I don't have the 45 but the 50 cal model. I use 100 grain pyro pellets with a 250 gr Shockwave bullet and use a 209 Remington Kleenbore primer with no problems. These guns can use 150 gr as in the manuals but why? I have used more powder and the groups seem to open up. I can hit 1" groups at 100 yds if I do my part using my 3-9-X40 scope. I usually take a lubed patch that is almost dry to the touch and run it down the bore before I load the bullet and it seems to help with velocity and accuracy. It's a great gun as I have 6 of them in various stocks and setups. Good luck shooting.