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So my previous post about this rifle had reminded me about the strange way this A2 was set up when I first bought it. This is a completely different topic so I figured I would just create a new thread. Also let me just say that I wasnt able to get a lot of information about the reasoning for this set up from the gentleman I had bought it from other then he never had any problems with the couole hundred rounds he put through it and thats how he bought it. Anyways the picture Im posting with this is the rifle right after I originally bought it from this gentleman via private sale (yay Arizona). So heres a rundown of how this was set up: Bushy XM15-E2S lower (Windham BFI days), Colt A2 upper, Colt 5.56 1/7 20" barrel, low pro gas block (non adjustable), rifle length gas system, free float quad rail, Colt "half moon" BCG, fixed rifle stock with a carbine buffer spring and a carbine buffer and lastly a Giessele SD3G flat faced single stage trigger.

So heres what I didnt and still dont understand about how this rifle was set up: Why the heck would you use a carbine length spring and buffer in a rifle length fixed stock with a 20" barrel with a 1/7 twist and a rifle gas system? I thought maybe the gas block is adjustable then that would sorta make sense but not its not. So I was looking at this A2 carry handle upper with no FSB, a low pro gblock, ff quad rail, a rifle stock and gas system but with a carbine buffer spring and buffer... and ofcourse the 20" 1/7 barrel. Lol I was like what in the .. did I get myself into.

I was thinking it might of had something to do with this Giessele SD3G trigger it has because.. its fast.. like real fast. But if im correct Im pretty sure you would want to beef up to a heavier buffer weight when your cycling at higher rates and you would want to lighten things up when firing slower rates to speed things up.. so Im still just boggled honestly. Im not sure if someone who had it before me just threw a bunch of parts together for a quick sale but the guy I purchased it from said it ate about 500 rounds flawlessly.. IF he was telling the truth though.. I didnt care to find out lol. Any ideas of why someone would have this set up? View attachment 157014
 

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I suspect the person you bought it from was attempting to put together a National Match rifle. The Gieselle trigger group, 1/7 barrel, and carry handle configuration are quite popular in the Bullseye competition community. It's missing a front sling swivel though, which is throwing me off, so I could be wrong.
 

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I suspect the person you bought it from was attempting to put together a National Match rifle. The Gieselle trigger group, 1/7 barrel, and carry handle configuration are quite popular in the Bullseye competition community. It's missing a front sling swivel though, which is throwing me off, so I could be wrong.
Ahh gotcha that would make sense then. I couldnt tell left from right when it comes to National Match so thank you for that. Also that rail has QD sling swivel attachment points on both the front and rear aswell as both left and right sides of the rail. So your suspicion might possibly be the answer my friend
 

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Check the stock buffer tube for evidence of a spacer block. To use a carbine buffer and spring you would need to change the depth of the spring/buffer tube, it is too deep in stock form. The inside depth of the buffer tube should be 9 1/2-9 5/8”. To be set up for a carbine spring and buffer the tube would have to be shortened internally by a good 2-2 1/4 inches. That could be done by stuffing a dowel down the tube. Once that is done, the carbine spring and buffer would work fine.
Remember that the carbine is the harshest operating system, the longer systems are more docile in operation.
 

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Plenty of mid length and rifle length gas systems using the “carbine” buffer system. It seems that system is more descriptive of the adjustable stock than of the type of upper. The shorter buffer pieces go with the adjustable stock. Granted you can get heavier buffers and springs to tune both of those systems.
 

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Discussion Starter #6
Check the stock buffer tube for evidence of a spacer block. To use a carbine buffer and spring you would need to change the depth of the spring/buffer tube, it is too deep in stock form. The inside depth of the buffer tube should be 9 1/2-9 5/8”. To be set up for a carbine spring and buffer the tube would have to be shortened internally by a good 2-2 1/4 inches. That could be done by stuffing a dowel down the tube. Once that is done, the carbine spring and buffer would work fine.
Remember that the carbine is the harshest operating system, the longer systems are more docile in operation.
The buffer tube did have a spacer but it wasnt on the inside of the tube but actually on the outside of it almost like a cap near the rear end of the rifle in between the tube and the butt of the stock. It was a rifle length buffer tube as well. Apparently the original A2 fixed rifle stocks required a spacer to sit in between the butt end of the stock and the back of the tube. I dont recall anything inside the tube this was a big reason why it didnt make sense to me. I remember pulling back the charging handle to test function and when letting go it almost felt as if there was no power behind the action of moving the bolt forward if that makes sense. Like if I went to rack it with the muzzle pointed upwards towards the sky I dont think the bolt would be pushed into place. Im starting to think the dude was BSing me when he said it was eating anything he put into it. Probably just threw together random parts for a quick sale. Price was good tho and I basically rebuilt the whole dang thing before shooting it anyways so hey cant complain
 

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Yeah, the tube is originally designed for the A1. The spacer came along with the A2 having a longer stock.
Even if it has the 12” a1/a2 spring (the carbine has a 10” spring) that carbine buffer is too short for proper operation.
 

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Yeah, the tube is originally designed for the A1. The spacer came along with the A2 having a longer stock.
Even if it has the 12” a1/a2 spring (the carbine has a 10” spring) that carbine buffer is too short for proper operation.
^^^
This...
The spacer is used in a rifle configuration, not a carbine.
 

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Lifeichose, Here's a picture of a carbine tube, end plate, castle nut, spring, and buffer. It's a totally different attachment system than what the A1 or A2 rifle stock uses.
20201129_141702~2.jpg
 

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Discussion Starter #10 (Edited)
Lifeichose, Here's a picture of a carbine tube, end plate, castle nut, spring, and buffer. It's a totally different attachment system than what the A1 or A2 rifle stock uses. View attachment 157144
Right I understand that. The guy had a carbine spring and a carbine buffer inside the rifle buffer tube without any sort of spacer accumulating the extra space... I would pull back to charge and when letting go it was like a 400 pound blind man trying to slide into home plate after a few rounds of chili dogs, the bolt would barely have enough force to rack a round. Im sure we can all agree that there shouldnt of been a carbine spring and buffer inside that rifle stock with no spacer .. especially on a rifle with a rifle gas system. What gets me is the gentleman told me he put 300 rounds total of both 5.56 and .223 and didnt have one single malfunction. He even said somethinf like "You can damn near shoot full auto with thag Gieselle trigger" haha and he seemed genuine! But I just dont see that happening with how he had this thing set up. So the point of this post was to see if maybe im missing something or do you think he was just full of it? This is all just out of curiosity anyways this gun has long had a makeover since.
 

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It sounds like the guy got some wild hair idea to be able to bump fire it that way ....maybe.

Although what would concern me is the strong possibility of the bolt carrier bottoming out and damaging the carrier key and the rear of the charging handle.
Unless he had a buffer tube spacer in it
But it sounds like he didn't.
 

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Discussion Starter #12
It sounds like the guy got some wild hair idea to be able to bump fire it that way ....maybe.

Although what would concern me is the strong possibility of the bolt carrier bottoming out and damaging the carrier key and the rear of the charging handle.
Unless he had a buffer tube spacer in it
But it sounds like he didn't.
That definitely crossed my mind especially after his comment about the gun mimicking FA. I dont have much knowledge in that type of area but I know the SD3G Gieselle trigger thats in it would definitely back that idea. Not sure if your familiar with that trigger but if not then basically think of a hair pin trigger with little pull weight and a very short reset.. then cut that pull weight and reset time in half and thats the trigger for ya lol its pretty ridiculous.

I made sure to thoroughly inspect the bcg, upper and lower receiver immediately after finding this out. I replaced the stock, receiver tube aswell as the entire buffer system with new and correct components. Then lastly had the headspace checked before I took it to the range. Because your correct, it was only a matter of time before something internally goes array.
 
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