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Author Topic: 7 mm Rem Mag  (Read 751 times)

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Offline h4064

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7 mm Rem Mag
« on: December 19, 2007, 02:28:07 AM »
If I had a 7mm 150 BT traveling at 3000 fps out of a 24" barrel.
How much steam would the same load loose (fps) if the barrel was 13"?
What is the formula for figuring out fps per inch of barrel?
Thx Mike
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Offline Glanceblamm

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Re: 7 mm Rem Mag
« Reply #1 on: December 19, 2007, 04:01:19 AM »
h4064
Welcome To Graybeard Outdoors!

My guess would be 2,450fps out of the 13" barrel based on the old 50fps per inch adage. I do not own a chrony so you will probably recieve a better answer than mine.
P.S. 13" rifle barrel ? is this legal ? I thought 16" was the min but realize yours may be hypothetical.
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Offline h4064

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Re: 7 mm Rem Mag
« Reply #2 on: December 19, 2007, 07:07:40 AM »
I am building a long range encore barrel with a muzzle brake.
Thanks so much for your info and time
Mike ;D
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Offline h4064

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Re: 7 mm Rem Mag
« Reply #3 on: December 19, 2007, 07:09:15 AM »
oopppps pushed the wrong button... encore pistol barrel. thx again
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Offline jhalcott

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Re: 7 mm Rem Mag
« Reply #4 on: December 19, 2007, 07:53:44 AM »
 H4064, why are you making the barrel 13"? I believe a barrel with THAT much powder would need at least a 16 to 18 inch barrel to be worth it. A smaller case like the 284 or even the 7x57 or 708 will get you to the same velocity with a LOT less powder. A 7x30 only looses about 100 fps when you go from a 24" barrel to a 14" one. You will not get that close when using the 7Mag. The fireball willl be large.
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Offline Rog

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Re: 7 mm Rem Mag
« Reply #5 on: December 19, 2007, 10:34:44 AM »
I once had a 7mm Rem mag 15" bbl.

I did very limited load development and chrono'd very few loads.

I was able to push Speer 145 gr BTHP bullets at just under 2700 fps.  My chrono went on the blink before I could clock the Hornady 139 SST bullet.  I was sure hoping that one was 2750-2800 fps, but never got to confirm.

One thing I have learned regarding ballistic data, is that unless you actually chrono your load, you really don't know how fast it's going.

Manuals sometimes are a ways off due to differences in barrels, etc. (pressure barrels vs. productio barrels, tight, minimum chambers vs. standard chambers, etc.)

I was never really happy with my 15" 7 Mag barrel.

I now have a 280 AI, which I like a whole lot.

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Offline Mikey

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Re: 7 mm Rem Mag
« Reply #6 on: December 20, 2007, 01:00:12 AM »
Mike - welcome aboard.  That's a pretty short barrel for the 7mm Mag you have in mind.  I have always been of the impression that most magnum rifle calibers perform best in longer barrels and might recommend another caliber - like the 7mm-08 if you prefer the 7mm bore.  Actually, I wouldn't want to be holding onto the pistol grip of a 7mm mag Encore and I don't think I have sunglasses dark enough to shade my eyes from the nuclear fireball that would envelop the first 50 yds of the range, but that's just me and I'm a woozy in that regard. 

You may wish to consider a shorter cased caliber for your project.  JMTCW.  Mikey.
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Offline SuperstitionCoues

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Re: 7 mm Rem Mag
« Reply #7 on: December 20, 2007, 02:14:49 AM »
Mikey's right - consider a shorter case for the burn rate of the powder(s) you are selecting.  If you have to do it in a 7mm Rem. Mag, consider short-fat as an alternative - i.e. 7mm WSM, SAUM, WSSM, RCM, etc., etc.   or I would even consider a 7mm-08.  It might help offset the short run/burn chamber of the barrel. 

Interesting concept though.  Reminds me of the bolt-action pistol that Remington made for quite a while.  Anyone remember what those were chambered in?  Let us know how it turns out.
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Offline h4064

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Re: 7 mm Rem Mag
« Reply #8 on: December 20, 2007, 08:04:05 AM »
WOW thx to everyone who took the time to help me out.. It is clear that there are alot of people out there a whole lot smarter than me about this pistol thing. I still think I will stay with the 7mm because of the B.C.. But wow a nuclear fireball at dusk would be really cool hehehehehe.  I fell in love with hand gun hunting about 4 yrs ago. What a hoot.thx again to all.     Mike
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Offline jhalcott

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Re: 7 mm Rem Mag
« Reply #9 on: December 21, 2007, 02:39:28 PM »
  hey mike, there is a 7mm mag barrel for sale on another site.
http://specialtypistols.infopop.cc/eve/forums/a/tpc/f/7946077864/m/8891068215
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Offline Mikey

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Re: 7 mm Rem Mag
« Reply #10 on: December 21, 2007, 03:24:04 PM »
SupersticionCoues:  I think that was the Remington Fireball (???) 221 cal (???), maybe.
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