Hello,
New member here and I am gearing up to start a takedown Mauser build that will be a two barrel set. I have seen some good threads on takedown Mausers on the Nitro Express Boards.

I originally just wanted to design and build a takedown, but then I figured to add to the purpose of a takedown and have a second barrel in the mix. Double the work, I know.

I primarily work on Classic Double guns, but I have a real appreciation for early 20th century European built Mauser Sporting rifles.

I am starting with an Interams Mark X action that was originally a 30.06 caliber.

I have started some of the initial work needed on the action for the build, but before I go much farther, I am wanting to nail down what I am going to do for calibers.

I was thinking one barrel for deer/big game and the other in a smaller varmant caliber. My original thoughts were .270 Win and 22-250 Rem.

My concern is making sure that the action will feed both rounds with no issues, so my thoughts were to choose two that are as similar to each other in size. The 30.06 is .473 Rim diameter and most popular cartridges are also .473 Rim diameter or very close so I am good there from a bolt face/extractor standpoint. But the length of the cartridges as compared to each other is my concern.

The action's starting caliber (30.06) is 3.34" overall length. Most all others are going to be shorter than that, so reducing the size of the mag box might be a given.
I am kind of using the 22-250 Rem as my starting point and then trying to find a good bigger game cartridge that is close enough.

22-250 Rem is 2.35" overall length and case length of 1.91".

.308 Win: 2.80" / 2.01"
.270 Win: 3.34"/2.54"
6.5x55mm: 3.15" / 2.16"
.280 Rem: 3.33" / 2.54"
.257 Roberts: 2.77" / 2.23"
7x57mm: 3.07" / 2.24"

Based on a quick survey like this, it looks like the .308 Win or other calibers in that family might be the best match to the 22-250 Rem as far as dimensions.

Any other suggestions?

Would the .5" difference in overall length cause major issues in cycling both rounds well in the same action?

Thanks