Build question

Discussion in 'Gunsmithing' started by winmag, Sep 11, 2010.

  1. winmag

    winmag Well-Known Member

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    I have a Winchester Model-70 (ya I know ''who'd have guessed'') chambered in 300wby. I only have less than 100 rounds down the pipe, but for some reason I dont like it. So I looked up J E's post on bolt face diameters shown here;

    Long actions with a bolt face .Dia of .540 +/-
    264 Win Mag, 270 weatherby Mag, 7mm Rem Mag, 7mm Weatherby Mag, 7 STW,
    7mm Rem Ultra Mag, 300 H & H, 300 Win Mag, 300 Weatherby Mag, 300 RUM, 303 Brit,
    8mm Rem Mag, 338 Win Mag, 340 Weatherby Mag, 338 RUM, 375 H & H, 375 Weatherby,
    375 RUM, 416 Rem Mag, 458 Win Mag, and the 458 Lott.

    Now my questions are;
    1. Can I turn my Model-70 into a 338RUM?-same bolt face, and c.o.a.l. of .04 more than the 300wby, or is that .04 longer c.o.a.l. not gonna jive with my action.
    2.Would a 338 RUM with a 28'' pipe be near the Edge for velocity? I dont want to monkey with brass necking up a 300RUM into 338 edge. and bother with custom dies etc.
    3.Would there be any forseeable problembs, such as needing new bottom metal, will the current action length be ok etc? Im not planning on shooting super long 300gr. Bergers. Probably 225gr, or 250gr Accubonds.
    4. I love my Model-70's and unfortunately Winchester does not currently offer a 338RUM chambering, or I could just go that route. Heres my delima:D
    I want a 300wsm and I have a 300wby:cool:
    I want a 338RUM and I have 338WIN:cool:
    Am I better off parting ways with both and getting the 300wsm, and wait and hope Winchester/FN comes out with a 338RUM offering sometime in the futre? Or should I sell the 338 and buy a 300wsm, and build my Model-70 300wby into a 338RUM-IF ITS POSSIBLE-?
     
  2. specweldtom

    specweldtom Well-Known Member

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    Winmag, I may be able to help a little bit. I'm not familiar with the Mod 70 action, either pre '64 or post '64 push feed, but I'll share what I do know.

    First, if it's a post '64, be sure the serial # has a G prefix. The ones without the G prefix I believe are investment castings. They made them during the transition. If it's a pre '64, they're all forged.
    I wouldn't barrel up a RUM on a cast receiver. Just my opinion.

    On the bolt face, the only thing I recommend is if the Winchester bolt has a recessed face like the Rem or Wby, turn a slight chamfer on the inside front corner of the lip to be sure you headspace on the base of the cartridge and not the bevel on the cartridge just in front of the extraction groove. I saw that happen on a Rem 700 bolt.

    #1 question. If you are willing to single load, no problem. The cartridge OAL's you listed are probably maximum SAAMI OAL's and could be loaded short enough to fit in a .300 Wby length magazine, particularly with 200-225gr bullets.

    #2 question. Given the same barrel length, the .338 RUM can't quite match the Edge performance, but it is so good that I could live with it easily.

    #3 question. You may not need new bottom metal, but you will need a mag box and follower that will feed the fat RUM case. The .300 Wby is a staggered feed, and may not be able to be modified to feed the RUM cartridge. The right pieces are available for Rem 700's and Wby MK V's, but I don't know about the Mod 70.

    The .338 Win Mag bolt face is a std belted mag bolt face and the .300 WSM has a .473 case head. It's not on JE's list. You would have to change bolts. Instead, look at the Rem .300 Short Action Ultra Mag (SAUM). It should work, and might feed out of the .338 Win magazine. I haven't done it, so I don't know.

    #4 question. I will always spend money on a custom barrel instead of expecting a factory barrel to perform satisfactorily. My experience is that factory barrels only meet 1 moa about 25-30% of the time. A quality custom barrel such as a Lilja, Krieger, Hart, etc. will do it every time if the installation is done right. Also just my opinion.

    Except for solving feeding problems, I think you can rebarrel your rifles to do what you want. If you know a 'smith who is building consistently accurate rifles, talk to him about your projects. There's an excellent chance that an experienced professional riflesmith can answer your questions definitively.

    I hope that some more knowledgable members will jump in.

    Good luck, Tom
     

  3. NesikaChad

    NesikaChad Well-Known Member

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    After building quite a few guns over the last 12+ years this is what I've pretty much whittled this sort of question down to:

    1. Is or can the bolt face be altered to physically retain the rim of the cartridge?
    2. Is or can the action magazine well/feedlips be altered to facilitate loading?
    3. Is the ejection port long enough and can it be lengthened if its too short?

    If yes is the answer to all three then give it hell.


    In your case:

    If the action you have uses a "T slot" style extractor then it's going to be a bit tricky to open the bolt face. It's not as simple as a guy would like. There are a couple things that need to be addressed. This particular extractor runs via a hole that's drilled in the face of the lug. A spring/plunger goes into this hole. It then drives a cone shaped (generally) countersink that is in the extractor. Opening the bolt face for a larger cartridge means that the extractor must move away from the center of the bolt face in order to be able to purchase the case rim for extraction and to be able to snap over the rim of the case when loading. The snapping action comes from the extractor begin able to slide back and forth in the T slot.

    If I was head set on doing this then I would probably attack it by machining a pin to fill the hole that the spring/plunger goes into. I'd then solder the pin in place with some low temp stuff (so as not to kill the heat treatment of the bolt lugs) and then relocate the hole. Chances are the extractor will need to either be made over or modified as the radius is different on the case/extractor.

    That's a push feed style.

    If it's a CRF (control round feed) then essentially the same basic process will need to take place, although it'll be a little different. The bolt face has to get bigger and the extractor needs to be refitted to make the thing work right.


    IMHO a magnum type cartridge that does NOT use a belt around the case web is always more desirable than one with a belt. They just run easier and the gunsmith chambering the gun can take advantage of a true headspace dimension instead of just using the belt. (Although I personally have all my gauges made so that I take a true shoulder/case head length when chambering)

    What I would NOT do under any circumstance:

    Have a Sako style extractor installed. I am very opinionated on this for safety concerns. I have a cardinal rule regarding them; I will not install or service a Sako extractor installed on a twin lug, 90* turn bolt action that uses a full length raceway.

    The reason is simple. The extractor isn't supported by anything when the bolt is in battery. If a case ruptures that little bastage will come flying out and if it hits a person it's very possible to kill or critically injure that person. I know of two cases this year alone that resulted in surgeries.

    Hope this helped.

    Chad
     
  4. winmag

    winmag Well-Known Member

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    Thanks guys.
    I appreciate the info.
     
  5. shortgrass

    shortgrass Well-Known Member

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    My sediments about the Sako style extractor exactly! Have ya' priced that Winchester push feed extractor lately? Tom, I've re-barreled several .300 RSAUMs' to .300WSM. Same bolt face. The reason,,,, ammo/component availabilty.
     
  6. RJ338

    RJ338 Well-Known Member

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    Some good advise given already, but I'll offer my 2 cents. You already have a 300 Wby, so the bolt face is the same as the 338 RUM.You will need a new mag box and follower. It probably will be tough to find though they were made in 300RUM (same as the 338), problem is the feed rails may or may not work, necessitating some work. Get at least a #4 contour custom barrel and a good brake(Vais, DE, Muscle brake- ranging from unobtrusive to offensive and all LOUD). The contours of all barrels will be heavier than the Winchester and need to be, so you will need to open up your stock or replace with a good (Mcmillan, High Tech or Manners) stock. This has already added up to quite a sizable investment... So how much better than the Weatherby is it... For BIG longrange game it is a major step up in killing power for a carry gun- not into the league of the EDGE shooting 300gr bullets. Those are dedicated platforms and require the commitment to the discipline to master and use. If you go that route please go the whole way, it isn't just a rebarrel.
     
  7. bigngreen

    bigngreen Well-Known Member

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    Man, I can't believe I missed your thread man! If a man doesn't have something to launch a 300 Berger at an elk I think that should be priority #1 :D

    I had a guy ask me about tweeking on a Win Mod 70 chambered in a 270WBY and I got to looking around and an earlier Win factory chambered in a WBY can be a gold mine so I told the guy not to tweek it but buy another gun to work with!

    I haven't measured up a Mod 70 for an RUM so I have no real advice there, I should measure up my dad's to see how it would fit. I would just roll with the 338RUM though, being just a tough shorter helps the feeding and there is hardly any practical difference between the RUM and EDGE.
     
  8. specweldtom

    specweldtom Well-Known Member

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    Shortgrass, I had an older Barnes (#3) reloading manual in the house and looked at it last night to get the rim diameter of the .300 WSM. It shows .473". I thought that was strange, but didn't look any further. After catching up on the thread this morning, I went out to my garage and looked at my Nosler manual and sure enough it shows .535". The .338 Win Mag bolt face will work with the .300 WSM.

    Winmag, It still looks like feeding out of the magazine will be the biggest issue on the .300 Wby to .338 RUM, but Winchester parts might be available to convert the .338 Win Mag to a .300 WSM. The factory WSM box is probably shorter than the .338 box, but should be able to be fitted and bedded into the longer well.

    Chad asked 3 key questions.

    #1. No alteration to the bolt face would be needed for the .338 Win Mag to .300 WSM, and if required at all, altering the .300 Wby bolt face for the .338 RUM would be the slight chamfer on the inside front of the bolt lip, (and maybe touch the corner angle on the face of the sliding extractor).

    #2 is the biggie. I don't know the answer to that one unless you're willing to single load.

    #3. The .300 Wby ejection port should easily clear a .338 RUM fired case. The .338 Win Mag ejection port might be long enough to clear an unfired .300 WSM, so a fired case would have all kinds of room.

    Never having done these conversions limits me to just reasoning my way through the process (pretty scary since I often miss something important), but with the other replies, maybe we've given you enough to go on.

    Let us know what you decide to do. Tom
     
  9. winmag

    winmag Well-Known Member

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    Sorry I shouldve clarified;
    The 338 win mag is a Browning A-Bolt, so it will be sold. I have not hered hardly anything good about building a Browning, and I dont want to start a build by going backwards. So the 338 will be sold to fund the 300wsm purchase in Model-70 Win.

    My current Model-70, 300wby is the only one I wanna convert.
    I have alot of thinking to do. I dont want to single load. and I want a carry gun, so Im staying away from the big stuff. But I do want a 338 to launch 225-250gr bullets with some authority to 800ish yards.
    I realise that I already have rifles capable of this, but I am a firm beliver in overkill:D, thus the RUM chambering.
    I already own a 270wsm and LOVE it-as most of you know-
    If I got the 300wsm, for an ''inbetweener'', and had the 338RUM for the realy big stuff at extended range I feel I would be well rounded in the range I am currently comfy shooting at, and have room to grow a bit along the way. I dont think that the gun is gonna give me the tallent that some folks have, nor do I think I can make up for marginal accuracy with ''horsepower'', but I do think its a step in the right direction for being able to extend my range as my ability grows. Plus, someday when I have alot more $$$$$ than I do now, I would like to own a full on custom, dedicated long range rig, so the Rum chambering seems like even more of a good stepping stone/Leartning tool, for longer range shooting, and builds.
    I just figured before I go dropping tons of $ on my 300wby for a brake, extending the length of pull, and some other issues, Id see if I had the proper makin's for a RUM conversion, without alot of headache.
    P.S. Bigngreen, its not the super expensive one, its only about an $800 rifle, by todays prices. But its a safe queen and looks too sexy to shoot:D, so I may as well make something usefull out of it. Ie; If I already have a 270wsm, and am going to get a 300wsm, why have a 300wby?........when I can have a 338 RUM:D.
    As far as the stock goes.......I dont wanna offend anybody, but I cant stand composite stocks, so I would either alter the one I have, or have to order a custom wood one with an aluminum bedding block inlayed...... LOTS of $$ that Id rather not spend if I could use/modify what I already have for now.
    Like I said I have alot of thinking to do before I start talking to a smith with cash in hand. I tend to be ''rash'' when I have a dollar burning a hole in my pocket.
    Thank you to all who have replied. This helps alot in making a decision of exactly what it is I want to do. Your comments are very educational, and I appreciate them all.
     
  10. NesikaChad

    NesikaChad Well-Known Member

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    Now to really screw you guys up.

    Norma now has the 338 Norma magnum. I have the reamer on the shelf and just finished a "lab rat" rifle for an ammunition manufacturer that's filling big big orders for the LE/Military crowd.

    Looks like a winner so far!

    Have a great weekend.

    c
     
  11. Coyboy

    Coyboy Well-Known Member

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    I finished a win 70 long action in 338 edge a couple months ago and it was pretty straigt forward. I added a wyatts box in the CRF action. That takes a little bit more work then in a 700 but is very doable. Think it was a 4 fluted packing gun.
     
  12. specweldtom

    specweldtom Well-Known Member

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    Yeah, from what I've read, I have the same impression of the A-bolt as a candidate for customizing.

    I have no problem confusing the issue either. Have you thought about the .340 Wby on your .300 Wby donor? It's about 200 fps faster than the .338 Win Mag, and the ones I've had loved the 250gr Nosler Partition factory load. That combination is poison in a carry weight rifle. A muzzle brake is not necessary, but felt recoil is high in a light rifle. It won't hang with the RUM, but can get within 150 fps with the 250gr Nosler, and the aforementioned Barnes book shows the 2 cartridges in a dead heat with 200gr and 250gr Barnes bullets. Both the Nosler and Barnes books used 26" barrels for both cartridges. As barrel length increases, the RUM will pull away from the Wby with all bullet weights because of the greater powder capacity, but in a carry weight rifle, they are closer together. At 2800 fps muzzle velocity, the .340 (250gr Nosler) drops to 2000 ft/lbs at 510 yds, with 1900 fps retained velocity. At 800 yds it's down to 1300 ft/lbs and 1500 fps. Still supersonic, and accurate, but below the 2000 ft/lbs that has been recommended for Elk. Been wanting to do it because my home built .340 likes that bullet too.

    I ran the .338 RUM at 2990 fps muzzle velocity and came up with 1477 ft/lbs at 800 yds with 1627 fps retained velocity. It drops to the 2000 ft/lb threshold at 600 yds, with 1930 fps retained velocity. Not nearly as much difference from the .340 as I expected. I got these numbers off my Oehler Ballistic Explorer. I ran them at 25' above sea level with 90% relative humidity and 70 deg F. The G1 ballistic coefficient of the 250gr Partition is .473.

    How's that for muddying the water? Tom
     
  13. RJ338

    RJ338 Well-Known Member

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    The 338 RUM will move a 210TTSX at nearly 3350 and in mine at 9.3# and a Vais brake it is a pussycat. The 338 Norma w/300gr MK at 2720 in the same wt..gun will get your attention. Both the Norma and Edge will eaqsily do 2750 with the Berger VLD-with a 250yd zero that is -220 @1000yd and 2400 ft lb. Shawn sure got the Edge right, what say Spectom?
     
  14. specweldtom

    specweldtom Well-Known Member

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    RJ, I didn't compare the Edge because Winmag said he preferred not to fireform, buy custom dies, etc so I just made the comparison with the factory RUM cartridge. The velocities your RUM is getting are great, especially out of a 26" (or shorter?) barrel.

    The .340 is a good balance of performance, weight, and moderate barrel length for a carry rifle. Mine has a Lawton sporter weight barrel with a composite stock and 4 x 12 x 40 Leupold scope. Everything except the MK V action is very light, but the rifle still weighs 9 1/2 lbs, and the 26" tube plus the Holland brake makes it a little longer than ideal for a quick handling carry rifle. Obviously the 250gr Partition isn't intended for long range work, but is a very fine stopper on game. I don't load 300gr Bergers or Sierras in the .340. My opinion is that they are too heavy for it. Conversely, my .338 x .378 shoots lightly loaded 300gr Sierra Mkhp's at 2780 fps, and 200gr Ballistic tips (not lightly loaded) at 3500 fps. It is a fine long range gun, still supersonic at 1700 yds with the 300gr Sierras, but it is too long and heavy to qualify as a carry rifle.

    That's about all I have to say.

    Good hunting, Tom