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Posted: 1/25/2017 3:39:06 PM EDT
| I just noticed my SBR has a canted FSB. The firearm functions fine but I had to adjust my rear sight 9 clicks to he right of mechanical zero which is about half of the total adjustment right. Is this within spec? I took another upper I have out ( colt 723 ) and noticed the sight is canted left. I'm guessing everything is fine and I'm not going to mess with it unless I need to. Anyone here deal with a canted FSB before ? |
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Is this within spec?
Not my specs but possibly within milspec. SBR should magnify problem but not uncommon to see original Colt 20" out 4-5 clicks from factory. Couple clicks just in different shooter variance if nothing else. Cant one yourself that you know is windage correct and see what I'm talking about. Generally I'll tilt mine a tad after 400 rds or so and I get a little tired now that I'm in my twilight yrs. Pretty simple and tells me it's time to quit for the day usually. If I'm dead on and then I'm not it has to be me and not the weapon. If not shooting over 100yds or so really doesn't matter anyway if it's where you want it.. I've never done much with SBR's but I've done a few 16 inch and longer. Mark barrel and FSB as they are currently installed. Remove and re-install FSB for starters. Should install the opposite direction of which way it's off to remedy / correct, fairly easy repair and a little goes a long ways . If it keeps installing to current marked position or worse which I kinda doubt you can purchase a hand reamer from Brownells or such to correct but you don't generally have to remove very much material to correct either. Helps to have a range where you make repairs. Unless trying for perfect windage zero probably can correct the first time. Few FSB removals re-install to exact position before removal on any of them. Thinking 2/0 reamer but may want to confirm before purchasing if you go that route. You can always send it back to whomever did it to start with and have them correct and if reputable shouldn't be a problem. If purchased used or no warranty I'm pretty sure member JT at Retroarms Works? could fix it in his sleep for ya! |
| All you have to do is loosen the barrel nut and see if you can get the barrel to move a little in the correct direction. If the index pin wont move a little in the upper you can widen the slot in the upper a very small amount and check it again. Its very easy with a little file. Dont twist barrel in the upper with the nut loose. , you can crack the upper at the threads. I would not remove the fsb. |
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Quoted:
All you have to do is loosen the barrel nut and see if you can get the barrel to move a little in the correct direction. If the index pin wont move a little in the upper you can widen the slot in the upper a very small amount and check it again. Its very easy with a little file. Dont twist barrel in the upper with the nut loose. , you can crack the upper at the threads. I would not remove the fsb. I've decided not even to mess with it . I can live with a canted FSB , it still zeros with another 5 plus notches of windage to spare. 10" barrels can be picky and I'm not having any malfunctions, more of a cosmetic deal. The barrel is in strait and the gas port is in the correct location. The FSB isn't canted enough to mess with the gas port hole so I'm going to let this sleeping bear sleep. It's a factory colt SP1 barrel I had cut down to 10.03 inches. I did some reading and it seems everything is in spec according to military TM manuals. Like I said earlier my factory 723 upper has a canted FSB to the left that needed 6 clicks left on the rear sight to zero so in the grand scheme of things this isn't really a big deal. |
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OP sounds like a smart move.
As stated I've done very little with SBR's due to legality issues mostly but as previously stated I would bet you could make up that difference learning how to shoot it specifically. Only talking a degree or two tilting in the correct direction for a couple inches at 100 yds or 4 clicks or so. That would put your windage adjustment easily within the milspec for a 20" rifle. The Colt shorty's were never intended to be but so accurate down range. They were made for killing people in close, for concealment or operation in very tight quarters. Unless upper is junk to start with (which I highly doubt yours is) don't ever remove material from the receiver. There is a reason the index pin is removable. Remove metal from the pin not the receiver. A lot of armorers ruined the receivers with the filing mod but they were using tax payer parts / coins and generally weren't the sharpest tacks in the outfit or at the least had any cards in the game. Ever notice most all who start filing on receivers here quickly put the finished product on the EE or similar with some kinda sob story and generally leave the Bubba'd part out of description. |
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Quoted:
OP sounds like a smart move. As stated I've done very little with SBR's due to legality issues mostly but as previously stated I would bet you could make up that difference learning how to shoot it specifically. Only talking a degree or two tilting in the correct direction for a couple inches at 100 yds or 4 clicks or so. That would put your windage adjustment easily within the milspec for a 20" rifle. The Colt shorty's were never intended to be but so accurate down range. They were made for killing people in close, for concealment or operation in very tight quarters. Unless upper is junk to start with (which I highly doubt yours is) don't ever remove material from the receiver. There is a reason the index pin is removable. Remove metal from the pin not the receiver. A lot of armorers ruined the receivers with the filing mod but they were using tax payer parts / coins and generally weren't the sharpest tacks in the outfit or at the least had any cards in the game. Ever notice most all who start filing on receivers here quickly put the finished product on the EE or similar with some kinda sob story and generally leave the Bubba'd part out of description. I've been thinking about this , it does bother me but I don't want a hack job. Tomorrow I'm going to have the barrel pulled and reinstalled to see if I can fix it that way. I don't want to mess with the indexing pin or slot with a file so that then leaves me with one last option. If reinstalling the barrel doesn't work I'll order some oversized taper pins and have John Thomas ream out the holes with the FSB in the correct position and instal the oversized ones. |
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OP don't answer questions just giving something to think about.
Can you do the work or having it done by others? How far were you shooting requiring the 9 clicks of adjustment? I'm assuming not 100 yds. Is the SBR that sweet looking 610 or such build in the other thread or a different build? Did you originally install the barrel on upper or purchase assembled? Is it new, used ? Do you have spare parts? Possibly another member with one of those could chime in as to how much adjustment their identical weapon requires. |
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Quoted:If reinstalling the barrel doesn't work I'll order some oversized taper pins and have John Thomas ream out the holes with the FSB in the correct position and instal the oversized ones. If you decide to have me work on your barrel, don't bother buying oversized pins. That's not how I fix these. I tig weld up all the existing holes/slots/cuts/etc., smooth and refinish, then with a "fresh start", I drill/ream/reinstall the base. John Thomas |
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Quoted:
If you decide to have me work on your barrel, don't bother buying oversized pins. That's not how I fix these. I tig weld up all the existing holes/slots/cuts/etc., smooth and refinish, then with a "fresh start", I drill/ream/reinstall the base. John Thomas It's going in the mail ! |
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Quoted:
OP don't answer questions just giving something to think about. Can you do the work or having it done by others? How far were you shooting requiring the 9 clicks of adjustment? I'm assuming not 100 yds. Is the SBR that sweet looking 610 or such build in the other thread or a different build? Did you originally install the barrel on upper or purchase assembled? Is it new, used ? Do you have spare parts? Possibly another member with one of those could chime in as to how much adjustment their identical weapon requires. Yeah it's the 610 clone  at 25 yards it's 9 clicks and at the 100 yard range it shoots right of impact to the point I can't adjuste it far enough. I had someone else instal the barrel. The barrel is a chopped Sp1 barrel. Good news it it cycles like a boss and if I can't hit you I'll make you deaf or blind from the muzzle blast  this is my first SBR and was so freaking excited, now I'm just bummed lol. Another week or two and I'll be able to be excited again.
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