45-70 to 458 Win Mag conversion

[marlin mike]

Has anybody rechambered a Handi in 45-70 to 458 Win. Mag? I really like my Handi and I really want a 458. Don't know why I just do. Any ideas if this is possible and what would be involved?

[Mac11700]

Not as far as I have heard..and IMHO...you would be must better off buying a Ruger #1 in this caliber...It might last a little longer...cause I don't think the Handi would take to many shots thru it before stretching the frame...FWIW...Try some of the max Handi level  loads in 45-70...I think you'll find it plenty enough for this little rifle...

Mac

[eskimo36]

There is a good reason no belted mags are chambered in the handi.

[mattparliament]

FWIW, the 450 Marlin is belted.

[eskimo36]

You are correct and I should have been clearer in my response.

43K in pressure for the 450 marlin and 53K for the 458 win mag or a 23% increase between the two.  Full power loads in the 45-70 and 500 S&W are brisk to say the least in the recoil department.  They are both a handful in this light weight platform.

FYI
54K for the 338 win mag (25% increase)
60K+ for the weatherby mags(40+% increase)

[quickdtoo]

This is my 3rd attempt at posting a reply to this thread, had one going last night and forgot to copy it before submitting it, it's somewhere in cyberspace now. I just tried again a bit ago, copied it, the decided to add a link, when I copied the link, I overwrote the post that I copied and then when I submitted it, I got the SMF cannot connect to database error so my post went off into cyberspace again!

Anyway, a rechamber to .458WM may be a moot point since the rim cutout of the .45-70 is larger than the rim of the .458WM.

Even if it will work, the SAAMI MAP of the .458WM is 53kcup which is much higher than that of the .500S&W at 50kpsi, and would push SB2 frame strength to the limits, might not last long.

http://www.frfrogspad.com/miscellk.htm#pressure

A far better choice IMO, would be to just throat the .45-70 Handi/BC so bullets could be seated longer providing more powder room and subsequent less pressure, or rechamber to .45-90 or .45-100.

Even max levergun loads have too much recoil for most shooters, so I would recommend shooting some heavy loads in the .45-70 to see if you even want to go there, here's some data that will make most .45-70 shooters quite gun shy, if you like a 525gr BTB at 1800fps, then you may appreciate doing more along this .458WM line of thinking.

Tim

http://beartoothbullets.com/open_sight/archive_open_sight.htm/21








EDIT: SAAMI MAP link added.

[mattparliament]

The 2006 Hodgdon manual has some really nice loads in the 43K-48K range, also at the 50K range and max out at 52K.

Ouch.

[Mac11700]

The 2006 Hodgdon manual has some really nice loads in the 43K-48K range, also at the 50K range and max out at 52K.

Ouch.

Yup...they are stout for sure...All in all...the frame may handle it...it may not...but...I doubt you'll find a reputable smith willing to do the conversion anyway...even if the cases were closer.....and if you do find one willing...I'd be very leary of them doing this conversion....Some folks I have heard are even pushing the 450 M to extreamly higher levels.well above these pressures....G...aaaads... ...I'll stick to my 2400fps 300 grain Marlin loads...that's more than enough for my poor shoulder...Hmmmm...maybe someone here will buy a reamer and see if it works...stranger things have happened

Mac

[dewy]

I would try the 525gr at 1800fps before I moved up, trust me but first a longer throat for the NEF

Dewy

[marlin mike]

Ok so much for my bright ideas. Thanks for all your info and imput. Guess I don't need one that bad. Sigh!