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9/22/2017 12:11:25 AM
Posted: 9/3/2010 12:02:42 AM EDT
I am finally getting a little tired of the ever so slight "ghosting" I see when using optics on my favorite flat top carbine. It has never bothered me during Aimpoint / Eotech use. Rear BUI, front tower, and red dot sights co-witnessed.

It all started bothering me with the TA31F at longer shooting distances. I built the gun as light as I could at the time using an aluminum front rail system. My first instinct was to just cut / mill the front sight tower off. Problem fixed I remember seeing this all the time "back in the day" of the first flat tops

My carbine has a lightweight 14.5" "pencil" profile barrel with a .625 diameter at the gas block, 1/7 twist, Vortex on the end. I have looked and looked for something that:

1. Will fit a .625
2. Is light weight.
3. Must have a bayonet lug
4. I don't need or want any extra rails - except maybe a top one that matches the height of my DD 7.0 Omega rail (to mount forward BUI). I am not sure if the inch or so more the BUI would sit forward would be of any great advantage.

So...damn the torpedoes and "hack it off" , or is there a better...more civilized way to go about this keeping the above #'s 1-4 in mind?

Link Posted: 9/3/2010 12:18:18 AM EDT
I think a cut-down FSB without being covered by a rail is ugly and dumb looking. That said, it's your gun, and you should do what you want. There's nothing functionally wrong with it.
Link Posted: 9/3/2010 12:38:34 AM EDT
Cut FSBs are some of the absolute best "gas blocks." Seeing AR fads go full circle is something I'm finding more and more funny though.

Saw a thread recently where a person removed the FSB, installed a rail and gas block... and then pinned the gas block?
Link Posted: 9/3/2010 1:11:04 AM EDT
[Last Edit: 9/3/2010 1:16:02 AM EDT by MJL]
If you're planning on leaving the bayonet lug on there, and you might actually attach something to it, then I would just cut down the original front sight tower. It's pinned so it is going to be a bit more solid than a clamp or set-screw gas block, and it already has the lug you want. Plus, there are fewer gas block options out there for .625 barrels anyway.
You can buy lower profile gas blocks with and lugs, but they are usually clamp-on and personally, I don't think that's good enough to withstand any forces that might be exerted against a bayo lug that actually has a bayonet attached to it. If you're gonna have it then it might as well be reliable.
If you take your time you can make it look decent. A cut down sight tower will probably be a little lighter than a lot of other blocks too.
Link Posted: 9/3/2010 1:20:35 AM EDT
Run magnification and the ghosting goes away.

Like already mentioned, it's your gun do as you please. I run fold down sights with a rail for my optics on one of my Ar15s. It works, but it's heavier.

My fighting carbine has an Eotech with the front fixed sight. Mine ghosts too, but I like the lightness. The sight post protects the Eotech sight too, if you bump into something....
Link Posted: 9/3/2010 3:16:51 AM EDT
old school if it's done well....ghetto crap if it's not.
Link Posted: 9/3/2010 4:19:33 AM EDT
I have a Colt 6720 (flattop, 16" lightweight carbine). I am getting ready to have ADCO shave the FSB and install a LaRue 10" rail that will completely cover the cut down FSB and then some (a 9" will cover it on a carbine). I don't think I would like an exposed cut down FSB.
Link Posted: 9/3/2010 4:40:11 AM EDT
cut it
Link Posted: 9/3/2010 5:38:17 AM EDT
I recall seeing a thread somewhere on how-to-do-it. The final result was great; it looked like a factory made gas block.
Link Posted: 9/3/2010 5:51:09 AM EDT
Wanna borrow my hacksaw? Whack it! This will also allow you to install a cool tube that will cover the chopped sight (but you may have to also grind off the bayo lug to do this). OTOH, like the man said, with a 4x32 you really don't notice the front sight although it is 'there'. And, if you carry a carry handle on you, you have a way of staying in the fight if something happens to the optical sight.
Link Posted: 9/3/2010 5:53:21 AM EDT
I run a YHM Diamond and a TRX Extreme and I chopped the FSB for both of those. They're under the rail, so what's the big deal? . Hit it with some Rustoleum high temp paint and it's good to go. $35 to cut a FSB is rape and I'm too cheap to spend $25 up to $100+ for a new gas block that's gonna be held on with set screws. I also found it easier to install the FSB and gas tube and then tape off the barrel and paint it. There's a lot less scratching on it if you do it that way.
Link Posted: 9/3/2010 6:03:55 AM EDT
Why pay 40, for something you can have for free?

The CD FSB is the way to go.
Link Posted: 9/3/2010 11:49:33 AM EDT
Originally Posted By MJL:
If you're planning on leaving the bayonet lug on there, and you might actually attach something to it, then I would just cut down the original front sight tower. It's pinned so it is going to be a bit more solid than a clamp or set-screw gas block, and it already has the lug you want. Plus, there are fewer gas block options out there for .625 barrels anyway.
You can buy lower profile gas blocks with and lugs, but they are usually clamp-on and personally, I don't think that's good enough to withstand any forces that might be exerted against a bayo lug that actually has a bayonet attached to it. If you're gonna have it then it might as well be reliable.
If you take your time you can make it look decent. A cut down sight tower will probably be a little lighter than a lot of other blocks too.


I am sold!!!! I am going to get out my WW1 field surgery kit and remove it tonight!

Thanks for everyones opinions!


Link Posted: 9/3/2010 12:20:25 PM EDT
What the hell do you need a bayonet lug for anyway?? That's simply a throw back to WWII. I spent 20+ years in the military. Been in combat in Iraq and many other not so nice places over the years. I've never been issued a bayonet ........ ever. The only place I've ever seen a bayonet is in a surplus store. I've never even seen a person with an issued bayonet. Everyone I knew had to buy thier own knife ..... none of which you could put on your weapon. I think civilians that "Must Have" a bayonet lug on thier rifle are just rediculous. If you are a collector of older weapons and you want one to be a perfect specimen. Then yes, I can see the need for the bayonet lug.
Link Posted: 9/3/2010 12:23:01 PM EDT
If done properly it will look great.
I have done a few for friends and they really like the way they turn out.
Just cut the top off with a hacksaw and grind it down until it looks good.
Link Posted: 9/3/2010 12:35:16 PM EDT
I feel it is the way to go with a dedicated magnified optic rifle. I've worked on too many guns that the reason they were having cycling problems was due to an aftermarket gas block.

You know your FSB works, and attachment via taper pins is the most sturdy way available.

If done properly and refinished properly it comes out looking good too...



- AG
Link Posted: 9/3/2010 12:42:48 PM EDT
Yep, these really look ghetto!!! Cutting down a stock FSB is often a simple solution to a basic need.



Link Posted: 9/3/2010 4:55:52 PM EDT
Originally Posted By Aggie_Gunner:
I feel it is the way to go with a dedicated magnified optic rifle. I've worked on too many guns that the reason they were having cycling problems was due to an aftermarket gas block.

You know your FSB works, and attachment via taper pins is the most sturdy way available.

If done properly and refinished properly it comes out looking good too...

http://img.photobucket.com/albums/v668/dp_holland/HGW002b.jpg

- AG


Nice work! Thank you for the ideas!

Link Posted: 9/3/2010 5:14:30 PM EDT
It's not ghetto if done right like the ones posted. They work and they are secure.

However, I don't like doing it for a couple of reasons. A pinned FSB is specific to the barrel. Once you modify it you can't go back if you ever change your mind. Also, it takes time to do, which isn't much, but if you do screw it up, you are stuck with buying a gas block anyway. For $50 a decent low profile gas block is easier and for most purposes plenty secure. So, my choice is to buy the gas block and retain the FSB for use on that barrel at a later date should I change my mind or decide to sell it.

I'm not disagreeing with anything or saying they aren't a good option. After doing it once and regretting it, it's just my preference not to do it - anymore. In fact, now if I buy a barrel that has a GB or FSB option at close to the same price, I'll go with the FSB, remove it and put on a gas block if I need to cover it with rails.
Link Posted: 9/3/2010 6:17:25 PM EDT
[Last Edit: 9/3/2010 6:34:26 PM EDT by ThompsonCrazy]
What does the Mk18 Mod I run? I think they are KAC low pro...... Does that secure with a set screw? If so I guess the barrel can be dimpled but you would still be relying on loctite to keep the set screw/screws secure?

TC
Link Posted: 9/3/2010 6:37:39 PM EDT
I cut mine off with a hacksaw and then rounded off with a dremel add a little gun bluing or brownells makes a stick and it looks fine uncovered but i did cover mine which were my intentions from the start.
Link Posted: 9/3/2010 6:42:47 PM EDT
I dont worry about looks, function is most important.
Link Posted: 9/3/2010 7:57:37 PM EDT
Originally Posted By Eazy_E:
$35 to cut a FSB is rape


Please!!! Some people do not have the tools or the talent to take on such a task. I am more than willing to spend a "whopping" $35 to let a professional with better tools and talent than me do the job right so I don't screw it up. Adco's prices are really quite reasonable when compared to the quality of the work.

Originally Posted By Eazy_E:
I'm too cheap


You said it!
Link Posted: 9/3/2010 8:18:09 PM EDT
A buddy at work and I cut my front site gas block on my 6920, I did most of the cutting and to be quite honest it looked like A$$ really but i got it done and It was not that hard. but my buddy did the finishing of it, and turned my hackjob into something that looked very clean and nieat, it can be done just a matter of what you want it for or out of it. I wanted it to fit under a rail so I could run back up front and rear sights, plus I pretty sure colt had the right idea with the pinned gas block to start with, so why reinvent the wheel,just me personal observation
Link Posted: 9/3/2010 11:45:34 PM EDT
[Last Edit: 9/3/2010 11:46:11 PM EDT by superchi]
Originally Posted By tacman556:
Originally Posted By Eazy_E:
$35 to cut a FSB is rape


Please!!! Some people do not have the tools or the talent to take on such a task. I am more than willing to spend a "whopping" $35 to let a professional with better tools and talent than me do the job right so I don't screw it up. Adco's prices are really quite reasonable when compared to the quality of the work.



A rotary tool and about 10-15 minutes of your time, it's not rocket science. You can use that $35 to buy the rotary tool and it'd be much more useful than being too afraid to chop your gas block and paying a "professional" gas block chopper
Link Posted: 9/4/2010 12:28:01 AM EDT
DYI chop job using a $25 dremel from craigslist. It really wasn't that hard to do, just take your time and protect the areas you dont want to cut with masking tape. I wouldn't call it a 10-15 min job if you want it to look nice, but its pretty quick. You'll be surprised how handy having a dremel tool around the house will be.

Link Posted: 9/4/2010 1:25:56 AM EDT
i would cut and refinish it, then get a rail long enough to cover it, or longer. Vtac extreme or trx extreme (same thing, one is slots, one is holes) are very light. gives you more room for hands/accessories also.
Link Posted: 9/4/2010 9:22:08 PM EDT
Link Posted: 9/4/2010 9:39:30 PM EDT
A cut front sight gas block is the best way to go for a low pro gas block if the barrel it came from is from the factory. This way you are the not messing with the original gas system that came from the factory therefore being the most reliable and best way to go.
Link Posted: 9/4/2010 10:55:18 PM EDT
Originally Posted By Unicorn:
I agree with doing it yourself instead of paying me to do it. I really don't like doing them as they are kind of a pain sometimes. You'll go through about 3 cutting wheels and easily dull a less than top tier blade cutting one down. Even with a bench grinder it takes time to do a neat job. About say, $35 or so just for the time involved. It's kind of like paying to have your oil changed or doing it yourself. You are paying for the time involved in having it done. Not necessarily the quality of work or the cost of tools. Just the convenience of not spending that time yourself. But it's not extremely difficult if you have the patience and some Dremel mastery skill. Cut then grind and/or file until it's where you want it. Finish with a good high temp paint instead of just Krylon. I like the high temp exhaust paint that can handle over 1,000 degrees. Solvent and heat resistant.
The coolest thing IMO about doing it yourself, is that well, you did it yourself. It makes it yours. A small thing, but still something. I say go for it. Hell, if you screw it up or decide to change later on, and you have to buy one anyway, what are you out? Some time and experience gained.


I think this unicorn guy may have a very good point
Link Posted: 9/5/2010 12:00:35 AM EDT
Link Posted: 9/5/2010 4:29:59 AM EDT
So does no one make a low profile gas block that uses the original pin holes?
Link Posted: 9/5/2010 5:39:26 AM EDT

Originally Posted By UH_SALT_RIFLE:
So does no one make a low profile gas block that uses the original pin holes?

The pin holes have to be individually drilled by a gunsmith, so no two are totally the same. That's why if you look on BCM, or any other parts dealer, they never sell them pre-drilled. A pinned gas block/FSB is pretty much unique to whatever rifle it came on.
Link Posted: 9/5/2010 6:50:49 AM EDT
Originally Posted By Eazy_E:

Originally Posted By UH_SALT_RIFLE:
So does no one make a low profile gas block that uses the original pin holes?

The pin holes have to be individually drilled by a gunsmith, so no two are totally the same. That's why if you look on BCM, or any other parts dealer, they never sell them pre-drilled. A pinned gas block/FSB is pretty much unique to whatever rifle it came on.


Looks like it's time to break out the old cutoff wheel!
Link Posted: 9/5/2010 7:26:56 AM EDT
Originally Posted By Gregory_K:
Why pay 40, for something you can have for free?

The CD FSB is the way to go.


I say this. Fancy low profile gas blocks are for guys that want a pretty gun. A cut down front sight base will function the same.
Link Posted: 9/5/2010 7:49:46 AM EDT

Originally Posted By UH_SALT_RIFLE:
Originally Posted By Eazy_E:

Originally Posted By UH_SALT_RIFLE:
So does no one make a low profile gas block that uses the original pin holes?

The pin holes have to be individually drilled by a gunsmith, so no two are totally the same. That's why if you look on BCM, or any other parts dealer, they never sell them pre-drilled. A pinned gas block/FSB is pretty much unique to whatever rifle it came on.


Looks like it's time to break out the old cutoff wheel!

I've done two. It's really no big deal to cut one. I used a hacksaw because I don't have a Demel, and I'd recommend going that route. Just go slow. I spend most of my time really getting the profile down with a bench grinder. Again, go slow. It's easy to take too much off. I used Rustoleum high temp paint when I was done. It's a lot easier to replace the gas tube, and pin the gas block in place and then tape the barrel and gas tube and paint it. I had to do that anyway to touch up my first one, so why not cut out the middleman and just paint it once it's already in place. I guess giving it a good shooting after it's painted helps to cure the paint too, but mine are both totally under the rails, so that doesn't matter too much.
Link Posted: 9/5/2010 4:36:55 PM EDT
Originally Posted By Eazy_E:

Originally Posted By UH_SALT_RIFLE:
Originally Posted By Eazy_E:

Originally Posted By UH_SALT_RIFLE:
So does no one make a low profile gas block that uses the original pin holes?

The pin holes have to be individually drilled by a gunsmith, so no two are totally the same. That's why if you look on BCM, or any other parts dealer, they never sell them pre-drilled. A pinned gas block/FSB is pretty much unique to whatever rifle it came on.


Looks like it's time to break out the old cutoff wheel!

I've done two. It's really no big deal to cut one. I used a hacksaw because I don't have a Demel, and I'd recommend going that route. Just go slow. I spend most of my time really getting the profile down with a bench grinder. Again, go slow. It's easy to take too much off. I used Rustoleum high temp paint when I was done. It's a lot easier to replace the gas tube, and pin the gas block in place and then tape the barrel and gas tube and paint it. I had to do that anyway to touch up my first one, so why not cut out the middleman and just paint it once it's already in place. I guess giving it a good shooting after it's painted helps to cure the paint too, but mine are both totally under the rails, so that doesn't matter too much.


Who am I to question the word of an OG wit two gats dog?
Link Posted: 9/5/2010 4:55:50 PM EDT
Originally Posted By drifter_r6:
DYI chop job using a $25 dremel from craigslist. It really wasn't that hard to do, just take your time and protect the areas you dont want to cut with masking tape. I wouldn't call it a 10-15 min job if you want it to look nice, but its pretty quick. You'll be surprised how handy having a dremel tool around the house will be.

http://i904.photobucket.com/albums/ac248/drifter_r6/IMG_2315s.jpg?t=1283588511




THIS! Really cool.

Link Posted: 9/5/2010 5:46:57 PM EDT
[Last Edit: 9/5/2010 5:49:15 PM EDT by comp1911]
Originally Posted By Sub-MOA:
Cut FSBs are some of the absolute best "gas blocks." Seeing AR fads go full circle is something I'm finding more and more funny though.

Saw a thread recently where a person removed the FSB, installed a rail and gas block... and then pinned the gas block?


If you ever want to go back to a FSB this is a good idea. It's also a lot less dicking around pinning a gasblock then chopping up a FSB. At least for me it is. The only negative is the cost of the gasblock.
Link Posted: 9/5/2010 6:44:31 PM EDT
Originally Posted By CLICKBANGBANG:
Originally Posted By Gregory_K:
Why pay 40, for something you can have for free?

The CD FSB is the way to go.


I say this. Fancy low profile gas blocks are for guys that want a pretty gun. A cut down front sight base will function the same.


Not everyone buys a gun whole.. why buy a FSB and cut it down when you can buy a low profile gas block to begin with?
Link Posted: 9/5/2010 9:18:43 PM EDT
I say old school if done right.......ghetto would be turning your gun on its side when firing....."kill shot"-Date Night
Link Posted: 9/7/2010 8:45:55 PM EDT
Poor men have poor ways. I am going to cut a Co-worker FSB after deer season.

Stone
Link Posted: 9/8/2010 2:19:05 AM EDT
[Last Edit: 9/8/2010 2:23:06 AM EDT by Colt808]
It's an old school modification and not hard to do right. I consider those who do it ingenious, self-reliant, handy, creative, resourceful etc. Why spend the money on an upgrade for something you can do yourself? I've done on 2 of my own AR's and a couple of my buddies. I'll admit I can be a cheap bastard at times, but my choice to do this has nothing to do with that. I think it's obvious from some of the example that there's nothing ghetto about it.

Tips/how I do it: Remove the FSB if you can...it can be done while attached to the barrel, but it's just easier to take it off. Rough cut about 1/8-1/4" higher than where you want to be when finished. It doesn't matter if you use a hacksaw, dremel, or cutoff wheel, just leave yourself a little extra to work with. Use a file to shape and cut it down further. Complete with some fine sand paper and refinish.

It's really that easy. Just have an idea of what you want and take your time. My first attempt took about 45 minutes. If you put in the effort, the last thing you'll want to do is cover it up. Show it off with pride.
Link Posted: 9/10/2010 5:08:00 PM EDT
Well I took the plunge (or the cut) and it was easy and came out great. Getting those stupid pins out of the FSB was harder than anything in my case.

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