Forming 243 40' Improved

[Westerner2]

I am trying to form 243 40' Imp.And it is not working.
I Annealed 100 rounds.I am loading 100gr Sierra Pro-Hunter with 43.8 gr of RL-22.I am seateing them .005 off the L&G.I am useing Win Brass.
I have loaded them three times and they are NOT fulley formed YET!!
Any ideas of what is going on?????????


I need HELP

Westerner 2

[Jack]

Westerner, welcome to Huntchat.
First, a question or two... how much of the case are you annealing, and what procedure do you use for annealing?
The thing I can think of off the top of my head is this: usually for blowing out cases in an improved chamber, the experts recommend using a medium charge of a medium speed powder, rather than the slower powder you'd normally load in an improved 243.
In other words, a middle of the range charge of a powder like 4895 rather than something slow like Reloder 22.

[Westerner2]

The Cases were Annealed in a machine by a friend.They are Annealed about 3/16 past the sholder.
I am useing the 100gr Sierra Pro-Hunter because I had 500 of them.The RL 22 was just a book load and I had 3lb of it.I use a lot of it for other loads I do.

Westerner 2

[Catfish]

First I NEVER Annel cases to fire form them. RL-22 is a little slow for the 100 gr. bullet in the .243, but I would have guessed it should have fire formed them. You only problem is that you are just alittle low on presure. If you can get in more powder put it in, if not you`ll have to change powders.

[Rocky Raab]

Well, I guess it's too late to try to talk you out of expanding a case that's already on the limit of case to bore volume efficiency, huh? Or to warn you that they're a booger to fireform?

Oh well...

In that event, I'll second what Catfish said. You need to fireform with a bit faster powder. The slow, gentle pressure curve buildup that RL-22 is giving you may be super for high muzzle velocity, but it's the wrong approach to fireforming.

Look for a "book" load using a faster powder like 4895, 4064, Varget or RL-15 then load to 95% of book maximum. That should give you the pressure "pop" you need to shove brass into those real sharp corners.

[Westerner2]

Thank vary much.I have all of thoses Powers I will try them.
I though about doing it to a 260 Rem.But I love the 243W.I have three of them.

Westerner 2

[Catfish]

If you want a faster round you could have had the barrel chambered in .243-06 and neck down some 06 brass to .243. I doubt that the twist rate in the barrel is fast enough to to use 107 gr. bullets and if I were going to chamber that round I would want an 8 twist for the 107 gr. bullets.

[Larryjk]

Westerner2, I chamber for this, and it is also called the 243 Ackley Improved. Like they said, use a faster powder, put the bullet right to the rifling and shoot. The cases don't have to be annealed first, but doing so should have been a plus. When your rifle was chambered was it a new chamber or a rechamber from a standaard .243 Win.? If it was a rechamber, the barrel should have been set back a thread because the Ackley Improved (or the Rem Improved 40') is about 0.004 shorter headspace than the standard. This is so you can put a standard .243 Win. in the chamber and fireform. You should have a little pressure before the bolt handle goes all the way down to battery. You won't hurt the gun. This procedure also insures you will end up with a fireformed case that doesn't have any stretching in the web area.
If you don't have this .004 shorter chamber, you will end up stretching the web and setting back the shoulder each time you shoot the case, resulting in early case failure. If you just case-neck size the fireformed cases, you shouldn't have this problem. Standard .243 Win. cases "grow" so that you need to trim about every third shot. You eliminate this considerably with the improved case.

[Rev]

I agree with everything stated above. Use a moderate to full standard .243 W load of medium burning rate powder (4895, 4064, 4320. 748 or whatever you have most of near those burning rates.

In my 6mm. AI, I use new un-annealed brass (usually Rem.) and 95-100 gr. bullets. I do seat the bullets firmly into the lands when fire forming. That insures that the head stamp of the case is firmly against the bolt face and any stretching is forward as the fire forming takes place. Pressing the bullet into the lands also will increase initial chamber pressure slightly (but not dangerously) helping to fire form the case the first time. I also like to feel slight resistance when closing the bolt.

After fire forming, I like to neck size only for as long as possible. When chambering becomes more difficult after several (sometimes numerous) reloadings, I'll partially resize the case body just enough for easy chambering. With the 40 degree shoulder, my case lengths hardly grow at all.

I know I've repeated a lot of what's already been said, but just wanted to throw in another opinion agreeing with all the others.

BTW, IMR-4350, Nosler 95 gr. BT's, and Fed 210M's with Rem cases work best in my 6mm. AI.

Rev