Teaching a Old FX Crown a New Trick! (update 8/9/19)

 

Hello AirgunNation Peoples,

Okay.. Okay... JoeKool has been bitten by the “slug bug”. I was one of the early adopters of the FX Crown back in 2017 and have been extremely pleased with it’s shooting (.25) JSB Kings 25.39gr @ 950fps and JSB King Heavy MKII’s 33.95gr @ 850fps for the last 2 years. Accuracy is flat out great and beyond satisfactory out to 100 yards at this tune, with these pellets, and with the 600mm “A” .25 caliber FX pellet liner. But... Slug this and slug that has got to me. So, what would I need to transform this shiny walnut beauty into a certified .250 slug slinging beast?

Four things:

1. A 580cc FX Carbon Fiber bottle upgrade over the stock 480cc CF bottle (more air)

2. The 600mm (.25) slug “A” liner

3. Nielsen Special Ammo .250 - 33.50 grain hollow-point slugs ( boxes of them!)

4. A power increase tune (more speed)



So, this stuff: (Crown .25 580cc CF bottle, slug liner, & NSA .250 slugs 33.50 grain)





To get things rolling, a good experiment should begin with a controlled medium. For comparing after things get altered. So the controlled medium would be a rested set of 5 shot groups shot at 50 and 100 yards. These groups would be shot using the Crown’s go-to ammo the JSB KING @ (950 fps) & KING HEAVY MKII @ (850 fps). The two year old tune that has worked faultlessly for my Crown. Also this test will be shot through the OEM .25 600mm “A” pellet liner. Regulator pressure 135 bar and hammer spring on MAX but specifically tuned to reach the below speeds for these JSB .25 caliber pellets.

Chronograph results FX Crown pellet liner, pellet tune, and JSB King and King Heavy MKII 







Here’s the “Control Group” Target:



In the field ( left 25.39 & right 33.95 MKII )bottom 100yds, top 50yds:

Same target ( left 25.39’s & right 33.95’s)bottom 100yds, top 50yds:

This is my best for a breezy day! So, having this vital real world info... Can the FX Slug Liner / Power Increase / Nielsen Slugs do better?

Keep reading.

Next was about 3 hours worth of a combination of installing the new 600mm Slug “A” liner, tuning the Crown’s regulator to 155 bar, maxing out the hammer spring, and chronograph testing.

Here are the resulting speeds and energies with each projectile in the tests. Through the 600mm .25 Slug liner after being satisfied with the tune.

JSB .25 King 25.39 grain



JSB King Heavy MKII 33.95 grain



Nielsen Specialty Ammo .250 Hollow Point Slugs 33.5 grain 



Now on to what this post is all about. The Slug Liner and NSA .250 caliber 33.5 grain slug groups. Also, curious to know how my normal ammo for the Crown .25 will fire from this 600mm slug “A” liner, the JSB .25 King and King Heavy MKII!

FX Crown .25 Slug liner 5 shot groups @ 50 yards (left to right, JSB 25.39[1st], JSB 33.95 MKII[2nd], & NSA 33.50 HP- Slugs[3rd])



Same target (50 yards)



How does a pellet out perform a slug in a slug barrel?

100 yard target Slug liner 5 shot groups (left to right, JSB 25.39[1st], JSB 33.95 MKII[2nd], & NSA 33.50 HP- Slugs[3rd]):

I’m no one special when it comes to long range shots with airguns, but was happy to see that the slugs where at least on par with my trusted MKII’s!

I know and understand the ballistic advantages of slugs vs pellets, but unless you guys can help me out with some “secret formula”? I may go back to the pellet liner and my tune that has worked for me.

Ballistics YES mind boggling accuracy NOT YET!

Huge ballistic advantages though, take a look at my BC calculations and some ChairGun graphs after plugging in my testing info?



At this tune and slug liner setup:

JSB KING .25 25.39 grain BC = 0.036









JSB KING HEAVY .25 33.95 grain BC = 0.051









NSA .250 Hp-Slugs 33.50 grain BC = 0.075







Does anyone have any tips for improving or shrinking my FX Crown .25 slug groups?