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

Facts were presented in this thread, but since those contradict preconceived notions, they "must" be wrong.

The engineers at SAAMI and the engineers at the component/ammo Co's obviously aren't all that bright...

Su 35 I have been out of town for a couple of days and want to bait you further.

Neither Bob nor I load our Mashburns so that the bullet extends below the neck. I filled a fired case from my #1 Mashburn with water Thursday night. It shows a case capacity to the bottom of the neck at 82.8 gr. So by your data I have 2.8 gr. +/- minus more case capacity than you.

Now in the real world 2.8 gr. is not much and probably results in maybe 25-30 fps. of velocity difference at a 65K max but it is still more case capacity. I get a chronoed. 3060 fps. from this 24" Mashburn with 74 gr. H1000 and Sierra 175's. I'm happy and intend to continue using this cartridge.

Flame on fellow!!!!!

Docbill, seems you have used both no? Years back i think it was you who did the case capacity comparison..which turns out the mashburn has 3 grains more than the wby?

Three [bleep] grains guys..thats what we are arguing about? As most know neither the mash or wby suffer from mag constraints. The MK5 is long, then theres the M700 like mine that are 3.6" right off the rack.

From reading here, the wby guys are the ones doing all the trick moves, but the wildcat shooters are keeping it simple..

This thread is a damn hoot.Grown men stomping there feet and holding their breath, insisting there toy is the best, incredible.

Tanner, yes..3rd season kicked my ass this year, shot this one the last day in dark azz pines, split second to decide, turned out to be a 3x4.

Docbill,

Thanks very much for that information. Now I can satisfy pathfinder76's request, and apply a basic internal ballistic formula to the 7mm Mashburn.

First, I found the water capacity of once-fired 7mm Remington Magnum (made by Federal), 7mm Weatherby (Weatherby factory, made by Norma) and 7mm STW brass (Remington). First I measured with the water level at the bottom of the necks, like Docbill did, when he found his Mashburn brass held 82.8 grains. Here are the results:

7mm STW--90.6 grains
7mm Rem--79.9 grains
7mm Wby--83.3 grains

It may seem strange that the 7mm Weatherby has slightly more powder room than the Mashburn, but that's with water to the bottom of the neck. I next measured the 7mm Weatherby capacity with a 175 Sierra GameKing seated to the SAAMI standard cartridge length, and got a water capacity of 80.7 grains. This is still very close to the Mashburn's, and is because the Norma/Weatherby brass is pretty light, weighing 20 grains less than the Federal 7mm Remington Magnum brass.

Then I applied the ballistic formula that any change in case capacity in the same caliber results in 1/4 that change in velocity, in loads of the same pressure. I came up with this formula years ago empirically, by crunching the numbers of published, pressure-tested data. The result of my empirical approach was confirmed a couple years later by the late Don Miller, the guy who created the rifling twist formula used in Bryan Litz�s book and ballistic program, and published an article about it in either Precision Shooter or Varmint Hunter, I forget which.

Many people aren�t aware of this ratio. Quite a few assume velocity is directly proportional to case capacity, or close to it. This can be easily disproved by comparing the .308 Winchester to the .300 RUM. The RUM has about 100 grains of powder space, and the .308 only about 50, but the .300 RUM does not get twice the velocity of the .308. Instead it gets about 25% more. (I�m not going to do the math for everybody.)

Following the 1/4 formula, we can figure that the 7mm Mashburn as described by Docbill will get 97.7% of the velocity of the 7mm STW. I used the 7mm STW because I had a fired case for measuring the powder room, and it has a SAAMI maximum pressure of 65,000 psi, as high as SAAMI standards are in any round.

If we look up the 7mm STW in various handloading data sources, we find the top velocity is usually around 3000 fps for 175-grain bullets. The Nosler manual lists 3042 fps from a 26� barrel, Hodgdon 3020 (24�), Hornady 3000 (26�), Norma 2989 (26�), and Alliant 3033 (24�). The highest with a 24� barrel like Docbill�s rifle is Alliant�s at 3033. Applying the formula we multiply 3033 x .977 and get 2963 fps.

This is about what the 7mm Mashburn should get at 65,000 psi or close to it. This isn�t surprising, since with bullets seated to the base of the neck the Mashburn only holds about three grains more powder than the 7mm Remington Magnum. Or at least it does with the cases Docbill and I measured. Changing the brand of brass would have an effect�in fact, using fire-formed Norma 7mm Weatherby Magnum brass would increase the capacity of the Mashburn somewhat, though the neck would be a little shorter than when using .300 Winchester brass, 2.55� versus 2.62�.

Pressure also varies depending on the bullet. The 175 Sierra Docbill uses will develop a little less pressure than many other 175�s because of the shorter bearing surface of boattail bullets, but his velocity of 3060 fps indicates the pressure probably is a little more than 65,000.

Using the old Homer Powley formula (again proven many times) that pressure increases twice as fast a velocity indicates a pressure of 69,000+ psi. This also isn�t surprising, since around 70,000 psi is about where most pressures end up when using �traditional� pressure signs such as bolt lift, primer pocket tightness, etc.

This isn�t exactly dangerous, obviously, but manufacturers of ammo and rifles prefer a little more safety margin, just in case a rifle is fired in very hot weather, or there�s dust or water in the bore, both of which can raise pressures. Handloaders using a wildcat that�s supposed to get more zip aren�t usually as concerned.

Thanks John for all the work. Just as a thought exercise, do you think the old Rem factory listing of 3050 fps. (if my memory is correct) for the 7 Rem. 175 load was over 65 K psi. or did they use majik powder to get those #'s. They have obviously turned the power down on that load now for several widely known reasons.

I use .300 Win Match Federal brass. I don't know if other brands are thicker or not. I develop all my loads in the Texas summer and usually the temps. are over 90 and at times over 100 so if it works in our temps then it should not be an issue. I also chose H1000 for its hopefully temp. stabality. In my other rifle I use RL-25 and also developed that load in the summer using Hornady 162's. I backed that load down to 3225 using 75 gr. The AOL on that load is a little longer than the other Mashburn.

Docbill,

Just for conversation's sake, QL estimates that 162 load of 75gr RL25 at 3226 fps and 75,833 psi peak pressure.

Docbill,

The original 7mm Remington Magnum factory loads were tested in 26" barrels--as were most cartridges in those days. They used what was later sold as IMR7828, but the testing as also done with copper crushers. When the industry later started the switch to piezo-electronic testing, it was found the pressures were very high--and the 7mm Remington Magnum's pressures also tended to vary more than many others rounds. Thus the eventual drop in factory ballistics.

The argument I have with the Mashburn guys is when they get all pissy that my 24" 3 groove .280AI is supposedly "greatly" over pressure because I get 3200 fps out of a 140 TTSX. Their basis is that the Barnes book shows that speed for a 26". Never mind that calls to Nosler and Barnes say its a perfectly safe load and gets its speed due to the 3 groove and less bearing on bullet thus less pressure/resistance.

I'm supposedly guessing yet the Mash burn loaders doing the same thing are relying on ancient pressure data.


Intellesting....

Docbill, thank you for providing your data, excellent.


I went into town today and found two boxes of Hornaday 7mm 175 grain bullets. RN and SP.

I then measured the bearing surface of all three bullets. Here is what I came up with. Probably not exact but very close.

Horn 175 SP was .730
Horn 175 RN was .800
Nosler 175 LRAB was .650 much less,

Then loaded them to exact Hornaday book data. Using Rem brass and Rem Mag primer. Hornaday uses a 26" barrel, mine is 24".

I also loaded some 175 LRAB to that data as well.
Here are my results and conclusion.

Hornaday 7mm 175 SP I loaded Hornadays recommended max load of RL25 75.9 grains
Velocity was 3,044 for average.

Hornaday 7mm 175 RN (same load)
Velocity was 2,989 for average.

Nosler 175mm LRAB (same load)
3,167 for average

My conclusion, I had it backwards. Less bearing surface resulted in higher speeds. This is I would think a good thing for shooting the high BC LRAB and higher speeds.

2" of more barrel and I would be right in line with Hornaday results shooting the Horn 175 SP at 3,100 fps.

Absolutely no signs of any pressure with the loads.




Here was my LRAB load. Am I out there pressure wise?
Unless someone shows me I am wrong...
I don't think so, seeing that the LRAB has less bearing surface.





I'll test the H4831 load next week.

And something the Mashburnites just hate to hear. Their cartridge doesn't really have all that pressure breathing space as they thought it had.

I would bet the Nosler 175 Partition at 3,050 is getting over 70K psi.

Thanks Mule Deer, the original Myth buster.

To bad Page and Hagel didn't have Mule Deer around.

If this was a court of law and the evidence presented today.
Bob would have his lawyer butt handed to him.

Page and Hagel didn't have the benefit of what our friend MD has available to him. They were men of their time and undoubtedly did the best they could.

But I'm biased that ole' JB might be the best gun writer to ever pick up a pen. Talk about a flexible and original thinker... I appreciate his input on this forum, and is frankly one of the few reasons I still hang around.

But arguing over Ballistic Gack is one of the most trivial things in life possible, certainly...

Are we gloating a little?

No doubt, but then Mashburnites were/are relying on that time period.

Not taking anything away from the Mashburn, still a great cartridge.



I really didn't appreciate the way Bob portrayed me.

JB, rates VERY highly with me, as well, and I started reading gun "lit", hidden in my text books at age 12, in 1958, when I started shooting. I have read all of the well known ones and many others whom were/are not as famous, although VERY talented....the late Ernie Stewart, of "BC Outdoors" was one such and "Bert" Stent, of central BC, active in my youth and before, was another.

I don't really see ANY writer, per se, as THE best, greatest and tend to evaluate specific articles, more than the individual(s), who wrote them. I agree with Brad, that Page and Hagel, I just, finally, purchased the last of his books for my enjoyment, were men of a time when the kinds of technological gizmos that we now have to measure various ballistic phenomena, were just not available.

I have simply enormous respect for Bob Hagel, always have had and he always impressed me with his honesty, knowledge and a certain humility that comes across in his written work. However, we live in a different world, in many important respects and should benefit from "progress" as much as we can.

All of this, notwithstanding, I will very simply reiterate my previous comments about "BobinNH" and will flatly state that he is one of the half dozen guys whom I have "met" on the gun-related internet, that I wish could accompany me on a hunt in northern BC....but, our laws exclude that possibility and my age ain't helping much, either!

So, what I get from all of this, is that, I really wish I could get a Simillion-built 7MSM, on a Dakota 76, for first choice, and see what it would do on "clearcut" Elk and Moose, here in BC, wearing a Swaro Z3 in 3x10x42, flinging 175s at, hopedully, 3000?

This, and I ain't even remotely a "wildcat" sort of guy!

Then, I wouldn't MIND one of those neat "UL" Weatherby's in 7mm Bee, either........

I'm not a fan of Weathebys but I sure think I could own one of those UL's!

Now, with a simple query and hoping for a peaceful reply(s).

IF, I had two identical actions, long enough in the mag boxes, identical barrels of 24" and both chambered in the optimal manner to obtain the best performances from each, one in 7mmBee and the other in 7mmMSM....

Which, freebore or not, loaded with 160 and 175 Nosler Pts, ONLY, would give the highest, SAFE velocities?

JB?

Others?

Almost as if someone at Nosler knew what they were doing when creating the LRAB...

Thanks JB, SU35 and Doc for the info and testing.

Mike

Thanks for the good words, guys. I must mention that both Hagel and Page were both large and positive influences on my eventual career.

What it looks like to me is the Weatherby and Mashburn are so close in case capacity that the only very small differences between them are the freebore of the Weatherby and brass price/availability. And after all the gack, probably the most practical of all the 7mm magnums is the Remington!

I have fooled with more than a couple 7mm Weatherby's and had to lean on things pretty hard to get to 3100fps with 160's. This was from 24" barreled rigs. And I have tried every powder under the sun pretty much.
I also found the Weatherby to be a little bitchy and honestly if I were going to fool with a fast 7mm again it would be a Mashburn, 7mm WSM, long throated 7mm rem mag, or perhaps a 7mm-338 remington ultra mag

Sound advice that I might have used had I not came to my senses and went to .30 cals.....