Tuning FX Crown MK2 380mm .217 KO slug tune

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Ghostranger169

Ghostranger169

Member
Jun 9, 2019
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Lamont, FL, United States
I have a tune that is consistently accurate to 150 yards for my FX Crown MK2 Chassis 700mm barrel for .217 JSB Knockout slugs, but that thing is a broomstick. I have been struggling to come up with a slug tune for my 380mm Superior STX barrel that is stable/consistent (fewer flyers, consistent week-to-week, etc.) to pest or plink at longer ranges when it is windy. I "stumbled onto" a very stable low velocity tune for shooting slugs out to 125 yards when I switched from shooting pellets to slugs, but forgot to change the power wheel. I've been shooting this tune for 2 weeks and it hasn't changed(lost zero, POI shifts, more flyers, etc.). I shot the following targets at 25, 50, 75, 100, 125 yards over a 2 hour period in a swirling 2 to 8 mph wind. These are representative of the results I've been getting over the past 2 weeks, so I thought I would share.

FX Crown MK2 w/380mm superior stx barrel(twist rate- 1:23.5) w/.25DonnyFL FX moderator

.217 JSB Knockout slugs @ 805fps: 

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Looks good! Looks like a top notch tune! 



I got fed up with my 700mm barrel as well, lol. I got a 500mm shroud from FX for about $80, and got a 500mm superior liner. Also bonded some carbon fiber to the liner. Last I went out, it was shooting griffin 21gr ldc slugs @ 940fps. Had some issues with my reg pressure gauge and couldnt dial it in (should have been shooting much hotter) but the gun was shooting amazing regardless. @72 yards, it was absolutely stacking them.



The carbon tube is supposed to make the gun less tune sensitive. And the superior liner does as well, but tends to do well being shot a bit faster than the older slug liners, in addition. And that is the results I seemed to be experiencing. 😎 So, to convert your 700mm , all you need is the outer shroud tube and a shorter liner.

My 380 barrel is untouched. I love shooting pellets with it anywhere from 650-960fps, it's a real laser.



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Long_Gun_Dallas,

I know what you mean about the Superior liners. Waaay more forgiving and don't get dirty as easy(less frequent need for cleaning). Thanks for the tip on the carbon fiber tube on the 500mm liner. Probably helps with harmonics too? I know moving the spacers around on the liner can affect harmonics/accuracy. As well as, which moderator I used. Especially with heavier slugs and on the longer 700mm barrel. Even with the 380mm, I tried Huggett Astille, FX moderator(empty can), DonnyFL Sumo, Shogun, and Tanto. Different accuracy with each one. Best was with the DonnyFL FX.
 
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Interesting find on the moderators. None I tried on my 700mm barrel improved accuracy over the absence of one. I even tried using my huma moderator in a large number of configurations with no gain over none.

I tend to use an extremely short huma mod 30 on the 380 when hunting . But I've used it at all lengths (they're stackable), and have a factory FX mod (not DonnyFL) that has some cone baffles, and a 25mm extension on it that I'll use. Neither of which I've seen any increase or reduction in accuracy on the 380mm barrel. Not sure why.

The carbon tube should help a lot with harmonics. You can find them in Earnest Rowes custom shop if you're interested. They are an odd size I'm fairly certain he had to have made specifically for him, and this intended purpose. I epoxied it fully, and positioned the 2 supports in a way that I felt comfortable with, and let the tubes maintain fairly long sections (better rigidity) I hadn't seen anyone use the carbon tubes on a superlight barrel system yet, but didn't see any reason not to.






 
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