In my experience
If you want a general use quantity epoxy,the West systems marine epoxy can be had in a qt can with a small can of catylist.There are fast and slow catylists,and a fairly inexpensive ratio pump is available to put in the cans.
They have a series of additives,from lightweight microbaloon filler to flock,wood flour,etc.Some thin this down for stock filler,but I lack experience with that.They build airplanes and silboats,etc with this stuff.
If you don't have much experience and want a good product that is forgiving and easy to work with(relatively) I like accraglas Gel.It does not run or drip.
While it is true an accraglas kit is expensive,it gives you what you need,the research and guesswork has been done,and Brownell's IS an outfit we want to give our business to.The stuff works!
Regular accra glass is still flowing when you use it.That is good,for fill and penetration.If you are just learning,it can make you sad to see the resin running out the bottom and gaps forming up top.
Steelbed I used in a Hi-tec specialties stock.It adds a little weight,but it was a 30-338.I'm happy.
Polyester(general auto fiberglas) is OK when it is the original matrix in a boat or something,but it does not stick as well as epoxy.Epoxy is what you want.
NEVER mix epoxy and polyester components.Very bad reactions occur.
That ACE hardware epoxy putty that comes in a stick is pretty darn handy stuff!
Devcon titanium is interesting.I used some once in another application.It seems to have a very high solids content,and "stacks" a bit.
I have used quite a bit of flexane to build fixtures ,etc.It is about like a deadblow hammer.It is available in 94 duro.You likely will have some bubbles with it.It does not evacuate in a vacuum chamber well.Haven't used it in a firearm.It really sticks!!
h,and my compliments to the pix,flawless,Beautiful!!I love the box of media!!Walnut hulls?