View Full Version : .357 point of impact question

11-30-2010, 09:47 AM
I have a question for you guys. Is it normal to have a horizontal point of impact difference between jacketed bullets and cast? I understand a vertical difference, but my Ruger GP100 consistently shoots cast bullets approximately 5 to 6 inches to the left of jacketed bullets at about 25-30 yards. I thought it was me at first, but I have done it over and over the last couple weeks. Does it offhand and from a bench. This is the only gun I own that I have noticed this in. Im shooting 158 grain cast and jacketed bullets with 15 grains of H110 pushing the jacketed, and 14 grains of H110 pushing the lead. Thanks

11-30-2010, 10:02 AM
I have experienced shifts in horizontal impact between different loads, but since I don't shoot jacketed bullets, I have no direct comparison like you mention. For me, shifts are more like 2 or 3" at the most between different loads.

MT Gianni
11-30-2010, 10:21 AM
Is there an equal amount of bearing surface on the bullets? That might cause it but I am nowhere near conclusive on the idea.

11-30-2010, 10:38 AM
I have noticed shifts between different styles of cast boolits. Maybe the differences in the shape cause the shift. You have also changed the powder charges.15 gr under the cast might shift it back or may shift it further out. To make a better comparison, you should chrony them to the same velocity.

11-30-2010, 10:51 AM
Are you shooting single action or double action with the revolver? It could be a number of things too little or too much trigger finger, jerking the trigger, try loading two rounds and just go through the motions like you are firing 6 rounds and see if you are getting the same results. The rugers i have shoot a little higher with cast but they don't go left or right on the target. try changing your grip a little higher or lower on the backstrap it might cure it or change stocks if you have a friend that might let you try some different ones it sounds like the revolver is torqueing a little in your hand during firing

11-30-2010, 12:06 PM
You're not alone with this phenomenom...don't know if you would call it a problem. You don't read or hear about it a lot, but years ago Skeeter Skelton remarked on how 357 Magnums seemed to be sensitive to changes in grip or loadings, especially compared to his beloved 44 Specials. Since I am shooting fixed sight Original Size VAQUEROS and BISLEY VAQUEROS in 357, I've tried to concentrate on finding and making "the one good load" for them.

I'm not up on the GP100...does it have rubber grips of some sort...would a solid grip that doesn't flex eliminate the problem.

11-30-2010, 12:16 PM
It is very common and is the way to work loads for fixed sights. Problem is that a load that shoots to the POA is sometimes not accurate.
It is rare to have any number of boolits or bullets shoot to the same place.
Friction, bearing length, velocity in the barrel, powder burn rates, lube, barrel vibration, recoil and barrel rise or torque and maybe a lot more will change things.

11-30-2010, 12:35 PM
Thanks for the replies. I think I will just shoot up the rest of my jacketed bullets, and stick with cast in this gun from now on. Anyone have any experience with shooting deer with .357 158 grain wadcutters? How do they perform?

11-30-2010, 12:51 PM
In my limited experience, left - right is controlled by bullet weight / friction. Up - down is controlled by velocity and ballistic coefficient in flight. I dont have any technical writings to support my theories, but i have worked on around 20 revolvers this way and most have responded to this program.

11-30-2010, 01:01 PM
This is just a guess. If your J-bullet loads are near maximum, your GP-100 may be "torquing" and you without doubt have the sights adjusted to compensate for the torque. With a cast boolit load you are probably not having the same degree of torque, thus point of impact will change. Perhaps as the J-bullet first enters the rifling lead it "bites" solidly into the rifling producing maximum torque while the cast boolit being softer, may "skid" somewhat upon entering the rifling lead, thus cushioning the torque effect. The only way to possibly check to see if skidding is happening would be to collect undamaged, fired projectiles of both types and closely examine the width of the grooves impressed on each by the rifling. If the cast boolit has wider grooves, then it is skidding. Two possible solutions may be to cast your boolits of harder alloy and to use a very firm grip on the GP-100 and to also lock your wrist to lessen the effect of torque. Another suggestion would be to find someone with a machine rest with the proper grip insert for the GP-100 and fire an equal number of each type of projectile. A machine rest should not be affected by torque. LOL

11-30-2010, 01:23 PM
Thanks guys. I love this site becasue everyone is so polite, fast to reply, and provide such detailed explainations. Trifocals, I never thought about why it is hapening like that. Very interesting.

Larry Gibson
11-30-2010, 02:08 PM
Thanks for the replies. I think I will just shoot up the rest of my jacketed bullets, and stick with cast in this gun from now on. Anyone have any experience with shooting deer with .357 158 grain wadcutters? How do they perform?

Years ago when a LEO in NE Oregon I dispatched several deer with some Lyman 458495s cast of the old harder WWs and loaded them to 1200 fps out of a 4" Colt Trooper. The were accurate to 50 yards (never tested them beyond that) and killed deer quicker (I used to time such - from shot to flat on ground) than any other type of solid cast bullet. The only other cast bullets that killed quicker were soft cast GC' HPs at true magnum velocities of 1400+ fps. If ranges are short and you can develop an accurate load that runs 1200 fps i wouldn't hesitate to use them on deer with broadside, slightly quartering to and away and with frontal shots. I don't take Texas heart shots.

Larry Gibson