I have a long-action rifle chambered in 300WSM. It does not feed so well. I am thinking of creating a wildcat based on the 300RUM shortened to .30-06 length. The base datum diameter of the WSM is .555 inches. The base datum of the 300RUM is .550 inches. My question is how much of the barrel do I have to cut off to get the diameter of the chamber down to such a size that I can cut the chamber for the wildcat? I believe the diameter of the WSM is .5381 at the top of the body.

Cartridge Creator courtesy of ammoguide.com

HB,

Probably simplest thing to do is put a micrometer on a piece of once fired brass from the gun in question.

Drawing it out the lines lay on top each other. I would wonder if you need to set it back at all. .005 would about the thickness of a piece of paper then split it for the difference on each side. Your brass will vary more than that.

Pour a chamber cast and mike it. Locate the diameter you need and cut it .250 ahead of that.

quote:

Pour a chamber cast and mike it. Locate the diameter you need and cut it .250 ahead of that.

That is a good idea. Never thought of that. Thanks!

Ever hear of a .300 Dakota?

quote:

Ever hear of a .300 Dakota?

Yes. I have looked at it on ammoguide. It is close to what I want, but its base datum is .010 too small and its shoulder diameter is .007 under the WSM. I want something that has more powder than the 300WSM but not as much as the 300RUM. Throat erosion is a major bugaboo of mine, given that barrels and their installation cost an arm and a leg. The neck on my proposed wildcat is .400 inches long, to reduce throat erosion. The neck on the 300Dakota is .310...

http://ammoguide.com/?catid=258

If Winchester has just made the WSMs with the common .550 base datum, my job would be so much easier. Below is a visual comparison of the cases from which the wildcat might be made. Ignore the 223, 30-06 and 300WSM; they are there just to give some scale to the others...

Visual comparison courtesy of ammoguide.com

seriously?
set it back and rechamer for 300 winmag -
OR rechamber for 300 rum and down load it

you are looking at 1000 bucks to pay for reamers, custom dies, and gunsmithing

2.55" is the case length of the ARs, and what you are looking for is the 300 AR -- but it didn't offer a thing that wasn't already available 10X over..

If you can't kill it with a 300 winmag, you need a .4++

quote:

Originally posted by homebrewer:

quote:

Ever hear of a .300 Dakota?

Yes. I have looked at it on ammoguide. It is close to what I want, but its base datum is .010 too small and its shoulder diameter is .007 under the WSM. I want something that has more powder than the 300WSM but not as much as the 300RUM. Throat erosion is a major bugaboo of mine, given that barrels and their installation cost an arm and a leg. The neck on my proposed wildcat is .400 inches long, to reduce throat erosion. The neck on the 300Dakota is .310...

http://ammoguide.com/?catid=258

If Winchester has just made the WSMs with the common .550 base datum, my job would be so much easier. Below is a visual comparison of the cases from which the wildcat might be made. Ignore the 223, 30-06 and 300WSM; they are there just to give some scale to the others...

Visual comparison courtesy of ammoguide.com

If you think barrel switching is expensive, you'll love how much you save by creating a wildcat.........

Can you explain how a longer neck prevents throat erosion? I'm not suggesting it doesn't, I just don't understand how it would......

The long neck contains more of the flame than does a short neck. I read a lengthy article about a man who builds a 6.5mm varmint gun that has a wildcat cartridge that uses a neck .400 long. He says he does it to reduce throat erosion. So I said "OK, I will use a .400 neck."

I have to do some thinking as to how I'm going to do this. I thought about using the 338LapMag shortened a bit, but that would require my boltface to be opened up to .590. It's a .700 bolt, so I'd have just .050 lip on the boltface. No too much, in my thinking. So I thought I'd keep the .534 boltface and cut the barrel to such a length that I can chamber for a new round and keep the barrel. The sticking point of the whole thing is that any gunsmithing seemingly takes years and years to get done. I'll be so old by the time I get the gun back, my fragile frame won't be able to take the punishment of the recoil...

quote:

Originally posted by Mark:
HB,

Probably simplest thing to do is put a micrometer on a piece of once fired brass from the gun in question.

That should work!