Unfortunately, there is no support for 300MP in the current release of QuickLoad, so determining a starting point was a matter of translating load data, which does exist for the 460 S&W to our 450b. They are very similar calibers. Not identical, but close enough to serve as a starting reference. Alliant does have a recommended load for the 460 S&W pushing the 300gr Gold Dot. Given the slightly higher case capacity of the 460 S&W, I took that load and interpolated it downward to a starting load of 36gr.
Since I only had 18 pulled Gold Dots to work with, I went with 3-shot strings ranging from 36 to 41gr. I had already determined that a 450b case would hold 42gr of 300MP uncompressed to come close to the base of a 300 GD seated to where the cannelure is almost buried in the mouth (2.06 COL). I wanted to utilize the native taper crimp die that comes with the Hornady 450b set, since not many members have the modified Lee FCD die, which has been chronicled elsewhere. There is more to be accomplished both with higher charges of 300MP, different seating depths and different crimping techniques.
Here's the resulting performance that should serve as a characterization of 300MP for future efforts. One note though. Since I was forced to use pulled down bullets, with resulting reduction in diameter from having been once seated in cases already, I elected to use a more aggressive taper crimp of .474 into the cannelure as measured at the very lip of the mouth. Had these been new bullets, I would have used .475 into the cannelure.
The resulting groups, which were not the thrust of this range visit show typical results I obtained with Gold Dots last year. I get better groups using the similar 300gr Hornady XTP Mag. Natchez has them in stock at the moment for around $17.88/box.
The heavier the projectile, the greater the vertical change in POI as a result of change in velocity. I had originally sighted in my load workup scope using the standard 250gr FTX over 38gr of Lil Gun and the 300s dropped substantially as you can see in the first (36gr) target. I adjusted the scope for the subsequent targets, but you can see the groups climb as I increase the velocity by as little as 50-75fps. The lighter, higher BC, bullets I normally frequent do not respond so radically to variations in velocity.
Much like other bullet weights in this barrel, there is a tendency for the groups to tighten up as the velocity and resulting RPMs increase. That is also more pronounced with the heavier bullets. As you can see, the groups are just starting to tighten up as the velocity goes above 2000 fps. These 300 Gold Dots scream for more velocity. You're all probably getting tired of reading this, but I have little to no interest in bullets above 275gr. There is more to be learned from using 300MP with the heavier bullets, but I'm loathe to spend money on more 300 grainers. Some times I pursue weights outside my interest zone just for the sake of buying some education. I may pick up some more 300s to continue where I left off, as it is always interesting to ply the waters of a new powder and to justify having bought a whole pound of it.
-To be continued-
Hoot
ETA: The 35 gr load data came from foulers, so there's no group picture
