Thanks Kraky,
The best loads for both the 7 Rem Mag and 300 Win Mag feature a case full of H 4831. I shoot rifles that plunk bullets out there at anywhere from 1800 fps to 3400 fps. My favorite 1000 yard load runs at 2850 fps. I don't try to wring the last fps out of each load, but if I am going to put up with the added expense and recoil of shooting Mags, I want to get the basic velocity I'm paying for.
JCN

I've tried everything I can think of to stop that initial stretch and I've come up blank each and every time. In EVERY case, I was never ever able to get the corners of the shoulder to "fold over". I finally resorted to using other brass to form cases for the 338 Win Mags I favor. I use 358 Norma Mag brass that is much longer in the body, and then size them down to just bump the shoulder in the 338 Win Mag. Works great!



The only thing I haven't tried is a recipe someone posted on the internet somewhere using a case full of ultra slow powder to fireform. He claimed he DID get the corners to fold, and to a degree I think this may be a possibility. When you form with COW, the propellant is at the base of the case with the COW on top. Because the COW is inert, it acts much as a hammer on the shoulder to push it out and therefore the stretch in the body, and the start of incipient case separation.



Incidentally, I've tried lubing all the case, only parts of it, putting the false shoulder in the neck, everything. Nothing prevented that stretch.



What was suggested with the slow powder makes a bit of sense in that when the propellant ignites, it all ignites giving equal push, including the powder stuffed to the shoulder and neck. This just might enable the exterior of the brass at that point to grip the chamber and at least somewhat reduce the stretch. That may be worth a try. Even filling the case to a moderately compressed load I think I would still put a false shoulder into the neck. Can't hurt, and it might help. Never tried it as it made more sense to me to use the Norma brass.



As far as brass life with our "short" cases, I neck size after the initial fireforming, bump back the shoulders at about 4 reloads, and anneal the necks at that time, and I'm able to get about a dozen reloads. I've managed as many as 15 a time or two, but 13 seems about it. This is with any of our domestic brass. Always check the cases but I start really looking hard at about 10 reloads.



With the Norma brass, following the same procedures as above, I'm still working on the first batch I used for the 358 experiment. They have 18 reloads and no signs of separation. However, because I load pretty hot, some of the primer pockets are beginning to get a bit loose.



I never used bullets with the Cream O' Wheat. Use a wad of toilet paper. And, using a fast pistol powder such as Unique or Bullseye, doesn't use that much powder, about 18g for the 338 class cases. The COW is biodegradable. The Sierra Club and environmentalists should love you for it!

I have had poor luck getting sharp corners with cream of wheat. I would load up some moderate amount of powder and seat the bullets long. Heck, make them way long with a light or no crimp so the bolt can press them in the case a tiny bit.

I've never had brass problems in situations like yours unless I'm loading in the 55,000psi to 65,000 range. If you can keep with moderate hunting loads I wouldn't bother at all with fireforming. You might just find a magic load at 100 fps less than a super max load AND I guarantee your animal will not know the difference. Also 100 fps less will probably mean NO MORE than 1" drop difference at 300 yds. It's up to you but if I was looking at doing that much brass I would not bother with all the fireforming.

I have recently worked up a load for my 7 Rem Mag, 300 Win Mag, and 338 win Mag rifles. I have some fresh brass, and am ready to load a couple hundred rounds of hunting ammo for each rifle. A few minutes with the Stony Point comparator comparing virgin and fired brass shows the usual: Fresh brass is made short, and the chambers on production rifles are made long. The least amount of headspace slop is .020". Since I squandered all my money on good brass, I'd like to get some decent life out of it.
I'm soliciting advice on the best way to fireform the brass to chamber specs before going on a reloading rampage next week.
I have the tapered expanders, so I can bump the necks up oversize, and then F/L size just enough to get a snug fit in the neck, then shoot a moderately stiff load over some old conventional bullets.
I could also use the fast pistol/shotgun powder trick with cream of wheat (I'll leave the Malt-O-Meal in the grocery for Ray A.).
Does anybody have any strong feelings for one method over the other?
What is the best way to keep the necks straight if you bump them up with a tapered expander?
Will all that singed Cream-O-Wheat turn my range into an EPA Superfund site?
The reason I ask is that the snug neck method will use up 600 bullets and 6 pounds of real rifle powder. If that is the best way to go, then so be it.
JCN

The purpose of the COW type loads isn't to get a 100% "sharp shouldered" perfect case, it's to move the shoulder forward/fill the chamber so that you end up with one that's 90+% (slight rounding of corners) and zero HS clearance. The first "full power" load will finish the job on the corners.

When I burn these barrels up I'll just throw new ones on.
I want to match enough brass up to the barrel so that about the time the brass is thinking about crapping out the barrel breathes its last, pukes its heart out, and croaks.
So far, the only barrels I've used up have been in .308 and .223. With the .308's I used 500 pieces of brass, six loads each piece, good accuracy, then pitch the brass, and start over. It is easy to set up brass for a .308. If the chamber is tight (I like 1.631") the brass starts out a very close fit.
These short Magnums are a lot sloppier. I'm trying to understand the process and learn the trajectories so I can shoot these rifles instinctively, like a shotgun. I also have the habit of policing up my brass, even when I hunt. (I don't want Msgt. Nail to kick my ass)
JCN

If you're talking about hunting ammo, I don't see any real need to fireform anything. Just trim your brass to a uniform length, load your hunting load into the virgin brass and go hunting. (after checking poi)
Why would you need to go thru all sorts of bench rest brass prep for a hunting round. I've never found enough difference between rounds loaded with virgin brass and ones loaded with once fired to cause concern in the field.
Another point to consider, while you're doing all this "fire forming", you are also burning up your barrel.

I like to comment on this subject.
I tried to fire form some 500 A square brass from a 460 WHTBY case, with fast pistol powder (R1 Norma = red dot) started at 10 gr/ COW/Parafine plug in the neck, it did not work.
At 30 gr of powder I has about 10 gr of powder unburned in the barrel the neck was blown out but the shoulder was not.

I think this may be be cause the case is nearly a straight wall,so I used a taper expander,a water hardened cast bullet tight in the lands and a stiff load of XMP5477.
This after annealing the cases

Regards Martin