Paintball research respository

[cledford]

Try this...

FatMan,

Try a precison digital powder scale. They're used for weighing powder charges when reloading firearm ammunition. They can measure in either grains (fractions of grams, 1 grain = .0647 grams) or grams.

Here are the parameters for the pact version:

1500 Grain or 100 Gram Capacity.
.1 Grain or .01 Gram Resolution.
+- .1 Grain .01 Gram Accuracy.

I've got one and it works great.

You can find more info at Pacts website:

http://www.pact.com/disp.html

-Calvin

[AGD]

Since we have years of experience doing this I'll give you some hints. First of all the weight difference between paintballs is nothing to worry about and you would need a scale that does 10ths of a gram anyway.

Use large sheets of paper for the targets with no backing. Tape them into a frame with each corner marked so each paper can be aligned and taped in the same postition. Fire 10 rounds and then go down to the paper and put an x across each tear hole and make sure you come up with 10 x's. QUite often balls go through the same tear. For precision groups we have someone stand down range behind plywood and they come out and mark each impact point since they can see where it hit. Enter the x,y coordinates in Excel to get your statistics. Do not bother creating a 1 inch grid for each paper use a yardstick to measure each x.

AGD

[FatMan]

Thanks again AGD!

Gee, I hope you don't get tired of hearing folks say "thanks!"

Well, I had just managed to find a place to borrow a scale with .001 gram precision (thanks for the idea bjjb - I had one of those once). On the other hand, if ball weight variation is just going to be noise it would sure speed up the test procedure to skip that. I'm willing to accept AGD's experience on this unless everyone thinks I should do it to be SURE I can account for ball weight variation.

As for the paper idea, that sounds like a good idea. I wasn't going to create the grid, but try to get paper already gridded. If I can't get that, then direct measure would work fine.

Now, my PLAN had been to record weight, speed, and offset for each ball (keeping the three stats together per ball). That would seem to require identifying the hole ball-for-ball. I *could* just get the stats on the speeds and offsets (and weights if I did that) and report averages, std devs, etc. I'm not sure that the detail data would really tell us anything useful.

Once again, I ask you - do I need to identify which velocity went with which offset (and weight) - which would take more effort - or just gather all the data for aggregation. Sounds like AGD is recommending the latter.

As a compromise, I could use the less detailed procedure until I identify the BEST barrel insert (assuming there is one) and THEN do a detailed study of THAT to see if things like ball weight account for whatever variation remains.

Its a thought! Anyway, I'mm still gearing up to start this - so any input from you guys is welcome. And AGD, thanks again for your input!

FatMan

[Redkey]

Another way to do it...

When I was working up loads for my 357 I was performing accuracy tests for bullet and powder load combinations. Since the measuring the shot spread was a hassle I setup an image analysis package to make the measuremnts for me.

A digital image of the impact points is fed into the software which finds the holes due to their contrast with the white paper (I put something black behind the holes). Then the software grinds away to determine the center of mass for each impact and spits out x, y coordinates based on what ever measurement system it was calibrated for. It would also kick out the coordinates of the bullseye for a reference point.

In excel I calculated the distance from the bull for each shot and then used the average and standard deviation of the spread to make the load to load comparisons.

There are several free IA packages out there, if anyone is interested I could look around and find something that will work for this type of measurement. Mine has a dongle so I cannot share.

In the short term the ruler method will always be quicker and just as accurate... the IA method is neat because the measurements can also be taken real-time with a video camera after each shot allowing you to link the impact point with what ever other data has been collected by the computer... velocity, pressure profiles, wind speed etc.

Call me a geek but half the fun is building the test system.

fatman... how will you control your aiming point?

[FatMan]

Project idea

Well, the IA thing sounds like a great project for our students one semester. I think we have most of the hardware around for that. For now I don't want to wait for that, I want some numbers, but who knows, I might do more of this.

As for the aim point, I don't plan to control it. I don't plan to have a bull's eye. Rather, I intend to find the centroid of the shots, and then find the deviation from that. Presumably one must adjust for range and windage when shooting anyway - the issue I'm trying to measure is consistency.

FatMan

[Redkey]

But, are you measuring the consistancy of the marker or your aim? I you don't have control over where the marker is pointed how do you know what is contributing to your spread?

A good target pellet rifle can basically put five aimed shots in one hole at 25 meters. Compare that to a pump up Crossman that can put five shots in one inch at 25 meters. If you were to randomly shoot those guns at a target without aiming you would probably get a similar spread in both shot groupings... even though you knew one gun was much better than the other.

I'd at least put a laser or scope on the gun to make sure your aim point is the same for each shot. Without controlling the aim point any spread calculations will be meaningless.

[bjjb99]

If it hasn't been stated earlier in this thread, the marker needs to be bench mounted or otherwise immobilized during the test to prevent human aim from diluting the results. In an ideal case, the marker would be solidly affixed to a firing platform and fired without anyone touching the marker itself during testing. Even something as simple as a couple of shooting sandbags upon which you can rest and steady the marker would reduce the human factor, and may well be sufficient for a test run of the experiment.

BJJB

[FatMan]

Uh, yeah ...

yeah, looking back at the original post I indicated I would mount the marker to a bench. I was going to use a commercial job, but instead I built one this weekend that fits my marker exactly and holds it still. I intend to strap the mount to a bench (or table, to be more precise), and then fire the marker touching only the trigger.

I didn't realize that's what you meant by controlling the aim point. I thought you meant ensuring that for each test round its pointed at exactly the same spot - there might be variation from round to round, but within a round the variation should be minimal.

Of course, I guess I could mount a laser pointer to the mount (or marker for that matter) to make sure its lined up the same, but I'm not sure that's going to buy me much.

Sorry for the confustion.

FatMan

[AGD]

Fatman,

You should also shoot each shot through a crono and decide if your going to keep the fliers or not. Another idea is to process only the shots within 3 fps and see what the deviation is compared to the whole group. This would tell you the amount of error contributed by velocity variations vs paint in flight.

AGD

[FatMan]

The plot thickens ...

OK, that's a good reason to keep track of which ball made which hole. Then we can look at the whole set to get an idea of the barrel's influence on velocity consistency, and then look at groups within the same fps (+/-) and get an idea of non-velocity related consistency.

Cool! I'm getting pretty fired up about this. I need to work on my target system (based on AGD's suggestions).

I'm trying to get cphilip fired up about assisting, too.

FatMan