Warning

 

Close

Confirm Action

Are you sure you wish to do this?

Confirm Cancel
Member Login
Site Notices
9/19/2017 7:27:10 PM
Posted: 10/27/2003 9:14:29 AM EDT
Just got an upper and went to sight it in today and it shoots WAY left...looks like the fsb is canted. I got the upper used and it's had a float tube put on, it's a colt hbar 20. Just wondered what makes the fsb cant like this.
Link Posted: 10/27/2003 9:53:04 AM EDT
[Last Edit: 10/27/2003 9:55:36 AM EDT by NoCompromise]
what is the B in FSB? if the barrell was removed to install the float tube, sometimes they don't realign the barrel, perfectly. I have one that is a little canted but nothing that I cant adjust with windage adjustments.
Link Posted: 10/27/2003 5:26:09 PM EDT
Link Posted: 10/27/2003 7:43:05 PM EDT
Originally Posted By NoCompromise: what is the B in FSB?
View Quote
FSB = front sight base Another cause is that it came from the factory that way.
Link Posted: 10/27/2003 9:19:28 PM EDT
hmmmm.... I've always know it to be the Front sight tower. I knew what he was talking about though.
Link Posted: 10/27/2003 11:52:07 PM EDT
Originally Posted By NoCompromise: what is the B in FSB?
View Quote
[url=http://ar15.com/forums/announcement.html?b=3&f=66&id=188]Glossary[/url]
Link Posted: 10/28/2003 6:32:38 AM EDT
Yeah, the weird thing about this is that it's canted to the right. I would think if it were overtorqued on installation and the alignment pin bent it would be canted to the left? Maybe when the FSB pins were reinstalled they were hammered a little too hard, enough to roll the sight base slightly to the right?
Link Posted: 10/28/2003 8:24:39 AM EDT
Originally Posted By kicker9898: Yeah, the weird thing about this is that it's canted to the right. I would think if it were overtorqued on installation and the alignment pin bent it would be canted to the left? Maybe when the FSB pins were reinstalled they were hammered a little too hard, enough to roll the sight base slightly to the right?
View Quote
If an action block/upper vise block is used to mate the barrel to the upper receiver the FSB will cant to the right. This is what most people use for mating these two parts. If a barrel vise block is used, it will cant to the left.
Link Posted: 10/28/2003 8:37:54 PM EDT
gee I thought canted FSB where just limited to the SAR AKs....this is the first I heard of a AR with a canted FSB. what did colt do, import a bunch of gypies from romania to assemble their rifles?
Link Posted: 10/29/2003 1:15:25 AM EDT
Originally Posted By sfcret: what did colt do, import a bunch of gypies from romania to assemble their rifles?
View Quote
You MUST be an AKer. [:D] Colt doesn't have this problem.
Link Posted: 10/29/2003 5:55:53 AM EDT
[Last Edit: 10/29/2003 6:02:15 AM EDT by kicker9898]
[romanian accent]Ve hab vays of making your rifle shoot sidevays[/romanian accent] [smash] <----- Romanian gunsmith Actually I like my AK's too, my romanian SAR1 doesn't have a canted FSB...lol. Oh well, I doubt it came from colt this way, but it's a nice rifle anyway, I'll get the sight fixed up, just needed opinions on what to do to fix it...so is there any way to tell if the pin is bent when I take it out of the receiver? Also...if using a receiver block commonly causes this problem how is this to be avoided?
Link Posted: 10/29/2003 10:42:28 AM EDT
Link Posted: 10/29/2003 1:44:04 PM EDT
Thanks for all the good info guys...I should be able to get it straightened out now. Appreciate it. Jason
Link Posted: 10/29/2003 9:43:26 PM EDT
Originally Posted By Troy: Finally, you can use a guage (if you have a flattop, you'll need a detachable carry handle). Brownells sells them, but it's really a piece of drill rod with a pointed end that you clamp into the channel on the carry handle. If the point is pointing straight at the front sight, you're good. If not, then you know how far the alignment is off, and can shim or adjust the barrel as needed. -Troy
View Quote
Ooooooo! That sounds neat, got a link? I have no idea what to search for on their website.
Link Posted: 10/30/2003 4:24:56 PM EDT
Link Posted: 10/30/2003 8:21:22 PM EDT
Originally Posted By Troy: I just looked and didn't find it (maybe discontinued?), but it was WAY too expensive anyway. Find a local machine shop and have them machine a point on a piece of stainless rod that will in your carry handle. -Troy
View Quote
Oh well, I only wanted it if it wasn't going to put too much of a dent in my wallet anyway. Thank you for taking the time to look.
Link Posted: 11/19/2003 9:07:49 AM EDT
Hey kicker9898, did you get the canted sight problem fixed, and how hard was it to do it yourself?
Link Posted: 11/19/2003 9:20:20 AM EDT
Oh yeah...wasn't hard at all. Just followed Troy's advice, put new Moly lube on the threads, had someone hold the barrel so it wouldn't have a tendency to "follow" the torque...lol. Not a problem, shoots straight as can be. But, I also ended up replacing the HBAR with an M4 Dissy barrel, like it much better now. Now the only problem is that I have a spare barrel laying around begging for a project upper...lol. Jason
Link Posted: 11/19/2003 9:41:09 AM EDT
thanks for the update. Looks like I'm going to have the same problem as you, I'm going to replace my 20"HBAR with an A2 profile barrel. the HBAR is just too heavy for me.
Link Posted: 11/19/2003 12:58:58 PM EDT
[Last Edit: 11/19/2003 3:08:06 PM EDT by 556Cliff]
Two more questions, how many pounds of torque do I use on the barrel nut when I put the new barrel on, and after the barrel is installed do I check the headspace? Thanks 556Cliff
Link Posted: 11/19/2003 1:46:38 PM EDT
Link Posted: 11/19/2003 3:18:30 PM EDT
Thanks Troy, That answers that question but after the barrel is installed do I need to check headspace?
Link Posted: 11/19/2003 5:26:28 PM EDT
Link Posted: 11/19/2003 7:32:21 PM EDT
Originally Posted By Troy: On the third tightening, tighten to 35 ft/lbs. -Troy
View Quote
It's 30ft/lbs according to the TM. Not trying to be a "corrections jerk", just that for MANY people 30-35ft/lbs is where it lines up and not again until 90-100ft/lbs.
Link Posted: 11/19/2003 8:11:47 PM EDT
Originally Posted By Troy: In an AR, headspace occurs between the barrel assembly and the bolt. All you need is these two components to check the headspace of the barrel. Installing the barrel into an upper won't change this in any way. -Troy
View Quote
So is that a NO I don't have to check headspace[?]
Link Posted: 11/19/2003 10:37:36 PM EDT
[Last Edit: 11/19/2003 10:41:51 PM EDT by Tweak]
Checking the HS is not necessary (but not a bad idea) if the barrel and bolt have been HSed previously. Switching the barrel and bolt into a new upper will not change the HS. Changing the barrel and/or bolt can. ETA, wyv3rn's got the torque value correct according to the latest 23&P C6. The different values come from different manuals or different changes to the manuals. Doesn't matter much, tight is tight, loose is loose. 30 ft/lbs isn't a lot of torque.
Link Posted: 11/20/2003 6:10:35 AM EDT
If you have a new barrel or bolt, yes, check HS. All you need is the go and field gauges, you can skip the no-go.
Link Posted: 11/20/2003 7:27:38 AM EDT
Thanks guys, that answers my question.
Top Top