450 BM Not Cycling

B

Buckreed

Well-Known Member
Joined
Dec 27, 2017
Messages
142
Hello, I'm new to reloading for gas guns and have a 450 in an AR platform. I made about 50 reloads for it and the fist 5-10 cycled fine but none of the rest did.
Should I be looking to lower my pressure to allow the buffer spring to hold closed longer or increase pressure to make it cycle harder.
Thanks for your help.
 
I'll need to verify factory ammo. I haven't tried any since I got set up to reload. In the past only issue I had with factory ammo was running sub sonics.
I'll check my load data when I get home but it seem like 37.5 of lil gun, 250 GR horniday ftx, and crimped.
As far as brass Landing I'll need to check that with the factory ammo since these ant cycling.
 
I have a 450BM upper that didn't cycle until I put an adjustable gas block on it. Even with a suppressor seemed to consistently have problems until I opened it up. Can't remember the brand off the top of my head but it was pre-assembled. Not a choice I would have made to use a fixed block.

I bought a second (Aero) upper that came with an adjustable block and it's always worked 10/10.
 
QuietTexan said:
I have a 450BM upper that didn't cycle until I put an adjustable gas block on it. Even with a suppressor seemed to consistently have problems until I opened it up. Can't remember the brand off the top of my head but it was pre-assembled. Not a choice I would have made to use a fixed block.

I bought a second (Aero) upper that came with an adjustable block and it's always worked 10/10.
Click to expand...

An adjustable gas block only restricts, it does not allow more gas to come through. The gas port in the barrel is a fixed diameter and can only let so much gas through, which is the maximal amount an adjustable gas block could also allow.
If it seems completely undergassed, then opening up the gas port is the way to solve that issue.

For the OP - I would try increasing your charge weight to see if that helps with cycling.
 
waspocrew said:
An adjustable gas block only restricts, it does not allow more gas to come through
Click to expand...
Should have added I milled the hole as part of it, I get that's not entirely clear as a part of making the change to an adjustable block - that's what the "opening it up" bit was about. I don't recall what the original port size was, other than smaller than a (IRRC) 0.125" end mill. Might have been a 0.096, or that might have been what passed to align it.

If I pulled the Aero I would bet cash money it had a larger port to start with. Something good manufacturers seem to care about, not something you get in cheaper barrels.
 
Last edited:
waspocrew said:
An adjustable gas block only restricts, it does not allow more gas to come through. The gas port in the barrel is a fixed diameter and can only let so much gas through, which is the maximal amount an adjustable gas block could also allow.
If it seems completely undergassed, then opening up the gas port is the way to solve that issue.

For the OP - I would try increasing your charge weight to see if that helps with cycling.
Click to expand...
depends on the hole size! i would say most are oversized for ensured ejection and feeding, but some are undersized and opening the block out all the way won't help (many variables dependent on that also).
 
did you have time to check ejection pattern?

after that it'll give more info on what to do or check for next (ie, increase buffer weight or decrease it, check the mag for issues and so on)
 
Buckreed said:
Hello, I'm new to reloading for gas guns and have a 450 in an AR platform. I made about 50 reloads for it and the fist 5-10 cycled fine but none of the rest did.
Should I be looking to lower my pressure to allow the buffer spring to hold closed longer or increase pressure to make it cycle harder.
Thanks for your help.
Click to expand...
not knocking your reloading skills, but how long (sometimes reloaders with years experience including me have came across issues) have you been reloading and/or your process?
 

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