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anyone built a 22-243 middelstat?

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Looking to build my first 'wildcat' coyote gun.
My primary coyote tools are a 257 wby mag and 17 hmr. One is too voracious for pelts, the other too limiting.
Looking to bridge the gap with this fire-breathing speed demon (4400-5200 fps). Any of the fine folks on-board here have any words.
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varmastr

Aren't you worried about throat damage/erosion with that kind of velocity? I don't know anything about the 22-243 specifically. My question is based on experience with other very fast cartridges.

Also, what kind of bullet will hold together under the rotational stresses at 5000 plus fps?
 

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Discussion Starter · #3 ·
according to accuratereloading.com and some other sites this is a fairly stable round with acceptable throat life.
A local gunmaker has the ability to employ gain twist rifling. Gain twist rifling starts at 0 twists per inch and gradually increases to 8 or 9 twists per inch at the muzzle.
a 30 gr. berger bullet was used for 5200+fps.
realistically, once sighted in, a 'busy' coyote only hunting rifle will take years to cycle through 1000 rounds. a more 'realistically acceptable' velocity would be around 4600-4800
 

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Discussion Starter · #5 ·
yes sir, it is, the 22/308 is commonly refered to as the 22 cheetah, my megre learnings tells me that they both are only microscopically different. velocities...(with shoulder angles being one of the bigger differences)
 

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"...the 22 CHeetah (Carmichael-Huntington) is the Remington .308BR case (with small primer pocket), necked-down and fireformed to less body taper. During the fireforming process, the shoulder angle is increased to 30 degrees and moved foreward for a .224-inch neck length. The end result is a wildcat with about ten percent more case capacity than the Winchester 220 swift case."
...from the Hodgden data manual no.26.

I have a rifle that I had built on a Ruger action to chamber this cartridge. What I was trying for was a high-intensity 22 for coyotes and varmints. I wanted to shoot the middle-to heavy range of 22 bullets, 55gr and up.

The rifle was set-up with .250 neck and 1-in-9 twist. This "fitted neck" results in a fired case that requires the absolute minimum of neck sizing to reload. This is no small concern when you have as many hours into case preparation that even the most easily formed wildcat will require. This is, of course, part of the fun.

After 18 months of effort on the part of myself and my gunsmith trying to get the piece to shoot the way I wanted it to, not including case-forming and preparation, what I wound up with is a modified 22CH Mark II (sort of a cheatin' cheetah, mk3).

The first thing that went out the window was the 308BR case. It may work in southern california (warm/hot and dry) but here in the northwest the large charges of slow burning powder I use require a large rifle primer. I have settled on CCI BR4 primer. I went with standard, large rifle primer pocket Remington 308 Win cases 308 Win because I wanted to have enough neck wall thickness to work with and Remington brand because they were what was available when I was ready to get going. If I were looking for ultimate accuracy I'd have gotten Lapua or Norma brass; still might down the road.

We wound up extending the chamber throat .100"; the cheetah is set-up for light bullets consequently I was having to seat the longer bullets too deeply into the case. The gun absolutely will not shoot MOA with the bullet touching the lands; .050 off is the magic number here.

It took me 3 months to detail 500 cases for varminting. I still have yet to fire-form about 100 of them. The others have been around the block a few times.

Load development was an excruciation but I learned a heck of a lot along the way.

My pet load is 48 grains of WMR powder/77gn sierra bthp match bullet/CCI BR4 primer. This results in about 3800 fps mv.

I have hit many a prarie dog, out to 800 yds, 1-shot, with this load. The gun will also shoot win 64gn psp bullet well; The hdy 68 match and sierra 69 gn match bullets do very well also. All the varmint bullets I have tried disintegrate within 100 yds of the muzzle (or shed their jackets) after a few fouling rounds. This looks kind of cool to my spotter, but is not conducive to hitting anything, to put it mildly.

No coyotes yet, but that's my fault; don't see many 'yotes from the reloading bench.

If I had it to do over again? I'd build a fast-twist (1/8 or 1/9)
22-250 or 220 swift, with an extra-long throat, and shoot heavy bullets. If I wanted another fitted neck, which definately improves case life, I'd go with a minimum-dimension SAAMI spec reamer and have my sizing die cut using the same reamer and use 250-3000 cases and turn the necks to the appropriate thickness.

I would also recommend a subscription to precision shooting magazine and a heap of reading on the subject.


EDIT: That's 0.005 off the lands, not 0.050.



 
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