Loading for a Ackley Improved

It depends on the amount and percent of case capacity increase. Neither the 7mm-08 AI, nor the 260 Rem AI gain much more than 3-4 grs, i.e. 6-8% over their parent cartridges. That being the case, and wanting to keep max pressures the same, for those two cartridges, you could only add a maximum of 3-4 grs more powder, and only for the slowest powders listed that are already loaded to compressed, full or very nearly full in the parent cartridge, and then as a sanity check, you should only expect 50-75 fps more MV.

This is a simplistic approach, but it's one that prevents you from putting pressures through the roof by relying on subjective and deceptive "pressure signs".
 
Well, I did the FIRST part, about a slower powder (IMR 4831) but then that part about starting somewhere near the middle of the chart would have been good to read a while back when I loaded some 7 x 57 Improved. I started 1.2 gr higher than the max load in one of my manuals..............Hey, you've got a hot rod you don't want to run it in idle, right?

I have posted a request for any tested 7 x 57 Imp recipes, on a separate thread.

And I am going to order that PO Ackley book, looks interesting and not expensive either!

Doug
 
One of the big variables in the 260 Rem AI is the throat depth. Mine is deep, intended for the 142 Sierra. If your chamber throat is shorter, my loads would be very hot.

I form virgin brass with 45.5 gr of 4895 and the Sierra 142. Accuracy is superb. I use them in the short range shoots (300 to 500).

For the formed cases, I 47.5 gr of RL22, or 51 gr of RL25, or 48 gr of 4831SC.

These are max loads. Work up from less with your rifle.
 
So the books don't show a lot of the AIs out there and I was just wondering what you use as a starting point when loading for a AI vrs standard cartridge. Ex 7mm-08 vrs 7mm-08AI or .260 vrs .260 AI

Go with what Ganderite has said here, all reloading data is "ball park" because of variations in reloading components and the firearms themselves.

I have a Powley computer from the early 1960s and "had" Quickload that also gave me "guesstimates" when you feed it even more information. And they are still nothing more than "ball park" figures and Quickload is even more worthless if you do not have a chronograph to use to calibrate the information it spits out.

So start at midrange for the parent cartridge as Ganderite said and work up and let the brass and primers tell you a story.
 
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