Thread: Getting Ar15 adjustable gas block from US

If you have a drill,a tap and a grub screw it's no big deal to do yourself.

But if your close to him and he's only asking $30.....

I wonder if there is enough meat to drill into a low pro gas block. Does the grub screw go into the tube through the block?

Not into the tube itself (the tube is a consumable remember) into the area before the tube to limit the gas entering the tube.
Some aftermarket barrels have smaller gas holes than others so effectively all ready do this-I have a true flight barrel that has a tiny hole so doesn't really need an adjustable block. The cheeper the gun the more likely it is to have a large hole to make it more reliable-these old guns that no one ever thought were going to get suppressed are why everyone now thinks they need an adjustable block if they are fitting a can.

Originally Posted by res

Some aftermarket barrels have smaller gas holes than others so effectively all ready do this-I have a true flight barrel that has a tiny hole so doesn't really need an adjustable block. The cheeper the gun the more likely it is to have a large hole to make it more reliable-these old guns that no one ever thought were going to get suppressed are why everyone now thinks they need an adjustable block if they are fitting a can.

I have to disagree. If the gun cycles at all unsuppressed, then it's going to be overgased when suppressed.

More gas than needed to make something just work does not make it automatically over gassed.
Not all ar's are race guns tuned to within an inch of its life. A lot of modern cans also don't cause anywhere near the extra back pressure that older cans did as another factor.

The truflight barrel I was talking about is not reliable with all ammo without a can btw.

Over gases is a over talked and thought subject for a lot of modern guns unless your moving into short gas systems.

From your pics you have barrels that are designed for military applications so they will probably have a largish gas hole to ensure function with almost any ammo and a dirty gun. So yes I can see why you find it important

At the end of the day an adjustable block puts one more thing to go wrong on the gun,but it rairly does so for my use I run them-even tho I no longer think I need them on most of my rifles.

OSS claims that suppressors from 'industry leaders' (in the states) increase bolt velocity by 28 to 44 percent. A 44% increase in bolt velocity is over 100% increase in kinetic energy. An AR that just barely cycled unsuppressed would suddenly cycle with over twice the energy it needs. In other words the bcg/buffer would slam into the back of the extension with as much energy as if you shot a correctly gassed AR with no buffer spring in it.
Even a 28% increase in bolt velocity equals a 64% increase in Ek. Like you said, gas ports are generally slightly larger than needed to ensure reliability, so taking that extra energy into account, a 64% increase on top of that isn't exactly a small increase that should be ignored.

I'm not sure who OSS are,but it's interesting to see numbers rather than just observations.

Not sure what those number = in the real world.

I personally have always thought of over gassed as being when there are problems showing up, eg marks in the receiver/extension or the action getting dirty at an excessive rate(and that is subjective as everyone has different tolerance to cleaning) or the bolt not picking up rounds due to excessive speed. In a race gun I have used an adjustable block to try to keep the gun as still as posable while it cycles-to enable more accurate double taps,light weight carriers were part of that as well. Stoping excessive gas in your eyes is another plus but I find a moded charging handle helps a lot more with this.

Personally never seen an extension more than marked from the buffer,so to me it's not that big a deal.

Part of my thinking as to why people can be to gas block happy is a lot of people set them up so things only just work with one sort of ammo and then something changed-eg ammo,temperature,altitude or cleanliness of the gun and they start having problems. This is why makers run more gas than they need by a big margin,and it's why on my rifles
I set them up so that I'm risking being slightly over gased rather than slightly under gased.

I hope it does not come across as trying to argue with you about it,it's just interesting to talk about-and as I have said I run adjustable blocks on most of my rifles.

Operator Suppressor Systems Oss Operators Suppressor Systems - Silencers
They make suppressors with a turbine type system instead of baffles.

When I say over gassing, I'm meaning past the margin for reliability. You should definitely have more gas than the minimum required for cycling to have a margin of reliability, but a suppressor will often greatly exceed this margin, even on an already lowly gassed gun. It's not like over gassing by an extreme amount will ensure better reliability in adverse conditions. The action spring will be the weak link and will fail to return the bolt in to battery, making all that excessive energy that ensured full rearward bolt travel fairly redundant.
Then there are all the negative effects of increased bolt velocity. More blowback, increased wear, higher chance of malfunctions, increased felt recoil, rougher extraction. Even if a gun cycles without issue when over gassed, it will still develop malfunctions sooner than if it wasn't.

The way I look at it is, gas dwell time and gas port diameter on a gun have been tuned to one another to ensure correct cycling. If you change one, you need adjust the other. Screwing a suppressor on the end completely changes dwell time and the depressurization of the barrel. The gun is no longer functioning as designed and in a less than optimal state. I can't think of any reasons to purposely leave a gun excessively over gassed, but I can think of plenty of reasons to tune it down.

It almost sounds like we are setting things up the same,just starting the conversation from dif ends of the possibilities .

Spiral cans? Like a de sail .45-that's cool