You need a bit of room for the cartridges to work in the magazine. .010" is enough. I seat mine at 3.060" in the two short action M70's I have in this cartridge and they work fine. I've tried the dummy rounds in the the MRC action and they also work with about .010" clearance. I can seat them out to 3.080" apparently. I'll know when I start shooting it. Mine were throated to permit seating out further.



As for use of the 7mmWSM case, apparently the webs are thicker than those of the 300WSM cases. I expanded some and had EXACTLY the same water capacity in both, 83g. There was NO capacity advantage in the 7mmWSM, at least in the lot of brass that I compared. Additionally, the Norma brass in 300WSM is heavier than WW brass. Its water capacity is 1.2g LESS than our domestic brass.

In the current issue of Guns & Ammo there is an article on the wildcat .338-.300 WSM, which the author refers to as simply the .338 WSM. He admitted his load development was brief and incomplete, but he reported somewhat negatively about his less-than-expected velocity results. He used IMR4895 with 225 grain bullets and only reached 2600 fps.

My suspicion is that IMR4895 is too fast for this case capacity and 225 grain bullets...not an optimum choice. What's your view? I would guess a slower powder, maybe 4350 would be a better choice and that with that wildcat you should be able to hit 2800 with 225 grain bullets.

Maybe someone with Quickload could comment?
Jerry/AK

I've run loads through both CalcuLoad and Quickload, but didn't need to since I've put them through a couple of barrels and chronographed them. The cartridge was the 338/300WSM. 225 loads maxed out at about 2840fps using propellants much slower than IMR4895. 210's and 215s were at 2900fps and 185's at 3000fps. 250's were the ones that just barely made 2600 fps. The bullets, when seated for short actions, intrude too far into the powder chamber of the case. Faster powders give pressure early, and you can't get enough of the appropriate slower powders to get going much faster than that.

I had my MRC 1999 throated to be able to seat bullets out to the maximum magazine length - which is substantially longer than the factory version. I assume I'll be able to push heavier bullets at more velocity by the gain in case capacity. Would you assume so also?

DeanAK

But Bob, were you able to seat your bulelts out to 3.08"?
Just because the mag will hold them doesn't mean the reamer was made to allow it.
As I recall, the COL of the WSM's in general is ~2.8", and the other .28" is wasted on the M70.

i STILL think using the 7wsm, rather than the 300, is a better idea, larger case (gimme a break, it's like 1.5 grains... i've seen guys spend 600 bucks for 1.5 grain more than a factory round) and zero difference in receiving the brass
jeffe

Bob,
DeanAK and I would like your loading info please. If you don't want to post it here, would you PM either of us? Thanks.

Also .35/.300 WSM info if you have any.
Jerry/AK

I would like to see that info as well please, Bob. I'm considering rebarreling one of my scout rifles into a 338 WSM WSM or 35 WSM. Thanks. - Dan

No problem posting it here. If you want more, PM me and I'll send it. I'll post the most accurate loads for each bullet weight. Velocity over Oehler 35P. All these loads are HOT, and on the edge, usually backed down from loads with pressure signs.

185 Barnes X, H414-73g, WLR, 3001fps.

200 Nosler, Varget-63g, WLRM, 2899fps.
200 Nosler, RL19-72.5g, 210M, 2890fps.

210 Nosler, N560-73g, 9�M, 2853fps
210 Nosler, H4350-69g, 210M, 2887fps

215 Sierra, RL19-73g, WLR, 2843fps.

225 Hornady, H4350-70g, 210M, 2804fps.
225 Hornady, RL22-75.5g, WLR, 2830fps.
225 Hornady, N560-75g, WLR, 2828fps.

I have much data on other propellants, some faster than these but less accurate. Also many VERY accurate, but far slower by about 50-100fps. Also have much data on the 338 Jamison which has the identical case capacity as the WSM.

With 250g Partitions best velocity was 2643fps. Not accurate and on the edge pressure-wise. Remember, your mileage may vary.

Jerry,

Say it ain't so, you haven't sold out to the 33 calibers have you?

BTW, have you had a chance to try the 280 gr cast bullets yet?

Paul,
No, I haven't gone off my rocker and switched to any wimpy .33 caliber rounds. It's just that my good friend DeanAK is doing a .338 WSM and he wasn't onboard yet with AR so I posted his question. MY new rifle is a .35 WSM! (Our rifles are MRC's with sequential serial numbers.) We're a couple of weeks away from being ready and able to take them to the range for testing. That's when I'll try some of your 280 grainers in both the .35 WSM and the .35/.284. Will report results here on this board when available.
Jerry/AK

Jerry/AK,

I can not tell you how this round will do in a rifle but can tell you that in a 15" custom XP-100 handgun, it is simply the most impressive round I have yet to hunt with and I have taken big game with over a dozen different handgun rounds.

My handcannon has a 1-12" Lilja barrel which was chosed because I wanted to use bullets from 180 to 225 gr and no heavier. I figured the slower twist would help add a little velocity at slightly less pressures.

Most do not believe me when I tell them the performance I get with my handgun but it is simply true.

With the 180 gr Ballistic Tip over 69.0gr Rl-15 and loaded to an O.A.L. of 3.075"(very long for the WSM) I get an average velocity of 2960 fps at 60 degrees F.

Extreme spread for 10 shot strings will run under 20 fps and 1/2" three shot groups are very common. This is the most accurate load for this handgun.

It also likes the 200 gr Ballistic Tip with the same powder and will average 2810 fps with sub moa groups.

The heavier 225 gr Hornady bullets will hit just shy of 2700 fps with similiar moa groups.

All of these bullets are impact coated with moly.

Yes, these are hot loads. In fact after the fifth firing, the primer pockets are ready for retirement but I have yet to have one leak.

I have taken several head of game with this handgun with the 180 gr load including a +325" 4x5 mule deer at a measured 317 yards with a single shot.

Out of a handgun this is a truely impressive round, it would be even better in a light weight rifle.

Good SHooting!!!

50

Fiftydriver,
Your results are very impressive. I hope you realized I was just poking fun. I know that the .338 WSM and the .35 WSM are generally two peas in a pod...sort of like the 280 Remington and the 30-06.

Anyway, if you can reach those levels with your 15" barrel that's a good indicator Dean and I will reach our goals in our 23" barrels.

Thanks for the post.
Jerry/AK

I didn't mention the barrels on those for which I posted velocity. Both were 21" barrels, one of which is a gain twist.

Jerry/AK,

I love the idea of the 35 WSM, but the next short mage I build that isn't the 6.5 WSM will either be the 375 or the 416 on a Ruger short action.

Perhaps even in one of my spare Xp's??

Good Shooting!!!

50

I need to correct an error in one of my posts.

I typed that I took a +325" muler deer at 317 yards.

Before some of you start thinking I'm crazy the " should have been lb.

I shot a +325 lb mulie at 317 yards.

Damn wish it was a +325" buck.

Sorry for the typo.

Good Shooting!!!

50