Moderator hole size

Well a 1/4 inch is .25 caliber.

Have a 22 cal would like to make it work on a 25 cal. ( would like it to be slightly bigger so there is no pellet clipping ) so what size drill bit do I need & have you done this before ? I'm thinking I need to ream this. Thanks in advance headed out shooting soon but will get back as soon as I can Darell

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The ID of my .25 cal. mod is .315" which is about 8mm.

The ID of the .22 mods that I have seen are usually around .265"

I would definitely use a reamer(s) if you have access. Not drills because they won't cut a round hole.

Perfect way to do it would be to gradually step the ID up in size because reamers are not made to hog with.

Start with a .281" reamer, then .296 then finish with either a 5/16 or 8mm reamer.

Use oil on the reamer flutes and run them at 200-300 rpm (not too fast)

Good luck. Hope this helps
Matt

Here's a picture from when I modded my .25 Tatsu from 1/2 UNF to M14x1.25 to fit my Vulcan.

Matt's idea is probably the way to go but I didn't have all that stuff so I used a drill to open up a Donny FL Sumo and it looked absolutely perfect when I was done. After I opened it up, I used a sharpie to cover up the bare aluminum and was done. Took about five minutes to do the front and the internal ports and you can't tell it was altered at all. Quick easy and cheap if you don't have all the tools. It's really no big deal, just take your time. If you have the tools, do it Matt's way, I didn't and it was no big deal.

Stoti

Hopefully your moderator is a DonnyFL type so you can take it apart to also ream out the internal baffles. Either that or have a really long bit.



if you do have a Donny FL, try swapping his wrap inside for white foam wrap that you can get at Home Depot in the plumbing ABS pipe section. It comes about 3/16” thick, 4” wide, and is available in small roles. Really helped to quiet my Shogun even more so. I used electrical tape to compress it tightly at midpoint, and ends. I only lapped this material about 1/2” due to its thickness.

If the moderator is made correctly and any adapter is correctly mounted to barrel concentrically (you need to check carefully), pellet clipping is a non-issue. Bore size in relation to moderator effectiveness is not a sensitive issue either contrary to popular belief. I make moderators for myself and have made many over many years. I generally use .020" or.5mm for pellet to hole wall clearance. This clearance can be more with no change in noise level. In point of fact many commercially sold moderators use large bore sizes so that the moderator works on more than one caliber.