Best long distance airgun

[plinker81366]

204 yds jsb 22 18 gr. @885 fps

[MicErs]

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.

[MicErs]

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.

[Voltar1]

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 :-)

[Jmorris]

Far from the impressive results from others but I have gone out to 150 yards with a stock mrod.

Video

[Smitty8141]

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.



Holes are elongated, tough to tell entry from pellet.

Kevin

[rsterne]

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

[Smitty8141]

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

[rsterne]

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

[MicErs]

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.

[MicErs]

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.

[rsterne]

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

[Tofazfou]

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

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...................

[MicErs]

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.

[Smitty8141]

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