self-built 22lr ar22 dedicated upper..

[pkuptruck]

ok. I have an older M261 22lr conversion unit, and 10 or so functioning magazines.

problem is, most uppers I have are 1:7 or 1:8.. 22lr like the 1:16 or so twists..

I was wondering to myself.. would it be worth it to..
-take a 10-22 take off barrel, standard type
- get it fitted to a regular a3 upper..
- have it reamed out for 5.56 so that the M261 22lr adapter would work, as is.

Anyone familiar enough to know if this is feasible?

[Moleman-]

I also have a M261 kit and mostly shoot it in a 1:12 or 1"14" barreled upper but hate that it isn't as accurate as a off the shelf 10/22 which I don't think are particularly accurate. Why not thread/pin on a bushing that is similar to the barrel extension on standard barrel and turn down the barrel stub so that it is .455" or whatever and made a short "barrel" section that is now just a collar that slips over the barrel stub. CMMG and others have used that style. No chamber work, and you'd only have to make the barrel to receiver bushing and the new "barrel" collar. I like the actual feed ramp of the CMMG type so I was thinking about just getting one of them when they're on sale and making a barrel for it as the upper prices are a bit much for what you get.

[slingshot77]

ok. I have an older M261 22lr conversion unit, and 10 or so functioning magazines.

problem is, most uppers I have are 1:7 or 1:8.. 22lr like the 1:16 or so twists..

I was wondering to myself.. would it be worth it to..
-take a 10-22 take off barrel, standard type
- get it fitted to a regular a3 upper..
- have it reamed out for 5.56 so that the M261 22lr adapter would work, as is.

Anyone familiar enough to know if this is feasible?

It might be feasible with enough machining & custom work.

Might make a good project if you do the machining & fitting in a home shop but would be costly to farm it out, then you still don't know the accuracy potential or other problems that will have to be worked out. The 10/22 barrel probably has a front sight, or at least a sight notch, so the machining would have to be exact to have it match the barrel extension so it doesn't look hokey with the sight or dovetail way off of center. Also the 10/22 barrel might not have enough diameter at the rear to get your .22-.223 adapter to fit properly.

If you want a 10/22 then buy a 10/22 for cheap then add the chassis of your choice. (lot of chassis types available for the 10/22)

If you want the real AR platform to practice with then just build one up on your AR upper or buy a full .22 upper & bolt.

Personally I hate shooting .22 in a .556 upper as the junk .22 lead & dirty combustion plugs the heck out of the gas tube.

Years ago I built a dedicated .22 AR upper using a CMMG .22 barrel & bolt kit & was very pleased with the accuracy & functionality. Very accurate with .22 ammo it likes & very few function problems if kept somewhat clean. I have probably put 50,000+ rounds through it & have no complaints except for the bolt hold open as it uses the mag follower for last round hold open so the bolt slams home when mag is removed for a change (kind of hinders real mag change practice).

You can get a dedicated .22 bolt hold open for the lower that works great & allows mag removal with bolt still held open but that prevents using that lower on a .223/.556 upper.

You can buy a CMMG AR-15 22 Long Rifle M4 Contour 1 in 16" Twist, 16" long Chrome barrel & bolt for about $289.99 at Midway & build a good functioning .22 AR upper. (I am extremely pleased with mine)

I'm not sure that your present mags will work with the CMMG barrel/bolt but Black Dog .22 mags are cheap & need no adapters or gimmicks.

[oldmann1967]

The barrel twist is not the only concern with a .22lr. The .223 barrel is not the correct size in the first place.

.22lr diameter=.223"
.223 diameter=.224"

I would start out there. Also, not sure about you adapter, but the difference between a CMMG adapter and the bolt from a dedicated upper is only the chamber adapter is removed on a dedicated.

[JimSig]

I have a CMMG conversion kit and i found out that shooting it in my AR15 pistol that has a 1:7 twist from and 8.5 " barrel is accurate enough. the difference is probably about a 1/4" at 25 yard from shooting 223 ammo as i use the same red dot that is mounted on the upper. if you do the math a 1:7 twist in a short barrel 8.5" results in 1.2 rotation of the 22LR bullet as compared to 2.2 rotations from a 16 in barrel with the same twist rate of 1:7
Comparing to a dedicated 22LR barrel of 1:16 twist at 16 inch barrel resulting in 1 complete rotation. Conclusion: Shorter AR15 barels with 1:7 twist rates result in comparable rotations for 22LR with a conversion kit.

[slingshot77]

I have a CMMG conversion kit and i found out that shooting it in my AR15 pistol that has a 1:7 twist from and 8.5 " barrel is accurate enough. the difference is probably about a 1/4" at 25 yard from shooting 223 ammo as i use the same red dot that is mounted on the upper. if you do the math a 1:7 twist in a short barrel 8.5" results in 1.2 rotation of the 22LR bullet as compared to 2.2 rotations from a 16 in barrel with the same twist rate of 1:7
Comparing to a dedicated 22LR barrel of 1:16 twist at 16 inch barrel resulting in 1 complete rotation. Conclusion: Shorter AR15 barels with 1:7 twist rates result in comparable rotations for 22LR with a conversion kit.

Jim

Twist rate doesn't work like that as barrel length has no effect on bullet spin as long as the barrel is long enough & rifling is deep & sharp enough to not allow the bullet to strip in the rifling.

1:7 is 1 turn in 7" of bullet travel no matter the barrel length

1:16 is 1 turn in 16" of bullet travel no matter the barrel length

[pkuptruck]

I also have a M261 kit and mostly shoot it in a 1:12 or 1"14" barreled upper but hate that it isn't as accurate as a off the shelf 10/22 which I don't think are particularly accurate. Why not thread/pin on a bushing that is similar to the barrel extension on standard barrel and turn down the barrel stub so that it is .455" or whatever and made a short "barrel" section that is now just a collar that slips over the barrel stub. CMMG and others have used that style. No chamber work, and you'd only have to make the barrel to receiver bushing and the new "barrel" collar. I like the actual feed ramp of the CMMG type so I was thinking about just getting one of them when they're on sale and making a barrel for it as the upper prices are a bit much for what you get.

this is kinda where I was going, mentally. ( really. most my friends think im mental anyway)

isnt the m261 "chamber" gizmo different than the CMMG ? or does their chamber adapter fit on the M261 ?

I know that they are different enough, that CMMG mags wont work.. have to use the M261 type ( black dog make good ones! )

[DrScaryGuy]

Order a barrel blank and start from scratch?
http://www.gmriflebarrel.com/search....rch_query=22lr
If it doesn't work, strap it to a board and get your money refunded at the next Detroit gun buy back.

[JimSig]

Jim

Twist rate doesn't work like that as barrel length has no effect on bullet spin as long as the barrel is long enough & rifling is deep & sharp enough to not allow the bullet to strip in the rifling.

1:7 is 1 turn in 7" of bullet travel no matter the barrel length

1:16 is 1 turn in 16" of bullet travel no matter the barrel length

You just confirmed my observations buddy.

1:7 is 1 turn in 7" of bullet travel no matter the barrel length.. so if the barrel is 7", the bullet will travel 7" and twist one complete turn. And if the barrel is 14" the bullet will travel 2 x 7" and will twist twice. Right..

The bullet travels in the barrel, so barrel length combined with the twist rate do have an effect on how many times the bullet gets to spin before it leaves the barrel..

[slingshot77]

You just confirmed my observations buddy.

1:7 is 1 turn in 7" of bullet travel no matter the barrel length.. so if the barrel is 7", the bullet will travel 7" and twist one complete turn. And if the barrel is 14" the bullet will travel 2 x 7" and will twist twice. Right..

The bullet travels in the barrel, so barrel length combined with the twist rate do have an effect on how many times the bullet gets to spin before it leaves the barrel..

Barrel length doesn't matter (within reason). The spin on the bullet is put on the bullet by the twist rate not the barrel length.

If the barrel is a 1:7 twist & 7" long the bullet will still twist 2 turns at 14" of travel (or very very close to that anyhow). Now the bullet spin does degrade as it travels down range due to air friction but it exits a 7" barrel spinning at the same spin rate as it would exit a 14" barrel or a 32" barrel (assuming the same barrel twist of 1:7 for all barrels).

Using your above barrel length suggestion what is the bullet spin of a S&W revolver with a 1:18.75 twist with a 2" barrel? _____ Your thought would have the bullet not even spinning one complete revolution. How could that bullet stabilize if it isn't spinning?

But the bullet IS spinning because it has a 1 turn in 18.75" of travel put on it at barrel exit. So even though the barrel is only 2"long it has placed a spin on the bullet of 1 turn in 18.75" of travel but it is long out of the barrel before it reaches that 18.75" of travel.

A bullet spins longer inside the barrel with a longer barrel but it doesn't spin any faster in a longer barrel of equal twist rate.