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Posted: 3/22/2026 5:24:44 PM EDT
[Last Edit: SC_Tiger][Edited]
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Hi all. New to the forum. I have a home built AR in 5.56 that I want to replace the gas block on. Currently it has the ‘A frame’ gas block with the front sight, pinned with two pins. I want to put a low profile gas block on it so I can mount a low power scope on the rifle. I have a few questions: Is there a party brand of gas block I should get or one I should stay away from? Barrel OD is .750”. Are the ones retained with a set screw any good? Seems like a potential failure point but installation would be easier. Any tools I should invest in? Already figuring on the front sight removal block. I have some punches but not sure I have the exact one I will need. Anything else I should know? Rifle is a hodgepodge. 16” Bushmaster chrome lined barrel (what can I say - dad is a Vietnam vet), DPMS upper (bought all that assembled and the bolt already headspaced), poverty pony lower with Palmetto State Armory internals. Carbine gas system. Direct impingement - not a piston drive. Works pretty well. Shoots better than I do (that ain’t saying much though). Thanks in advance. I used to be on Glocktalk and The Bore Site so maybe some of you were over there too. Same user name. |
Shaving the front sight tower would be the the easiest course of action. But yes, swapping to a low profile gas block is pretty straightforward. Hammer the pins out, remove the front sight tower, and replace with gas block of your choice. Set screw options, when installed correctly , work fine. Everybody has their pet brands. SLR, Daniel Defense, and Yankee Hill Machine are my preferred. |
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Originally Posted By TGWLDR: Shaving the front sight tower would be the the easiest course of action. https://i.postimg.cc/rsfC5yRq/images.jpg But yes, swapping to a low profile gas block is pretty straightforward. Hammer the pins out, remove the front sight tower, and replace with gas block of your choice. Set screw options, when installed correctly , work fine. Everybody has their pet brands. SLR, Daniel Defense, and Yankee Hill Machine are my preferred. FPNI. |
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Originally Posted By TGWLDR: Shaving the front sight tower would be the the easiest course of action. https://i.postimg.cc/rsfC5yRq/images.jpg But yes, swapping to a low profile gas block is pretty straightforward. Hammer the pins out, remove the front sight tower, and replace with gas block of your choice. Set screw options, when installed correctly , work fine. Everybody has their pet brands. SLR, Daniel Defense, and Yankee Hill Machine are my preferred. +1 for shaving existing block. I cut off the sight tower with a hacksaw and cleaned it up with a Dremel and stove paint. I've also used set screw blocks. A dimple can be drilled in the barrel to help lock in the set screw position. |
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Originally Posted By TGWLDR: Shaving the front sight tower would be the the easiest course of action. https://i.postimg.cc/rsfC5yRq/images.jpg But yes, swapping to a low profile gas block is pretty straightforward. Hammer the pins out, remove the front sight tower, and replace with gas block of your choice. Set screw options, when installed correctly , work fine. Everybody has their pet brands. SLR, Daniel Defense, and Yankee Hill Machine are my preferred. You know I thought about that. But it thought it would be the ‘hack’ way to do it. That said - the one in your picture is done quite well. Very nice. Thanks. |
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Originally Posted By SC_Tiger: You know I thought about that. But it thought it would be the ‘hack’ way to do it. That said - the one in your picture is done quite well. Very nice. Thanks. Many do, and have done, the same mod. It works very well, retains the double taper pin retainer method, no added cost, and minimally time consuming. I wouldn't consider it a "hack" approach personally. |
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| Only thing to add is to make sure you drive out the pins, actually taper pins, in the correct direction. I have done this so seldom that I cannot recall offhand which way, but the simple and fool proof method is to measure each end of the taper pin. Then drive it out from small end toward the large end. Install in reverse, from the large side to the small side, so when you take the measurements, don't try to remember which way, write it down so you don't screw up when putting it back together. When driving out the pins, sometimes they can be a bitch so rest the sight tower against a solid object, like hard wood, and use a big hammer and properly fitting punch. Do not try to "tap" them out. Give them a good hard whack and they should come right out. At least that's been my experience with the few sight towers I have removed. I much prefer the set screw type gas blocks then tork it well and blue Lock-Tite it and they do not come loose. I've never had one come loose yet and that has been on a lot of rifles and calibers. Dimpling is nice but not needed if you do it right. Also, if you set screw it, I like the tooth type set screw that really bites into the barrel steel like this. |
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Question on shaving the gas block - if I do that will I be able to get the barrel but over it or will I still have to remove it? If I remove it will I need to replace the pins to put it back on or are they reusable? I plan to install a free floating hand guard and all options I’ve seen require me to replace the barrel nut. Just trying to think through this before I do it. |
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Originally Posted By TGWLDR: Many do, and have done, the same mod. It works very well, retains the double taper pin retainer method, no added cost, and minimally time consuming. I wouldn't consider it a "hack" approach personally. I’m not hating on it at all. I’m kinda new to this level of work on the AR. I think it’s a great idea. |
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Originally Posted By SC_Tiger: Question on shaving the gas block - if I do that will I be able to get the barrel but over it or will I still have to remove it? FSB will need to be removed to change barrel nuts, even after shaving. If I remove it will I need to replace the pins to put it back on or are they reusable? Taper pins can be reused if not damaged upon removal. I plan to install a free floating hand guard and all options I’ve seen require me to replace the barrel nut. The majority of FF handguards do require using the manufacturer's proprietary barrel nut. There are a handful of manufacturers that offer FF handguards that will mount to a USGI style barrel nut. Just trying to think through this before I do it. |
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I've always gotten pins out without much trouble, theyre tapered and only drive one direction. Most people that run into issues tried driving them the opposite way. Like big bore said measure the pin size on each side. They make fixtures for it, ive always just clamped it with a C-clamp between a couple pieces of wood, with wood underneath both sides to leave the pin a spot to hammer through. Soak in kroil. Hit with a little heat. And use a punch larger than the pin head. Real good hard smack and it should go. May need to tap the old block off if its carbon locked. Deadblow hammer for that. Set screw gas blocks are generally adequate. Harder to move than you would think. However you can always make dimples or pin the block down the road if you feel like it. Tools. You need a hammer. A punch. And for the new gas block you need a 3/32 Allen wrench. Gut n tight works, I use torque specs for everything 20-25 in/lbs. I even put a little smidge of rocksett on the threads. Never struggled to get them out after. However, if you ever strip a gas block screw tightening it, simply hammer a t10 bit into it. Itll come right out. |
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Originally Posted By TGWLDR: Shaving the front sight tower would be the the easiest course of action. https://i.postimg.cc/rsfC5yRq/images.jpg But yes, swapping to a low profile gas block is pretty straightforward. Hammer the pins out, remove the front sight tower, and replace with gas block of your choice. Set screw options, when installed correctly , work fine. Everybody has their pet brands. SLR, Daniel Defense, and Yankee Hill Machine are my preferred. Another vote for just cutting the existing sight base down. It's free to do and if your covering it up with the rail you'll never notice the difference. |
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Originally Posted By seek2: In addition to set screw blocks, there's clamp-style blocks. I use them exclusively and have never had a problem. Quite a few of the adjustable gas blocks are the clamp style, and they make doing barrel changes pretty easy. I had a clamp on block on one build and it was in so tight after a could couple thousand rounds I had to cut it off when I wanted to swap handguards. Only negative about the clamp on is that they are a little bulkier. |
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Originally Posted By RogueSpear2023: I vote for chopping it off. Nothing more sturdy than taper pins short of welding it on This, I have one 14.5" with a low profile pinned flash hider so I can drive the pins out and swap the barrel nut if needed for a new rail. Its the most solid gas block you can have, and would be the absolute last rifle I would ever part with. Otherwise you could chop or keep the front site and use a Centurion or Midwest Industries two-piece free-float rail. |
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Originally Posted By 64tinc: What kind of block do I need to set the old gas block in to remove taper pin. I put it on rubber handle of some pliers. I keep chasing it around though. Need something to keep it tight. While I hammer old pin out. It's tight in there.. A front sight bench block is handy. Many use these: https://www.brownells.com/tools-cleaning/gun-tools/gun-sight-tools/ar-15-front-sight-bench-block/ A solid workbench or a concrete floor with oak blocks is my preferred. My blocks have a relief drilled for the pins to pass through. I use a section of 5/8" brass round as a drift to shock them loose initiallly then follow with an appropriate sized steel punch to drive them out. |
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Originally Posted By TGWLDR: A front sight bench block is handy. Many use these: https://www.brownells.com/tools-cleaning/gun-tools/gun-sight-tools/ar-15-front-sight-bench-block/ A solid workbench or a concrete floor with oak blocks is my preferred. My blocks have a relief drilled for the pins to pass through. I use a section of 5/8" brass round as a drift to shock them loose initiallly then follow with an appropriate sized steel punch to drive them out. I made a DIY block from a scrap 2x4. |
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