I was fireforming some new brass. I did a jam fit into the lands where i normaly seat 5-10 thou. off the lands. I used the same powder load because it's pretty conservative. I got no highpressure signs but i had a light black "soot" on the sides of the case head. I've never had this happen before.
What do you guys think. BTW they shot like crap. should a new powder load be worked up when jamming the bullets? I figure the pressure is higher. Thanks in advance for your comments.

Cartridge? Load? Firearm?

Soot on the case can be a sign of more then one thing. With light loads it can at times be simply gas flowing back around the case before pressure rises enough to seal the gas at the case mouth.
Tell us more.

remington 700 22-250,1-8 twist barrel,32gr 4064 under 75gr moly a-max. I figured that it was gas escapeing but with the bullet into the lands should the neck not get blowen out and seal that off faster?

If this was a standard chamber and standard brass, what was gained by fire forming the brass in this manner? Wouldn't firing the brass with a normal load set-up acchieve the same thing?
I'm gonna make a "wag" that the fast twist and heavy bullet forced gas back around the neck. My 22-250s with 1/14, 52gr bullets, H380 would smoke somewhat. I didn't pay too much attention to it as long as the bullets went into the same hole.

Case head??

How many times has that brass been loaded? Soot sometimes occurs around the neck when the necks have work hardened. Since I don't shoot low pressure loads, I use it as a signal to anneal.

I assume we are talking about the neck.

I dont have much load data for 70gr bullets but it appears you are well over any max load for imr4064, especially if they are jamed into the lands. if the soot extends down the side of the cases you have an over pressure load.
Dave

If the soot comes from the case mouth/neck down the side of the case, then a low pressure load is likely the culprit. If the soot is only near the case head, then there is probably a pierced or leaking primer and the cause is high pressure...inspect the primers carefully.

If he really did mean the case head, could he be enlarging the primer pocket?? How he's going about "fire forming" his brass sounds like an accident waiting to happen.

I'm really pissed about this. I was just asking for a opinion. FYI i lived through this "accident waiting to happen". the real deal is...1)i was using new brass(norma)skim neck turned 2) I know what a case HEAD is. 3) I was 2 grains below the max load that i use with no high pressure signs. 4)benchrest shooters frequently seat the bullet into the lands. 5) I'll keep trying new things if i think it will shrink groups or help me learn!

As you say, benchrest shooters will "may" seat into the lands,but if the gun doesn't shoot well they will back out. Your gun doesn't like that so, I would back out.

If your primers are okay, not showing any signs of pressure than I would think that with the load you have, you are a bit low on the pressure side, which is may be why the neck is not sealing.

The other thing though, I would take a look at the norma brass and measure the thickness. I found that norma, compared to say winchester and remington tend to run thinner. With a standard chamber they may not seal as well.

I had one gun that I could only reload the norma brass 2 times and then it wouldn't hold a bullet. Winchester brass was okay in that gun, so I used that instead. It may be that the neck in that chamber was a bit oversized. That was a 22-250 as well.