What a difference seating depth makes

[adamjp]

So, I've been pulling my hair out with the 6mm BR and the Berger 105gn BT bullets. So much promise, but such poor performance.

Yesterday I sat down and worked up a load development set that would answer the questions once and for all.

Start with the normal 11thou JAM, include a 22thou JAM, and then look at the OFF lands loadings of 40, 60 and 80 thou OFF.

Proof is in the shooting.

Ignore the group in the bottom left, that is the 6/223 getting some exercise. There were 6x cartridges left. 2 had been pulled and reloaded, 4 were clean reloads. Guess which ones were which?

[ecomeat]

Adamjp,
Don't be frightened to try 0.100" and even 0.120" Jumps, as per Walt Berger's recommendation. It might get even better
I run 4 x 7mm barrels in an F Class Open rifle, and they are all totally different in "what they like".
One Bartlein likes 180 gr VLDs jammed 0.005" and 180 gr Hybrids jumped 0.015"
The second Bartlein likes VLds jammed 0.015" and shoots best with Hybrids jumped 0.080"

A lot of shooters certainly start off with a jam, or touching, and that is very true of the long range af Class crowd, where new chamberings are often based on correct freebore to allow the 180 gr bullets to be well jammed. But Vince Northfield (originally one of the Wild Dog team, and now living in Townsville) has beaten basically everybody at the top of our game at least once using a 7mm-08, at a slow node of just over 2700 fps, and jumping at least 80thou.
He actually reckons that his next barrel will be chambered from scratch for an 80thou to 100thou jump.

[RDavies]

Adamjp,
Don't be frightened to try 0.100" and even 0.120" Jumps, as per Walt Berger's recommendation. It might get even better
I run 4 x 7mm barrels in an F Class Open rifle, and they are all totally different in "what they like".
One Bartlein likes 180 gr VLDs jammed 0.005" and 180 gr Hybrids jumped 0.015"
The second Bartlein likes VLds jammed 0.015" and shoots best with Hybrids jumped 0.080"

A lot of shooters certainly start off with a jam, or touching, and that is very true of the long range af Class crowd, where new chamberings are often based on correct freebore to allow the 180 gr bullets to be well jammed. But Vince Northfield (originally one of the Wild Dog team, and now living in Townsville) has beaten basically everybody at the top of our game at least once using a 7mm-08, at a slow node of just over 2700 fps, and jumping at least 80thou.
He actually reckons that his next barrel will be chambered from scratch for an 80thou to 100thou jump.

I gotta agree with you on this one Ecomeat. I'm the first one to start off load development with bullets jammed, but I have had some problem barrels which were OK, but nothing special until I jumped them a lot. It is strange that I haven't had many barrels which like the usual .010"-.030" jump, but some have loved the big jumps.