I have 40+ of neck down 404 Jeffery Brass. I bought these years ago from an estate sale. I was going to fire form them back to 404 Jeffery, but I have more 404 Jeffery brass than I'll ever need.

The cases are approx. 2.840 in length. Some have been fired and a .308 bullet will slide in and out of the case. Most have just been formed in a die.

What the heck do I have? 300 Dakota?

RUSTY, got this off another web site.

The 300 Dakota is based upon a shortened 404 Jeffery case. In any given length cartridge, use of the non belted 404 Jeffery case provides about a 15 percent increase in usable case capacity, compared to the standard belted case. The cartridge provides a significant capacity advantage over the 300 Winchester Magnum and comes close to duplicating capacity and performance of the much longer 300 Weatherby Magnum.

My best guess is that these were prepared for either a .300 or .311 Imperial Magnum. The Imperial Magnum line was introduced about three decades or more ago by a Canadian company. They were extremely close in dimension to the later line of Remington Ultramags, also derived from the Jeffery case.

They offered a 7mm, .300, .311 (this diameter was offered to match the .303 British, still popular in Canada), .338, and .375 if memory serves. I think the company offered proprietary rifles built on the Sako L61R action, and they had an outlet in Washington State through which they distributed in the U.S.

The 311 Imperial is 2.830" long. 2.339" body length and 2.500" to start of neck. I'm putting my $$$ on that one. The 300 Imperial doesn't match up and it's a bit shorter in all dimensions.