basic ap ballistics questions

gordonfriesen · Post by **gordonfriesen** » Tue Jan 20, 2009 4:03 pm

Folks,

Please bear with me here, as I am an airgun novice.

What are the basic ballistics of airpistols at different speeds? How flat is the trajectory out to 10 meters? What is the effect on target position of different weights of pellets? What is the usual weight (or choice thereof) for target grade pellets?

Thanks,

Gordon

Rover · Post by **Rover** » Tue Jan 20, 2009 4:47 pm

I'm not quite sure what you're asking, but here's some answers anyway.

Pellet weights run from 7 grains up to about 8.4 grains. I like lighter ones in the lower powered guns, but it really doesn't seem to make a difference except that it might cut a slightly cleaner hole in the target.

I asked Don Nygord about this once, and he said it just didn't matter what weight one used.

Most pistols will shoot at around (give or take) 500 f.p.s. and pellet weight does not seem to change the point of impact more than, say, a click. I don't make a sight change when switching from 5m to 10m shooting.

I often throw the ends of the odd can of pellets into one and use them for practice. APs are pretty forgiving, but I can't speak to the higher accuracy demands of Air Rifle shooting.

gordonfriesen · Post by **gordonfriesen** » Tue Jan 20, 2009 7:37 pm

Rover,

Thanks for the info. I did my sighting in at 5 meters, and was wondering what would happen at 10. More particularly, my gun seems to be set up to shoot higher than I like (sights all the way down and sub-six hold still a little high), and I wondered if that meant my shots would be falling off at 10 meters.

Best Regards,

Gordon

tenex · Post by **tenex** » Tue Jan 20, 2009 10:46 pm

Hi Gordon,
Here's a simple trajectory calculator that can answer a lot of your questions:

http://www.airguns.net/software_downloads.php

It's a neat program, and can be used to predict trajectory at different distances.

Steve.

Rover · Post by **Rover** » Wed Jan 21, 2009 10:13 pm

Since you seem to be having trouble with your sights, be bold!

Take a mill file and start hacking away at the top of your rear sight (about 1/16" to start).

I have found itis really hard to cut the notch in the sight square with little Swiss files so I take a small chain saw file (they have no taper) and just clean up the notch into a "U".

The Russians have been very successful with this and I kinda like it myself. I have found most stock sights do not show enough white around the front sight and it makes them hard to use, especially with a center hold or with older eyes.

Go for it...you can always buy a replacement.

gordonfriesen · Post by **gordonfriesen** » Wed Jan 21, 2009 11:28 pm

Rover,

I will have to do something like that. Actually I was thinking of trying to build up the front sight. Haven't figured out quite how yet. Maybe the file is the way to go.

Tenex,

That is a very interesting download.

Thanks,

Gordon

j-team · Post by **j-team** » Wed Jan 21, 2009 11:59 pm

Just out of interest.

How much is the conversion costing, compared to the cost of a SCUBA tank?

Richard H · Post by **Richard H** » Thu Jan 22, 2009 8:18 am

What air pistol are you shooting?

Fred Mannis · Post by **Fred Mannis** » Thu Jan 22, 2009 9:08 am

Gordon, if you are referring to your IZH53 in this thread, it is a relatively low velocity pistol and different weight pellets may have significantly different trajectories - or at least enough to get you to suitable POA.

Fred

Rover · Post by **Rover** » Thu Jan 22, 2009 1:02 pm

To build up the front sight just superglue a small piece of brass shim stock to the face and file to neaten. Paint black. This is also an opportunity to widen your sight.

I personally would work with the rear sight. I could probably do the whole thing in 2 minutes, but I have the files.

I doubt that changing pellet weight will help you with this (as it will with a firearm). You can try, though. Cheap, good 7gr pellets are RWS Basic or Hobby. You can probably bum a few heavyweights from another shooter if you don't have any.

Rover · Post by **Rover** » Thu Jan 22, 2009 1:15 pm

Another quick and dirty solution that I have successfully used with an air rifle:

Whack the middle of the barrel hard with a rounded piece of wood opposite the side you want the pellet to go. In your case the top of the barrel as it will "raise" the front sight.

Crude, but effective. Brought to you by the "Get A Bigger Hammer" school of repair.

Rover · Post by **Rover** » Thu Jan 22, 2009 4:53 pm

Well, that pellet weight business drove me crazy until I could confirm what I said.

I went out to the garage and shot 10 shots at a 5 meter target from 18' from the standing one hand position.

Shooting RWS Basic (7gr) and JSB S100 (8.3gr) mixed I shot a 98 score 2 hole group (one hole was the two 9s, called). The 10s were well centered.

Good enough for me. The 2 beers I had first may have helped.

ronpistolero · Post by **ronpistolero** » Thu Jan 22, 2009 7:09 pm

Gordon,

My thoughts. Before you do any modifications on your front sight, try to find out if you can remove it. If it can be removed, you can put a 0.5mm shim under it. If it can't be removed and you would really have to "mess it up", you may want to try using epoxy instead so that it can easily be filed/contoured. Then spray black paint or light a masking tape and let its smoke temporarily blacken the modified surface. A way to test if the front and rear sights are aligned on its plane is to put the sights against a piece of glass pane.

Regards,

Ron

gordonfriesen · Post by **gordonfriesen** » Thu Jan 22, 2009 10:45 pm

Fred,

Yes this is the low end spring gun, izh-53m. I am trying to find a gun that I can use to teach shooting to a couple of youngsters without dragging their parents into any serious expense. The izh-53m has primitive but functional micrometer clicks for both horizontal and vertical. It shoots ok groups (meaning that it will put them all in the black at 5m on the scaled down target). It also has a very light cocking pull (13 pounds) so it is easy for a kid. I have ruled it out for teaching, however, because follow through is well-nigh impossible. Whatever else an airgun is good for, it should allow you to see the front sight remain in the notch throughout the shooting proccess. Unfortunately the spring mechanism throws the gun more than rimfire does.

Other cheap crank guns exist with direct compression of the air, but the cocking effort is very tedious for the young (21-27 pounds). After that comes the izh-46, but that is a full sized gun, and very heavy for young arms.

There is also a popular gun made by crosman, the 2300t which uses co2 cartridges, and therefore has a stable send off and follow through, with no cranking, and it also has reasonable sights, but, it has a top speed of 520 fps which makes it a restricted weapon in Canada (I'm in Montreal) and therefore none of the airgun people can order it.

I am now trying to find a store on the border of NY state (hopefully Plattsburgh), and I will buy one and carry it across the border myself as a restricted weapon, and then get it verified and certified at 500 fps (a judicious choice of pellets and an understanding "verifier" should do the trick) so that it becomes legally just an airgun again. (BTW anybody in northern NY please feel free to suggest a vendor.)

Ron and Rover,

Those are good tips. I especially like the mallet solution. But a pistol barrel is a lot shorter than a rifle, and this operation becomes more delicate. In any case, tomorrow I am going to take it to the range where I can test it at 10 meters. I expect that the shot will fall a little. Actually, the manufacturer seems to expect that the gun will need to be adjusted UP, not down. There is a second rear sight blade with the gun, and this one is taller than the one in it now. Also the front sight is on a spring-loaded bar ( at its highest position) and you can shim under the butt of the bar to bring it down, but there is no room left to let it up.

This gun is sold as "the most poplar training pistol in Russia". It certainly is an attempt to produce something that can hit a target for next to nothing. I'll let you know tomorrow what it does at 10m.

Best Regards,

Gordon

Rover · Post by **Rover** » Fri Jan 23, 2009 2:59 pm

One more time:

Pity that Pardini no longer makes the P10, a simple SSP with great grips and trigger. It was light, easy to cock and accurate...even at its rather puny 400 fps. It was ideal for young shooters.

There was a Pardini dealer on Long Island named Phil Saccio (Saccio Studio) and he sold a bunch of them. There might be a few used ones floating around NYS.

Fred Mannis · Post by **Fred Mannis** » Fri Jan 23, 2009 3:19 pm

Gordon,
Two other pistols to consider - Weihrauch HW75 (formerly the Beeman P2) and the Weihrauch HW 40 (Beeman P3). These are SSP pistols with a reasonable cocking force. I have shot both guns and both are capable of shooting 90/100 on a standard 10M target.
See http://www.pyramydair.com/cgi-bin/show. ... =Weihrauch for detailed specs

Regards,
Fred

Seftref · Post by **Seftref** » Tue Jan 27, 2009 8:37 am

Trajectory is relativelly flat out to 10 meters (33 feet).
Flight time to 10 m is a triffle less than 0,1 sek.
Fall of said pellet is then 1/2 *9.82 m/sec*(0.1)*(0.1)sec*sec = 0.05 meter, 5 cm that is, or about 2 inches.

Hope this clarifies the matter.

gordonfriesen · Post by **gordonfriesen** » Tue Jan 27, 2009 8:43 pm

Seftref wrote:Trajectory is relativelly flat out to 10 meters (33 feet).
Flight time to 10 m is a triffle less than 0,1 sek.
Fall of said pellet is then 1/2 *9.82 m/sec*(0.1)*(0.1)sec*sec = 0.05 meter, 5 cm that is, or about 2 inches.

Hope this clarifies the matter.

Seftref,

I wish I undersood the factors in that equation! Two inches fall would give me comfortable adjustment room.

I had meant to make a practical test on friday, but it turned out that my range was closed for an IPSC competition. This gun is fun to shoot. But I find the behavior of a spring gun at lift off, especially seen from the perspetive of a 15 inch sight spread, to be very difficult to understand.

Thanks for the info,

Gordon

spacestout · Post by **spacestout** » Thu Jan 29, 2009 7:04 pm

Gordonfriesen asked about basic ballistics and pellet velocity. There are a lot of parameters when it comes to ballistics; energy and velocity at muzzle and some point down range, trajectory, to name a few.

You can sure find a lot of information by online searches. Many people have conducted experiments. For example, on this link you can see the results of 5-shot groups by holding everything constant and varying the pellet velocity (you can adjust the velocity on many high-end guns).

http://www.mra.org.in/Bench%20testing%2 ... Pistol.pdf

Their data seem to support what many people believe; that velocities around 525 fps give the best groups or accuracy.

I conclude that the human factors affect accuracy far more than ballistics. In all their testing, they are still within the 10 ring. My experience backs this up.

I just acquired a Steyr LP1 CO2, an Anschutz LP@, and Steyr LP5 CA from someone retiring from coaching and shooting. They are all beauties but I knew I could only afford to keep one and sell off the rest. First thing was to check out the gun conditions. Next, I figured that if the guns shot accurate and consistent groups at consistent velocity, I could conclude good things about barrels, seals, regulators, etc. So, I did like I've done with .22 pistols; hand hold the pistol in a rest. My targets showed erratic groupings spread way larger than I thought "one-hole" guns should shoot. The groups suggested that with my bad eyes and iron sights, even holding still I was introducing error. What I'd done with .22 pistols involved a scope. I decided I needed to remove the human factor as much as possible.

I built a bench rest vice like in this post and shot thru a chronograph:

http://www.pilkguns.com/mako.htm (you can find a lot of the info you seek on pilk's site)

In this article, the author is still using a quality gun, quality pellets. You can see that varying pellet weight and size do make a difference, however, just a couple of mm. Beyond notice for most of us shooters. Quality pellets shoot well in quality guns, he concludes.

Back to my story. All my guns shot nearly 1-hole 5-shot groups with a Champion's Choice pellet whose weight I'm not sure of. A Gamo Match of weight 7.71 spread out more, about 1/4". And expensive RWS R10 pellets of 7.0 gr had the worst patterns. I haven't concluded testing to know what the optimum pellet will be for each gun. But they don't like the very light pellets.

I did fulfill my purpose. The data showed the guns to be accurate, and repeatable in group size and velocity shot after shot.

I'll make the agonizing decision of which gun to keep, then, being the engineer, will tinker with finding the pellet which shoots best. Somewhere in there I need to practice. Shooting freehand vs bench rested vs vice-held really bears this out

Fred Mannis · Post by **Fred Mannis** » Thu Jan 29, 2009 7:52 pm

I'll make the agonizing decision of which gun to keep, then, being the engineer, will tinker with finding the pellet which shoots best. Somewhere in there I need to practice. Shooting freehand vs bench rested vs vice-held really bears this out

Having established that all three pistols are mechanically sound and can shoot good groups, I suggest that the choice be made by finding which gun feels the best to you (grip, balance, trigger,...) and shoots the best for you. I too love to tinker, but I would spend my tinkering time on the triggers to find which one suits you best. Certainly the single stage LP5 trigger is a very different beast from the two stage LP1 trigger.

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