Sorry, I don't have any data, but I'll toss out these words of wisdom:
While wildcats can be fun, they aren't standardized and you're on your own for working up load data. There's no telling how many 'improved' .270's out there, with different shoulder angles, body diamters, and throat lengths. Even if it's an "Ackley" improvement on a standard .270 Win chamber, there may exist more than one variant.
Having said that, when you open up a chamber and take out more metal to increase powder capacity, one thing that you can be sure of is that the pressures will drop as compared to the original loading. So, a good starting point for your improved .270 Win load development would be near-maximum .270 Win loads for the standard cartridge, and work up with a chronograph and good micrometer. Clearly, not a good place for a novice handloader to be.
Do check out Ross Seyfried's article on pressure in the latest Handloader. Might give you an idea if you feel up to tacking such a project.
Over in the Wildcats forum I was asking questions about this round last summer. Go back to around July (page 5 currently) and you can see what others had to say. Also you'll see an address for PO Ackley's son-in-law who was more than happy to converse via email. There was quite a wide spectrum of answers to my question(s). The final response made the conversion seem worthwhile but I didn't pursue it. Factory rifles chambered for new cartridges with similar ballistics seem to be on the horizon, and I decided to wait it out. The prospect of a 270 Rem UM or 270 WSM makes spending dollars on custom work worth putting off (IMHO). Especially if buying a conversion piece with longer barrel (or adding a new barrel) is required to get the most out of the wildcat anyway.
Whatever you decide, it's fun to consider the possibilities...
I've got the reamer and haven't had the time to rechamber my rifle. i would suggest trying IMR 7828 and Reloader 25 before you wasted a lot of time on the faster burning powders listed in the old data. Especially if you're planning on using 130-150g bullets. I'm basing this on my experience with the 25-06 AI. I achieve higher accuracy and better velocity with IMR 7828 than any other powder. Much higher velocity in fact. I'd start by fireforming the brass and working up from what the listed maximum for the standard 270 win. is. Hope that helps!
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