Birdhunter50

There are countless reasons for getting a screwed up weld.
The most common reason is that the guy doing the weld didn't have any business working on your gear.
It's that simple.

Tig welding is like anything else.
There may be more than one right way to do it right, but there's an infinite number of ways to do it wrong.
Yes it's true that there's more than one way to plug the machine in, set it up, choose the material of and properly prepare an electrode, shielding gas, filler rod alloy and diameter, turn the dials or press the buttons...

It would take a fool to attempt to write a forum response or essay... on how to tell a guy how to make a tig welder to 'not get pinholes in a weld on gun parts during the conversion of a shotgun to a double rifle...'

Don't try to look so far into the why.
Look for a different guy for the job.
I've been welding and machining metal for over 30 years. Via every process available, I've put down more miles of weld than I'll ever care to account for.
Hired and fired plenty of good welders, turned a lot of lawyers, carpenters, dentists, librarians, lapdancing strippers (no shit!)... into damn good welders over the years.

I totally agree with you on the 'No Tig On The Monoblock' mandate. That's a whole different discussion though, and I don't think it's appropriate to engage in coaching anyone who doesn't already know why on a website like this over such a topic.

As far as pinholes in welds -- just find someone who's qualified for the work, don't look for the 'get me up to speed on this one' forum response.
Birdhunter50, I've noted to you that you appear to have the right kind aptitude to quickly become a qualified welder.
I meant that. It isn't going to happen over the world wide web though -- and there ain't no way we're going to be able to coach the guy who laid pigeon shit welds on your project to do it right.
Ever.

As I've told hundreds of people in the past, you're going to find some of the best tig welders in high-buck bicycle framebuilding shops -- not the place where you get a basket and a rack for the schwinn, but the dark and cold workshop where the thousand buck and up bicycle frames are built.
Those guys are working with playing card thick, crazy-ass alloy steel tubing every day.
The welds they do are some of the highest life-risk liability welds in the business.

We can kick the 'pinhole problem' around till our toes are worn through to the bone.
It's a fruitless conversation.

Also, building a double rifle on a shotgun action isn't a job for an amateur in the metalworking trades. I consider most gunsmiths AT BEST poor applicants for entry level positions in the high-end metalworking trades.
Furthermore, of the hundreds of welding shops I've seen, I can think of very few who I'd trust with any kind of gun parts or barrel welding project (you'd be getting closer looking at generations-old tool and die shops).
This kind of work takes an ALREADY UNDERSTANDING of the distinction between and the function of soft solders, silver solder, brazing alloys, fluxes, welding processes, and the equipment and considerations around them -- as well as solid understanding of the materials, from simple weld prep, material selection, clearances necessary for weld/braze/solder joints, down to an at least basic understanding at the molecular level.
Y'ever wonder why those brazed carbide tool bits have a wafer of coper foil between the steel shank and the carbide in the braze joint..?

You don't just go read a book, take a welding class, and then become qualified to take this kind of work on yourself - then expect to end up guaranteed any kind of successful result.
You need to be able to go into this kind of project with the tools and knowledge to know FOR DOUBLE DAMN SURE whether or not what you just did ANYWHERE IN THE PROCESS is good or is not good. From there you need to know how to treat the good stuff and what to do about the stuff that wasn't good.
Birdhunter50, I'm just guessing - off the cuff here, that you knew your way around the shop for more than a few weeks before you took your first double rifle conversion project on. I'm also pretty clear that you're OK with knowing that you're not 'the guy' *today* to do a tig weld on a rifle action. I'm just standing up to say that it doesn't appear to me that you've found the 'right guy' in your neighborhood yet. There are full-kitty professional outfits that are straight-out gunsmithing specific. Doug Turnbull's operation comes to mind pretty quickly, there are numerous others. Consider these places a good place to send that 'quick little weld' that (the collective you) you aren't prepared to handle.

I have no apologies about the 'tough love' tone in this message.
This is serious business and shouldn't be taken lightly.
I don't want anyone here to think I'm accusing them of being a dumbass, a bad (or good for that matter) gunsmith.
I don't mean to offend anyone here with what I've said.
I anyone here does find themselves offended with what I've said, let me know right away and be specific on exactly which feelings got hurt and where.
I'll do my best to respond appropriately.

--Tinker