The Accurate Reloading Forums THE ACCURATE RELOADING.COM FORUMS Guns, Politics, Gunsmithing & Reloading Gunsmithing Winchester Model 70 Stainless to 375 RUM?Go | New | Find | Notify | Tools | Reply | |
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Does anyone know what it would take to convert the 375 HH to 375 Rem. Ultra Mag.? Can it be done? Action lenght,feeding,bolt face,what is needed to be done? I am an Alaskan hunter wanting more power with the controlled round feed in stainless.Thanks | ||
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Longshots, Welcome to the forums. It can be done, but it will be a pain in the ass. The bolt face will need to be opened up, you will need an Ultra Mag specific follower and will likely need some expert attention to the feed rails. I believe you would be much better served by having your rifle converted to the 375 Weatherby. That would only require having the barrel set back one or two threads and the chamber opened up with the 375 Weatherby reamer. With a new magazine spring (part #MS from Wisner's) and possibly having your gunsmith mill a few thousandths off the bottom of your follower you can get four down with the 375 WEatherby. lawndart  | |||
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PS, If you really want the 375 RUM, look around on gunbroker or gunsamerica for a stainless Winchester Model 70 in 300 RUM. Then all you need to do is screw on a new barrel and have it chambered. Of course, you'll then need iron sights put on, and will not have four down in the magazine. lawndart | |||
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Well, rim is the same, so you don't need to recut the boltface. But I think it does take some talent to get those to feed. Winchester sells the follower for not much, but the way they set their rails up, with a little step out of them, makes me think it's not a simple widening operation. No doubt a good smith can do it, though. I have to agree that hte 375Wby gives you quite a bump up from the H&H with less work. | |||
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Longshots, Not much really. Some threading back of the barrel and then some judicious bending of the magazine springs. I'm no gunsmith and certainly I'd get the wider RUM box if I was going to use it as a DGR. Feeds fine if not smoothly & mag fits 3 of the fat RUMS. My gunsmith says that the chamber was so generous that he had difficulty getting the reamer to bite in the shoulder area. Would have needed to set barrel back about 1 inch, which he figured I would not want so I have a 375 RUM with a slight Weatherby type radiused (not obvious to my eye anyway)shoulder. If it works I'll post a pic below. The stock is off a 375 Safari express rifle I used as a donor for a custom job.  | |||
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JohnT  o you have any problem using 375 RUM loading dies, or do you just shoot factory ammo? | |||
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JohnT: I just saw your picture after I posted about the dies. The rifle looks excellent,you should be proud! If you do reload,I am interested in your favorite loads. | |||
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If you feel you need more power than the 375 H&H go to a bigger cailber...like a 416... More velocity ain't the answer for consistent better stopping...as a matter of fact as velocity increases so does erratic bullet performance Mike Never under estimate the internet community's ability to reply to your post with their personal rant about their tangentially related, single occurrence issue.  What I have learned on AR, since 2001: 1. The proper answer to: Where is the best place in town to get a steak dinner? is…You should go to Mel's Diner and get the fried chicken. 2. Big game animals can tell the difference between .015 of an inch in diameter, 15 grains of bullet weight, and 150 fps. 3. There is a difference in the performance of two identical projectiles launched at the same velocity if they came from different cartridges. 4. While a double rifle is the perfect DGR, every 375HH bolt gun needs to be modified to carry at least 5 down. 5. While a floor plate and detachable box magazine both use a mechanical latch, only the floor plate latch is reliable. Disregard the fact that every modern military rifle uses a detachable box magazine. 6. The Remington 700 is unreliable regardless of the fact it is the basis of the USMC M40 sniper rifle for 40+ years with no changes to the receiver or extractor and is the choice of more military and law enforcement sniper units than any other rifle. 7. PF actions are not suitable for a DGR and it is irrelevant that the M1, M14, M16, & AK47 which were designed for hunting men that can shoot back are all PF actions. 8. 95 deg F in Africa is different than 95 deg F in TX or CA and that is why you must worry about ammunition temperature in Africa (even though most safaris take place in winter) but not in TX or in CA. 9. The size of a ding in a gun's finish doesn't matter, what matters is whether it’s a safe ding or not. 10. 1 in a row is a trend, 2 in a row is statistically significant, and 3 in a row is an irrefutable fact. 11. Never buy a WSM or RCM cartridge for a safari rifle or your go to rifle in the USA because if they lose your ammo you can't find replacement ammo but don't worry 280 Rem, 338-06, 35 Whelen, and all Weatherby cartridges abound in Africa and back country stores. 12. A well hit animal can run 75 yds. in the open and suddenly drop with no initial blood trail, but the one I shot from 200 yds. away that ran 10 yds. and disappeared into a thicket and was not found was lost because the bullet penciled thru. I am 100% certain of this even though I have no physical evidence. 13. A 300 Win Mag is a 500 yard elk cartridge but a 308 Win is not a 300 yard elk cartridge even though the same bullet is travelling at the same velocity at those respective distances. | |||
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Longshots, Thanks, it doesn't look too bad for a parts bin special. No problem at all reloading for the RUM. I use the Redding 3 die set & they are excellent. For Priming I use the Lee hand primer and the only hassle is that you need to grind the opening down to fit the fat cases - the case fits the shellholder just fine. Don't know when Lee will wake up & do something about that. MTM loading block fits but only just, use a Frankford Arsenal powder funnel with all those plug in spouts. Std funnels don't fit. Minor stuff. Have not done a lot of load development with my scope problems & limited range time. Believe me its not one of my favourite things shooting bits of paper with a 375RUM - 40 shots= 1 big ouch. Have concentrated on 2 powders AR2213SC (H4831SC) and AR 2217 (H1000). I have only fired the H1000 rounds - starting at 95gr - low velocity (intentional) only 2400 but terrible recoil & blast. Groups about 2 inch for 3 shots. The Rem ammo with 270gr Hornadies was spot on velocity wise 2920fps - 2 shots touching then a flyer. Do a search for posts by "RIP" he's reloaded a bit more for it plus reports excellent accuracy from the REM factory 300gr A Frame load. I think the 375 RUM gives excellent reloading flexibility. Easily duplicate 375H&H vel while coasting at lower pressures. I am currently shooting 300gr Woodleighs but have some Barnes X's stowed away for this beast. That's when I think a RUM comes into its own doing 2700fps (Saeeds preferred velocity) with a long monometal bullet. I think the H&H will be redlining at those figures whilst we can do it easy. Bottom line its fun to get into & it does not cost the earth to try - so why not have a go eh?? Also if you look at the Nosler Manual (No. 5 I think) you will see a note that they now use the RUM for all their 375 testing as they consider it more accurate than the H&H. But then they use a machine rest don't they-no ouches. Believe me the recoil is substantially more than a H&H but then maybe I'm just a wimp. Good luck with your project. I guarantee you that when you pull the trigger for the first time at your local range that you will be the centre of attention. Just mark my words! Welcome to the Club. New members always welcome. Regards JohnT | |||
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JohnT: Thanks for all of the help.It's time to find a gunsmith.Before posting here,I called a few with no luck .They weren't interested, and tried to talk me out of the project.Sounds fun, Thanks again. | |||
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longshots - go to www.rifleactions.com and send a message to Dave - he was the gunsmith at chimo guns in Wasilla and moved to Washington state - he did this conversion on a friends model 70 and it worked out extremely well - KMule Hear and forget. See and remember. Do and understand. | |||
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KMuleinAK: Thanks for helping me find Dave Caboth.I had heard of him, but I could not find him.I tried searches on the internet with no luck. Thanks | |||
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I had considered the same conversion pretty hard , but in the end went with the .375 Weatherby option . The thing that turned me was a post by Bill Leeper on this board where he found that the WSM chambers in the M-70 tended to end up out of round becaude of the barrel and thread diameters in the Winchester. This concern should carry over to the RUM s because the case diameter is about the same as a WSM . The Weatherby is a very easy conversion that should work nicely with your original magazine . It gives ya more than enough thump , and like the RUM , quite a bit of loading flexibilty . In addition ,you can fireform the cheap and plentiful H&H cases and use H&H ammo in a pinch.........it's really a nice .375 bore cartridge.... | |||
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Winchester Part Number U353071480 300 Ultra Magnum Magazine (1480) $15.00 | |||
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sdgunsliger, That's what my gunsmith told me. Well actually the 375 Ackley Imp. But I didn'think the H&H needed improving, I just wanted a different 375. I already had another 2 x 375 H&H's. If you start off with a 375 H&H chamber I don't think there is any issue with "out of round" chambers since it should all clean up going to 375RUM. Anyway to each his own. I would have thought 375 RUM brass in USA would be a lot cheaper than the Norma 375 Wea too. Regards JohnT | |||
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JohnT who did the gunsmithing on your 375 RUM. Mark | |||
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sdgunlsinger, Lookls like Bill Leeper was right. A mate of has a 223 WSSM Coyote and the barrel thread is larger than the normal 1 " M70. I suppose all M70s will become the same barrel threas size. Mike | |||
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John From Leeper's info , it isn't the re-chambering that creates the out of round problems . Apparently what he saw is that chambering to a WSM left so little "meat" in the threaded barrel shank , it would spring out of round when screwed into the M-70 action . Too bad that post was on the old board , it was quite interesting but I suppose it's now impossible to dig it up . If as Mike says , Winchester has now gone to larger barrel shank with these fat cartridges , it would tend to confirm Leeper's observations. | |||
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sdgunslinger All the old posts are still available. Use the "Find" then the advanced search function. I just did so and brought up a bunch of Bill's posts but couldn't find the exact one you're referring to. With a little more time and patience I'm sure you could find it - then you can post the link for us all! | |||
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Mark Smith, Sorry Mark the guy has retired now due to ilness. Pity cause he is super talented and a real nice guy to boot. Regards JohnT | |||
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sdgunslinger, Thanks for the link. Now I can re-read that post. It was an interesting one, as are most that Bill writes. | |||
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I originally wanted to convert a stainless Mod. 70 375HH to 375 Rum. I still haven't found a gunsmith that thinks this is a good idea. What do you think of using a CZ 550 action,weath.erproofing it,and using a stainless barrel?Do you think I could use a CZ action that has been used already for a 375HH.Would the feed rails be able to be worked to feed 375RUM? | |||
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The cz action would be very good for the RUM and well with the size of the cz action you may as well go the whole hog and get a .378 weatherby !! All class  | |||
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Could the CZ 550 action taken out of a 375hh still work for the 378 Wea. ?Bolt face? Feed rails? Mag. Box? Could the barrel be rechambered? Thanks | |||
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Longshots There is a poster on the forum by the name of RIP who has a CZ 375 H&H converted to 378 Wby. He could give you the details Mike | |||
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Mike375: I invited RIP to a private exchange.I have never done that before and I can't even find my message to him?? | |||
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Yeah, I always have trouble with that thing. If you send a PM is starts of a thread but he needs his "Notifications" turned on and then he receives an email and he can open it from there. Just address a thread to him on Big Bores an he will be more than happy to elaborate. His is a rechamber of 375 not a rebarrel of a 416 Rigby. Mike | |||
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Mike375: Thanks alot. | |||
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Or post to him on this thread he has going on Big Bores about 375/338 Lapua https://forums.accuratereloading.com/eve/forums/a/tpc/f/4711043/m/560108902 | |||
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Hello longshots, The CZ 550 Magnum in .375 H&H makes a good rechamber to .378 Weatherby. No problems. A little feed work and rechamber, open bolt face, glass bed and cross bolt the stock or use a McMillan. Great rifle. Mine is MOA with 300 grainers at 2900 fps easily from the 25" CZ barrel. 3000 fps would be no problem. The .375 Weatherby cleans up the .375 H&H chamber of a Win M70 perfectly. No feeding issues. I did this with a stainless M70 Classic .375. The .375 RUM has a slightly longer neck than the .375 H&H, so you would have to rebarrel or set the threads back/whack off the threads and rethread the barrel, etc. Therefore, you cannot simply rechamber an M70 from .375 H&H to .375 RUM. A Rum box and follower and some feed/rail work would also be needed, as mentioned above. I did rebarrel a CZ 550 to .375 RUM and got it feeding properly with some work. The slightly rebated rim is a no-good thing. It does 2780 fps from a 23" barrel and a no-freebore throat. The 26" Remington factory .375 RUM M700 LSS gets just barely over 2800 fps with the same factory load (300 grain Swift). The .375 Weatherby is most sensible, and it will do 2800 fps with 300 grainers (Nosler Wby factory loads) from a 26" barrel, and 2740 from a 24" barrel, so even the 24" barrel delivers 5000 ft.lbs. of KE. Many options here. But I gotta try one more: .375 Lapua. | |||
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RIP: Thanks for the reply.I started a new thread on Big Bores after talking with Mike375.I think I will leave it there in case anyone has anything else to add. Thanks again Longshots | |||
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I have buildt a 338 RUM on a stainless M70 action. No problem! Mine was originally a 338 win mag. All I did was to rebarrel it with a Shilen SM-barrel, and removed the clip in the magazine, and changed the bolt-stop. I guess you dont have to do this things because you already use the whole lenght for the 375HH. But for the 375RUM I'll use a lot of crossbolts in the stock. My magazine holds 3 rounds, but I have to use one of them in the chamber. So 1+2 is more correct. Maybe I'll check out that 300 RUM magazine myself? *Treat problems like a dog; Take a sniff ..... If it can't be killed, eaten, or fucked? Just pie on it, and walk on!:-) Arild. | |||
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