TargetTalk

A forum to talk about Olympic style shooting, rifle or pistol, 10 meters to 50 meters, and whatever is in between. Hosted by Pilkguns.com
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PostPosted: Thu Feb 16, 2017 7:40 am 
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The right way - i would say - is to select proper:
- ammo
- velocity
- barrel
(In this order).

Tests without shooting chronograph are misleading.
I did a test last week for a buddy. 10 shots. 9 of them 152-153m/s and one of them 159m/s was a "flyer" to the right 6-7mm from main group. Etc.
With a crony we can check some dependencies. Hevy pellets for air rifle deliver good groups from pistols but with higher energy (and yes - now you have small recoil). If we have setup for heavy air rifle pellet and then switch to light pellet... we have to setup the velocity once again (it will be about 6-10m/s higher after using heavy pellet ... R10 air rifle 4,49 ---> JSB Match Light 4,49... the difference will be very significant (approx +10m/s more)... the velocity have to be reduced to get recommended +/-155m/s).
And vice versa.


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PostPosted: Thu Feb 16, 2017 10:55 am 
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ruig wrote:
The right way - i would say - is to select proper:
- ammo
- velocity
- barrel
(In this order).

Tests without shooting chronograph are misleading.
I did a test last week for a buddy. 10 shots. 9 of them 152-153m/s and one of them 159m/s was a "flyer" to the right 6-7mm from main group. Etc.
With a crony we can check some dependencies. Hevy pellets for air rifle deliver good groups from pistols but with higher energy (and yes - now you have small recoil). If we have setup for heavy air rifle pellet and then switch to light pellet... we have to setup the velocity once again (it will be about 6-10m/s higher after using heavy pellet ... R10 air rifle 4,49 ---> JSB Match Light 4,49... the difference will be very significant (approx +10m/s more)... the velocity have to be reduced to get recommended +/-155m/s).
And vice versa.


Your post raises an interesting question (at least to me)... Does that (relatively small) difference in velocity make much of a difference? I am relatively inexperienced, but I've been of the opinion that tight groups were the most important thing with a match pistol (or rifle). Regardless of the velocity as long as it's not overly low or high.

What I would do (and have done) is determine which pellet can give the group sizes that I am happy with and once that is done, adjust the sights so that the gun shoots where I want it to.

Does a velocity difference of 6 m/s really make much difference at 10 meters?

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PostPosted: Thu Feb 16, 2017 12:31 pm 
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Nah! Half that is normal with PCPs (but not with SSPs). I'll give you that you may need to be fussy with an air rifle, but with a pistol it just doesn't matter, no matter how much fretting and whining goes on here.


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PostPosted: Thu Feb 16, 2017 12:45 pm 
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Mtl_Biker wrote:
ruig wrote:
152-153m/s and one of them 159m/s

Does that (relatively small) difference in velocity make much of a difference?

For the heck of it, here's some math:

Time to travel 10m:
152 m/s > 0.0657894736842105 s
159 m/s > 0.0628930817610063 s

Drop of pellet:
0.0657894736842105 s > 2.12228402008 mm
0.0628930817610063 s > 1.93952968633 mm

Difference: 0.18275433375 mm

So, the slower pellet will drop 0.2 mm further than the faster pellet.

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PostPosted: Thu Feb 16, 2017 4:08 pm 
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Rover wrote:
Nah! Half that is normal with PCPs (but not with SSPs). I'll give you that you may need to be fussy with an air rifle, but with a pistol it just doesn't matter, no matter how much fretting and whining goes on here.


This is what makes pistol shooting attractive to me (in addition to minimal gear). Its more advantageous to spend time playing the game than worrying the technicalities however interesting they may be.


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PostPosted: Thu Feb 16, 2017 5:17 pm 
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SlartyBartFast wrote:

Difference: 0.18275433375 mm

So, the slower pellet will drop 0.2 mm further than the faster pellet.


You're probably describing an ideal system.
Pellets get unstable during the flight at certain velocities (pellet specific thing). Barrel twist.. velocity... pellet mass.. etc.

In my particular case I suppose it was uncalibrated or damaged pellet, that caused 159m/s and "flyer". Other quality pellets showed narrower range of velocities with that particular pistol.


Last edited by ruig on Thu Feb 16, 2017 5:52 pm, edited 1 time in total.

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PostPosted: Thu Feb 16, 2017 5:44 pm 
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Mtl_Biker wrote:
Does that (relatively small) difference in velocity make much of a difference? I am relatively inexperienced, but I've been of the opinion that tight groups were the most important thing with a match pistol (or rifle). Regardless of the velocity as long as it's not overly low or high.


Try it once. Test will take only 10 minutes with usual match air pistol with adjustable velocity.

For example. Take light air pistol JSB pellets 4,49mm / 0,5g. Using velocity adjustment screw and chrony set velocity about 155m/s (comfortable recommended velocity). Shoot a little bit. Muzzle energy ~6J.
Then take heavy air rifle pellets R10 4,49mm / 0,53g. Try to shoot. It is too slow. You must hear it (at least). Chrony measured about 146m/s in my particular case (~5,6J). Adjust the velocity once again (approx. 155m/s)... Kick is heavier now (muzzle energy ~6,4J).
Now switch back to light pellets. Chrony showed 164m/s in my case (~6,7J). You will hear and feel it.

One joule in everyday life represents approximately
* The kinetic energy of a 50 kg human moving very slowly (0.2 m/s or 0.72 km/h).
* The kinetic energy of a 56 g tennis ball moving at 6 m/s (22 km/h).[9]
* The kinetic energy of an object with mass 1 kg moving at √2 ≈ 1.4 m/s.

We talked about feelings and recoil.

Now try to test the groups... heavy and light pellets... velocity range from 146m/s to 164m/s.

And then.. correlate your best feelings and best groups... and decide what pellets are best for you.


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PostPosted: Fri Feb 17, 2017 10:06 am 
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Location: Montreal, Canada
Awhile ago (thanks to Rover's strong endorsement) I bought a bunch of RWS Basic pellets to use for training. And with my pistol in a vice, tested them against other higher end/cost pellets I'd been using and the results were superb. Especially at my current skill level, those RWS Basics are really all I need. Not quite as tight groups (clamped gun) as JSB Match Diabolo, H&N Finale Match Pistol or QY Training, but fairly close.

Unfortunately it seems only one Canadian source sells these (other sources sell only the higher end RWS pellets) and I cleaned them out. So because I was down to my last two tins of Basics and since the next shipment isn't expected for probably close to a month from now, I decided to try the H&N equivalent (as near as can be determined) and last night I had my first chance to try them out.

First impression was that they looked dirty while the RWS Basics were bright and shiny. That apparently doesn't matter though, because the H&N Sport pellets turned out to give BETTER groups than the RWS Basics did and just slightly worse than the top-of-the-line other pellets I have.

After testing the pellets with a clamped gun, I shot a full match against a friend. And my score was a full 20 points better than my prior best! Maybe it was me, maybe it was the phase of the moon, or maybe the H&N Sport pellets had a wee bit to do with it, but I was very happy with the result.

And I couldn't care less that these are heavier pellets than the RWS Basics (8.18 gr versus 7.0 gr) and that they may be shooting at a different velocity than the lighter pellets. All I care about is that they group really well in my gun even if the velocity may not be optimum. I'm not even going to bother chronying the result because it wouldn't make any difference to me.

And the final bit of good news about these pellets is that they're a wee bit less expensive than the RWS Basics, so they've just become my new go-to pellet. Over the weekend I plan to test them in my match rifle also, and I expect and hope that they'll prove to be just as good there.

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PostPosted: Fri Feb 17, 2017 10:42 am 
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Location: Maine
I wonder if the extra weight played a role. I prefer RWS R10 8.2 gr. pellets for matches, my Izzie seems to like the heavier weight.


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PostPosted: Fri Feb 17, 2017 7:35 pm 
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SlartyBartFast wrote:
Mtl_Biker wrote:
ruig wrote:
152-153m/s and one of them 159m/s

Does that (relatively small) difference in velocity make much of a difference?

For the heck of it, here's some math:
...
Drop of pellet:
0.0657894736842105 s > 2.12228402008 mm
0.0628930817610063 s > 1.93952968633 mm

Difference: 0.18275433375 mm

So, the slower pellet will drop 0.2 mm further than the faster pellet.


For what it's worth, you are out by a factor of 10. Pellet drop at 10m is a couple of centimeters, so the difference in your example is 2 mm. As mentioned by ruig, pellet stability - which can vary strongly with velocity - could affect shot dispersion (not just drop). In my own tests, pellet size - 4.49mm vs 4.50mm vs 4.51mm seems to have a more significant effect.

Perhaps in most cases the actual difference is not really physically significant in the mechanical sense. But pistol shooting is very much a mental game and anything that helps stabilize the mind can be useful and shouldn't be dismissed out of hand. Since we are all so different, what helps one shooter's mental state may not always help the other. The purpose of any such testing should be for building confidence and not to reduce the shooter into a nervous wreck, fretting constantly about the equipment.


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PostPosted: Fri Feb 17, 2017 8:42 pm 
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metman wrote:
For what it's worth, you are out by a factor of 10. Pellet drop at 10m is a couple of centimeters,


Having simply calculated the time in flight and plugged the time into an online equation, I would be interested in how you came up with your results.

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PostPosted: Fri Feb 17, 2017 9:29 pm 
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Location: New Hampshire, USA
QUAM MULTI ANGELI IN APICE ACICULAE SALTARE POSSUNT?

I hope I'm not too far off - I took my last Latin class over 50 years ago.


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PostPosted: Sat Feb 18, 2017 8:33 am 
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william wrote:
QUAM MULTI ANGELI IN APICE ACICULAE SALTARE POSSUNT?

I hope I'm not too far off - I took my last Latin class over 50 years ago.

Close enough. Depending on what scripture you subscribe to, the answer is zero. Angels are far to stuffy to dance.


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PostPosted: Sat Feb 18, 2017 8:59 am 
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Location: Scottsdale AZ
Latin quotes are great, but let's handle this empirically. Scroll down to the post by jteam on this thread:

viewtopic.php?f=6&t=54059

This mirrors my own no bullshit tests.

BTW Do they do the "freddie"?


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PostPosted: Sat Feb 18, 2017 10:49 pm 
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SlartyBartFast wrote:
metman wrote:
For what it's worth, you are out by a factor of 10. Pellet drop at 10m is a couple of centimeters,

Having simply calculated the time in flight and plugged the time into an online equation, I would be interested in how you came up with your results.

Flight time in a vacuum is OK for this calculation. In air there is a small drop in speed by the time the pellet reaches the 10m target, around 2 or 3 m/s, (1-2%) so actual flight time would be more, but for this exercise it's not significant.
Drop in gravity with no air drag is high school physics:
Drop = 1/2 x g x t^2
where
g=981 in cm/s/s, is gravitational acceleration at ground level,
t is time in seconds.
For values of t ~ 1/15 sec for travel from muzzle to target, the back of the envelope gives
Drop ~ 490 x 1/225 = 2.2 cm
Your units should have been cm, not mm.
Even with these values the difference is small.


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PostPosted: Sun Feb 19, 2017 8:22 am 
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metman wrote:
SlartyBartFast wrote:
metman wrote:
For what it's worth, you are out by a factor of 10. Pellet drop at 10m is a couple of centimeters,

Having simply calculated the time in flight and plugged the time into an online equation, I would be interested in how you came up with your results.

Flight time in a vacuum is OK for this calculation. In air there is a small drop in speed by the time the pellet reaches the 10m target, around 2 or 3 m/s, (1-2%) so actual flight time would be more, but for this exercise it's not significant.
Drop in gravity with no air drag is high school physics:
Drop = 1/2 x g x t^2
where
g=981 in cm/s/s, is gravitational acceleration at ground level,
t is time in seconds.
For values of t ~ 1/15 sec for travel from muzzle to target, the back of the envelope gives
Drop ~ 490 x 1/225 = 2.2 cm
Your units should have been cm, not mm.
Even with these values the difference is small.


Enough is enough. Or is it too much? What difference does the actual value of pellet drop make? If the holes - real or virtual - end up lower (or higher) than you expect them, adjust your sight accordingly. You don't have to do any calculations other than:

1 click = X millimeters.

To quote the title of the 4/02 Nygord's Note: "So that's why there are screws on my rear sight!"


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PostPosted: Sun Feb 19, 2017 8:30 am 
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C'mon William, even if they are a click or two out, how would they know. Nygord said he MIGHT take a click if he thought he needed it, but these guys aren't World Champs.

Let's get them angels aprancin' again.


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