6BR and 80gr Berger FBs?

S

sgt_jamez

New member
So I normally shoot 105gr Berger's from my 28" 1:8 twist bbl. I decided to give myself brain cancer and try something new.

So here's my basic question... what general speed range should I be expecting to see?

I've read that these bullets tend to be most accurate around the 3025-3125 range (I don't have the actual values in front of me so those are approximations).

This past weekend I loaded up a test strings to look for velocity flat spots and the speed data I got on some powders was not as I expected. I used Quickload as a max load reference and my start point was 10% reduced.

X-Term - 30.7gr 3229 fps (3037 fps predicted)
2520 - 32.3 gr 3261 fps (3173 fps predicted)

I know QL isn't the end all of predictions but it's worked well for me in the past and these measured values seem extremely high.

I guess my last question is somewhat general. Would it be a true statement to say that any given bullet has a "sweet spot" velocity window? And if that's true... how is someone supposed to come to that determination? Hopefully the answer isn't bottom to top powder range testing.

Thanks all!
 
Smokeless powder burns more energetically under containment (unlike black powder which damps under pressure) therefore a smaller pressure vessel skews the numbers for a program like Quickload. In other words, the same amount of powder will produce more velocity in a smaller vessel than in a larger one.

a smaller vessel combined with better design allows the 6BR to perform at a higher level than larger more conventional case designs, the designs and yields upon which QL's parameters are based.
 
That makes sense! Thank you.

What about velocities for an 80gr bullet? Is there a sweet spot? And what would be considered too fast?
 
sgt_jamez said:
That makes sense! Thank you.

What about velocities for an 80gr bullet? Is there a sweet spot? And what would be considered too fast?
Click to expand...
I've shot 80s from 3200-3400fps with good results. Ime, they liked being pushed pretty hard but I know others that are shooting very well at around 3250.
 
mwezell said:
I've shot 80s from 3200-3400fps with good results. Ime, they liked being pushed pretty hard but I know others that are shooting very well at around 3250.
Click to expand...

Wow... ok so I wasn't even close to the performance window. I think I need to go do some more testing... groups too!

Thanks guys!
 
sgt_jamez said:
Wow... ok so I wasn't even close to the performance window. I think I need to go do some more testing... groups too!

Thanks guys!
Click to expand...

OK-OK-OKAYYYY...... hang on there ..... this is a BENCHREST forum......... A RACING forum.....We START loading where the books leave off.

Undersized ejector holes......
Bushed or undersized (.062-ish) firing pins in TIGHTLY FITTED holes....
Scrupulous tolerances thru-out, I mis-doubt Ezell's fired a factory action in lo these many years.....

"that performance window" pretty much means a custom rifle setup which if you've got, and if you truly understand pressure signs, is still someething to be well understood ;)

F'rinstance, an 80gr 3400fps load worked up on a 65 degree day then left out in the sun on the shooting bench on a hot summer's day can get downright rode'o quite quicklike

Wear your safety glasses when venturing forth onto thee mighty see of velociteee

(which IS where the good fishing is BTW)
 
What action are you using?
3200-3400 is plenty fast enough if your action take take it. In a weak or unsafe rifle that may not be the best speed for you and as Bill Gammon says, what does it look like on paper. A rocket is no good if it misses the mark.
 
I shoot Bart’s 80 grn Dominator BT’s out of my 1-12 twist 6BR, .060 throat, 26 inch long barrel.

3350 FPS is no problem, shoots mid three groups at 200. Bat M Action.
 
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