pressure related primer problems?

[greggc1960]

If anyone has experienced this would you mind telling me what caused it? I changed powder to Hybrid 100V, started 2grs below max, using a seating depth of 3.960 instead of 3.660 with SMK 250 338s, and this happened. If the picture works you can see the primer looks like it was center punched. Oh yeah, its a CCI250 LRM primer. Any thoughts?

 

[Lefty7mmstw]

You didn't develop enough pressure to shove the primer face around the firing pin to the bolt face.

 

[RT2506]

First off the reason that they list starting loads is because that is where you should start when working with a new powder in YOUR rifle which is completely different than the one that the data was worked up in. Then moving a bullet that much closer to the lands will increase pressure.
I have had rifles with custom chambers that are a bit tighter than factory made rifles that I could not go over mid data loads with some powders before I ran into pressure problems but I was using a chrno so I found that I was getting the velocity I wanted with the top loads out of the lower loads. Just some things I picked up over the 30 some odd years of reloading.

 

[Lefty7mmstw]

I'm with rt2506 here, start at min. listed for the combo and walk it up. It looks as though your pressure is actually low to me, but it could also be a bit of extra headspace or something else causing your issue. In any case, work your loads up so you can see the primer changes/ case expansion changes/ accuracy changes/ velocity changes as you go. Your rifle will tell you what it wants, you just have to listen.

 

[greggc1960]

First off the reason that they list starting loads is because that is where you should start when working with a new powder in YOUR rifle which is completely different than the one that the data was worked up in. Then moving a bullet that much closer to the lands will increase pressure.
I have had rifles with custom chambers that are a bit tighter than factory made rifles that I could not go over mid data loads with some powders before I ran into pressure problems but I was using a chrno so I found that I was getting the velocity I wanted with the top loads out of the lower loads. Just some things I picked up over the 30 some odd years of reloading.

So...this is from hi pressure ? Not trying to be flippant, I'm having trouble understanding what your saying. I thought moving toward the lands , initially, anyway, lowered pressure. I get "in the lands" raises pressure, as the bullet cant move till pressure gets hi enough to move the bullet on into the barrel, and not trying to sound argumentive, but I still have nearly .100 jump. Am I wrong? And yeah, its gonna be nice to finally get a chronograph, but for now...I was thinking lower pressure might cause this? Thoughts, please?

 

[greggc1960]

I'm with rt2506 here, start at min. listed for the combo and walk it up. It looks as though your pressure is actually low to me, but it could also be a bit of extra headspace or something else causing your issue. In any case, work your loads up so you can see the primer changes/ case expansion changes/ accuracy changes/ velocity changes as you go. Your rifle will tell you what it wants, you just have to listen.

Thanks, I appreciate your comments. Since the book lists such a short OAL, do you think I should let one fly at that length, and see how it acts? The SMKs seem to like to be about .100 off in my rifle. I had thought that I was only borrowing some of the freebore. Not correct?

 

[blacknzr1]

if you seat a projectile into the case further, you get less pressure.
if you seat it further out, (longer over all length) you get more pressure.

it sounds backwards but that's how it is.

I start with a small jump to the lands when I develop a load. if I fine tune that load with seating depth I only seat the projectile further into the case by different amounts to test. i never go back out.

 

[Lefty7mmstw]

if you seat a projectile into the case further, you get less pressure.
if you seat it further out, (longer over all length) you get more pressure.

it sounds backwards but that's how it is.

I start with a small jump to the lands when I develop a load. if I fine tune that load with seating depth I only seat the projectile further into the case by different amounts to test. i never go back out.

yup, until you actually jamb the bullets into the rifling that is, then the pressure goes back up.

 

[RT2506]

The others explained the bullet seating pressure question. I could not really make out what the primer looked like in the picture. If you have too low pressure this can happen. When a cartridge is fired the case expands to fill the chamber and the base is slammed against the bolt face. In this process the primer actually moves in the primer pocket but is kept in the pocket and reseated as the base of the case slams into the bolt face supported by the firing pin. This all happens in a nano second. If the pressure is too low the primer can actually protrude a little from the case but still be rounded on the edges. I have seen the primer pierced which I think may be from a slightly week firing pin spring or slightly long firing pin or a little over size hole for the pin in the bolt face that lets the primer flow into the hole and pierce because it backs out too much before the base of the case slams into the bolt face to support the primer. Ain't reloading fun?

 

[greggc1960]

Thanks guys. Guess I'll start over.