What makes certain barrels able to shoot pellets and slugs well?

[kwaping]

Through my research while trying to decide on a new gun, I noticed that some barrels are able to shoot both pellets and slugs well, while others are only for one or the other. What are the qualities of a barrel that lets it be versatile with ammo type and remain precise?

 

[Gerry52]

From my understanding a barrel that can do BOTH needs to be unchoked, maintaining the same diameter throughout the full length of the barrel. That's the extent of my knowledge on that & I won't swear it's 100% correct.

 

[kwaping]

From my understanding a barrel that can do BOTH needs to be unchoked, maintaining the same diameter throughout the full length of the barrel. That's the extent of my knowledge on that & I won't swear it's 100% correct.

I've seen that term before but have never looked up what it meant. Thanks for the hint, I'm going to do some research on that as well.

 

[JimD]

I would love to know why some barrels shoot a particular pellet well while others with equivalent design prefer a different pellet. I have two barrels for my P35-25. One shoots JSB heavies, 34 grain, best. The other prefers H&N Baracuda pellets. Same design, same manufacturer (SPA). If we cannot explain this sort of thing it seems unlikely we can explain preference for pellets and slugs versus just pellets.
O
But we do know that slugs want a faster twist rate while pellets may shoot most accurately with a slower twist over 1 in 20. But most airguns seem to come with a twist rate around 1 in 18 which seems to be fast enough for slugs. My Caiman X has this sort of twist and will shoot both pellets and slugs accurately. But my P35s have about the same twist rate and I've only found a slug the 177 will shoot reasonably. Nothing I've tried in the 22 and 25 will group.

My guess is many guns are more picky about slugs making it harder to find a slug/gun match. If the twist is fast enough it may be a question of searching hard enough to find a slug your gun likes. But my Caiman doesn't seem to be picky. All H&Ns 21 to 30 grains will group about 1/2 inch at 30 yards. Not sure about others.

My Caiman X and P35s are choked.

 

[Firewalker]

I would love to know why some barrels shoot a particular pellet well while others with equivalent design prefer a different pellet. I have two barrels for my P35-25. One shoots JSB heavies, 34 grain, best. The other prefers H&N Baracuda pellets. Same design, same manufacturer (SPA). If we cannot explain this sort of thing it seems unlikely we can explain preference for pellets and slugs versus just pellets.
O
But we do know that slugs want a faster twist rate while pellets may shoot most accurately with a slower twist over 1 in 20. But most airguns seem to come with a twist rate around 1 in 18 which seems to be fast enough for slugs. My Caiman X has this sort of twist and will shoot both pellets and slugs accurately. But my P35s have about the same twist rate and I've only found a slug the 177 will shoot reasonably. Nothing I've tried in the 22 and 25 will group.

My guess is many guns are more picky about slugs making it harder to find a slug/gun match. If the twist is fast enough it may be a question of searching hard enough to find a slug your gun likes. But my Caiman doesn't seem to be picky. All H&Ns 21 to 30 grains will group about 1/2 inch at 30 yards. Not sure about others.

My Caiman X and P35s are choked.

Man, if you figure it out you'd be rich! I think the intended markers for an accurate barrel are known but putting it in practice is a different story.

Just look at the recent new barrel companies that took years to figure out what worked for them with the equipment they had.

I don't make barrels so this is just speculation but I think there is more to it than we think.

 

[Motorhead]

My thought and loose findings are this ...

A bore that is concentric end to end having no oddities is tight to loose spots than appear if present to YAW destabilize the projectile.
* In other words the Lets say Slug must spin along it's absolute balanced center line like a TOP does on a flat table being motionless outside of the spin present.
If there is ANY radial wobble the axial center line is also moving.
Only when said projectile exits barrel with perfect spin will it fly true and straight.

Rifling only needs to be slightly off ( As in groove depth differences radially ) for the projectile to leave muzzle ever so slightly in a orbital spin that may be straight tip to tail axially but off Radially.
* A wobbly football is generally radially running true but AXIALLY in a wobble as the tip and tail are out of alignment. This counter to statement one line up ....

Just thoughts ....

 

[bigHUN]

The bottom line is, picking up a good performing barrel is a pure luck. Some people keep buying and testing and buying again, and some gave up with spending money and try to make it work DIY.

I just did some lapping on my six FX liners, what fire lapping and what cast lapping, or both.
I learned that the rifling - land has its own ID and groove has its own ID, and not necesery two liners with same TR (different length) are the same.
Each land or groove on he's own can have tight and loose spots.
With lapping and polishing I tried to get a most consistent friction along the length. The choke is the next unknown and hard to predict.

Next time at my gunrange bench, I am expecting I will have very different indexing/tuning/POI and most likely the old tune is gone.
I know the ballpark for pellets but the slugs are a lot of work, I would need to buy couple cases to make sure enough for re-tuning again.

 

[Airgunmann]

Twist rates play a good size part depending on the length / weight of slugs

 

[timmah]

I'm thinking that slugs are more sensitive to barrel imperfections and twist rates since they're solely dependent on spin for stabilization in flight. Pellets have some stabilization built in by virtue of their diabolo design, so may be more tolerant of barrel and twist variances. Just speculating out loud here.