445 SuperMag challenges

cptmclark · January 10, 2008, 11:46 AM

I'm loading the 445 for a single shot rifle. Not much data, and the rifle has a really long throat. It started life as a 44 magnum, then reamed to 445. I've now had three range sessions working up loads, and I'm puzzled.
Two probelms I'd really like help with.
First, is accuracy, and may be tied to the second. Most loads tried give vertical stringing. A lot of vertical, say 6 or 7 inches at 100 yards. Horizontal is very consisant. I floated the forearm of the HR 1871 Handi Rifle (Except for the stud which I bedded), and it still happens. I've found limited loads that don't string vertically, but best accuracy is 2.2 moa or so.
I'm using Hornady data with 296 powder, and the 300 xtp, 265 fp, and Speer 240 GD. I suspect the long hop to the rifling, but loading these long which requires no crimp, is not good for ignition apparently. I also tried some IMR4198 that was on hand, and it gave as good results as the other, but probably less velocity. It didn't like un-crimped bullets either. I've also tried loading long with no crimp (near the lands), with no improvement. A 1680 and W680 are no more, and I plan to try 4227. What do you think?
Second problem is sooty cases, making me think the case is substantially smaller than the chamber. This happens even with heavy loads. I'm guessing here and eager to hear from you more knowledgable guys.
New Starline brass measures .454 at the web, .454 at the mouth, and (go figure) .452 in the middle. After sizing and loading of new brass, it measures .454 at the web, .454 at the mouth over the seated bullet, and still .452 in the middle. Spec for the 445 is .455 at the web and .454 at the mouth.
(Spec for 44 is slightly larger at .457 web and 456 mouth. Would two or three thousandths be enough to prevent sealing?) I measure the chamber at ,456 with simple inside calipers but don't feel confident this is a good measure. [B]Fired cases measure .454 at the web, .461 just above the web, from 458 to 460 in the middle, and still .454 at the mouth.[/B]
So now I see fired case expansion up to .461 at the "expansion ring", and still getting some blow by looking at the sooty cases. That's .006 expansion, which seems excessive to me. Do I have a bad chamber? Can I partially size straight walled cases like I would my bottlenecks?
Many thanks.

SOSARMS · January 10, 2008, 08:59 PM

I've not had a problem with the 445 SM , but have not shot it in a rifle though...I have Dan Wesson with 8" and couple T/C barrels up to 14" but not rifle. I have not encountered any problems with sooting . The cases prob are the same as yours, since i believe starline was the only supplier, at least at the time i purchased. Cases though are straight cases and should not be more than 002 off in diameter anywhere through the case. The dies i use are full length. I do crimp the case as recommended. I normally use 300 gr JHP or Barnes solids and load near max pressure. I wonder if your reamer got a little happy taking out material ???

January 10, 2008, 11:46 AM	#1
cptmclark Senior Member Join Date: November 22, 2004 Location: Indiana Posts: 432	445 SuperMag challenges I'm loading the 445 for a single shot rifle. Not much data, and the rifle has a really long throat. It started life as a 44 magnum, then reamed to 445. I've now had three range sessions working up loads, and I'm puzzled. Two probelms I'd really like help with. First, is accuracy, and may be tied to the second. Most loads tried give vertical stringing. A lot of vertical, say 6 or 7 inches at 100 yards. Horizontal is very consisant. I floated the forearm of the HR 1871 Handi Rifle (Except for the stud which I bedded), and it still happens. I've found limited loads that don't string vertically, but best accuracy is 2.2 moa or so. I'm using Hornady data with 296 powder, and the 300 xtp, 265 fp, and Speer 240 GD. I suspect the long hop to the rifling, but loading these long which requires no crimp, is not good for ignition apparently. I also tried some IMR4198 that was on hand, and it gave as good results as the other, but probably less velocity. It didn't like un-crimped bullets either. I've also tried loading long with no crimp (near the lands), with no improvement. A 1680 and W680 are no more, and I plan to try 4227. What do you think? Second problem is sooty cases, making me think the case is substantially smaller than the chamber. This happens even with heavy loads. I'm guessing here and eager to hear from you more knowledgable guys. New Starline brass measures .454 at the web, .454 at the mouth, and (go figure) .452 in the middle. After sizing and loading of new brass, it measures .454 at the web, .454 at the mouth over the seated bullet, and still .452 in the middle. Spec for the 445 is .455 at the web and .454 at the mouth. (Spec for 44 is slightly larger at .457 web and 456 mouth. Would two or three thousandths be enough to prevent sealing?) I measure the chamber at ,456 with simple inside calipers but don't feel confident this is a good measure. [B]Fired cases measure .454 at the web, .461 just above the web, from 458 to 460 in the middle, and still .454 at the mouth.[/B] So now I see fired case expansion up to .461 at the "expansion ring", and still getting some blow by looking at the sooty cases. That's .006 expansion, which seems excessive to me. Do I have a bad chamber? Can I partially size straight walled cases like I would my bottlenecks? Many thanks.

January 10, 2008, 08:59 PM	#2
SOSARMS Senior Member Join Date: June 13, 2006 Location: The great Buckeye state...where nuts are not just for eating Posts: 623	I've not had a problem with the 445 SM , but have not shot it in a rifle though...I have Dan Wesson with 8" and couple T/C barrels up to 14" but not rifle. I have not encountered any problems with sooting . The cases prob are the same as yours, since i believe starline was the only supplier, at least at the time i purchased. Cases though are straight cases and should not be more than 002 off in diameter anywhere through the case. The dies i use are full length. I do crimp the case as recommended. I normally use 300 gr JHP or Barnes solids and load near max pressure. I wonder if your reamer got a little happy taking out material ???