Bolt stop keeps bending

[izzy]

I built a QC10 SBR chambered in .45. The combination of the bolt, buffer spring and buffer that I had to use to get the rifle to cycle properly ended up being pretty heavy. Now I can take the rifle out about two times before the bolt catch ends up a little bent. After it bends the rifle still works but there will be no last round hold open nor can I lock the bolt back by hand. I've replaced the bolt catch three times now and it's getting pretty annoying. Someone at a gun shop mentioned a company that makes a "tough" bolt catch just for this type of thing. Of course I'm an idiot and I forgot the name of the company and can't find it by searching. Does anyone know where I can get a part that will solve this issue? Is there another solution?


edit: it's a "bolt catch" not a "bolt stop"

[gta_spec]

How much over travel does your bolt have passed the bolt catch? You can stack quarters in your buffer tube to limit this to 3/8 to 1/2". I have used 5 to 7 quarters in other blow back AR designs.

[izzy]

Okay so I'm a little inexperienced here I guess. I don't really know what you mean by over travel. How do I measure this?

[Great-Kazoo]

Okay so I'm a little inexperienced here I guess. I don't really know what you mean by over travel. How do I measure this?

Pull bolt back till it stops. Look at the position of the bolt to BHO /bolt stop.

[gta_spec]

If your bolt has a lot of over travel it's going to have the room to pick up speed before it gets stopped by the bolt catch. The shorter this distance, from end of travel to bolt catch, the lower speed the bolt will be traveling at before being stopped by the catch and dumping it's energy into the catch, eventually bending it or worse. You only need a half inch or so of over travel. Maybe less.

[izzy]

Hadn't had a chance to check until the other day but I do have quite a bit of over travel in this setup. I've yet to measure exactly how much but it feels like it's more than half an inch. As soon as I can get my hands on a new bolt catch I'll start trying to work on a solution. Thanks for all the advice.

[hobowh]

I know it doesn't fix the actual issue but HVA makes a bolt catch that is milled stainless might be worth a try

[meatman]

The first time I shot my QC10 45ACP 8.5 barrel pistol setup, I broke the bolt catch in half and the proprietary spring went missing. I emailed QC10 about it and they asked what buffer I was using because a "too-light" of a buffer could cause the issue because of the bolt reciprocating at excessive speed. I told him I was using the Kaw Valley 10oz buffer with the Kaw Valley 308/pistol caliber carbine spring. He said that should be a good setup and I may have had a defective bolt catch (it broke at the pivot).

They sent me a new spring bolt catch spring for free and I didn't have any issues with it bending or breaking. But re-reading your original post, you said the every two times... so I have yet to see.

[whitewalrus]

I had this problem in a suppressed 5.56 SBR, I threw in a heavier buffer and threw in a Colt bolt catch. The BCM parts also seem to be a lot more heavy duty than the the standard MIM kits that everyone else makes.

As others have mentioned, its normally that the bolt has too much energy when it comes foward...so either slowing it down or stopping it from going so far back will typically resolve the issue.

[izzy]

I ended up ordering a steel bolt catch and and adjustable buffer assembly. I'll be able to tune the weight buffer and hopefully be able to slow things down. Still trying to figure out how I want to mitigate the over travel.

[DenverGP]

seems like a steel bolt catch will just cause the steel catch to bend/deform the aluminum lower.

[Great-Kazoo]

I ended up ordering a steel bolt catch and and adjustable buffer assembly. I'll be able to tune the weight buffer and hopefully be able to slow things down. Still trying to figure out how I want to mitigate the over travel.

Spacer inside buffer tube, issue solved . I cut mine to fit inside the buffer spring so i'm not changing the OAL of spring travel.

[MarkCO]

Delrin spacer. Cut your own from blank stock or buy one from Brownells.

[izzy]

I've gotten all the modifications done here that have been suggested. Thanks to everyone for the input. I've just got to get the time to test fire it at this point.