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Posted: 6/4/2012 4:03:30 AM EDT
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In light of this thread: http://www.ar15.com/forums/t_3_118/575498_I_give_up_____what_is_it_.html
I've been thinking. If a person had a regular M4-style carbine, and wanted to "dissipate" it, it's as simple as grinding/milling down the FSB/GB, adding your favorite rifle-length handguard, and adding another FSB via pinning? What are the hurdles to overcome? My main curiosity is what handguards will clear a milled FSB. Just brainstorming here, but I like the idea of the rifle-length sight radius. |
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i think as long as there is enough barrel thickness up front for a gas block its fine(ie not a pencil barrel) .750 or .625, you just need to shave the fsb top and botton and i think most rails and hand guards will clear it. though i rather like the 16" with mid gas and be lw profile like the one aim has from spikes thats always out of stock.
edit; also you need the handguard cap and something to retain it meaning you'd need to turn the barrel down for the new fsb. |
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Having just gone through this, I had a FSB pinned on my HBAR carbine barrel, it probably isn't that simple.
The guy who did mine had to weld a small tack on the barrel to get the .750 FSB to be snug to the barrel to allow it to fit tight in the jig and be pinned on an HBAR barrel. Prior to that I was running a regular FSB modified with set screws. It tightened up ok but I wouldn't have slung off of it or anything for fear of it moving the FSB even though it felt tight. Quoted:
i think as long as there is enough barrel thickness up front for a gas block its fine(ie not a pencil barrel) .750 or .625, you just need to shave the fsb top and botton and i think most rails and hand guards will clear it. though i rather like the 16" with mid gas and be lw profile like the one aim has from spikes thats always out of stock. edit; also you need the handguard cap and something to retain it meaning you'd need to turn the barrel down for the new fsb. |
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I've been thinking. If a person had a regular M4-style carbine, and wanted to "dissipate" it, it's as simple as grinding/milling down the FSB/GB, adding your favorite rifle-length handguard, and adding another FSB via pinning? If I already had an M4, I would cut down the existing FSB and look into rifle-length free float hand guards with an integrated or bolt-on front sight, something like this. I wouldn't go to the effort of adding a FSB. Just my 2¢, WhyTanFox |
| i think adco sells barrels already set up for what you describe, it may be easier selling off the barrel you have and buying one set up already, or call adco and see what they would charge you to do it to your existing upper. i also prefer the original fixed sights. |
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i think adco sells barrels already set up for what you describe, it may be easier selling off the barrel you have and buying one set up already, or call adco and see what they would charge you to do it to your existing upper. i also prefer the original fixed sights. +1 |
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I actually like the A frame FSB's, and don't see many reasons to forego them. I do to, and I love Dissapators (though oddly enough I keep giving mine away :-/). I just think it will be a lot more work trying to add a FSB/faux gas block to an existing barrel. |
| Even with two first cousins who are machinists? Maybe I'm underthinking this, but aligning the new FSB with the old seems a trivial task, then there's the matter of fitting it, which could be accomplished by shimming/sleeving if the FSB is larger ID than the OD of the barrel? |
| I really am not a huge fan of dissys. The first AR I personally owned was a dissy and it had its problems when dirty.... if you ran about 500 rounds through it it would turn into a single shot or if you were lucky you might get of a few rounds before the bolt failed to eject the spent casing. I have heard of mid lengths with 14.5" barrels being undergassed so only having about an inch of barrel following the gas port is not the most effective way to do things... they could possibly run a larger gas port diameter but if there is any build up it can affect how much gas gets back to the bolt. |
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I would be keeping the carbine length gas system in my utterly reliable gun. Nothing would change except the sight radius and handguard length. yea... it won't change much going to the "dissy" setup in that case. You will get a little more accuracy with that longer sight radius for sure. It will add some weight up front which will make it a little less stable shooting unsupported so it probably is about the same in the end but you will definitely get more precision out of your irons supported or from the bench with it being the same exact rifle with the exception of that one variable. |
Sweet. Time to get some calipers on the barrel and shop for a front sight block, and start shopping the EE for a rifle length OD MOE
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Armalite sells a clamp on FSB that can be adjusted for windbags giving you a perfect mechanical zero. I was initially skeptical about it rotating but that has not been the case. I assume you meant windage and not windbags. Yes, the Armalite clamp on is the easiest to use. I used on on a M4 style barrel and it clamped on tight and never moved. |
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I really am not a huge fan of dissys. The first AR I personally owned was a dissy and it had its problems when dirty.... if you ran about 500 rounds through it it would turn into a single shot or if you were lucky you might get of a few rounds before the bolt failed to eject the spent casing. I have heard of mid lengths with 14.5" barrels being undergassed so only having about an inch of barrel following the gas port is not the most effective way to do things... they could possibly run a larger gas port diameter but if there is any build up it can affect how much gas gets back to the bolt. Sounds like you had the 16" with rifle length gas Dissy set up. Those can be problematic. Almost all modern Dissapators use carbine or mid length gas systems. My middy Dissapator cycles anything I put though it, dirty or clean. |
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I really am not a huge fan of dissys. The first AR I personally owned was a dissy and it had its problems when dirty.... if you ran about 500 rounds through it it would turn into a single shot or if you were lucky you might get of a few rounds before the bolt failed to eject the spent casing. I have heard of mid lengths with 14.5" barrels being undergassed so only having about an inch of barrel following the gas port is not the most effective way to do things... they could possibly run a larger gas port diameter but if there is any build up it can affect how much gas gets back to the bolt. Sounds like you had the 16" with rifle length gas Dissy set up. Those can be problematic. Almost all modern Dissapators use carbine or mid length gas systems. My middy Dissapator cycles anything I put though it, dirty or clean. Yea... it was the rifle length and it was problematic. I kept it less than 2 months. gave it away... that rifle pissed me off |
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I would just cut front site post down, then add a free float rail and put a flip up sight at the end. Done!
No having to add another front sight post onto the barrel. Just my opinion on the matter, unless you really want to have the front sight post on there. With the free float method you get a free floated barrel while also getting a longer sight distance and the option to flip the front sight down should you ever add an optic.....it just makes more sense in my head to d it this way. |
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I would just cut front site post down, then add a free float rail and put a flip up sight at the end. Done! No having to add another front sight post onto the barrel. Just my opinion on the matter, unless you really want to have the front sight post on there. With the free float method you get a free floated barrel while also getting a longer sight distance and the option to flip the front sight down should you ever add an optic.....it just makes more sense in my head to d it this way. Kind of exactly like what finslayer83 did here |
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I would just cut front site post down, then add a free float rail and put a flip up sight at the end. Done! No having to add another front sight post onto the barrel. Just my opinion on the matter, unless you really want to have the front sight post on there. With the free float method you get a free floated barrel while also getting a longer sight distance and the option to flip the front sight down should you ever add an optic.....it just makes more sense in my head to d it this way. Kind of exactly like what finslayer83 did here Yup, just like that. Couldn't be any easier. Hardest part is cutting front post down, but it's really not that hard. |
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I've had two. Both of them were undissipated. I love them, but I'm a balance nazi and have always had a disgust for the AR15 FSB. Ghost ring rear sights blow with bladed fronts compared to hooded front sights, and they obstruct the sight picture too much with optics. JMO.
Maybe I'll give it a try again someday with a pencil barrel. |
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I would just cut front site post down, then add a free float rail and put a flip up sight at the end. Done! No having to add another front sight post onto the barrel. Just my opinion on the matter, unless you really want to have the front sight post on there. With the free float method you get a free floated barrel while also getting a longer sight distance and the option to flip the front sight down should you ever add an optic.....it just makes more sense in my head to d it this way. Kind of exactly like what finslayer83 did here Yup, just like that. Couldn't be any easier. Hardest part is cutting front post down, but it's really not that hard. That'll be the route I take at some point if I'm looking to tweak my rifle after if figure out optics and lots of other things. |
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I would just cut front site post down, then add a free float rail and put a flip up sight at the end. Done! No having to add another front sight post onto the barrel. Just my opinion on the matter, unless you really want to have the front sight post on there. With the free float method you get a free floated barrel while also getting a longer sight distance and the option to flip the front sight down should you ever add an optic.....it just makes more sense in my head to d it this way. Kind of exactly like what finslayer83 did here Yup, just like that. Couldn't be any easier. Hardest part is cutting front post down, but it's really not that hard. That'll be the route I take at some point if I'm looking to tweak my rifle after if figure out optics and lots of other things. Same here. My next build will be a free float carbine system, but most would call that a Recce, not a dissipator...even though they are very similar. My G/F has a 16" Dissy and it is awesome. She gets so many looks at the gun range from people......"what is that?", "I've never seen anything like that before". They are shocked when a female knows more about AR's then they do.....I just sit back and smile. |
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Armalite sells a clamp on FSB that can be adjusted for windbags giving you a perfect mechanical zero. I was initially skeptical about it rotating but that has not been the case. I assume you meant windage and not windbags. Yes, the Armalite clamp on is the easiest to use. I used on on a M4 style barrel and it clamped on tight and never moved. I blame autocorrect 
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I would just cut front site post down, then add a free float rail and put a flip up sight at the end. Done! No having to add another front sight post onto the barrel. Just my opinion on the matter, unless you really want to have the front sight post on there. With the free float method you get a free floated barrel while also getting a longer sight distance and the option to flip the front sight down should you ever add an optic.....it just makes more sense in my head to d it this way. Kind of exactly like what finslayer83 did here Yup, just like that. Couldn't be any easier. Hardest part is cutting front post down, but it's really not that hard. That'll be the route I take at some point if I'm looking to tweak my rifle after if figure out optics and lots of other things. Apparently I'm the only one that feels this way, but the idea of free floating a handguard (so that WHEN it flexes, the barrel does not flex with it) then mounting the front sight on the FF handguard (which BY DESIGN moves independently of the barrel) seems like a good way to guarantee that the POI will be constantly shifting relative to the front sight. Joe |
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I would just cut front site post down, then add a free float rail and put a flip up sight at the end. Done! No having to add another front sight post onto the barrel. Just my opinion on the matter, unless you really want to have the front sight post on there. With the free float method you get a free floated barrel while also getting a longer sight distance and the option to flip the front sight down should you ever add an optic.....it just makes more sense in my head to d it this way. Kind of exactly like what finslayer83 did here Yup, just like that. Couldn't be any easier. Hardest part is cutting front post down, but it's really not that hard. That'll be the route I take at some point if I'm looking to tweak my rifle after if figure out optics and lots of other things. Apparently I'm the only one that feels this way, but the idea of free floating a handguard (so that WHEN it flexes, the barrel does not flex with it) then mounting the front sight on the FF handguard (which BY DESIGN moves independently of the barrel) seems like a good way to guarantee that the POI will be constantly shifting relative to the front sight. Joe Then why do people say if you free float a barrel it can become more accurate? I get what your saying, but I really don't think it is the case. Have you shot w/ a set up like this? I have and the POI is fine. |
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Free floating a barrel prevents the barrel from flexing with the handguard as a result of the shooter gripping the rifle (or supporting it with a bipod or bench rest).
An optic secured to the upper receiver is unaffected by the movement of the handguard as well, so excluding the influence of gravity or momentum on the barrel, the POI should never move relative to the receiver rail mounted sight on a FFed barrel For BUIS I can see the point of mounting the frotn sight on a FF HG, but for the primary (or only) sighting device, it's less than optimal IMHO. Joe |
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Free floating a barrel prevents the barrel from flexing with the handguard as a result of the shooter gripping the rifle (or supporting it with a bipod or bench rest). An optic secured to the upper receiver is unaffected by the movement of the handguard as well, so excluding the influence of gravity or momentum on the barrel, the POI should never move relative to the receiver rail mounted sight on a FFed barrel For BUIS I can see the point of mounting the frotn sight on a FF HG, but for the primary (or only) sighting device, it's less than optimal IMHO. Joe I got you......I guess I feel differnt as my irons are like you said...back up, and not my primary sighting device. |
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Free floating a barrel prevents the barrel from flexing with the handguard as a result of the shooter gripping the rifle (or supporting it with a bipod or bench rest). An optic secured to the upper receiver is unaffected by the movement of the handguard as well, so excluding the influence of gravity or momentum on the barrel, the POI should never move relative to the receiver rail mounted sight on a FFed barrel For BUIS I can see the point of mounting the frotn sight on a FF HG, but for the primary (or only) sighting device, it's less than optimal IMHO. Joe Very interesting points you bring up. I wonder if anyone has done an accuracy test on this like using a clamp on FSB, then removing it and using a BUIS on the rail and shooting groups with both methods. Sounds like someone should. |
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Free floating a barrel prevents the barrel from flexing with the handguard as a result of the shooter gripping the rifle (or supporting it with a bipod or bench rest). An optic secured to the upper receiver is unaffected by the movement of the handguard as well, so excluding the influence of gravity or momentum on the barrel, the POI should never move relative to the receiver rail mounted sight on a FFed barrel For BUIS I can see the point of mounting the frotn sight on a FF HG, but for the primary (or only) sighting device, it's less than optimal IMHO. Joe Very interesting points you bring up. I wonder if anyone has done an accuracy test on this like using a clamp on FSB, then removing it and using a BUIS on the rail and shooting groups with both methods. Sounds like someone should. I know AMUshooter10 did a that had something to do with POA and POI w/ different types of holds. Search won't let me look for threads by author. |
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Here is the thread I was talking about...pretty interesting.
http://www.ar15.com/archive/topic.html?b=3&f=118&t=556278 |
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The main appeal for the dissy is the longer sight radius and more handguard. The plus to the fixed front sight is that it is more durable than a folding, rail mounted front sight. The dissy is a rifleman's carbine. I have dedicated Dissy set up with a free float rail, an optic, and KAC 200-600m rear sight. Aimpoint is zero'd at 50yrds. KAC is zero'd as recommended by KAC.
So I have a rifle that can do up close work or reach farther out. 
As for the free float with rail mounted sight, it's only a Recce if it is using a magnified scope. 
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Free floating a barrel prevents the barrel from flexing with the handguard as a result of the shooter gripping the rifle (or supporting it with a bipod or bench rest). An optic secured to the upper receiver is unaffected by the movement of the handguard as well, so excluding the influence of gravity or momentum on the barrel, the POI should never move relative to the receiver rail mounted sight on a FFed barrel For BUIS I can see the point of mounting the frotn sight on a FF HG, but for the primary (or only) sighting device, it's less than optimal IMHO. Joe Very interesting points you bring up. I wonder if anyone has done an accuracy test on this like using a clamp on FSB, then removing it and using a BUIS on the rail and shooting groups with both methods. Sounds like someone should. I think it could be pretty easily demonstrated without firing a shot. Use a laser bore sighter and zero the FF rail mounted BUIS on a wall 30 feet away (I mean zero, as in 6 oclock sight picture, laser dot on the post) then compare the sight picture with different grips on the HG, maybe a bipod, and with a sling. See if the laser dot moves off the front sight post. I suspect that even with bare hands one could flex the FF HG enough to move the front post off "zero". Now if the shooter always maintained the same grip on the HG, it would flex the same every time, and provided it was sighted in with the same grip, it would hold zero. In a bad situation, though, the shooter may not be able to use that same grip. At short distances the POI shift would be negligible, probably. Hell, I'm not even that good with irons... I can get 80% of my shots on a 6" target at 100 yards at best, but my eyesight isn't what it used to be, either. Joe |
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Here is the thread I was talking about...pretty interesting. http://www.ar15.com/archive/topic.html?b=3&f=118&t=556278 Thanks for the link, interesting how far off the POI can be. |
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Armalite sells a clamp on FSB. So does JP but it is $.
You may need to shim it slightly if your barrel has a step to aid in starting your gas block/fsb. 
If you are seeking accuracy with irons, consider a thinned front sight post. I need to take a picture of it, bit I took a KNS aperture sight, pulled out the too-thick crosshairs, and soldered in a SKINNY front post. That was after experimenting with this: 
It worked but a skinny post works better. I'll take some pics tonight. |
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I would be keeping the carbine length gas system in my utterly reliable gun. Nothing would change except the sight radius and handguard length. yea... it won't change much going to the "dissy" setup in that case. You will get a little more accuracy with that longer sight radius for sure. It will add some weight up front which will make it a little less stable shooting unsupported so it probably is about the same in the end but you will definitely get more precision out of your irons supported or from the bench with it being the same exact rifle with the exception of that one variable. I find a heavier rifle to be a little less 'nervous' when shooting offhand. I think it is an accuracy aid. |
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I would be keeping the carbine length gas system in my utterly reliable gun. Nothing would change except the sight radius and handguard length. yea... it won't change much going to the "dissy" setup in that case. You will get a little more accuracy with that longer sight radius for sure. It will add some weight up front which will make it a little less stable shooting unsupported so it probably is about the same in the end but you will definitely get more precision out of your irons supported or from the bench with it being the same exact rifle with the exception of that one variable. I find a heavier rifle to be a little less 'nervous' when shooting offhand. I think it is an accuracy aid. The weight is both a hendrance and a help. My dissy upper on a buddy's FA lower. Video of shoot (I suck at embedding) |
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