Powder capacity 6br 0 freebore vs 6ppc .045 freebore

[NC/Br Shooter]

I think the standard difference in powder capacity of 6br vs 6ppc is about 4.5 to 5 grains.
So doesn't freebore change powder capacity a bit?
If you where to compare the two cartridges or Chambers rather, 6poc with a .045 free bore against a 6br with 0 freebore ,using the same flat base 68grain pill. Wouldn't this even out the powder capacity difference of the two chamberings?
Iv tried to explain this to a friend and best I could, we weren't arguing at all, I just didn't have a definitive number to back up what the difference would be. If there is any.

 

[urbanrifleman]

It does.

 

[Frankm]

Probably can do an inside neck diameter calc with .045 of freebore and get to any of water capacity reduction … I m not smart enough to do it quickly but there’s a way I m sure ….

 

[Frankm]

Any should of been “amount”

 

[gunsandgunsmithing]

Not even close to evening them out. A .045 vs a zero is simply .045 less bullet in the neck for the longer fb. So neck id x .045 is all you gain with that amount of fb. Doesn't take much to visualize it. Just set your calipers at .045, look at that space and imagine a teeny column that's as big around as the neck id and that .045 long. Maybe a layer of n133 kernels the diameter of the neck id....maybe a tick more but you get the idea. About a couple of tenths or so gained....maybe.

 

[urbanrifleman]

In 6br the difference between 104 and zero freebore was about 1.5 grains of n133.

 

[gunsandgunsmithing]

In 6br the difference between 104 and zero freebore was about 1.5 grains of n133.

Not terribly different than I said but it's hard to do it that way without "eyeball subjectivity" whereas, area is area and is not subjective. It is what it is.

 

[NC/Br Shooter]

In 6br the difference between 104 and zero freebore was about 1.5 grains of n133.

That's what I was wondering. In this case. It would be about 60% less of 1.5 grains. So not much at all.

 

[urbanrifleman]

That's what I was wondering. In this case. It would be about 60% less of 1.5 grains. So not much at all.

.75 grains ish.

 

[gunsandgunsmithing]

That's what I was wondering. In this case. It would be about 60% less of 1.5 grains. So not much at all.

How'd you come to that % ?

 

[NC/Br Shooter]

Was just a hust

How'd you come to that % ?

Was just a close guess.

 

[NC/Br Shooter]

How'd you come to that % ?

Was just a close guess.
104-45=59
Look at it in percentages if you want, or not

 

[Frankm]

Probably a half grain to something under a grain IF I was guessing. With a chronograph and some careful loading could probably increase your normal charge in .2 gr increases and see where it went. I wouldn’t expect it to be anywhere close to the 6 BR 0 throat performance though; at least not without hotrodding the PPC and hammering your brass !

 

[divingin]

Sure, make me try and do math again...

Cylinder Volume = Pi(R^2)H
Cylinder Volume = 3.1415 (.122in^2)(.04in)
Cylinder Volume = 3.1415 (.015sq in) (.04in)
Cylinder Volume = .00187 cubic inches.

Given a cubic inch is 16.4cc's, that's 0.0306 cc's.

N133 density is listed at 880 (and 870, depending on who you believe) g/l; that's .88 and .87 g/cc.
Converting that to grains yields 13.58 or 13.42 gr/cc

Taking the fractional CC from above means the neck volume change yields 0.415 or .0411 grains of N133, depending on your estimate of bulk density.

I take zero responsibility for any math errors. My math teachers are probably all dead now, so I can blame them.

 

[gunsandgunsmithing]

Sure, make me try and do math again...

Cylinder Volume = Pi(R^2)H
Cylinder Volume = 3.1415 (.122in^2)(.04in)
Cylinder Volume = 3.1415 (.015sq in) (.04in)
Cylinder Volume = .00187 cubic inches.

Given a cubic inch is 16.4cc's, that's 0.0306 cc's.

N133 density is listed at 880 (and 870, depending on who you believe) g/l; that's .88 and .87 g/cc.
Converting that to grains yields 13.58 or 13.42 gr/cc

Taking the fractional CC from above means the neck volume change yields 0.415 or .0411 grains of N133, depending on your estimate of bulk density.

I take zero responsibility for any math errors. My math teachers are probably all dead now, so I can blame them.

Lol! Close enough for me! Thanks!

 

[Alex Wheeler]

What happens with small changes in capacity is you end up adjusting powder to end up where you started. The change has to be big enough to allow you to get to the next node or its pointless

 

[NC/Br Shooter]

Sure, make me try and do math again...

Cylinder Volume = Pi(R^2)H
Cylinder Volume = 3.1415 (.122in^2)(.04in)
Cylinder Volume = 3.1415 (.015sq in) (.04in)
Cylinder Volume = .00187 cubic inches.

Given a cubic inch is 16.4cc's, that's 0.0306 cc's.

N133 density is listed at 880 (and 870, depending on who you believe) g/l; that's .88 and .87 g/cc.
Converting that to grains yields 13.58 or 13.42 gr/cc

Taking the fractional CC from above means the neck volume change yields 0.415 or .0411 grains of N133, depending on your estimate of bulk density.

I take zero responsibility for any math errors. My math teachers are probably all dead now, so I can blame them.

.04 of a grain?
That's all?
You did the math right there alright. Thanks
Shows what guessing will get ya.
Thanks for that explanation