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McWhorter Rifles 6.5 Wby Mag.!!

 
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  #8  
Old 07-08-2009, 07:38 AM
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Re: McWhorter Rifles 6.5 Wby Mag.!!

Quote:
Originally Posted by AZShooter View Post
That is screaming velocities for those bullets! I had a 270 Weatherby with a 26" barrel and it shot the 130 NBT at 3475 so I suppose this is within the realm of possiblities.

According to the way I understand cartridge efficiency, whenever you neck down a cartridge (like 270Wby to .264), the pressure has a less area to push on (base of bullet), which leads to a loss in efficiency. They are probably getting those velocities, but 3275fps in a 24" barrel is definitely a HOT load.

I looked in Quickload and in simulating the 6.5x300wby (not the 270wby), which has a LOT more powder capacity (98gr vs 82gr), 3275fps in a 24" barrel is still a HOT load (68k-70kpsi depending on powder).

I hope it works out and is a safe rifle.

AJ
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  #9  
Old 07-08-2009, 07:44 AM
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Re: McWhorter Rifles 6.5 Wby Mag.!!

I am shooting a 270wby. with a 24" barrel. 140 Bergers with 71grs of VitN560. I am getting 3275 out of them with no pressure signs at all. I do know that this is a hot load but no sticky bolts and I have shot 1.5" groups at 400. This is a 7lb rifle with a 12x scope.
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  #10  
Old 07-08-2009, 08:17 AM
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Re: McWhorter Rifles 6.5 Wby Mag.!!

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Originally Posted by jbroadnax View Post
I am shooting a 270wby. with a 24" barrel. 140 Bergers with 71grs of VitN560. I am getting 3275 out of them with no pressure signs at all. I do know that this is a hot load but no sticky bolts and I have shot 1.5" groups at 400. This is a 7lb rifle with a 12x scope.

I don't doubt it at all, Quickload shows that 3275fps in the 270wby and 140gr bergers will give a pressure of around 66k psi. Definitely a good solid and safe load in a strong rifle. The question would be when necking it down and loosing the efficiency, how high would the pressure be.

Lets look at an example of necking down a cartridge and comparing it's performance to it's parent with the same weight bullet and same pressure. Looking at the 308win and 7mm-08 velocities and pressures with the same weight bullet shows the loss in efficiencies. I looked at the 150gr numbers for both cartridges and the 7mm-08 looses about 5% velocity for the same pressure and weight bullet from it's parent the 308Win. Necking the .308 down to .284 is a reduction of 15% in bore area. Necking the 270 down to 264 is a reduction of around 14%, so the numbers should be relevant.

If the loss in velocity for the same weight bullet and same pressure is 5%, then the 264x270wby and a 140gr bullet should be around 3111fps (using your velocity in the 270wby). The 264Win Mag and the 140gr bullet shows a velocity of 3170fps when the pressure is 66k psi.

Just some numbers to ponder,
AJ
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Last edited by AJ Peacock; 07-08-2009 at 08:23 AM.
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  #11  
Old 07-08-2009, 10:32 AM
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Re: McWhorter Rifles 6.5 Wby Mag.!!

jboadnax,

Load the 264 Win Mag to the same pressures with the same bullet in same barrel length with the same powder he is using and you will get the exact same performance pure and simple. Velocoty is a simple function of pressure and time, pressure behind the bullet and time that pressure is applied to the barrel.

he is getting 3300 fps for one reason, he is using alot of pressure in a well built, tight chambered rifle.

Not knowing his throat design its hard to say if this level of pressure is smart or not but I would be really interested to know how many firings he is getting on each case at 3300 fps with 140 gr bullet weights.

My 6.5mm AX will get 3350-3400 fps with a 142 gr SMK very comfortably as will the STW but thats at comfortable chamber pressures and long brass life.

I do not know anyone that is opposed to paying alot for good brass. I know many who are opposed to paying alot for crap brass. I am not saying the Wby brass is not quality as far as specs but its SOFT, very soft and will not last long under high pressure loads.

This all reminds me of a guy that came out many years ago with his 257 Hot Tamale. Was spouting all over the web about driving a 100 gr XLC bullet to 4100 fps in a 28" barrel length. Well, this went on for years and years but eventually it caught up with him.

I had several conversations with this smith and he claimed he designed this new wildcat although it was identical to the 257 STW, in fact interchangable. I questioned him on his velocity claimes MANY MANY TIMES and even had customers contact me wanting this level of velocity. In the end, he simply pushed pressures to the extreme to get these velocities and after he got backed into a corner he finally admitted that he did not care about case life and that performance was the only thing he cared about. He said if someone wanted more then one firing per case they would have to live with less velocity.

Well, that less velocity, in a 28" barrel length turned out to be around 3800-3850 fps to get a min of 4 firings per case.

The 4100 fps claim is possible, but you will throw your brass away after the first firing and he simply used this velocity claim as a sales pitch and sadly it worked very well.

Do not get caught up thinking that your getting something for nothing. Again, with some minute variables, to get Z fps, you need X psi of pressure for Y bore time.

I have built several 264 Win Mags and loaded them up with powders such as RL-22 and H4831 and gotten velocity up to these levels easily, case life was not good but it can be done no doubt.

Take a strong receiver, tight chamber and push the pressure to it, no problem at all. Not saying he is not getting this level of performance but I am saying be cautious about it because he is only getting this performance because of very high pressures.

As far as the accuracy performance, that is nearly 100% the result of a well made rifle and a quality barrel, when you get into this case capacity of chamberings, very little has to do with inherent accuracy of the case design, its nearly all determined by the rifle quality more then anything else.

One other thing that I see as a red flag, I have shot the 140 gr Berger in pretty much every chambering in 6.5 you could think of from the 6.5mm BR up to my 6.5mm Allen Magnum and in all of the top barrels made in the US.

In EVERY case, once velocity reached around 3250 fps, accuracy went to hell. In some cases it went from sub 1/4 moa at 3200 fps to 2-3 moa at 3275 fps. Obviously there are not many 6.5mms that can drive this bullet weight over 3250 fps but the big ones can.

When I was developing my 6.5mm Allen Xpress and 6.5mm Allen Magnum, I started with the 140 gr Berger. With the AX, which is based on the 300 Dakota case, and the instant the muzzle velocity reached 3250 fps, accuracy went away. At 3300 fps 50% of the bullets never made it to the target, even in 1-9 twist barrels.

In the 6.5mm Allen Magnum, based on the 338 RUM parent case, 3300 fps is a puff load, 3400 fps is a puff load and at this level, I was seeing nearly 100% bullet failure in flight.

Switched to the 142 gr SMK and was able to put the throttle down on both to get up to proper working pressures to get the ultra slow ball powders to burn cleanly. In the 6.5mm AX, this resulted in around 3350-3375 fps with well under 1/2 moa accuracy.

In the big AM, where the Berger let loose at 3250 fps, the 142 gr SMK ran hard up to just shy of 3600 fps which is where I stopped increasing the powder charges in load testing. Dropping the velocity back down to 3550 fps gave decent brass life, which in my opinion is at least 4 firings per case.

I am just wondering what barrel he is using to get 3300 fps with the 142 gr Berger and getting this level of accuracy. I am also curious how many rounds down the bore these rifles have that are producing this level of accuracy with these bullets at this velocity. Again, in my experience, the older the barrel, the lower the velocity ceiling of the Berger bullets. Brand new barrels may well get you 3250 fps but a barrel with even 300 rounds down it will often drop that velocity ceiling noticably.

Again, I stand by my original comment, I see no difference in performance and accuracy between this round or a properly built and loaded 264 Win Mag other then spendier, less quality brass with the Wby...

I think you may have missed my comparision between the 7mm Rem Mag and 7mm Wby Mag, when handloaded to same pressures and when used in rifles with similiar throat lengths, with same weight bullets, the two are identical. Jsut because the factories down load the Rem Mag severely does not mean its handloaded form is not the full equal to the Wby Mag either in factory loadings or handloaded form.

This holds true for the 264 Win Mag and this new wildcat which is a 6.5mm-270 Wby Mag and nothing else.

Again, I am not picking a fight, just stating the obvious. Obviously they build very quality rifles but the chambering is nothing new, just a hot loaded 264 Win Mag in every way other then name.

I am also not saying that there is no need for this wildcat, hell, to each their own. If they want to design a new wildcat, more power to them, I have done it a couple dozen times and at times have been hammered for my test results but in the end every claim I have made has been supported many times over by customers.

I am sure this will happen with these rifles as well but the only reason for this velocity performance is pressure, pure and simple, no magic with special powders or anything else, just alot of pressure.

I am also not one to pick on high pressure loads as long as they are loaded in guns and brass designed for this level of pressure but there are realistic limits we as "experts" in the business have to hold out chamberings to to be safe for the general public that often get stary eyed and always want more.

To close with, I want to tell of a 7mm Rem Mag I still own that I used for many years. It was a Ruger M77 MkII with a 24" barrel. Decent shooter, sub moa but no better then 3/4 moa shooter. Still a good practical big game rifle. When I started handloading for it I had several years of experience handloading so did some playing with the round.

Started with the max load from the Nosler manual for a 140 gr BT. I believe it was 68 or 69 grains of Rl-22 which was supposed to be good for 3300 fps. Loaded that load up, shot it over the chrono, averaged 3075 fps!!!! How could this be, the Nosler manual states 3300 fps which was exactly what the 7mm WBY could do out of the same manual.

I took a fired, unsized case and rechambered it in my rifle(just a think from my 50 BMG load development). The case chambered flawlessly, telling me pressures were extremely mild. No resistance on chambering that case at all, felt like a virgin case. Increased the powder charge 1/2 grain at a time and shot all loads over a chrono. Finally, at 72.0 gr I hit 3300 fps and pressures appeared to be perfectly safe. No pressure signs of any kind and primer pockets were still very tight.

Again, proves the point that velocity is a simple function of pressure and time, not grains of powder in the case.

Being young and "Wanting More", I kept working up the load 1/2 grain at a time and got to 3420 fps. Thats with a 140 gr BT in a 24" barrel............

There was not a sign of pressure of any kind, no ejector slot mark on the case head, effortless bolt lift, effortless extraction, no primer pocket loosening at all........

Is 3420 fps with a 140 gr bullet in a 7mm Rem Mag out of a 24" barrel a smart load to use???? In my opinion, NO, I dropped it back to 3300 fps and left it there.

Stating my original point, this is simply a 264 Win Mag loaded to top end pressures and packaged in a good gun with a chambering with a different name on it, nothing more, nothing less.

I garantee he could build a 264 Win Mag to the same specs and get the exact same performance, I know that because I have done it many times.

Nuff ranting.
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  #12  
Old 07-08-2009, 11:31 AM
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Re: McWhorter Rifles 6.5 Wby Mag.!!

I'm sending bullets at 3,300 out of a 264 26" using 68 grains of RL25.

Using Win and Rem brass btw.
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  #13  
Old 07-08-2009, 11:54 AM
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Re: McWhorter Rifles 6.5 Wby Mag.!!

SU37,

Well, with the barrel length correctly, you right on with what this 6.5-270 Wby is getting, right on the nuts to be honest, exactly what I have been saying. Same thing in a different package.
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  #14  
Old 07-09-2009, 09:17 PM
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Re: McWhorter Rifles 6.5 Wby Mag.!!

I guess it's the pixie dust.

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