PDA

View Full Version : case annealing



terryhawk
03-01-2008, 07:50 PM
i'm in the final throws of a rifle build. we fired a round out of a barrelled action fri. this is a wildcat ie; 243 catbird i neck sized a 270 case down to 6mm and figured i would anneal prior to fire forming . after fire forming i noticed the corners at shoulder as well as where shoulder meets neck are not as sharp as they should be. should i wait to anneal after fire forming ?? i intend to fire form remaining cases using the cream of wheat method (please don't chastise don't have fireforming barrel at this time) only going to do limited #at this time.... thanks for all opinions

Larry Elliott
03-01-2008, 08:08 PM
If the cases are new and unfired I wouldn't bother with annealing them. If the shoulder isn't as sharp as it should be increase the powder charge. Some suggest using a light charge, but I fireform Ackley's, etc by using the charge I'll use in the round in question or as much as the unformed case will hold. The energy "wasted" in blowing the case out will be enough to keep pressures in line.

I've tried other methods, but the simplest method I've found for fireforming is to use a bullet and normal powder charge. Trying to clean burned Cream of Wheat or cornmeal out of a rifle barrel is like trying to clean the bottom of a pot that you've burned either of them in. Ugly in my experience.

terryhawk
03-01-2008, 09:15 PM
larry,
thx for response. i probably was'nt clear in 1st thread. i did anneal the case before fire forming. i'm using load data for 240 gibbs as this is the closest cartridge configuration i can find. backed off 10 percent indications ie;primer looks like a warm load as is. any thoughts?

Larry Elliott
03-01-2008, 11:39 PM
Flattened or cratered primers depend on the primers you're using since some primer cups seem to be softer or thinner than others. If you annealed the shoulders before fireforming and they didn't come out sharp, assuming that extraction was fine you could probably go up with your charge a bit. I tend to load fairly warm for rifles, so flattened and mildly cratered primers don't bother me as long as the edge of the primer is still radiused. If the bolt lift and extraction are fine it's likely not a problem.

With a case that size and 6 mm bore you're likely using a fairly slow powders which might not give optimum fireforming. A faster powder might work better, but I don't know what that might be.

What are you going to use the rifle for? If it's for hunting either varmints or game and accuracy is good with the fireforming loads you might want to fireform while you're using the rifle for its intended purpose. Saves barrels and bullets if the accuracy is okay.

Stonewall
03-01-2008, 11:41 PM
There is a .240 Catbird article in an older Precision Shooting magazine.

I would contact Jarrett for information on fire forming loads .
mailto:jarrett5@mindspring.com

Quickload would proably be quite helpfull here. http://www.neconos.com/details3.htm

.240 Weatherby loads would be a better place to start. If your headspace isn't perfect on the first firing the primers will be flat .

Glenn:D

John Kielly
03-02-2008, 04:29 AM
There's a possibility that what you're seeing is the primers backing out of the case at the start of powder ignition, then being hammered flat as the case backs up to fill the chamber.

terryhawk
03-02-2008, 02:01 PM
thanks to all for info.
in response to some of the things mentioned i have looked at the similarities between the 240 wtby and 240 gibbs the wthby seems to be on the low side however,somewhere between the two seems to be good baseline data to work off of.
this is not the first time i've heard using a faster burn powder to fireform or that it creates better results .but i simply would'nt know where to begin would there be some sort of criteria out there a percentile reduction or gain when work from slow to fast?
thanks again
mark