LOL... no it's not. A 1911 .45 caliber is a semi auto pistol. A pistol big enough to chamber that round would be the size of a Volkswagon... It's a .50 caliber made by Winchester Repeating Arms in 1954. It's a US military cartridge used in heavy machine guns and also used in long range sniper rifles.
And why it has a crimped in primer.
That generally designates military use. What's interesting is WHERE you found it. Is that area know to have been used by National Guard guys playing war games ? And if so I still question the use of live rounds. That's NOT a blank.. Is there a military range nearby ? There are .50 cal BMG rifles sold these days for civilian use but that shell casing looks to have spent a bit of time in the ground. Very odd.. I once hit an area in an old NH ghost town though that was littered with .223 & .308 military blank rounds and even found a spent smoke grenade. Turns out the Guard plays war games down in there.
And why it has a crimped in primer.
The 30/06 shell is pretty understandable as a lot of people shoot surplus ammo (and the 30/06 has been popular for a long time now) when they can find it at a good price. The .50 BMG isn't nearly as common outside of military bases and training areas, so that's the oddball of the two finds.
FYI, the M16/AR-15/M-4 use the 5.56mm/.223 cartridge, much smaller than either of the two cases you've found so far. It's pretty common. Since you seem to be collecting a variety of ammo I'm including a pic of the various sized ammo you've found so far and some you appear likely to encounter in that area. From left to right is a 5.56/.223, 7.62/.308, 30/06, and .50 BMG.
