The Lee 340 gr shoots great in my Handi rifle, but not so much in the Encore. The Lee 405 hollow base works ok in both. Size is critical, about 0.002'' over groove dia is best, in my rifles anyway. The Lee tends to run a bit small, so that may be an issue for you. The hollow base may bump up on firing to seal better, I can't really say for sure. I have had NO luck with the Lee 450 grainer. I have some commercial cast 500 gr Postell's that group great, but they push back too hard if you are on a bench.