AR Sponsor
Posted: 4/16/2009 4:04:54 PM EDT
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I have two Bushmaster barrels with factory installed FSB's; one has a bayonet lug and the other does not. I want to take the bayo lug FSB off the barrel it's on and put it on the other one. Both FSB's are installed with taper pins. What are the chances that this can be done without any drilling and that the FSB will be properly aligned on the new barrel?
Experts, weigh in! 
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Chances are very slim. Read through the previous pages in this forum. This topic gets covered quite often. OK, I have searched and not found. Linky to said posts? Use the search function for starters. There are currently 200 pages to this forum. 
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Chances are very slim. Read through the previous pages in this forum. This topic gets covered quite often. OK, I have searched and not found. Linky to said posts? Use the search function for starters. There are currently 200 pages to this forum. Thought I said I did that...but I guess the concensus is that it's very unlikely, so I'll go another way. |
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Quoted:
Just grab your hammer and punch and see if you can't knock those taper pins out and remove the FSB's without any trouble. I never had a problem doing this. Removing the FSB pins is not the issue here. The issue is getting a FSB removed from one rifle, and installing it on another rifle. It is very unlikely that the FSB will line up with the barrel since FSB’s and barrels are drilled as a matching set. |
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I actually did this one time with two BushMaster barrels. One had a gas block and one had a regular sight on it. I was prepared to replace both sights with a set screw replacement though I wanted to give it a try before I spent the money. I know my situation was definitely the exception but this one time it worked out perfectly, no canted sight or worry about how the gas ports lined up. I didn't need to coax anything. Just want to clarify this point, I'm with the rest of the crew, chances of this working are slim and I got lucky. |
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lamarbrog,
Take a look at some of the aftermarket gas blocks. Look at how they are secured to the barrel. Clamping designs or set screws are two of the more common methods. If you destroy your original FSB it’s not the end of the world, a new standard FSB can be installed. But, it’s not a job that the average AR owner can do on the kitchen table or out in the garage. Outfits like ADCO can do the job, they have the necessary equipment and the know-how. |
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Quoted: lamarbrog, Take a look at some of the aftermarket gas blocks. Look at how they are secured to the barrel. Clamping designs or set screws are two of the more common methods. If you destroy your original FSB it’s not the end of the world, a new standard FSB can be installed. But, it’s not a job that the average AR owner can do on the kitchen table or out in the garage. Outfits like ADCO can do the job, they have the necessary equipment and the know-how. Thanks for the reply, QUIB. I'm really not very familiar with the methods of attachment of the low-pro gas blocks. I haven't had a chance to look at one very closely, or see how they interact with the barrel. Do the screws go all the way through the old pin-holes? Or just press against the barrel? It doesn't sound very secure... is it safe to do this? |
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Is this just something to do for "play" rifles... Is it secure enough for a fighting rifle? I've been thinking about doing this for a while, to put a free float tube on... but my biggest concern has been the security of the low-pro gas block. I guess the tube covering it would allow some security... |
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The Army SDM rifle uses set screws in a standard style FSB, but I doubt with that type of rifle you’d be out running bayonet drills.
I had the YHM folding FS on one of my rifles. The sight was secure with set screws, worked just fine for the range, but I wouldn’t trust anything mounted in that fashion to secure a bayonet. Would I trust my life to it otherwise…..sure. |
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Quoted: The Army SDM rifle uses set screws in a standard style FSB, but I doubt with that type of rifle you’d be out running bayonet drills. I had the YHM folding FS on one of my rifles. The sight was secure with set screws, worked just fine for the range, but I wouldn’t trust anything mounted in that fashion to secure a bayonet. Would I trust my life to it otherwise…..sure. What I plan to do is have the FSB (which won't actually be a sight, just a gas block) underneath the free float tube w/ 1913 rails. So, I don't think it would even be possible to mount a bayonet with this setup. A 16" carbine length gas isn't much good for a bayonet anyway... not much loss there. Besides, the whole purpose of the rifle is that you don't need to go stab the bad guy...  Thanks QUIB, as always, you're a great help. |
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Quoted:
Quoted:
The Army SDM rifle uses set screws in a standard style FSB, but I doubt with that type of rifle you’d be out running bayonet drills. I had the YHM folding FS on one of my rifles. The sight was secure with set screws, worked just fine for the range, but I wouldn’t trust anything mounted in that fashion to secure a bayonet. Would I trust my life to it otherwise…..sure. What I plan to do is have the FSB (which won't actually be a sight, just a gas block) underneath the free float tube w/ 1913 rails. So, I don't think it would even be possible to mount a bayonet with this setup. A 16" carbine length gas isn't much good for a bayonet anyway... not much loss there. Besides, the whole purpose of the rifle is that you don't need to go stab the bad guy...
Thanks QUIB, as always, you're a great help. I mention the bayonet because for some reason that seems to be the big concern here for a lot of folks, and it usually comes up in the arguments against an aftermarket FSB that mounts in a manner other than with taper pins. |
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I am no expert on AR-15's (or many other things,) but I have been in a lot of manufacturing facilities, and it is that experience which really prompted my original question.
As you may notice, I mentioned in my OP that both barrels were Bushmasters. If I were running the manufacturing operation that attaches FSB's to barrels at BFI, it would be done in a standard process fashion using fixtures and jigs to eliminate as much variability as possible in the placement of the FSB as well as the location, drilling angle, and depth of the taper pin holes; it would very likely be computer-controlled. As a result, this process would be in control and it would be entirely possible to remove a FSB from one barrel and put it on another barrel with no drilling and no misalignment. That is fundamental to efficient (and profitable) manufacturing. It is the difference between what I do in my garage (batch operation) and real manufacturing flow, and it is absolutely essential to the concept of replaceable parts. Maybe they don't do it that way at Bushmaster, but they probably should. (It is interesting to note that one poster was able to interchange FSB's on Bushmaster barrels.) As to another poster's comment that the FSB's were never meant to be removed and replaced, it would seem to me that if that were the case, the FSB's would be welded to the barrels. That certainly would be less expensive and potentially stronger than the current method of attachment. I try to remember that all knowledge can be divided into three groups: the things that I know that I know, the things that I know that I don't know, and the things that I don't know that I don't know. The third group is the largest by several orders of magnitude. Thanks to everyone for the input and the food for thought.
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Tracecom,
I know the sites search feature is not the best, and I hope you did not take my suggestion the wrong way. The previous pages viewable to the membership was increased, with the thought in mind of keeping more of that information viewable. There are a group of topics that quite frequently pop up, if these repeat questions are not researched first, but simply asked over and over, it makes the forum simply that much more difficult to navigate and eventually the new topics or new questions get buried and pushed further and further back. |
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Here are a couple of my threads on this subject.
http://www.ar15.com/forums/topic.html?b=3&f=118&t=422219 http://www.ar15.com/forums/topic.html?b=3&f=4&t=416100 |
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So yalll are telling me that the A-2 FSB is not going to fit the SDM barrel I am having made by CLE? In other words its not "plug and play"?
I dont understand how the sight can canted. I can see the length between the pins on the FSB not being the same as the FSB, but if its mil-spec, and CLE is making the profile of the barrel mil-spec, I would think they would fit. If so, should I send my FSB to CLE before they get done so, they can fit it properly? |
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Quoted:
I am no expert on AR-15's (or many other things,) but I have been in a lot of manufacturing facilities, and it is that experience which really prompted my original question. As you may notice, I mentioned in my OP that both barrels were Bushmasters. If I were running the manufacturing operation that attaches FSB's to barrels at BFI, it would be done in a standard process fashion using fixtures and jigs to eliminate as much variability as possible in the placement of the FSB as well as the location, drilling angle, and depth of the taper pin holes; it would very likely be computer-controlled. As a result, this process would be in control and it would be entirely possible to remove a FSB from one barrel and put it on another barrel with no drilling and no misalignment. That is fundamental to efficient (and profitable) manufacturing. It is the difference between what I do in my garage (batch operation) and real manufacturing flow, and it is absolutely essential to the concept of replaceable parts. Maybe they don't do it that way at Bushmaster, but they probably should. (It is interesting to note that one poster was able to interchange FSB's on Bushmaster barrels.) As to another poster's comment that the FSB's were never meant to be removed and replaced, it would seem to me that if that were the case, the FSB's would be welded to the barrels. That certainly would be less expensive and potentially stronger than the current method of attachment. I try to remember that all knowledge can be divided into three groups: the things that I know that I know, the things that I know that I don't know, and the things that I don't know that I don't know. The third group is the largest by several orders of magnitude. Thanks to everyone for the input and the food for thought.
When was the last time you saw a front sight on any weapon welded to a barrel (home bubba mods don't count)? I know of a few that were silver soldered but that is about it. All military weapons I can think of have been pinned, splined/keyed (M1, M14). With the M16 the FSB is strong enough. Remember it has an aluminum receiver and could be damaged with a hard enough blow by the alignment pin. Or the pin could snap off which a poster here recently did by trying to tighten a flash hider on by sitting on the entire rifle. Welding couldn't help with accuracy either if done after rifling. Maybe it would work if done before but then it might complicate any other operations for machining the barrel. |
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Quoted:
So yalll are telling me that the A-2 FSB is not going to fit the SDM barrel I am having made by CLE? In other words its not "plug and play"? I dont understand how the sight can canted. I can see the length between the pins on the FSB not being the same as the FSB, but if its mil-spec, and CLE is making the profile of the barrel mil-spec, I would think they would fit. If so, should I send my FSB to CLE before they get done so, they can fit it properly? If your new barrel doesn't come with a FSB already on it then it won't be drilled for one. If want them to install one you should contact them or you will have to send it to someone else to have it installed. |
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I called Compass Lake today. They said my A-2 FSB should fit the SDM profile they are doing. They seemed bewildered that I would ask such a question, and ask where I heard such of a thing. I said "the internet", and they said well there you go.
I asked if I could send it to them to put on. They said they woulld make sure it fit, but said they would take it back off to ship it, b\c it had to be removed to be installed. When I called I had not recieved the taper pins. They wanted me to wait and send them when I got them, b\c pins differed in size. Well I they came in a little later. They dont fit. I tried everyway possible. I did not hammer them in, b\c I was afraid they would not come back out, if I was to get them in. Do I grind\sand them down? Drill out the FSB holes? I am sure I would make them too big. Or let CLE put them in? Our just let a local gunsmith take care of it? / Everything else has fit. Now the only ornament piece is not going on. The only reason I am using a FSB is to be consistent with the Army SDM-r. |
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Quoted:
Quoted:
I am no expert on AR-15's (or many other things,) but I have been in a lot of manufacturing facilities, and it is that experience which really prompted my original question. As you may notice, I mentioned in my OP that both barrels were Bushmasters. If I were running the manufacturing operation that attaches FSB's to barrels at BFI, it would be done in a standard process fashion using fixtures and jigs to eliminate as much variability as possible in the placement of the FSB as well as the location, drilling angle, and depth of the taper pin holes; it would very likely be computer-controlled. As a result, this process would be in control and it would be entirely possible to remove a FSB from one barrel and put it on another barrel with no drilling and no misalignment. That is fundamental to efficient (and profitable) manufacturing. It is the difference between what I do in my garage (batch operation) and real manufacturing flow, and it is absolutely essential to the concept of replaceable parts. Maybe they don't do it that way at Bushmaster, but they probably should. (It is interesting to note that one poster was able to interchange FSB's on Bushmaster barrels.) As to another poster's comment that the FSB's were never meant to be removed and replaced, it would seem to me that if that were the case, the FSB's would be welded to the barrels. That certainly would be less expensive and potentially stronger than the current method of attachment. I try to remember that all knowledge can be divided into three groups: the things that I know that I know, the things that I know that I don't know, and the things that I don't know that I don't know. The third group is the largest by several orders of magnitude. Thanks to everyone for the input and the food for thought.
When was the last time you saw a front sight on any weapon welded to a barrel (home bubba mods don't count)? I know of a few that were silver soldered but that is about it. All military weapons I can think of have been pinned, splined/keyed (M1, M14). With the M16 the FSB is strong enough. Remember it has an aluminum receiver and could be damaged with a hard enough blow by the alignment pin. Or the pin could snap off which a poster here recently did by trying to tighten a flash hider on by sitting on the entire rifle. Welding couldn't help with accuracy either if done after rifling. Maybe it would work if done before but then it might complicate any other operations for machining the barrel. That is my point exactly; I think FSB's (like almost all front sights) are made to be replaced as required and for that reason, manufacturers should (if they haven't already) standardize the location, spacing, and diameter of the taper pin holes. As to the danger to the rifling, that's not likely; a properly done weld job on the perimeter of the FSB wouldn't raise the temperature of the bore anywhere near damage level. |
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Quoted:
Quoted:
Quoted:
I am no expert on AR-15's (or many other things,) but I have been in a lot of manufacturing facilities, and it is that experience which really prompted my original question. As you may notice, I mentioned in my OP that both barrels were Bushmasters. If I were running the manufacturing operation that attaches FSB's to barrels at BFI, it would be done in a standard process fashion using fixtures and jigs to eliminate as much variability as possible in the placement of the FSB as well as the location, drilling angle, and depth of the taper pin holes; it would very likely be computer-controlled. As a result, this process would be in control and it would be entirely possible to remove a FSB from one barrel and put it on another barrel with no drilling and no misalignment. That is fundamental to efficient (and profitable) manufacturing. It is the difference between what I do in my garage (batch operation) and real manufacturing flow, and it is absolutely essential to the concept of replaceable parts. Maybe they don't do it that way at Bushmaster, but they probably should. (It is interesting to note that one poster was able to interchange FSB's on Bushmaster barrels.) As to another poster's comment that the FSB's were never meant to be removed and replaced, it would seem to me that if that were the case, the FSB's would be welded to the barrels. That certainly would be less expensive and potentially stronger than the current method of attachment. I try to remember that all knowledge can be divided into three groups: the things that I know that I know, the things that I know that I don't know, and the things that I don't know that I don't know. The third group is the largest by several orders of magnitude. Thanks to everyone for the input and the food for thought.
When was the last time you saw a front sight on any weapon welded to a barrel (home bubba mods don't count)? I know of a few that were silver soldered but that is about it. All military weapons I can think of have been pinned, splined/keyed (M1, M14). With the M16 the FSB is strong enough. Remember it has an aluminum receiver and could be damaged with a hard enough blow by the alignment pin. Or the pin could snap off which a poster here recently did by trying to tighten a flash hider on by sitting on the entire rifle. Welding couldn't help with accuracy either if done after rifling. Maybe it would work if done before but then it might complicate any other operations for machining the barrel. That is my point exactly; I think FSB's (like almost all front sights) are made to be replaced as required and for that reason, manufacturers should (if they haven't already) standardize the location, spacing, and diameter of the taper pin holes. As to the danger to the rifling, that's not likely; a properly done weld job on the perimeter of the FSB wouldn't raise the temperature of the bore anywhere near damage level. You may think and want them to be easily replaceable but the military feels differently. The manuals state the entire barrel need replacing. The only problem that occurs is in the civilian world where people want to play parts swap. Most parts replacement are not even allowed at company level so would would be swapping out the FSB? If it moves up the chain due for the damaged FSD it is easier (military doesn't worry the cost like we do) for maintenance to swap out the entire thing. They also don't use lo profile blocks, flip up sights (short of a few special units who have their own amours to do the work), swap between F and standard sights all on a whim like civilians so. So why would they need to worry about it. Remember where the AR/M16 got it's start and it wasn't for most of us to play transformer rifles with. |
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I called Compass Lake today. They said my A-2 FSB should fit the SDM profile they are doing. They seemed bewildered that I would ask such a question, and ask where I heard such of a thing. I said "the internet", and they said well there you go. I asked if I could send it to them to put on. They said they woulld make sure it fit, but said they would take it back off to ship it, b\c it had to be removed to be installed. When I called I had not recieved the taper pins. They wanted me to wait and send them when I got them, b\c pins differed in size. Well I they came in a little later. They dont fit. I tried everyway possible. I did not hammer them in, b\c I was afraid they would not come back out, if I was to get them in. Do I grind\sand them down? Drill out the FSB holes? I am sure I would make them too big. Or let CLE put them in? Our just let a local gunsmith take care of it? / Everything else has fit. Now the only ornament piece is not going on. The only reason I am using a FSB is to be consistent with the Army SDM-r. So gee, the people on the internet were wrong about the block not lining up huh? Shocker there. Send it back since you already paid them to fit it. Don't drill, grind or force anything, at least not unless you want to eat the costs of it as they won't want to touch it after you do any personal mods on it. |
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I mention the bayonet because for some reason that seems to be the big concern here for a lot of folks, and it usually comes up in the arguments against an aftermarket FSB that mounts in a manner other than with taper pins. The only reason I have bayonet lugs on my non-retro guns is because of the AWB. They wanted them banned, so of course I must have them now. The YHM folder's lug is for photos, not fighting. The slip-over flash hider on one gun makes it impossible to use a bayonet, but I have a lug... The R604 and A2 clones have lugs because they represent guns that came with lugs as M16s. The XM177E2 will not have a lug. Historical accuracy trumps political silliness. |
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