" What are these things"
You need to get out more.
Those are " US Rifle, 30 caliber, Model of 1917", Primary US Rifle of the US Expediency Force in WWI { more Model 17's used than 03 Springfield's }, they are not P17's, no such animal. Long story made very short. British wanted a new rifle and cartridge to replace the old Lee Enfield 303. It was called the Pattern 14. WWI starts and the British realised that they better stick with the Lee Enfield. The US realising that they would need more rifles, rechambed it to 30-06 { 30 Caliber} and three firms built it, Remington UMC, Remington Arms Co, ( Eddystone ) and Winchester. As stated, more Models 1917's were used than the 03 Springfield. Because there was a Pattern 14, some people mistakenly called it the P { for Pattern } 17. Again, no such animal. This is a very short version of a very long story and a lot has been left out , but it does answer your question, "What are those?".