AR Sponsor
Posted: 12/11/2009 12:47:19 PM EDT
|
Question. What's the overall diameter for the dedicated 22LR barrels, at the breech?
|
|
Quoted:
So there's only 0.1365" of support around the chamber. Is that OK/safe for ~25Kpsi? yes CMMG collar is only .460 Id so I would think the Spikes,Ciener and Model1 would be stronger since they are .498 - .502 Ive never heard of any problems yet with any of them in that area. |
|
frog5215: Well, you do have the whole collar, too. But have you ever looked at the thickness of the cylinder walls of an NAA mini pistol?
2 points, they are about a micron thick....I had one, it shot great. Not much value for self defense in the places I roam. 
Spec |
|
Quoted:
But have you ever looked at the thickness of the cylinder walls of an NAA mini pistol? That is true, but probably the total number of rounds each of those sees in a lifetime, is lower than the one of a range session with a 22LR AR15 
Probably nothing to worry about, but it just looked on the thin side as a chamber area support. |
I have two DPMS dedicated uppers and they use the same diameter barrel at the breach as the CMMG and they have plenty of steel left in the barrel to support the chamber. I had the end of one barrel peen out from repeated dry firing due to not counting rounds with 10 round mag. I just can't count fast enough on those mag dumps even with 10 rounds  . I'm glad I modified this rifle to use BDM 25 round mags with BHO follower. My calipers show the barrel wall to be .165 not including the slot cut out for the extractor. The CMMG collar fit the barrel on my DPMS M-4 dedicated 22 upper and works great after opening extractor slot to accommodate Ciener bolt.
|
|
Did some calculation considering 416 SS strength, plenty safe:
Online Pipe/Chamber Pressure Strength Calculator Peak tensile stress is about 37800psi (considering a 25000psi chamber pressure), against a yield tensile strength of about 75000psi for typical 416 SS. |
|
Compass Lake does the same trick with Douglas barrels for M-261 bolts. Barrels for Service Rifles and Space Guns are about $300, the bolt with CLE's "collar equivalent " is $240. Other lengths $50 extra.
Mine wants to shoot one hole @50yd, but I restrain it to the 3/8" level of accuracy. |
|
Quoted:
Compass Lake does the same trick with Douglas barrels for M-261 bolts. Barrels for Service Rifles and Space Guns are about $300, the bolt with CLE's "collar equivalent " is $240. Other lengths $50 extra. Mine wants to shoot one hole @50yd, but I restrain it to the 3/8" level of accuracy. Any chance you could post a pic of the CLE collar equivalent? I've got an M261 that needs a job. |
|
I'll have to hunt the pic.
Basically it's a lug that replaces the chamber adapter, and fits in a recess on the left side of the dedicated CLE barrel. If you're getting a CLE barrel, the part is $40. The breech is otherwise a lot like the AS ones pictured, except for a big scallop/flute on the left to accept the connecting link, which keeps the bolt captive for removal on cleaning. |
|
Left is Colt/DPMS, right is Ciener. The Ciener looks just like a Kuehl MKI.
IIRC AS will do barrels for any conversion bolt- like Air Force and M-261 I guess would fill out the roster My CLE is on my post of 7-25-09 (currently page 35 Pistol and Rimfire). I would cut & paste, but I'm not smart enough to do that on this computer. The connecting link fits the mortise on the right in the picture (left in the gun). It's seen (badly) on the far side of the assembled bolt. |
|
None. I got a $98 CMMG upper from CTD, stuck the barrel in, screwed on the handguard, dropped in the bolt, slapped on a scope, and went shooting.
For the AS Ciener setup, I suspect the tabs on the conversion rail have to be ground off, for theColt/DPMS, it looks like the bolt is screwed to the barrel. I THINK, the M-261 bolt is attached to AS's barrel by a pin or setscrew. Ballistic Advantage is doing dedicated Douglas barrels that work with standard Spike's, M1S, and Ciener bolts( with the dedicated collar). Folks, they're just ARs, the parts screw together the same way. The only significant difference is the part of the Brownells action vise that sticks inside the upper to prevent crush/distortion has to be drilled out in front to accept the breech stub of the .22 barrel since it sticks so far into the upper. It's glass filled nylos and drills easily. Oh, yeah...NO GAS TUBE TO FIDDLE WITH. I built one on a 9MM flat top for the slick side look. Forward assist has nothing to push on on a .22 bolt anyway (unless AR-fan has had ahold of it). |
|
Here you go frog5215 I'll try and cut and paste the thread on your barrel....................................
Quoted:
This showed up in the mail Thursday. 18" SPR barrel for a .22 MK12 Mod 0 I'm building in .22. The can is fake, just a thread protector until I get a flash suppressor. The handguard is until I come up with the cash for the PRI. Frank White does really nice work. We'll give it a try tomorow, plain and probably with a Spectre. The Bob Sled is a single shot adapter; the plunger pushes up the bolt latch. http://img36.imageshack.us/img36/9985/img1997y.jpg http://img156.imageshack.us/img156/7550/img2001h.jpg http://img190.imageshack.us/img190/4931/img2002c.jpg http://img35.imageshack.us/img35/144/img2004k.jpg http://img35.imageshack.us/img35/3788/img2007f.jpg |
|
Thanks, Vascar.
This is for the M-261 bolt. If I can get my kid here tomorrow we'll do a better picture of the connecting link. CLE feels the M-261 is the most accurate and reliable conversion. Since they do mainly Service Rifle trainers and Space Gun trainers (when not covered up with .223 match guns), this makes some sense. There are some advantages to the M-261 in this role. This bolt uses 10rd mag inserts that go into unmodified USGI 20rd and 30rd mags. Like everything else except the Air Force conversion, it doesn't lock open on an empty mag with the .22 mag in place. HOWEVER, with a USGI mag in place WITHOUT the insert, it will lock open. BFD, you say? Well, it does make it possible to single load the gun, with the shell holder supplied or easily fabricated. Same deal with the BobSled. This is nice for slow fire; the gun is empty and locked open after each shot. I can't say enough nice things about this barrel. I've wanted to do a nice write-up, but between waiting for a calm day, work, and hunting season, I've been unable to generate the targets I feel this thing's capable of. Before I found my AccuWedge, on a calm day shooting SKMatch @ 50yd, I'd get 3in one hole and 2 in another, opening the group to a half inch or less, or a little more. One pretty good afternoon just playing I tagged a 4" round swinger 8/10 @200yd, then 4 for 4 (end of a box). It's built up as a MK12 MOD 0, PRI Gen III handguard and gas block/flip up, SWAN sleeve an rear sight, ARMS lever lock rings, a Chinese knock off 3 1/2-10X40 side focus 30mm scope. I normally shoot it with a Spectre. CLE will do other barrels(customer supplied), but I was so pleased with a 21 1/2" Douglas Jim Clark sent me for my 10/22 18 or 20 years ago I saw no need to look further. |
AR Sponsor