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hello from B.C. 
PostPosted: Fri Mar 07, 2014 11:29 pm Reply with quote
bcbuddy
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Hi folks.
im kinda new to air rifles i mean i had one as a kid but never put much thought back into them until i bought a stoeger x20 with an "advertised" FPS of 1200 with steel alloy pellets.
I bought it as a varmint/rabbit rifle.
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PostPosted: Fri Mar 07, 2014 11:47 pm Reply with quote
bcbuddy
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P.s. im wondering if someone had the tools and the time how difficult would it be to "polish" an air rifle to make it faster
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PostPosted: Sat Mar 08, 2014 7:35 am Reply with quote
DavidSaunders
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bcbuddy wrote:
P.s. im wondering if someone had the tools and the time how difficult would it be to "polish" an air rifle to make it faster


Just remember with an air rifle you do not want to go past 850FPS, anything faster and you start to loose accuracy. If you want more power get a gun that shoots heavier pellets in the 600FPS to 800FPS range.

Also if you are just getting into airguns I would recommend against a springer (break barrel/gas ram/nitro piston/spring air) gun. This is because of the double recoil that takes a significant learning curve.

A better low cost entry point would be a good CO2 gun like the Crosman 2240, or a Multi Stroke Pneumatic like the Crosman 2289b Backpacker (sold in the Crosman doomsday Bugout Kit). Both of the guns that I mentioned are .22 cal, and less than $80.00 US.
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PostPosted: Sat Mar 08, 2014 7:36 am Reply with quote
DavidSaunders
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And welcome.
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PostPosted: Sat Mar 08, 2014 8:37 am Reply with quote
AirGunEric
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I would have to disagree with some of the content posted above- 850fps is not a "barrier" to accuracy- the only 'rule' in that respect is turbulence around the speed of sound- i.e. 1020-ish fps. Accuracy is otherwise going to be dependent on the pellets and barrel being used. I would agree that a springer (and the more powerful the springer, the more so) is the most difficult gun to master, if a person understands that and works to become a good shooter with one, pretty much every other gun they touch will be almost a joke in respect to becoming a good shooter (the classic statement being if someone can become a solid shooter with a high-powered springer, they can shoot anything else at least as well). It is challenging when first starting, but I don't think this should be a barrier unless someone is impatient or doesn't have the time to practice very often.

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PostPosted: Sat Mar 08, 2014 9:51 am Reply with quote
DavidSaunders
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AirGunEric wrote:
I would have to disagree with some of the content posted above- 850fps is not a "barrier" to accuracy- the only 'rule' in that respect is turbulence around the speed of sound- i.e. 1020-ish fps. Accuracy is otherwise going to be dependent on the pellets and barrel being used. I would agree that a springer (and the more powerful the springer, the more so) is the most difficult gun to master, if a person understands that and works to become a good shooter with one, pretty much every other gun they touch will be almost a joke in respect to becoming a good shooter (the classic statement being if someone can become a solid shooter with a high-powered springer, they can shoot anything else at least as well). It is challenging when first starting, but I don't think this should be a barrier unless someone is impatient or doesn't have the time to practice very often.

Eric sorry to disagree though pellets begin to spiral around 860 to 870 FPS. There has been high speed photography to prove that.
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PostPosted: Sat Mar 08, 2014 10:50 am Reply with quote
bcbuddy
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Good information off the get-go thanks fellas.
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PostPosted: Sat Mar 08, 2014 1:40 pm Reply with quote
AirGunEric
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DavidSaunders wrote:
Eric sorry to disagree though pellets begin to spiral around 860 to 870 FPS. There has been high speed photography to prove that.


If you are talking about end-over-end spiralling, not the appropriate twist spiralling due to barrel rifling, please point us to where this information is to be found so the specific conditions of it can be looked over- the statement, as nothing more than a statement, is fairly meaningless.

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PostPosted: Sat Mar 08, 2014 6:58 pm Reply with quote
Slavia
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Welcome to the forum!

Quote:
you do not want to go past 850FPS, anything faster and you start to loose accuracy

Here's a discussion from a couple of years ago about pellet destabilization starting at mach .80 - .85:
http://www.airgunhome.com/agforum/viewtopic.php?t=7935&postdays=0&postorder=asc&highlight=mach&start=0

Quote:
if someone can become a solid shooter with a high-powered springer, they can shoot anything else at least as wel

I agree with Eric on that one. Springers are simple, require only one cocking stroke, and offer freedom from other "junk" (like pumps, tanks, CO2 capsules, etc.). On the other hand, there is a specific technique and learning curve involved (see "artillery hold"). But hey, the gun takes 500 - 1000 rounds to get broken in, so you've got time to practice.

Quote:
wondering if someone had the tools and the time how difficult would it be to "polish" an air rifle to make it faster

Springer velocity can be increased by increasing the preload on the spring or replacing the spring altogether, but often at the expense of harshness in the firing cycle. Smoothness and accuracy are more reasonable goals. You can polish the muzzle crown,choke the barrel, fit new barrel pivot washers, adjust the pivot tension, de-burr the internal parts, hone the cylinder, button the piston, polish the spring ends, fit more precise spring guides, add thrust washers, change lubricants, hone the trigger parts, or even replace the trigger with an upgrade. And that's just springers - CO2 and pneumatic guns have their own lists of possible modifications.

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PostPosted: Sat Mar 08, 2014 9:09 pm Reply with quote
AirGunEric
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I do recall that discussion, and the talk of the transonic region and some extra buffeting- but I don't believe "spiralling" was ever on the table (this would seem to be dependent on the specific pellet being used). It was noted that less accuracy can be present when in this region, but even Bob's experience indicated it was closer to 950fps where this became an issue, not 870fps- so I will point again (assuming such a thing was photographed at 870fps) that the specific pellet/design is relevant.

All that being said, and along these same lines, has anyone ever fully tested a pellet flight path through the transonic area (i.e. through, above, and back down)- it would seem to make sense that as it is the same conditions for each shot, that the end result should be consistent, even if the end result is not what was fully expected. I am wondering if anyone has ever tested this properly over a longer distance-?

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PostPosted: Sat Mar 08, 2014 9:33 pm Reply with quote
DavidSaunders
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I am looking for the references. Though there are certain constants that effect the spiraling regardless of pellet. Obviously some pellets will have a better time of it though all will loose accuracy do to spiraling.
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PostPosted: Sun Mar 09, 2014 8:50 am Reply with quote
Slavia
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Perhaps "spiral" is an imprecise choice of words. To me, spiral means a helical flight path due to nutation (gyroscopic precession of the longitudinal axis). Flipping end for end might better be described as "tumbling" in flight or "keyholing" at the target. I agree with Eric that such a rotation about a transverse axis would be more a function of the pellet design and gun. To my mind transonic instability doesn't imply "sprialing," "flipping," or "tumbling." It's the disturbance of the pellet's longitudinal axis (and flight path) due to "buffeting." That buffeting being caused by the pressure differential with a shock or pressure zone forming and dissipating asymmetrically and randomly as the pellet passes through the transonic region.

870 vs. 950 and semantics aside, the practical application is simply to use the pellet that gives the best accuracy in a particular gun. Moving to a heavier subsonic pellet might satisfy that end.

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hello from B.C. 
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