Ballistics Mystery

B

BSambrook

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I'm a 'newbie' to the group and have a question thats puzzeling me.

I'm reloading ammo for my .357 and here's whats going on with two loads.....

1) .357 Wad Cutter 148 Gn with 3gn's of Titegroup. These rounds are right on the bullseye at 15 yards.

2) .357 Copper Jacket 158 Gn with 5.5 Gns of Titegroup. These rounds land about 6" low at 15 Yards.

Now in my simple mind, the copper jacket rounds while heavier have almost twice the powder as the wad cutters so should be landing in almost the same spot as the wad cutters.

Must be missing somthing here ......

any thoughts will be most appreciated !

Barrie
 

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The heavier loads are getting out of the gun faster before it has time to rise as far in recoil; which begins as soon as the bullet starts to move. Therefore they strike lower.
 
Welcome to the forum.

Usually, with revolvers, heavier bullets impact higher, but that's because, for a similar amount of propellant energy, they take longer to get out of the barrel than lighter bullet do. As Jim described, that lets the muzzle climb a little further before they reach the muzzle and exit. But in this case, with nearly twice the powder energy behind them, the heavier bullets are getting out faster, as the energy difference is much greater than the weight difference.
 
"...so should be landing in almost the same spot..." Nope. There's really no comparison between a 148 WC(usually pure lead) and jacketed 158 grain bullet. However, the felt recoil alone will change your POI. The velocity is a bit over 200 fps different too.
148 WC's are usually used in .38 Special target loads running less than 800 FPS. Titegroup runs a bit faster than that.
Have a look at this.
http://www.bullseyepistol.com/training.htm
 
Bottom line is not to over think this stuff.

What you want to do about it is the question.

Either adjust the sights each time to suit the load and the bullseye or go with whatever group you want on the Bull-eye and just let the other group where it will.

Usually you want your carry load (if its a carry or SD gun) on and the practice ammo falls where it will and you want to know how you are shooting and the group size tells you that.

I shoot a lot of rifle target, I don't care if I hit the point of aiming, I just want to see what any given load (or me) does for the group.

I can adjust the gun onto the point of aim any time I want.

In my case I really don not want as my aim point gets mussed up (nothing worse than a mussed up aim point!) Offset a bit and I maintain the sight picture without a blowing a cluster out of the aim point.
 
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