# Confusing velocities during conical testing



## krucker26 (Mar 9, 2009)

My friend and I are planning a muzzleloader hunt in CO this season for elk and mule deer. We bought several different conicals and went shooting this past Saturday. However, neither of us can explain the results. We were tracking velocites and shooting 100 yard groups. The 2 test guns were a TC Triumph and a TC Endeavor. Both guns are .50 cal and have 28" barrels. The Triumph has a slightly tighter bore (observed through loading). We both were shooting Blackhorn 209 powder with CCI primers. Our loads were identical in every way however the Endeavor consistently achieved much higher velocities than the Triumph. Can anyone explain the observed disparity in velocity. See selected data below? C

80 g. Blackhorn 209 w/ 460 g. No Excuses Conical
Triumph = 1400 fps
Endeavor = 1750

80 g. Blackhorn 209 w/ 440 g. Parker Industries Hydracon
Endeavor = 1765 fps
90 g. Blackhorn 209 w/ 440 g. Parker Industries Hydracon
Triumph = 1500 fps


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## rogerw (Jan 7, 2008)

Wow, that is interesting. That is not a heavy load of powder, and I would not suspect the plastic sabot failing to seal on the looser loading one....

that was my only thought, but it does not seem likely. If you were shooting above 100gr of that stuff I might begin to suspect that.

Was either gun shooting a significantly better group at 100yds? gas cutting past the sabot seal would probably have a bad effect on the grouping.

[edit] here is a thought....I have had chrony to malfunction and give errors when the light is not just right.....were you using the lightshades properly, or shooting without? Were all the shots mixed during the session or were one gun shot first and then the second under different sun/lighting?

If your chrony light sensor(s) happens to be getting its predominate illumination at an angle (strong source direct to sun0 and not perfectly vertical to the lightshade, it will give you a velocity error. I have seen this happen, they are sensitive to light conditions and setting up properly.

YHS,
rogerw


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## krucker26 (Mar 9, 2009)

These loads were all bore-sized conicals, no sabot involved. Groups were similar but the Endeavor was grouping a little better. The light shades were properly installed and we alternated shots throughout the day. The chronograph was tested with .17 HMR and some .40 pistol ammo. No malfunctions in the chrono were detected.


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## rogerw (Jan 7, 2008)

Good procedure.... I am tapped out on ideas, unless the looser loading one was leaking gas around the boolit, but the other one was achieving a decent obduration and seal.

YHS,
rogerw


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## Plainsman (Jul 30, 2003)

roger, that's about the only thing I can think of also.

Krucker, what is the twist in the two rifles? Do you know if the rifling depth is the same? Also, comparing the rifles what does the fire hole from primer to powder look like in those rifles? Are they the same?


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