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Thread: 7mm Rem Mag Conversion to 300 RUM?

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    Default 7mm Rem Mag Conversion to 300 RUM?

    What would it take to rechamber a 7mm Rem Mag (M77 with tang safety) to a 300 RUM. The difference in COAL appears to be about .36 and there doesn't look like a lot of room to configure a new mag box???

    Is it possible?

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    Member Big Al's Avatar
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    Quote Originally Posted by MontanaRifleman View Post
    What would it take to rechamber a 7mm Rem Mag (M77 with tang safety) to a 300 RUM. The difference in COAL appears to be about .36 and there doesn't look like a lot of room to configure a new mag box???

    Is it possible?
    BUDDY, you do know that the RUM is about a mile longer that even an H&H don't you?
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    Quote Originally Posted by Big Al View Post
    BUDDY, you do know that the RUM is about a mile longer that even an H&H don't you?
    Al,

    I may have step on it here earlier on the other thread, I haven't measured any recent M700 since the RUM's came out is a 30-06 and 300 RUM the same length inside? So like a 7 mag could be rechambered 7 RUM and work fine with no other chamges? How many different length actions does Remington make (in M700)? Ok a 223 length, right? And a everything else length?? This face really suits me right about now.
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    Quote Originally Posted by Big Al View Post
    BUDDY, you do know that the RUM is about a mile longer that even an H&H don't you?

    Anymore good news???

    What else could I convert it to? Want to get away from the belted cases.

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    Quote Originally Posted by Murphy View Post
    Al,

    I may have step on it here earlier on the other thread, I haven't measured any recent M700 since the RUM's came out is a 30-06 and 300 RUM the same length inside? So like a 7 mag could be re chambered 7 RUM and work fine with no other changes? How many different length actions does Remington make (in M700)? Ok a 223 length, right? And a everything else length?? This face really suits me right about now.
    No Murphy, your right about the RUM it is a longer action. And I don't mean just a little bit either. Take a RUM case and Hold it in your hand along side a H&H case. It's scary. Yes your correct that Remington has a short action. a medium action and for sure they got the RUM. When I look up the part numbers for the .300 H&H/.375 H&H and follower, they have different part numbers. I know that I did a 10.57mm Meteor on a Mag action, had to get a special mag box for it and the action and bolt had to be modified, Mic Bros did the work. You know anything that has Lazzaroni on it comes dear. In fact that was the most expensive conversion work I ever paid for.

    I wish I had a 700 in the shop to get this idea out of my mind that it can't be done with out machine work on the action. Way long ago I did several conversion from .300H&H to .375 H&H, a couple for a couple of left handed brother from Fairbanks. They were easy. I did a couple of 721 from .300 H&H to .375 H&H..

    We will clear this mystery up when Pac-Nor returns my call! You know these boys will have the answer you can take to the bank.
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    Quote Originally Posted by MontanaRifleman View Post
    Anymore good news???

    What else could I convert it to? Want to get away from the belted cases.

    Hold off till I get word back from Pac-Nor. You know that the reason most people want to get away from belts is any easy solve problem with a special die to size down to the belt. Not cheap, but it is in the long run. I no longer have to say no to folks that want to give me once fired belted brass. I still like the .358 Norma conversion the best. It's a vary cheap conversion Only requires a re bore and re-rifle and chamber work. Believe me a guy could not ask for more rifle than that.
    "The tree of liberty must be refreshed from time to time with the blood of patriots and tryants." (Thomas Jefferson

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    Quote Originally Posted by Big Al View Post
    Hold off till I get word back from Pac-Nor. You know that the reason most people want to get away from belts is any easy solve problem with a special die to size down to the belt. Not cheap, but it is in the long run. I no longer have to say no to folks that want to give me once fired belted brass. I still like the .358 Norma conversion the best. It's a vary cheap conversion Only requires a re bore and re-rifle and chamber work. Believe me a guy could not ask for more rifle than that.
    The die thing wouldn't be an issue, but still would like to move away from the belts. Would consider it though. Where can I find ballistics on the the 358 Norma and what in the world would I do with a 358 in Montana? Interesting, but not sounding very practicle for this Montanan. I have considered a 338 RUM but a 358 just seems out of place. What a bout a 7mm RUM? Barnes is showing a 3.575 COAL and i just measured three of my handloads at 3.317 and there's about .1 play in the box with those loads. Not too far off??? What ya think?

    Actually measured the inside of my box @ 3.361.

    Hold off till...
    There aint no hurry on this, probably a year out

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    Quote Originally Posted by Big Al View Post
    BUDDY, you do know that the RUM is about a mile longer that even an H&H don't you?
    Where do you come up with this stuff at?

    The 300 RUM and 375 H&H have the same length case.

    Have you even held either cartridge before?

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    Quote Originally Posted by Matt View Post
    Where do you come up with this stuff at?

    The 300 RUM and 375 H&H have the same length case.

    Have you even held either cartridge before?
    I think it should be obvious by now, OUT OF MY *****.

    I don't know because I haven't gone down to the shop to grab a .375 H&H case to compare to the .300 RUM cases I have by the computer. But I can tell you this, it takes a different mag box for the RUM and that just came from a guy that does this every day.

    Now so I don't have to start a new thread, I now know that the standard action 700 will take all ctgs. Even if it's a 30-06. Just need a new extractor re-riveted in after the bolt face is opened up to .541-.542".
    (and opening up the barrel channel of course for the larger dia. barrel)


    So yes it just a matter of a re barrel to make your 7mm Rem mag into a .300 RUM or a .375 H&H. Or whatever else you can think of that Remington chambers as long as the bolt face is the same as the ctg.

    Are you happy about that good news? You were right and I was wrong.
    "The tree of liberty must be refreshed from time to time with the blood of patriots and tryants." (Thomas Jefferson

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    The 300 RUM is the same length as the 375 H-H.

    Problem is neither will fit a M77.


    There are some cool cartridges that are based on the rum case shortend that will fit in the M77. Including a cool .475 caliber.

    http://forums.accuratereloading.com/...43/m/769108843


    --------------------------

    You could always do a 300/375 ruger (not the pipsqueek 300 ruger) no belt and plenty of case.


    ----

    As for the hijacked rem 700 questions the rem 700 magazine will fit the 30-06 to ultra mag. The difference will be in mag width not length. Maybe only a different mag follower. So a 7mm rem mag can simply be rechambered to 7mm rum with maybe just a new mag follower. The largest cartridge I have seen in a mod 700 is a 10.21 meteor (Lazzeroni version of .416) which is a very large case like a rigby case.

    Rem has short action and long action.

    Winchester does too but for a medium cartridge like the 30-06 or 338 win mag the magazine will have a spacer in it to shorten mag length.

    Unfortunately ruger actions are medium length for 30-06 length cartridges only.
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    Member shphtr's Avatar
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    I have a number of these conversions in light sheep rifles and shoot them regularly. Prob the best conversion from 7mm Rem if you want to stay with a 7mm and want to go "beltless" is the 7mm Dakota. I know next to nothing about Rugers, but for Rem's you will need a different size mag box (avail from Rem) and new follower (also avail from Rem). Bolt face size for the RUM and classic belted mags are the same - for Dakota chambering often have to open up the bolt face another .012. The different mag box has the shoulder cut outs to better accommodate the larger diameter of the RUM. To convert a mag Rem 700 to one of the RUM's you will need a barrel of the appropriate chambering, new mag box and follower with spring (I always get the new follower spring but it may be the same as a mag - don't know myself). I do not own any Rugers and don't know squat about their inerards! Best with 24 - 26 inch barrel and for ultra light weight rifles muzzle brake is something to consider. Good luck.

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    Member alaska bush man's Avatar
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    Thumbs up 300 Win

    It would be much easier to convert to a 300 Win Mag......just a barrel change
    Alaska

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    Thanks for all the input, I really appreciate it. I don't really want anything bigger than a 338 becuause I'm not going to Africa or Kodiak anytime soon.

    I'm thinking a 7mm WSM should be an easy conversion and the WSM has a lot of advantages over the Rem Mag.

    Wha'do ya think?

  14. #14

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    Quote Originally Posted by alaska bush man View Post
    It would be much easier to convert to a 300 Win Mag......just a barrel change
    Great idea but already have a 300 WSM

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    Quote Originally Posted by shphtr View Post
    Prob the best conversion from 7mm Rem if you want to stay with a 7mm and want to go "beltless" is the 7mm Dakota.
    I think you're right, Just checked the ballistics on the Dakota and it will give me up to 250 fps more than the Rem Mag and the case lengh appears to be the same. This looks like a good and easy solution.

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    Quote Originally Posted by MontanaRifleman View Post
    I think you're right, Just checked the ballistics on the Dakota and it will give me up to 250 fps more than the Rem Mag and the case lengh appears to be the same. This looks like a good and easy solution.
    Necking down 375 ruger to 30 caliber would give you easier acces to brass and you would not have to have the bolt face worked on either. Ballistics would be similair to 300 WBY.

    Of course 100 brass would last a long time too. At least for me it would.
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  17. #17

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    Quote Originally Posted by RMiller View Post
    Necking down 375 ruger to 30 caliber would give you easier acces to brass and you would not have to have the bolt face worked on either. Ballistics would be similair to 300 WBY.
    Interesting, do you know anyone who has done this? Any ballistic data on it?

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    Quote Originally Posted by MontanaRifleman View Post
    Interesting, do you know anyone who has done this? Any ballistic data on it?

    I have been wanting to do it with a Kimber Montana. Take a 300 win mag and have it rechambered. All you have to do is take a 375 ruger reamer and ream the body because the neck of the 300 win mag is exactly where it needs to be for the 300/375 ruger. I guess the 375 ruger die would still need a 30 cal pilot.

    I will look to see if it has been wrote about yet as it surely has been done by now.

    The size of the case tells me it will be faster than the 300 win mag because it holds more powder.

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    Member RMiller's Avatar
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    the 300/375 ruger has been done before but I have not found ballistics yet.

    Jeffeoffo,
    I have been grinding a lot of wildcats such as the 6.5/375 Ruger which has been winning a lot of matches this year. We have had ordres in just about every wildcat you can think of using the 375 Ruger case. I have talked with many folks about the 375 Ruger but I know of no plans of Ruger coming out with a family of rifles in long or short versions. I have talked with several gunsmiths and benchrest shooters about my opinion on the case being necked up and down as I really believe in the performance of this case. I hope that people don't jump to conclusions that Ruger and Hornady are going to come out with a family of cartrides and rifles just because I am pushing the wildcats. I respect Prescott's support of the case but I have no imformation on any other calibers coming out in the future.
    Thank you,
    Dave Kiff, Owner of Pacific Tool and Gauge
    sounds about right for 300 wby ballistics. This also duplicates the 30 newton.

    If you neck down a 375 ruger in the newton die then trim to 2.5 it work in the newton. This was actually done with a guy who used a 35 newton.

  20. #20

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    Quote Originally Posted by RMiller View Post
    the 300/375 ruger has been done before but I have not found ballistics yet.

    sounds about right for 300 wby ballistics. This also duplicates the 30 newton.

    If you neck down a 375 ruger in the newton die then trim to 2.5 it work in the newton. This was actually done with a guy who used a 35 newton.
    Sounds real interesting, still like the idea of the 7mm Dakota. With the Dakota I can probably get 3400 fps with a 150 E-Tip which will get me opening velocity of 1800 fps out to about 1000 yds out of a 26 or 27" bbl.

    The Dakota brass sure is spendy but forming the 300/375 brass will take some expense and effort too. If I could get 3100 fps with a 200 gr bullet out of the 300/375 I would probably go for it, Need to do some research.

    Still have a lot of time to think about. Thanks for the info.

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