What would you tune to

[Bravo1956]

What do you think the absolute sweet spot in velocity is for a 177 JSB 8.44 or any diablo pellet and the absolute max fps before it becomes unstable?

I am tuning my FlashQE to shoot the 8.44 JSB (it really doesn't like the AA or JSB heavy) and am curious what others have found as the sweet spot for these.

 

[Guest]

750-880fps for a Diabolo shaped pellet.

 

[intenseaty22]

Interestingly enough, I was reading on the Lost Volume FB group the other day and this subject came up. There seems to be the notion out there that the 8.44 should fly at 777. 

Do. Note Tony’s answer: 

 

[Michigander]

There is no simple answer to that question, but I have noticed that increasing velocity can sometimes improve stability, which can improve accuracy, especially in windy conditions. Presumably this is due to higher spin rate at higher velocity. I have found a good indicator of stability to be velocity variation downrange, say at 50 yards. With only marginal stability, one pellet may be stable and the next less stable, giving increased velocity spread.

On the other hand, pellets seem to again become unstable at velocities approaching the speed of sound. My rule of thumb is stay between 800 and 900 fps when shooting at distances over 20 yards. On the other hand, I have gotten some surprisingly good groups at 50 yards from a 300S shooting at only 620 fps. Go figure.

Chuck

 

[mtnGhost]

My jaw hit the floor when I first tested the 18gr AA pellets out of my 700mm Crown at 980fps. I expected them to drift and fall apart in the wind at 100m, but they were accurate (maybe not sub-MOA, but decent enough for the conditions). They were tighter at 920 and no different all the way down through low 800's. 

That said, my best advice to you is test all velocities until you find the height of accuracy before the drag coefficient makes them inaccurate. Often you'll see different velocity sweet spots for a given pellet out of a given rifle, where they're accurate from 820-870, inaccurate from 871-890, accurate again from 891-930, inaccurate from 931-950, etc etc. 

 

[Bravo1956]

mtnGhost, that last sentence is so true, and it is very annoying and frustrating sometimes because of that.

 

[NickNorthGA]

That's the mostest fun part of it lol! But really, I enjoy struggling with air guns for some reason.

 

[AG72]

I have a hatsan 95 that goes his own way and don't listen to any thumbs of rules, it shoots the Crosman Premier domed 7,9gr at over 1020 fps, and it is accurate at this speed... 

 

[bucketboy]

From what I understand a small light fast pellet will loose more of its forward speed quicker than bigger, heavier calibres but the spin rate will not decay as quickly as forward momentum. This ratio increase between spin and speed causes instability. There are many clips on YouTube showing good stability at closer ranges but erratic spirals as the distance increases.

from my experience, if you are shooting at close range less than 25 yards then you can push pellets faster but accuracy drops off markedly the further the target. I tune .177 8.4grn pellets to run between 770 -800fps, I rarely see .177 guns that I consider to be accurate when pellet speed is much above 850fps, even jsb heavies loose the plot around 900fps.

4 shots at 45yards rapid mfr .177 780fps the pellet is one that I pushed into the hole made by the others.



Bb

 

[Bravo1956]

I am going to tune so the top of the curve is around 880, I think that is a good place to start.

 

[Macloaded]

I try to shoot pellets at between 850 and 900 ftps, for example my FX Streamline in 25 shoots jsb kings at 875 and is lights out accurate. My 22 Wolverine R shoots jsb hades at 890 ftps and is also very accurate. I have had both shooting faster but got no improvement in accuracy and very little in trajectory so just felt I was wasting air.