Hi there, I have a Rem 788 that I have chambered for the 243 AI. I have a Pac-Nor standard match stainless barrel, 27" long, #7 contour, 1-9 twist. Is the 1-9 twist fast enought to stabalize 105gr. and 107gr. bullets? I just shot some Berger 95gr. VLD's today, with AA4350 powder. I think it could shoot a little better. What loads do you guys like to shoot. Any info would be greatly appreciated.
Jeff

The dirty little secret that no one will discuss about Ackley Improved loads is that you need to work up your own data.

I just recently rechambered my Rem 700 PSS to .223 AI and have gone so far as to set up a web site to collect load data. PO Ackley, in "Handbook for Shooters & Reloaders" lists some load data for .243 AI, but the data is pretty old (1962).

You need to use a chronograph to work up loads. I always wanted a chronograph. Now I own one. I'm amazed at the data I'm getting. Loading without a chronograph is shooting in the dark. It's impossible to work up a wildcat load without one.

PO Ackley notes that 35% of the load energy goes into spinning the bullet in the rifling. Tighter rifling uses more energy. So velocities that someone posts from a 1:14 bbl. are not going to work for your 1:9 bbl. -- all other variables being equal. BUT, there are a lot of other variables at work in the mix!

1:9 rifling is pretty tight. This should stabilize most of the heavier bullets. Sierra and some of the other bullet mfg. web sites should discuss rifling requirements for their heavier bullets.

You might search the web for load data. My search for .223 Ackley Improved turned up next to nothing. But .243 Ackley load data may be easier to find. I started a .223 Ackley Forum on HotBoards.com and have been able to gather some data through it. That entails some work and some ability to write HTML and otherwise run a web forum.

The up side of all this is that working up data for a wildcat cartridge opens up a whole new world of ballistics to you. My reloading skills have taken a quantum leap!

Varmint Al may list some load data for .243 Ackley. He has an excellent discussion of reloading:

http://www.cctrap.com/~varmint/arelo.htm

[ 06-02-2002, 21:53: Message edited by: Genghis ]

Hi Jeff,

Follow this link to a site where I and others have posted load data and information on the .243AI.

.243AI

George

I agree that each gun is an individual, and in order to receive any benefit from an improved chamber, you must work up loads for that individual rifle using a chronograph. I would start with the consensus maximum load for the standard .243 and go from there.

The 1-9 twist is pretty common for 6mm bores. Most .243's used 1-10, but when Remington switched their .244 from 1-12 to the 6mm at 1-9, they switched the barrels on their .243's to the same. Whether it will stabilize the over-100 grain specialty bullets can only be determined by shooting them in your gun. Generally, higher velocities will stabilize a given bullet at a slower twist.

P.O. Ackley was a brilliant gunsmith, but as a physicist he might as well have had the sun orbiting the earth. The energy which goes into imparting spin to the bullet is far less than 1% of the total (and the biggest part of the powder energy goes flying out of the barrel as heat, anyway). If the difference in velocity between a 1-12 twist and a 1-9 twist could be measured, it would be insignificant anyway. After all, have you ever had a rifle "twisted" out of your hands due to the "tremendous" torque imparted by spinning the bullet? Think about it: Does the rifle twist with half the energy that it kicks?