View Full Version : Are FSB "married" to barrels?
I have a 14.5" DD CHF barrel. I shaved the FSB to fit under a rail.
Now I have decided I want to go back to using that barrel with a FSB and I want to use the rail with a DD CHF 16" barrel.
Could I order a DD 16" barrel with a FSB, take the FSB put it on the 14.5" barrel and put the shaved FSB on the 16" barrel? Same barrel profile for each, same manufacturer.
Basically will the pins line up?
Possibly, but not likely the holes will line up.
Considering it's from the same manufacturer, they very well may use a jig to drill the holes, so they may line up fine.
No you can not. Each one is drilled individually and unless you somehow get very lucky they are not going to match up.
No you can not. Each one is drilled individually and unless you somehow get very lucky they are not going to match up.
Yea generally speaking it isn't going to work. You can get a new fsb and drill it to work with the barrel but it isn't easy to do.
I've always wondered why this is the case- is it really that hard to come up with some set dimensions for this and standardize?
Even if the military doesn't do it, you'd think the manufacturers could get together and come up with a spec for this- Kind of like how SAAMI works, except barrels/FSBs instead of ammo.
Sure would make life easier...
I have a 14.5" DD CHF barrel. I shaved the FSB to fit under a rail.
Now I have decided I want to go back to using that barrel with a FSB and I want to use the rail with a DD CHF 16" barrel.
Could I order a DD 16" barrel with a FSB, take the FSB put it on the 14.5" barrel and put the shaved FSB on the 16" barrel? Same barrel profile for each, same manufacturer.
Basically will the pins line up?
Basically what those guys said.
But now to me, it seems that if they are both DD barrels, they would have some degree of commonality. You could contact DD and find out what they say. But, if I were you, I would find a retailer who would accept a return on an unused barrel, carefully knock the pins out and see if they mate up. Or you could just buy the barrel and develop another plan if it doesn't work.
Either way, my suggestions take some element of courage.
I tried to swap the bayo-lugged FSB from my 6920 to my older Colt A2 whose FSB is w/o bayo lug: Close, but no cigar. With it in place, the front pin lined up about dead on, the second was off by about 1/32" or so.
Plenty of shops remount new FSBs on drilled seats. Takes a little skill and, at least, a very solid drill press to do it though. For the cost and hassle you might as well buy new and sell the old.
Maybe, just maybe, you could use one pin in each sight and then drill and tap the other end for a set screw, through the bottom, of course. The open holes on the sides of the end with the set screw could be filled with Devcon, or JB Weld, for cosmetic purposes. Now, none of this would work be feasible if the original cross-drilling was not at the exact same angle, or very, very close, across the two barrels. That would throw the windage adjustment off on the rear sight.
Don't slam me too hard if you don't like the idea. It was just a thought.
Thomas M-4
09-21-11, 22:35
The correct way would be to use over sized pins. And ream it to the new over sized pins. But this still may not work depending on how far off the holes are.
I would guess they use the same jig.
I've swapped LMT FSBs before with no issue.
Well the idea of a jig makes me want to take a chance.
Now I just need to find a 16" DD CHF LW mid barrel with the FSB. I will report back after I give it all a try.
I doubt it. We still can't get manufacturers to stop making silly commercial lower receiver extensions or do simple thigns like stake castle nuts and bolt carrier key screws.
I've always wondered why this is the case- is it really that hard to come up with some set dimensions for this and standardize?
Even if the military doesn't do it, you'd think the manufacturers could get together and come up with a spec for this- Kind of like how SAAMI works, except barrels/FSBs instead of ammo.
Sure would make life easier...
I doubt it. We still can't get manufacturers to stop making silly commercial lower receiver extensions or do simple thigns like stake castle nuts and bolt carrier key screws.
There's always going to be someone who doesn't know and/or doesn't care about specs.
Still- if BCM, LMT, Daniel Defense, and other good companies all said "Hey, let's pin our FSBs based on this spec." it would be a great advertising point for those who do FSB modifications.
If I recall, ADCO offers a service to replace pinned FSBs. Contact them for more information
Possibly, but not likely the holes will line up.
Considering it's from the same manufacturer, they very well may use a jig to drill the holes, so they may line up fine.
Yeah I thought my brother was full of shit when he told me my holes wouldn't line up. He was right.
I would call up DD and talk to them. Ask them if they use a Jig type setup for all their FSB's. If they do (all manufactures likely do, just different jigs) you have a good chance of it matching. Before you do anything call DD and ask. They may be able to help you out.
Also for those if you looking to or considering shaving the FSB down, you may want to think otherwise. It works yes, but brings problems of it's own such as this one above. If you change you mind, well...:big_boss:
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