Home Forums Hunting & Shooting Long Range Hunting 7mm Wby and LRAB results...........

The people I have spoken with off-line about this thread,and who have experience with the 7mm Weatherby,say the velocity claims for the 175 load made here are malarkey.

The SAAMI table indicates that as well....even if a 3/8" freebore allows a bit more speed, it isn't enough to jump velocties up to the levels of an STW or RUM.

So let me get this straight...

You don't rely on a manual for pressure data and you don't rely on a chronograph to extrapolate pressure from velocity, even though pressure = velocity, and the velocities in the manuals come from pressure tested data.

You have your own pressure testing gear?

If not, what you're saying is you guess.

Which, of course, is why most wildcat rounds "out-perform" conventional rounds so dramatically...

So let me get this straight...

You don't rely on a manual for pressure data and you don't rely on a chronograph to extrapolate pressure from velocity, even though pressure = velocity, and the velocities in the manuals come from pressure tested data.

You have your own pressure testing gear?

If not, what you're saying is you guess.

Which, of course, is why most wildcat rounds "out-perform" conventional rounds so dramatically...

I see this thread has wandered even further into the theoretical since last evening.

Yes, you can extrapolate pretty closely on pressures if you know what you're doing, and a chronograph is the #1 way to do it. I've done it a bunch of times, and been able to test my loads with either strain-gauge equipment, or have a piezo-electronic laboratory test them.

I see Bob still insisting the 7mm Weatherby Magnum gets it's results with too-high pressures, despite all the pressure-tested data to the contrary. I just happened to do an article on the 7mm Weatherby recently, and have the Nosler and Norma maximum-velocity 160-grain handloads for it and some other 7mm magnums at hand:

7mm Wby. Magnum Norma 26 inches 3199
7mm Wby. Magnum Nosler 24 inches 3197

7mm Rem. Magnum Norma 26 inches 3084
7mm Rem. Magnum Nosler 24 inches 3077

7mm STW Norma 26 inches 3176
7mm STW Nosler 26 inches 3229

7mm RUM Norma 26 inches 3186
7mm RUM Nosler 26 inches 3261

Somebody will no doubt point out that Norma is a European company, and the SAAMI equivalent over there is the Commission Internationale Permanente (C.I.P.), which uses a slightly different piezo-electronic set-up to measure pressures. But Norma is also a member of SAAMI, so adheres to their guidelines.

Also, Western Powders runs one of the larger pressure labs in the country, which does a lot of testing for other companies as well. They've done some experimenting with C.I.P. piezo barrels to see what the actual difference was, rather than speculate about it, and found there was around 1000 psi difference.

The reason most companies don't publish pressure data (though Western also does, for Accurate and Ramshot powders) is that reloaders are very much likely to extrapolate what they can do, and possibly get into trouble. For one thing, the pressures listed by Hodgdon and Western are Maximum Average Pressures (MAP). There are a couple of other pressure standards that cartridges have to meet, one being how much pressure varies from average on the HIGH side, since individual rounds can vary considerably. This also affects the MAP either SAAMI or C.I.P. select for a certain round.

Also, you can be assured that any load found in any current source of SAAMI-member data does not exceed the MAP of that cartridge, so that limit in pressure is implicit in any data.

So let me get this straight...

You don't rely on a manual for pressure data and you don't rely on a chronograph to extrapolate pressure from velocity, even though pressure = velocity, and the velocities in the manuals come from pressure tested data.

You have your own pressure testing gear?

If not, what you're saying is you guess.

Which, of course, is why most wildcat rounds "out-perform" conventional rounds so dramatically...

You must have missed the part of my recent post where I've done a lot of testing of "guessing" pressure with a chronograph by comparing the results to SAAMI loading data. Yes, you can come very close to estimating pressures with chronograph results. I've done it dozens of times.

In fact when the .300 WSM was so new there wasn't any SAAMI reloading data, a magazine assigned me to work up some loads, in order to beat the competition with the first .300 loading data around.

I compared the powder capacity of the .300 WSM with the .300 Winchester Magnum, using water and a bullet seated to the same depth in fired cases. Using a simple internall ballistics formula, I figured the .300 WSM should get 98% of the velocity of the .300 Winchester Magnum, so worked up some loads with popular .300 Winchester Magnum powders using that guideline.

My loads were published in HANDLOADER magazine, and when pressure-tested data came out over the neat year, only two of my 10 or so loads varied an entire grain from the pressure-tested data--and one of those was a grain under. The others we either spot-on or within a half-grain. And that's just ONE example among many of using a chronograph to estimate pressures.

As another experiment, I once loaded for the .270 using all the the traditional pressure signs, including measuring case-head diameter, to what were apparently "safe" levels. I then took of the same ammo to a piezo lab, where it tested almost 68, 000 psi.

Now, I did ignore velocity as an indicator in that test--and it turned out that the velocity I was getting was faster than any published data, and the powder charge also higher than any listed for that bullet weight.

Yes, there are ways of guessing pressures that are more accurate than bolt-lift and primer pocket tightness.

Jordan, I get all that and agree.

Still, saying that a /thoughtful/careful/eyes-wide-open handloader who will not push an agenda, can't get a sense of safe pressure via pressure tested data and an average velocity across his chronograph (adding or subtracting velocity for barrel length differences), while keeping an eye on brass life and "traditional pressure signs" is, well, dumb beyond belief.

Umm Brad. That is what I do. EVERY single time and I apply that knowledge and technique to the Mashburn. But you know no more what actual pressure you are running in the 30-06 than I do in the MSM (I know I don't). We assume safe pressure based on those indicators above.

I posted this thread in April 2010 asking about the comparison of both the Mash and the Wby.

http://www.24hourcampfire.com/ubbthreads/ubbthreads.php/topics/3983494/1


I bought a 7mm Wby to find out FOR MYSELF what could be done with published data. I wanted to test it out and know for myself. I figured if the data didn't match up I could punch my rifle out to Mashburn.

So far, with published data, I am getting the speeds and to prove for myself and others here I'll be buying some Hornaday 175 grain bullets to test out. And, measure their bearing surface.

I'll be glad to ship those bullets/componets and rifle to BobNH and let him test it out. My cost. Otherwise Bob, shut your belligerent, arrogant, angry, mouth up!

Put up or shut up!

You're having a hard time with reading comprehension I believe... I never, ever said "know" pressure... I said "extrapolate" pressure.

You're fixated on something I NEVER said...

So you bought a Wby to see for yourself. Don't own a Mashburn and never have and are mad because guys that have owned and loaded for both don't agree with you? Wow. That's interesting.

either pressures aren't equal or you're having to play "56 trick moves" to get it. Which is exactly what it seems like Bob has been saying in this thread.