grip pistol in right hand,remove clip,on front of barrel slide lever in opposite direction, pull back breech and slowly move toward front while unlocking slide lever. once past lever, barrel and recoil spring are exposed..lift tabs and remove short barrel and spring. that's it. do so carefully or you will lose spring.
Colt 1911 .45 serial # 171885 was manufactured in 1917.
The Colt 1911 was designed in 1897 and adopted by the US Army in 1911.
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Good pistol
The Colt government 1911 .45 with that serial number was made in 1944 by Remington Rand
Colt 1911
That Colt .45 government model was made in 1918.
made by Colt 1918....................
45 ACP
Your colt model 1911 commercial (that is what the C stands for ahead of the serial number) was made by colt in 1917.
Your Colt model of 1911 dates to the year 1918,with the serial number that you have supplied.
Proofhouse.com has Colt sn data.