What are the ways to use a scope on an untapped barrel?  I want to temporarily mount a scope on some on some rifles of mine.  Thanks for your input.

Win225

I've seen it posted here about using epoxy or JB Weld to mount bases. Then when you want them off just apply some direct heat to make the epoxy let loose. Never tried it myself.

I used some Acraglas gel to glue some blocks on to a Stevens 44 barrel with a nice patina.  It held OK for 50 or so shots but when I removed them all I had to do was give them a gentle tap.  Unfortunately the finish came off with them. 

Jack

Kind of philosophically speaking: I think it boils down to whether one is dedicated to the ideal of "pure as-manufactured condition" or accepts minor practical changes effected during the time immediately after manufacture when the gun was simply a tool, a means to an end. Ie: scope mounting holes to accommodate an 1890's-1920's period Mogg/Malcolm/Stevens/Winchester scope on a Ballard target rifle. To that end (given that such alteration doesn't effect the value in one's eyes), if one were to drill said holes today in an otherwise pristine Ballard who's to say it wasn't done 120 years ago - it's forensically impossible to dispute it.

We have differing attitudes about this. Who's to say what's right and what's wrong. Personally, I thank heaven when a righteous specimen comes along that has been previously fitted with scope access, it relieves me of the quandary of doing it myself and does nothing to detract from the historical/monetary value (and often adds value in my eyes).

Faced with the conundrum of drilling/tapping a 100+ year old Stevens 44 so I could have the pleasure of actually shooting it at its full potential, I would - and who's to say it wasn't done 100 years ago in Niedner's shop at Ned Robert's behest paid for by Townsend Whelen? (A ludicrous example for sure, but with provenance would sky rocket said 44's value not drag it down.)

Agreed, Bill. But, where is the line drawn and who draws it? And if one steps over the line, so to speak, who among us is forensically capable of proclaiming it was done in 2025, 1950, or 1901? Honesty/veracity, or lack thereof or ignorance for that matter, comes into play also. 

(And for the record the only rifles I consider fair game are parts guns or otherwise egregiously tampered with specimens. At that point all bets are off and I'll do as I see fit. My previous comment about d/t'ing a Stevens 44 was hypothetical in nature.)

I own a number of old original or custom singleshot rifles that have been d&t for scope bases, and it doesn't bother me when I find one I like. But I personally would never be the guy who d&t an old rifle myself. 
Occasionally I've purchased an old rifle that looked like someone's machine shop project with all sorts of holes in the tops of their barrels for different bases, or spacings, and I usually find two pairs of holes that make it the standard spacing and bases, and plug the rest before restoring the barrel finish. I figure I could remove and fill all of them, but I do appreciate shooting my old singleshots with scopes or iron sights, so I always leave those that work alone.
I have some old Remington Rolling Block rifles that never got holes for tang sights, and I'm even more tempted to d&t the top tangs for a tang sight. But there also I've restrained myself and not added tang sight holes.