Wildcat: .45 ACP Extra Long?

jkpq45 · December 13, 2012, 11:54 AM

Hello All--Mods, please feel free to move the topic if I'm in the wrong sub-forum.

I'm considering a wildcat cartridge along the lines of .450 Bushmaster using a rimless, headspacing-on-the-case-mouth cartridge utilizing the wide variety of 0.450"-0.454" projectiles available for .45ACP, 45LC, .454Casull and .460S&W Magnum. I could hold pressures to the .450B limit of 38 ksi, but what's the fun in that?

I'd like to use .30-06 brass as the parent case (citing availability as the reason) vs. the .284 case the .450B is based on. I'm planning on installing this cartridge into a single-shot, break-action H&R/NEF rifle receiver to begin with.

The question is--how to fireform? I'm planning on a case OAL of ~2.25". Can I count on the extractor to "hang on" to the case hard enough that it can be prevented from being driven forward by the firing pin during forming? Any chance I can trim the case after forming?

Thanks for the advice--this is my first wildcat to headspace this way, so I appreciate the input.

jkpq45

Scorch · December 13, 2012, 07:51 PM

Sounds like you are talking about a rimless 45 cal version of a 444 Marlin. It can certainly be done, but it will cause you some trouble.

1- Rifles generally do not like cases that headspace on the mouth. The longer cases do not headspace well and can cause issues.

2- Rifle chambers like some taper to them to ease extraction. About .010" of taper. More later.

3- At higher pressures, recoil and bullet backout will become an issue because of the taper crimp. 45 Win Mag rifles were produced, I think they are cool, but I am not sure if they had issues with this.

4- The biggest issue is that brass cannot be made easily from 30-06, you will wind up with a rebated rim case. 45 ACP base diameter is .480" (versus .470" for 30-06/308), and that leaves the brass very thin at the case mouth (.005"-.007" in order to give the needed case taper). You are talking about higher pressure, so you need thicker brass at the case mouth, maybe .012", which will make the case mouth .475" minimum, and your base diameter is .470", so you wil be bulging the brass out to fit the chamber. Problem there, but not insurmountable.

5- For fireforming, seat a lead bullet out far enough so that it engages the lands, that will keep it from being driven forward when the firing pin hits it. Old wildcatters' trick.

Hey, have fun experimenting!

HiBC · December 14, 2012, 09:10 AM

FWIW,the old .44 Automag was made by cutting off .308 or 30-06 brass.

Don H · December 14, 2012, 11:46 AM

Sort of like the .45 Winchester Magnum that debuted in the late 1970's and chambered in the Wildey and Grizzly pistols? I think TC chambered a barrel for it at one time.

December 13, 2012, 11:54 AM	#1
jkpq45 Member Join Date: September 28, 2012 Posts: 44	Wildcat: .45 ACP Extra Long? Hello All--Mods, please feel free to move the topic if I'm in the wrong sub-forum. I'm considering a wildcat cartridge along the lines of .450 Bushmaster using a rimless, headspacing-on-the-case-mouth cartridge utilizing the wide variety of 0.450"-0.454" projectiles available for .45ACP, 45LC, .454Casull and .460S&W Magnum. I could hold pressures to the .450B limit of 38 ksi, but what's the fun in that? I'd like to use .30-06 brass as the parent case (citing availability as the reason) vs. the .284 case the .450B is based on. I'm planning on installing this cartridge into a single-shot, break-action H&R/NEF rifle receiver to begin with. The question is--how to fireform? I'm planning on a case OAL of ~2.25". Can I count on the extractor to "hang on" to the case hard enough that it can be prevented from being driven forward by the firing pin during forming? Any chance I can trim the case after forming? Thanks for the advice--this is my first wildcat to headspace this way, so I appreciate the input. jkpq45

December 13, 2012, 07:51 PM	#2
Scorch Senior Member Join Date: February 13, 2006 Location: Washington state Posts: 15,248	Sounds like you are talking about a rimless 45 cal version of a 444 Marlin. It can certainly be done, but it will cause you some trouble. 1- Rifles generally do not like cases that headspace on the mouth. The longer cases do not headspace well and can cause issues. 2- Rifle chambers like some taper to them to ease extraction. About .010" of taper. More later. 3- At higher pressures, recoil and bullet backout will become an issue because of the taper crimp. 45 Win Mag rifles were produced, I think they are cool, but I am not sure if they had issues with this. 4- The biggest issue is that brass cannot be made easily from 30-06, you will wind up with a rebated rim case. 45 ACP base diameter is .480" (versus .470" for 30-06/308), and that leaves the brass very thin at the case mouth (.005"-.007" in order to give the needed case taper). You are talking about higher pressure, so you need thicker brass at the case mouth, maybe .012", which will make the case mouth .475" minimum, and your base diameter is .470", so you wil be bulging the brass out to fit the chamber. Problem there, but not insurmountable. 5- For fireforming, seat a lead bullet out far enough so that it engages the lands, that will keep it from being driven forward when the firing pin hits it. Old wildcatters' trick. Hey, have fun experimenting! __________________ Never try to educate someone who resists knowledge at all costs. But what do I know? Summit Arms Services

December 14, 2012, 11:46 AM	#4
Don H Senior Member Join Date: May 8, 2000 Location: SLC,Utah Posts: 2,704	Sort of like the .45 Winchester Magnum that debuted in the late 1970's and chambered in the Wildey and Grizzly pistols? I think TC chambered a barrel for it at one time. __________________ Don http://www.utahconcealedcarry.com/forum/

December 14, 2012, 09:10 AM	#3
HiBC Senior Member Join Date: November 13, 2006 Posts: 8,289	FWIW,the old .44 Automag was made by cutting off .308 or 30-06 brass.