The benefits that come from having broken in you bore, vary from manufacturer to manufacturer in terms of how many shots it takes. My original 450b with its chromed chamber and bore didn't settle into its
groove until somewhere around 200 rounds IIRC. Groups tightened up some but it always was easier to clean. I didn't realize the latter fact until I got a second CrMo barrel. The chrome bore, despite what some AR aficionado's claims, was trouble free through 2000 rounds.
The factors which govern the tightness of reload groups are many. Individually, each may only be a small amount, but they stack up to take 1 MOA capable amunition and turn it into to 2 MOA. Wet tumbling your cases removes some of the contributing factors that I used to deal with in post cleaning processing. Most of those small factors are nuance but the crimp is the big ticket. Attention must be paid to having enough without too much but equally important is consistency from round to round. The crimp influence upon group size goes up as the bullet weight goes down.
My rules of thumb are as follows:
Never use the flaring die. Never.
For smooth walled, jacketed bullets, keep the taper crimp at .476. There's no place for the brass wall to go deeper with a smooth walled bullet. You just wind up distorting the bullet into an hour glass shape.
For cannelured bullets like the 200 and 225 FTX, seat them so that most of the cannelure is just below the mouth with a little peeking out and taper crimp down into it with a resultant diameter of .474-.475. That should be measured as close as possible to the mouth using a micrometer. If you can only afford a digital caliper, that will have to do. Consider getting a micrometer. you can find high quality, name brand ones on Ebay for about the cost of a couple of boxes of bullets if you try and it will serve you a long time.
For solid copper bullets with driving bands and their accompanying grooves, seat them similarly so that a groove is mostly below the mouth peeking out. You can easily crimp down into the groove to .474. IMHO, there is no added improvement to accuracy going smaller, even though you can. The sharp shoulders on those grooves provide an excellent gripping opportunity. In the case of really light bullets, a firmer hold will increase velocity but if those really light bullets are smooth sided, its hard to hang onto them enough to get consistent ignition.
If you want factory ammo results, use the same primer as the factory. I have one type of primer that I use. Remington 7 1/2 small rifle primers. When I find something that works well, I don't look any further. The nickel price per primer difference is not going to stop me from reloading.
There is no substitute for testing at the range on a stable bench however. Real world results always trump theory (see sig).
We all have range sessions where the results tell us that we would have been better off doing something else that day. It happens....
Hoot
Posted: Fri Sep 01, 2017 9:40 am