40/65 shooting groups at 200 yards

[michael m]

my usual results thus far is a group that is 2" high and 4" wide.

I shoot 4198 and a 300 gr rcbs, plus dacron filler in an c. sharps 75.

What do you think I need to do to get a 2" x 2" group?

why the horizontal dispersion?

[Ballistics in Scotland]

As a very rough guide, dispersion of shots in all directions equally is the cartridge, and dispersion in one direction is the rifle or the sighting. I'd be inclined to suspect the bedding, sights that allow sideways moving, sling tension if you use a shooting sling, or sights like a blade and notch which you can line up better vertically than horizontally. With a .40-65 as usually loaded, 2n. sounds like the loads are fine.

[Litl Red 3991]

You don't mention what velocity you're getting with that bullet and powder.

There is a somewhat complex theory about the affect on windage accuracy and the speed of sound. It has to do with ballistic coefficient and such and would take a page or two to cover adequately enough to cut down on misunderstood responses blasting it as BS. Cutting to the chase... Testing it proved to me the strong possibility it is right. At least for my 40-65 and 40-70SS and those 300RCBS bullets. With loads that exceed Mach both calibers have shown to be more vulnerable to significant wind doping. In other words, the faster loads require me to get my windage right or the L-R dispersion is greater than the vertical.

To prove it you need to be sure of your own performance on the trigger AND actually know what the wind is doing WHEN you've actually got wind. Don't have wind flags out? Don't know your actual velocities for sure? Darn Then Scotland has covered the rifle/shooter part, and the other is the conditions part. And no way to know if either (or a few not mentioned yet) is the reason.

Good thing about marksmanship is... it always gives you another reason to go test something more.

[Litl Red 3991]

BTW, have you chronographed those filler loads yet? The reason I ask, is awhile back I setup my chronograph at a Buffalo match after it was over and a bunch of guys got a chance to find out what their loads were actually doing. Eye opening for sure...

Chronographs tell you a lot more than just average velocity. And quite a few of the smokeless loads gave pretty lousy deviations. One shooter happened to have one load with and without filler. Not enough to actually prove anything but the fact the filler load gave awful deviation woke him up. We got together again to run more testing (see how that works out to go shooting more?) and same results. Some things everybody knows aren't always true. That's often true because everybody usually thinks basic truisms are one line sound bytes. And shooting is nowhere close to that simple.

BTW, turns out about half the guys who took advantage of the chrono after the match owned chronos themselves. And didn't know even their average velocity, much less the spread etc. Tells ya' something, don't it.

[fa38]

When I was shooting my 40-65 at gong matches my rifle preformed best with the Lyman Snover bullet which weighed 415.0 grains. I was shooting about 19 grains of IMR SR 4959 and WLR primers.
I tried the RCBS 300, 350, and the 400 grain bullets. They all came out of the molds at about 15 grains more that the stated weight.
As I went down in bullet weight the accuracy went down also. i.e. the 300 grain RCBS was least accurate, Not real bad but the heavier bullets were better.

[Tatume]

Litl Red is correct, horizontal dispersion is often caused by wind.

[Shiloh]

A friend has a replica rolling block in 40/65 caliber. Very accurate. I can't see well enough anymore, but can hot a gong at 200 or 225 almost every time. He shoots it and keeps rounds in the 1o ring with some straying into the 9.

Shiloh

[Blackwater]

At 200 yds., and with the bullet and velocity you're shooting, it's most likely the wind. Lighter, shorter bullets are more wind sensitive, and the wind blows them more easily and further than longer, heavier bullets. Long range shooters have always gravitated toward the longest, heaviest bullets their guns will shoot, and it's because of the wind drift at any significant distance. If you have a ballistic program, run a few test projections, and see what you get with your appx. BC and velocity at 200, and you'll likely find that you were really pretty lucky the wind was mild on the day you were shooting.

I once had a buddy shoot a very small group at 600 yds., with a single flier out by 4" from the center of the group. When I got home, I ran a projection on the Sierra CD I have, and it showed that just less than a 1 mph. wind could blow the bullet he was using 4" at that distance. With your slower, lower BC bullet, 2" of drift at 200 really isn't bad.

The more long distance shooting you do, the more you'll come to respect the wind. That's darn good shooting, though, so you're well set to learn to shoot in the wind. Only accurate shooting will or can reveal these things to you, and you're in the short rows now, with that down pretty well pat. Good shooting!

[gwpercle]

At 200 yards wind plays a big part on those 40-65 loads. Most of the shooters at that distance prefer heavy 45 cal. boolits just for bucking the wind better.
4 inch X 2 inch groups are darn good, paying close attention to wind flags and timing your shots so there is little or no wind might just do the trick. If you are not already doing this.
Gary