frnkeore
posted this
02 December 2014
Well, to start with, for rifles built for target shooting, square and concentric is to be assumed to start out on even footing to be comparing chambers.
If you don't have a competent gunsmith, your just not going to get anywhere.
For cast bullets, for at least 25 years, to do well you need a gentle leade angle with (IMO) no steeper than 1 deg per side. My 30 cal reamer is 3/4 deg and my 28, 32 and 33's are 1 deg per side. I had my reamer made in 1988 by Hugh Hendricson, based on what I had learned in CBA match shooting at that time. To illustrate what difference it will make, make a fist and plung it into water slowly (shallow angle leade) and then fast (steep angle leade), slowly the water conforms and fast it speads rapidly out, deforming the water. The steeper angle also causes more forward resistance, increasing the chance of deformation over the shallow angle.
All that said, I had a chance to meet and shoot with Mel Harris, this last Stepember (my scores weren't recorded for CBA because I'm not a member), as most CBA guys know, he holds at least 15 current CBA records. We talked about throats and he uses a freebore (didn't ask if it has any taper) and a 1 deg leade. From his results, 1 deg is all that is necessary. I also think that he said he uses a .309 freebore but, I'm not completely sure on that or on the length but, it was in the .100 range.
I will shoot with him again in March (the Roseburg range is 90 some miles from me)and if I'm off on those figures, I'll correct it.
For the BSing experiment, you can get a throating reamer made and increase your freebore to about .190 or so, to take most all of the bands with very little pressure or maybe increase it to take the whole bullet with the GC at the start of the freebore, using just light palm pressure.
Frank