I know this is not a new idea, and that Lazzeroni has something a bit bigger called the 9.53 Hellcat. However, I have RCBS dies in 300 WSM,
338 RUM and 375 RUM and was fooling around in the last ice storm, finding it easy to mock up a 375 WSM and do some honest case
capacity measurements.

Either a 270 gr Hornady SP or a 300 gr Woodleigh will leave 73 grs of water capacity seated to COL 2.80 inches. This is a good indication
that it will propel the 300 grainer to nearly 2600 fps and the 270 over 2700 fps. Sounds a lot like the 'ol 375 H&H in a short action to me. For
long shots the 225 gr Hornady will do over 3000 fps...all from a 22 inch bbl.

Now, the 375 WSM is certainly a brut of a rifle round and will bump you with 46 FP of recoil in an 8.5 lb rifle, so a few reduced loads make
sense. Around 42 grs of XMP5744 will launch the 225 gr Hornady at 2540 fps in this case, dropping recoil to 22 FP in the 8.5 lb rifle, putting it
in the 30-06 class. Several "35 Whelen duplication loads" can be fashioned with this power/case combo covering weights from 225 to 250 grs
in the 375 caliber.

I have done this in the much larger 375 RUM with these components, using about 60% load density with fine accuracy and similar recoil
reductions...however, the bigger case takes more powder and recoil is more like a 338 Win Mag.

In any event, I am intrigued by the flexibility of the 375 WSM as it appears that it will deliver a sizable whack at moderate recoil levels in a
sporter weight rifle and then step up and flatten dangerous game when recoil is not the primary issue.

Anyone have an interest in building one of these?

My dad and I did a .375 WSM on a VZ-24 last year......your velocity estimates were pretty close to what I was getting out of a 24" barrel (the recoil isn't that bad either, even with the 300s).

Lee Martin
www.singleactions.com

I have a MRC SA with the Magnum Boltface and am highly interested in this round. Did you lose any cases in the necking up process? Did you have to step to .338 in between?
I am looking at a #4 Pac-Nor tube 22" long and a McMillan in the Winchester Supergrade pattern. Banded NECG front sight, Talley Rings and bases with a backup rear peep. Leupold 2.5-8x36 with the heavy duplex or German #4. I think it would be great for bear, big hogs or deer when loaded down to Whelen specs. My smith has the reamer, I just haven't made the plunge...

Chris.....we've formed over 100 cases and have yet to loose one in the process.

Lee Martin
www.singleactions.com

The 300 wsm x .375, aka the 375 jamison, is within a cuople grains of the 376 steyr (i think 2.5, but i don't have the data in front of me)

The 376 feeds like minnows dodging a bass, in a mexican mauser...

the 375 wsm will present some challenges to get to feed properly. It can be done, with some patience.

the 376 steyr is an exotic, though factory round. dies, cases, and brass are available

the 375 wsm will require more bucks

I have a 376 steyr finishing chamber reamer... I don't for 375xwsm

with a 24" barrel, i can get OVER 2500 fps with a 300 grain hornady... but that's max... i load it to 2400...

i can get OVER 2900 with a hornady 225 grain.. and I load it to 2800....

dies where CHEAPCHEAP, ad brass was about 40-45� each



both are great, just wanted you to know that you wuold be spending ~300-450 bucks extra to deliver a 376 steyr...

jeffe

Jeffe....btw, thanks for all of the load data you sent me on the .375 Jamison (worked well for in my .375 WSM).

Lee Martin
www.singleactions.com

Lee,
NP... how close was it?
jeffe

Very close.....you were right, the .375 WSM and .375 Jamison are nearly the same with respect to case capacity/velocity (within 1 grain for most loads). Thanks again.

Lee Martin
www.singleactions.com

I think i'll run a comparison between the 375 jami and the 376 steyr, at 50, 55, and 60,000 psi, with 225 hornady and 300 gr woodliegh rn's... and post the velocity results.. i've foudn quickload to be pretty durn close ... especially with my 376, 416, 458 and 500

jeffe

Chris -

I am certain there will be no case forming problems. I make nearly all of my 375 RUM brass from 300 RUM using 338 as a step up and it is no problem.

Please send me the phone for your Gunsmith as I might ship an A&B barrel blank in 375 for my 300 WSM Savage 110. He will not even need to headspace it...just finsh ream it and send it to me. I put on Savage bbls all the time and headspace them while screwing them on.

I won't need any other changes and it feeds fine now, so it will only feed better with a smaller diameter increase from neck to shoulder. Anyway, that will allow me to swap the bbls back and forth between 300 WSM and 375 WSM.

I can't fit the 376 Steyr into that magazine, so its 375 WSM or nothing. Seems like they went to a lot of trouble to make the Steyr with the WSM case in the wings.

The 358 WSM is nice too, since one can shoot .357 pistol bullets out of it. If one shaves 25 grs off of the 375 bullet weights, you get the same velocities in the 358 WSM.

Sabot,
I heartily agree they are both great rounds... but, heh, I can't see why winchester would copy jamison's wildcat, with the 376 being so easy to get to feed in mauser (little self dpreciation for me, here)


Here's my PROJECTIONS of MV for the 375 jamison vs 376 steyr

Quickload Estimates
24" barrel
3.11 oal for steyr
81 gr water cap

2.86 oal for jamison
85 gr water cap


375 jamison
300 woodleigh

50000
2455

55000
2520

60000
2551


376 STEYR
300 woodleigh
50000
2430

55000
2480

60000
2510


375 jamison
225 hornady
50000
2789

55000
2855

60000
2925


376 steyr
225 hornady

50000
2765

55000
2831

60000
2901


Less than 50 FPS, and the steyr is has the benifits of being a factory round.... that's 90 bucks a foot per second...

jeffe

Great.
Now, set them both at the same COL.
Fair is fair....

I have thought about it. My first idea was to rebore my super shadow 300WSM. Rebarreling would cost less though.

This is not the aka 375 Jamison it may be similar but it is not the same. Arent the jamison done on the 425 wes-rich?
All short fat cases do not rip off Jamison anymore than all 20 cals rip off Todd Kindler. There are probably 20 different versions of every wildcat you can think of.

If I made an 30-06 action into a .375 I would do a .380 Howell. Or open the boltface and make a 375 Dakota.

Sorry Jeff but you can't sell me on a 376 Steyr.

For now I know I can just load my 375 RUM down if I want to duplicate any of these .

Well, I know Jeffe's going to jump on this, but I got here first!
If it'll fit 3.34", then WSM and Steyr are both out, but if it'll fit Steyr, then it'll fit WSM out to 3.1" as well.
The Jamison is off of 404 Jeffery cases - very similar to the W-R but no rebated rim. Virtually identical to RSAUM cases.
THE 3.1" round will always be a 2.33" 404 case. So close to factory H&H it'll make you weep (but just a little bit, while no one is watching.)
So, if you have a SA M70 kicking around....

Is the Steyr a short action case? I though it had to fit in 30-06 medium actions .

BB,
heh... sure, i'lll much with the factory oal's... soon as someone says "well, make the oal on the 300 win the same as the 300 WSM and the WSM will beat it".... LOL.. yeah,,, aint an apples to oranges then... the steyr is longer and thinner, the wsm aint... good opinions on both

the jamison is based off the 404...

btw, winchester, like remington, SAYS their's a "unique case design"... hogwash

let's get the "proper" framework here gents... the x57 rounds ALLL fit in MAUSER short actions, without <real> mag mod. This includes 257 roberts, right?

hmm, that's interesting... the 376 fits RIGHT into my 1936 mexican short action. It's quite a bit of work to just get a 30-06 to fit into one of those... but, then again, I built my son a 458 winmag in a 1910... it's limited to 400/405 grain bullets at 3.125 ... but it's NOT a dgr... it's his range pop gun.



Guys, the 375x300wsm would be a great round... the reason winchester hasn't put it out is that it's a match for the 376 steyr... which was not a commerical success... and come out the at the same shot show as the 300 wsm

myself, i can't wait for a factory 338x7wsm to appear...

why the 7wsm when i just blasted the 4 grains difference as marginal? Becuase if winchester does make it, I would like to see the "biggest" case from the factory, in the line.


opinions vary, that's why there's 500+ calibers and horse races

cheers
jeffe

Heh..

good one... IF i was building a true widcat, I would have a RUM cut down to 2.5 inchs.... and run it at 3.25...

since the 376 is just about the equal of the 375 jamison, I wouldn't spend the cash to get 50 FPS difference!!!

cheers

jeffe