First load GLB post I got no replies, hopefully somone will lend their expertise on this question:

I am about to embark on loading grenade launching blanks for my Yugo M59/66, 7.62x39mm. The crimp die set is on it's way to me and I know it puts a good rose petal crimp on the case mouth to close it but it does leave a tiny hole in th ecenter of the crimp which must be sealed with something.

Anyone know what this "something" may be? I have used finger nail polish to seal some but it takes multiple applications as the powder outgasses and this blows bubbles in the polish! Need something a little thicker than this but still flammable so it will be consumed in the blast when the cartridge goes off. Any ideas or suggestions...? M59/66 Rifle Grenade launch page

Yes, hide behind a concrete wall and pull the trigger with a string.

I cannot imagine why you're doing this, but in the spirit of exploration and comraderie, I suggest you use a small flat of aluminum foil to seal the case mouth prior to crimping. If there is not enough powder to keep it in place try stuffing a small bit of toilet tissue in first. Best I can come up with, but I disavow any responsibility for the results as mine is just a wild ass guess, and your results may not be what you hope for.

Thanks for the suggestions, the toliet paper one is a good one but it might decompose over time.

Really, it's a hoot to launch something that large and heavy that far with your rifle. Since the butt is not planted on the ground the rifle is not receiving an undue amount of stress on it and from experience I know it's safe to do this. As long as that RG can be slipped on and pulled off easily there is no problem blowing it off the end of the barrel. It comes off of there around 200-500 fps depending on caliber and weight of RG. Once you launch a couple of these it's hard to wipe that silly grin off your face! Here's some more RG footage using the FAL:

FAL RG launches

I've been thinking about a similar project, using a wax plug. I was thinking about wax melted onto a small dish, then cooled. I don't know if the wax would stick to the dish upside down. If it worked, you could then seal the top of the wax plug with nail polish for strength.

These are only ideas, I haven't tried any method, yet.

Guys what about that powder outgassing?

All of the grenade launching rounds that I have opened and then sealed back with finger nail polish had bubbles blown from within . I have opened FAL grenade launching rounds, US Military GLB's and new production Hi-Vel rounds. All showed the same thing, a bubble would rise from the hole I was attempting to seal and eventually the hole got smaller and smaller and the polish dried quicker than a bubble could form. So the powder does have some sort of gas coming from it, very low pressure, as the bubbles formed so slowly.

I like the Wax idea and then an over seal of red finger nail polish. Come to think of it the seals on some of the GLB's I opened slightly to get the powder out and measure it had a look and feel of a wax type sealant. Good call on that one! Worth a look into.