First time shooting SBR, some help needed

General Firearms NFA
1

Hit the range yesterday with the 10.5" SBR and AAC SDN6

Lower is a factory Colt with Geissele Super Dynamic trigger
Upper is a LMT 10.5" with a Daniel Defense BCG with a 51T Brake

Rifle shot fine unsuppressed. Mounted the can and shot one round. Trigger pin pulled out of right side of rifle, dissabled gun. Pushed it back through and shot another round, FTE. Cycled bolt manually, double feed. And trigger pin started pulling out again.

Clearly need some anti-rotation pins but whats up with the rifle FTE? Any tips would be appreciated.

I’ll be hitting the range again this week after I get the pins installed.

Side Note: Got my first taste of shooting longer range (300 yards) with a Semi 308 and I think I’m hooked. Need to get my rear in gear and finish my MATEN build.

2

I’m betting you do not have the legs of the hammer spring over the trigger pin. If you just pushed the pin back in without removing the hammer then you reinforced my last sentence. You do not need “anti rotation” pins to stop a pin from “falling out”.

3

Thanks for the tip, I’ll look into this after work.

4

Bingo. Incorrect assembly is to blame.

As for the FTE 10.5" LMTs are way over gassed if I recall. You may want to look into a heavier buffer or an A5.

Lastly, shoot the SBR at 300. No need for a 308 at such close distances.

5

I was going to get a 1-4 or 1-6x for my 14.5" and shoot that out to 300 first as I continue to work on my MATEN build.

I’ll be checking trigger assembly then messing wtih buffers and ammo to see what will run reliably.

6

I’m running an a5h4 in my LMT 10.5. Softer than shooting a 22 unsuppressed and very reliable.

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7

You recall correctly. The LMT is way over gassed. Try an H3 and blue.

8

I run an H2 in my SBR lower with either my AAC 300blk upper or my 10.5" LMT. Runs like a top with and without the can in any configuration.

9

I shoot my 8.5" LWRC SBR at 300"yards and it is surprisingly consistent . Given I am using an Aimpoint PRO I am happy with the results . That being said using my HK MR762 with Nightforce scope is almost boring now due to the consistency. It’s next to impossible to miss 12" steel with that combination . Now I am going after bowling pins foe something more challenging .

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10

First off. The pin is most likely coming out due to incorrect assembly, as already mentioned.

As for the rest. A double feed is caused by a bad magazine, it’s not a weapon issue. You fail to mention what buffer you are using. If you are shooting suppressed you should be using an H3 buffer. There is no way to know if the LMT barrel is “overgassed” without measuring the port. LMT used to make their stuff with the smaller port, however it would appear that they have opened them up and are supposed to be around .078.

The A5 is probably your best bet. If you are going to keep the current carbine receiver extension, get an H3 buffer and a blue Sprinco spring and you will be fine.

11

God has spoken.

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12

What ammo you using?

Just curious as I have a 10.5lmt and an A5 but need to order a different buffer as the BCM kit came with an A5H0…

13

m193 m855 ae223 and a few of my different reloads 55gr and 77gr