Re: Powder for short barrel 243?
possibly something applicable to powder burn and short barrels:
http://www.hornady.com/assets/files/superformance-technology.pdf
i'd go with hornady superperformance / light magnums off the shelf,
http://www.hornady.com/store/243-Win-95-gr-SST-Superformance/ seemingly they are as close as you are going to get for a max vel. and built to be "safe" pressures.
chrony them through YOUR barrel. get the FPS. then look at load data to try to mimic that, starting lower and working your way up to the shelf bought stuff. look at the primers of shot rounds to see any signs of over pressure / over charging as you are working your way up jsut as a safety issue. sacrifice a few rounds of the shelf bought stuff to get case and overall length, weigh the powder inside and see what type of composition it is (flake, stick, ball) it may give you a clue to what they are using.
as mentioned before, fastest may not always be the most accurate. it's nice to have a flat shooter, but what's the point if the POI is erratic? while you are working up your loads, take note of the group size, you may find in YOUR rifle, slower is better.
even though you may be able to reach published loads for a 22" with a 20", that's not gaurantee that the powder that accomplished this is within safe pressures as you are typically using more powder to push it faster in a smaller length barrel, causing more pressure.
the "rule of thumb" is 50 fps per inch to calculate / relate max loads published to barrel lengths you have in reality, but then there are the "other rules of thumb".
from a chuck hawks article on barrel length and figures for per 1" of losing barrel length:
The 2001 Edition of the Shooter's Bible states, in the introduction to the Centerfire Rifle Ballistics section, "Barrel length affects velocity, and at various rates depending on the load. As a rule, figure 50 fps per inch of barrel, plus or minus, if your barrel is longer or shorter than 22 inches." However, they do not say what category of load to which this 50 fps average pertains.
Jack O'Connor wrote in The Rifle Book that, "The barrel shorter than standard has a velocity loss which averages about 25 foot-seconds for every inch cut off the barrel. Likewise, there is a velocity gain with a longer barrel." He went on to illustrate this using a .30-06 rifle shooting 180 grain bullets as an example, so his estimate was obviously for rifles in that general performance class.
Other authorities have tried to take into account the different velocity ranges within which modern cartridges operate. The Remington Catalog 2003 includes a "Centerfire Rifle Velocity Vs. Barrel Length" table that shows the following velocity changes for barrels shorter or longer than the test barrel length:
MV 2000-2500 fps, the approximate change in MV per 1" change in barrel length is 10 fps.
MV 2500-3000 fps, the approximate change in MV per 1" change in barrel length is 20 fps.
MV 3000-3500 fps, the approximate change in MV per 1" change in barrel length is 30 fps.
MV 3500-4000 fps, the approximate change in MV per 1" change in barrel length is 40 fps.
The 45th Edition of the Lyman Reloading Handbook also has a table showing Center Fire Rifle Velocity Vs. Barrel Length. Their figures apply to barrels between 20 and 26 inches in length and agree with the Remington figures. The Lyman table shows the following approximate velocity changes:
For rifles with muzzle velocities in the 1000-2000 fps range, the change in velocity for each 1" change in barrel length is 5 fps.
For rifles with muzzle velocities in the 2001-2500 fps range, the change in velocity for each 1" change in barrel length is 10 fps.
For rifles with muzzle velocities in the 2501-3000 fps range, the change in velocity for each 1" change in barrel length is 20 fps.
For rifles with muzzle velocities in the 3001-3500 fps range, the change in velocity for each 1" change in barrel length is 30 fps.
For rifles with muzzle velocities in the 3501-4000 fps range, the change in velocity for each 1" change in barrel length is 40 fps.
The 43rd edition of the Lyman reloading Handbook gave some concrete examples of velocity loss for specific calibers and loads. The Lyman technicians chronographed some high velocity cartridges in rifles with barrels ranging in length from 26 inches down to 22 inches with the following results:
The average loss for the .243 Win./100 grain bullet was 29 fps per inch.
The average loss for the .264 Win. Mag./140 grain bullet was 32 fps per inch.
The average loss for the .300 H&H Mag./220 grain bullet was 25 fps per inch.
safety first, accuraccy second as it's hard to be accurate with a blown up rifle.
