270/7mm wildcat.

[wuz]

Hi, can anyone please tell me if there is a wildcat cartridge in 270 or 7mm based on a 284 win case shortened to 51mm (2.030"=308 case) to fit properly in a short action? The 284 case is the same length as the 6.5 x55 so really isn't a short action cartridge.
My alpine rifle is currently built on a modified Rem 700 short action and comes in at about 5lb bare, or 7lb with its Swaro Z5 scope, Gunworks spartan overbarrel suppressor, MTN gear carbon/Ti bipod, sling etc. Its v accurate and great in the mountains. It's currently chambered in 7mm08, which is an excellent cartridge out to about 600m (650yd) ethical range on big game. However, Id just like to squeeze the most I can out of a light, short action rifle. Praticularly to minimise wind-drift, and maybe even give me another 100m or so range.
I don't want to go to a magnum bolt face for two reasons. 1. Recoil. Its a light rifle and gets lively, even w a suppressor. 2. I don't want to have to build a whole new rifle.
So is it doable to alter cases to move a 284 shoulder rearward, without serious engineering equipment? Is anyone else doing it? Im aware I'd need dies made, but is it going to be in the to too-hard basket? Would I just have to chamber in 284W and seat the bullets deep in the case
Cherrs

 

[NorthIdahoDude]

The cartridge you are describing would have a case capacity of around 62 ish grains of water, and be a real b***h to form brass for. 7mm-08 AI with some thinner brass would have ... about 59 to 60 grains of water capacity. Not enough difference to matter. Honestly, my 7x57 with 61 grains of capacity, loaded to modern pressures, is only about 40 FPS or so over a plain jane 7mm-08 with 56 or so grains capacity.

If you really wanna make 7mm bullets hum, you need a long action and a 280AI minimum, or a 7mm SAUM.

Or, if you really really want a 284 Win in a legit short action, 7-6.5 PRC is for all practical purposes, exactly a 284 win. Is mag bolt face, but would otherwise get you exactly what you want, and a smith can mod your rifle pretty easily.

 

[NorthIdahoDude]

You could also look into have Defensive Edge do you a Plus P throat on your current rig. My loose understanding is, they alter the throat geometry to drastically reduce start pressure, which is the primary driver of peak pressure. That lets you run more powder/higher velocity without over pressuring in any given cartridge (100 to 200 more FPS I think is the claims).

 

[wuz]

Haha, thanks. I thought my idea might fall in the too-hard/ not worth it basket.

I'd considered going 7mm08 AI, but the extra possible 50fps doesn't seem worth the hassle of forming brass, and cost of rebarrelling. I'm currently shooting 140gn Nos BT/ABs at 2850fps.

I'd also considered the 7-6.5PRC and the 7mmSAUM. The 7-6.5prc does seem v close to what I'm looking for, if I was to go for a magnum conversion. Only thing is, if I was to go that direction, I might as well just go with a 6.5 PRC, since 140gn high BC bullets at 6.5PRC velocities should drop any game here in NZ out to further than I can shoot, and I won't have to mess around forming brass.

How does 6.5PRC feed from a Remington or Wyatt internal staggered box in a Rem700?

I dont think the +p converion is an option in my part of the world, though thanks for alerting me to it.

Cheers

 

[NorthIdahoDude]

Just a thought, with a Wyatts mag box, you get a max OAL of 3.0 (or 2.99 ish) inches if I recall? That's a bit tight, but doable for a 284 Win. I'm not aware of any mainstream bullets that have a tip-to-ogive measurement longer than .8 or so, which would put your OAL at 2.98-ish with the ogive set just ahead of the case mouth. Sure, you're intruding on powder space a fair bit, but you'd still be getting about a 10 grain upgrade in net capacity over a 7mm-08, which is enough to make a significant-ish jump in velocity.

Using QuickLoad and a 168 Sierra SMK for my test case:

7mm-08, at 2.87 OAL (max in my AICS poly mags, not sure if your current setup would go that long?), gets you 48 grains of net case capacity. A max-ish load of H4350 would put you around 2590 FPS (at 5% compressed)

284 Win, at 3.0 OAL, gets you 58 grains of net case capacity. Lightly compressed max ish load of H4831SC should put you around 2740 FPS in a 22 inch barrel.

Or if you want to stick with having a wildcat (ish) cartridge:

284 Shehane (approximately a 284 Win AI), at 3.0 OAL, gets you 60 grains of net capacity. A lightly compressed max ish load of H4831SC would put you up around 2785 FPS in a 22 inch barrel.

So even with the choked down OAL, you should one-up your 7mm-08 by 150 or so FPS in a straight 284, and near 200 FPS in a 284 Shehane.

That said, your original premise is correct, a 2.8 OAL per SAAMI spec on a 284 win, is not workable with modern high BC bullets, because the ogive ends up below the case mouth, which is never a good plan. But a 2.99-ish OAL, it's doable.

All that said, there ain't no free lunch - that will jump the recoil very noticably in a lightweight rifle. Per kwk.us, your current setup is probably around 17 ft-lbs in recoil (not counting any reduction by the suppressor), and the 284 Win will jump that up to around 22 ft-lbs, so a bit more than 20% increase over whatever you've got now.

 

[hereinaz]

True short action magnums:

25 Sherman Short Tactical/SAUM shooting 133/134
6.5 Sherman Short
7 Sherman Short