GTA
All Springer/NP/PCP Air Gun Discussion General => PCP/CO2/HPA Air Gun Gates "The Darkside" => Topic started by: Smitty8141 on September 03, 2015, 12:54:28 AM
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Just wondering what everyone's thoughts are on what the best long distance airgun would be... The shot would have to be with a pellet. So far my FX Boss .30 is the best I have for shooting long. I have a target at 234 yards and can hit it. I'll post pictures once I have enough posts to be able to post a picture.
What's the farthest others have shot.
Kevin
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This should be interesting. Pellet, may be the .30 since it can buck the wind a little better.
However as the title mentions, "airgun", it may be the .257 cal. bullet. In the Big Bore section under PCP the .257 cal has really been doing well to distances around 700 yards. A lot of .257 rifles are made on the Air Force Condor platform. There are also some videos on U/T that show the .257 being shot at different distances.
I was at the LASSO shoot last Saturday and there was one person there shooting an Air Force Condor SS in .25 cal at 250 yards. His rifle had an 18" barrel. He placed 3rd in Varmint class.
I'm waiting for the SHOT SHOW in January 2016 to see all the new items. I'll make my decision on what I want after the show. I do plan on getting something specifically for long range shooting, just not sure what I want.
Right now I'm shooting a regulated FX Royale 500 .25 cal. I have been shooting at 100 yards easily, just haven't had the time to stretch it out yet. I retire October 1st and I my plans are to have a range day of at least once a week.
Also on the Talon Forum there is a section dedicated to the .257 shooter. Good read if you have the time.
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700 yards, even with a bullet, is amazing for an air rifle.....
Kevin
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700 yards, even with a bullet, is amazing for an air rifle.....
Kevin
700 even in inches is pretty good for some folks ::)
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Here is the link on his write up. http://www.gatewaytoairguns.org/GTA/index.php?topic=95899.0 (http://www.gatewaytoairguns.org/GTA/index.php?topic=95899.0)
If you're really interested look on the Talon forum. There's a lot more over there.
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Airguns for any realistic and practical use shooting PELLETS becomes for fun and giggles at or beyond 100 yards IMO.
Sure they shoot farther ! ... but reliable accuracy and repeatably way out :P ... Not so much.
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The 30cal BT65 that I built shooting at 264 yards put 5 JSB pellets into a 4 inch cluster.
Don't believe guys that discount long range pellet shooting.
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The 30cal BT65 that I built shooting at 264 yards put 5 JSB pellets into a 4 inch cluster.
Don't believe guys that discount long range pellet shooting.
thats some awesome shooting, grouping like that at that range!
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From what I've seen, range goes up with caliber. The most accurate long range pellet gun I've shot is the Flex made by Wicked Air Rifles and it is 30 caliber.
Now if you switch to slugs, the range goes way up too. Have you seen Cedric's videos shooting slugs from his 257 from 200 to 400 yards? Most of his videos are worth watching
https://www.youtube.com/user/tofazfou (https://www.youtube.com/user/tofazfou)
Ray
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The 30cal BT65 that I built shooting at 264 yards put 5 JSB pellets into a 4 inch cluster.
Don't believe guys that discount long range pellet shooting.
That's unbelievable shooting with an air rifle. Can the rifle repeat that performance?
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The King Heavy has a slightly better BC than the 30 cal pellets if the measurements taken are to be believed( and I think they're legit ). A 40 gr boolit in .224 is about double the heavy King and it gets better with the heavier stuff.
cheers,
Douglas
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The 30cal BT65 that I built shooting at 264 yards put 5 JSB pellets into a 4 inch cluster.
Don't believe guys that discount long range pellet shooting.
That is amazing... Once I can post pictures I'll post my shooting at 234 yards. I shot about 12 shots. Group was about 10 - 12 inches. I'll have to measure exactly. So far .30 has been best for me.
Kevin
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Here is a link to the 234 yard target. I'll post more after I see if this works
Kevin
http://i980.photobucket.com/albums/ae286/smitty8141/image.jpg1_zps6oxrcndc.jpg (http://i980.photobucket.com/albums/ae286/smitty8141/image.jpg1_zps6oxrcndc.jpg)
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Now I can post pictures.
Here is my setup
(http://i980.photobucket.com/albums/ae286/smitty8141/image_zps521cb306.jpg)
Here is the view to the target, 234 yards away
(http://i980.photobucket.com/albums/ae286/smitty8141/image_zps335fca32.jpg)
View through the scope, 20x
(http://i980.photobucket.com/albums/ae286/smitty8141/image_zps3cbf0f5e.jpg)
Target after 12 shots
(http://i980.photobucket.com/albums/ae286/smitty8141/image.jpg1_zps6oxrcndc.jpg)
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Kevin,
Thats real cool. Love it. The 1st thing that caught my eye in your target pic is the shape of the holes of the pellets. They show me that they pellet really have some ARC and are coming DOWN into the target.
Good shooting.
While i'm a firm believer of using bullets/slugs for long range, the pellet can reach out there. REACHING out there with a pellet is a fact and its good to see ANY TYPE airgunner reaching out................
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Thanks..... According to Chairgun the poi is 18 feet above the target. That is a serious drop.
Kevin
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The 1st thing that caught my eye in your target pic is the shape of the holes of the pellets. They show me that they pellet really have some ARC and are coming DOWN into the target.
That sounds a bit far fetched to me.... At 250 yards a JSB .30 cal pellet shot at 900 fps would be dropping 2" per yard.... or about 0.056" per inch of travel.... The pellet is about 3/8" long, so the path through a piece of paper would be oval by about 0.020".... You shouldn't even be able to see that....
If the pellet was flying nose up the whole way, the difference between the boreline and the impact path (trajectory) at that range is less than 5*, so again, the hole in the paper should be nearly round.... about 0.030" out of line with the trajectory.... Even the two things added together are less than 1/16"....
However, I've never shot at 200+ yards, so I guess something weird could be going on.... :-\
Bob
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The 30cal BT65 that I built shooting at 264 yards put 5 JSB pellets into a 4 inch cluster.
Don't believe guys that discount long range pellet shooting.
That's unbelievable shooting with an air rifle. Can the rifle repeat that performance?
Hoping the rain stops tomorrow and I will see what she does.
Bought some carbon fiber tube and added that to the barrel.
Will report back asap.
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Bob,
I'm hoping to get out this weekend again. I'll run another target out at 234 and shoot another group or two. I shoot at 207 also and the holes in the paper are elongated just like at 234. I don't know the actual drop, I can only report what Chairgun says. I can tell you that I have my scope elevated in the rear far enough that the barrel is shooting well above the target. I'm hoping to stretch to 250 as soon as I get a chance. Unfortunately my FX Boss has developed a leak near the air gauge. Hopefully it doesn't get worse before I get a chance.
Kevin
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Kevin, would you confirm what chair gun gives for mine?
Sighted in for 50 yards. Velocity is 850 iirc. 264 yards the point of aim is 18 ft above impact.
See if that jives with chairgun. 44 gr JSB pellets.
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Voltar1,
Assuming I'm using the right BC, I show a POI of 278 inches, which is 23 feet. It's sounds close. Your shooting 30 more yards are your velocity is 20 ft/s slower than mine. It's showing a velocity of 366 ft/s at 264 with 13 ft.lb of energy.
It's amazing that these pellets seem to be staying relatively stable dropping from that distance.
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I have a BC of 0.040 (GA Model) for the .30 cal JSBs at 850 fps.... Sighted at 50 yards, ChairGun says 214.07" of drop (17.8') at 264 yds and 211.90" at 263 yards, so the pellet is dropping 2.17" in the last yard, or just 0.060" in the last inch of travel.... which works out to 3.44*.... The boreline at 264 yards is 40" above horizontal, making the total drop from boreline 254" (just over 21 feet).... 264 yards is 792 feet, or 9504 inches, so the angle is inv.sin(254/9504) = inv.sin(0.0267) = 1.53*.... If the bullet is still nose high, parallel to the boreline, it will be tearing though the paper at just under a 5* angle.... That would make the hole in the paper 0.033" taller than it is wide, for a pellet that is 0.38" long.... The pellet would be travelling 488 fps and still have 23.6 FPE of energy at 264 yards.... A 1 mph crosswind would drift the pellet 5.65"....
Bob
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18 ft is right on then? Wow that is cool.
So the Bushy rangefinder must be accurate as well as the mildots of my scope. Coolbeans.
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Yup, looks like the BC is right on with your field results.... Using 0.039 it is slightly over 18 feet instead of slighty under (GA Model)....
Bob
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I have a BC of 0.040 (GA Model) for the .30 cal JSBs at 850 fps.... Sighted at 50 yards, ChairGun says 214.07" of drop (17.8') at 264 yds and 211.90" at 263 yards, so the pellet is dropping 2.17" in the last yard, or just 0.060" in the last inch of travel.... which works out to 3.44*.... The boreline at 264 yards is 40" above horizontal, making the total drop from boreline 254" (just over 21 feet).... 264 yards is 792 feet, or 9504 inches, so the angle is inv.sin(254/9504) = inv.sin(0.0267) = 1.53*.... If the bullet is still nose high, parallel to the boreline, it will be tearing though the paper at just under a 5* angle.... That would make the hole in the paper 0.033" taller than it is wide, for a pellet that is 0.38" long.... The pellet would be travelling 488 fps and still have 23.6 FPE of energy at 264 yards.... A 1 mph crosswind would drift the pellet 5.65"....
Bob
Can't you just say that an over stabilized pellet will not follow trajectory (the nose leading the flight path) and is "dang" near key holing... :D
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What I'm saying is that the strange shaped holes in the target cannot be, IMO, from the bullet "dropping" into the target paper, there must be another reason.... Even if the nose of the bullet was still flying on the same angle above the horizon it was launched on, the hole in the target would only be 0.033" taller than it is wide.... "Overstabliized" to me, means that the bullet is spinning way faster than it needs to, so the nose is staying on the original course.... When it happens to artillery shells that are fired on a high angle, they don't land nose first, which is why the Military use Stability Factors between 1.5 and 2.5....
There may be some factor of Dynamic Instability involved that is causing the strange impact marks.... It might take high speed photos to find out exactly what is happening.... However, it can't be just the bullet dropping into the target, the angles just aren't great enough....
Bob
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Bob,
I can tell you that at 100 yards the holes are perfect. Unfortunately I don't have any way to put a target between 100 yards and 207 yards. I have a 100 yard range straight off my patio. To shoot farther I shoot across the mucky lake you see in the picture. Shortest is 207 yards, so far longest is 234. Also, the Boss has a smooth twist barrel. I would think the pellet is spinning slower, just a guess. Maybe that has something to do with the holes. BC for the .30 pellet in the FX is .035.
Kevin
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The 30cal BT65 that I built shooting at 264 yards put 5 JSB pellets into a 4 inch cluster.
Don't believe guys that discount long range pellet shooting.
One time...
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What I'm saying is that the strange shaped holes in the target cannot be, IMO, from the bullet "dropping" into the target paper, there must be another reason....
There may be some factor of Dynamic Instability involved that is causing the strange impact marks.... It might take high speed photos to find out exactly what is happening.... However, it can't be just the bullet dropping into the target, the angles just aren't great enough....
Bob
There is. When the bullet gets significantly off line of travel drag further displaces it. That is when you start to get key holeing with the tip of the bullet high due to stabilization. The holes are oval because the bullets are hitting tip high. The bullets are hitting tip high because of the effects of drag. They were launched at nearly double the speed of impact. They probably had a 50 foot rise to line of sight. The math is non-linear, it would probably be modeled with a quadratic equation. That bullet is right at the raged edge of turning backwards.
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W "Overstabliized" to me, means that the bullet is spinning way faster than it needs to, so the nose is staying on the original course.... When it happens to artillery shells that are fired on a high angle, they don't land nose first, which is why the Military use Stability Factors between 1.5 and 2.5....
Bob
Bob, I suppose that is true but what we are looking at here is probably what you are calling over stabilisation. Who is building a barrel today that is intended to shoot to 200 yards at sub Mach I velocities with anything, let alone a .257 bullet?
I think the barrel is probably a one in ten maybe one in fourteen MAX. We have this large, long, slow boolit, traveling down range subsonic. End result is it is trying to flip over backwards, tip high.
Shoot it another 40 or 50 yards and see what you get.
Just my two and admittedly I did not bother with any math... so... SWAG =)
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Just my two and admittedly I did not bother with any math... so... SWAG =)
I love Scientific Wild A** Guesses! ;)
Seeing as a slo-mo camera is a costly item, might I suggest a stack of scrap wallboard, block of clay/duct seal, stack of cardboard, or ballistic gelatin to catch the projectile at it's last attitude?
Having pulled many a target at the 800, 900 and 1000 yard lines, I have seen numerous .30 cal. holes in the 2"x4" target stands at rather steep/unusual angles.
I was also led to believe that airgun shooting at reduced distances was supposed to mimic this.
Cheers,
Smoketown
Edit - Spellun'
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The 30cal BT65 that I built shooting at 264 yards put 5 JSB pellets into a 4 inch cluster.
Don't believe guys that discount long range pellet shooting.
One time...
Hope not :-)
BTW, how many times have you done 'it'?
Going to give it a go tomorrow. Weather should let up by then
Cheers
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W "Overstabliized" to me, means that the bullet is spinning way faster than it needs to, so the nose is staying on the original course.... When it happens to artillery shells that are fired on a high angle, they don't land nose first, which is why the Military use Stability Factors between 1.5 and 2.5....
Bob
Bob, I suppose that is true but what we are looking at here is probably what you are calling over stabilisation. Who is building a barrel today that is intended to shoot to 200 yards at sub Mach I velocities with anything, let alone a .257 bullet?
Just to clarify. The target pictures were shot with a .30 pellet from an FX Boss with a smooth twist barrel. The target was at 234 yards.
Kevin
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As I said, the math for the pellet hitting on an angle due to excessive drop just doesn't add up.... On the other hand, since we're talking an FX with a smooth twist barrel, it is entirely possible that the pellet is understabilized, and on the verge of tumbling.... therefore hitting nose up, which would explain the smeared top and sharp, circular bottom (creating a pear shape) on some of the holes at 234 yards.... I saw one measurement of the spin rate on a pellet from an FX that showed the pellet was only rotating 1 turn in 13 FEET....
There are several very good programs for calculating the required twist, and the better ones deal with subsonic velocities just fine.... The .300 AAC Blackout shoots 200 gr. bullets at 1050 fps, and is very accurate out to 600 yards in an 8" twist.... so the technology certainly exists, and is pretty well known.... Several GTA members have produced spectacular results out to 400 yards, and bullets aren't tumbling as far out as 700.... but with bullets, not pellets, of course....
Bob
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Bob,
Tomorrow I'm going to run around the lake and pull some of the pellets out of the wood that the target sits on. I'll post pictures of them. Maybe we can see entry angle into the wood.
Kevin
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The 30cal BT65 that I built shooting at 264 yards put 5 JSB pellets into a 4 inch cluster.
Don't believe guys that discount long range pellet shooting.
One time...
Hope not :-)
BTW, how many times have you done 'it'?
Going to give it a go tomorrow. Weather should let up by then
Cheers
Most likely it is a one time event or one in 100 groups. I dont think hes trying to get under your skin but its obvious that you are using one group at extended range to say dont discount long range pellet shooting and one group doesnt show anything. Try shooting 20 groups of 5 shots at 264 yards and see what the average group size turns out to be. I am not saying it cant happen but its unlikely you will retain a 4" average at that distance with pellets. Good luck and post the results.
Weather should let up by then
Why wait on weather? I think that would be the best way to prove you can get long range results with pellets. I almost never have calm conditions to shoot in and this is one reason people discount the long range ability of pellets. In real world conditions at ranges beyond their design pellets will have problems with even the slightest breeze. Chairgun says that a .22 JSB heavy that starts out at 835 fps will get pushed over 8" at 265 yards in a 1 mile an hour cross wind.
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;D Long range shooting with a pellet rifle is challenging at anything over 100 yards to date my best is 6 out of 10 shots at a 7" circular saw blade at 110 yards with my Daystate Huntsman Regal XL .25 and my Evanix RS II .22 5 hits out of ten on the same target. Funny thing is there was a guy doing it with a .177 RAW HM Target with a pro tune
PS He out shot me all day and even let me play with it for about 20 shots, the trigger was super light ~ 5 oz and he had a Leopold 4x12x ? not sure what the objective lens was
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This shooting I am telling about is the first attempt at that distance
I shot three hail mary shots then finally saw the dust kick. Reduced the power
to 8x so i could shoot and watch the hits. Took five shots at the chosen poa
Pleased as punch to watch them land. I expect this rifle to repeat that easy
when it is NOT just a five shot group selectively chosen to brag about. I woul
email pics to anyone handy at posting here.
Weather permitting......
I doubt any of you would be shooting for groups in the high mountains
in a driving rain storm on the verge of snow.
Today is much nicer but I cannot see the hits in the mud.
Cheers
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enjoy the pics, 204 yds , jsb 18 grns, 885 fps (http://[url=http://i1353.photobucket.com/albums/q674/plinker81366/image.jpg2_zpsspbbxfmr.jpg]http://i1353.photobucket.com/albums/q674/plinker81366/image.jpg2_zpsspbbxfmr.jpg[/url])
(http://[url=http://i1353.photobucket.com/albums/q674/plinker81366/beb77dcf-ff89-4d38-9895-2d55bc068db4_zpswmzzbpap.jpg]http://i1353.photobucket.com/albums/q674/plinker81366/beb77dcf-ff89-4d38-9895-2d55bc068db4_zpswmzzbpap.jpg[/url])
(http://[url=http://i1353.photobucket.com/albums/q674/plinker81366/image.jpg1_zpsmucumkak.jpg]http://i1353.photobucket.com/albums/q674/plinker81366/image.jpg1_zpsmucumkak.jpg[/url])
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This shooting I am telling about is the first attempt at that distance
I shot three hail mary shots then finally saw the dust kick. Reduced the power
to 8x so i could shoot and watch the hits. Took five shots at the chosen poa
Pleased as punch to watch them land. I expect this rifle to repeat that easy
when it is NOT just a five shot group selectively chosen to brag about. I woul
email pics to anyone handy at posting here.
Weather permitting......
I doubt any of you would be shooting for groups in the high mountains
in a driving rain storm on the verge of snow.
Today is much nicer but I cannot see the hits in the mud.
Cheers
I guess I dont understand that comment. Why do you need to see the hits in mud? Why do you even need to see the hits? It seems like it would be easy to put a target up at 264 yds and shoot some groups. You say that you can repeat the 4" 264 yd group easy so lets see it. As far as I am concerned thats a very bold statement to make so I need to see multiple groups on paper that show that. Like I said if you can and do make 4" consistent groups at 264 yds with pellets great shooting.
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(http://[url=http://i1353.photobucket.com/albums/q674/plinker81366/image.jpg2_zpsspbbxfmr.jpg]http://i1353.photobucket.com/albums/q674/plinker81366/image.jpg2_zpsspbbxfmr.jpg[/url])
(http://[url=http://i1353.photobucket.com/albums/q674/plinker81366/image.jpg1_zpsmucumkak.jpg]http://i1353.photobucket.com/albums/q674/plinker81366/image.jpg1_zpsmucumkak.jpg[/url])
204 yds jsb 22 18 gr. @885 fps
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This shooting I am telling about is the first attempt at that distance
I shot three hail mary shots then finally saw the dust kick. Reduced the power
to 8x so i could shoot and watch the hits. Took five shots at the chosen poa
Pleased as punch to watch them land. I expect this rifle to repeat that easy
when it is NOT just a five shot group selectively chosen to brag about. I woul
email pics to anyone handy at posting here.
Weather permitting......
I doubt any of you would be shooting for groups in the high mountains
in a driving rain storm on the verge of snow.
Today is much nicer but I cannot see the hits in the mud.
Cheers
Wow, great shooting and a great rifle. I need to remind myself what people were doing with muzzle loading BP rifles sometimes I just forget my history.
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The 30cal BT65 that I built shooting at 264 yards put 5 JSB pellets into a 4 inch cluster.
Don't believe guys that discount long range pellet shooting.
One time...
Hope not :-)
BTW, how many times have you done 'it'?
Going to give it a go tomorrow. Weather should let up by then
Cheers
Brother, I've never done it. I would be proud to be able to say I had. In my youth I could do it with an M16 with the stock peep though, which is probably easier in many respects than what you have done. Well shot. I also hope it is not the only time.
The thread is interesting and I'd like to hear more about your exploits. It will be very cool if you manage to do it with regularity even if you have to pick your weather.
This is one of the reasons that a 10 shot group actually gives us 3 times as much data than a 5 shot group.
With at 10 shot group you get 9+8+7+6+5+4+3+2+1=45 data points. With a 5 shot group you get 5+4+3+2+1=15 data points. This happens because you can consider the distance between each pair of shots a data point. Essentially you will find that seven shots is the minimum shot count which will give you a high probability of defining what the rifle/shooter/pellet combination is actually doing. There are 28 pairs of shots in a seven shot group. This is true only if you shoot only one group. The average of two five shot groups is pretty indicative of what the system is actually doing because there are 30 data points in two five shot groups.
Anyway the "Shrimp on the Barbie" so.... later.
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This rifle is a BT65 Hatsan worked over and converted to 30cal
Made a singleshot receiver and fit a TJs barrel using specs by Rsterne and SMP
I have added a carbon fiber sleeve friction fit over barrel
Plan to epoxy the two pieces eventually.
Will be shooting 100 yards this Thursday with a buddy that has the Daystate Wolverine
See how we do then :-)
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Far from the impressive results from others but I have gone out to 150 yards with a stock mrod.
Video
(http://i664.photobucket.com/albums/vv5/qvideo/Mobile%20Uploads/th_VID_20150901_130018_454_zpsfvvwz2yu.mp4) (http://i664.photobucket.com/albums/vv5/qvideo/Mobile%20Uploads/VID_20150901_130018_454_zpsfvvwz2yu.mp4)
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Here is a picture of a pellet that was shot in my pictures in the beginning of this topic. 234 yards, .30 cal, shot from FX Boss. Pellet was embedded in 1/2" plywood.
(http://i980.photobucket.com/albums/ae286/smitty8141/image.jpg1_zpsw6prglme.jpg)
Holes are elongated, tough to tell entry from pellet.
Kevin
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I would say the "crater" on the left of the pellet head in that photo is the impact point.... with the striations running at about 90* to that as it penetrated the plywood backstop at roughly a 45* angle.... We know the pellet is NOT coming down into the target at a 45* angle, so that leaves us with the conclusion that it is hitting the target yawed nearly 45* to it's line of flight.... ie on the verge of tumbling.... Since the pellet is falling through the air at some angle of attack (at least 5*) then it would make sense that there is lift being generated by the round nose, lifting it further (increasing the angle of attack / upwards yaw) because of insufficient gyroscopic stability (RPM), and the pellet is in the process of starting a back-flip.... JMO, of course....
Bob
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I would say the "crater" on the left of the pellet head in that photo is the impact point.... with the striations running at about 90* to that as it penetrated the plywood backstop at roughly a 45* angle.... We know the pellet is NOT coming down into the target at a 45* angle, so that leaves us with the conclusion that it is hitting the target yawed nearly 45* to it's line of flight.... ie on the verge of tumbling.... Since the pellet is falling through the air at some angle of attack (at least 5*) then it would make sense that there is lift being generated by the round nose, lifting it further (increasing the angle of attack / upwards yaw) because of insufficient gyroscopic stability (RPM), and the pellet is in the process of starting a back-flip.... JMO, of course....
Bob
You could be absolutely right. I've never dug a pellet out of such a long distance shot. The smooth twist barrel is interesting. Slow spin rate, but very stable flight to 100 yards. After 100 I have no way to see it. I have never seen the pellet spiral.
Kevin
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I don't doubt that the pellet doesn't spiral.... I firmly believe that spiraling is caused by Dynamic Instability, which is most often caused by over-spinning the pellet/bullet.... With the extremely low RPM reported for pellets shot from the FX Smooth Twist barrels, I would think the most likely thing to occur is exactly what we may be seeing here.... Once the velocity slows to the point that the skirt can't keep the nose into the direction of travel then the lack of gyroscopic stability takes over and the pellet should start to do a backflip....
Bob
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I don't doubt that the pellet doesn't spiral.... I firmly believe that spiraling is caused by Dynamic Instability, which is most often caused by over-spinning the pellet/bullet.... With the extremely low RPM reported for pellets shot from the FX Smooth Twist barrels, I would think the most likely thing to occur is exactly what we may be seeing here.... Once the velocity slows to the point that the skirt can't keep the nose into the direction of travel then the lack of gyroscopic stability takes over and the pellet should start to do a backflip....
Bob
You got it in one. I want to see groups at fifty yards further. It could be telling.
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I firmly believe that spiraling is caused by Dynamic Instability, which is most often caused by over-spinning the pellet/bullet....
In that regard, Bob, I think that it is caused by skirt deformation more that any other of many possible reasons. Why? because I see soft skirted pellets spiraling when I don't see hard skirted pellets spiraling. It is something to think about, not necessarily something to write on your bible.
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Dynamic Instability is so complex they really can't even model it properly.... They know some of the causes, but the way they interact is almost impossible to predict.... Generally, however, if a given bullet spirals, if you slow down the twist rate, it no longer does so at the same velocity.... The best explanation I have seen for why a pellet starts to spiral some distance out from the muzzle is that the velocity slows down faster than the spin rate.... If a pellet starts out at 700 fps, in a 12" twist, it's rotating 700 rev/sec, or 700 x 60 = 42,000 RPM.... Let's say that combination doesn't spiral.... The same pellet, starting out at 900 fps, same twist, is rotating at 54,000 RPM.... It also may not spiral at that combination.... However, if it starts at 900 fps, and 56 yards out it's going 700 fps, it may still be rotating at 52,000 RPM.... and that combination is Dynamically Unstable and the pellet starts to spiral.... Slow the twist rate down to 14", and it's only rotating 46K at the muzzle and 45K at 60 yards, and that combination is stable.... A different pellet will have different parameters where it is Dynamically Stable or Unstable.... Note this is completely different than Static (Gyroscopic) Stability, which is what keeps a bullet from keyholing/tumbling.... If you make the twist rate too slow for a given bullet, then it becomes Statically Unstable.... Too high a twist rate and it will fly nose up (parallel to the boreline) all the way to the target (Statically Overspun)....
Bob
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I have a BC of 0.040 (GA Model) for the .30 cal JSBs at 850 fps.... Sighted at 50 yards, ChairGun says 214.07" of drop (17.8') at 264 yds and 211.90" at 263 yards, so the pellet is dropping 2.17" in the last yard, or just 0.060" in the last inch of travel.... which works out to 3.44*.... The boreline at 264 yards is 40" above horizontal, making the total drop from boreline 254" (just over 21 feet).... 264 yards is 792 feet, or 9504 inches, so the angle is inv.sin(254/9504) = inv.sin(0.0267) = 1.53*.... If the bullet is still nose high, parallel to the boreline, it will be tearing though the paper at just under a 5* angle.... That would make the hole in the paper 0.033" taller than it is wide, for a pellet that is 0.38" long.... The pellet would be travelling 488 fps and still have 23.6 FPE of energy at 264 yards.... A 1 mph crosswind would drift the pellet 5.65"....
Bob
Bob,
You seriously have too much time on your hands sir...................lol! Take it lightly Bob ;D
You have a formula for telling how much TEAR would be in paper if a PELLET DROPS into a target or if its just unstable? LoL.....just giving you a hard time
Sorry, but i simply figured that a 30 cal pellet at a lowly 850 fps shooting 260 plus yards would have some slightly DOWNWARD angle (no sir, not 45 degrees) as it comes into the paper target which can make those long tears. So can instability which i already knew about ST barrels. I didn't even consider the barrel was a ST.
Would really love to see some HD video of this slug travelling to the target.
Good stuff though...................
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Dynamic Instability is so complex they really can't even model it properly.... They know some of the causes, but the way they interact is almost impossible to predict.... Generally, however, if a given bullet spirals, if you slow down the twist rate, it no longer does so at the same velocity.... The best explanation I have seen for why a pellet starts to spiral some distance out from the muzzle is that the velocity slows down faster than the spin rate.... If a pellet starts out at 700 fps, in a 12" twist, it's rotating 700 rev/sec, or 700 x 60 = 42,000 RPM.... Let's say that combination doesn't spiral.... The same pellet, starting out at 900 fps, same twist, is rotating at 54,000 RPM.... It also may not spiral at that combination.... However, if it starts at 900 fps, and 56 yards out it's going 700 fps, it may still be rotating at 52,000 RPM.... and that combination is Dynamically Unstable and the pellet starts to spiral.... Slow the twist rate down to 14", and it's only rotating 46K at the muzzle and 45K at 60 yards, and that combination is stable.... A different pellet will have different parameters where it is Dynamically Stable or Unstable.... Note this is completely different than Static (Gyroscopic) Stability, which is what keeps a bullet from keyholing/tumbling.... If you make the twist rate too slow for a given bullet, then it becomes Statically Unstable.... Too high a twist rate and it will fly nose up (parallel to the boreline) all the way to the target (Statically Overspun)....
Bob
All of that is very true. Spin rate tends to stabilize even malformed projectiles as it increases. This was documented by DoD people a life time ago. That makes me rethink my assertion that it might have to do with malformed skirts. What is changing? Velocity is changing much faster than angular rotation. Do they spiral in agreement with the rifling or against it? That might be worth knowing. It is an interesting problem. It may be that there is a clue in how frequently spiraling correlates to the direction of the twist in rifling.
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Although I have shot 234 yards a few times. I just shoot at a paint tray. I can hit it 9 out of 10 times if the wind is very light. The tray is 12" x 16". The target I posted was the first time I had put a target out their. Had to pay my daughter to run around the lake and hang the target. The group is large, but it's definitely a group. I will try to stretch to 250 yards this weekend. That should give us an idea if the pellet is destabilizing. If the pellet is beginning to tumble, I won't be able to get a group at 250.
Kevin