Adjustable gas block question

[TrueBlue711]

I just got my first adjustable gas block for my 300 BLK pistol with the goal of suppressing it. It is the one made by Ergo and the adjustment is simply a screw on the right side of the block. The screw is very easily adjusted and I'm concerned about it backing out while firing. How do you set the screw so it doesn't move? Blue loctite? Wouldn't the gas block get so hot, that loctite would melt and seep out? Obviously don't want to use red loctite since I'll be adjusting it. Suggestions would be appreciated.

[jugornot]

Mine uses a detent that holds the adjustment screw to quarter turns.

Bill

[stagpanther]

Most adjustable blocks have an inner set screw which is then locked into place by another screw that goes on top of it (unless you have a screw/dial type like syranac's). One thing to mention--carbon build-up in the block and screw gaps will eventually seal them--I wouldn't worry about a screw backing out without locktite--in addition, you'll probably find yourself adjusting pretty often if you change load types frequently.

I have a 300BO pistol but do not have a suppressor--but from what I've read/heard it's apples to oranges comparing a suppressed carbine to a suppressed pistol.

[TrueBlue711]

Another question. Found out how to properly adjust the adjustable gas block (start off with it completely closed, keep shooting one shot at a time while opening up the gas block until bolt locks back). So when going to suppressed, would you need to adjust the gas block differently (i.e. open it more)? Or is it good to have the gas block as closed as possible for suppressors?

[MarkCO]

When you get frustrated with the one you have, get a Superlative Arms. Not a fan of adjustable gas blocks because of what stagpanther mentioned. But the SAs are the best of the batch and the only ones I will use, when I have to.

In most cases, the suppressor will need the gas block closed off a tad more to achieve the same cycling. If you want Hollywood, just close off the block and run it is a manual.

[imashooter]

If you don't have an additional set screw, you need to find where you are going to set it, then remove the screw. Upon removing it, count the number of rotations. Give it a little high - heat threadlocker and count the same number of turns upon re-installation. I'd let it set 24 hours.

[Double Naught Spy]

Gotta agree with what MarkCO says. I have the same SA system on my SA piston system and it works well and doesn't lock up like my Syrac did.

[Mobuck]

"So when going to suppressed, would you need to adjust the gas block differently (i.e. open it more)? Or is it good to have the gas block as closed as possible for suppressors?"
You will probably need to reduce the gas when using the muffler.
I added an adjustable gas block to my 300 ( carbine length gas) only to find that the adjustment had to be wide open to function w/o muffler. My solution after some experimentation was to use a lightweight bolt carrier when firing w/o muffler and standard BC w/muffler.
Later, the addition of a second 300 upper allows me to have one set up for suppressed and one open.

[stagpanther]

When you get frustrated with the one you have, get a Superlative Arms. Not a fan of adjustable gas blocks because of what stagpanther mentioned. But the SAs are the best of the batch and the only ones I will use, when I have to.

In most cases, the suppressor will need the gas block closed off a tad more to achieve the same cycling. If you want Hollywood, just close off the block and run it is a manual.

I run the SA as well as JP and odin's--odin's is my current fav, the SA is nice--but IMHO limits the range of adjustment clicks (which makes it easier for some I guess) and I'm not entirely convinced the locking set-up is really all that robust.

[Double Naught Spy]

"So when going to suppressed, would you need to adjust the gas block differently (i.e. open it more)? Or is it good to have the gas block as closed as possible for suppressors?"
You will probably need to reduce the gas when using the muffler.
I added an adjustable gas block to my 300 ( carbine length gas) only to find that the adjustment had to be wide open to function w/o muffler. My solution after some experimentation was to use a lightweight bolt carrier when firing w/o muffler and standard BC w/muffler.
Later, the addition of a second 300 upper allows me to have one set up for suppressed and one open.

So adding a suppressor will increase the pressure in your gas system and cause your bolt carrier group to cycle faster, potentially resulting in malfunctions. You need to reduce the pressure getting to the BCG.

On the Superlative Arms, you have the option of either opening up the gas block to reduce the amount of gas getting to the BCG (bleed off) or restricting the amount of gas getting to the BCG. It is rather quite ingenious.

The bleed off function does several things. It reduces pressure to the BCG. It releases some dirty gas from the system instead of forcing all of it through your BCG. Based on the tests of a guy on Youtube, it will reduce the noise from your gun by 1-2 db. The downside, he found, was that it reduced velocity by 20-30 fps as well.

The huge downside to shooting suppressed is how much nastier your gun will get, but it isn't just your gun. Those dirty gasses also get down into your magazine and dirty rounds waiting to be fired. Regularly topping off your mag is not the best idea with a suppressor as the bottom rounds will get dirtier and dirtier.

[MarkCO]

No gas block other than SA has ever made it past 3K on my .308 without some sort of problem, usually erosion which is adding gas and defeating the benefits. It is pretty robust.

[Mobuck]

"The huge downside to shooting suppressed is how much nastier your gun will get, but it isn't just your gun. Those dirty gasses also get down into your magazine and dirty rounds waiting to be fired. Regularly topping off your mag is not the best idea with a suppressor as the bottom rounds will get dirtier and dirtier."
From my experience, it's not only with DI guns. My Adams Arms piston upper still shows some fouling in the magazine when set on the "low" setting w/muffler. Far less than the DI it replaced but still there. This is obviously being blown back through the chamber by back pressure in the muffler since there's no other way for it to get into the receiver.
I only "top off" while hunting. Empty the mag and refill with "clean" ammo on the bottom and fouled at the top at the end of the day.
__

[stagpanther]

No gas block other than SA has ever made it past 3K on my .308 without some sort of problem, usually erosion which is adding gas and defeating the benefits. It is pretty robust.

Haven't had any problems with my SA yet either--the dial/click/set mechanism just seems a bit flimsy to me--but I'm no expert. When you say erosion--do you mean literally metal is corroding away--or simply gas forces it's way past seals on the block and set screws?

[Mobuck]

"When you say erosion--do you mean literally metal is corroding away--or simply gas forces it's way past seals on the block and set screws?"

Hot, high pressure gas can cut(erode) the gas passage in the gas block as it blasts through the tiny orifice. Some(most?) gas blocks aren't made of material known for good gas erosion resistance.

[stagpanther]

The odin ones I currently favor are cut from 303 stainless.

[MarkCO]

Originally Posted by Mobuck

"When you say erosion--do you mean literally metal is corroding away--or simply gas forces it's way past seals on the block and set screws?"

Hot, high pressure gas can cut(erode) the gas passage in the gas block as it blasts through the tiny orifice. Some(most?) gas blocks aren't made of material known for good gas erosion resistance.

Yes, the hot gases, entrained sometimes with burning powder granules, gas cut the metal. The screws that go into the gas stream to limit flow are often the first to go carrying metal into the bolt and gas rings.

303 is a relatively inexpensive commodity stainless, even if with the L designation, won't last as a gas block long term. 400 series stainless with proper heat treat (which is the key) is the way to go. Odin's more expensive adjustable with Carbon Steel and the Inconel screw is better, but still has some issues.

[stagpanther]

Appreciate that Mark--I may be wrong but I think they specifically rate the carbon steel for lower pressures--that's why I tend to get the 303 stainless. I don't remember what SA's is made of.

[MarkCO]

SA uses 416 stainless for the stainless, and Melonited Steel. Both are appropriate and much harder than untreated steel or 303.

I make a gas block (non-adjustable) and comp for the AR15 and I only use 416. I pay more for the heat treat than some companies charge for their parts retail...it is that important to me to make the best parts I can. We have never had a failure of our gas block or comp. In fact, while most comps last for the life of a barrel, ours last for the life of several barrels.

I did a lot of poking and prodding to check out SA before I bought one of their gas blocks, and now I have three. I have a box with at least two dozen failed adjustable gas blocks. SA did a great job and that is the only reason I use and recommend them, and I have no association with them at all. Ask me what trigger or comp, I will say it depends...adjustable gas blocks, only SA gets the recomendation from me.

[stagpanther]

Hard to argue with that Mark--thanks!

[Double Naught Spy]

"The huge downside to shooting suppressed is how much nastier your gun will get, but it isn't just your gun. Those dirty gasses also get down into your magazine and dirty rounds waiting to be fired. Regularly topping off your mag is not the best idea with a suppressor as the bottom rounds will get dirtier and dirtier."
From my experience, it's not only with DI guns. My Adams Arms piston upper still shows some fouling in the magazine when set on the "low" setting w/muffler. Far less than the DI it replaced but still there. This is obviously being blown back through the chamber by back pressure in the muffler since there's no other way for it to get into the receiver.
I only "top off" while hunting. Empty the mag and refill with "clean" ammo on the bottom and fouled at the top at the end of the day.

Correct, but in my experience, there is HUGE difference in the amount of fouling between suppressed DI and suppressed piston systems.

Like you, I top off when hunting and I may top off several times in a night when going after hogs. I also top off doing drills.

On top of that, mags stay much cleaner with a piston system when running suppressed over DI. Topping off or not, crap is forced down into the mags.

Bottom line, if running suppressed, your gun, mags, ammo are going to stay a LOT cleaner with a piston system.

[Road_Clam]

Honestly, I built a 16" 300 BLK and I have a standard gas block. I have a pistol gas system and a standard carbine buffer system. My system functions supersonic suppressed perfect. My rifle also cycles subsonic suppressed good, my only issue that's work in progress is i'm having feed issues when shooting 220 gr smk's. For some reason my rifle won't fully chamber the 1st round stripped out of the mag. I think I need to experiment with a stiffer buffer spring.

[Mobuck]

"Correct, but in my experience, there is HUGE difference in the amount of fouling between suppressed DI and suppressed piston systems."

I would say the difference in magazine fouling is "moderate" while the difference in BCG fouling is truly HUGE.

[Mobuck]

"When you say erosion--do you mean literally metal is corroding away"

I didn't properly address this in my previous post but will now clarify.
Corrosion is a chemical transformation/degradation of a substance.
Erosion is a physical action on a substance by another factor such as wind water or in this case hot gases.

[stagpanther]

OK

[TrueBlue711]

Update: I FINALLY went to the range to tune my gas block to subsonic 300 BLK rounds (Hornady BLACK 208 grain ammo). Completely closed it off, loaded one round in the mag, shot it, saw to see if bolt locked back, open up the gas block 1/4 turn, then rinse and repeat. I damn near had to open the gas block all the way to where the adjustment screw was only being held in by a few threads before the bolt finally locked back after being shot. I'm starting to reconsider the adjustable gas block and just put a normal gas block back in it. Would putting in a lighter buffer in it help remedy this? I have a Spikes Tactical T1 (~3oz) buffer in it now with a pistol buffer tube + spring.