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Adjustable gas blocks? Suppressed. #15250575 09/23/20
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MtnBoomer Offline OP
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A couple uppers in the works.

16" 300 BO, pistol gas and 16" 7.62x39, carbine gas. Both are .750" and under freefloat handguards.


To operate suppressed, subsonic and supersonic, will I need adjustable gas blocks, and any recommendations, suggestions or things to avoid?


Much appreciation for anything useful to go from.


If I need to I'll make a cutout on the handguards to access the screw or whatever on the gas block. Is that a "thing" that's done? Might I need different/special buffers?


Critical thinking not needed.

BP-B2

Re: Adjustable gas blocks? Suppressed. [Re: MtnBoomer] #15250719 09/23/20
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Originally Posted by MtnBoomer
A couple uppers in the works.

16" 300 BO, pistol gas and 16" 7.62x39, carbine gas. Both are .750" and under freefloat handguards.


To operate suppressed, subsonic and supersonic, will I need adjustable gas blocks, and any recommendations, suggestions or things to avoid?


Much appreciation for anything useful to go from.


If I need to I'll make a cutout on the handguards to access the screw or whatever on the gas block. Is that a "thing" that's done? Might I need different/special buffers?


To start at the start you need to define the lowest gas situation for both uppers.

This would be subsonic/ unsuppressed unless you will always be suppressed which will be subsonic/suppresssed.

The port has to be big enough to supply enough gas as adjustable gas can't make more gas.

Light buffers and low spring rates can help when gas is weak but you still have to have enough spring energy and buffer mass drive the next round into the chamber and there is a lot of variability in subsonics and the port pressure supplied.

So start at the start and get function at the weakest gas situation with the loads you will be using (subs).

Then see if the added gas is a real problem with supers and add spring rate, buffer weight, or a gas throttle if required.


John Burns

Re: Adjustable gas blocks? Suppressed. [Re: MtnBoomer] #15250741 09/23/20
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MontanaMan Offline
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You may need it, might not, but if you have it, it will most likely help you. With carbine gas, I think you will like having the AGB.

Get an SLR, period. They are definitely not cheap but they work, have longevity, are easy to access & adjust, & are easy to take apart & clean.

The adjustment screw is on the front & you also want to buy one of their 2mm ball screwdriver adjustment tools long enough to reach it from the front of the handguard.

Use a 12" handguard, & even with a carbine gas system, you will be fine.

Carbine gas would not be my 1st choice by any means.

MM

SLR AGB's

Re: Adjustable gas blocks? Suppressed. [Re: MtnBoomer] #15250993 09/23/20
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I have 2 ARs, one in 6.8 spc with a 16" carbine gas, and one in 223 with a 16" mid length gas. I have Odin Works adjustable gas blocks on both and shoot them suppressed and unsuppressed. I have not had to make gas block adjustments switching back and forth. I got some extra long allen keys to reach the gas block from the front and keep them in the storage areas of the butt stocks in case I need them.

Last edited by scoony; 09/23/20.
Re: Adjustable gas blocks? Suppressed. [Re: MtnBoomer] #15251192 09/23/20
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MtnBoomer Offline OP
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Much appreciated guys.


Say that I decided to just go subsonic suppressed with the 300 BO, recall it is 16" with pistol length gas, all 556 generic otherwise. What would be the best first thing to try IF it doesn't run, buffer, spring or gas port?


I saw some ports that vent off, rather than restrict flow. Superlative Arms. Are those worth a chit?


Critical thinking not needed.

IC-A

Re: Adjustable gas blocks? Suppressed. [Re: MtnBoomer] #15251345 09/23/20
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MontanaMan Offline
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Well, I guess everyone has an opinion, but I'd much rather use an SLR than a Superlative; Odin is my next choice, but they can be an issue with some small ID handguards.

As to what to change 1st (w/o an AGB), again, IMO, assuming full weight M-16 BCG, then buffer first, spring 2nd (depending on where you started, I always start with Sprinco standard white or slightly enhanced blue) and gas port size change is last.

Here are some nominal gas port typical sizes.................check yours to see if it's close to something nominal. Scroll down to the 300 BO data.

MM

Typical Gas Port Sizes

Re: Adjustable gas blocks? Suppressed. [Re: MontanaMan] #15251472 09/23/20
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MtnBoomer Offline OP
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Thanks man! Appreciate it.

(Yes on the full-weight BCG)


Drawback being tuning a particular lower to this upper. I'll get an agb - maybe.

Last edited by MtnBoomer; 09/23/20.

Critical thinking not needed.

Re: Adjustable gas blocks? Suppressed. [Re: MtnBoomer] #15251563 09/23/20
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MontanaMan Offline
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It's quick & easy & not too expensive to change buffers & springs on a lower to work with different uppers.

Just sayin'.....................

MM

Re: Adjustable gas blocks? Suppressed. [Re: MtnBoomer] #15251614 09/23/20
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MtnBoomer Offline OP
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Yah. We'll see, I have the 300 stuff in hand so I better get to it. . Appreciate it and I will likely follow up. Thanks for pointing me in the right direction.


Critical thinking not needed.

Re: Adjustable gas blocks? Suppressed. [Re: MontanaMan] #15252062 09/24/20
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MtnBoomer Offline OP
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Originally Posted by MontanaMan
Well, I guess everyone has an opinion, but I'd much rather use an SLR than a Superlative; Odin is my next choice, but they can be an issue with some small ID handguards.

As to what to change 1st (w/o an AGB), again, IMO, assuming full weight M-16 BCG, then buffer first, spring 2nd (depending on where you started, I always start with Sprinco standard white or slightly enhanced blue) and gas port size change is last.

Here are some nominal gas port typical sizes.................check yours to see if it's close to something nominal. Scroll down to the 300 BO data.

MM

Typical Gas Port Sizes



Looking at that port size info, my 300 BO is .093",
listed for 16" with pistol gas are:
subsonic suppressed .086", subsonic un-suppressed .067"
supersonic suppressed .059", supersonic un-suppressed .0625"


So, likely to be over gassed, and what might be needed is: heavier buffer, heavier spring or less gas?


Critical thinking not needed.

IC-B

Re: Adjustable gas blocks? Suppressed. [Re: MtnBoomer] #15252107 09/24/20
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MontanaMan Offline
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In that case, I'd start with the AGB for sure.

MM

Re: Adjustable gas blocks? Suppressed. [Re: MontanaMan] #15252279 09/24/20
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MtnBoomer Offline OP
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Thanks again. SLR is looking good.


Critical thinking not needed.

Re: Adjustable gas blocks? Suppressed. [Re: MtnBoomer] #15254343 09/24/20
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MtnBoomer Offline OP
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Horned me up a bit more than I thought it would!


I beat it apart and back together with the 300 BO barrel and it runs. I'll get an AGB for it. It's not for everyone, Anderson lwr, PSA EPT build kit, swapped out BCA pistol upper with 7" HG, but it's paid for!

Appreciate the guys on this forum sharing their knowledge.

Shown with my Omega 300 but plan to use with an Octane when I get a 5/8-24 mount.
No louder than 22lr rifle with Win 200gr OT subs. Going to mount a 1-6 on it. Antelope? LOL
[Linked Image from i.postimg.cc]


Critical thinking not needed.


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