.308win: Strange Burn Pattern

goosevr1 · May 1, 2006, 08:04 AM

Playing with some 308 loads this weekend and had found a pretty decent load that gave quarter sized groups at 100 yards (42gr Varget, Remington Brass, CCI BR2 Primers, 168 Sierra HPBT).

I also made some "plinking" rounds--100gr Lead RN in 27gr H4198; one a few of the cartridges I had what looked like an usual residue burn--it looked like it was focused on one side of the brass rather than the other. Not sure if these photos capture it but here it is anyway. If anyone's had a similar experience can you explain why this happens and if it's still safe?

This was my first batch ever for using round nosed bullets in 308 calibur--never had a problem with the boat tail stuff but it seemed like the seating of the bullet didn't go to well. Some of the cartridges didn't chamber very easily; it looked like the bullet seated to a certain depth and then instead of taper crimping the additional force just pushed the neck down into itself a little more. A few of these cartridges were able to chamber and I think they fireformed out okay but should I discard this brass or is it safe to keep?

Leftoverdj · May 1, 2006, 08:11 AM

Nothing to worry about. Your low pressure cast loads did not expand the necks enough to seal. Gases flowed back past the side with the most clearance. If it bothers you, anneal the necks to dead soft.

Jim Watson · May 1, 2006, 08:14 AM

Low pressure of the plinking loads did not expand the brass to fully seal the chamber. Smoking is due to gas leakage. Lopsided because the case is laying in the bottom of the chamber.

Light loads can set the shoulder back. If you are seeing any fired primer protrusion that is where it is coming from. Keep those cases for light loads only.

Seating lead bullets calls for case mouth flare, best done with the Lyman "M" die. Doubly important if those bullets are plain base, not gas checked.

Why are you crimping .308? I can't see any benefit except for a machine gun.

May 1, 2006, 08:11 AM	#2
Leftoverdj Senior Member Join Date: October 15, 2004 Posts: 934	Nothing to worry about. Your low pressure cast loads did not expand the necks enough to seal. Gases flowed back past the side with the most clearance. If it bothers you, anneal the necks to dead soft.

May 1, 2006, 08:14 AM	#3
Jim Watson Senior Member Join Date: October 25, 2001 Location: Alabama Posts: 18,541	Low pressure of the plinking loads did not expand the brass to fully seal the chamber. Smoking is due to gas leakage. Lopsided because the case is laying in the bottom of the chamber. Light loads can set the shoulder back. If you are seeing any fired primer protrusion that is where it is coming from. Keep those cases for light loads only. Seating lead bullets calls for case mouth flare, best done with the Lyman "M" die. Doubly important if those bullets are plain base, not gas checked. Why are you crimping .308? I can't see any benefit except for a machine gun.