Wednesday, August 13, 2014

Long Range Shooting Part 0b - The Phase Three Rifle

In my last post about my new project, long range shooting, I detail, in a long winded way, the background, intent and plan I hope to follow as I attempt to teach myself how to shoot long range. For me to consider this project complete I must be able to land 5 out of 10 shots on a 10 inch target from 1000 yards away in less than 20 minutes. I assume that this project will take around 10 years to achieve. In this post, Part 0b, I will be talking about the details I left out of Part 0a regarding the Phase Three rifle build. 

 

The Phase Three Rifle


The Phase Three rifle has is a ton of stuff to consider. Since I WILL be handloading for the target application of this rifle, I might have to look into having things specified such as the throat length and twist rate. I'm also already looking into what caliber to use (likely 7mm-08). I'll give you an example of what I'm concerned about. Let's say I choose 7mm-08 since it has a really good ballistic coefficient. Most factory hunting ammo uses a projectile in the 120 to 140 grain range but the bullets I'm looking at are in the 160 to 180 grain range. I would prefer use the heavier bullet for long range bench rest shooting because they have a higher ballistic coefficient (or BC) than the lower weight rounds. The higher the BC the more resistant to wind effects the bullet has. This means they have a flatter trajectory and since the velocity lost to the friction of the air, the bullet will hit much harder down range. All those things might give me the best possible chance at achieving the Phase Three goal. That said, I AM making a huge assumption in thinking that the lighter weight bullets aren't going to be sufficient for achieving the Phase Three goal.

Let me explain some things. The heavier bullets require a different twist rate compared to the lighter bullets. For example, if I choose the 180 grain Berger VLD Hunting bullet then I would need to have a twist rate of 1:9 to stabilize the bullet, but if I chose the 140 grain Berger VLD Hunting bullet then I would need a twist rate of 1:11. Choosing the twist rate for the heavier bullet could basically ruin any chances of good accuracy if I were to go hunting using ammo with a lighter weight bullet. I would also likely lose the ability to use the rifle's magazine as the handloaded cartridge's overall length (OAL) would be longer than the maximum OAL causing the action to jam. This makes a fast follow up shot almost impossible, should one be needed. The upside to the heavier bullets twist rate would be I would have a very accurate rifle for long range shooting when using the heavier bullets even if every round would have to be loaded one at a time.

I could, however, be over estimating, or underestimating, the effects here. For instance, if I did go with the heavy bullet setup and the distances I'm shooting from while hunting were short in addition to using the light weight bullets when hunting, then I may still have an effective rifle for both purposes if the light weight bullets turned out to still be effective even if they aren't as stable as they could be due to the wrong twist rate. Basically, even though the light weight bullets wouldn't be as stable as they could be, the short distance could basically negate any stability issues that would occur when using the light weight bullets. The alternative could be that if I choose the light weight bullet setup, the 140 grain match bullets may still be effective enough to achieve the 1000 yard goal.

The only reason I'm going through all of this headache is simple. I want a dual purpose rifle. If I was just going to build a 1000 yard bench rest rifle then I would be making a custom rifle using the 6mmBR cartridge or similar. But for some reason, I've got it in my head that I want this rifle to be a target rifle disguised as a higher end hunting rifle or something like that. Also, I don't really want to spend a boat load of money or too much time on this project because I am interested in pursuing other projects. I think I will be posting based on each Phase such as the build's for each as well as progression. We shall see.

No comments:

Post a Comment