7MM Rem Mag in 21 Inch barrel


March 17, 2005, 11:53 AM
Okay, I bought recently a very nice Western Field 660 in 7mm Rem Mag. This is a Mossberg 810 that uses 4 locking lugs, two opposite, and was produced in the 1960's and 70's. I bought it because for the price, a rifle with deep bluing, fully polished metal, open sights, and a Walnut stock cannot be had at anywhere near the price I paid. It was in perfect condition save for some finish loss on the stock. Barrel was 24 inches long.

Okay, I cleaned the barrel and revealed perfect rifling and a mirror bore. From the breach end, all looked so good that I almost kissed myself. I then made the mistake (or good move) of looking at it from the crown. To my woe and sorrow, I discovered a bulge or barrel ring some 2 1/2 inches from the end. Closing my eyes, I confirmed its location with the very slightest bulge on the outside of the barrel. Well, crap.

So, I take it to my smith and he is going to cut the barrel down just behind the bulge and re-crown it. His work is highly recommended all about my area so I feel good about its work. Now, I understand accuracy should go up slightly because of the more rigid barrel, now that length has been removed (theoretically, of course, and I know it depends on a good crown job, but just for grins and chuckles). What velocities and energies should I expect from a 7mm Remington Mag out of a 21 inch barrel?

I can't afford $200 or more for a replacement barrel, but $25 to cut down and recrown is affordable so that is the route I chose. Now that I have the tiger by the tail, I just wonder what I should expect.


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March 17, 2005, 04:45 PM
pretty significant velocity loss. i don't have my factual numbers here when i went from 26" to 24", but i do remember i thought it was a bad idea.

when you get the funds up, if that barrel is a shooter, i'd check into having it re-chambered to something more suitable to that barrel length, like 7-08.

March 17, 2005, 04:52 PM
He can't rechamber 7 Rem Mag to 7-08 without even more barrel loss because the 7-08 case dimensions are smaller and shorter than the 7 Mag. Such a rechamber job would require setting back the barrel significantly (maybe 2 inches) and this in turn could mess up the barrel inletting depending on taper dimensions of the barrel.

Even rebarreling may be messy unless he could order a new barrel with matching diameter and taper. I agree he will lose substantial velocity with 21 in barrel though.

Good shooting and be safe.

ps: Can you return the gun for a full refund?

March 17, 2005, 05:52 PM
It would have involved shipping. Turns out it was cut back to 21 1/2 inches, down from 24 inches (2 1/2 inches cut). Already I have a 270, 30-06, .308, and .243, not to mention 7.62x54R and .30-30, so the world is not lost. I imagine it will perform in the .270 range.


Buck Turgeson
March 17, 2005, 07:48 PM
Like Mark Twain said about the 'Allen's Pepperbox' ... if she don't bring home what you're aiming at it will fetch home something else. Besides, you can probably read at night from the muzzle-flash.


March 17, 2005, 08:50 PM
Eh - load it with slightly faster powders and be done with it. It'll still likely give you performance equal to a 280 at a minimum, and that's plenty good in my book...

Art Eatman
March 17, 2005, 10:24 PM
HearGuards. I strongly recommend HearGuards. :D

Muzzle velocity? I'd guess 300 to 400 ft/sec below most published data...


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