I am sure it is here somewhere but I don't know how to find it. So what size drill do you use to drill out freeze plugs or baffles for a .22LR can and 9mm can?

Thanks.

For freeze plugs where concentricity might be an issue the smallest I'd go for a .22 is 9/32 which is 0.281".  Keep in mind drills usually drill over nominal. So you could start as small as 17/64 or 0.265" but normally that's pretty tight for something not bored concentric on a lathe.  If you use a gauge rod and everything clears great. Otherwise you can upsize your distal baffles or the entire stack to 19/64 or 0.297.

For 9mm the smallest to start at 50 thou over bullet diameter is 13/32 or 0.406". You're probably better off at 27/64 or 0.422.  Or drill 0.406" and ream larger.

Since thin freeze plugs can grab a drill leaving a distorted hole sometimes drilling undersized and reaming or filing to finished diameter is the best process. A cheap harbor freight conical reamer can finish freeze plug holes.

It's also possible to center drill freeze plugs with a centered spotting hole undersized to the bore and then pressing a a cone while expanding the bore at the same time. Not necessary if the plugs are already pressed into m-baffles.  If your cones are already pressed you'll have better luck staying centered by step drilling starting with a 1/8" drill or a short stiff center drill.

Good luck.

I use 60 thousandths over bullet diameter, so caliber + 0.06

There is probably more opinions out there on bore size than carter has pills so I will go ahead and add some numbers. The system I use and recommend  is called a progressive bore. When you think about how the blast bubble moves through the can the best performance will be obtained when all the parts share in the workload. Baffle design is the most important which also includes clipping. But just as important and can have a major impact on performance is baffle spacing. You need to consider all the factors in can design.

Back to bore size, this has been verified by many that have built cans following these guidelines developed after thousands of rounds of testing. This is directly from the tutorial over at form1suppressor.boards.net.

From the tutorial
I'll start with the bore size, I have consistently recommended the bore size . 080 larger than the bullet diameter and the endcap bore .100 over the bullet diameter for rifle cans The last two 30 cal cans I have built I bored .100 over for the first two ss coned or ss radial baffles .410 . The next 3 ti cones are bored .400. I have switched to ti RSC for the last 2 baffles bored to .390. the endcap is bored to .410. stack  All baffles are using the DHC. I currently use as of 5/2017 all RSC in both rifle and pistol cans which have been proven to have excellent performance and proven by many and on sound meter testing.

The results have been outstanding and tested on 308, 300BO and 556 all through the same can. 134 db on 308, 126 db on 300BO, 129 db on 556.
form1suppressor.boards.net/thread/2215/meter-testing-results

The larger bore on the first two baffles reduces the back pressure and allows the gas to flow through at at higher psi in effect increasing the efficiency of the middle baffles and the last two baffles improving suppression. The last two vsr baffles trap the gas and allow a larger volume of gas to compress due to the flat sectons on the OD of the RSC vs a cone extending flush with the outer wall.. As the psi starts to reduce the higher volume in the last two baffles are directed into the laminar flow by the dhc which improves suppression. the last two baffles also with a smaller bore than the endcap act as a throttle allowing the gas to expand and exit at a slower rate through the endcap. Using all RSC improves this performance and results.

I also built a 9mm can using .420 for the first two baffles . .415 for the next 3 baffles and .410 for the last two ti RSC baffles and .425 for the endcap all with the DHC and the same outstanding results as on the rifles cans.

If they are available to you, try using an end mill instead of a drill.

If the cone isn't exactly on center of where you want the hole, an end mill won't care.
If the cone is pressed you don't need to worry about the end mill being center cutting.
Only real downside is a little less size selection than drills, but you should be able to find a fraction close to what you need.

need a boring bar and very precise measurements, so that the hole is both round and centered, if you want to maintain the rifle's accuracy. Egg shaped holes mean that the blast effect is greater on one side of the bullet than on other sides, which is not good when you want maximum stability in that bullet.