Update on the 22 Cheetah MkI

[sundog]

Trials and tribulations. Non groups and case separations. Brass that wouldn't form properly. Well, I was gonna rebarrel to 22-250, but decided to shoot the brass I have left one more time since its formed. Well, after today, I'll load some more of it because I shot a nice little sub one inch hunert yard group of ten shots. Hdy 75 gr BT over 41.0 Rl22. A while back 39.0 H4831SC yielded promising results. Guessing velocity at 3000. Will play with this some more. Sure not much out there on this cartridge for help, but thangs are lookin' up, finally.... sundog

[Scrounger]

Trials and tribulations. Non groups and case separations. Brass that wouldn't form properly. Well, I was gonna rebarrel to 22-250, but decided to shoot the brass I have left one more time since its formed. Well, after today, I'll load some more of it because I shot a nice little sub one inch hunert yard group of ten shots. Hdy 75 gr BT over 41.0 Rl22. A while back 39.0 H4831SC yielded promising results. Guessing velocity at 3000. Will play with this some more. Sure not much out there on this cartridge for help, but thangs are lookin' up, finally.... sundog

Any kind of gunsmith can set that barrel back and rechamber it for .22-250 or .22 Swift. The few good groups you see are a function of the barrel and proof of its' quality. The bad groups you usually get are a function of your cartridge's ignition problems and inconsistency. Only thing I can think of to try that might work is magnum primers. Considering how much powder you have in there, a magnum primer might give you better ignition.

[swheeler]

The chamber is already larger in diameter than either the swift or varminter chambers! I think it would take a new barrel, unless it was a straight cyl bull barrel that could have the CHeetah chamber cut off, then threaded and rechambered, but you would loose a couple inches barrel length. I believe it was designed on the 308BR case(small primer pocket) in a search for improved accuracy, and read somewhere that very few powders were found that would give consistent velocities(ignition) seems like it was H380 and maybe 4320? Even if SD is forming brass out of 243 W/large primer pockets maybe faster speed powders would yeild better accuracy? Just like a steer, never quit trying!
Scooter
CH capitalized- jim Carmichel and fred Huntington

[sundog]

Scooter, 10-4. Had several more almost case separations a couple days ago, 4 out of 5 to be exact, and I stopped right there. This has turned into more problem safetywise than I am willing to deal with. All the brass was trashed. Rifle is going to smithy this morning for a rechamber (if possible) to 22-250 which there may not be enough metal to do that. If not, the barrel will be sold - could be rechambered for same or the Mk II with a different shoulder angle. Making the brass is just a whole lot more than I want to mess with - rifles are made for shootin'. Won't be giving up much if it can be rechamber velocity wise, so no problem. If rechamber is not possible it will still be a 22-250 with a 14 twist and minimum chamber (could even be a cast boolit shooter then!). We'll see.... Safetywise, it'll be far better than what I'm dealing with now. sundog

Looks like I have a set of RCBS .22 CHeetah Mk I dies (FL size and bullet seat) and maybe a barrel for sale.

[swheeler]

Sundog; PO Ackley had a good idea with his line of improved cartridges, easy fireforming and some calibers give excellent velocity increases. The 257R and 7x57 gives velocities beyond what should be possible with their modest case capacities. I have experienced 300-350 fps gain with 7x57AI and 140 gr bullets, pressures are close to the standard cartridge. I know the gunrag experts say it isn't possible, BUT-been there,done that! One step slower powder and a 9-10% charge increase-300 fps increaseIMPOSSIBLE(chamber shape?)

139 gr SST @ 3050 case looks like a starting load-moa accuracy
Scooter

[sundog]

Scooter, thanks for the interest and ideas. The gun is now at the smithy with instructions to 1) rechamber to 22-250 if possible; 2) rebarrel to 22-250, but call me first to discuss. Nothing like a work in progress, huh? I'd really like to keep the barrel I have and continue to shoot the 75 gr Hdy AMax. It has 8 1/2 twist. sundog