AR Sponsor
Posted: 11/27/2013 10:13:28 AM EDT
| What's the proper way to fix a canted front sight post? |
|
If you're lucky, you just loosen the barrel nut, align the FSP to the upper receiver rail, and re-tighten. If that doesn't work, then it's probably either mis-installed from the maker, or the originally-installed FSP has been mixed with one from a different rifle. Fixing either of *those* may be a machine shop operation.
Would be helpful to know more about the rifle's configuration, and whether it's new, factory, garage build, etc., and whether it came to you this way, or got this way after work on the gun. HTH GSM |
|
First off, shotgun the upper open and look at the center of the feed ramp against the center of the lower lug.
In this photo, notice how the center of the feed ramp is slightly to the left of bottom center, which would cant the FSB to the left as well. 
So on that note, did the barrel slip in the upper receiver when the barrel nut was tightened, or is the feed ramps centered, but the FSB canted alone instead? Next, need to know if the FSB is taper pin installed on the barrel, or if the FSB is set screw installed on the barrel instead. The reason for the question, if the barrel slipped, then easy fix by just slipping the barrel back into correct rotating in the upper receiver (do not even have to loosen the barrel nut to do this). If the barrel is correctly indexed in the upper receiver, and the FSB is installed via set screws, then you need to transfer heat to the set screw via an old allen wrench and a blow torch on the wrench to first break the loctite bond on the bolts, pull the bolts and clean them, reinstall the set screws with new red loctite, and index the FSB correctly. If the barrel is correctly indexed in upper receiver, FSB is attached via taper pins, then the barrel needs to be replaced, or at least the FSB replaced with a bolt on type FSB instead. The short version of this is the gas port is indexed off the barrel extension pin, and with a canted FSB off the receiver extension pin, then it was the FSB that was not jigged correctly to the pin when it and the barrel where drilled for the taper pins. To correct this, the barrel would need to be tig welded to close the old taper pin channels, then the FSB rejigged and drilled again. By the time you pay a smith to do this, it would be cheaper to buy a new barrel instead. 
|
| It was a factory upper that would shoot to the left a few inches. The feed ramps are centered and and the front sight post didn't look off. I sent it back to stag and they apparently used a machine to apply pressure to straighten the front sight post. So far I have been very impressed with there customer service and they had it in the mail back to me the day after they got it, and they paid for shipping booth ways. I have read that some have fixed this with a rubber mallet. I suppose if I ever need to remove the tapered pins on the front sight post I may need a sledge hammer now |
|
Quoted:
I sent it back to stag and they apparently used a machine to apply pressure to straighten the front sight post. I have read that some have fixed this with a rubber mallet. I suppose if I ever need to remove the tapered pins on the front sight post I may need a sledge hammer now  so full of "What the Fuck" I don't know where to begin.
I have repaired a slew of canted FSB's on AR's and AK's and not a one involved a "machine to apply pressure to straighten the sight post" That would be known as a hydraulic press. Somebody takes a hydraulic press to the FSB of one of my rifles I would beat them with it. That is a "ni$$er rig" fix and it deplorable that a manufacturer would resolve it in such a manner. I would DEMAND replacement. Here is what happens when one would do such: The barrel has to be held to prevent rotation in some manner, I would think either in a barrel vise or by the extension somehow. Then the FSB would have literally tons of pressure applied to it to force it into alignment. So when the "repair" is done here is what you have (or a combination of) A bent FSB (as they are forged usually it would be more likely broken) Bent/broken taper pins Distorted (read destroyed) reamed holes for the taper pins. Twisted barrel. Enjoy your "factory repaired FSB" 
There is a correct way to repair them and as mentioned I have done lots of them. No need to weld the barrel. The old taper pins must be removed and the barrel / FSB is mounted in a fixture that indexes on the extension pin. The FSB is aligned as required and locked in place by the hole for the sight post. Then the fixture is mounted in the mill, the old taper pin holes are indicated in then I shift the table to favor the barrel by .010-.015. That way we know we will get good virgin barrel for the new pins. An 1/8" end mill is used to clear cut the holes all the way through and then before the table is moved an oversized taper reamer is used and new oversized taper pins are fitted. In the case of an AK the same procedure is used but straight pins are used as that is what is used on an AK. The result is a CORRECTLY repaired canted FSB. You got Dicked OP |
AR Sponsor