30 sherman magnum

[Phil Rizzo]

Dont be surprised if you see great accuracy with the FF loads.
reduce load 5% at least, and use up your least favorite components.
Engaging the rifling when seating ensures alignment in addition to what VLD said.
It may take another firing to get them 100% but they will be done for the most part after the first. Some suggest a slightly faster burning powder.
Good luck, you are going to have a Beast !

 

[QuietTexan]

I know some people are just buying factory 300PRC ammo and getting brass that way, so I assume I should just load up my brass to spec for 300PRC using a starting load (say 75gr of H1000 under a 200gr SMK) and call it done?

Yup, it's that easy. I used 73.0gn of H4831 behind a Berger 208, got 2800FPS from it. Yes on the slow side but formed the cases well enough, I don't usually push brass hard on the first firing even if not fire forming the shoulder.

I was using Rich's 30SM headstamped brass, it came in 50fps faster than projected due to slightly less case capacity than I had entered into QL. I'm basically getting mid-range 300WM factory load performance out of a soft load that's fun to hit steel with, I don't see a single draw back to needing to fire form the 30SM cases. When I upped the powder to 75.0gn I was getting 2950FPS, so basically matching full-house 300WM and still below 300 PRC book max. Way below 30SM max. Rich hit a home run with this design.

Dont be surprised if you see great accuracy with the FF loads.

100% agree. I couldn't miss a 10"/2MOA plate at 500 yards with my first wild-guess fire forming loads in my last 30SM barrel. From the grouping on the plate I could have been hitting the 5"/1MOA plate just as easy, but didn't want to miss any hits to see a real aggregate group size. Steel misses don't really help much in that regard Mainly I think that shows the quality of the barrel job I got that it shot so well so soon, one big plus to getting something like a 30SM made instead of buying off the shelf.

 

[snox801]

Yup, it's that easy. I used 73.0gn of H4831 behind a Berger 208, got 2800FPS from it. Yes on the slow side but formed the cases well enough, I don't usually push brass hard on the first firing even if not fire forming the shoulder.

I was using Rich's 30SM headstamped brass, it came in 50fps faster than projected due to slightly less case capacity than I had entered into QL. I'm basically getting mid-range 300WM factory load performance out of a soft load that's fun to hit steel with, I don't see a single draw back to needing to fire form the 30SM cases. When I upped the powder to 75.0gn I was getting 2950FPS, so basically matching full-house 300WM and still below 300 PRC book max. Way below 30SM max. Rich hit a home run with this design.


100% agree. I couldn't miss a 10"/2MOA plate at 500 yards with my first wild-guess fire forming loads in my last 30SM barrel. From the grouping on the plate I could have been hitting the 5"/1MOA plate just as easy, but didn't want to miss any hits to see a real aggregate group size. Steel misses don't really help much in that regard Mainly I think that shows the quality of the barrel job I got that it shot so well so soon, one big plus to getting something like a 30SM made instead of buying off the shelf.

Same was getting great groups with random ff. Loads at 400 yards

 

[tyler6593]

I just went through fire forming my brass. 75 grains will work good for the fire forming. I went lighter on powder than I should've. I jammed as well. Took me two firings to get the shoulder blown out to match the chamber.

 

[synfinatic]

Dont be surprised if you see great accuracy with the FF loads.
reduce load 5% at least, and use up your least favorite components.
Engaging the rifling when seating ensures alignment in addition to what VLD said.
It may take another firing to get them 100% but they will be done for the most part after the first. Some suggest a slightly faster burning powder.
Good luck, you are going to have a Beast !

Just so I'm on the same page, but you're saying reduce the load an additional 5% below the starting load for 300PRC? I don't really have anything suitable for magnum cartridges faster than H1000.

 

[Phil Rizzo]

Mr Rich, what specifics do you have to offer concerning powder burn rate and charge?

 

[elkaholic]

Mr Rich, what specifics do you have to offer concerning powder burn rate and charge?

You can fire form with upper 300 PRC loads just fine. About 77 H1000 should work great

 

[synfinatic]

Thanks Rich!

 

[VLD Pilot]

I use what I use for all my loads. N570 works great. Not hot loads but with the 225s, I ran them around 2950 for fire forming. Hunting loads are 3050-3075. Course my FF loads I also use for hunting.

 

[Phil Rizzo]

Got almost all my 30 SM parts in hand, ready to get going !
I hope it likes N568, got enough to feed it a while.

 

[Will.284]

This was formally the 300 PRC S.I. for those who missed it.
I got out a couple days ago to do some more testing and the mirage shooting over the bright snow was terrible so I couldn't really accomplish as much as I wanted to. I did get some velocities and enough data to make another run on a couple loads when conditions warrant.
I ran some 225 eldm's at 3059 with N570 that showed potential
I also shot some 215 Bergers at 3167' that also looked like they need more testing.
Below are pics of the brass which didn't show any over pressure and a pic of the 215 Berger group. I think in better condition this load would cut a single hole.View attachment 127740 View attachment 127741

That's a sexy caliber. Thought about one many times

 

[synfinatic]

Just wanted to update that I finally went out out to the not-so-local range (3hr drive each way for me). Just shot the fire form loads (77gr of H1K as Rich recommended) and gotta say, I was impressed with the accuracy considering zero load development. Was shooting 1moa @ 1000yds after doing the initial barrel (Straight Jacket Armory) break in.

 

[Polaris_Doc]

Does anybody have measurements for the 230 Berger hybrid Target, BTO and overall length touching the lands? Thanks
And if known, loaded long like that, does it crush on a max load of n570?

 

[Taylorbok]

Does anybody have measurements for the 230 Berger hybrid Target, BTO and overall length touching the lands? Thanks
And if known, loaded long like that, does it crush on a max load of n570?

Mag length? There's several ways to find your measurement without the gauge. You might have issues with a "max load" but that's pretty spicy IME