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Question for FT shooters using JSB 10.34

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Cannonball

Cannonball

Member
Jul 30, 2020
786
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Tennessee, United States
I would like to shoot the JSB 10.34’s a little faster than typical to help with trajectory. I realize around 880 is a sweet spot for most pellets but wanted a little faster if possible. I was wondering what speed the accuracy fell off to the point it was detrimental for most air rifles. I am using a Taipan Veteran standard and can adjust the speed anywhere I want it under 20 foot pounds to use for Hunter class. With the current limited supply of pellets I was hoping to minimize the amount of testing needed to get this information. I realize that some rifles might be able to do this better than others, I was just wanting to see what everyone’s thoughts were in this. 
 
I would like to shoot the JSB 10.34’s a little faster than typical to help with trajectory. I realize around 880 is a sweet spot for most pellets but wanted a little faster if possible. I was wondering what speed the accuracy fell off to the point it was detrimental for most air rifles. I am using a Taipan Veteran standard and can adjust the speed anywhere I want it under 20 foot pounds to use for Hunter class. With the current limited supply of pellets I was hoping to minimize the amount of testing needed to get this information. I realize that some rifles might be able to do this better than others, I was just wanting to see what everyone’s thoughts were in this.
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Though they can be usefully accurate right at the 935 limit in some guns, my testing shows wind drift increases in my barrels enough to make it a push over the 860-900fps or so that I normally use, I get both higher count and a bit better accuracy with my guns with that pellet at under 900fps. If I were shooting open class, I might even use lower speeds, but for Hunter I don’t because ranging gets too iffy with only 16X mag.


 
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Daystate Wolverine stock from factory, 920 fps with AA 10.3 gr. Shots spot on out to about 65 yards then goes out of control spiralling beyond. Works great for field target.

It didn't like the JSB 10.34 at all, about twice the group size

Only real way to know what your gun likes and best velocity is a lot of time at the range slinging lead.


 
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My Weihrauch .177 Bullpup with a 24 inch barrel hurls them at 985 and shoots one hole groups at 20 yards. It is the most accurate pellet in that rifle, with the Crosman 10.5s nearly as good. I have executed several tree rats at 40 yards and one Woodpecker (he was pecking a hole in my roof) at about 36 yards. Highly recommend this pellet for .177.



As already said, all weapons have their own peculiarities.
 
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I would like to shoot the JSB 10.34’s a little faster than typical to help with trajectory. ... can adjust the speed anywhere I want it under 20 foot pounds to use for Hunter class. ...
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Start at 933fps (20fpe). Work down from there. If there is no significant increase in accuracy at the lower velocities, then shoot it at 933fps.

If you shoot at 880fps, you might get about 10% less wind drift, but you will get about 10% more drop. Are most of your misses because of miss-reading the wind (horizontal-drift) or from ranging errors (vertical-drop)? That also might affect your decision on velocity.
 
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"Are most of your misses because of miss-reading the wind (horizontal-drift) or from ranging errors (vertical-drop)? That also might affect your decision on velocity."

The growing popularity of 13.43 versus 10.34 grain pellets in 20 foot pound FT classes well illustrates Scotchmo's point. Expounding a bit on that excellent point, I'd say that particular (trajectory versus wind-drift) choice is best dictated by severity of wind conditions at any given match, and/or any given venue. However I'd also opine that his statement becomes more poignant and an easier decision the farther One strays below 20 FP power limits.

As a specific example of my point, say your rig only produces 16 foot pounds. Assuming equal accuracy, the substantial trajectory advantages of an 8.44 grain pellet at 920 FPS versus a 10.34 grain at 830 FPS might make the choice between wind-drift and trajectory/ranging-error a much easier decision. 

An even more obvious example would be choosing between 8.44 and 10.34 grain pellets in Pistol Field Target, but I won't belabor my point. 

Great post Scotchmo; but we've come to expect nothing less from you. 
 
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My rifle has no choice but to shoot them at 1001fps (fx 10grain) and it is surprisingly accurate. And its about 3 inch groups at 100yards. 3 holes makes it about 1 inch but the other to open it up 2 more inches both directions.
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But that means you can’t shoot Hunter Class field target, since anything over 933fps with that pellet is over the allowed limit … the thread is regarding Hunter class ft, which has a maximum target distance of 55 yards.

But IF you needed that gun to shoot under 933fps/10.3, its normally not at all difficult to tune those guns to shoot slower.
 
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"Are most of your misses because of miss-reading the wind (horizontal-drift) or from ranging errors (vertical-drop)? That also might affect your decision on velocity."

The growing popularity of 13.43 versus 10.34 grain pellets in 20 foot pound FT classes well illustrates Scotchmo's point. Expounding a bit on that excellent point, I'd say that particular (trajectory versus wind-drift) choice is best dictated by severity of wind conditions at any given match, and/or any given venue. However I'd also opine that his statement becomes more poignant and an easier decision the farther One strays below 20 FP power limits.

As a specific example of my point, say your rig only produces 16 foot pounds. Assuming equal accuracy, the substantial trajectory advantages of an 8.44 grain pellet at 920 FPS versus a 10.34 grain at 830 FPS might make the choice between wind-drift and trajectory/ranging-error a much easier decision. 

An even more obvious example would be choosing between 8.44 and 10.34 grain pellets in Pistol Field Target, but I won't belabor my point. 

Great post Scotchmo; but we've come to expect nothing less from you.
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By coincidence I’ve been experimenting this morning with 13.43gr jsb’s vs 10.3’s for Hunter class. There IS a noticeable difference in wind drift between the two when fired right around 19.5fpe, but the drop is greater with the heavier pellet, and I suspect ranging with only 16X mag might be enough more of a problem to be a deal-breaker for me. I realize some Hunter class guys do shoot only 800fps and do ok, but my old eyes may not be good enough.

I’ll experiment a bit and see if less drift is worth the additional ranging precision i’ll need. It look like 5/8” more drop but 3/4” less wind at typical 5 mph wind using the 13.43 pellet.

A point for the 10.34 is one can sometimes wait for a bit less breeze, but wind or no wind, drop is drop with the 13.43, right?


 
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My rifle has no choice but to shoot them at 1001fps (fx 10grain) and it is surprisingly accurate. And its about 3 inch groups at 100yards. 3 holes makes it about 1 inch but the other to open it up 2 more inches both directions.
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But that means you can’t shoot Hunter Class field target, since anything over 933fps with that pellet is over the allowed limit … the thread is regarding Hunter class ft, which has a maximum target distance of 55 yards.

But IF you needed that gun to shoot under 933fps/10.3, its normally not at all difficult to tune those guns to shoot slower.
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You bring up an interesting point. The 2% rule. 

"Velocity readings may exceed by a 2% margin to account for Chronograph variance."

I've never felt the need to push it, but if somebody was a bit of a gambler (that the chrono used at larger matches/grand prixs reads similar to their own) and had a gun that still shot them well that fast, they could technically go up to 950ish? I think.

2% of 933 is 18.66fps so 933+18.66 = 951.66. 
 
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I've never felt the need to push it, but if somebody was a bit of a gambler (that the chrono used at larger matches/grand prixs reads similar to their own) and had a gun that still shot them well that fast, they could technically go up to 950ish? I think.

2% of 933 is 18.66fps so 933+18.66 = 951.66.
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2% variation between chronographs is the expected threshold that was decided upon. The 2% is to insure that if you really are at 20fpe, you don't get DQ'd by a optimistic chronograph.

If you run an actual 950+fps average, you will get DQ'd more than occasionally. Keep it <=20fpe and your odds of getting DQ'd by an erroneous chronograph are very low. That means you should make sure that the chronograph that you use for tuning to the 20fpe limit is accurate (or even slightly pessimistic).
 
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"A point for the 10.34 is one can sometimes wait for a bit less breeze, but wind or no wind, drop is drop with the 13.43, right?"

I did my own testing when the 13.43s came out too LD, and came to the same conclusion as you based on the venues I was shooting at the time that had enough natural wind breaks to make the choice easy enough. That choice might have been different was I shooting venues back then with as brutal winds as my 30 acre home-place has (where we now shoot EFT).
 
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