Tuning FX Streamline/ Smooth Twist / slugs?

Excuse my ignorance but does the Streamline have the ORIGINAL Smooth Twist barrel? If so, I don't think you'll have much luck with slugs. Believe me, I've tried with mine (Royale 500 & Boss). OST barrels were designed around JSB pellets & do that job SUPERBLY but the physics are all wrong for slugs.

The streamline has the old school smooth twist with the last bit of the barrel rifled. Still a very good pellet barrel. 
 
There was someone on here saying that his .177 was accurate with certain NSA. As for the .22 and .25 I didn't have any luck but maybe the .177 is different.

That was probably me.

I have been on a quest to find "one" ammo for all of my guns. Currently I am using NSA 17.5gr for my MCT and M3. Both shoot lights out. I am also using the 12.5gr for my Daystate MK4 and FX Royale 400. And yes, the Royale does have the Smooth Twist barrel. I have heard the .22 and .25 versions of the Royale doesn't like slugs. I have yet to try them on my 500. But I can assure you, at least with my gun, the 400 in .177 does shoot slugs well out to 100 yards. I only say 100 yards as that's the longest distance I have to shoot them on my property.

Keith.
 
My smooth twist barrel shoots NSA 17.5 gr .217 -HS-HP-DB out of my HW100 at 910fps very well.
But I must say , the gun is more consistent and is a lazer with the 18.1 JSB pellets.
The low was when i dropped of the reg.
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