So What Caliber Now ?

Oh Mike this is a teaser! OK lets see what your parameters are. 30-06 case head, cast bullet caliber, for coyotes, groundhogs etc.
Ok switch on thinking cap--- ouch that hurts!!! Guess I don't use it enough.
OK here come the input data-- I shoot cast in a 22-250 with a 1/14" twist barrel and it just loves the NOE copy of the 55gn RCbS at about 2000 fps though the NOE version is 62gn. Am I suggesting a 22-250 ?-- no but its performance with cast may shed some light on what I will suggest. Were it my project I would strongly consider a 250 Savage with 1/10" twist barrel. There is a good wide range of cast bullet weights in 25 caliber. We have maybe 10 in our 25 cal line ranging from 65gn to 125gn. What the 22-250 offers as a cast bullet rifle the 250 Savage will multiply. In 25 caliber you would have a superb varmint rifle for cast bullets but if you want to use for bigger game it would still be well suited to the task. We have a couple folks reporting on using our 125gn 25 cal bullet in the 25-35 win for deer and report very good results the 250 Savage will equal the 25-35 at about 3/4 throttle.
Truth be told I have been lusting for a 250 Savage for these very reasons.

Well yea that too. Its just that well there always seem to be a couple 30-06 rifles lying about but I have never had the opportunity to try a 250 Savage. There have been several 257 Roberts both standard and Ackley and several 25-06 but never a 250 Savage.
I had been considering a 257 Kimber a 25 caliber on the 222 mag case or a 25 Sharps a 25 caliber on the 223 case. This because they claim performance equal to guess what a 250 Savage. I was taught if you want milk go to the cow.
I really like 25 caliber weather large or small and the 250 is about middle of the road for case volume. Consider that one of the most popular according to sales chamberings today is the 6.5 Creedmoor a cartridge based on guess what the 250 Savage and necked up .006"
The only issue I can think of may be with the shorter cartridge feeding in a controlled round feed action. I just built a 260 Rem a short cartridge on a long Savage action and it feeds as slick as can be but it is a push feed action. A controlled round feed action may act differently.

I am whole heartedly a Charles Newton fan and admire his cartridge design genius. Some of the cartridges he designed while employed by Savage were the 250 and 300 Savage as well as the 22 Savage Hi-power.
While under his own employ before his shop burned he designed and offered in a rifle also of his design the 256 Newton in the first model Newton rifle. I have had the distinct pleasure of for a time owning a first model Newton rifle chambered in the 256 Newton cartridge both of which I have high praise for. The current new fad long range cartridge is the 6.5 Creedmoor a very close facsimile of the 256 Newton. Charles thought on a level that was ahead of his time and certainly ahead of powder burn rate availability.

The 6.5 Creedmoor is based on the 250 Savage case but should be considered as an improved Ackley version. Truth is there is very little difference between the 250 Savage and the 6.5 Creedmoor other than about .006" difference in caliber and the Creedmoor uses the improved case shape. The 6.5 has about a 257/8 bore and a .264 groove while the 250 has a 250 bore and a 257/8 groove. I think the cast bullet design availability favors the 25 caliber. Another plus in favor of the 25 caliber version for cast bullets is that the 250 Savage uses a slower twist than does the 6.5mm version. The creedmoor uses a 1/8" twist while the 250 originally used a 1/12" twist but often on custom builds uses a 1/10" twist. An perhaps interesting note is that of all the calibers we sell cast bullets in 25 caliber is by far the best seller.
Another interesting note is that when Chas Newton designed the 256 Newton he designed it to be a 25 caliber. He was importing his barrels from Europe and their 25 caliber equivalent was 6.5mm or .264 caliber. Instead of trashing the project he just went with the .264 caliber but stayed with the 256 for the name of the cartridge.

Generally re-lining a barrel is not recommended for cartridges in the 55,000 + pressure range.
Personally I would not overlook some of the less expensive barrel makers like ER Shaw. I have not checked pricing but think they can install a chrome molly blued barrel for about $300.00 total. I was just looking at their cost for a pre fit Savage barrel in stainless steel and the cost was $250.00
Since your starting with a milsurp receiver your not building a bench rest quality rifle so to my thinking why put on the best quality (most expensive) barrel.
I have a couple Shaw barrels and have no disappointment with them in the accuracy department. I do prefer cut rifling over button rifling but now even some of the high end barrels are button rifled. Maybe the best barrels are hammered but hammer forging is not readily available from the majority of barrel makers.
I tried a Walther barrel with polygonal rifling which is not really rifling but all flat surfaces and it shot very well. I felt though that for long range shooting the polygonal form of rifling gave a greater degree of spin drift than conventional shallow groove about .004" per side as opposed to the paddle like surface imparted to the bullet by the polygonal system.
Perhaps I am beginning to ramble so will just say don't rule out ER Shaw just because they are less expensive. Go to their site and have a look see.

A 1/10" twist will handle any 25 cal bullet weight/length you could conceivably want to shoot.  1/10" is standard for the 27 Roberts and 25-06 and handles the longest bullets in that caliber. Twist rate is always a compromise as slower twist rate is less stressful (torque) on cast bullets but as twist rate and correspondingly rotational velocity is decreased it also reduces the length/weight of bullet that it will stabilize.
On the other hand when shooting jacketed bullets the slowest possible twist that will adequately stabilize a bullet will also yield the highest possible velocity at normal pressure because of the reduced torque/resistance of the slower twist, another balancing act.
The 250 savage was originally offered with I believe a 1/14" twist or possibly 1/12" I will have to look it up to be sure. The reason for the slower twist was purely a marketing ploy in that savage set out to offer the first factory cartridge to achieve 3000 fps thus the full name of the cartridge 250/3000 Savage. They did it by using the slowest possible twist that would stabilize an 87gn bullet. They could not get a 100 gn bullet to go that fast so optimized the twist for the 87gn bullet weight to achieve their goal.
As a general rule cast bullets of equal caliber and weight of jacketed bullets are shorter in length than their jacketed counterparts. The reason is the homogenous density of cast bullets. It is entirely possible that the slower 1/14" twist will stabilize up to a 100 gn cast bullet or even slightly over 100gn. You just have to decide how versatile a rifle this will be and if it will see dual use of jacketed and cast bullets.
Just so you wont be frightened about the 1/10" twist if that is all Shaw offers in 25 cal I have done some darn good cast bullet shooting with 1/10" twist barrels.

When I built my first 6.5-06 Ackley I decided on a 1/10" twist as opposed to the standard 1/8" twist. This because I felt I would not use this rifle with the heaviest bullets in the caliber but instead would aim at a single bullet weight at about the middle of the bullet weight range in that caliber which was 100gn. This also because I wanted the highest possible velocity with the 100gn bullet. My hope and expectation was for 3500 fps but my pet load for the rifle exceeds expectation by a decent margin at 3690 fps.

Yes across country! Sometimes I have to invade sovereign air space and shoot from public land over private land and back onto public land. So far my launchings have not been intercepted en-rout by those forces protecting the sovereign air space over private land.
BTW I have decided to lighten up a wee bit on that load because after three loads primer pockets become noticeably loose.

Keep right on chuckling!! Best to you on your project. Keep us informed.

You know I am going to want to shoot it.

Lord willing !!!