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Thread: Model 70 winchester

  1. #1

    Default Model 70 winchester

    I have a model 70 Win. in 7mm Rem. Mag. I think this gun has excessive head space. I start getting case head seperation after 3 or 4 loadings. That is after full length resizing. This gun shoots real good. I just want to see what my options are. Can this gun be reamed to a 7mm STW? If so will the bolt and magizine work for the STW cases and bullets? I have another 7mm Rem, and I have dies and a lot of brass for the STW and no rifle at this time. The STW I had would not shoot accurate and it moved to a new home.

    I know I could have the barrel cut, rethreaded and set back, or necksize to increase the number of loadings bofore wearing out the brass. What are my other options? What would you do if this was your gun?

  2. #2
    Member Diesel Nut's Avatar
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    I don't know how long you've been loading, so I need to make ask: Are you sure it's the rifle and not your loading process? If you set the shoulder back too far when resizing, you'll fatigue cases and get head separations after only a few loads.

    You should be able to open it up to STW without much problem. The STW reamer will clean up the old chamber just fine, so no worry about setting the bbl back or anything. I can't find receiver specs on the M70, but I don't think they offer anything other than a short and long action, which means the extra length of the STW of the standard magnum case shouldn't be a problem.

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    I am willing to bet you are setting the shoulder back to far when full-length re-sizing. This causes more stretching of the case when firing = short case life.

    Try this,

    Take a couple of pieces of factory ammo and a spent pistol casing that will fit over the neck of 7mm Mag. You want the mouth of the pistol case to rest of the shoulder of your rifle case. Take a measurement. Lets say its 3.484", this is you reference for X brand factory ammo (which should be in SAMMI spec). Now take a case that has been fired once or twice in your rifle which hasnt been re-sized. Make the same measurement with the pistol case over the top. It should be only .005-.009 greater than the factory ammo you measured previously.

    When you set your re-sizing die, you want to push the shoulder back only .002" from your fired case. Start with the sizing die just barley touching the shell holder than measure, 1/8 more, measure, etc. Ive seen some manuals recommend 1/4 turn past touching the shell holder. This will cause premature case failure most of the time.

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    Quote Originally Posted by TomM View Post
    I am willing to bet you are setting the shoulder back to far when full-length re-sizing. This causes more stretching of the case when firing = short case life.

    Try this,

    Take a couple of pieces of factory ammo and a spent pistol casing that will fit over the neck of 7mm Mag. You want the mouth of the pistol case to rest of the shoulder of your rifle case. Take a measurement. Lets say its 3.484", this is you reference for X brand factory ammo (which should be in SAMMI spec). Now take a case that has been fired once or twice in your rifle which hasnt been re-sized. Make the same measurement with the pistol case over the top. It should be only .005-.009 greater than the factory ammo you measured previously.


    When you set your re-sizing die, you want to push the shoulder back only .002" from your fired case. Start with the sizing die just barley touching the shell holder than measure, 1/8 more, measure, etc. Ive seen some manuals recommend 1/4 turn past touching the shell holder. This will cause premature case failure most of the time.

    I would bet money this is the problem. You can also just neck size some and see if that cures the problem. If no necks are being cracked now then you are bumping the shoulder back a bit to far.

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    [QUOTE=TomM;649433
    When you set your re-sizing die, you want to push the shoulder back only .002" from your fired case. Start with the sizing die just barley touching the shell holder than measure, 1/8 more, measure, etc. Ive seen some manuals recommend 1/4 turn past touching the shell holder. This will cause premature case failure most of the time.[/QUOTE]


    Good advice but I think your starting point is off. If it were me I would set the resizing die above the shell holder about the thickness of a nickel. Lube up and run three fired cases through the die and try to chamber them in the rifle they were fired in. If they do not chamber with just a hint of resistance lower the die 1/4 turn and repeat the process. Once you find your sweet spot for that die/rifle lock the die into place.
    Remember, the die will only be adjusted perfectly for that rifle. In the long run I've found it easier to buy different dies for each rifle we own in the same caliber and the ammo is kep separate.
    Tennessee

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    Default Belted case seperations and headspace

    Remember that the 7mm Mag is a belted case. If the rifle is headspaced correctly off the belt then it is not technially a question of headspace although the cases will stretch and seperate if the chamber is too long or the dies push the shoulder back too far.

    Backing the dies off and headspacing off the shoulder is a popular work-around. However you may find that the cases don't get sufficently resized just above the belt and after a few firing they may get hard to chamber. If that happens run them into a .300 Weatherby or .458 die with the decapper / expander removed. Set the die screwed down to make hard contact with the shell holder. Using those dies will size down the base without touching the shoulder. Then you can go back you your regular sizing routine as described by others.

    A small base sizer die is a handy thing to have around if you use range brass. I've salavaged a lot of brass this way where it was shot in a maximum sized chamber and my guns had chambers more toward the mimimum size.










    Quote Originally Posted by Cast Iron View Post
    I have a model 70 Win. in 7mm Rem. Mag. I think this gun has excessive head space. I start getting case head seperation after 3 or 4 loadings. That is after full length resizing. This gun shoots real good. I just want to see what my options are. Can this gun be reamed to a 7mm STW? If so will the bolt and magizine work for the STW cases and bullets? I have another 7mm Rem, and I have dies and a lot of brass for the STW and no rifle at this time. The STW I had would not shoot accurate and it moved to a new home.

    I know I could have the barrel cut, rethreaded and set back, or necksize to increase the number of loadings bofore wearing out the brass. What are my other options? What would you do if this was your gun?
    Living the urban lifestyle so I can pay my way and for my family's needs, and support my country. And you?
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  7. #7

    Smile loading problem...

    I think your getting good advice. When I first started loading ammo in the 70's I ran into the same issue. When I followed the instructions that came with the die I would get a case separation just above the belt. Then I learned to head space off the shoulder. That worked fine untill the round would not chamber because the base of the case was not resized enough. Years ago I ordered a "Belted Magnum Collet Resizing Die from Innovated Technologizes". Now I run all my brass thru it before I run it thru the resizing die. This allows me to load brass that was fired in my rifle correctly, at least for me. There is more then one approach to this as suggested but for 89.00 my issues went away. I have loaned this die out to friends who were having the same problems as you and there problems went away. I used to only use "once fired or new brass" for my hunting rounds. Now I will use brass that has been fired 3 times. After that it goes into the "practice" pile. Good luck.

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    Default Feeler guage

    I've had problems sizing a AI cartridge. The base above the belt wasn't sizing well. To make a long story short I adjusted the FL sizing die to where the brass would chamber and it would size the neck correctly then I use a feeler guage to measure the Gap wrote down which two sized guages I needed for those dies and now when I want to load bullets in that cartridge I put the ram al the way up and hold the guage on the shell holder and screw the dies down until it touches the guage.

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    Quote Originally Posted by hntr View Post
    Now when I want to load bullets in that cartridge I put the ram all the way up and hold the gauge on the shell holder and screw the dies down until it touches the gauge.
    Pretty slick, good use of your feeler gauges for sure.

    I'm fortunate that I use a 550B and I leave all of my dies adjusted for each rifle on the tool head. It makes for a very quick set up.

    I was always wondering how I would set up a die in a hurry on a traditional press, your way seems very practical and repeatable.

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    Quote Originally Posted by tvfinak View Post
    However you may find that the cases don't get sufficently resized just above the belt and after a few firing they may get hard to chamber. If that happens run them into a .300 Weatherby or .458 die with the decapper / expander removed. Set the die screwed down to make hard contact with the shell holder. Using those dies will size down the base without touching the shoulder. Then you can go back you your regular sizing routine as described by others.
    Another great idea.

  11. #11

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    Thanks guys this is good information. I have two 7mm Rem. Mags and the die was set up for the other gun. I have been loading for about 35 years but had never run into this problem before. I will defenately hold off on doing anything to the gun until I check these things out. Most of my dies are RCBS but the last two I bought were Hornady New Dimension and I like these dies very well. I will pick up a set of these dies for this rifle and experiment before I do anything else. I had not thought about setting the shoulder back to far. This gun has a smoothe action and trigger and shoots well. It will be nice if I can solve the problem and not mess this gun up.

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