This is a scale up version of the 25 cal Mos bullet. It will be well stabilized in a 12 twist barrel.

Frank

Been there and done it all I shoot is a 12 twist 28 and it won't stabalize in my rifle. I just finshed cutting four bullet moulds of varying lengths to see just how long / heavy I could get so I know first hand based on real life experiances and not a program. 1.048 in lenght is about ideal CW and with 16-1 it gives you about a 154gr. bullet. 1.058 in length is were it started getting a bit too unstable for the best in accuracy while also sneaking up as close to 1600FPS as I cared to go. There becomes a point when the increased movement of the rifle in the bags by far exceeds any advantages that a small increase in velocity might provide of which it then becomes a real disadvantage. I have a Mos mould that David made for the twelve twists it is 1.032 long and weighs 147grs. with 16-1. Both his and my own design are both spitzers mine being a little more so than his in regards to the nose radius. I could cut you a mould to the length in the drawing but it would really just be a waste of my time and yours now knowing what I have learned first hand or I would indeed  be shooting one if not longer if I could.

JLouis

One also needs to take into consideration the case being used. Before I re-chambered my 28 12 twist to 28-35SS it started out as a 357Max.straight tapered to 28 and left full length. With it I had to push the 1.032 147gr. Mos bullet so hard to try to get it to stabalize that all I ended up with was excesive case pressure. The last match I tried to shoot with it I ended up having to knock out cases with my cleaning rod to be some what competitive. Reaching 1600fps. was also not even close to being doable for me but on the other hand and now using the 25-35 case blown out to 28 it is very doable and it is also amazingly forgiving in regards to the load preference window as well as being extremely accurate. I can now push a bullet as hard as I would care to but like I stated earlier you reach a point where the increased movement of the rifle in the bags out weighs any benefits provided by any increased speed and our bullet weight. I only bring this up to point out that one's choice in case design can indeed be a limiting factor to ones choice in achieving the maximum bullet length for a 12 twist 28 rifle. I also had high hopes of getting to and possibly over 160grs. and the reason for my testing of different lengths but I could not get there being here. In that I mean the density altitude, elevation etc. also comes into play depending on where one lives. All though what did not work for me that being my limitation to maximum length / weight does not mean it might not work out well in thinner and less dense air for others. These are just a couple of the things one also has to take into consideration when reviewing the various twist rate rules. I have always found the Miller to be a good choice and I was quite surprised by the instability with my longest bullet it should have been very stable in the 1550fps. range but in real life it was just not nor was it when I pushed well beyond that point and as hard as I could. As I continued to go up in powder so did my groups in size and just because one can get to or beyond 1600fps. it does not mean your rifle will shoot its very best there. I have found over spinng a bullet is just as damagaing to accuracy as under spinning it. When one finds the right bullet desgin, length and load combination while also being dependant on a multiude of other things is when one's rifle starts to become amazingly accurate as if magical even to ones self.


JLouis