Adjustable gas block under a Geissele MK8. What do I want?

[Live2Gun]

I will read up on it. I like the looks of it. Do you happen to know for sure if it will fit under the Geissele rail?

Yes the SLR will fit under the Geissele rails.

In response to the poster who mentioned the Gov'nah. I think the Gov'nah will only fit if it's the 2 position plate. IIRC the 3 position hits the rail. I went with the ALG EMR V3 for use with a 3 plate Gov'nah.

[WS6]

I am working on a new build based around a Larue Stealth 14.5" barrel that I will have pinned and welded to avoid NFA stuff. The rail will be a 13" Geissele MK8 and I want to have an adjustable gas block to tune the recoil. The gun is going to be used for competition shooting and is currently running unsuppressed. I have no experience with adjustable blocks and don't want to buy a stinker that will be stuck on a pinned/welded barrel. So what would you put on there?

First off...how large is the gas port? A properly ported barrel will so no real benefit from an adjustable gas-block. For example, here is one of my friends shooting his BCM rifle with my Surefire 556-212 suppressor. Exactly what could be gained with an adjustable gas block beyond creating more failure points in the system? A 14.5" midlength gas system barrel of 0.750" journal OD should have a port between 0.073 to 0.077 for optimal function, IME.

[WS6]

I would seriously reconsider the pin and weld, especially if you are unsure about the gas block.

Do you have other reasons besides configuration uncertainty for re-considering a pin and weld? For example, if someone is married to a suppressor, they likely won't be swapping MD's. Is a pin/weld in this case a functional negative?

[Atticus_1354]

First off...how large is the gas port? A properly ported barrel will so no real benefit from an adjustable gas-block. For example, here is one of my friends shooting his BCM rifle with my Surefire 556-212 suppressor. Exactly what could be gained with an adjustable gas block beyond creating more failure points in the system? A 14.5" midlength gas system barrel of 0.750" journal OD should have a port between 0.073 to 0.077 for optimal function, IME.

Larue has notoriously large gas ports and while I don't have this barrel in hand I would be very surprised if it wasn't on this barrel. An adjustable gas block allows you to tune the gas needed to the system. You claim a range of acceptable sizes and that may work well, but everything from the temperature to the ammo used will change the amount of gas flowing through the barrel. Add in factors like the amount of lube, suppressors, spring strength and buffer weight you get a range of acceptable gas for proper function. Having an adjustable gas block lets you narrow that range to one where the gun runs smoothly and reliably. Have you shot a rifle tuned with an adjustable gas block? I recommend you try it.

This rifle build is being built for a specific purpose of being used in Run N Gun competitions. Maybe I would buy different components if I was dropping in to a jungle at night and my life depended on it, or if I thought I would need to defend myself with it in my house. But I am building it for what is at the end of the day a game I like to play. If this gun should prove unreliable I will compete with another upper while I sort this one out. And if I do end up with a problem during a competition my life is not on the line so the benefits outweigh the potential downside for me.

[tom12.7]

Do you already have this barrel and rail? Are you dedicated to those, or would you be willing to try other options?

[Atticus_1354]

I have both and am happy with both. What are you suggesting?

[tom12.7]

As you stated, the porting for that barrel isn't optimal. I certainly know that registering another lower and paying the tax and wait time isn't an investment that a lot want to do in a "fun gun".
We do not know what can or possible ammo is in the mix, and those are variables for sure. We also do not know if a possible adjustable gas block is set for a certain operation and then fixed, or if the intention is to make adjustments more frequently.
There's a lot of good rails available now. Are there certain attributes for this rail that you want that others do not offer? The internal space for the gas block options does vary. That can limit options, just depends on what you want to do.

[WS6]

Larue has notoriously large gas ports and while I don't have this barrel in hand I would be very surprised if it wasn't on this barrel. An adjustable gas block allows you to tune the gas needed to the system. You claim a range of acceptable sizes and that may work well, but everything from the temperature to the ammo used will change the amount of gas flowing through the barrel. Add in factors like the amount of lube, suppressors, spring strength and buffer weight you get a range of acceptable gas for proper function. Having an adjustable gas block lets you narrow that range to one where the gun runs smoothly and reliably. Have you shot a rifle tuned with an adjustable gas block? I recommend you try it.

This rifle build is being built for a specific purpose of being used in Run N Gun competitions. Maybe I would buy different components if I was dropping in to a jungle at night and my life depended on it, or if I thought I would need to defend myself with it in my house. But I am building it for what is at the end of the day a game I like to play. If this gun should prove unreliable I will compete with another upper while I sort this one out. And if I do end up with a problem during a competition my life is not on the line so the benefits outweigh the potential downside for me.

I guess I just remember the only adjustable gas port I ever saw run truly hard, besides my Noveske SB (which froze up, too). It was a Surefire representative who had the gun, actually. He had tuned it so nice. It was so sexy. When he shot suppressed, it functioned great. However, he held the class up, had to come off the line, so on and so forth that first day. The gun got hot and dirty and drier than when he had tuned it. he needed to add lube to limp it through the day until he could re-adjust it that night.

Now the other experience I have with running a course suppressed the whole time is my own. I ran my DDM4 16.1" suppressed with a SF can for a VTAC course as well (the one I saw the other guy at was Streetfighter, I ran Nightfighter suppressed 100%). I chose to run Wolf 55gr, and applied lube once, before arriving. I never cleaned or added lube again, and after the 1500 round course, I dumped the can (grenade launcher style), and ran a few rounds unsuppressed. Worked fine still. Gun was FILTHY. but it worked 100% the whole time, except that I did have failures returning to battery ONLY when loading a new mag.

After speaking with Duane Liptak about it, the only conclusion we formed was the mil-spec spring + humidity + the fouled magazines led to rounds sticking to the lips slowing feeding. I replaced the mil-spec with a Green Sprinco, and it has been gravy ever since.

My point in this whole story is that all of this "tuning" of gas-blocks to get "super awesome function suppressed" is likely to bite you in the arse unless it's a system like the Govnah which allows you to quickly revert back to an unsuppressed setting, and even my Noveske SB froze up royally/got too hot to use, etc. It was supposed to NOT do that. Just like the Govnah. But I have no experience with the govnah, so I won't down it. I'll just say "be careful until you've actually done it".

[WS6]

As you stated, the porting for that barrel isn't optimal. I certainly know that registering another lower and paying the tax and wait time isn't an investment that a lot want to do in a "fun gun".
We do not know what can or possible ammo is in the mix, and those are variables for sure. We also do not know if a possible adjustable gas block is set for a certain operation and then fixed, or if the intention is to make adjustments more frequently.
There's a lot of good rails available now. Are there certain attributes for this rail that you want that others do not offer? The internal space for the gas block options does vary. That can limit options, just depends on what you want to do.

Honestly? I'd recommend he get a Daniel Defense or BCM 14.5" middy. Those are ported correctly, and shoot 1-2 MOA from most accounts and personal experience. If that's not accurate enough, then yeah, I understand, but I just don't see the point in getting an over-gassed barrel only to damp it down with a widget. It's counter-productive, IMO.

[tom12.7]

Yeah, I would prefer some other choices here.