Actually, from your picture I can see an 11deg crown cut to the bore.
Other than a thorough cleaning with a GOOD copper remover, I wouldn’t touch it!
CHOOT IT!
I’d first try a 117gr Sierra GameKing over 51.0gr of IMR4831. That’s 1.0gr below max in the Nosler manual and 0.6gr under max in the Hornady manual but is a KNOWN accuracy load. Roughly equivalent to most factory “advertised” loads.
A friend who passed away some time ago, had a Cooper Arms M24 (iirc) single shot b/a w/26” bbl that shot TERRIBLE! He had David Sams work it over: blue printing the action, squared the barrel, cut and recrowned the muzzle to 24”, and glass bedded the action in the marvelous stock. It would then shoot “bug holes” at 100yds. He won several matches with it in the light varmint class bench rest matches. IIRC, he was using the Sierra 87gr FB HP over 52.5gr of IMR4350. He only used it on “windy days” where the 22 and 6mm crowd would get wipped by the wind… he said the bullet wasn’t in the air long enough to get blown out of the “bullseye”.
A “sleeper” load is 43.0gr of IMR4320. A friends Interarms MkX with the 117gr Sierras routinely shoots 1/2” three shots at 100yds. He’s killed dozens of deer with it! Longest shot was 310yds down a power line ROW in SW Pennsylvania. He had to wait on the deer to cross out of W.Virginia to the Penn side, as property is in both states. The load “only” chrono’s 2,800fps but kills deer like lightning! I’m not sure, but I believe it was one of Ken Waters “Pet loads”.
I use the 100gr bullets in my .25’s for deer. I bought 500 Hornady “blems” from MidwayUSA about 15yrs ago. They usually completely penetrate our 135-175lb bucks with a spine or shoulder shot from the .257Robt, but seldom from the .257Wby. Never had a problem recovering a deer! They always bang-flop! But then again, my book max load of RL25 is running them at 3,650fps… a recovered bullet weighs 67gr in a classic mushroom. The “Bob” with the classic 100gr load (45gr of IMR4350) runs a 100gr bullet right at 3,000fps. The 21” .25/06 should easily get 3,200fps, so you’ve still got plenty of punch.
I’ve killed over 100deer with the “little Bob” since I had it built in ‘83. Longest shot was a mule deer doe near Lincoln, Montana hunting along the Marias River breaks. 431yds “lased”, high shoulder shot bang-flop with an 85gr Nosler B.T. (My prairie dog load! 46.0gr H380 for 3,400fps)
Biggest deer I’ve ever taken was with a Hornady 117gr BT Interlock, 210yds, bullet hit left ham and was recovered from right shoulder. Shot him as he was jumping a barbed wire fence! Chasing a doe I almost shot before I saw him. He “bottomed out” a 200lb scale, field dressed!
I’m a big fan of the .25’s! I “only” have three at the present!
A .257mag Weatherby Vanguard, (24”bbl)
A custom M98 Mauser w/E.R.Shaw .257Roberts, (22”bbl),
And, a Marlin M1893 in .25-36Marlin (think .25-35win ballistics w/26”bbl).
I once had a Ruger M77/MkII. Generally, it was a 2” gun at 100yds, but had an affinity for the Berger 115gr VLD.with 45.0gr of IMR4831. Very devastating on dreer. I only recommend chest shots as it is very destructive. My M98 doesn’t especially care for it, though.
I’ve heard a rumor that there was a female big game guide in Alaska that for a number of years used a .25/06 as her “backup” gun! She had even killed several grizzly/browns with it. Supposedly she was using either a Nosler 120gr Part or a Swift 120gr A-frame. She only switched to a Savage .375 (don't know if a H&H or Ruger) as a guest/client gifted her the custom rifle and ammo…
As regards the crown, Mr Walker of formerly Walker Arms of Selma, Al used that type of crown on guns he recrowned fwiw… a best friend and hunting buddy had a Winchester M94 AE in 7-30Waters, cut to 17.75”. (Mr Walkers decision!).. I’d be branded a liar if I said how accurate it shot a Speer 130gr HP…
