Why don't you tell us how you Really feel about the .270 Winchester.
This is what P.O. Ackley... thought:
"...But the 270 Winchester Ackley Improved was a different story altogether,
another customer request that resulted in a wildcat inferior to the standard cartridge.
P.O. wrote that the standard 270 was already "over- bore,"
so a 40-degree shoulder with minimum taper couldn't offer much improvement, if any."
P.O. ACKLEY FIREFORM IMPROVED WILDCATS FROM CURRENT FACTORY CARTRIDGES
Cartridge - Performance Gain over Factory - Ackley Comments
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270 Win.Ack.Imp. - Little or none with more powder - Not recommended, factory 270 is better
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GR
I think that might change if Ackley had access to some of the powders available today. He felt a number of the Imps were already so overbore, that they were not worth improving.
If i remember correctly, the best option for that class of overbore cartridge were the 4831s, or perhaps even the 4350s.
Personally i prefer the Gibbs to the Ackleys, simply because almost all of the 06 based cartridges have kinda long necks (IMO), and the .270s are longer than the rest.
Again its all academic, they all do just fine for nearly anything you could ask of them.
I do feel the 277s got short changed on the twist. But since they WERE ment to deliver relatively light bullets at very high velocity, and shooting long, heavy VLD type bullets is a relatively recent phenomenon, I cant really fault the design for that.
This dosent mean I wont fix that issue, and use a magnum case, if i ever get around to building a .277 bore rifle.
Comparing the 120-130 class, 6.5 projectiles to the 140-147 class, dosent change a whole lot when were talking about deer imo.
BUT you do get about 150fps more velocity, and adequate penetration, so it might be worth swapping down, Ive certainly considered it. If i didnt load for a 6.5-284 as well as my 6.5CM I think id probably shoot 120 class bullets exclusively, but I prefer more weight in the x284.