Bad groups with slugs

[aldea6]

Hi , today I decided to make some improvements to shoot slugs with my FX Dreamline Classic . I put a slug liner A 500mm , and removed the aft spacer from the liner ( super light system), keeping only the front spacer . Between this one and the brass compression nut I put a carbon fiber sleeve, with epoxy , to increases stiffness . Took the gun to shoot some pellets first , JSB 18 gr ; good groupings at 50 yards ,850 Ft/s .

Then I increased speed to 900 Ft/s and switched to slugs....bad surprise. I expected some POI shifting , of course , but not such a catastrophic result : slugs spread in all directions , 10" right or left , up , down ...felt like I was shooting a shotgun.I began with FX Hybrid , with very bad result , no grouping at all ! Same with NSA 21gr , Javelin 23 gr , Zan ...impossible to get a decent group . Where have I been mistaking ? Speed , barrel harmonics ,....?

I was so disapointed that I took my Kalibrgun Tactical 60 to shoot very good groups with.....FX Hybrid !!!! at 900Ft/s

 

[Scotty1]

Is there any chance they are clipping your moderator?

 

[steve-l]

Sounds like not enough spin. I suggest you check the riffling yourself not just the label on your barrel. You need the "Heavy" barrel about 1 rev in 18 ".

 

[qball]

Sounds like your tune created way too much muzzle blast and destabilized the slugs. Try to find 850-900FPS speed range with regulator at 150 bars, you will need the medium weigth hammer which is unlikely for a 22 to have coming straight from the factory. Call FX and order the heavier hammer and tune your tune with high reg pressure or it's very hard if not near impossible to get a good slug tune. 

 

[aldea6]

Thank you guys ; about the moderator I don't have any issue with pellets , could it be different with slugs? Reg pressure is at 130 bars , I didn't increase the HST untill now and I used the FX slug liner with which , I remember , I didn't have good results with slugs in my Crown . Changing the liner is an option ; odly enough this liner groups very well with pellets ...

I keep going testing 

 

[biohazardman]

It's likely all in the tune. Try going up and down in velocity near 20fps each way and you will likely find an accuracy node in there somewhere.

 

[steve-l]

When I received my Crown in .25 with the standard barrel, it liked the 25 gr JSB pellet, but did not do so well with the 34gr JSB and slugs were all over the place. I changed to the 1 in 18 heavy barrel for the JSB Knockout slugs and everything started working better. My Crown really likes the faster twist. I have never changed the reg pressure. It is still at the 135 bar it came with from FX. I see around 890 fps with both the 34 grain pellet and the 34 gr slug.I expected the 25 gr to start looping being a bit over stabilized with the higher twist barrel, but I have not seen that surprisingly..

 

[aldea6]

Yes , there is no reason this gun couldn't shoot slugs better than this . I'm going to tune it in a more methodic way , changing each factor one at a time . Adding a plenum chamber to get more power , maybe. Lot of work to come