One shot pops high

C

Charles E

curmudgeon
Throughout much of my shooting life, I've been plagued with shots popping out out the group high. This isn't really "vertical stringing," the group, aside from the errant shot, is good. I have read and re-read Speedy's tips on vertical stringing.

Multiple ranges, though some are noted for letting a shot pop high. Multiple actions -- BAT, Panda, Viper. Multiple barrels. I think multiple rests/bags, though that's harder on an aging memory.

Let's also assume I can (1) develop a good load, and (2) weigh or throw powder accurately. Tried both, long range and short.

Let's NOT assume I've payed attention to always having great ignition -- choosing an action specifically for striker energy, or replacing springs, or using anything but Federal Match primers. (Grasping at straws, I imagine, though ignition issues are maybe too often overlooked in CF benchrest)

What it really sounds like though, is a bad habit, bad technique. I do shoot free-recoil, but realize saying that isn't very descriptive.

Any thoughts?
 
Charles, one shot high is a common problem with us short-range group shooters. Mike Ratigan, in his book "Extreme Rifle Accuracy" goes into this scenario and says it happens to everyone; especially on the first shot on the record target. Mike even says, "There are those who have this problem and know it and those that have the problem and do not know it but everyone has the problem."

For years, I searched for the cause and solution to this situation and think I may have stumbled on the answer. :)

In the tunnel, we do quite a bit of dry firing to test both the rest and bags and also the shooter's rifle handling. I remember one particular time in which we could not stop the shift in point of aim when the striker fell. The problem went away completely when we placed a used dryer sheet under the buttstock. I think what was happening was we had quite a bit of "sticktion" in the bags and a bit of energy was being stored as the rifle came to rest in the bags between shots. This little bit of sticktion/energy was being released the instant the striker fell.

I have found it is okay to have a good bit of drag at the front bag as long as the rear bag does not stick to the buttstock. Lots of things can be used at the rear bag; used dryer sheets, powder, boron nitrate, silicon spray, etc.

Try this and see if it doesn't solve your problem. ;) Let us know the results. :)

Gene Beggs
 
Gene - primer state?

Gene, what is the state of the primer when you do these tests, fired, unfired but deactivated, or an actual live one in an empty case? thanks... Scott
 
Woody said:
Gene, what is the state of the primer when you do these tests, fired, unfired but deactivated, or an actual live one in an empty case? thanks... Scott
Click to expand...



Scott, we chamber a fired case with primer left in place and click on it only once. If we are going to do extended dry firing, we remove the firing pin and slip a small o-ring over it and reassemble the bolt. This cushions the firing pin fall slightly and prevents any possible damage. (But don't forget to remove it! :eek:)

Gene Beggs
 
Gene Beggs said:
In the tunnel, we do quite a bit of dry firing to test both the rest and bags and also the shooter's rifle handling. I remember one particular time in which we could not stop the shift in point of aim when the striker fell. The problem went away completely when we placed a used dryer sheet under the buttstock. I think what was happening was we had quite a bit of "sticktion" in the bags and a bit of energy was being stored as the rifle came to rest in the bags between shots. This little bit of sticktion/energy was being released the instant the striker fell.

I have found it is okay to have a good bit of drag at the front bag as long as the rear bag does not stick to the buttstock. Lots of things can be used at the rear bag; used dryer sheets, powder, boron nitrate, silicon spray, etc.
Gene Beggs
Click to expand...
In the past, to solve a different problem, I've used long-thread felt laid over the bag. I'll give it a try.

Have you further thoughts, at least on rear bags & stocks? Have you done any work with how the bag and stock should fit? Al Nyhus & I feel, but cannot prove, that the stock should not have the majority of it's weight on the bottom of the bag, as can happen with a multi-stitched bag and a stock with a flat bottom.

I also notice that in the little score shooting I do, I shoot the target sequence numbers 5-4-3-2-1. That is, first up, then left, then down. My first target, 5, is usually an X. 4 tends to go high, as can 3. after those, move left and down, and 2 tends to be a bit low, and 1 really low. Not a good sequence with Creedmore tie-breakers.

I do pull the rifle back & forth to settle it after each movement. I guess it helps, but the shot pattern usually stays the same, just less of it. It is predictable enough I can hold for it, but that is a patch, not a solution.

Thoughts?

* * *

And lest the thread take off too far on the rear bag issue, anybody else have other thoughts for popping one high, say -- say, a bad habit with the shoulder & free recoil, or . . . ?
 
Charles, this may be a problem to which there is no definitive answer. The rimfire shooters use one-piece rests that have no sand bags; the rifle's stock rides on delrin contact points somewhat like our rail guns. Of course, our rules prohibit such.

Let's keep working at it. Maybe someday we will come up with something better.

Gene Beggs
 
Just a thought, not mine, but Tony mentions in his book that too firm a front bag gave him unexplained vertical once in a while. Especially on the bottom. It caused a periodic stock bounce by not absorbing the vibration.

virg
 
when studying this situation one may wish to get a few different stock designs, then screw a BAT pillared action with a proven barrel onto it and fire it in your tunnel, or sheltered range to see what is happening. One may also want to see what difference the rear bag ear height and ear spacing has on this occurance.

or just recognize it is there and deal with it.

I did the test when coming to a conclusion on the rear butt design on the JTR by Robertson. (hint you need to have a rear bag design in mind before deciding on your stock design or else you will have to experiment with different rear bags to get the proper tracking) (on some guns you can actually feel the vibration pattern come back in a snake or side to side pattern, this does not mean the gun wont shoot just that the rearward motion is a snake pattern, even though this can be stable)

later Jeff
 
Charles you may be on to your own answer but....
You have stated that you know where the shots will go based on your firing pattern 5,4,3,2,1,
If you fire them in the opposite order and also if you fired them in a totally different order do the shots still fall in the same place on the numbered target as they do when you fire in the 54321 sequence or do the shots fall sequentially low high and what not regardless of which targets are shot. Hope that makes sense.
 
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