I have not removed it yet). I expect one of those 3 things to be incorrect, identifying the problem.
I searched the forum for this issue and found some circa 2009 posts, but nothing current. Unless improper installation is to blame (I doubt it since the trigger pull is exactly like my other SSA rifle), I am wondering if KNS trapped pins would be an acceptable solution if the lower hole is too big. I thought I read somewhere that they were not recommended for the Geissele triggers.
Is my troubleshooting plan comprehensive enough? Is there something else that could cause this that I should look for? Any advice would be welcome.
A trigger pin walking out is normally caused by improper installation of the hammer spring. The legs of the hammer spring should rest on top of the trigger pin. The trigger pin should have a notch in one or both ends. The legs of the hammer spring rest in that notch and this is what keeps the trigger pin in place.
Bill Geissele has warned against the use of the KNS pins with his precision triggers. The pins provided with G triggers should be used as they are slightly over sized for a better fit and function.
Yes the trigger spring is installed incorrectly. You will need to remove the hammer altogether and reinstall it with the legs of the spring positioned on top of the trigger pin. If you’ve never done this before it can be a bit of a pain to push the hammer into position and hold it in place while lining up the hammer just right to install the hammer pin. As much as I hate to say it, it may be helpful to watch one or two videos on YouTube before you do it.
Incorrectly installed. I am not saying that Grant couldn’t have made a mistake, but it seems awfully strange to me that he would have done so. When was this lower purchased?
As it appears in the photo, not only are the legs of the hammer spring below the trigger pin, the u-bend portion of the hammer spring is positioned in front of the hammer instead of at the rear of the hammer. You’ve had over 2000+ rounds through this set up without a fail to fire? WTF! Like a Timex, it kept on firing!
ETA, After further close exam of photo, the last one, I’m mistaken. The u-bend is positioned at the rear of the hammer. The angle of the photo got me all screwed up!
One of the easiest ways I’ve found to install the hammer is to simply use your fore finger in front of the hammer and place your thumb somewhat under the tail and on the disco ledge. Press it it down and it will come very close to aligning. I start the pin by hand, press it through and realign the hammer by “twisting” it to align the other hole, tap lightly if required. It does help to spray some MAN on the parts first.
I don’t pull triggers out of lowers for cleaning, ever. So I assumed it was from G&R that way, but replying to IG made me think about when I bought it. I found my post about the Form 1. Now I believe I might have pulled it for engraving, so it was me.
I meant no offense in my post, I only mentioned Grant because in my mind that kind of ruled out improper installation…
