Just a reminder – in Scotland “large deer” legal (all bigger than a roe deer) load has to be at least a 100gr bullet AND have muzzle velocity of 2,450 fps AND muzzle energy of 1,750 foot pound. As getting s/h barrel in .308 for my Blaser is not happening at the moment, I needed to develop a new 100gr load for my .243 for this red deer season.
Which 100gr bullet?
My .243 Win is a standard 1:10 twist barrel which is not ideal for 100gr projectiles. I read about some standard twist rifles not stabilizing 100gr bullets and did some research before deciding which bullet to go for. As I already have good 87gr load using modern plastic tip design I wanted to go for a typical soft point cheap bullet. I found somewhere on the Internet a formula how ideal twist rate for a given projectile is calculated and contrary to what I read, there was no bullet weight in it. Actually length of the projectile is used in this formula, and although obviously related to weight, there are lots of 100gr bullets with different lengths. I wanted to use the shortest 100gr SP bullet I could easily source. I compared length of most popular 100gr .243 bullets and these is what I found:
|Sierra SP ProHunter||1.041|
|Sierra BTSP Game King||1.078|
|Speer Grand Slam SP||1.040|
|Speer Spitzer BTSP||1.050|
|Nosler Partition Spitzer||1.065|
Sierra ProHunter and Speer Grand Slam were the shortest flat base designs. I could not find Grand Slams in my local gunshops and Sierra ProHunters were readily available and cheaper than anything else.
I had some N140 powder I used in my .308 and .243 87gr loads, but not being ideal for heavier loads I got a pound of N160 powder. Vihtavuori load data is usually quite confusing as they changed loads recently in comparison to data published couple of years ago. I averaged them a bit and started off 39gr and loaded five different loads in 1gr increments. I used my standard CCI 200 large rifle primers and some Norma brass I found lying around.
According to Vihtavuori OAL should be 2.689″ for the two 100gr they listed, but I sat the bullets deeper to 2.670″ OAL (to tip and 3.205″ to ogive using Sinclair hex nut) as it was a bit too close to lands in my rifle.
The results at 100m were quite promising. All loads were safe and I did not see any pressure signs. The best load being 39gr of N160. I do not have a chronograph, but according to Vihtavuori manual the load should easily satisfy legal minimum muzzle velocity and energy requirements.
Now I need to see how it works on roe and red deer. 😆
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