Tarawa-

I'm skeptical of the possibilities or getting good repeatable data from this laser boreguide experiment.
I'm equally enthusiastic for you in your undertaking and wish you the best success in getting your cool set of doubles regulated and running properly.

You might have noted this elsewhere, so forgive me if you've already answered this elsewhere -- but with three similarly chambered rifles, are you going to set each of them up with significantly different loads, such as high velocity varmint, heavy hardcast flat point penetrator, and traditional RNSN JHP soft skin game loads?

Over at The Drilling Hotline (and elsewhere I'm sure, this is standard, Remington factory loaded ammunition in Remington boxes...) they offer the Remington 55gr 22 accelerator rounds (4200fps!!) in 30-06 cases. Cool stuff for sure, and they're only about $35 USD a box there - typically you can find this ammunition for about $30-$38 a box when it's in stock.

Here's an early promo image from Remington, it shows 30-30 brass (which they also offer).

I'd try this with the stack guns first, and for all it's worth, you could get one of those stack guns shooting whatever 30 caliber bullet you want on the top barrel, and the accelerator on the bottom barrel (or whatever...)

I think there's some neat possibilities for you with this 'magazine' of low-cost, adjustable 30 caliber doubles.

Give it some thought.
Let us know if you go this route.
I'm interested to see if it could work out.
We all know what the possibilities could be!

-Tinker