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

A few years back I started a thread "7mm Mashburn vs 7mm Wby?" https://www.24hourcampfire.com/ubbthreads/ubbthreads.php/t Don't know what happened here..most of my post got deleted. ??? Anyways, Here are the results shooting the 175 LRAB and 70.0 grains of H4831. 3,080 average speed ES of 8 fps. .5 group [IMG]http://img.photobucket.com/albums/v705/su35/7mm%20WBY%20Mag/P1020702_zpsa892b5b6.jpg[/IMG]

Very nice!

My 7mm Weatherby Mark V ULW has a 26" barrel and gets just about the advertised 3200 with 160 Nosler Partition factory loads, 3-shot groups averaging .6-.7 at 100 yards. Don't think I'll be Mashburning anytime soon either.

I still don't savy how the Weatherby gets all that velocity without pressure and freebore.

Given equal barrels and pressure the Mashburn will outrun the 7mm Weatherby with 175 and heavier bullets....has to; it has more capacity.

I won't be going 7mm Weatherby anytime soon.Hagel proved it decades ago....the Weatherby is second fiddle.

It isn't unusual to see cases of slightly less capacity than another show roughly the same velocities with lighter bullets;usually the differences will be seen with the heavier bullets and this is where the larger capacity cases come into their own.

So I am not surprised to see SU35 get 3300 from a 7mm Weatherby; but I have also chronographed loads in the Mashburn that did 3300 fps with a 160 gr with no ill effects, even though I do not choose to run it that hard.3300 with a 150 seems pretty routine coming from those who have used them in the Mashburn.I haven't.


Besides, if I put a 7 Rem Mag on the bench next to a 7mm Weatherby and just compare the size of the cases, I am hard pressed to understand where all the additional velocity comes from...the body of a 7 Rem Mag case is actually larger,while the 7mm Weatherby has a longer neck; the case is 2.55 inches in length.

A 300 Win Mag case(from which the Mashburn is formed)has more capacity than either of the other two.

My '81 vintage Wby Mk V does 3050 with the Nosler 175 Partition and IMR 7828. I can't wait to try it with the LR Accubonds.

Bob,

The freebore flattens the pressure curve, which doesn't peak as steeply as in a conventional throat with the bullet seated close to the lands. Peak pressure is less, but the "area under the pressure curve" is greater, allowing the use of more slow-burning powder. This has been proven over and over again by pressure-testing. In fact if bullets are seated deeper in a conventional throat the same thing occurs.

The downsides? Accuracy can be mediocre unless the long throat is just slightly over bullet diameter. Otherwise the bullet can tilt slightly before entering the rifling. Throat erosion can widen the freebore enough to do this, though it takes a while, since throat has to not merely surface-crack (the early stage of erosion) but start to lose chunks of steel as cracked areas break off.

The Weatherby rifles I've shot over the past several years have all shot quite well, indicating the freebore is the correct diameter.

One thing I remember about shooting my 7mm Wby. handloads over an Oehler was the very low, sometimes single digit, extreme spread I'd see for five shot strings. This could be a nice thing for real long range shooting.

Yes, and very noticeable to me today.

The Hornaday manual list many loads that will reach 3,100 with the 175's and 3,300 with the 150s. I use those same loads to get the same speeds.

The only thing I see the Mashburn getting is more recoil.

Just got two boxes of 175 LRAB to test out in my 7wby..Like SU35's its a R700 and 24". Its been a great shooter, and does seem to produce velocities out of proportion for its case size..even with 180's.

John I have not done so in awhile but have had several 7 Rem Mags with throats cut for 160 gr bullets seated even with the base of the neck....this created some free bore no doubt and in those rifles I noticed that I did not hit that velocity/pressure "wall" as fast with the 7 RM that we sometimes see....and the cartridge was much better behaved.I also noticed those rifles gave high velocities with 140 gr bullets as well.

Actually I had one that took 70 gr H4831 and 160 NPT, which is nudging right there with the 7mm Weatherby max load from the Nosler manual.....

I wonder if the long throating had the same effect as the free bore of the Weatherby?

In any event I saw much the same effects from the 300 Win Mag doing the same sort of thing and one barrel, a Krieger SS 24" routinely did 3210 with the 180 gr bullet....I shot it for years that way.

In any event my only objective in going with the Mashburn was that I wanted 3200 fps or so from a 160 and over 3050 or so from a 175 from a 24" barrel...."easily". Figure I could not go wrong picking the bigger case,which proved to be exactly what I got.

Double radii.





I'm hurt.

SU35, have you determined the actual BC on the bullet yet?

laffin'

Of course...they are both good! Take either in a heartbeat over a 280AI.

Bob,

Aside from factory brass and ammo, the only practical difference between the Weatherby and the Mashburn is the Weatherby rounds will fit in a so-called .30-06-length magazine box of 3.3" or so. Which makes it possible to build them on standard 98 Mauser actions, which was a big deal when Roy Weatherby started out, and still was for a few decades afterward, due to so many cheap 98 actions being available. It's also why Winchester's series of belted magnums (.264, .300, .338 and .458) have an overall cartridge length of 3.34".

There are some, of course, who suggest that if the magazine box is longer you might as well do a 7mm STW, or even a 7mm RUM, rather than a Mashburn.

John: Well, I couldn't tell all this from a distance.

Never owned a 7mm Weatherby and didn't want one because brass is expensive,and I just came off a bad experience with 7mm Dakota brass(Norma).

Yes I could get Remington brass but didn't want that either.Besides I just did not trust the cartridge to give the velocities I wanted from a 24" barrel. Weatherby ammo is known for being fire-walled.In any event every source I went to shows the Mashburn as having greater capacity.

Minor point maybe but I would have been disappointed if the thing ended up being a warmed over 7 Rem mag with more expensive brass. I don't have the time nor the resources to try everything out there....

Didn't want an STW(BTDT) and it likes 26" barrels and doesn't give any more velocity than a Mashburn.

As to the action length business,just like a 300 Win Mag, the Mashburn will fit in a 30/06-length box.You just have to seat deeper. I set mine up for H&H length because I wanted to....not because I had to.

Page's rifle (that gave 3050 with the old 175 gr NPT)was a 30/06 length action...as was Hagel's FN Mauser before he started seating to longer OAL.

In the end I have been very happy with the cartridge and am not bothered by the wildcat thing,nor the results. It works perfectly. I am thinking of getting another.

I could be wrong, here, often am, but, the comment by "Reloader28" concerning the "Powell-Miller-Venturi-Radius" shoulder, as used in Weatherby's cartridges, makes me wonder?

I have long been under the impression that this was actually more a marketing ploy by Roy W. and the configuration really has little effect on the chamber then exterior ballistics of a given round?

As, I understand the situation, a larger case capacity, all other factors being equal, will give higher velocities, due to more powder burning which produces more of the pressured gases that propel bullets. So, I see little difference between a 30* standard, as in, .264WM case,( for example only, not specific to actual cartridge) and the "double radius" of a .270WEA. case?

My 26" factory P-64 Westerner bbl, will run the 125NP at an easy 3350-3375, all day and put these into sub-moa clusters, and I cannot "get" how the minor difference in shoulder shape would improve this?

Hmmmm, Bob, is ...thinking of getting another....

THIS, is an example of EXTREME "gunaholism" and my 50ish years of this insanity has shown me that it is an incurable affliction!

Probably, should sell ME that old beater of a Simillion you now have, eh..........

Kutenay,

I don't consider Roy Weatherby to be on the same level of genius as John Moses Browning. However, when it came to creating high velocity cartridges he chose double radius shoulders & freebore for a reason.

I do know that in drag racing applications, rounded (radiused) intake ports induce greater velocity in flow rate vs. turbulence in right angles.

kuteany: I'm like you.....when I like something, I get a spare.

In one of JOC's monthly columns in Outdoor Life in the early 60s, he covered the 300 Wby and his two rifle so chambered. In that article, he stated that Roy Weatherby had told him that used the double radius as a marketing ploy, not because he thought it contributed to performance.

At that time, I was a high school student and "Outdoor Life" was THE reading material I favoured over any other, especially the boring and useless textbooks we were forced to study.

I thought when I posted the above that I had read "J'0C" on this at that time and vaguely recalled what Rick has posted.

I dunno, but, I tend to doubt that the shoulders REALLY DO make any major difference in performance in this situation. I do recall MD's comments on "the rocket effect" from an article he published some years ago and my impression from shooting various rifles is that his conclusions were/are correct in this respect, but, I am a bit unclear as to the effects upon velocity?