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PostPosted: Mon Jun 26, 2017 11:21 am 
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Joined: Sat Nov 05, 2016 10:52 am
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Location: Caronport, Saskatchewan
Hi, just wondering if chairgun or some other calculator can figure out the variation on target depending on the fps change? I'm wondering how to figure out what an acceptable shot string would be on an unregulated gun. For example what would be the pellet spread be at 35 yards, in a gun shooting a string from 800fps up to 870 fps with 14.3g? If such a calculator exists or if chairgun does this somehow, that would be super!
Another question - I need to know the volume of the qb78 tube in order to figure out efficiency of the gun using Sikes calculator. Anyone know?
Thanks

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PostPosted: Mon Jun 26, 2017 3:58 pm 
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Location: Caronport, Saskatchewan
I found the answer to my last question, still hoping to get an answer to my first. The volume of a stock qb78 tube plus the volume of a modded valve is around 46 or 47 cc, according to Bob Sterne, on a post I found (not confirmed by him personally as of yet, but I assume this is accurate).

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PostPosted: Mon Jun 26, 2017 11:39 pm 
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Location: Winnipeg, Canada
If you are above 800, a 70 fps variation won't be that much at 35 yds.
If I remember correctly, shooting down from 760 to 680 resulted in a p.o.i. shift of about 0.20" on centers at 25 yds with the jsb heavy.
I think that works out to a bit over a minute of angle at 100- could be more.
A good excuse to do the work at the target board, no? :mrgreen:
I'm itching for the pit again. Likely head out Friday if no rain.

-D.S.

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PostPosted: Mon Jun 26, 2017 11:45 pm 
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Location: Caronport, Saskatchewan
Thanks! That's not much variation. Yep, I think I am going to get up really early tomorrow and try and get some shooting in outside town here.

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