1/2 grain more, how fast???

[NC/Br Shooter]

Yesterday, I clocked my 68 grainers at 3285 out of my 6br 13.5 tw. . Load was 29.5 of vv133.
Today, I shot five rounds, Rain got me. Had to quit.
But I shot one of the smallest groups of my life, in to one hole, literally. I see Ejector outline on case head. So I think that's plenty of pressure.
Since I didn't have my radar out today. Because of rain.
How much more speed do would be gained going from 29.5' to 30 grains of charge?
Educated guess?

 

[6BRA]

I've pushed 90s to 3325 fps out of an 8 twist. A 68 should be over 3500 I would think. Sounds like another powder may offer better velocity, if that's what you are chasing. This is referring to a BRA. I mistakenly thought you were talking about a BRA from your title. Sorry.

 

[swd]

I generally see about 50fps for .5gr on the small/mid 6mm’s.

 

[SmokinJoe]

I shot the 6BR very successfully in NBRSA group when I first started BR. My magic was a coated Fowler 66 and N-135 for about the velocity level you are at now. If you want more speed, try TAC. I have gotten up around 3500 with 65 V-Max using TAC (for PD shooting).

 

[MDT6BRA]

Only your rifle can answer that question, you might try xbr8208 it seems to like the lighter bullets, I shoot it with 70 nos bt

 

[NC/Br Shooter]

I'm sticking to what I got.


Swd, hey man. Thanks.. that's what I was looking for. Thanks

 

[NC/Br Shooter]

I'm not chasing speed. Just couldn't wait to see what speed might be. .it'a be next week til I get it back out..

 

[SmokinJoe]

Well, if you have some N-135, try it.

 

[gunsandgunsmithing]

Every gun is different but n135 is the go to powder in a 6BR with light bullets. Not saying other options can't or won't shoot, just that n135 is sorta the gold standard. You just have to test beyond that. H322 is another good choice. Varget works well with heavier bullets but is seldom the best choice for the 62-70gr bullets in a BR.

 

[BartsBullets]

Yesterday, I clocked my 68 grainers at 3285 out of my 6br 13.5 tw. . Load was 29.5 of vv133.
Today, I shot five rounds, Rain got me. Had to quit.
But I shot one of the smallest groups of my life, in to one hole, literally. I see Ejector outline on case head. So I think that's plenty of pressure.
Since I didn't have my radar out today. Because of rain.
How much more speed do would be gained going from 29.5' to 30 grains of charge?
Educated guess?

Right around 3340.

Bart

 

[Bojo]

 

[Shooter13]

Right around 3340.

Bart

Exactly my calculation. It's amazing how math works!! (3340.6779)

 

[BartsBullets]

Exactly my calculation. It's amazing how math works!! (3340.6779)

Bingo!

 

[Frankm]

I would guess 50 fps more unless pressure is getting way up there; >62-63K then you might be getting 70-80 fps or more for that .5 grain increase.