Saturday, July 18, 2015

300 Win Mag Reloading with Superformance and 175gr Sierra TMK (tipped match king)

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 finally received a box of 175 TMK direct from Sierra and couldn't wait to do some more experimentation in my 300 win mag. I know these were mostly made to be a 308 match bullet but I figured the 300wm might like it just as well.    If you have been following this blog,  I bought a Savage 110 FCP in 300 Win mag and have experimenting to find a good load for this rifle.  I have more than 10lbs of Superformance on hand and have been trying to see if I can come up with a long range load using it.  There is little load data on the Superformance still and I think a lot of people are afraid to experiment with reloading.  I have yet to use magnum primers with the superformance but those experiments will be coming soon as well. For now, i have been using CCI #34 and CCI 200 primers. I switched from the #34 to the 200's because I think the #34s tend to hide the early signs of overpressure.  For example, I was seeing ejector marks before I was seeing primer cratering or flattening. This is because the 34 is a much harder primer designed for Semi-autos. I digress.

After determining my max OAL  for this cartridge which wsa 3.612 (on the lands), I decided to start with some longer bullets and some max "magazine" length loads (the longest load that fits in my magazine.


The following were shot in 5rd groups at 100yds.


These bullets seem to have a lot of potential in the rifle. I only loaded 5rds of each so the data is really only a starting point. One thing I noticed is that really all loads worked well. The speed was consistent and I believe the rifle cooling in between groups is why we didn't see much change between the 74gr load and the 75gr.

I was happy to finally have an accurate load which actually fits in the magazine. These TMKs  have a sufficiently high BC at .545 and I believe I could load these quite a bit hotter. I would actually like to see how these do around 3200fps. According to the Hodgdon Ballistic Calculator at 3200fps we would see a ballistic chart like the following:

The chart doesn't differ much if you input 3100fps as velocity.  At 1500 yards, the velocity is 1128 vs 1164.  I really don't plan on shooting much past 1000 yards with this rifle so really this is quite good.  The next step for me is to load up a bunch and shoot some 10 and 20rd groups to see if this is really the load I want to settle in on.

More to come!

1 comment:

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