18" Barrel

[grunteled]

I'm thinking of creating an upper for my AR using the 300 Fireball chamber and an 18" barrel. I want to do something similar to an SPR look. Stainless with rifle length rails and flash suppressor. This will be a pig/deer killer and I want as much velocity as I can get but not with a 20" barrel.

Does an extra 2" help any with velocity? I'm in a no sound suppressor state so subsonic loads are not of great concern. My real intrest was a .30 caliber rifle that is lower compatible with a standard AR15. Anything special I need to know to build this?

TIA!

[Zed Stewart]

I have a 16" Oly barrel. With no more powder than is used, I do not think an extra 2" of barrel would make any difference velocity wise. You are only using 20 gr of H-110 with a full blown 125 gr load. I loaded more than that for a 4.5" 44 mag pistol.

My upper is a dedicated optics upper with a GG&G GS-1 rail, no front sight, and a rifle-length DPMS free float tube. With this set up, it resembles a short SPR, especially when I have my SS10x42 mounted. It has 4.5" of barrel and flash suppressor sticking out of the front of the handguard.

[Quarterbore]

I was trying to find a source for this but I thought I had read that the 300 Whipser only really requires something like a 13-inch barrel to use up all the powder and perhaps less barrel then that.

As suggested above, we are using very small powder charges in a small case. I agree with the advise above that you are not likely to see much change in velocity by going to a 18-inch barrel over a 16-in.

As far as what to keep in mind, you are at the right place... The big one for you is getting this upper to run with supersonic ONLY loads. That may well make it so that you don't need to worry about an adjustable gas tube but I would be curious if the guys that are here with an adjustable gas system need to generally close down or open ut the gas system to shoot supersonic loads... My guess is that a supersonic load requires less gas flow (smaller gas port) then is required for subsonic loads....

Anybody?

[Zed Stewart]

My 1970 fps 150 gr loads have a fairly violent ejection. Full blown 130 gr loads are much lighter. My barrel has a pistol length gas system. I was thinking about a pigtailed gas tube. It should still cycle with subsonic loads due to having 10", or so, of barrel in front of the gas port. I do not know the port diameter but it has run with subs even when it was brand new.

[grunteled]

As I'm still a newbie on this platform.... does the .300-221 use the same bolt and so forth? I thought I read the only change is the barrel but I wasn't sure. I may go for an adjustable gas system as I may not always live in MO.

I'm looking at AR15Barrels.com since they offer a stainless match barrel and I DO NOT WANT to try drilling and grinding on my barrel as people are talking about with M1 Sales. Anyone know what I can expect accuracy wise from a good barrel?

My plans are for a RRA flat top upper, CH and Bolt Carrier and a Colt bolt. I just added a nice RRA trigger to my host lower and I really like it. I didn't realize how bad the stock trigger is till I felt this thing.

Thanks for the help and input!

[jripper]

Yes, you are right. It does use the same bolt as a .223, and you only need to change barrels.

My Model 1 seems to be running around 1 MOA. From what I hear, most people are getting about the same.

If you get a barrel from AR15barrels, and think you may want to shoot subsonics some day, get the 1 in 8", with the pistol length gas system. You will diffenitely want an adjustible gas system, however. You will also need to figure out a way to get to the gas system, as the gas block will be under the hand guard.

Good luck, and have fun.

[Triggerf16]

Be advised AR15Barrels.com will do all that for you.

1:8" twist, pistol length gas system, JP adjustable gas block, and milling the gas block to fit under a standard handguard.




Trigger