98Z5V

That 0.875" is the diameter of the gas block journal, and the size of the gas block that you'd need to buy, if you were buying another. Gas block sizes (standard sizes) are 0.625", 0.750" 0.875", and 0.936". Yours is 875. Gas block journal size has a direct effect on gas port diameter size - two barrels made identical, say 18" midlength gas barrels, one with a 0.750" gas block journal, and one with the 0.875" gas block journal - the same-sized gas port is not going to work perfectly on both those barrels. It's a pressure that needs to be maintained for cyclic function. You change that pressure when you change the cylindrical volume of a gas port: make it smaller or larger - gas port size - or, make it deeper or more shallow - gas block journal size. For recoil - you need to balance the system, and if it's kicking you hard, it's not balanced. The first indication is that 3.8oz buffer weight, and that spring. The easiest, cheapest thing to do is buy the Armalite (real Armalite, not copies) AR-10 Carbine Receiver Extension kit. That will SOLVE the recoil system. The next thing you need to do is determine the diameter of your gas port. Then drill it up, if it needs it. Buy a cheap digital vernier caliper from Harbor Freight, use numbered drill bits, there are numerous ways to determine gas port size. This is the recoil system that you need to be running on a .308AR: https://www.armalite.com/product/ar10rekit01-6-position-receiver-extension-kit/

Your gas tube is good to go. Cross that off the list. Recoil system needs fixed, and there are a couple ways to do that. You'll need a gas port diameter of 0.085"~0.090" for that rifle to run correctly. Next step is finding out what the gas port diameter really is.

You're looking for 3/16", if everything is perfect in the world. Some fuktard over on THR stole that number from one of my posts from a long time ago, and think's he's a hero over there, acting like he came up with it...

You're not overgassed. You're under-recoiled. What's the gas port diameter in that barrel? What's the gas block journal size? Got a pic of how far the gas tube extends into the upper receiver? You could have multiple things going on here - buy you are under-recoiled. Not over-gassed. That's why it's kicking hard. Oh, and it's not a DPMS .308. It's based on the pattern - but thats why I backed up edgecrusher, asking if it was a factory DPMS rifle - which it is not.

Want me to try to T&E one of those?...

AZ'ers should come out to the Capitol this Saturday, 15 Feb, 10am~2pm for the annual 2A rally: https://2ndamendmentrallyaz.com/

Just those damn trees...

https://www.fddefense.com/rifles/fd308/ Look, they even have "The World's First ,338 Lapua Magnum AR Platform" https://www.fddefense.com/rifles/fd338/

They made some badass CAD drawings in 2011, 2012 - billet receivers, renderings of them. I posted about them here. Reaaaaally wanted them to get produced, and be somethings besides vaporware.

Long Distance is fun. Takes time and money to get proficient, but it's worth it. Make sure you hit up this thread about it:

This is honestly the best place he should start, Doc, right here: https://lmgtfy.com/?q=Sprinco+Orange+spring Click that ^^^, and you're in business.

Sprinco.

This is the biggest part.

Or, they're not making any money on ARs. Too many smaller, better companies out there, brother.

12 Angry Dems that took Bloomberg money. It'll never get through, not this year. But it's a wake-up call, for sure. Bloomberg ironically setup a campaign office in Phx about a week ago...

Each quarter is 0.069" thick - one would do, since the internal depth on that is right on at 7.000". Next - shoot it. Function test it with live ammo. Put rounds downrange. Start with a single round in the mag, and see if it will lock the bolt back. That's the first test. It's not going to, I'll bet. That gas port is gonna need to go up, so you might as well just take the gas block off there one time (maybe 2), so put the Armalite AR-10 Carbine gas tube in there when you're in there. It's longer than an AR15 midlength gastube (and has the appropriate bends in it for a .308-sized barrel). Here's the gastube: https://www.armalite.com/product/ar-10-carbine-length-gas-tube-10007005/

That's TactiCat. He's an as$hole, and 12lbs. He's handful, enough. I've always wanted one of these jackasses, though. Cute when little. If I could tame it, raise it right, this would be a badass cat. Doesn't have anything to do with maximizing space in a gunsafe - but I've always wanted a mountain lion.

SHIIT...

You're the guinea pig in this one - nobody here has ever built one yet. Let's get it on. DPMS high-profile rail, so start searching that out. As far as barrel manufacturers - you haven't even mentioned the caliber yet. There are very, very few piston guns in the large frame format - and when there are, it's usually complete rifles - not component parts. Finding a stand-alone piston system that you can bolt on to a large-frame AR - good luck. Better get used to a DI system - they work, very, very well.

Found one available here: https://www.firequest.com/ML433.html

Burt Gummer is my Idol. One day, I will achieve his status.

I truly LOVE M18A1 Claymore mines. Just LOVE 'em! 🥰

TactiCat is up to 12lbs now - and I don't want to fight him. I'd fucking RUN if he was 300lbs... Fuk that.

Gotta let 'em eat - but I can't let them all out together. I'd need to buy 10 Australian Shepherds just to keep shiit in line...