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4000 fps in a 7mm STW w/140 Bullet?

 
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  #43  
Old 03-10-2013, 07:13 PM
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Re: 4000 fps in a 7mm STW w/140 Bullet?

Quote:
Originally Posted by Bart B View Post
The highest max average pressure for a 7mm cartridge is probably the Weatherby Magnum version at 65,000 psi using SAAMI transducer measuring systems.

If that 'smith was near me, I'd consider betting him a bushel basket full of hundred dollar bills that his 7 STW would not push a 140 out over 3600 fps average from a 26" barrel with a max average pressure at 65,000 psi.

I had a 'smith back in the '60's tell me his .264 Win Mag would push out 140's at 3500 fps at normal safe pressures. After I offered a similar bet with him, he refused saying he didn't want to take my money.

I'd stay far away from that guy.
The 7 roy and 7rum both "top out" at 65 KPSI.

I had a strain guage on my sendero 7stw (26" bbl.); I'll try to dig up a few of the graphs and post them. They were a bit of an eye opener; easy to extract stuff was sometimes putting up over 70KPSI peaks. I never got balsy enough to push it 'till she got sticky though.
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  #44  
Old 03-10-2013, 07:22 PM
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Re: 4000 fps in a 7mm STW w/140 Bullet?

Coo coo! Coo coo!
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  #45  
Old 03-10-2013, 10:29 PM
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Re: 4000 fps in a 7mm STW w/140 Bullet?

That would be very interesting as well as Cool!

Rupe
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  #46  
Old 03-11-2013, 07:06 AM
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Re: 4000 fps in a 7mm STW w/140 Bullet?

It took a bit of digging but I found 5 of them; I'll try to post 'em. They were from '04 so they've been tossed about a bit
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  #47  
Old 03-11-2013, 07:25 AM
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Re: 4000 fps in a 7mm STW w/140 Bullet?

4000 fps in a 7mm STW w/140 Bullet?-065.jpg

4000 fps in a 7mm STW w/140 Bullet?-068.jpg

4000 fps in a 7mm STW w/140 Bullet?-067.jpg

4000 fps in a 7mm STW w/140 Bullet?-066.jpg

These are the four most pertinent ones-- the other one had little labeling and was likely just shot to confirm. Remember, I had no reference ammo, so it was basically just a comparison between loads. The two that say winchester are the 150 grain win factory load that was availability for a time. Notice it actually has the highest peak pressure.

RL 25 and 7828 were putting up within 25 fps of each other.

the first ans last trace were rl25, btw...

notice the small secondary peak just after 1 millisecond; it is a mild tight spot in the barrel that was noticeable with a patch or brush.

Last edited by Lefty7mmstw; 03-11-2013 at 09:09 AM.
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  #48  
Old 03-11-2013, 11:53 AM
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Re: 4000 fps in a 7mm STW w/140 Bullet?

Thank you! That is very interesting! I am surprised that the same loads can be so different in pressures. It does make you think. Thanks for posting them!

Rupe
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  #49  
Old 03-11-2013, 12:27 PM
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Re: 4000 fps in a 7mm STW w/140 Bullet?

I was shooting the 140 grain sierra pro-hunter for all of the hand-loaded data; I just noticed that wasn't listed.
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