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Old November 11, 1999, 02:48 PM   #1
Join Date: October 6, 1998
Location: My wife's house...
Posts: 2,659
I'm very familiar with the .308 USN conversion (chamber sleeve & mag-well spacer).

My current interest is for a "Tanker" carbine conversion to .35Whelen or .375Whelen (brush gun), and a standard rifle configuration to something around 6.5x72mm, while retaining full use of the semi-auto functions.

My initial concerns are gas pressures, porting, operating parts inertia (battering) etc.

Has anyone any experience with these sorts of conversions that they're willing to share?

Are there any online custom conversion sites or forums that address such issues?

Thanks in advance for any assistance.
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Old November 11, 1999, 07:26 PM   #2
Art Eatman
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Join Date: November 13, 1998
Location: Terlingua, TX; Thomasville, GA
Posts: 24,164
About the only bit of your post I can talk about is the gas pressure. If memory serves, the pressure at the port of the standard M1 is 2,000 psi, from the GI cartridge pressure of 47,000 psi. (If anybody knows differently , please correct me.)

Anyhow, if you load a hotter cartridge, the hole must be smaller. For your 6.5, you could probably safely assume that the ratio of the pressures should be as the ratio of the cross-sectional areas of the gas ports. More pressure = smaller hole.

For a tanker length, the pressure at the gas port in the shorter barrel will be higher than the gas port out at the end of the longer barrel. Same deal as above.

Hope this helps.

, Art
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Old November 11, 1999, 11:29 PM   #3
James K
Join Date: March 17, 1999
Posts: 24,193
Hi, Mykl,

The M1 is really made to work with one cartridge. Even the .308 conversions have had problems. The .35 Whelen is not too far out, but the 6.5x72(?) would be 9mm too long. (By the way, the only 6.5x72 I know of is a resized version of the old straight rimmed 7x72R. Maybe I missed something.)
Anyway, I think it would be an interesting and quite costly experiment. Remember the cartridge has strict length limits and has to work with the clip unless you modify the magazine as well.

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Old November 15, 1999, 10:37 PM   #4
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Join Date: September 1, 1999
Location: IL
Posts: 294
Jim Keenan:
You mentioned problems with the .308 Navy conversions. Could you elaborate on these problems? I've just purchased an IHC Garand converted by the Navy to .308 and I'm curious about what problems to expect. Thanks in advance.


[This message has been edited by PoiDog (edited November 15, 1999).]
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