300 Win Mag with 208gr Amax & Superformance powder. Session Two

I put a cheek rest on my rifle this week as I felt that maybe some of the accuracy issues were related to my cheek weld and some sort of paralax effect. My scope has a paralax adjustment and it was set correctly so I am pretty sure it wasn't the problem but the cheek rest is nice anyhow.

I got one from Matthews Fabrication (http://matthewsfabrication.com/product/adjustable-kydex-cheek-rest-matthews-sleek-rest/) for around $40.  It took about 10 minutes to install and works really well.  You may notice in this picture that the muzzle brake is missing. More on that later!

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. 

From my last range session, I determined that I wanted to try a bigger batch of loads using 70gr of Superformance Powder.  This should yield velocity at around 2800FPS with the 208gr AMAX. This is good enough for 1000 yards and more.

I arrived at the range early in the morning (8am is early for me) and the weather was perfect at 80 degrees no wind.  This was to be a hot day so I wanted to get my shooting done early.  

I ran my first 5 shots over the chrony and here are the readings:

1. 2754 fps  (cold bore)

2. 2827 fps

3. 2816 fps

4. 2803 fps

5. 2818 fps

Almost exactly where I wanted to be.  I was a bit surprised on the huge jump between the cold bore shot and all the others.  The first group was around 1.5" which is much better than before but still not where I want to be.  There was no flattening, cratering or signs of over-pressure otherwise.  This seemed like a viable load if only it groups a bit better. 

My next 5 shots were as follows:

6.  2806

7.  2803

8.  2842

9.  2846

10. 2814

I had a cluster of 3 together at about 1/2 inch and then 2 right on top of each other about 1" away for a total 5 shot group of about 2in.  Not great but interesting as the rounds matched up with the velocities almost exactly.  shots 8 & 9 were the two that were together. I am going to play around with this load a bit more in the future and be more precise. These loads were sort of slapped together. 

At this point, I took off the muzzle break as I wondered how it might affect the accuracy and speed of this load.  The next 10 shots were much more consistent in velocity but not any more accurate. 

Shots 11-20 ranged between 2809 - 2817 and were very consistent however I was still not able to produce better than 1.5" groups at 100 yards.  Its still a new barrel so I probably need to give it more time and a good proper cleaning. More to report later!  All I know is that the muzzle brake is your shoulders best friend. 

Reloading 300 Win Mag with Hornady 208gr AMAX and SUPERFORMANCE Powder

Ok, so many reloaders will tell you to stick to the book if you don't want to blow yourself up.  I don't want to blow myself up, but I always question everything.  About a year ago, I bought 10lbs or more of Superformance powder. I wanted to try it out for 308, 243 and 30.06.  It didn't seem to give me any great boost over what I was already using (except the 30.06 but accuracy was crap) so I put it away.  I was looking through the load data I had for 300wm and realized that I would probably have to buy some more h1000 or Retumbo to load for this round.  After spending about an hour on the internet looking for these powders in stock, I decided to see if something I had could work.

Varget seemed like it might work for the lighter bullets but definitely too fast for the 208gr.  It was then that I decided to look up the burn rates for superformance and was pleasantly surprised to find out it was right in between Winchester Surpreme 780 and H4831.  These powders also were sort of middle-of-the-range in the Hodgdon Reloading Center so I thought I would give it a try.  According to the data I found, Supreme 780 was the same or slightly faster burn rate than Superformance. I decided to start at the bottom of the range and load 5rds for each 1 grain increase.   I started at 67gr and ended at 73 grains.  I went with the Hodgdon COL which was 3.420" .

Regarding primers, I only had 20 mag primers left so decided to bench them and use CCI #34 for now. I had many others in my stock but those were already loaded up in my priming tool from my last 308 session and I am lazy.

Back at the range, I setup my Chrony which is a Beta Master and prepared to blow up my rifle with this undocumented load.

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. 

300 Win Mag, 208gr Hornady Amax, PPU once fired neck sized brass with CCI #34 primer. COL 3.420

Superformance:
67gr :  STD = 14,  Average 2734FPS,   LOW=2720FPS, HIGH = 2753FPS

68gr :  STD = 11,  Average 2766FPS,   LOW=2750FPS, HIGH = 2780FPS

69gr :  STD = 15,  Average 2813FPS,   LOW=2790FPS, HIGH = 2834FPS

70gr :  STD = 2,  Average 2836FPS,   LOW=2834FPS, HIGH = 2838FPS

71gr :  STD = 7,  Average 2917FPS,   LOW=2910FPS, HIGH = 2929FPS

72gr :  STD = 10,  Average 2973FPS,   LOW=2955FPS, HIGH = 2973FPS

73gr :  STD = ND,  Average ND,   LOW=ND, HIGH = ND


Things started of great! I was surprised that my starting point was pushing those big pills at over 2700.  My target velocity was 2800 so I wouldn't have far to go.  There was absolutely no signs of over pressure whatsoever. Accuracy was not great however.  She was grouping around 2" @ 100 yards. I was taking about 5 minutes between each set of 5. I probably got the barrel hotter than I should have as I was in a bit of a hurry towards the end.

I started to see signs of pressure at 72gr.  The primers were starting to flatten just a bit and you could see the faint markings of the ejector on the brass face. Still no bulging, cratering or sticky bolt so I thought I would press on. The gun was very hot at this point and I felt if I let it cool down, I might be way over pressure for the 73gr load.  At this point I believe something went wrong with my chrony as I couldn't get a reading on the next 5.  My guess is that they would have been around 3000fps but this was hotter than I wanted or needed.  Still no sticky bolt or popped primers and cases looked fine. Just a bit of flattening on the primers and light ejector marks.

I had gotten the data I needed and headed home to clean the gun and inspect the cases & primers more closely before reloading them.  Based on the data, I think I am going to try a bigger batch of the 70gr load. Still not sure what these would do with magnum primers but at this point, I really don't need them!