I'm looking at selling the 7+lb 300WSM M70 Fwt I have to get into something that has a little less "bite" on my many times damaged shoulder, and have been studying the Hodgedon Reloading tables to gain some insight into changing powders to get lower chamber pressures, without losing too much MV in another of the 30 caliber variations, and need a conversion factor to mesh PSI & CUP numbers into a common reference table with. Anybody got any idea how to do that?

Probably gonna have to "downsize" out of the 30 Short Mag into a 30-06 if I stay in a 30 cal platform...just got lots of 30 cal supplies, and even considered going back into a 300WInMg and down loading it to starter type loads, that look like will usally get me upper range & + in '06 MV's for bench work, and then a scootch heavier powder load for hunting with it.

Already had moved the WSM into mostly 165gr loads before the house relo move wrecked my time tables for this year which was a little help, but a heavier shooter would prolly help too. Have not seen an off the rack 26" barreled '06 or WSM either, like is fairly common in the belted WMg, and a tad helpful on MV's too.

Any insight would be appreciated.
Ron

Ron, I would just use one of the recoil calculators that are available online. This one is pretty good and have used it several times LINK

Converting CUP to PSI or the other way are not linier or something that I would attempt to calculate a conversion.

Check out Hodgdon 4895 for reduced loads, you can use that powder and load it like a 30-30, 308, 30-06 or 300WSM.

On the main Hodgdon page under the Data header a link to a PDF with instructions for reduced loads with H4895 is there with an example using 30-06. You can find the max load of H4895 and multiply that by .6 for a starting reduced load. Lots of people use that for reduced recoil loads much like Remington Managed recoil loads are.

GTK about the down load tool available on the Hodgedon site that I have been looking at to get chamber pressure #'s. Just never figured out how to convert CUP #'s to PSI, or vice versa.

I've been using the Hunt America recoil calculater site for years and find it to be reflective of my SWAG levels of "felt on the shoulder" recoils in the past...but fast forward about 8-10 years to today though, and thought maybe that by now there would be something out there that could give me more accurate numbers.

Looked at a clean Remmy SPS 308 Varmint at the annual Labor Day Weekend auction at the Civic Center last weekend, but giggled at the +$700 price it went for, and not seeing much offered or affordable on GB caliber wise in the T/Vt styles either and decided to go with a 8-9lb all up field weight shooter that gives me more latitude in calibers and recoil levels, & mebbe try a Boyd's thumbhole stock to help with the recoil levels too. Just need to figure how to find something I can live with and use regularly without having to go thru the buy this'un and try it a while cycle of wasting time & money that are becoming an ever shorter supply the older and less physically able I get.
Ron

Dare I say it? Maybe it's time for a muzzle brake. Not a fan myself, but, as you know, they work well.

I wouldn't rely on this for anything that might be a safety thing, but generally speaking, 60,000 psi is equivalent to about 50,000 CUP in typical modern high velocity rifle cartridges. This is just an observation I have made over the years.

The old copper crusher method uses a copper pellet in the same way Plasti-gauge is used to determine clearances during engine building in that the total dimensional distortion of the pellet is analogous the the cumulative effect of pressure. It does not reveal anything about peak pressure, but rather just a product of time x pressure.

SAAMI pressure testing utilizes a piezoelectric transducer and allows the logging of a pressure trace plotted against time, so instantaneous peak pressure can be determined within the limitations of the system. It's said that peak instantaneous pressure is what destroys firearms, so the advantages of this method over the copper crusher method are apparent.

Some years back, I shot a Savage factory "corncob" muzzle brake a for a while on a 300Wmg. It was not a pleasant experience, worth repeating.

When the old now long departed Out Back Range on Hwy 380 east of Denton was still around, I could NOT shoot the muzzie brake within 3 stations of usually open bench next to the wall at the west end f the CF Rifle Range, even with the plugs and muffs I had then, and have since upgraded.

The muzzle blast shot from even anywhere close to the wall would sometimes blow my hat & glass's off with some of my "full house" loads & my BH would comment on the "sunburn" from the spent powder burns on the right side of my face and neck...but the net 20" long barreled Savage was indeed super accurate, even if the shooters on the other side of me complained about the muzzle blast also. It was a fast way to empty the benchs around me for sure.
Ron

RR RE 300WSM & 300WMg In re looking at the Hodgedon Reloading site this morning, it seems like the spread from slowest to fastest is only about 150/160 fps in most of the older powders I have on hand with the stated 24" barrle length...and about 6-7 or 8000 CUP min/max #'s at most in pressures listed, and I can live with that spread in lower MV's as long as they'll shoot decently. Just may take some tinkering to get the 200 yard MOA's I'm looking for, which is the max distance my local range has.

The clue was to change bullets in the Recipe data to something newer that was tested in PSI, using the same powders and same bullet weight to see the rough 50-52k Cup ='s 60-61k PSI relationship. Would love to be a fly on the wall in a project to re shoot ALL the old data with PSI #'s.
Ron