300blk 7.5" sbr cycle issue

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Rewben300
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300blk 7.5" sbr cycle issue

Post by Rewben300 »

So as the title says I'm having cycle issues...i have tried to search the site and already posted topics but other I'm over looking similar issues or suck at searching. It's like it's short stroking, It will fire, eject the casing but its not going far enough back to pick up the next round. Made sure the gas block is on straight and all that good stuff, it does have a pistol length gas tube. Just curious as to what the issue could be? I've change to different BCG and trigger group...pretty much everything other than making the gas port larger and still the same issue. So that's why I was coming here to get others input to see if that is a possible reason for it to short stroke before I open it up a bit. I appreciate any help in advance
dpete
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Re: 300blk 7.5" sbr cycle issue

Post by dpete »

Are you shooting Supers or Subs and not having it function? Adjustable or fixed gas block? Whats your gas port size right now?
My 8" barrel wouldn't cycle with subs until I opened the gas port in the barrel to .108" When I add the suppressor I can dial the adjustable gas block to exacly where it needs to be for cycling either subs or supers.
Rewben300
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Re: 300blk 7.5" sbr cycle issue

Post by Rewben300 »

Supers and I do not have an adjustable gas block and I don't know the size of the gas port. I'll get that info when I get home
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dellet
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Re: 300blk 7.5" sbr cycle issue

Post by dellet »

What ammo, factory or reloads?

If reloads, complete load data is needed.

Then rifle specs. Buffer weight, carrier weight, spring length wouldn’t hurt, but not likely a rifle spring in there.

It’s not likely port size, but alignment is possible or a clog. Loose gas key can do it.

Without knowing load and rifle specs, anything is just a wild guess
300 Blackout, not just for sub-sonics.
Rewben300
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Re: 300blk 7.5" sbr cycle issue

Post by Rewben300 »

Ok and I'll get that info. They are factory rounds, and it's brand new...could it still be clogged? I do know that it's basically all milspec parts if that helps at all...sorry for the lack of info and vagueness I'm new to this
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dellet
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Re: 300blk 7.5" sbr cycle issue

Post by dellet »

Rewben300 wrote: Sun Oct 09, 2022 12:55 am Ok and I'll get that info. They are factory rounds, and it's brand new...could it still be clogged? I do know that it's basically all milspec parts if that helps at all...sorry for the lack of info and vagueness I'm new to this
Could be plugged or mis-aligned, partially or completely. Think about how many times burrs are left drilled holes. I’ve even seen a gas tube where the hole was drilled on the wrong side, or was bent the wrong direction, same result.

A burr on the gas port of the barrel can shove enough bullet off to plug a gas tube pretty quick. It’s always worth checking when there are cycling issues.

Another common issue is having a gas block that is mil-spec pushed back against the shoulder on the barrel. If the block was drilled to allow the part of a plastic military to fit between the shoulder and the block, the hole in the gas block will cover about half the port if pushed back against the shoulder.

Unless it’s a real rare occasion, it’s not the ammo. But with that said, supers, in a rifle with poorly chosen parts, can cycle so fast that the magazine can’t feed the next round. This happens when people try to solve a lack of gas problem with a drill bit. A 7.5” pistol gas barrel only needs about .080” to cycle supers and can often get by with less depending on the actual load.

Not uncommon for some barrel manufacturers to use a .120” port, that will often cause cycling too fast
300 Blackout, not just for sub-sonics.
Rewben300
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Re: 300blk 7.5" sbr cycle issue

Post by Rewben300 »

Alright, that is a ton of stuff I didn't know. I really appreciate the help and information given. I will look over everything and see where it all mounts up and check port size. Again thank you for all the information!
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