Jamming the lands

[DynamicAccuracy]

I have a savage 243 i just got back from the gunsmith. Im wanting to tune a special load to shoot really tiny groups at 100-300 yards. Basically a benchrest style load. Ive never jammed bullets before and my question is do i tune powder charge with the bullet off the lands and then start with different amount of jam or do i go ahead and do a light .001-.003 jam when tuning powder charge. Ill looking at running the 85gr sierra gamekings or the 80gr berger flatbase bullets.

 

[MtnCreek]

Back off you current charge. You should jam enough to account for variations in bullets. You'll want to reduce neck tension to 1 to 2 thousandths. Imho, leave jamming to the bench rest crowd.

 

[spife7980]

If you are going to jam at all then start jammed, or at least do your pressure testing jammed. If you tune or max test jumping and then jam that can lead to an unpredicatable increase in pressure over what you found jumping them.

 

[arm017]

Yeah most folks will tell you to back off the lands and get your SD/ES tuned, then mess w/ seating depth.

 

[1J04]

I would highly advise you read, at the bare minimum, the stickies above by Tresmon. If you don't have the correct tools to measure CBTO, get'm. That number will 'help' keep you from eating your bolt. I'd also respectfully disaude you from 'jamming' bullets and give yourself some breathing room. But that's just me.
Read those Stickies.