FP Group Testing Methods?

[Mark Briggs]

Hi Folks,

I have a little dilemma that I'm hoping this fine crew of TargetTalka's will be able to help resolve. I have three different free pistols that I want to perform ammunition group testing with (Toz35, Hammerli 150 and Morini CM84E). I have access to a Ransom rest through our club, but of course, this rest has no inserts for such fancy pistols as my FP's. So here's the dilemma - how do I economically group test the pistols?

Ideally I'd like to find some home-made device which would allow me to support the pistol such that returns to battery in a repeatable fashion, and yet would still allow the pistol to free recoil. Obviously the H-150 and TOZ are fairly easy to accomodate in any test rig because the grips can be removed and the gun can be bolted to a very simple slab of wood or metal to hold it solid. The CM84, with its grip-mounted electronics, is an entirely different kettle of fish. With this beast the grip pretty much has to be left on the pistol, making it a much more difficult pistol to accomodate.

So, if you have a device you use to test your FP's, I'd like to hear about it. The cheaper and easier to fabricate, the better it will be from my viewpoint.

Thanks in advance for your thoughtful comments and positive input!

[Ernie Rodriguez]

Mark-I saw a photo involving a heavy vice with dense rubber jaws attached.The rubber jaws surounded the BBL of the pistol and the grips rested on a fixed table-it looked pretty stable.One other idea that might work is using sandbags and trying it out-using different brands of ammo and see what the results look like.And finally-I have read a number of articles that indicate if you use top quality ammo,chances are the f/p will group within the x ring anyway.I have done extensive testing with competition 38/45 's and I can tell you it is quite time consuming-HOWEVER-the testing was always done using a Ransom Jig with the proper adapters.Ernie

[Mark Briggs]

ER - thanks for your comments. I've looked at the concept of clamping the barrel in a vise, but this has a couple of shortcomings (the vise changes the harmonic response of the barrel, and the whole vise setup has to absorb the entire recoil force, meaning it would have to be a very heavy device to produce any accuracy).

I've already tried the sandbag routine, but without the benefit of a single plain of reference sighting system (ie a scope) sighting errors can cause significant group dispersion.

I recognize that all good ammo will produce reasonable results, but my limited testing to date shows that some produces very different results than others. Now I'd like to get down to a little finer point in seeing exactly which ammo does the best in each of the pistols. A Ransom rest would be the way to go, were it not for the complication afforded by the CM84 electronics. Hmmm, need to think some more about this one...

[FredB]

Mark,

I'd like to suggest that your objections to clamping the barrel may be questionable. I really doubt that the barrel harmonics are a significant factor with the relatively short FP barrel at 50 M. And the Ransom Rest can certainly absorb far greater recoil than generated by a FP. If you can obtain a blank R-R insert, you can use it in the R-R to clamp the barrel securely. Everything I have read and seen (video) indicates that barrel clamping is the way all manufacturers do their testing.

HTH,
FredB

[Steve Swartz]

Mark:

1) Attach laser pointer type sight to the gun
2) Sight with pointer for each shot, stabilizing wobble with sandbags under heel of gun only
3) Shoot at least 30-shot groups
4) For each group, calculate shot centroid and then measure distances from centroid for each shot
5) Calculate average and standard deviation of average for distance measurement for each group
6) Compare average distances between groups. If the averages are not at least 2 standard deviations apart, either the groups are equal *or* you need to fire more groups for comparison

Note that most testing is done from ransom rest or fixed rest because most folks believe that how a firearm responds in a human hand vs. in a barrel clamp is not significant; in other words, the tightest groups from a vice would still be the tightest groups in your hand.

Remember, you aren't trying to determine the theoretical accuracy limit of any particluar ammo type- you just want to identify which is better. The response in the human hand vs. vice might be very important to consider if what you are trying to do is determine the "true accuracy;" but might not be an issue at all if what you are trying to determine is "relative accuracy."

Steve Swartz

[Mark Briggs]

Hmmmm, interesting answers and points to ponder, as always. Every time I ask a question here I'm reminded of how valuable this forum really is!

Steve - you're definitely right on the money when you mention that I want to establish the relative accuracy of different ammo types. This being the case, the barrel clamp method might indeed suffice as a means of eliminating other variables from the accuracy equation. Especially since, in the real world of FP shooting, the ammo, pistol, pistol-to-hand interface (grip) and the rest of the human body holding the pistol all function as a system in which the individual elements interact to produce a group on the target. Although I appreciate your suggestions, I doubt I'll do the large amount of math you've suggested - after a day at work I suspect my brain's too fried for that degree of higher computational tasking! *grin*

FredB - your comment about using the Ransom Rest while clamping the barrel in a blank insert might be the best compromise of offering recoil damping (so I don't have to mount the thing on concrete pilings) and repeatability. Will have to give this some thought... Also - you mentioned reading and seeing video of tests done using barrel clamping methods. If you have any web references to this info, I'd sure appreciate it if you could post them here so that I (and others) might enlighten myself further.

Once again, thanks to all for your valuable feedback!

[PaulT]

Ammunition testing at Eley is in a barrel clamp for free pistol. I found virtually any batch of Tenex would hold the X ring (25mm) and several held a far smaller group. By way of comparison, Lapua Pistol King held tight groups well inside the X ring and Midas L marginally better. This data provided me batches of match (Tenex/Midas) and training ammunition (King).
So, with the ammunition sorted, then comes the minor problem of delivering the shots in a nice tight group yourself. I would not suggest expending too much time or effort getting hung up on ammunition testing. I feel it important to make sure your equipment well exceeds the task required as this will provide confidence, once completed, the rest is up to the shooter!

[Guest]

My humble opinion on Barrel/Ammo accuracy testing.

You gotta simulate the state the combo is in when it is fired.
And to me, a clamped FP barrel is not in its free state.
Clamp the action for sure, but let the barrel free!!!My humble opinion on Barrel/Ammo accuracy testing.

[David Levene]

My humble opinion on Barrel/Ammo accuracy testing.

You gotta simulate the state the combo is in when it is fired.

Should you be interested in the barrel/ammo accuracy. Isn't the complete gun/ammo/shooter/conditions combination more important. How you would test for that though I have no idea, but if you are worried about getting 1-2mm tighter groups you need to test with all of the causes for errors/differences included.

IMHO too many people are getting anal about testing. As has previously been said, good quality ammunition will hold the X ring so there are no excuses for a bad shot. Shoot at the middle and you will get a 10.

[VAshooter]

I have never taken the grip off a Morini CM84E but I have experience with their air pistol and if I wanted to fire the pistol out of the grip I would simply make a jumper cable to go from the pistol to the grip.
If the connector is the same as the air pistol let me know and I will make one for you if you don't have the capability to do it.

I wonder if the ammo that shoots the smallest group in a barrel clamped in place will also shoot the smallest group in the same barrel hanging free fired in the normal manner.

I would be interested in what shoots well in the Hammerli 150 as that is what I am shooting. Good luck in your search for the perfect combination.

Doug

[RobStubbs]

I tend to agree with David here in that I can see the point of getting good ammo over bad ammo, but trying to work out good from slightly better ? Is a test group 5 or 10% better than another really better - or is it down to statistical variation ? How many times for example would you need to repeat the 'experiment' to get a statistically meaningful result ? Even if you do find an ammo that is really better what does that equate to at the business end ? What I mean is over a 60 shot match a worse ammo may actually lead to you dropping a couple of points at the very worst and would probably make absolutely no difference. I am absolutely certain that ammo is the least of my worries with the free pistol as I can lose far more than that in a single poor shot.

Just as a small aside, how many air pistol shooters ever batch test pellets ? Surely the same variability must ocurr yet I don't know anyone who batch tests pellets - other than perhaps to initially test a best size and manufacturer.

Rob.

[Richard H]

I agree, with pistol the shooter contributes more variation to the system than any high quality ammo does. The variation in ammo may even help the shooter. Example, on this shot I am a little low but do to the variation in the ammo I score a ten, I know the opposite is also true. I think the time that one would spend ammo testing would be far better used in practising. That being said some just like to tinker and experiment, and if thats what you like to do well then go to it. I really don't believe ammo testing is going to add any points to pistol scores.

[PaulT]

In addition to my earlier post – I think it is important to make sure that the ammunition is not letting you down. If, for example, the ammunition can not hold the 10 ring (and we have seen several budget brands with this problem) then you are probably not doing your self any favours if you generally hold a nine ring group or better. For indoor training, something like Lapua Club (in tins!) or Eley club/pistol holds the ten on a scaled down 50m target at 25m nicely. So cost should not be a factor of compromise as it may be with rifle shooters. BTW use Eley Pistol Match with caution in the Morini, this is a low velocity round and several of us found it did not hold a 9.5 group at 50m!

The “shoot out of the hand” is an interesting point. I shot some nice 40 shot matches this week (I shoot two 40 shot matches in some training sessions) and they held the 9.5 ring on 50m electronics scoring targets with a few called eights and lesser nines (I will not share with you what I called them but they were called and dismissed!). Interestingly, on both sessions, the was one match a piece with Lapua and Eley (see above post from details). The brands did feel different in recoil, with the Lapua feeling smoother and a bit more controllable with follow through. I do shoot with a compensator so this may have some bearing. As the lesser recoil has a lesser influence on the variability of the grip (shooter error), it is possible that this is to be favoured. Both ammunitions are unquestionably accurate, behave the same in wind don’t discharge ammunition flyers.

Until recently, I did not batch test air pistol pellets. When I had my Morini serviced, the pistol was apparently velocity optimised for my pellet batch. I had given the engineer a tin of my pellets not knowing he was going to do this for me, I assumed incorrectly he had forgotten his tin again! The pistol was returned as the engineer was just about to go on a shooting trip and I had just returned, the service was forgotten and detail not mentioned! I shot three successive match PB’s, one with my best ever number of tens and some excellent groups in all matches. Interestingly, I was later given my pellet tin back with the results of a tight one shot hole after 20 shots going through it. The other pellet batches were not as good and pre velocity adjustment, it was X ring but only just! I am pleased I just picked up 20k of the batch and I will integrate the testing with the pistol service.

[Mark Briggs]

PaulT - thanks for the hint about Pistol Match. I enjoy the way it feels in my Morini (with comp), but haven't had good success with it. Perhaps your testing results resonate with my experience!

You mentioned that some ammo won't hold the 10-ring. That's really my concern with all this testing nonsense; I want to prove to myself that all the ammo I have on hand will provide sufficient accuracy for my needs and that my scores are not being punished by an incorrect choice of ammo. Likewise, I want to prove to myself that all of my FP's still have the capacity to hold the 10-ring, even after their years of service.

On the subject of pellet testing, you're lucky to have service personnel who are capable of doign that kind of fine tuning. Whoever he is, hang on to him! I've had a similar experience with my CM162 wherin I tuned it to my current batch of pellets. Group size shrunk almost 50% as a result of tuning and now is a very tight one-holer. Thank goodness I've still got 15 or 20 thousand of those pellets left, as the tuning process takes time to complete.

[David M]

I have a rest similar to a ransom, that uses a steel plate (with multiple mount holes) pivoted for recoil on a base plate.
Two blocks of 5" x 4" (1" thick) nylon were milled to fit over the forward frame of the morini free pistol and partly on to the barrel (approx 2" only) leaving a hole to access the trigger.
I have tested the pistol with multiple barrels (varing lenght and mfg.) both with and without compensators fitted.
Generally most ammo will group 20-30mm, with the best groups are around 18mm (50m distance).
Group test in 10 round groups as most ammo will group well only to be spoilt by some flyers out of the group.
The thing I have learnt is that cost of ammo will have little effect on average group size, but has a bearing on consistency (least flyers).

[Mark Briggs]

Thanks to all for your helpful comments and suggestions. I've now just about completed a custom-made rig for testing. It clamps the pistol and allows it to recoil freely on what is essentially a horizontal track. I'm most anxious to prove out some of the data the kind contributors have provided here.

David M - a special thanks to you for your response, knowing you're just back from the WC circuit and probably still feeling the effects of jet lag! You've been providing one of my teammates with some "neck and neck" competition in scores. Congratulations on the nice shooting. Wish I could have made it to Munich and Milan, but not at all sorry to have only made it to Ft Benning. After all, a bad day of shooting is better than just about ANY day at work!

Now that I have a spare barrel for the CM84 I'll also be testing one barrel against the other to see how they stack up. Hmmm, could be interesting... ;-)