Observations of the 300 Whisper
i recently decided to break out a 300 AAC reamer I have had for a while and never used along with a Krieger 8 twist barrel. I initially set the rig up with a 20" barrel. After a couple of trips to the range and some general handling in the back yard, I decided that I didn't like this much barrel with a 9" can attached. I also would occasionally get a downrange crack meaning that the round had gone supersonic. So I set it back up in the lathe and trimmed it to 18" and re-threaded the muzzle. OK, now I like it a bit better. I let a buddy shoot it and the next thing I know he's calling me five times a day to figure out what he needs for an AAC upper for his AR. He asked me to order him some ammo and while tripping around the different suppliers, I discovered that Hornady makes two 300 Whisper loads - a subsonic 208 AMax and a Supersonic 110 VMax. Thinking the Hornady bullets might potentially open up better than the Remington loads with match bullets, I ordered a case of each. It also occurred to me that the 110 might make a decent whitetail load out to 300 yards or so without a can (we can't use cans on game animals in TX) and the 208 would make a nice quite pig slayer with a can.
So last week I took the rig to my 100 yard range and began testing for accuracy and zero. First was the 208 at 50 yards. I set the zero and then shot a group at 100 yards. Measured with my Leupold mil dot, the 100 yard group was exactly 2 mils low from the 50 yard zero. I took a break and pondered how and where I would engage the swine and decided to set the target knobs to a 100 yard zero. Shot a few groups to confirm. Ok, the 208 suppressed rig was ready.
Now to the 110 whitetail setup. I removed the can and put on a thread protector. I had two large targets stacked vertically at 100 yards. I sight on the lowest bullseye on the bottom target and shot a three shot group. It went way up on the top target, which I was expecting. What I wasn't expecting was the complete lack of windage offset after removing the can. Then it gets even better. I bagged the rifle nice and tight and put the crosshairs on my point of aim and twisted the Leupold target knob down until the crosshairs reached the actual group (my standard method for zeroing). I looked up at the knob to see how much elevation was needed and low and behold, it was exactly 15 MOA which is one complete revolution of the Leupold target knob. I was back to zero on the knob, just one revolution down from the 208 zero with the can. PURE DUMB LUCK but I'll take it.
Then out to our hunting camp last weekend. I have a 12" round steel plate set at 150 yards and a 2' x 4' steel with a life size deer painted on it at 350 yards. Saturday morning back at camp after the hunt. I set up on the bench and sent a few 110s at the 150 yard steel. I needed 2 MOA from the 100 yard zero. Conditions were very calm with a 3000' DA. I swing over to the 350 yard target and send a few. I needed 10 MOA but the rounds were going way right. I thought that maybe I had slightly missed a little windage offset on the 150 yard steel since its not a precise target so I dialed the necessary windage for the 350 yard and confirmed with a couple of shots. When I looked at the dial, I was surprised that it was 1.75 MOA of left windage. I knew I hadn't missed the 150 by that much. So I got on my glass and looked for unusual wind. There wasn't any wind to speak of. It was one of those really calm mornings. So I moved back to the 150 and shot one. It went exactly 1.75 MOA left of the last group. Now I'm scratching my head.
It finally came to me. Spinning a 110 grain at 2300 fps out of an 8 twist barrel creates an assload of spin drift. Mystery solved.
I'm going to harvest a doe in the next couple of weeks with the 110s and I'll report on the terminal effects.