.308 gas block, which one?

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gun'sRgood

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For all of you that have and continue to help with this problem child I would like to extend my warmest gratitude. It looks like I might be passing too much gas. [Sorry about that, I just couldn't help it. And my Wife would agree.] I know an adjustable block would be the easiest way but it looks like they cost as much as 5-6 of a preset one. BSF tells me the port size is 0.080. If you have sight to go to I
d really appreciate it. Thanks guys, Really awesome to have all this knowledge come to me. Oh yeah, the other idea was to use a heavier buffer weight. I just put the rifle spring and buffer on and I do believe that was absolutely needed. Moreover it was you guys passing your years of knowledge and experience. Where would you send me for rifle buffer weights? I did not weigh the one that was sent. Sorry. I know the more I can tell you the better your help.
 
If a rifle is overgassed, the solution is to reduce the gas, NOT to increase the reciprocating mass. So if you’ve diagnosed overgassing while using an appropriate reciprocating mass for your application, fix the gas.

I personally like the two piece, detent adjustable, (super) low profile JP gas block.
 
The AR-15 and the 308 AR can use the same block, just buy the one that fits your trunnion size. They also use the same gas tube, just matched to the port placement on the barrel. Carbine, mid or rifle length.
I personally prefer adjustable blocks, but I reload and change powders and bullet weights, so it is easier all round to change the gas flow to the carrier key to adjust the bolt opening for timing.
For an adjustable gas block; Start at full closed, you have a single shot. Open 1/2 turn until you get full function with lock back on an empty mag, just load one round at a time. Some like a 1/4 turn, I prefer 1/2.
 
I agree with you guys. I've got different blocks here and just don't want to spend my way out of a problem. Here good things about SLR. Thx!
 
I'd have to agree that anything I've ever ordered from JP was well worth the investment. Was that an adjustable bock?
 
On my LR308 I decided to just go with an odin works "tunable" gas block since all I really wanted to do was dial the gas back to where it just holds the bolt open on an empty mag of light "plinker" reloads. Once I got it set, everything has been running well! Less recoil, more accurate, and hasn't had much for malfunctions since.
 
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The question is, how do you know your AR is over gassed? Sometimes, an AR thought to be over gassed is actually under buffered.

Let me repeat what VT said- If a rifle is over gassed, the solution is to reduce the gas, NOT increase the reciprocating mass. He's absolutely right.

The corollary to that is, if the rifle is under buffered, the solution is to increase mass, NOT reduce gas.

I don't know what symptoms your AR is displaying. Some symptoms misdiagnosed as over gassing are actually from a weak extractor.

With 5.56 ARs, it's easy to fix extractor spring problems. Install a Colt or Sprinco M4 extractor spring.

308s are harder on extractors than their smaller caliber cousins and the springs aren't as durable or strong as they should be. I think the various 308 bolts use different springs. I don't know what spring to recommend. I'm still trying to sort out the extractor in my 308.

If you have an extractor spring problem, you can't begin to determine if your AR is over gassed or under buffered or whatever, until the extractor spring is fixed.

If you have a weak extractor spring, your AR will display some kind of failure to eject.

In any case, to trouble shot your AR, we need an accurate description of the symptoms. Don't tell us what the problem is, describe it accurately.
 
PS- When tuning the gas system, start with enough gas flow to operate the the action. Starting with it closed is to invite stuck cases in the chamber.

Close the gas with each shot until the rifle ejects but does not lock back. Then, open the gas one click or one quarter turn until the rifle ejects and locks back.

DO NOT PAY ANY ATTENTION TO EJECTION ANGLE!

Ejection angle will tell you nothing about how your AR is gassed. If you don't believe me, try it for yourself.

If the ejection angle does move forward, either over time or when increasing gas flow, it's often an indication the extractor spring is failing. (This assumes the ejector is functional and not modified.)
 
MistWolf said:
The question is, how do you know your AR is over gassed? Sometimes, an AR thought to be over gassed is actually under buffered.

Let me repeat what VT said- If a rifle is over gassed, the solution is to reduce the gas, NOT increase the reciprocating mass. He's absolutely right.

The corollary to that is, if the rifle is under buffered, the solution is to increase mass, NOT reduce gas.

I don't know what symptoms your AR is displaying. Some symptoms misdiagnosed as over gassing are actually from a weak extractor.

With 5.56 ARs, it's easy to fix extractor spring problems. Install a Colt or Sprinco M4 extractor spring.

308s are harder on extractors than their smaller caliber cousins and the springs aren't as durable or strong as they should be. I think the various 308 bolts use different springs. I don't know what spring to recommend. I'm still trying to sort out the extractor in my 308.

If you have an extractor spring problem, you can't begin to determine if your AR is over gassed or under buffered or whatever, until the extractor spring is fixed.

If you have a weak extractor spring, your AR will display some kind of failure to eject.

In any case, to trouble shot your AR, we need an accurate description of the symptoms. Don't tell us what the problem is, describe it accurately.
Click to expand...
I believe you are absolutely correct! I guess I've put about 15 AR15's together. Then I made the incredibly stupid, arrogant, ignorant "Assumption" that I knew something about an AR10's! Or for that matter, like I'm a seasoned armorer of any kind. My apologies to all of you that, for some reason, keep hanging around trying to help me. I can not tell you how grateful I am to all of you. I've got an adjustable block coming and I see that getting a couple of heavier buffer "rifle" weights should be on my purchase list. Side note: While living as a professional student, Philosophy was one of my more enjoyable pursuits. Back then, about 40 years ago, I could prove that the more you know, the less you know. Today I'm just living proof. Here's kind of how it works: Take a balloon and blow into it. Everything inside the balloon is what you know. The surface area outside the balloon is what you don't know. As you continue to blow into the balloon, knowing more, the surface area outside the balloon exponentially expands. Hence, the more you know, the more you don't know. And now I've forgotten most of what I used to know making me just full of hot air. I guess I am over gassed. I'll try for a video next range date
 
AliExpress, These guys have what is probably junk. But the prices are so cheep I thought I'd put a heads up for boy-toys. BTW, this is NOT where I went to get my adjustable gas block
 
For some reason it probably isn't and I'm absolutely no closer to figuring this thing out. Thx MW! Hope to have good news soon.
 
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