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 FSB-Gas block Swap -- task complete 
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Looking for a bit of info on swapping my old A2 FSB for a low-profile, set screw gas block?

Mostly my concerns are properly indexing the new gas block and if/how dimpling the barrel for the set screws.

I've removed the FSB once before so no need tell me how effing hard it is to get those taper pins out... I already know.

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Last edited by PW45 on Fri May 08, 2020 7:13 am, edited 1 time in total.



Wed Apr 29, 2020 8:39 pm
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How much of a do it yourself kinda guy are you? I guess I'm really asking if you're the kind of guy who's pretty handy with tools and can figure most things out, or if you tend to struggle with this stuff? Also do you own the necessary tools and a good bench vise? No offense intended, but it makes a difference in what to recommend you do.

Either way, it's important to recognize that your barrel will have two holes for those taper pins in it, and those holes usually are only ~3/4 of the way closed. That matters because using a set screw gas block can put one of the set screws right over one of the pin holes and cause an issue with alignment and retention.

The easiest thing to do is use a clamp-on type gas block, if your free-float handguard has enough clearance for it. (Presumably you'l be installing a free float handguard at the same time? Or are you wanting to retain the stock clamshell handguard?) If you're retaiing the clamshells, you'll want to stick with a pinned gas block; there are a few options for those out there but your options are more limited.


Wed Apr 29, 2020 11:43 pm
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Does your new Gas Block have a rail section on it that you intend to use? (can get hot enough to melt plastic sights, be careful)

Is the new GB an adjustable GB?

Will the new GB be hidden under the rail?

If no to the first two and yes to the third, it might be preferable to merely cut of the top end of the GB you have. No cost, AND IMO that taper pin set up is yards better than clamp on attachment YMMV.

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“A return to First Principles in a Republic is sometimes caused by simple virtues of a single man. His good example has such an influence that the good men strive to imitate him, and the wicked are ashamed to lead a life so contrary to his example. Before all else, be armed!” ~ Niccolo Machiavelli

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Thu Apr 30, 2020 5:29 am
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I'm not going free float I'm sticking with the rifle length handguard. I put a 1-6 optic on the rifle now I've got a big dumb sight post when I'm on low magnification.

So maybe clamp-on is a better option than set screw?

Or better yet just cut and refinish the existing FSB? (The first "I can do that for cheaper than a new gas block" wins)

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Thu Apr 30, 2020 7:21 am
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PW45 wrote:
I'm not going free float I'm sticking with the rifle length handguard. I put a 1-6 optic on the rifle now I've got a big dumb sight post when I'm on low magnification.

So maybe clamp-on is a better option than set screw?

Or better yet just cut and refinish the existing FSB? (The first "I can do that for cheaper than a new gas block" wins)



See above> Do you have me on "ignore"?

jukk0u wrote:
If no to the first two and yes to the third, it might be preferable to merely cut of the top end of the GB you have. No cost, AND IMO that taper pin set up is yards better than clamp on attachment YMMV.

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“Finding ‘common ground’ with the thinking of evil men is a fool’s errand” ~ Herschel Smith

"The said Constitution shall never be construed to authorize Congress to prevent the people of the United States who are peaceable citizens from keeping their own arms." ~ Samuel Adams

“A return to First Principles in a Republic is sometimes caused by simple virtues of a single man. His good example has such an influence that the good men strive to imitate him, and the wicked are ashamed to lead a life so contrary to his example. Before all else, be armed!” ~ Niccolo Machiavelli

Láodòng zhèng zhūwèi zìyóu

FJB


Last edited by jukk0u on Thu Apr 30, 2020 7:33 am, edited 2 times in total.



Thu Apr 30, 2020 7:32 am
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I cut and rounded off a pinned block that was "in the way" like your situation. I wanted to retain the mount on it for triangle handguards. A dremel is easy and it is the cheapest/fastest option of those you have mentioned, especially since you don't have to change guards that way. Become a PITA if you want to have a front post again, but that is similar with swapping to any other block too.


Thu Apr 30, 2020 7:32 am
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YHM makes a front block with a folding sight rather than a fixed post. Clamp-on versus set screw. I am looking into them for a pair of dissipator-style builds I have planned.

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Thu Apr 30, 2020 7:45 am
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jukk0u wrote:

Do you have me on "ignore"?



Oh man sorry Jim! I was reading this at the same time getting snacks for the kids and missed that part hahaha. I really should have you on ignore though.

Ok so DIY cut the FSB, I'm assuming there'll be exposed metal that needs to have some sort of coating on it?

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Thu Apr 30, 2020 7:48 am
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Birchwood Casey makes a pen that when painted on Aluminum makes a blackened finish. (Is that FSB aluminum?) Should be durable enough.

If not, maybe take the FSB off (In know the taper pins are stubborn) and have Dreadi put some magic on it?

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“Finding ‘common ground’ with the thinking of evil men is a fool’s errand” ~ Herschel Smith

"The said Constitution shall never be construed to authorize Congress to prevent the people of the United States who are peaceable citizens from keeping their own arms." ~ Samuel Adams

“A return to First Principles in a Republic is sometimes caused by simple virtues of a single man. His good example has such an influence that the good men strive to imitate him, and the wicked are ashamed to lead a life so contrary to his example. Before all else, be armed!” ~ Niccolo Machiavelli

Láodòng zhèng zhūwèi zìyóu

FJB


Thu Apr 30, 2020 8:45 am
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PW45 wrote:
I'm not going free float I'm sticking with the rifle length handguard. I put a 1-6 optic on the rifle now I've got a big dumb sight post when I'm on low magnification.

So maybe clamp-on is a better option than set screw?

Or better yet just cut and refinish the existing FSB? (The first "I can do that for cheaper than a new gas block" wins)


Nope, if you're keeping the clamshell handguards, you need to stick with a pinned gas block. Don't waste your time trying to use a set screw or clamped gas block; the spring pressure from the handguard delta ring can push it forward over time, rendering the rifle single shot. This is the kind of thing you might get away with for a while, until one day you don't.

Cutting the sight post is the easiest method and probably the best if you are able to make it look good. If you want to buy something, there are a few pinned gas blocks available. I think YHM makes one or two, and maybe DPMS.


Thu Apr 30, 2020 9:04 pm
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If you can find one around, Windham Weaponry has a railed gas block that appears to be the same footprint of a pinned FSB. Would give you a platform for a flip-up front sight if wanted.

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Z66 and I still fuck on the regular.

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Mikey is a Bossy Bottom.....


Thu Apr 30, 2020 9:08 pm
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Pvanderzee wrote:
If you can find one around, Windham Weaponry has a railed gas block that appears to be the same footprint of a pinned FSB. Would give you a platform for a flip-up front sight if wanted.


That's a good suggestion.

Something to remember on the rail-top gas blocks though - they usually sit a bit lower than a rail on a handguard. This is important to know because most flip up front sights are made for handguard rails. If mounting one on a gas block, you need a gas block height sight; they are available but a lot less common.


Thu Apr 30, 2020 11:46 pm
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Thanks for the suggestions fellas. Think I'll start by hacking the existing post off. Worst case if I fuck it up I can go to one of the other options.

Does anyone know if the Birchwood-Casey touch up pen work on high temp?

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Fri May 01, 2020 8:18 am
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oops. sorry bum steer there.

https://birchwoodcasey.com/files/datash ... %20Pen.pdf

"Conditions to avoid: Excessive heat."


wah wah wah wannnnnh.

How about Stove Coat? (Spray paint)

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“Finding ‘common ground’ with the thinking of evil men is a fool’s errand” ~ Herschel Smith

"The said Constitution shall never be construed to authorize Congress to prevent the people of the United States who are peaceable citizens from keeping their own arms." ~ Samuel Adams

“A return to First Principles in a Republic is sometimes caused by simple virtues of a single man. His good example has such an influence that the good men strive to imitate him, and the wicked are ashamed to lead a life so contrary to his example. Before all else, be armed!” ~ Niccolo Machiavelli

Láodòng zhèng zhūwèi zìyóu

FJB


Fri May 01, 2020 11:52 am
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Hahaha all good, I'll figure something out. I got suspicious when it only said good for receivers and stocks

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Fri May 01, 2020 1:58 pm
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