9mm AR trigger pin broke

[CapnMorgan]

I have a 9mm AR Semi-auto and I was just bragging to my buddy how good the trigger was. It was the best milspec I'd ever felt, just as good as his drop in. I reload, and working up a new load I ended up with some unburned powder in the fcg, I decided to just pop the hammer and trigger out to clean it and when I pushed the trigger pin only half of it came out. I replaced the pin with a dpms I had and my trigger is now normal crappy milspec quality.

The lower is an RRA lar15 with a RRA 9mm hammer and RRA 9mm mid length upper. I can't remember if I bought a complete or stripped lower so I don't know what brand the pin was.

Did I have a defective pin? Are 9mm AR's hard on the pins? The bolt isn't ramped, Will ramping it help?

 

[ferndog1]

Colt 9MM AR-15s come with stainless steel hammer and trigger pins, because the normal steel ones break.

 

[Ulwembu]

If the bolt isn't ramped it's extremely hard on the hammer pin (it tries to push the hammer back instead of down). Ramp the bolt and the risk of breaking pins is a lot less.

 

[sniperdoc]

Try polishing the new pin.

 

[MPA guy]

Not only are 9mm hard on pins, they also have a bad tendency to egg out the receiver around the pins. Especially considering it's just aluminum.

Ramp the bolt.

Heck, you may even be able to buy a ramped bolt cheaper than you can had adco or someone ramp that one with as inexpensive as parts are getting.

 

[DistalRadius]

Does he need to ramp the bolt with the RRA 9mm hammer? That hammer is the rounded type meant to work with an un-ramped bolt, will ramping it actually relieve any more stress?

Do you have a spacer in place to take up the bolt overtravel? You need one, the bolt gets a nice running start at the bolt catch without it and transfers a lot of force. You can stack quarters in the rear of your buffer tube until the bolt juuust locks back on an empty mag but no further. Also make sure you are using a 9mm buffer, not a standard one.

 

[MPA guy]

I have a 9mm hammer from RRA.

The RRA 9mm hammer actually won't work with my ramped PSA bolt. It uses a standard AR hammer.

Here are some photos from arfcom

https://www.ar15.com/forums/ar-15/PSA_9mm_Bolt_pics/15-675269/

 

[Ulwembu]

Why won't it work? Due to the slot being too narrow in the bolt? Have it milled out and it will. I had the same issue with a CMC 2-stage hammer.

 

[MPA guy]

Don't know what it won't work. I didn't spend the time diagnosing it. Regular hammer works fine.

 

[CapnMorgan]

I have the 9mm buffer, I also use a stiffer spring. I never knew to use a spacer. I'll use the quarters like you said, then machine a delrin spacer that size. Thanks

 

[Captain murrica]

Ramped bolt, regular hammer, extra power buffer spring, heavy buffer, never had a problem.

 

[secondofangle]

I think KNS antirotation pins are SS too. Other than FA, this may be an instance where they are indicated.