300 Win Mag Accuracy Testing

I bought a used Browning A-Bolt 300 Winchester magnum (Win Mag) that was built by a US Military Sniper for my personal use on safari in South Africa.  Odds are that this gun will shoot, right?  Well at least better than I can.  So if accuracy is poor, it can't be the gun.

The problem?  I was getting 1.5" - 2" groups at 100 yards, sometimes worse.  The outfitter in SA will have me check the gun upon arrival to ensure that it was not damaged or taken off zero during the flight.  He wants to see 1" maximum groups at 100 yards.  If I can't get that at home, there's no way to expect that in SA.

So I figure it must be the ammo - well that's what I'm hoping, or otherwise it's the operator and I do not want to face that reality.

Upon suggestion from others who have been on safari, I was shooting Hornady's Superformance ammo in 180 grain (the heaviest bullet available is recommended).  This is a great round, as it should be at $75 / box of 20.

Thinking (HOPING) I have an ammo problem, off to Gander Mountain I went.  I spent $175 on four types of ammo from different manufacturers in different bullet weights.  I bought 2 boxes of 180 grain and 2 of 150 grain.

And I also cleaned the gun - although it had less than 30 rounds through it.  Again, can't hurt right?

Off to the range for testing.   I set up 8 targets - 2 for each round.  I planned on shooting 3 rounds at each target to see which was the most accurate.

The first ammo I tested was Winchester's Deer Season in 150 grains.  Not only was this round more pleasant to shoot, it shot VERY WELL.  I think I might have found the problem.  But, this was with a cold gun.

I continued to fire, testing Remington's Core Lokt 150 grain rounds; Winchester Silvertip 180 gr.; and Hornady Superformance 180 gr.  Then I fired them all again in reverse order to test the rounds on a "hot" gun.  And I'll tell you this, the gun barrel was HOT.

I am unsure of the twist rate in the Browning's barrel, but I can attest that it prefers the lighter bullet.  Pictures included below to show the differences...

3-shot group using Winchester's Deer Season 150 grain ammo.  Cold gun.
2 rounds through SAME HOLE.  Distance center to center:  0.36 inches*

3-shot group.  Win Deer Season 150 gr.  Hot gun.
Distance center to center:  0.39 inches*


3-shot group.  Remington Core Lokt 150 gr.  Hot gun.
Distance center to center:  1.4 inches*

* All measurements taken with an electronic digital caliper.

Also, please note, Location on the target is not a concern as I can always adjust the scope to hit center mass.  What's important is that the rounds all impact TOGETHER.  I'll adjust zero later.

The BEST I could get with the 180 grain ammo was 1.75" center to center.  The Hornady's were the worst performers at 2.9".  Again, not slamming the ammo.  I'm just saying that MY GUN prefers something else.

It looks like I will be buying more Winchester Deer Slayer ammo to take with me to South Africa.
Damn right, this gun can shoot!  And thank goodness it wasn't a shooter error!

I guess I'm all out of excuses if I miss now...

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