FX Smooth Twist - Twist Rate for Strelok?

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hollowpoint

Member
Nov 13, 2017
111
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California, United States
Hey guys, I figured I'd post this in here since it's a question related to ballistic calculators/computers. I'm new to using ballistic software, and I'm trying to get Strelok Pro setup on my phone. I have a few setup parameters I wanted to double check with someone more knowledgeable.

1) Twist Rate

Does anyone know what the twist rate is on a fullsize FX Wildcat Smooth Twist barrel in .25 cal? I did some searching and one guy mentioned his Bobcat was 1-32 left hand twist, and another person mentioned he thought it might be closer to 1-40 twist. Assuming either of those numbers are in the ballpark of reality, is this how I would enter 1-32 left hand twist into Strelok?

1531201424_18958246595b4447908db646.12486939_Screenshot_20180709-222053.png


2) Determining Scope Height

I took the following measurements to determine scope height. Was this the right way to go about it?

  • Measure scope diameter and divide by two - 2.21" / 2 = 1.105"
  • Measure barrel/shroud and divide by two - 1.1" / 2 = 0.55"
  • Measure distance from top of barrel shroud to bottom of scope - 0.90625
  • Add them all together to determine scope height - 1.105 + 0.55 + 0.90625 = 2.56" Scope Height



Is there anything else that I might have missed to setup Strelok for airgun use? Thanks for your time!
 
I use Strelok for my long range powder burners and was turned on to Chairgun Pro for airguns. It seems to be a lot more user friendly when using air guns and it's a free download. It also already has a huge database of the most common pellets used. It's fast, easy and accurate. Also, I don't know about your formula for finding scope height but it's much easier to just hold a ruler on the side, center of your barrel and measure to the centerline of your scope. Simple and fast with no math involved.
 
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That twist rate (although probably close) won't work because Smooth Twist (st) is only in the last few inches of the barrel. You should be fine leaving the twist rate at default (12 if I remember correctly).

Scope height and velocity are more important. Yes you calculated your scope height correctly.
 
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That twist rate (although probably close) won't work because Smooth Twist (st) is only in the last few inches of the barrel. You should be fine leaving the twist rate at default (12 if I remember correctly).

Scope height and velocity are more important. Yes you calculated your scope height correctly.
Click to expand...

Thanks Michael, I changed the twist rate back and forth from 32 to 12, and at least out to 150 yards in Strelok...the holdover calculations look the same. Thanks for letting me know that won't work/doesn't make a difference.
 
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I've tried the same thing with my .30 Bobcat, and like @hollowpoint says, it didn't affect holdover at all. I do know that changing the twist rate, along with pellet velocity, affects the gyroscopic stability factor (try changing variables and watch the GSF change). My assumption (question) is if there are algorithms in the app that adjust the amount of hold for windage based on the GSF and BC? Just a thought... Love Strelok Pro by the way.
Mike
 
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