Friday, July 3, 2015

Experiments with 300 win mag and Superformance - 168gr amax & 155gr SIE HPBT

DISCLAIMER/WARNING FOR NEW RELOADERS:  Any load data in this article is for ONE particular rifle (mine).  If you try this load in your gun, it may not feed and worse, it may feed but blow up your rifle causing injury or death. Be very carefull when extending your Cartridge Length over the reloading book published values as there can be dangerously huge increases in pressure. 

I decided to give the 208gr amax a break for a weekend and try something different. I have a bunch of 30cal bullets on hand which I reload mostly for 308 and 30.06 and thought I would give some a try.  I decided to do some minimal loads and see what velocities I got.

Again because superformance has a similar burn rate to Winchester Supreme 780 and I had load data for that powder (courtesy of Hodgdon Reloading Center) and used the minimum charge as the starting point.

I tried two loads this time out. The first was with Sierra 155 MK HPBT.
I used 75gr of Superformance which according to the load data I had, should generate velocities between 2900 - 3000fps. Again I used PPU brass and CCI #34 primers.  This was the second time reloading these cases and they were neck sized only.

The second load was 168gr Amax with 72gr of Superformance, PPU twice fired brass and CCI#34.

At the range I started with the 155gr first and was completely shocked at how far off my estimates were.

Here is the data.
Shots #1-10
1. 3170
2. 3193
3. 3131
4. 3200
5. 3210
6. 3197
7. 3217
8. 3187
9. 3238
10. 3215

So after firing the first shot, and looking at the Chrony, I thought either I made a huge mistake or the Chrony was broke. I checked the brass and there was no sign of over pressure. I continued on. The group sizes for the first two 5 round groups were .9" and .7".  Now that's what I am talking about!

The next 10 produced a range of velocities between 3177 - 3211. Again great groups under 1".  This was actually a total surprise because I was pretty sure that the 155SMK wasn't really made for that kind of velocity.

Next up was the 168gr AMAX.  Here is the data:

Shots #1-10
1. 3200
2. 3192
3. 3183
4. 3194
5. 3183
6. 3184
7. 3167
8. 3193
9. 3192
10. 3179

Again, wow.. I was expecting to be around 2800FPS but this is crazy. 3200 was way hotter than I expected. Again, the brass looked great, primers were in good shape, no signs of over pressure. The only downer was that the groups sizes were 1.8" - 2".  My rifle hated this load but I may tune it up or down a bit to see if I can get something to group.    I have a box of SMK 175 TMK coming soon so looking forward to putting those down range with superformance as well.  So far in my rifle, this stuff is turning out to be a super powder for 300 win mag (well at least in terms of velocity).

More to come!

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