Moderator Bore Clearance Question

[Steyr]

I have a moderator in 22cal which I would like to use for 25cal gun. A quarter bore inch rod fits OK through the moderator but is very snug with very little clearance. Do you guys think this would be OK or I would get lots of clipping, damage the moderator, etc,

 

[Stubbers]

I'd advise against it. You need nearly the same ratio from pellet to bore in .25 as is currently present in your .22 moderator. Which would be around a .285" bore minimum for .25.

Not to say it's not possible, just rather...not advisable. The above ratio would leave around .0175" radial clearance.

-Matt

 

[Gerry52]

Don't forget, it's NOT just whether the pellet can fit through the moderator bore but also the effect of air turbulence around the pellet exiting a too tight clearance. Other factors at play besides "exit hole clearance". Just get the correct moderator!

 

[steve-l]

It can work, but it will be close. If your alignment is not correct , you will get clipping. I made an alignment rod from a piece of precision ground .250" rod ground down to the exact diameter of the barrel choke. I use that to check moderator alignment where the gap around the moderator cap is uniform around the rod when placed into the barrel bore. I use a clearance of .010 radially when making my moderators.