I just started making some Lee 160gr RF boolits last week. I have made some felix lube and have some Hornady gas checks. I have seated some by hand but though I better ask is it absolutely necessary to seat with mechanical means. I am trying to order a lee sizer in .309 but am still waiting as supply is limited.

What I am really asking is will these gas checks come off or should I load a few up and try shooting them anyway. I have tried removing them by hand and it's not real easy. Must them be crimped on. ?

I won't say I'm an expert on seating gas checks by hand or by any other means doc but it mighten hurt to load some up and just see what happens.The way I understand is that they do what they've got to do in the barrel & after that their just there for the ride as it were

Doc
You may wish to measure the flared portion of the gascheck, the mouth.
If you were using the old Lyman gascheck there would be no problem in just pushing the gascheck onto the bullet base.
For my 30-06 Winchester 95 I found that using a sizing diameter of .311 worked like magic.
Jim