drgondog
Major
I Read an article in "American Rifleman" about someone who converted a Model 95 or 98 Mauser(I can't remember which) in 7 x 57 into a 284 Winchester. The bolt face of 7X57 and 284 Win is identical so only rechambering is necessary.
True - except the 284 is a rebated case with .500 base instead of .473 - I have run through a LOT of 284 based wildcats (currently have a 25-284 and 6.5-284) and for an action like the short M77 you have one potential problem which is not universal. Namely the little fat case sometimes offers a feed problem from mag. It must be borderline as both of mine are the old M77 short action and I haven't had problems with these two.
The only issue that follows is really more to the 6.5 with the long 140 gr bullet. You have to seat it deeper to get into that short mag. Mine is still very accurate but I wish the mag was ~ .15 longer/
Also read that Fred Huntington who owned RCBS dies had done the same thing. The 284 Win has a case capacity the same as the 3006 or 270 Win but the 284 Win was designed to be used in a short action like a semi auto or lever action rifle and the overall length of the factory load is only 2.8 inches. Consequently some of the case capacity is used up if a long bullet is used. The key to the conversion is to have the chamber deepthroated so the bullet can be seated out further.
You really don't need to do squat with M700/M77 long action (isn't the 7x57 slightly too long for the M77 short action magazine at 3.06 OAL?) but with short action, the limiting factor is magazine length as noted above. If you can't stuff it in the mag, throat length won't matter unless you like single shot only. The throat on my Shilen 6.5 was plenty long enough 'as is' to seat a 6.5-284 as far out as I wanted but my mag well is .3 too short (~3.0 vs 3.3OAL) .
The 284 Win case has a short neck so bullet choice is critical. In other words, if the bullet is seated too far out, the bullet will not be held firmly because the neck is so short. I went to Ed Shilen's shop and asked him if the conversion was feasible and he said, "gosh yes, I have one I have done for myself."
Ren - Out of curiosity - was his shop in Irving at the time? I used to hang around that place just off MacArthur a lot in the 60's and 70's before he relocated south of Terrel.
Called Ruger and talked to the guys at their factory and asked the same question and they said it could be done but why? Typical Yankees who had never hunted in West Texas or Colorado where long shots are the norm. The 7 x 57 is at best a 200-300 yard cartridge. Anyway, I made up a dummy cartridge, using the 140 grain Nosler Partition. The cartridge is 3 and an 8th inches long and the base of the bullet is exactly at the bottom of the neck. Shilen charged me, I seem to remember, 25 dollars to rechamber. I already had a Leupold 2 x 7 fitted and I bought a Canjar trigger and had it fitted. Started working up loads using 4350 powder and like my No 1, the hotter the load, the tighter the groups. The rifle has a 22 inch light barrel and I finally settled on 58 grains of 4350 which is a compressed load and theoretically should give more than 3000 FPS.
Ren - you should be careful with this one even if you aren't getting pressure signs. You using IMR or Hogdon for your .284? Hogdon MAX for a 140 gr (per their manual) is 53.0 grains around 47-48000 CUP. Nosler MAX is 51.5 of IMR 4350 so you have a possibly dangerous load - These loads will give you 86% case loads eliminating the compression chsllenge.
Also you shouldn't ever have a problem with 140 grain as far as the lands are concerned but be careful with 175's
The 284 Win is a very strong case and there are absolutely no signs of excessive pressure. The load chronographed at 3100 FPS and from a rest, it will print min of angle three shot groups. I explain the accuracy because the twist, nine and one half, is ideal for that bullet at that velocity, or more likely the rechambering done by Shilen is perfectly concentric with the bore. Interestingly the down range ballistics are almost identical to my 270 Win load withe 150 grain bullet. Zeroed at 300 yards it is 18 to 20 inches low at 500 yards with more than 1000 pounds of energy at that range. I made a one shot kill(lucky as hell) on a Pronghorn, sitting with a loop sling, downhill, no wind, at 640 paces with witnesses. I estimated it was 500 yards and must have held too high. The rifle and scope with sling and four rounds weighs less than 8 pounds and would be good as a mountain rifle on all North American game, excluding Brown Bear. Wrote the late Finn Aagard describing the rifle and load and he concurred in a nice reply. The big problem with the rifle is that factory loads won't shoot well because of the deep throat and much shooting with those loads would probably erode the throat. I have eight handloads left and gave away all my empty cases and dies and press and all so I am out of business. Oh well.
I love the 284 case. It was the 'short mag' before modern marketing types settled on the name. My 25-284 is just a short action 25-06 but seems to like only 115 Nosler Accubonds and 120 Nosler Partitions and 49 gr IMR4350
I have plenty of empty cases if you need some.
