need explanation

06 February 2002, 15:17

Chuck F

need explanation

For the 45ACP the Sierra manual has:
185 gr. bullet with 6.5 grs. unique at 850 fps.
230 gr. bullet with 6.4 grs. unique at 850 fps.
The Hornady manual has:
185 gr. bullet with 7.8 grs. sr4756 at 850 fps.
230 gr. bullet with 7.6 grs. sr4756 at 850 fps.
T thought it took more powder to move a heavier bullet than a lighter one at the same fps. Where am I going wrong?

Chuck

06 February 2002, 15:29

ricciardelli

It has to do with the pressure/time curve...

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http://stevespages.com/page8.htm

06 February 2002, 16:08

Chuck F

Ricciardelli

I called Sierra and the gentleman I spoke to said he didn't develop those loads and he really didn't answer my quwstion. With your answer I undestand now. Thanks.

Chuck

07 February 2002, 17:23

<BigBob>

CHUCK F,
Loading the same charge with a heavier bullet will create high pressures. I do not know of a single cartridge where a heavier bullet is driven to a higher velocity than a lighter bullet if the difference it 5 grains or more. Good luck.

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BigBob

07 February 2002, 18:53

JerryO

quote:
Originally posted by Chuck F:
I thought it took more powder to move a heavier bullet than a lighter one at the same fps. Where am I going wrong?
Chuck[/B]

The heavier bullet reduces the powder space, creating higher pressure which pushes harder on the bullet.

Notice that the lighter bullets are below max pressure while the heavy bullets are at (or near) max pressure with the same amount of powder.

It can be real. I noticed it when running some .38spec loads across a chrony.

JerryO