Dan,
I read something on that one time and the article mentioned that there was a fair amount of throat erosion after 100 rounds alone.

a 22/257 Weatherby: the barrel would not outlast the pound of powder you reloaded your first cases with.

the 6mm Apex ( or 6mm/ 300 H & H) was mildly comparable and it had mass throat erosion also at around 100 rounds.

HOw extreme does this get???

Cheers
seafire

Isn't the 220 a semi rimmed case? I forget. I thought it was based on the 6mm Lee Navy. In any case, I believe the improved 220 would have about the same case capacity as the 22-6mm, or pretty darn close. I use a 22-243 Middlestead, about the same as the CHeetah Mk II. Really, at this point in time with todays powders, you can only go so far in small bore/big case combo's. FWIW - Dan

.225 Winchester is rimmed



The Sierra manual has the case length of the Swift at 2.205 inches which is 56 mm. The base dimension is .473, just like any other 308/30-06/7&8 mm Mauser based cartridge.



One of the improved Swifts was the .220 Weatherby Rocket. There was in article on this cartrige in the October 2003 Handloader. According to the article the Rocket holds 50 grains of water compared to the Swift's 48 grains. If you wish to read it I can scan the article.

pdawg,

Welcome to the forum.

I am sure someone has doen this before, and probably made all sorts of claims for it too.

But, I can tell you, from our own experience, that the largest case one can use, with a reasonable level fo success, is the 243 Winchester necked down to 22.

There are many versions of this, like teh 22-243 Midlestead, 22 Cheetah etc.

We have built several rifles for this wildcat, and all of them surpass the 220 Swift in velocity.

We have also tried necking down the 6mm Remington down to 22 caliber, and found that we had to use more powder to get the same velocity as the 22-243.

You can compare our data for these two Reloading pages .

>If I remember right the .220 Swift, 6mm Rem and .257 Roberts all use the same parent case. THe 7x57 Mauser.
.220 Swift's parent case is the 6mm Lee Navy

I built a .22-284 back in the early 1990s, and wasn't that impressed. It was fast, but for all the powder it burned and barrel it eroded, I concluded that you're better off with a Swift (I could only beat the .220 by 100-150 fps).

Lee Martin
www.singleactions.com