Cast Only Rifle Cartridge.....452 diameter, WSM parent

[Geppetto]

Gentlemen,
I have been doing some research on a project, and I am hoping for some input. Long story short, I have a 20” 0.452 barrel blank and I would like to build a rifle/carbine out of the blank. I want to go with a dedicated CB cartridge. I decided to go this route because I am getting set up for casting, and will be casting for 45 acp and hopefully soon 45 colt/454/ possibly 460 S&W. By going with a .452 rifle, I can use the same molds across the board. Because most “45” caliber rifles are 458, rather than 452, I’ll need to do some basic “wildcatting” to get the cartridge I want (unless I’m missing something, please let me know). I don’t want to go with a rimmed cartridge or belted cartridge, so that I need to go with a fat parent case to head space off the shoulder, which leads to the 404 Jeffery based cartridges, such as a 300 WSM. So what I want to make amounts to a 452 WSM.

The intent of this cartridge would be shorter range shooting. Some target, mostly white-tail and perhaps hogs on occasion. I doubt I’d typically be shooting it much more than 100 to 150 yards. I’d like to experiment with boolits in the 250 grain to 350+ range. The barrel blank has a twist of 1:16. I’d like to keep it to lower pressures and velocities maybe in the 1500 to 2000 range. If I can shoot ~100 yards without 3 feet of hold-over, I'd be happy.

So my questions are:

1) The WSM case should have similar volume to a 45-70 (WSM = ~79 grains of water, 45-70 ~75.5 grains water). Any problems with this case capacity for a moderate to low pressure round?
2) Any thoughts on this twist rate? Too fast?
3) Any specifics for cutting a chamber for cast boolits (long/short throat, tight or loose chamber, etc?)
4) Anything I’m overlooking?

Thanks for any and all help and input. I'm relatively new to the forum, but have been lurking steadily for the past several months.

Greg

[Whiterabbit]

twist rate is too fast for 45 acp class bullets, 300 is right there. So is 400+. I can shoot 300-740 grain bullets in a 1 in 16. 200 too, but only if I load trailboss.

My thoughts. make sure the throat is LONG. It's really nice to be able to shoot biggies and have the case capacity too. That's your cake AND eating it. big bullets take up LOTS of case capacity after seating.

wsm brass is thick as hell.

[Whiterabbit]

Other parents are

338 lapua
375 ruger basic

I think everything else is belted or rimmed or EXPENSIVE.

Might also consider 458 socom or a 50 beowulf wildcat. I bet 50 beowulf is easier and easier to come by as time goes by.

I'm a fan of bigger is better. the bigger the case, the easier it should be to get to 2000 fps at low pressure.

Also easier to cut down than to stretch brass! Apparently 458 ruger already exists. Might be worth checking out.

[FrankG]

I made one several years before 450 Marlin was intoduced . Based it on the 458 American but went with standard 45-70 length of 2.1" . I used 7mm mag and 338 mag brass cutting it off at shoulder to trim to 2.050" . I first used a .452 barrel I picked up at G.S. , used a 30-338 and 45-70 reamer to cut a chamber . All was well but twist was to slow . I think it was meant for a replacement BP barrel or some such . I redid it but this time with a Douglas barrel blank I picked up at G.S. , turning it down to a super heavy sporter like contour. I did some dinmention checking and found that a 300 Win mag reamer would cut my chamber , and I had one . It worked slick after I hogged some of chamber with appropriate drill bit to make it easier on finish reamer.
I use 45-70 starting loads to work from and shoot 385gr -535gr cast . When I started it was real work to load them but then Hornaday made dies for the Marlin .
Action is a '95 Oviedo (Mauser) bolt action . Just had to open bolt face and tune extractor to feed from magazine.

[Artful]

Have you examined the 450 Bushmaster, it uses .451-.452 bore. - They designed straight wall and to work within AR15 platform but similar performance as you specifiy.
69818
69819
http://en.wikipedia.org/wiki/.450_Bushmaster


Based on the "Thumper" concept popularized by Jeff Cooper, the purpose of the cartridge was to provide guaranteed one-shot kills on big-game animals at 250 yards, using a large-bore (.44 cal or greater) cartridge in a semi-automatic rifle. . . . .
Ballistically the round is very flat out to 200 yards. If the firearm is zeroed at 150 yards, the user can expect to see a rise of 1.8 inches at 100 yards, zero at 150 yards and a drop of 2.4 inches at 200 yards. This rifle has a free floating barrel making it extremely accurate—it is capable of sub 1 MOA.

[Geppetto]

Thanks for the responses guys.

450 bushmaster is certainly an interesting cartridge that I'll take a look at, especially for a potential AR upper build in the future. I hadn't realized it was a 0.452 bore. I would lose case capacity and some OAL on the bushy vs a 452 wildcat. I'll have to do some math/drawing and decide whether it matters or not. I suppose that I could also look into a 458 socom and just size it down a couple thousands.

Because I am not building this on an AR-15 platform, I'd like to try utilizing the extra case length and capacity I can get away with for a lower pressure cartridge which may be advantageous when launching boolits. And I think i'll continue on the 452 WSM/Ruger path just for the fun of it.

Thanks again!

[Whiterabbit]

I wanna see it when you are done with it :)