Is An Adjustable Gas Block Important?

Talk about the AR15 style rifles chambered in 450 Bushmaster.

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Is An Adjustable Gas Block Important?

Postby whitekayak » Tue Nov 21, 2017 11:31 am

I started my first AR build in 450b for hunting white tail deer here in Ohio. This will end up being more expensive than purchasing a complete rifle but I want the experience of building an AR. That being said I would like some input from you 450B shooters.

I have searched the forum and read about multiple feeding and ejection issues with this cartridge. How important is an adjustable gas block with the 450b? Are you shooters using an adjustable gas block to solve these issues? The reason I ask is I’m looking to purchase a semi bull barrel from Columbia River Arms/Black Hole Weaponry and running an Aero Precision Atlas S-One handguard. This barrel/handguard combo limits my selection of gas blocks dramatically and I am yet to find an adjustable gas block that would fit. I’m building a dedicated lower so my hope is to be able to solve feeding and ejection issues with buffers and spring swapping. Would you guys worry about limiting yourself to a non-adjustable standard .875” low profile gas block with the 450b?

Below is my preliminary build if it helps:

Lower - Aero Precision M4E1
Lower Parts Kit – Geissele
Trigger – Geissele GS2 Enhanced
Buffer Tube – Rifle Length Tube and spring
Buffer – CTS Engineering Rifle Aktive Recoil Buffer
Stock – Luth AR-LLC AR-15 Modular Stock Assembly Fixed Rifle Length
Grip- Ergo AR-15 Super Grip
Upper- Assembled Aero Precision 458 SOCOM
Hand Guard – 15” Aero Precision Atlas S-One
Bolt Carrier – undecided
Bolt Assembly – Windham Weaponry 450 bolt assembly
Barrel – Columbia River Arms/Black Hole Weaponry 18” semi bull profile 1 and 18” twist rate with Mid Length Gas System
Gas Block – Sadlak Industries .875” low profile gas block
Muzzle Device – undecided
Last edited by whitekayak on Tue Nov 21, 2017 3:21 pm, edited 1 time in total.
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Re: Is An Adjustable Gas Block Important?

Postby Hoot » Tue Nov 21, 2017 2:47 pm

whitekayak wrote:snip.... Would you guys worry about limiting yourself to a non-adjustable standard .875” low profile gas block with the 450b?
...snip


Welcome Aboard OM!

You should not need an adjustable gas block for two or more reasons. Gas issues are less of a challenge with a mid-length system than with a carbine length and I'm sure that Black Hole Weaponry determined the right size of the gas sample port without using an adjustable gas block. The only variable in the equation is your choice of buffer, as I'm unfamiliar with the CTS Engineering Rifle Aktive Recoil Buffer . The buffer can impact extraction/ejection performance. If I were you, I'd ask BHW what buffer they used to develop the barrel.

I look forward to reading about your experience with the 450b once you get it on the road.

Hoot
In Theory, there is no difference between theory and practice. In Practice, there is.
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Re: Is An Adjustable Gas Block Important?

Postby Bmt85 » Tue Nov 21, 2017 9:54 pm

This is my opinion, so take for what it is.

I’d say forget about the CTS buffer, it looks like it’s made to reduce felt recoil, rather than slow down cycling.

BHW makes some nice barrels, I ordered a 450B 20”, rifle gas, semi bull, that’s waiting to be built. Also ordered a 12.5”, carbine gas, bull recently because of their current sale. They offer a lot of options, and have a lot of happy customers to not know what they’re doing. With that said, if your looking to slow down unlocking, an adjustable gas block will work, but like you have found, the adjustable gas blocks start needing more room under the handguard. I have found one handguard that should work for you. Strike Industries Megafin XL handguard has an i.d. of 1.51”. It should at least fit an SLR Sentry has block. Now, another way you could go, is run a lo-pro gas block, and if needed, add weight to recoil system. That way you can run any handguard you want and still be able to tune, so to speak. You can run an H, H2, H3 buffer and see where that gets you, then if need be you can run something like Slash’s XH. I currently run 2 of them, one of which is in a build with a Tromix 18” mid gas barrel. No issues so far. Reason I ran it was because I was using the lower that had it in it while I was building the current one it’s on. Figured I would see what happens, didn’t see any issues, so kept with it.

One thing I would stay away from, is Extra Power buffet springs. They have way too much force when loading, could cause issues
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Re: Is An Adjustable Gas Block Important?

Postby Buckeye45 » Wed Nov 22, 2017 10:31 am

I put an Odinworks adjustable gas block on a dead shot mid gas barrel and it works very nicely. With the gas block you can skip all the trial and error with springs and buffer weights. That alone saves money and lots of wasted ammo. Mine is easy on the brass, and ejection keeps it in the same county. If you are spending good money on quality parts look around at other rails. I like the ALG line and they allow for adjustable blocks. They are thin and solid.
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Re: Is An Adjustable Gas Block Important?

Postby sbrGrendel » Sat Nov 25, 2017 10:49 am

If your also going to suppress your build down the road get a adjustable Gas Block, if your going to mess with spring weighs and buffers. It is easier to use adjustable GB to tune it, since they can make your rifle a little finicky when it comes to throwing brass and BHO.
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Re: Is An Adjustable Gas Block Important?

Postby buckeye3405 » Tue Nov 28, 2017 1:49 pm

I have the standard 16" Bushy upper on a custom built lower receiver. I shoot Hornady factory 250gr FTX. I have not had any problems with malfunctions, in very limited rounds, admittedly. I believe most feeding problems seem to be associated with magazines. I ordered two Bartz 5 round magazines upon completion of my build and it was the smartest move I made. Quality magazines made for the 450BM from the ground up.
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