Hello All,
I've read a lot of posts dealing with PC boolits and/or barrels with tight throats, but I'm not finding a definitive answer to my questions, so I thought I'd ask here.
First, the background info:
I have an M&P M2.0 9mm Full Size which has become my favorite gun. The barrel slugs at .3565.
I have been powder coating for about a year now, using the shake & bake method with powder I got from Smoke. I'm getting fantastic coverage, and I have no complaints about the PC per se. I have several 9mm molds, but my favorite all around is this 35-125Y from Accurate Molds:
http://www.accuratemolds.com/bullet_...=35-125Y-D.png
As I said above, the barrel slugs at .3565. I have been sizing to .3569, which is as big as I can go and still get the boolit to slip inside the throat and out to the rifling. I have been loading to 1.075 OAL, which I determined by finding the point where the nose touched the rifling and then backing off .010.
I have also pulled the boolits to check for swaging, and there is none. I use NOE expanders, which allow me much more control in this area.
So, the problem is that I've been getting some leading. Not horrible, surface-of-the-moon leading, but definitely some build-up in the angles where the lands and grooves meet. According to everything I've read, I know that I should be sizing my boolits bigger, but if I do that then I would have to load them MUCH shorter because they would hit the tight throat.
I have made up some dummy rounds with boolits sized to .358, and the max OAL I can have is 1.010. I'm not absolutely against doing this, but beyond the fact that it messes with my ability to use published load data, I'm not sure what other effects it might have. Specifically:
1) Will the PC get shaved off when the .358 dia. boolit hits the .357 dia. throat?
2) Will accuracy be affected?
As far as solutions to this problem (if it really is a problem), I can think of two:
1) I could have the throat reamed to accept the .358 boolits, although I have learned that M&P barrels are so hard that a special carbide reamer is required, and many (if not most) gunsmiths do not have such a reamer. I have already discussed this option with DougGuy, but his carbide reamer is shot and he's having a hard time getting another one made.
2) I could buy a different mold that would produce a boolit with a nose profile that would slip inside the throat. Here is one such mold: http://noebulletmolds.com/NV/product...tqi64r3s2n5l95
This might be an improvement, but Question #1 still stands: will the PC get shaved off when the .358 part of the boolit hits the throat?
I'll leave it there for now. I hope I have provided all the pertinent information, but please let me know if I have omitted something.
Thanks!
John