25 Pronghorn Preliminary Range Report

[T_Widdy]

The 270 is .010 longer to the shoulder and .022 longer to the neck


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I believe Hornady is wrong, look at the actual Saami prints. I thought the same as you.

 

[cal30_sniper]

I’m interested in if you have any issues with the 270wsm brass? I thought win/baco made the 270 longer to the shoulder and neck junction than 300. Are you able to push them back with your die or was your chamber reamed off the longer 270 print?

270 WSM and 300 WSM (and 325 WSM) all use the same shoulder datum/headspace. Simple neck down. You may be thinking of 7mm WSM which has different dimensions than the others.

Neither cartridge is easier than the other the 6saum imp you literally neck down brass, load, shoot and reload. Same as your doing and would be doing with a 6WSM
The saum and saum imp are already diminished returns in 6mm the wsm case would be a waste.
The easy button 6mm is the PRC

I’ve done scads of improved cases for my 7x57AI. Fireforming improved cases is several steps more complicated (including consumption of extra components in the load shoot reload phase you describe above) compared to a straight neck size operation. These 25-300 cases come out of the sizing die as close to chamber spec as any other virgin brass in a SAAMI chamber.

My cases are holding 81grs of H2O after firing. 6 WSM would probably be 79-80grs with the smaller neck. Not sure what 6UM 40 deg holds, but it’s a big jump over 6-284 or 6PRC, so I’m guessing they’re close in capacity to the WSM case. Hence why I’m wondering why folks would go through fireforming to blow out the shoulder and form UM when the WSM is already there with a neck size.

 

[cal30_sniper]

I hope the OP doesn’t find my posts as an intrusion, did a ladder today with H1000, Fed 215 M, from 60-63.5 gr and 134s. Never hit pressure, started at 2960 with 60 gr and ended at 3115 from a 26 inch barrel. I have room to go but I’ll switch to N570 and let it rip.
More to come.

Keep it coming! I’m interested to see where you end up. 3200+ shouldn’t be out of the question with that long of a barrel.