Siringo wrote:Part of my concern with the Barnes 200's is they are so short and .4505 diameter. Consider the free bore that the 450 AR's have (0.10"). I may be wrong, but I don't think BD's bolt gun has the free bore and also he is running a .451 inch barrel. Is this correct? So -- with the AR, the bullet is nearly out of the case just as the center driving band is barely engaging the rifling. IF the case is not perfectly square to the bore -- it would be easy for the gas pressure to cock the bullet to one side or another,since the free bore is around .453" diameter -- plenty of room for a .4505 bullet to bounce around if not securely in the bore. I think this is a problem with most of the short bullets. There are a lot of factors against getting these to shoot well in the Bushmaster barrel.
Siringo-
This post opens a new line of thinking. Thanks (I think). I hope the following comment does not derail the thread.
First, the blanks of the barrels on both my bolt rifles were stated to conform to nominal .45 auto dimensions. However, these dimensions as set by SAAMI have really broad limits. Bore can be 0.442" to .446"'; groove from 0.450" to 0.454". I have not slugged either barrel to find their actual dimensions. I have not seen the SAAMi specs on the 450B barrel for comparison.
(The jacketed bullet diameter for the 45 auto should be between 0.4490" to 0.4520"; for the 450B the Hornady drawing shows 0.4495" to 0.4525".)
Directly addressing the question about freebore in the bolt guns: because the chamber reamer for my guns was ground to 450B specs, the chamber, throat, leade, and any freebore characteristics should be the same as for the ARs.
Because I've been concentrating on velocity, I have not measured bullet-land engagement distances for any of the three bullets I've been using. I'll put it on my list of things to do.
--Bob