The one thing about Colt Sporter platform which most folks do not realize. Is Colt never throws out obsolete and unusable parts from their military contracts. You can track their use of obsolete parts in their production of the Colt Sporter. Have ever wondered why Colt was still using the slab sided lowers and uppers on their Colt sporter long after the military adopted the upper with the forward assist and lower with the full fence? The reason is quite simple Colt subcontracted for the upper and lower forging in large numbers not realizing that the US military may want to change the upper with a forward assist and a lower with a non-removable front takedown. The original lowers front pivot pin was removable from the lower. The US military did not like that feature and redesigned the lower with a partial fence to retain the front pivot pin spring and plunger to hold the front pivot pin to the lower. This design required a new lower forging. So what do you all of the slab sided lower forgings that you have. Easy you make Colt AR15 sporter out of them until the supply of forging runs out. My understanding is they had so many Model 601 forgings left over they did not run out until the mid 1980s. That's probably over 20 years after the changed to the Model 101 and 602. The HBAR barrels was Colt attempt at making a Squad Automatic weapon which the US military did not buy, so you make a "special" Sporter called an HBAR. Same with the Colt AR Carbine. Most of the parts were from the XM!77E1 and E2 SMG programs which the Army cancelled after the Vietnam War. The barrels of course cannot be used as they are 10.5" or 11.5". But the collapsible buttstock and a new 16" barrel can be used, thus you have the Colt AR15 Carbine. The Carbine provied to be so popular Colt continue to keep making the parts long after the XM177E1 and E2 SMG were history.
The one thing about Colt Sporter platform which most folks do not realize. Is Colt never throws out obsolete and unusable parts from their military contracts. You can track their use of obsolete parts in their production of the Colt Sporter. Have ever wondered why Colt was still using the slab sided lowers and uppers on their Colt sporter long after the military adopted the upper with the forward assist and lower with the full fence? The reason is quite simple Colt subcontracted for the upper and lower forging in large numbers not realizing that the US military may want to change the upper with a forward assist and a lower with a non-removable front takedown. The original lowers front pivot pin was removable from the lower. The US military did not like that feature and redesigned the lower with a partial fence to retain the front pivot pin spring and plunger to hold the front pivot pin to the lower. This design required a new lower forging. So what do you all of the slab sided lower forgings that you have. Easy you make Colt AR15 sporter out of them until the supply of forging runs out. My understanding is they had so many Model 601 forgings left over they did not run out until the mid 1980s. That's probably over 20 years after the changed to the Model 101 and 602. The HBAR barrels was Colt attempt at making a Squad Automatic weapon which the US military did not buy, so you make a "special" Sporter called an HBAR. Same with the Colt AR Carbine. Most of the parts were from the XM!77E1 and E2 SMG programs which the Army cancelled after the Vietnam War. The barrels of course cannot be used as they are 10.5" or 11.5". But the collapsible buttstock and a new 16" barrel can be used, thus you have the Colt AR15 Carbine. The Carbine provied to be so popular Colt continue to keep making the parts long after the XM177E1 and E2 SMG were history.
You can still use the shorter barrels, as long as you pin and weld a muzzle device on them that takes them out to the required 16" length. I recently completed a retro XM-177 commemorative build for a friend (his father carried one in Vietnam while with The Big Red One). We used the original length 10.5" barrel then had my gunsmith pin/weld the 5.5" muzzle device used on the XM-177s which brought it to the legal 16" limit. It was personalized to his father with his name, rank, dates of service, Big Red One logos and the Big Red One motto. Turned out really well and brought tears to his father's eyes when he was presented with it. The scary part is it actually works and his 74 year-old father is still pretty damn good with it!!
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Originally Posted by fjruple
