Ackley Improved Question...Experts needed...

n/an/a Member Posts: 168,427
I have both volumes I and II of P.O. Ackley's Handbook for shooters and reloaders. When looking up the load data for .300 Improved Magnum, it says "Loading data is same as for the .300 Weatherby". Now...Here's my question...We all know that Weatherby calibers are designed around the freebore concept, to reduce pressures. Standard and Ackley Improved calibers are not. Am I going to see excessive pressures loading Weatherby loads into my Ackley cases, which will more than likely be seated .005" off the lands.

I also noticed something else that is very interesting...and I'm assuming it also has to do with the freebore concept. If you look at the load data for IMR 4831 or 4350 for a 200 or 220 grain pill, the .300 Win Mag has almost identical velocities as the .300 Weatherby...and it does it with less powder!...a couple grains less powder! I'm assuming that my advantages might be seen with higher velocities than the .300 Weatherby, while using Weatherby loads...Is this a correct assumption.?.?

All three of these cartridges are overbore...I don't want to be using more powder to achieve the same thing I can already achieve with a standard .300 Win Mag...thus causing faster throat errosion, etc...but if I'm able to achieve better velocities b/c I've done away with the freebore concept, I can see a potential advantage to the Weatherby loads in the AI.

What are your thoughts.?.?

Do I use the Weatherby loading data as PO Ackley advises...and if so, do I have to worry about my seating depth.?.? ...or do I seat like a standard caliber and expect higher velocities???

All thoughts would be greatly appreciated![:)]


  • MIKE WISKEYMIKE WISKEY Member Posts: 9,297 ✭✭✭
    edited November -1
    see my reply in the 'experts' section.
  • JustCJustC Member, Moderator Posts: 16,038 ******
    edited November -1
    the shoulder of the AI design, IMHO, helps boost velocity with less powder by increasing pressure with the 40* angle of the shoulder. WTHBY uses a venturi shoulder design.

    The powders you are looking at are a bit fast,..if it were me, I'd be looking to R25, N165, 7828, H1000, etc. I like a full case of slower powders, but that's just me.

    As for data, and with AI's, I would start at just under max for the parent case, and work up with a chrono. The chrono will tell you when you have gone far enough or too far because the AI cases have a habit of withstanding great pressures and NOT showing signs. That is one thing about the 40* shoulder and a case that fits the chamber well. I ran a 6.5-06AI with 140gr pills up tp 3208fps[:0] I didn't realize how much pressure was present until a chrono'd them,....incidently that explained why the primer pockets were toast[;)]
  • MIKE WISKEYMIKE WISKEY Member Posts: 9,297 ✭✭✭
    edited November -1
    this is my rifles 'sweet' load.
    case= r-p .300 weatherby
    primer= fed. 215
    bullet= nosler 165gn. b.t. (molly)
    powder=rl-25...95.0 gns.
    oal= 3.890"
    vel. 3524 (average of 6)
    sd. 7
    will usualy group .75" or less
    the barrel is a match quality (maker unk.)1/12 twist 26" long, throated about 1/4" longer than the standard reamer. bullets seated about .010" off the lands. note that this load is safe in MY rifle and case life is indefinite, ymmv
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