Reloading for a rifle with an adjustable gas block….

[PinesAndProjectiles]

I’ve loaded for a few ARs but most of my experience is reloading for bolt guns.

I’ve got a rifle that I’ve had for a while and now am wanting to find a load for it.

This rifle has an adjustable gas block.

When starting the loading process, is there any benefit to completely closing off the gas block, find a load that I’m happy with, and then open up the gas block until the rifle cycles reliably?

Or does the cycling of the bolt factor too much into the rifle that an accurate “single shot” load won’t stay consistent once the rifle goes to functioning as intended?

 

[Kadams1563]

Hmmm. Interesting.

I haven’t thought of doing that way but I believe you would find and accurate load and then it might not be once the action is beating the hell out of it getting it in the chamber. I don’t know though.

What I do is open gas block all the way and load until I get what speed/accuracy I expect then I start closing gas block down until it will lock back on an empty mag.

I shoot my AR’s suppressed so I usually tune to where it won’t lock back unsuppressed but will suppressed. I don’t have a low back pressure can yet.

 

[bfoosh006]

I would reload for the rifle as it is intended to used.
There are so many moving parts involved in a semi auto, it is kind of a balancing act.

Interesting thought though. If you try it, please let us know your results.

 

[MontanaMan]

I’ve loaded for a few ARs but most of my experience is reloading for bolt guns.

I’ve got a rifle that I’ve had for a while and now am wanting to find a load for it.

This rifle has an adjustable gas block.

When starting the loading process, is there any benefit to completely closing off the gas block, find a load that I’m happy with, and then open up the gas block until the rifle cycles reliably?

Or does the cycling of the bolt factor too much into the rifle that an accurate “single shot” load won’t stay consistent once the rifle goes to functioning as intended?

Tune the rifle to the lightest load in your matrix to just lock back as normal.
Depending on the range of loads, it maybe be OK or may need finè tuning as you go up in loads.
I would not test loads in a mode not normal to the end use mode.

JMHO, YMMV

MM

 

[LRRPF52]

One problem you’ll encounter without being able to see it happen with most adjustable gas blocks that use set screws, is that the set screw itself gets eroded in the gas flow-path.

SOTAR posted an excellent video yesterday having to reverse-abort 2 Black Rain Ordnance LEA select-fire guns that were trash.

Among a laundry list of things wrong with them, they had huge gas ports with set screw adjustable gas blocks.

He put a bore scope down them to show what it looks like when you adjust the set screw, and you could see how obviously-eroded the screws were. Once you think you have a set screw gas block dialed-in, that screw is being furnace-torched with each round fired, and gets burned down like a pencil eraser. Then more gas flows through and increases the cyclic rate, which requires you to screw the log over the fire some more.

Go to 1:40:00 in the video to see what I’m talking about. This is probably the first time I’ve seen someone demonstrate with a bore scope what some of us have been trying to describe for many years:

 

[PinesAndProjectiles]

One problem you’ll encounter without being able to see it happen with most adjustable gas blocks that use set screws, is that the set screw itself gets eroded in the gas flow-path.

SOTAR posted an excellent video yesterday having to reverse-abort 2 Black Rain Ordnance LEA select-fire guns that were trash.

Among a laundry list of things wrong with them, they had huge gas ports with set screw adjustable gas blocks.

He put a bore scope down them to show what it looks like when you adjust the set screw, and you could see how obviously-eroded the screws were. Once you think you have a set screw gas block dialed-in, that screw is being furnace-torched with each round fired, and gets burned down like a pencil eraser. Then more gas flows through and increases the cyclic rate, which requires you to screw the log over the fire some more.

Go to 1:40:00 in the video to see what I’m talking about. This is probably the first time I’ve seen someone demonstrate with a bore scope what some of us have been trying to describe for many years:

I’m failing to see the purpose of your post. Are you trying to convince me to not use an adjustable gas block?

If so, I don’t understand how this pertains to my post.

 

[LRRPF52]

I’m failing to see the purpose of your post. Are you trying to convince me to not use an adjustable gas block?

If so, I don’t understand how this pertains to my post.

I’m pointing out that if you rely on the AGB, it will likely erode on you and will need continual adjustment.

In my personal experience with several of them, the set screws have become welded with carbon and unable to adjust after that.

If you approach loading for it with shut-off, then incremental retraction of the choke, it will be important to pay attention to the cyclic rate as time goes by once you find your initial lock-back and buffer zone from lock-back.

Ambient temperature will also play into proper gassing vs short-stroking, the colder it is, the more likely to experience short-stroke.

 

[Vynz]

One problem you’ll encounter without being able to see it happen with most adjustable gas blocks that use set screws, is that the set screw itself gets eroded in the gas flow-path.

SOTAR posted an excellent video yesterday having to reverse-abort 2 Black Rain Ordnance LEA select-fire guns that were trash.

Among a laundry list of things wrong with them, they had huge gas ports with set screw adjustable gas blocks.

He put a bore scope down them to show what it looks like when you adjust the set screw, and you could see how obviously-eroded the screws were. Once you think you have a set screw gas block dialed-in, that screw is being furnace-torched with each round fired, and gets burned down like a pencil eraser. Then more gas flows through and increases the cyclic rate, which requires you to screw the log over the fire some more.

Go to 1:40:00 in the video to see what I’m talking about. This is probably the first time I’ve seen someone demonstrate with a bore scope what some of us have been trying to describe for many years:

Watched the whole thing, that video was real informative. I hope I can find one where he goes over installing a barrel. So far from this video I haven’t done anything too stupid aside from hoping (not checking) how in-spec parts I’ve bought are aside from headspace gauges.

 

[mtrmn]

I THINK that if you start seeing pressure signs (ejector swipes, bent/torn cartridge rims, etc) as you increment up in powder charges, then you could shut off the gas and fire a couple rounds. If those rounds still show pressure signs, then you can rest assured it's actually pressure. This would help to determine if it's really pressure or perhaps not enough reciprocal weight, too much gas, etc

 

[PinesAndProjectiles]

I THINK that if you start seeing pressure signs (ejector swipes, bent/torn cartridge rims, etc) as you increment up in powder charges, then you could shut off the gas and fire a couple rounds. If those rounds still show pressure signs, then you can rest assured it's actually pressure. This would help to determine if it's really pressure or perhaps not enough reciprocal weight, too much gas, etc

Thank you for this. I’m by no means a gas gun expert but removing the gas from the situation would definitely make it easier to identify over pressure signs and isn’t something I would have thought about.

 

[DHDeal]

Not that I'm any sort of expert, but I've loaded for more than a few AR's with AGB's. I tend to have them set for lockback and work up a load. If during work up I notice higher pressure, I may close it up a click or two. I shoot mostly suppressed (hell, nowadays only suppressed) and have the SA or SLR AGB's set for lockback and then open another click, so I run them more towards closed anyway.

The only time any issues were involved was getting my 300BO SBR to run with both subs and supers. My 223's and Grendel's were easy and not banging the rifles up.