Length of rifling?

[Troy Bakel]

My question of my understanding the relationship has yet to be answered. That’s cool, I really don’t need a confirmation of the relationship as I’m not messing with Olympic style shooting.

Have fun with your project,
Dave

My HM1000X-MPA Matrix was tuned by Mr. Martin to launch JTS 22 cal, 22.07 grain round nose diabolos at a muzzle velocity of 990 fps. Yet the same barrel length, same plenum pressure, same hammer force and dwell time will launch a 14.3 grain Crosman Premier Hollow Point at greater than the speed of sound.

I know if I chopped enough barrel off ..... both velocities would drop but at full barrel length did I need full length rifling to attain those velocities? No. If the diabolos are the correct diameter for the bore (land to land) diameter the rifling has no effect on forward velocity. Rifling only effects spin rate and you do not need rifling the full length of a barrel to establish the desired spin rate.

 

[subscriber]

The FX smooth twist or rifled choke idea was great, as a cost saving. If you want to know what spin rate your pellet achieves using that rifling system, measure it by means of high speed video: An effective twist of 1:36 to 1:48 may be fine for diabolo pellets, but the fact that those rifled chokes' helix angle were correct for 1:16 means twist in .22 caliber barrels, means the pellet are skidding through the choke. Which is why they tend to lead up.

In an airgun, the friction peaks as the projectile swages into the rifling initially. After that, the friction is much lower, providing the rifling is a constant pitch, and the land and groove width and height are constant. Sure, making a smooth bore uniform is cheaper, but the idea that a partially rifled barrel is superior has little merit. Sure, FX pushed the smooth twist concept as superior, until they figured out a cheap way to impress rifling into the full length of their blank barrel tubes. Now, that is superior.

As for Baikal's hammer forged barrels; I am very happy with my 46M pistol, despite the barrel being rifled full length