dogsniper wrote:I am ramping up to build a 450b Bolt Action myself. Seeing that it HAS been done by at least one member here, I do have some questions. I have located a barrel blank with a 1:20 twist. I see where it is advised to stay away from the 1:16, with the 1:20 be sufficient? Also, I plan on using a Stevens 200 (savage 10) action as I already have one chambered for a 22-250 and the bolt head is the same. This is where the other questions come in. Will I need to modify the magazine follower to feed the rounds correctly? I am hoping Pittbull will have some advice on this since he has pictures of the rifle he already built. Also, if it would make things "easier" I would be willing to use a long action rifle if that will allow the cartridge to free itself from the magazine without binding trying to feed into the barrel. I have already contacted Manson Reamers and that is taken care of...just want to have all of the important stuff covered before I invest a bunch of money only to find out I didn't start with the right stuff! Thanks All!
dogsniper-
Welcome to the forum, and I hope your project goes well. If you've already committed to having Manson grind your reamer, then you are really serious about this and are not just engaging in wishful thinking.
You're approaching the project from the proper perspective of "let's build a 450B bolt rifle". Mine was converted from a couple other projects, and finally emerged as a 450B.
About your questions:
I don't think a 1-turn-in-20-inches barrel will give you any problems with twist rate. The barrels that come with the AR-15 uppers have a 1:24" twist rate, and there have been no reported difficulties with stabilizing some pretty long bullets. Rough calculations indicate your twist rate should be able to stabilize a bullet more than an inch long even at sub-sonic velocities.
You will not have any practical worries about the twist rate being too fast. As reported in the 450B reloading forum, I tried really hard to get a light cheaply-made bullet to self-destruct by spinning it too fast with high velocity. I wasn't successful, and some other forum members thought that a muzzle velocity of 6500 fps would be necessary for a blow up.
I can't make any predictions about ability of a Savage action to feed the 450B rounds, either from a long magazine box or a short one. Here are some disorganized thoughts.
My 1903 Springfield is set up for 30-06 cartridges. I haven't modified it at all. If I want to feed cartridges from the magazine I have to take some care in loading, compared to just stuffing in 06 rounds as in my unmodified Springfield rifles. With 1, 2, or 3 cartridges down, 450B feeding from the mag is successful. The cartridges have to be firmly against the rear of the magazine, and the bolt has to be run forward smartly. Otherwise the rounds will take a dive into the empty space between the noses of the bullets and the front of the magazine. My mag box is made for cartridges more than 50 percent longer than the 450B, so this is to be expected. The mag box could be reconstructed, but if the problem can't be solved with three down plus one in the chamber then another round or two would probably not help.
I cannot try the equivalent of a short box by placing a stack of cartridges at the front of the chamber. The geometry of the magazine spring won't hold a stack of cartridges level when they're place at the front.
Mag box modifications can be pricey if they are done properly, and a smith would have to spend a lot of expensive time with cutting and trying to make things work. I suppose the best way would be to start with rifle that has a magazine made for the 284 round. I don't know if Savage has ever made a rifle for that cartridge.
If your mag box is constructed to be the proper length for a 22-250, you might be all set. The 22-250 cartridge is 2.35 inches long, and the 450B is 2.25. But, you may be correct in thinking that in being pushed out of the magazine, the feeding angle of the thicker 450B might be wrong and cause jams in the short distance available. You might put some 450B cartridges in the mag before you unscrew the 22-250 barrel, and try feeding them with the bolt. They won't go into the chamber of course. However, this exercise might provide some indication of feeding success if the nose of the cartridge goes into the rear of the 22-250 chamber and the alignment of the cartridge body looks like it might work otherwise.
I suspect with the mag box of a long action, you'll be facing problems similar to mine.
Here's a couple of requests:
1) If you have other questions now or as you proceed, you might ask them in this thread. Others may try to do the same thing and will have the same questions and it might save them some time. Don't be bashful about sending me a PM either. I'll do my best to answer.
2) You might take some photos as you go along, and post them here. Again, the object is to help others following along later.
I hope this works out well for you.
--Bob