300 BLK and pistol position gas blocks

[mstarling]

Guys,

Am reading in other forums that the 300BLK will work nicely with both subs and supers using a carbine length gas system. These same reporters seem to say that we can expect pistol position gas systems to be over gassed with the 300 BLK.

I am having difficulty quite believing that the additional throat in the 300 BLK will obsolete by rifle which is a TP555 built 16" bbl with his three way gas block in the pistol position. Am I just being stubborn and have a bad surprise waiting for me? Or is there a lot of noise in the air just now?

Mike

[rsilvers]

Well more specifically what people were saying is that if you set the gas port to be large enough to work with very fast powders on subsonic loads, then it will be more over gassed when you shoot supersonic ammo than if you set the gas port size to be correct for Remington subsonic ammo which generates more gas port pressure than some of the faster powders.

And if you just set the gas port to be the correct size for Remington subsonic ammo, then you might as well use a carbine gas port as at that length the gas port size is well under the 0.125 max.

Generally one always wants to use the longest gas system that meets the cyclic rate target as it adds delay to the bolt unlocking and that improves reliability. This is why mid-length gas for 5.56mm is better than carbine gas for 5.56mm.

"I am having difficulty quite believing that the additional throat in the 300 BLK will obsolete by..."

It is not the throat, it is the Remington subsonic ammo being designed to provide more reliable gas pressure for an AR-15 than many of the load recipes floating around which are best for bolt guns.

[BWE Firearms]

Have you done any testing with the Blackout Ammo in an AR with the port in the pistol position that has had the chamber opened up to Blackout specs. I have two AR's chambered in 300-221. One with a carbine gas system one with a pistol gas system. I was going to start doing some testing to determine new gas port sizes but if you have already done it would you share the information.

I think the Blackout package in an AR will be more reliable then a properly set up Whisper AR but you will be able to get the Whisper quieter because you can use faster burning powder and still have it cycle. I can see the advantage of both approaches but for what I want to do with it I think I want to use faster powder to get it as quiet as possible. On the other hand putting a short barrel suppressed upper on my M16 lower and have it run reliably in full auto would be a ball.

After getting the sales literature on the short Blackout upper some of the changes you made to the chamber and powder decisions make a lot of sense. I didn't realize how hard you were targeting the military, police, full auto markets. It also made a lot more sense when I had a friend call and remind me the military is getting ready to hold new carbine trials. I don't remember what the military was looking for but it had to be a short barrel as this is what everyone has been introducing recently. I hope you guys get the contract so we can start getting cheep ammo.

[mstarling]

From the response so far and from the comments of tp555 on the amount of material removed from the chamber in updating it, one could assume that an existing rifle with a pistol position gas system should be able to run fast pistol powder subsonic loads as it always has and even supersonic loads if built with the same powders previously used with the rifle.

The interesting question is: Can the 220 gr factory subsonic load be used in such a rifle and have it function?

(BTW: My 16" upper runs fine on a registered M16 lower w supersonics. Haven't tried it with subsonics as the Form 4 for the can has not yet cleared.)

[Titleiiredneck]

Originally Posted by mstarling

From the response so far and from the comments of tp555 on the amount of material removed from the chamber in updating it, one could assume that an existing rifle with a pistol position gas system should be able to run fast pistol powder subsonic loads as it always has and even supersonic loads if built with the same powders previously used with the rifle.

The interesting question is: Can the 220 gr factory subsonic load be used in such a rifle and have it function?

(BTW: My 16" upper runs fine on a registered M16 lower w supersonics. Haven't tried it with subsonics as the Form 4 for the can has not yet cleared.)

I am more interested in seeing if a under <-- 8" barrel can be made to run with subs "only" in the blackout.

[tp555]

Originally Posted by Titleiiredneck

I am more interested in seeing if a under <-- 8" barrel can be made to run with subs "only" in the blackout.

Yes it can .Requires some R&D.I have made 9mm 7 1/2" barrels that cycle using the gas system. Also made some 9x18 makarov barrels for a customer.Some people like to play with such things and figure it out. I just make the barrels for them.

[JFettig]

Originally Posted by Titleiiredneck

I am more interested in seeing if a under <-- 8" barrel can be made to run with subs "only" in the blackout.

I don't see why it couldn't be done, I've made a few 7" 30-221 barrels.


Jon

[rsilvers]

We have a 7 inch 300 AAC BLACKOUT that works fine.

[Titleiiredneck]

May have to look into this further when ammo drops below or is almost the same as reloading 300/221. I may get spook or tp555 to run a barrel off then. Wouldnt mind a side charger with a 7 or less barrel and a adj block

[rsilvers]

I will post photos of my 7 inch tomorrow.