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3/8/2010 6:28:38 PM EDT
Hello, i just recently got a great deal on a M4 profile upper but the reason it was so cheap was because the roll pin on the FSB was misaligned and the gas tube is slightly crooked...i put a wd40 straw in the tube and it blows through into the barrel just fine but i havent shot it yet and want to replace it first. Well i'm trying to figure out how to go about it (new AR owner) i'm thinking i could just get a new tube and pin and just drill out the old pin and pull out the tube from in receiver?  anyone have any suggestions on how to go about switching out the tube without removing the FSB?
3/8/2010 6:39:21 PM EDT
[#1]
Yeah, you don't need to remove anything but the handguards & the gas tube roll pin.
3/8/2010 6:43:02 PM EDT
[#2]
thats what i was thinking the only bad thing it cant just drive out the pin, i have to drill out the damn thing
3/8/2010 6:46:00 PM EDT
[#3]
I have driven those pins out before. Is yours jammed or something?
3/8/2010 6:48:07 PM EDT
[#4]
it wasnt aligned during assembly and it doesnt go thru to the other side of the FSB so its basically blind pinned in there
3/8/2010 7:28:33 PM EDT
[#5]
Is it driven flush, or is it sticking out a little?
PS: Sorry about all the questions...I am a curious person, and have learned a lot on this site. Good people here.
3/8/2010 10:38:17 PM EDT
[#6]
Undersize drill it so you don't enlarge the cross pin passage, and you should be able to drive both sides of the remain pin into the gas tube.

If the gas tube is not destroyed, then you should be able to blow the pin remnants out of the tube, and put it back into play.

And before you go to install the new cross pin, chuck it up in drill and spin file taper down the leading edge of the pin so it drives true this time around.
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