Seating Depth Selection

[mbeavers1]

I am trying a new powder for my 6BR. It has always shot great at 2810 fps with Vargrt and 109s jumping 0.020". I was able to get the same speed and am now trying to find the right seating depth. My shooting buddy and I disagree.

I think 0.025" and he thinks 0.050". Opinions?

 

[hafejd30]

I say .025”. Less vertical as the throat grows .010”

Both look good honestly but closer to the lands leaves more room for throat erosion later

 

[Tokay444]

.027”

 

[Rio Precision Gunworks]

.027”

This. 0.027 gives you a few thou in case you seat a few that aren't consistent. And you should in theory be good for quite a bit of throat erosion.

 

[Rocketmandb]

With my 6 BRA with both 105s and 109s, I've always found something in the ~.020 to .030 realm to work best. I've also found solid performance at much higher numbers, but not as good as the range mentioned.

Also, when I do seating depth testing, I go in .003" increments with Berger Hybrids. The .005" you're doing might go right over an optimum depth.

 

[DeathBeforeDismount]

Bergers, especially the hybrids like to be jumped. I don't take them under .030 and most shoot better around .060-.090. This may be limited by your cartridge, magazine and freebore, but in a BR it should not be an issue at all.

Mark Gordon has a great article on this. All this old man BS about jamming into the lands or right off the lands is just that. They proved the more jump the better the gun shot.

Scott Satterlee has also done some testing with ultra long freebores and has found they are much more forgiving to shoot.

If you don't want to dick around with seating depth, you could just get a tuner as well.


With a BR, BRA, Dasher, GT....... Alpha/Lapua Brass, Berger hybrid, Varget/N140/H4350. Jump the bullet .030-.090. Pick a velocity and go to town. If you aren't shooting 3/8 groups BEFORE bullet seating testing, something is wrong in your reloading process.

 

[Tokay444]

My 6BR is a 1 hole gun at 5 thou off with 105 Hybrids. When it’s not, I usually know it before I even look, because I’m honest with myself.
The conclusion to Mark’s test wasn’t that the gun shot better with a farther jump. It wasn’t that the tune on the bleeding edge, and was less susceptible to going out of tune. It showed to be less sensitive to throat migration is all. They did measure smaller groups with smaller jumps.

 

[Rio Precision Gunworks]

Mark Gordon has a great article on this. All this old man BS about jamming into the lands or right off the lands is just that. They proved the more jump the better the gun shot.

That's definitely *not* what they proved. They showed that the rifle shot acceptable for PRS longer with the jumps. Not that the seating depths were better groups in general.

Jamming and/or being very close to lands still produces better results (F class and BR) group wise, but *may* need more attention.

Larger jumps perform acceptable for PRS and retain that acceptability through more throat erosion. Which is what you want when shooting 200+ rounds in a weekend.

 

[Rio Precision Gunworks]

 

[mbeavers1]

View attachment 8283579

This would indicate picking .050". POI is similar to 0.065".

Should be noted that I'm likely not going to have the 'best' groups because Im trying to not use Varget for speed purposes. Im trying to load on my 750 exclusively using the powder drop and ball powder.

Not a huge sample but think its possible.

 

[Rio Precision Gunworks]

This would indicate picking .050". POI is similar to 0.065".

Should be noted that I'm likely not going to have the 'best' groups because Im trying to not use Varget for speed purposes. Im trying to load on my 750 exclusively using the powder drop and ball powder.

Not a huge sample but think its possible.
View attachment 8283603

Your POI on .025, .030, .035 is very close.

Also, if that's 20shots with 7.8sd, then yea, you're fine on that front. You should have an SD of 11 (at max) with that sample if things continue.

 

[mbeavers1]

Your POI on .025, .030, .035 is very close.

Also, if that's 20shots with 7.8sd, then yea, you're fine on that front. You should have an SD of 11 (at max) with that sample if things continue.

Yup that was over the 20 shots prior to shooting these groups.