FPS standard deviation of 57. Is somethings wrong?

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Photobug

Member
Feb 10, 2021
15
4
57
Wyoming
I just purchased my second Dan Wesson 715 pellet replica. The first one I got was not right, I had to raise the sight by 6" to hit paper and it would knock over an empty aluminum can but would not penetrate it or barely dent it. After 2 CO2 cartridges through it I assumed it was a lemon and sent it back and ordered a replacement and spent the $10 to get a 10 for 10 test to have it tested before shipping.

The results from the 10 shot chrony test makes me wonder if I got another lemon. The gun is rated at 430 fps max but the testing showed
Min 166 fps
Max 369 fps
Average of 263 fps
Standard Deviation of 57

Besides not getting to the max fps out of it, my biggest concern is the lack of consistency.

The sheet lists bullet weight as 7, I assume a 7 grain pellet. The shots were over a 3 minute period with 11 shots. 4 in the first minute then 3 and 3.

the numbers were
284
205
290
251
283
287
206
166
369
334
227

I don't own a chrony so can't test it, beyond seeing how it groups.
Should I send this one back right now or try it out first?
 
Sqwirlfugger57 said:
Its the first 10 shots off of a fresh CO2 cartridge and a $120 pistol. The numbers are going to be wonky. Does it shoot ok?
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I haven't shot it yet. The last one was so bad, both underpowered and inconsistent. I will try and shoot it to see how it does. It is mostly for can plinking while camping, so don't need precision but would like it to be somewhat accurate. If a number of shots made it more consistent I am willing to try but since I don't have a chrony, not sure if it gets more consistent with time. The only way to test it is to see how far it sends an aluminum can.

Maybe time to get a chrony?
 
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A chrono is a really great tool to have. I would say it’s essential.

A little perspective on airgun and tuning. For rimfires, a standard deviation of 40 FPS is an excepted value for precision set ups in 10 shots. This is after tuning for action torque values, head space, barrel length and cartridge sorting for case rim width and weight. We are pretty spoiled with PCP, in most get good tunes are under 15 FPS usually.

I would say for an unregulatored airgun that 57 would be fairly normal. If it shot fairly decent in 20-25 yards in 10 shots.
 
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CoyoteGod said:
A chrono is a really great tool to have. I would say it’s essential.

A little perspective on airgun and tuning. For rimfires, a standard deviation of 40 FPS is an excepted value for precision set ups in 10 shots. This is after tuning for action torque values, head space, barrel length and cartridge sorting for case rim width and weight. We are pretty spoiled with PCP, in most get good tunes are under 15 FPS usually.

I would say for an unregulatored airgun that 57 would be fairly normal. If it shot fairly decent in 20-25 yards in 10 shots.
Click to expand...
Good info thanks.

After a little more research and thinking what I find particularly shocking about the stats are how underpowered the gun tests from the proposed max fps.

I think the true number of an standard decoration of 57 being pretty bad with an average 263fps. That means the fps out of the gun can range 40% from one shot to the next. I have not been able to test it yet, hopefully this weekend.
 
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