It's a wildcat that I designed about two years ago. It's a 300 wsm shortened. It's about 45 thousands bigger then the 7 saum. I built one in a rifle. It shoots the berger 168 at 3200 and the 180 at 3050. this is very mild load. The gun will shoot in the one's at two hundred and 600 hundred it will shoot just under a inch.
Depending on a variety of things I would go no shorter than 16" out to 18" for my uses. The Vais brake is a good one for sure, but if you will be doing much prone shooting you will learn to dislike it as it will cover you and your optics with whatever is on the ground-Been there and done that
For field rigs I have gone to the solid bottomed partition brakes. APS Kirby's / Defensive Edge Shawn's / Radial Baffle Quick Discharge Darrell Holland's, etc..
I have evolved over the years when it comes to barrel length. It all depends on what I want to shoot and how far I want to be able to reach.
For example, I love my xp in 338 WSM in a 15 inch tube. Easy to carry in a holster and plenty of power out to 300 yards on large game.
For 600 - 1000 yards I had my 7 Dakota rebarreled to 25 inches in order to push 180 Bergers to 2950 fps or so. I could have went shorter, and gave up velocity and wind drift and "pushed" it hard to get the most velocity. I know 25 is a bit extreme, but I would not go below 20 inches for anything I intend to use out to 1K yards.
My 17 inch 7 SAUM will send 140's at 3K fps and does well out to 600 yards. With 168 Bergers it can do right at 2800 fps which is very good and will really reach out.....at least to 800 yrds with pretty good ballistics.
My .338 Lapua is heavy at 16 pounds and sports a 20 inch tube. 250's at 2900 or bit more is the norm for that one.
I'm having a .338 Norma on an xp built as we speak with a 23 inch barrel in a #5 contour for a lighter weight rig for when I have to walk a lot during the hunt.
If you have Quickload you can play around with barrel length and projected velocities to give you some idea. For your project I wouldn't go shorter than 18 inches plus brake.
A good baffle brake like a Holland, Defensive Edge would work great. Also a radial brake from Holland or American Precision would even work better especially if you are going to use a rifle scope and I would guess you will for long range work. The Muscle brake or Pain Killer from Kirby also would work very well too.
It really depends on how much you want to adjust for drop and wind, and how protable you want it to be. Good luck in your decision.