Tuning Crown MK2- 6 projectiles, 4 barrels, 2 calibers, in 1 hour

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Ghostranger169

Ghostranger169

Member
Jun 9, 2019
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Lamont, FL, United States
This is a (somewhat crude/limited) demonstration of some of the possibilities and the flexibility of the Crown. This particular tune is more of a "power" tune. However, by adjusting regulator AND hammer spring pre-tension spring(appropriately), a variety of desired power levels can be achieved to correspond with multiples of your preferred ammo/barrel/caliber choices out of one gun, all by just turning dials and/or changing barrels.

Crown MK2 in synthetic stock-

Tune: Regulator at ~165 bar, Hammer Spring pre-tension screw 2 quarter turns from max. I didn't change these settings, only the Transfer Port(TP) and the Power Wheel(PW) dials.

380mm Superior liner shooting- 

.218 H&N 21g slugs @ 891 fps: TP-High, PW-5

.217 H&N 27g slugs @ 812 fps: TP-High, PW-Max

.22 JSB 18g @ 875 fps: TP- Med, PW-3

.22 FX 16g @ 886 fps: TP-Med, PW-2

1229201303.1610930956.jpg




700mm pellet A liner shooting-

JSB 18g @ 878 fps: TP-High, PW-1

JSB 18g @ 675 fps: TP-Low, PW-5

0117211629.1610932432.jpg




and 700mm pellet A liner shooting:

FX 16g @ 886 fps: TP-High, PW-Min

FX 16g @ 686 fps: TP- Low, PW-5

0117211629_HDR.1610932564.jpg




.25 380mm pellet A liner shooting:

JSB Kings @ 884 fps: TP- High, PW-B

JSB Kings @ 698 fps: TP- High, PW-Min

0117211603.1610932829.jpg




.25 600mm Superior liner shooting:

JSB King Heavy MK1 @ 912 fps: TP-High, PW-5and a half

0117211553a.1610933043.jpg


There is a lot to take in on this target and I did my best to label it. I started with the 380mm Superior barrel shooting .218 H&N 21g slugs in the upper left corner at 75 yards. The last group I shot was directly below the upper left, back with the 380 barrel and H&N 21g slugs again. I switched out barrels/probes/scopes and shot this target in less than an hour. In general, I shot the targets from top to bottom and left to right, although I did skip around a bit.

I have range cards on each barrel/scope combo to assist zeroing. I fired 3 shots to "season" barrel in between ammo changes and took a few sighters to verify POI at given distances. I shot with an FX chronograph on the barrel. It wasn't the point to try to get ABSOLUTE accuracy out of every setup. Just wanted to demonstrate the ease and speed of switching speeds/barrels/calibers with the Crown, and being "in the ballpark" very quickly. 

I originally intended for all shots to be at 75 yards, but there was a 4 to 8 mph headwind and I didn't think I could hit the target at 75 yards with some of the low powered ammo, so I moved the target to 50 yards. Conversely, I moved the target out to 100 yards for some of the higher powered ammo.

0117211825a.1610934199.jpg



 
Just noticed the extremely high reg. pressure. (for factory hammer weight) That might be playing a part in the fantastic accuracy you're seeing. Very low valve dwell time lends to favorable harmonics typically. I know my Crown sees peak output around 130-135 bar. So, you're well past the top of the power curve there. But still decent power likely due to the increased plenum volume.
 
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Long_Gun_Dallas,

Thanks for the input. I know it was a long, somewhat convoluted post with a lot of info to take in. You no doubt have a keen eye for detail.

I tuned this Crown MK2 by setting the TP on High and HS pre-tension screw to 2 quarter turns away from max. Then put the Power Wheel back on(set to max) and began shooting over the chrono. Reg pressure was at ~125bar. I then increased reg(1 quarter turn at a time) while watching fps on the chrono. when fps began to drop, I backed off the reg 1 quarter turn(this was 2 quarter turns away from all the way screwed in) and fired a string of shots to verify stable fps numbers. The reg pressure ended up at ~165bar. This is my (close to max) "power" tune. This is the easiest(and most consistently reliable) method I have found to find (close to)max power. I get a little over 3 magazines(58 shots) on higher powers shooting slugs out of the 380mm barrel(highest air requirements) and over 100 shots on lower powers with pellets. 

I first found this method while tuning my MK1 Crown a couple years ago. I have tired many other "lower powered"(lower reg pressure and the corresponding less HS pretension) and got higher shot counts, but lacked power to shoot heavier pellets or slugs accurately. I prefer this "power" tune as it allows me to shoot a wider variety of ammo with a "tight" shot string(keeps deviation and ES low)
 
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I've used both pellets and slugs for testing, but max always ends up being max with either one, so I use whatever I have that I don't want/shoot much of. I do always use the 380mm barrel(most power requirement) tho. 

I guess every gun/barrel is different. I got my Crown Continuum MK1 in May of 2018 from UA with reg set at 125bar shooting jsb 18g @ 890fps out of the 380mm. I have never been able to find a tune to get it to shoot the jsb 18g over 915 fps from the 380mm barrel. Close to max power tune for it is approx 130 bar.
 
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Hmm yep, the mk1 continuum sounds identical to my gun. (my barrel inlet is ported, observed 50fps gain on factory tune.) I know the mkii has a larger valve and plenum, but I can't wrap my head around how it would change the power curve/output in the way it has.... Maybe the larger valve is harder to open... But it seems that would push peak power to a lower pressure not higher.... 🤔
 
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Idk. Makes sense, tho. I certainly don't pretend to know what sorcery goes on in the guts of and FX receiver. I am lucky enough not to have had any problems with my Crowns, or been inclined to try and mod it. I know others have gotten increased performance from modding hammers, springs, transfer ports, barrels, etc... I'm content to just work with "stock" guns and try to make them as good as possible.
 
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