Most cheap 30-06 factory ammo is loaded for deer hunters, so performance is optimized for that. Buy it, use it in confidence, and don’t sweat the twist rate. 1:10 is standard for the 30-06 for one reason: the 30-03 needed it for 220-grain bullets and it was too expensive to rebarrel 75,000 rifles when we switched to the 30-06. The gubmint pulled the barrels, cut off the back ends off, rechambered them, and reinstalled them. If we were starting today without that limitation, the twist would probably be 1:12, which is standard for the 30-30 and the 308 Winchester.
As for the rifle itself, I applaud your choice. I live just outside Tacoma, WA, where Tradewinds used to be. We see lots of these rifles on used racks around here and I've owned six or seven of them, all in 30-06.
Different variants got different model numbers, but 1640 typically refers to the action. I’ve seen three variants on the 1640 action. The first and least common has a Monte Carlo buttstock and a Mannlicher forend. The second has a Monte Carlo buttstock and a Schnable forend. The third has a standard buttstock (lots of drop at the comb and heel) and a Schnable forend. The first and third types are usually walnut. The second is usually a light-colored hardwood that may be either birch or beech.
Unfortunately, recoil in all three types tend to split the web of the stock, but glass bedding fixes that. All of mine had 1:12 twist barrels and most were very accurate with cheap factory ammo.
Barrels came in three lengths: 20.5”, 22”, and 24”. Every Mannlicher gun I’ve seen had a 20.5” barrel and all Monte Carlo/Schnable guns had 22” barrels. I’ve seen all three lengths on the standard/Schnable rifles.
All three are very light, and IIRC, all have low iron sights. The standard/Schnable rifles are stocked perfectly for these sights, which means they’re too low for a scope. But if you put a peep on them, then you have a slick little carbine that’s no longer or heavier than a 30-30 but has twice the reach. The Monte Carlo/Schnable guns fit me almost perfectly and are ideal for offhand shooting. They’re my choice for scoped use.
I've owned three 20.5” guns in 30-06 and I think the barrel is too short for it. That said, the only one I still own is a 20.5” that my father gave me. A few years ago, my son used it to clobber a 200-ish pound hog in California with a 165-grain Remington CoreLokt bullet handloaded to 2,550 FPS. That hog was bigger than most deer and everything worked perfectly.
A few other things to know about them:
- Most of them have military-type triggers, which are a lot like Glock triggers. Timney makes the upgrade you need.
- At some point, any 1640 will stop ejecting and cases will dribble out of the action. That's because the ejector is tensioned by a little leaf spring that's held in place by a screw and the screw backs out. Re-tighten the screw, add a dab of red LocTite, and you'll be back in business.
- The serial number is on the barrel, not the action. If you rebarrel it, then your smith needs to carry the number over.
- Many commercial 98 aftermarket parts will work, often with little or no fitting. So will most tuning tricks that apply to Mausers. Brownell’s is a good source of information on parts for them.
- The 1900 action (push feed) replaced the 1640 in the late 60s.
- The 1640 had two types of bottom metal: steel and alloy. You can tell by the floorplate latch. On earlier guns, the latch is a folded steel spring. On later guns, it’s a protrusion inside the trigger guard like on a Model 700 Remington. Stocks inletted for one won’t work with the other.
- The front of the alloy magazine can get dented under recoil if you shoot a lot, but this may not be a problem with cartridges less powerful than the 30-06 or if you don’t load the 30-06 to the maximum.
If you like older lightweight rifles with wood stocks and you hunt in bad weather, a 22” 1640 glass bedded into a beech Monte Carlo/Schnable stock with a 4x scope is a superb choice.
I think they stand up well to the pre-64 Model 70 Featherweight.
Let me know if you have questions.
Okie John