Home Forums Hunting & Shooting Ask The Gunwriters What's Petzals beef with the 7mm RM?

I think we should change the subject to truck tire sizes.

Looks like a hotly loaded
7mag to me.

Looks to have be AI'd

Don't know about that. Looks overbore though.

Fugg the 270 WCF and the WSM. Pass me the 270 Roy with a 150 LRAB at 3250 and I'll be happy!!!

The problem with questioning the ability of the 270 Winchester as a general purpose cartridge for any North American BG animal in 2014, is that it's like coming to bat in the 10th inning when the game was won in the 9th, the stadium is empty,and everyone, except the guy at bat, has gone home.

It's already been done on everything from elk,Yukon moose and grizzly on down not dozens but thousands of times by now(if not tens of thousands).

If anyone has doubts,they are about 80 years late to the party.

That about sums it up...

QL estimates 65,000 psi at 3150 fps...

Love it. You put it very succinctly!

Plus its a Weatherby...

QL doesn't account for Wby freebore. In addition, Weatherby's factory 270, 150 gr offerings are listed at 3245 fps. Also, Weatherby ammo has a rep for making advertised numbers. 3250 with 150's isn't a problem.

So have you chronographed your 150's at 3250 fps? Freebore or not, you're probably running higher pressure than you think if you're loading them that hot.

Do you have any experience loading the 257/270/7mm Weatherby family of cartridges? If you do, you should know that reaching factory advertised velocities is not a stretch.

I don't shoot 150's in my 270 Wby as they're not as accurate as the 130's. I have however, tested several load combos with various 150's and have reached almost 3300(150 NBT) before pressure signs. Folks who own and load Weatherby cartridges know that factory ballistics can easily be obtained, safely, using modern powders. Doesn't sound like you're in that group.

Snapshot from Weatherbys website...factory ammo ballistics.

I could never hit Weatherby published velocity figures for my .257 WM . But it did have the 24" tube and not the 26. Still I fell 100 fps short.

So I assume you're using pressure testing equipment, then? Just because a factory makes ammo, doesn't necessarily mean it's within the pressure ratings that I want to be running in my rifle, and just because you're not seeing traditional pressure signs, doesn't mean you're under 70k psi. Some Weatherby ammo sounds a lot like some WSM factory ammo.

So far I've usually been able to match Weatherby factory velocities by using Norma powders, which are what's used in the factory ammo. In fact it's pretty easy to duplicate the powder charge by breaking down a factory round, weighing the powder, then using Norma loading data to figure out which powder it is. Listed data for some other double-based powders has worked too.

Weatherby and WSM rounds are loaded to the highest SAAMI pressure level for rifle rounds, 65,000 psi--and no, there isn't any significant difference in SAAMI and CIP pressures. One of the major pressure labs in the U.S. did some experiments with the CIP transducer location, and the difference between it and the SAAMI placement was less than 1000 psi.

Am assuming that this thread had deviated far enough from any particular topic and not intending to add any more contention... but adjusted for barrel length Mike, it's the difference betwixt a test barrel and your barrel...you are there.

MD, have been dicking around with a 7WB throated to 140/150s and w/slightly reduced loads have been reaching right into the published Nosler loads.

Hard to believe it isn't more popular...

Anyway, did run out of RL22 but managed some MRP of late --have you run any 140/150 loads with yours & MRP?

Thanks, JB. I appreciate the insight. It is interesting to me that from what I've gathered, there is no SAAMI pressure spec on Weatherby rounds, and I also read that Weatherby loads their ammo to 71,000 psi- higher than I want to shoot in my rifles. It would explain a lot if that info is factual.

When I hear of 7mm WSM ammo firing a 160gr non-moly coated bullet at 3250 or 3300 fps, or a .270 Weatherby firing a 150 at 3250, I start to wonder just what kind of peak pressures those loads are hitting...

Jordan,

Not all Weatherby rounds have been SAAMI standardized, just the most popular. Here are the MAP (maximum average pressure) ratings, all PSI:

.257--62,500
.270--62,500
7mm--65,000
.300--65,000
.340--62,500

The .240, .30-378, .338-.378, .378, .416 and .460 haven't had piezo standards established yet, probably because other riufle manufacturers don't tend to chamber them.

The SAAMI pressure standards are also paired with velocity guidelines, though ammo manufacturers are given a 90 fps, plus or minus, window on velocities. The .257 Weatherby's with 100-grain bullets is 3580 fps, and the .270 Weatherby's with 150's is 3230.