Has anyone else with a 17 HMR ever checked to see just what kind of velocity you are really getting from your rifle?

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Has anyone else with a 17 HMR ever checked to see just what kind of velocity you are really getting from your rifle?

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The 28" barrel on the Ultra Lux CZ rifles are slower than the shorter ones.

A hot barrel will affect the burn rate of some powders, some more and some less. This can account for a possible increase in velocity. However, even taking that into account it does not explain the higher velocity the first 3 or 4 shots from a cold barrel.When the barrel heats up, it changes the muzzle velocity.

Running the rounds through the Savage with a 22 inch bull barrel also shows speeds far above the factory speeds.I would think the factory used a 22 or 24" for testing velocity.

Found an article by Chuck Hawks on testing different brands of 17 HMR ammo and his results pretty much parallel my findings. Kind of dispells the rumor also that all 17 HMR ammo is loaded by the same company but only branded differently.

- CCI - high 2613 fps; low 2517 fps; extreme spread 96 fps; average = 2559 fps.
- FEDERAL - high 2631 fps; low 2539 fps; extreme spread 92 fps; average = 2595 fps.
- REMINGTON - high 2626 fps; low 2591 fps; extreme spread 35 fps; average = 2609 fps.
- HORNADY - high 2698 fps; low 2621 fps; extreme spread 77 fps; average = 2658 fps.

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If the sample size were small and the standard deviation was large. Sample variation might account for your discrepancies.

Can you tell me how many rounds you used to generate your numbers? The raw data would be better.

A google search showed me that a higher than advertised speed is normal for the 17 HMR. Some shooters found the speed to be as advertised, some found them higher as I did but none found the speeds lower than advertised. I was simply surprised to discover this but now I know......

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If we approximate the Standard deviation using the range we get 14.5 fps.

Using a 95% level of confidence, we can compute the margin of error on your sample mean. That is plus or minus 9 fps. That is, your measured muzzle velocity average is probably no more that 9 fps more than the actual average muzzle velocity.

That completely supports your conclusion that the advertised muzzle velocity is incorrect.

I fully suspect that the calculated margin of error would be much less using a more accurate number for the standard deviation. This only makes your conclusion stronger.

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