marlin 1895 design question

500bfrman
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marlin 1895 design question

Postby 500bfrman » Fri Dec 25, 2009 4:45 pm

Seems like I remember some threads info on here about design for this gun. But alas I can't find them now. I just want to make sure I don't mess up. Is there something I need to watch for? like throat? or are most of these throatless? i saw the design you had done, thinking about going with that. is bore riding a problem with this gun?

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mtngun
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Re: marlin 1895 design question

Postby mtngun » Fri Dec 25, 2009 8:36 pm

Marlins usually have a SAMMI throat. The SAMMI 45/70 throat is throatless, however, sometimes the case is shorter than the chamber, leaving a bit of a jump between the case mouth and the rifling. With a Marlin, it can go either way, with the case mouth right up against the rifling, or with a bit of a jump to the rifling. Also it will depend on your case trim length. Plus, if it is a used rifle, the previous owner may have firelapped it, which usually lengthens the throat.

If you really want to know, make an upset slug impression of the throat, and tell us what you find. If it's a new rifle, I'd lay money its a SAAMI throat.

This thread suggests a design for the Marlin 45/70. I've made quite a few of these and never had a single complaint about it.
http://www.mountainmolds.com/phpBB3/viewtopic.php?f=7&t=74

A short bore riding section is a good idea in Marlin lever actions, and the suggested design has one.

500bfrman
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Re: marlin 1895 design question

Postby 500bfrman » Sat Dec 26, 2009 9:03 am

I was reading about upset slug impression on this forum. I don't have a mold to cast from though. Will a jacketed bullet work in there backwards. Then close the lever, and what comes out is what my throat is? or is this my leade? it came out at about .150 longer than the brass. the gun is new. the jacketed was .457,8.

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mtngun
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Re: marlin 1895 design question

Postby mtngun » Sat Dec 26, 2009 11:27 am

Your backwards jacketed bullet test is telling you that there is 0.150" between the case mouth and the rifling. I suspect that is due to the chamber being longer than the brass, and not due to an honest-to-goodness throat, but nonetheless 0.150" gives you plenty of room to work with.

The 0.150" will be the design program's "rifle throat length." As long as your bullet design stays under the 0.150" throat length, and the COL is correct, you should be fine.

500bfrman
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Re: marlin 1895 design question

Postby 500bfrman » Sat Dec 26, 2009 12:09 pm

when I put the bore riders in as the bullet design the rifle throat goes way down. That's good. my question now is if the front band is .100 and the bore rider is .150. won't that bore riding part be on the rifling? WOuld that be a chambering issue or a pressure issue? I realize the bore riding section isn't the full 460 diameter but didn't know if it would be an issue with the groove diameter? I think all my terminology is right. thanks for all your help. or am i talking about bore diameter? anyway. my questions remain the same

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Re: marlin 1895 design question

Postby mtngun » Sat Dec 26, 2009 1:45 pm

Yes, if you have a 0.100" long front band followed by a 0.150" bore riding section, then bore riding section will be into the rifling.

That's OK as long as the bore riding diameter is no bigger than the barrel's bore diameter. With a lever action, it is best to set the bore riding diameter to err on the side of easy chambering.


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