Have you ever worked up a load for a rifle but a year later discovered that the load doesn't shoot worth a damn any more?! In the spring of last year I bought a Kimber 84M Montana in .308 Win for my girlfriend so that she would have a good, lightweight hunting rifle. In October of last year I worked up a 165gr Barnes TTSX load that I thought was "the one" using Lapua brass, Varget powder, and Federal GM210M primers. My gf shot and killed an injured deer last year with the load/rifle at 100 yards or so and all was good, or so I thought.
https://www.thehighroad.org/index.p...unting-load-development.812161/#post-10394219
So fast forward to a couple of weeks ago and my gf asks me if there's any ammo for her Kimber since she plans on going hunting this weekend and wants to make sure that she's ready. There were 15 or so rounds left from last year so she shoots a 5-shot group that didn't look much better than 3" at 100 yards. I jokingly tell her that she needs to practice more and then I shoot a group to show her how it's done. My group is only marginally better and this is from a load that put five shots into 0.624 moa a year earlier (see link above)! Now I'm scratching my head since the only thing I did to the rifle since last year was open up the barrel channel .020" to .030" on the right side near the end of the stock. Anyway, I had a couple of weeks to figure it out so not a big deal right? If only that were the case.
For the last couple of weeks I've been rushing home during lunch to shoot various loads using the Barnes 165gr TTSX and 150gr TTSX bullets, Varget powder, Federal GM210M primers and new Lapua and Winchester cases. To complicate things we've had a lot of snow recently with temperatures in the mid 20s to mid 40s. As of yesterday afternoon I still hadn't found a good load with either bullet and my gf was leaving around 10:30am today. In a last ditch effort I decided to clean the rifle and shoot some Hornady Superperformance 150gr SST factory ammunition at 9:00am this morning in the hope that it would perform well enough for her to use while hunting. It was snowing and 22F when I went out to the bench in my garage and the resulting 5-shot group is shown below (average velocity was a very respectable 2,997 fps). After shooting a group I reinstalled the cheek pad on the rifle and had my gf shoot a group which was similar but she had one round way off to the right that she put down to her error and not being ready. I adjusted the scope based on her 4-shot group dialing 1" right and off she went on her hunting trip. Hornady saved the day!!
This saga has me digging deeper into bullet length, gyroscopic and dynamic stability, barrel twist rates, air temperature etc. It's been a lot colder earlier this year than last year so temperature may be part of the problem along with both the 165gr TTSX and 150gr TTSX bullets being marginally stable (or possibly unstable) in a 1:12 twist barrel. Those copper bullets are long for their weight. Once hunting season is over I want to figure out what the issue is with the TTSX bullets but on the bright side she has four boxes of a factory load that shoot very well ... for now at least ... and we probably wouldn't have figured that out if the original handload had continued to shoot well.
https://www.thehighroad.org/index.p...unting-load-development.812161/#post-10394219
So fast forward to a couple of weeks ago and my gf asks me if there's any ammo for her Kimber since she plans on going hunting this weekend and wants to make sure that she's ready. There were 15 or so rounds left from last year so she shoots a 5-shot group that didn't look much better than 3" at 100 yards. I jokingly tell her that she needs to practice more and then I shoot a group to show her how it's done. My group is only marginally better and this is from a load that put five shots into 0.624 moa a year earlier (see link above)! Now I'm scratching my head since the only thing I did to the rifle since last year was open up the barrel channel .020" to .030" on the right side near the end of the stock. Anyway, I had a couple of weeks to figure it out so not a big deal right? If only that were the case.
For the last couple of weeks I've been rushing home during lunch to shoot various loads using the Barnes 165gr TTSX and 150gr TTSX bullets, Varget powder, Federal GM210M primers and new Lapua and Winchester cases. To complicate things we've had a lot of snow recently with temperatures in the mid 20s to mid 40s. As of yesterday afternoon I still hadn't found a good load with either bullet and my gf was leaving around 10:30am today. In a last ditch effort I decided to clean the rifle and shoot some Hornady Superperformance 150gr SST factory ammunition at 9:00am this morning in the hope that it would perform well enough for her to use while hunting. It was snowing and 22F when I went out to the bench in my garage and the resulting 5-shot group is shown below (average velocity was a very respectable 2,997 fps). After shooting a group I reinstalled the cheek pad on the rifle and had my gf shoot a group which was similar but she had one round way off to the right that she put down to her error and not being ready. I adjusted the scope based on her 4-shot group dialing 1" right and off she went on her hunting trip. Hornady saved the day!!
This saga has me digging deeper into bullet length, gyroscopic and dynamic stability, barrel twist rates, air temperature etc. It's been a lot colder earlier this year than last year so temperature may be part of the problem along with both the 165gr TTSX and 150gr TTSX bullets being marginally stable (or possibly unstable) in a 1:12 twist barrel. Those copper bullets are long for their weight. Once hunting season is over I want to figure out what the issue is with the TTSX bullets but on the bright side she has four boxes of a factory load that shoot very well ... for now at least ... and we probably wouldn't have figured that out if the original handload had continued to shoot well.
