picked up a very clean J.C.Higgins Model 50 .30-06 rechambered into the .30-338 calibre. Action is Belgium made and feeds quite nicely. Nary a ding in the stock. Bluing must be 85% plus.Swivel is very unique, has a threaded insert into stock both fore/aft, depress a center button and out it comes. Swivels freely and abit noisy but that is okay. Anyways looking for good loading material is not easy for this. Heard one fella say use .308 Norma Mag data and start 5% less than max. Anyone here that has some info on this calibre?

If it's a 338-06 (parent case 30-06), then Nosler's manual #3 has some good data. I have to leave to go to work in a couple minutes-If no one has data, I can give it to you tonite around midnight EST

If it uses a belted case, then my guess is that it is chambered for the .30-338 Mag wildcat. The .308 Norma Mag case is very similar but not identical.

From http://www.reloadbench.com/cartridges/w30338win.html:

30-338 Winchester Magnum

Historical Notes:

This cartridge was developed specifically for use in 1000 yard benchrest competition. It was created by simply necking the 338 Winchester Magnum to 30 caliber and almost exactly duplicates the 308 Norma Magnum (Norma's commercial offering has slightly less case taper and is slightly longer).

General Comments:

The 30-338 Winchester Magnum fills a void in Winchester's Magnum line, created when Winchester introduced the 300 Magnum. The 264 Winchester Magnum, 338 Winchester Magnum, and 458 Winchester Magnum all share a 2.5 inch case length. Evidently to avoid direct competition with existing 308 Norma Magnum and to better compete with the well established, and substantially longer, 300 Weatherby Magnum, Winchester opted to increase case length and push the shoulder forward on their new 30 caliber magnum (actual usable capacity increase was marginal). The Wildcat 30-338 is likely exactly what Winchester would have offered had Norma not beaten them to the punch. Ballistics are very similar to the 300 Winchester Magnum, despite the slight reduction in powder capacity. Compared to that commercial chambering, a slightly longer case neck provides superior purchase for longer bullets.

Source: Cartridges of the World

If it is a .30x.338 belted, this is basically the .308 Norma mag. I believe the current Hornady manual has data. You could use .300wm data, start low & work up.

yes it is a .338 necked down to .30cal.-- I have a speer #13 manual that lists the 308 Norma Mag and you say it is ballistically the same as I caught that elsewhere too. I have not loaded a round except to measure bullet to rifling and magazine. With a dummy round the bullet to rifling is 3.570" and magazine is 3.345" so I made up a dummy to 3.340" but there is quite abit of freebore isn't there? Approx. 3/8" for the ogive contact-is that acceptable in terms of real accuracy? I suspect to use the Scirocco quite often, if Wthby is a 1/2" freebore where does this leave me? I realize the closer to contact of rifling the better. Are many rifles that are rechambered like this. Wonder if the smith gone abit too far.

grizz, all rifles are diff. as to best accuracy. I usually load to longest OAL my mag. allows as long as it doesn't crush into the lands. Some bullets, like monometals, actually like being off the lands so loads osme up & give it a try.

If freebore is an issue try the Barnes TSX.
They are made of mostly copper and are therefore long for weight. Besides they should be loaded off the lands some .050 for best results. And their terminal performance is like lightning.

I would stress about freebore until after I've shot it. I've had a number of rifles over the years that had OAL's to the rifling much longer than the magazine would allow yet they all shot more than well enough for big game. Try it first.

The issue of freebore depends on the dimensions of the throat. If the throat is paralell or nearly parallel and 0.001" over bullet dia, then it should be a shooter of the first order even with the bullets well off the lands.

If the throat is more of a funnel, ie highly tapered, much larger than bullet dia, then getting groups with bullets well off the lands may not be in the cards for you.

Handloader had an article about the 30-338 a few years ago, I'll try and dig it up, scan it in pdf and e-mail it to you.