300 WSM AR10

[budlight]

All of my ar10 308's are the rifle +2 inch gas tubes. I have the 24 inch SS fluted match grade barrels with 11 degree crowns. I had a hard time finding the +2 inch gas tubes in 2020. I've never even seen a +3 inch for sale.

I reload for my friends bolt 300wsm and after much testing Ramshot hunter is the go to powder.

I am not for building AR's with heavy buffer tube weights. Firm believer in less moving mass and adjust the gas block to get the best cycling. They get the crud beat out of the face by the bolt. I am for the heavier full auto bolts in all Ar's.

I've played the spring game and some of the more silent flat wound springs are nice. I've also played with diameters of the buffer tube hole and spring length weights.

Good luck on your project!

 

[Citified]

A lot of good information provided here. The challenge is managing the gas system with the adjustable gas block so the system is not over gassed. As heavily invested as you are in the project, I would suggest adding JPrifles captured buffer spring kit.
You can tune the buffer with the optional additional spring rate kit they offer. You did not mention the type of buttstock you will use. I own an Armalite AR10 and as you probably know those components are not all the same as the DPMS style.
FWIW, my rifle loves 168 and 175s and is very accurate. The trick here is reliable functioning.

 

[Earnhardt]

Citified, is your AR a WSM?

 

[Citified]

No, it is .308. Was just trying to be helpful with the gas system and buffer setup.
Should have mentioned it in my post. I have had this rifle a long time and have others I built on the DPMS platform. They are all a lot of fun and very reliable. As Glenn Zediker said in his original book, a quality barrel freefloated is the key.

 

[bamban]

You'll need to open up the ejection port slightly for cases to eject properly.

Thank you, will do.

 

[C-130 Dude]

These are fun rifles. I have the factory built DPMS 300 Saum. They did these with a 20" barrel and rifle length gas. Any longer and I'd definitely extend the gas system like Earnhardt said. I run a standard buffer but haven't tried any others.

I think the KAK bolt is a hp type with smaller diameter fp. Mine is not, and will pierce primers with bullets over 168's, even with non-max loads and cci 34 primers. So I stick with 168's and H4350 and it works well.

I made a single stack mag that holds 6 iirc and it works well. Pmags work for 3 or 4 and the same with some steel mags but mag bulge becomes an issue after 3 or 4 rounds.

I have built 18 of these large frames ar308/10 type guns. Every one of them have had pierced primer problems. The only way I have been able to mitigate this problem was to install a JP high pressure bolt assembly. The smaller firing pin works. No, I don't get $$ from them to state this. Messing around withe gas system can induce REAL nightmares. I did this on the first couple of guns and finally learned my lesson. My advise, stay with a rifle length gas system. Note that the gas tube length of an Armalite AR10 and the AR308(dpms style) are different lengths. I found this out the hard way. Large frame AR guns require lots of patience to build and wring out the problems. Different weight buffers and different rate spring are essential to balance your system. Good luck.

 

[C-130 Dude]

I have an itch to scratch. I have all the components to build a lightweight AR10 (yes Armalite) in 300WSM. I have a 10T barrel, reamer, GG, barrel extension, superlative adjustable gas block, KAK magnum BCG, and Armalite build kit. Even have 100 pieces of 300 WSM virgin brass.

Those of you who runs an AR308 type 300WSM, could you possibly share the good, the bad, and the ugly in running one? I am aware of mag limitations for heavier bullets, that's not a concern of mine at this point. I can address that separately. I am interested in knowing other stuff besides mag limitations.

TIA

Nez

I have built 18 of these large frames ar308/10 type guns. Every one of them have had pierced primer problems. The only way I have been able to mitigate this problem was to install a JP high pressure bolt assembly. The smaller firing pin works. No, I don't get $$ from them to state this. Messing around withe gas system can induce REAL nightmares. I did this on the first couple of guns and finally learned my lesson. My advise, stay with a rifle length gas system. Note that the gas tube length of an Armalite AR10 and the AR308(dpms style) are different lengths. I found this out the hard way. Large frame AR guns require lots of patience to build and wring out the problems. Different weight buffers and different rate spring are essential to balance your system. Good luck

 

[C-130 Dude]

Thank you, will do.

I put a Superlative adj block on and still had to open the gas port. Gas balance is critical, especially if you intend to run a can or muzzle break. Good luck

 

[C-130 Dude]

All of my ar10 308's are the rifle +2 inch gas tubes. I have the 24 inch SS fluted match grade barrels with 11 degree crowns. I had a hard time finding the +2 inch gas tubes in 2020. I've never even seen a +3 inch for sale.

I reload for my friends bolt 300wsm and after much testing Ramshot hunter is the go to powder.

I am not for building AR's with heavy buffer tube weights. Firm believer in less moving mass and adjust the gas block to get the best cycling. They get the crud beat out of the face by the bolt. I am for the heavier full auto bolts in all Ar's.

I've played the spring game and some of the more silent flat wound springs are nice. I've also played with diameters of the buffer tube hole and spring length weights.

Good luck on your project!

When you went with the +2 tube, did you find your gas system and timing going into fits of protest? How did you finally balance it out?

 

[bamban]

I have built 18 of these large frames ar308/10 type guns. Every one of them have had pierced primer problems. The only way I have been able to mitigate this problem was to install a JP high pressure bolt assembly. The smaller firing pin works. No, I don't get $$ from them to state this. Messing around withe gas system can induce REAL nightmares. I did this on the first couple of guns and finally learned my lesson. My advise, stay with a rifle length gas system. Note that the gas tube length of an Armalite AR10 and the AR308(dpms style) are different lengths. I found this out the hard way. Large frame AR guns require lots of patience to build and wring out the problems. Different weight buffers and different rate spring are essential to balance your system. Good luck

The JP high pressure bolts are the key to success when dealing with these large frame ARs. One of the 308 barrels I chambered for a friend had similar issue, pin hole is way too large. Since it is a lefty, JP did not have a bolt for one before. I sent the bolt to be bushed and pin ground to match the 0.062 hole.

No more issues hence.

308s are easy to mitigate. I just chambered a 16.5 inch suppressed hunter for me using mid length gas system without adjustable block.

Never have messed with 300WSM, not familiar with its pressure curve. The curve must be wide. I am playing with QL to see if I can simply do a ratio between rifle gas length, hole, and the pressure between the 308 and 300WSM to determine what size hole I need for the 300WSM.

On the service rifle we are not allowed adjustable gas blocks, so for 308 I have to use the correct gas port size. In this case I use 2mm reamed hole.

 

[Earnhardt]

I have built 18 of these large frames ar308/10 type guns. Every one of them have had pierced primer problems. The only way I have been able to mitigate this problem was to install a JP high pressure bolt assembly. The smaller firing pin works. No, I don't get $$ from them to state this. Messing around withe gas system can induce REAL nightmares. I did this on the first couple of guns and finally learned my lesson. My advise, stay with a rifle length gas system. Note that the gas tube length of an Armalite AR10 and the AR308(dpms style) are different lengths. I found this out the hard way. Large frame AR guns require lots of patience to build and wring out the problems. Different weight buffers and different rate spring are essential to balance your system. Good luck

Of the 18 large frames you've built, how many are/were WSMs or SAUMs?

 

[C-130 Dude]

Of the 18 large frames you've built, how many are/were WSMs or SAUMs?

2 WSM and 2 SAUM.

 

[C-130 Dude]

The JP high pressure bolts are the key to success when dealing with these large frame ARs. One of the 308 barrels I chambered for a friend had similar issue, pin hole is way too large. Since it is a lefty, JP did not have a bolt for one before. I sent the bolt to be bushed and pin ground to match the 0.062 hole.

No more issues hence.

308s are easy to mitigate. I just chambered a 16.5 inch suppressed hunter for me using mid length gas system without adjustable block.

Never have messed with 300WSM, not familiar with its pressure curve. The curve must be wide. I am playing with QL to see if I can simply do a ratio between rifle gas length, hole, and the pressure between the 308 and 300WSM to determine what size hole I need for the 300WSM.

On the service rifle we are not allowed adjustable gas blocks, so for 308 I have to use the correct gas port size. In this case I use 2mm reamed hole.

I have asked JP several times over the years to make bolts for lefties. No joy. I must say that if you are building an AR308 from ONE manufacturer, timing is easier. But if you use parts from different makers, be prepared for a few headaches. Gas port size, adjustable gas blocks, buffer weights, and spring rates are mandatory issues to get timing just right. Now add a can or muzzle break and you just added another wrench in the works. Yes it can be done. But it will take a bit to wring out. Stay safe and have fun.

 

[Gunpowder]

This thread made me get out my 300 Saum and pound a few targets. What a sweet round in an AR, makes me grin every time.

My 20" barrel sends the 168s at 2850 btw. Nice mild load.