My 300 is finally done, I think

[Dolomite_supafly]

Good luck finding one of those stocks. They are snatched up almost immediately as they become available. I lucked out and found one. You know the vendor if you want ot pick one up.

It is the same length as a regualr A2 stock but has more storage. I am going to probably add the QD swivel mounts but other than that I really like how it works and feels.

Dolomite

[samson7x]

Very nice looking rifle sir. Well done.

[orientalexpress]

I have yet to try that stock on a rifle. I may have to pick one up at work, as I didn't realize they were that popular.

[atlas3025]

Nice!

[Guest FIST]

Can you run any length gas system other than pistol with this round?

[mikegideon]

Can you run any length gas system other than pistol with this round?

They say you can run carbine. That's what mine is. I haven't shot any subs in mine yet. May not cycle with some of those 12 lb mortars that Dolomite's running thru his

From AAC...

Q: Should I look for an AR upper with carbine or pistol gas?

A: First, there is no barrel length which works with mid-length or rifle gas. The choices are carbine or pistol. For barrels under 16 inches, pistol is needed - the bore is larger than 5.56mm so the gas pressure drops off faster. For barrels 16 inches or longer, carbine or pistol gas will work.

Q: Well then - for a 16 inch barrel, why would someone chose one type of gas vs the other?

A: If you are the type of person who prefers mid-length gas on a 5.56mm because it has less gas port erosion and less stress on the bolt and extractor, then choose carbine gas. If you want to experiment with extra fast-burning powders and are willing to either not shoot full power ammo or have an adjustable gas block - then use pistol. Remington subsonic ammo generates enough gas pressure to be compatible with carbine gas in a 16 inch barrel.

Edited October 26, 2012 by mikegideon

[Guest FIST]

They say you can run carbine. That's what mine is. I haven't shot any subs in mine yet. May not cycle with some of those 12 lb mortars that Dolomite's running thru his

From AAC...

Q: Should I look for an AR upper with carbine or pistol gas?

A: First, there is no barrel length which works with mid-length or rifle gas. The choices are carbine or pistol. For barrels under 16 inches, pistol is needed - the bore is larger than 5.56mm so the gas pressure drops off faster. For barrels 16 inches or longer, carbine or pistol gas will work.

Q: Well then - for a 16 inch barrel, why would someone chose one type of gas vs the other?

A: If you are the type of person who prefers mid-length gas on a 5.56mm because it has less gas port erosion and less stress on the bolt and extractor, then choose carbine gas. If you want to experiment with extra fast-burning powders and are willing to either not shoot full power ammo or have an adjustable gas block - then use pistol. Remington subsonic ammo generates enough gas pressure to be compatible with carbine gas in a 16 inch barrel.

Thanks.

[Dolomite_supafly]

I run the pistol length with a 3 way block. That way I do not overgass my gun with supers and I can run really mild subsonics. As a matter of fact I was shooting some 180 bullets earlier and they were cycling and locking back. I did n't notice a supersonic crack so they are likely subsonic. That would never happen with a carbine length gas system. I can also tone down my supers. Rather than have a 150 grain bullet at 1,800 fps I can switch my gtas block to subs and shoot the same bullet at probably 1,400 fps. This is veru important to me because I am recoil sensitive because of an accident.

One advantage to the carbine length system is if you find a subsonic load that works you don;t need to fool with an adjustable gas block. Problem is getting a load that has enough pressure to cycle a carbine length gas system AND stay subsonic. The easiest way to increase pressures without increasing velocity is to use heavier bullets. I shoot 240 grain cast bullets, which are equal to 220 SMK's, in order to keep the pressures up. I suspect a combination of slower powders, to keep pressures up, and heavy bullets, to also keep pressures up, are what is needed for a carbine to cycle with subs.

Dolomite

[Lumber_Jack]

Dolomite,

What are ways to tell if you are over gassing your gun? I can tell of its under gassed, i.e. doesn't cycle, bolt doesn't lock back.

[Dolomite_supafly]

The exact same signs as when the gun is under gassed as far as cycling goes. Failure to lock back, failure to pick up the next round. Another is the recoil being more noticeable when compared to other AR's. But you have to take the weight of the gun into account. A 10 pound AR will not recoil like a 5 pound AR.

The biggest indication is the brass and how badly it gets chewed up. Rims getting ripped off. Major dents.

Another indication is a dirtier than normal gun. Like shooting quality ammo and it looks like you have been shooting Wolf.

But honestly having a overgassed gun is a rarity. Persoanlly I think most carbine length gas systems are designed to be overgassed for reliability. The spec for the port size on a carbine length gas system with a 16" barrel is .077"-.083". I recently worked on a gun that was running 100% with a port size that was just over .070".

Dolomite

[samson7x]

I run the pistol length with a 3 way block. That way I do not overgass my gun with supers and I can run really mild subsonics. As a matter of fact I was shooting some 180 bullets earlier and they were cycling and locking back. I did n't notice a supersonic crack so they are likely subsonic. That would never happen with a carbine length gas system. I can also tone down my supers. Rather than have a 150 grain bullet at 1,800 fps I can switch my gtas block to subs and shoot the same bullet at probably 1,400 fps. This is veru important to me because I am recoil sensitive because of an accident.

One advantage to the carbine length system is if you find a subsonic load that works you don;t need to fool with an adjustable gas block. Problem is getting a load that has enough pressure to cycle a carbine length gas system AND stay subsonic. The easiest way to increase pressures without increasing velocity is to use heavier bullets. I shoot 240 grain cast bullets, which are equal to 220 SMK's, in order to keep the pressures up. I suspect a combination of slower powders, to keep pressures up, and heavy bullets, to also keep pressures up, are what is needed for a carbine to cycle with subs.

Dolomite

I ended up building my 300 with carbine gas on 16" barrel and wish I could have found one with pistol gas in stock. The only powder I have been able to get it to cycle reliably with is 1680 with 225gr hornady bullets. I tried Lil gun and 4227 with no luck using the same bullets.

Eventually I want to get a smaller barrel and SBR it but this is mainly my hunting rig.

[Guest rebeldrummer]

nice rifle man....300 blk is my next project too.

just trying to find a Zombie lower IN STOCK somewhere.

JoeBobs had them but they sold too quick.....

[Dolomite_supafly]

I ended up building my 300 with carbine gas on 16" barrel and wish I could have found one with pistol gas in stock. The only powder I have been able to get it to cycle reliably with is 1680 with 225gr hornady bullets. I tried Lil gun and 4227 with no luck using the same bullets.

Eventually I want to get a smaller barrel and SBR it but this is mainly my hunting rig.

Those powders are definitely too fast, they are even faster than 1680. I think 4198 or 2015 may work with the carbine length gas system and heavy bullets. Well not so much heavy bullets but bullet with a long bearing surface to keep pressures up. My 240 grain cast use the exact same data as 220 SMK's.

Something about 1680. It may run guns very well but it has a cost. It is the most inconsistent powder I have ever measured. I am getting very large ES's and SD's. And it shows on paper and on the ground. Groups are 4"-5" at 50 yards with both an AR and a known shooter with other powders. On the ground the casings are scattered all over and can have as much as a 10' spread on the ground. Different powders launching bullets at the same velocity will drop the empty cases within 6" of each other and it also shows on the targets.

1680 may be another reason AK's are inaccurate when shooting US made ammo. I have been told that most US makers of 7.62x39 use 1680. And with the results I have seen with the 300 I can see the same problems with 7.62x39.

If you can make it to Knoxville you are more than welcome to burn some of my powders to figure out what works and what doesn't in your AR.

Dolomite

[Guest TNBrat]

I want one! Wow, that's nice. Just on an aesthetic pov, it's too hot. Does it shoot as nice as it looks? I've only put a couple of rounds through my Dad's & it was super fun, but I'd love to get my, washed, sanitized, & gloved (wouldn't want to get ugly prints on it) hands on that. Does Sour Kraut get to shoot it? I hope she does & beats you in a competition. Sorry, it's a girl thing. Competing with JTMaze is part of what makes shooting fun

Sent from my iPad

TNBrat Hiding in the woods…

[Dolomite_supafly]

She does shoot better than I do with most guns, especially handguns. And yes she has shot this AR on several occassions. She likes the caliber because it isn't a heavy recoiling caliber and doesn't have the muzzle blast of a 223 AR. It runs great and now I am just trying to find some handloads it likes.I will be submitting the paperwork for a suppressor soon and when that comes back I will build a can for it. Then the gun will be QUIET, as in slinghsot quiet.

She also has a 9mm AR that is hers. She also has a bolt action in 45 ACP that I made her that she really likes. Not really sure which gun is her favorite she really likes the Taurus 24/7 OSS/DS we have as well. She shot a perfect score on her HCP with it. She carries a Talo Ruger LC-9. It is engraved and nickel finished.

We need to hit the range again.

Dolomite

[Slpeod]

I run the pistol length with a 3 way block. That way I do not overgass my gun with supers and I can run really mild subsonics. As a matter of fact I was shooting some 180 bullets earlier and they were cycling and locking back. I did n't notice a supersonic crack so they are likely subsonic. That would never happen with a carbine length gas system. I can also tone down my supers. Rather than have a 150 grain bullet at 1,800 fps I can switch my gtas block to subs and shoot the same bullet at probably 1,400 fps. This is veru important to me because I am recoil sensitive because of an accident.

One advantage to the carbine length system is if you find a subsonic load that works you don;t need to fool with an adjustable gas block. Problem is getting a load that has enough pressure to cycle a carbine length gas system AND stay subsonic. The easiest way to increase pressures without increasing velocity is to use heavier bullets. I shoot 240 grain cast bullets, which are equal to 220 SMK's, in order to keep the pressures up. I suspect a combination of slower powders, to keep pressures up, and heavy bullets, to also keep pressures up, are what is needed for a carbine to cycle with subs.

Dolomite

Looks good - did you modify the block yourself? I was trying to look at it under the rail but couldn't make it out.

[mikegideon]

I run the pistol length with a 3 way block. That way I do not overgass my gun with supers and I can run really mild subsonics. As a matter of fact I was shooting some 180 bullets earlier and they were cycling and locking back. I did n't notice a supersonic crack so they are likely subsonic. That would never happen with a carbine length gas system. I can also tone down my supers. Rather than have a 150 grain bullet at 1,800 fps I can switch my gtas block to subs and shoot the same bullet at probably 1,400 fps. This is veru important to me because I am recoil sensitive because of an accident.

One advantage to the carbine length system is if you find a subsonic load that works you don;t need to fool with an adjustable gas block. Problem is getting a load that has enough pressure to cycle a carbine length gas system AND stay subsonic. The easiest way to increase pressures without increasing velocity is to use heavier bullets. I shoot 240 grain cast bullets, which are equal to 220 SMK's, in order to keep the pressures up. I suspect a combination of slower powders, to keep pressures up, and heavy bullets, to also keep pressures up, are what is needed for a carbine to cycle with subs.

Dolomite

You have the ultimate in flexibility, something I knew I wouldn't have when I selected carbine gas. When I move into subs, I'll start with a box of Remington factory loads and make sure the gun runs. Then, I'll try to find a sub load that works. I have relied on AAC a lot, since they were able to work "in house" with Remington. I'll be happy with one good sub load. I don't plan to cast anything, which adds more complexity. I'll use SMK's or equivalent. AAC's recommendation for a sub load...

• R-P 300 AAC BLACKOUT brass

• Remington 7.5 primers

• 11.2 grains of A1680 powder (Adjust powder charge down as needed. Factory ammo is 1010 fps for 16" barrel)

• Case length is 1.368 +0.000 -0.020

• Sierra 220 MK loaded to 2.120 OAL (this length is optimal for reliable feeding from USGI magazines)

• Chamber pressure 21,100 psi.

[Dolomite_supafly]

Looks good - did you modify the block yourself? I was trying to look at it under the rail but couldn't make it out.

Here are pictures of the block the day I got it.

The only modifying I did was to make a new adjustment. The adjustment would get gummed up and a little rough to turn with cast bullets so the slot started gettting stripped out. So I bought some 1/2" setscrews and turned them down and made a new adjustment. Now I can use a 1/4" allen wrench and there is very little chance of it getting stripped out. I don't have pictures but you can see it through the handguard. I also drilled small dimples in the block itself and marked it with paints so I don't forget which setting is which.

The gas port in the barrel is what is used to meter the subsonic. It is drilled at .093" to ensure 100% reliability.

It has three settings, off-subsonic-supersonic.

The off position is obvious, it is block completely off for the ultimate in quiet operation with a can.

Subsonic is a wide open position. It has ports in the gas adjustment that are ~.110" so it lets all the gas from the .093" gas port in the barrel through without being metered. I can shoot subsonic 180 grain bullets or my 240 grain cast bullets at 800 fps.

Supersonic meters the gas from the barrel port with a port in the gas adjustment that is ~.070". This lets enough gas through to cycle without overgassing the gun. In this setting I need my 240 grain cast bulelts to be above 1,400 fps to cycle it.

The gun will run supersonic ammo in the subsonic position but the brass suffers with ripped rims and galling.

It works great and has a few added bonuses with the adjustments. If I don't want to shoot light weight bullets at max fps I can switch the setting from supersonic to subsonic and use much lighter loads. Those lighter loads will still cycle because they are no longer metered by the supersonic setting. So rather than have a 2,000+ fps load I can probably use the same bullet at 1,600 fps and still have it cycle. This will also allow me to tune a specific load for a specific trajectory.

Dolomite

[mikegideon]

It would be cool if you could bring a knurled knob through the handguard.

[Dolomite_supafly]

It would be cool if you could bring a knurled knob through the handguard.

I was going to but there is no way I could turn it when it gets gummed up. It was very, very difficult with a standard screw driver. It might have worked if I never shoot cast bullets but that is what I primarily shoot any more. At leat 100 to 1 cast vs. jacketed. The jacketed shoots better but it is a lot cheaper to shoot my cast bullets.

Another problem would be putting the "C" clip on the other side to hold it in place after the tube has been screwed in place.

Dolomite

[mikegideon]

I believe I would grumble at the guy that made it.

[samson7x]

Those powders are definitely too fast, they are even faster than 1680. I think 4198 or 2015 may work with the carbine length gas system and heavy bullets. Well not so much heavy bullets but bullet with a long bearing surface to keep pressures up. My 240 grain cast use the exact same data as 220 SMK's.

Something about 1680. It may run guns very well but it has a cost. It is the most inconsistent powder I have ever measured. I am getting very large ES's and SD's. And it shows on paper and on the ground. Groups are 4"-5" at 50 yards with both an AR and a known shooter with other powders. On the ground the casings are scattered all over and can have as much as a 10' spread on the ground. Different powders launching bullets at the same velocity will drop the empty cases within 6" of each other and it also shows on the targets.

1680 may be another reason AK's are inaccurate when shooting US made ammo. I have been told that most US makers of 7.62x39 use 1680. And with the results I have seen with the 300 I can see the same problems with 7.62x39.

If you can make it to Knoxville you are more than welcome to burn some of my powders to figure out what works and what doesn't in your AR.

Dolomite

Interesting point about 1680. I haven't made it to the accuracy stage yet, I have just been testing for function. Unfortunately I dont have a chronograph either.

What charge would you recommend with 4198 and the 225gr hornady bullet? I may try that powder next.

[Dolomite_supafly]

Kind of hard to judge velocity without a chronograph. The only thing you can do is load then listen for a sonic crack.

Hogdon lists the 11.5 charge at 1,068 fps. Personally I have had luck with 10.5 grains being subsonic. In my gun 11.5 grains of H4198 runs supersonic.

I would start out at 11 and see if you get a supersonic crack. Also make sure you are getting impact on target. Then if you are getting a supersonic crack I would drop it by .5 grains and try it again. Again making sure you get hits on target. Continue to drop the charge weights until the supersonic crack goes away or the gun doesn't lock back.

If you are not getting a supersonic crack I would increase it until you do. This will give you a working range for accuracy testing.

The most important thing is to ensure the bullets are making it out of the bore. Having a bullet go supersonic won't hurt you or the gun but having a bullet get stuck in the bore can be very dangerous if you don't catch it. I have stuck a lot of bullets and a single bullet is easily driven out of the bore. Multiple bullets can ruin your gun, your health and your day.

Dolomite

[Slpeod]

Here are pictures of the block the day I got it.

The only modifying I did was to make a new adjustment. The adjustment would get gummed up and a little rough to turn with cast bullets so the slot started gettting stripped out. So I bought some 1/2" setscrews and turned them down and made a new adjustment. Now I can use a 1/4" allen wrench and there is very little chance of it getting stripped out. I don't have pictures but you can see it through the handguard. I also drilled small dimples in the block itself and marked it with paints so I don't forget which setting is which.

The gas port in the barrel is what is used to meter the subsonic. It is drilled at .093" to ensure 100% reliability.

It has three settings, off-subsonic-supersonic.

The off position is obvious, it is block completely off for the ultimate in quiet operation with a can.

Subsonic is a wide open position. It has ports in the gas adjustment that are ~.110" so it lets all the gas from the .093" gas port in the barrel through without being metered. I can shoot subsonic 180 grain bullets or my 240 grain cast bullets at 800 fps.

Supersonic meters the gas from the barrel port with a port in the gas adjustment that is ~.070". This lets enough gas through to cycle without overgassing the gun. In this setting I need my 240 grain cast bulelts to be above 1,400 fps to cycle it.

The gun will run supersonic ammo in the subsonic position but the brass suffers with ripped rims and galling.

It works great and has a few added bonuses with the adjustments. If I don't want to shoot light weight bullets at max fps I can switch the setting from supersonic to subsonic and use much lighter loads. Those lighter loads will still cycle because they are no longer metered by the supersonic setting. So rather than have a 2,000+ fps load I can probably use the same bullet at 1,600 fps and still have it cycle. This will also allow me to tune a specific load for a specific trajectory.

Dolomite

Very nice, I'm looking at a similar setup on the Jp block. Going to have to copy your dimple and marking method. Hadn't really thought about the gumming up being an issue but since I'm ready to make the move to do some casting I guess I'll have to do some testing.

Sp

[shaftbass]

Very nice rifle D_SF!