View Full Version : Clamp On or Set Screw Gas Block
Which type of gas block is better for someone who is installing one for the first time, clamp on or set screw? I have done lots of searching and can’t find a definitive answer? Is it just preference or is one really better or easier to do right than the other? To me, the clamp on type seems easier, but i notice that most gas blocks on the market are set screw.
Clamp on may be easier, but a loctited set screw gas block with a dimpled barrel will be more secure. There are jigs on the market to set gas blocks.
Pinned through the barrel is the ultimate way to set a gas block.
Clamp on may be easier, but a loctited set screw gas block with a dimpled barrel will be more secure. There are jigs on the market to set gas blocks.
Pinned through the barrel is the ultimate way to set a gas block.
Are you talking about pinning one through where you removed a fsp and installed an aftermarket gas block and used the cut out or indention that is in the barrel? I’m wanting to remove my fsp and install a gas block but after punching out the pins it will have the indentions under the barrel and don’t believe a set screw gas block will be secure with that?
Military carbines are pinned. In the civilian market the industry standard is the set screw type. The best method is to buy a SLR Rifle Works gas block jig and drill a dimple. The jig is not expensive, you use it to mark the dimple in exactly the right place and its a tool that lasts so you can use it on your next build.
You won’t be able to use the cuts on the barrel from the removed FSB. I was referring to a virgin gas block and barrel.
You should be able to use set screws however.
Have you considered shaving the FSB if it will fit under your rail?
Set screw gas block with a dimpled barrel all the way. There are piles of videos on the YouTube that will explain it better than text on here will.
The key is having a dimple opposite the gas port to properly align the gas block.
With set screw blocks, the rear screw locates on the dimple, while clamp on blocks generally need to be eyeballed.
Our MicroPin gas block allows for easy pin drilling after installation, for the best of both worlds.
https://dqzrr9k4bjpzk.cloudfront.net/images/812059/294749845.jpg
ViniVidivici
02-18-19, 08:07
Yes I would say set screw type, with barrel dimpled for rear set screw, screws red loctited, and staked, would be much more secure than clamp-on. All that with a pin is best, of course.
If I were yhe OP though, I'd just cut down the existing FSB.
I am installing it on a new barrel. There is no FSB.
Are the set screw blocks all about the same from the different manufacturers or are any that are better than the rest?
I’ve used BCM, Vltor and BRT and had good luck with all 3.
ViniVidivici
02-19-19, 06:41
I have used Aero Precision and Ballistic Advantage.
There are cheaper ones out there, but I suspect it doesn't pay to skimp in this area. I like cheap parts, but I'd be worried about stripped threads, things being out of spec, etc. with cheaper blocks.
Pinned, clamp on, set screw, doesn’t really matter if its under a handguard, the port is aligned correctly, and threadlocker is used. I like pinned because its super easy and I almost can’t mess it up when I order a barrel that comes with a pinned block. I also hate tiny allen screws. No rocksett or loctite required with pinned. If I have a barrel with no gas block or dimple, I use a dimple jig with a set screw block because they tend to be low profile. With a pinned FSB, I shave it.
The M4 and M16 used taper pinned at least partly because the front sight base/gas block assembly is exposed, and Joe will inevitably drop his rifle, and/or tinker with anything that has a screw. “Look, Sergeant, I figured out how to clean my gas port!” And some idiot would probably be inspecting gas tubes at weapon turn-in.
This is of course just my opinion.
I use set screw gas blocks. They take up less room.
I think a clamp on might hold more securely but they are bulkier and sometimes the screws will shear.
Set screws into dimples is the way to go. I've dimpled all of my builds with the SLR jig. It has multiple choices to match the spacing between your gas block set screws. It uses a pointed set screw that you line up with your barrel gas port hole. Then just turn the block over and drill your dimples using the guide. Make sure that you get one for the barrel diameter that you are using. .75 is the most common. Measure the spacing on your gas block set screws, select the correct pattern on the jig. Very easy. .50 set screw spacing is very common but varies between manufacturers.
The dimples guide the set screw into their seat. Ensures proper secure alignment. Simple to use.
https://slrrifleworks.com/index.php?route=product/category&path=57_129
I have used Aero Precision and Ballistic Advantage.
There are cheaper ones out there, but I suspect it doesn't pay to skimp in this area. I like cheap parts, but I'd be worried about stripped threads, things being out of spec, etc. with cheaper blocks.
I’ve been looking at this for ne for $20 but can’t decide.
https://ballisticadvantage.com/750-lo-pro-gas-block-blem.html
They never say what the blemish is. Cosmetic, who cares but problems with the ports can be a pain in the cash.
ViniVidivici
02-20-19, 08:32
I would definitely get that one, the blem isn't going to be anything that affects function. That's a good deal.
There are cheaper ones out there, but I suspect it doesn't pay to skimp in this area. I like cheap parts, but I'd be worried about stripped threads, things being out of spec, etc. with cheaper blocks.
In reality, skimping anywhere in the gas system can cause issues.
The most common issue with cheap gas blocks is over sized bores for both the barrel and gas tube.
Loose bores cause excess gas leakage and variability in gas drive.
You won’t be able to use the cuts on the barrel from the removed FSB. I was referring to a virgin gas block and barrel.
You should be able to use set screws however.
Have you considered shaving the FSB if it will fit under your rail?
Have thought about it, actually and may go that route.
The key is having a dimple opposite the gas port to properly align the gas block.
With set screw blocks, the rear screw locates on the dimple, while clamp on blocks generally need to be eyeballed.
You do have to eyeball it, but designs with a split on the bottom typically have a hole drilled through the split (created as part of the step to make the gas hole) that can be visually aligned with the barrel dimple.
Springing for a nice gas block of whatever type you get is very much worth it, I've seen too many cheap gas blocks leak like crazy. Sparks going downrange, won't seal up even after 1k rounds.
Clint you have been one of the most reasonable and knowledgable members on this board contributing a wealth of knowledge. I'm glad to see someone as experienced as yourself express a common sense here. I see people are too focused on saving money often as little as $5-15 and maybe a total of $50 per rifle trying to score cheaper parts of either questionable quality or unknown blem issues. It's okay buying good quality parts on sale and/or cheaper. I personally stray away right now from any blem items. First of all - almost all blem items are non-returnable, second - it's not worth saving a couple of dollars on the part which you typically never replace unless there is an issue.
In reality, skimping anywhere in the gas system can cause issues.
The most common issue with cheap gas blocks is over sized bores for both the barrel and gas tube.
Loose bores cause excess gas leakage and variability in gas drive.
Over the years I have seen strap-on gas blocks come loose. One issue that seems to be common is the screws loosening and sometimes break from use. Ultimately, as Clint mentioned, an interruption of the gas system is going to lead to problems.
Straight Shooter
02-25-19, 17:47
Over the years I have seen strap-on gas blocks come loose. One issue that seems to be common is the screws loosening and sometimes break from use. Ultimately, as Clint mentioned, an interruption of the gas system is going to lead to problems.
IG- if YOU were building a 20" precision rifle..what low pro Gb would YOU use? Even give a top 3 or 5 list if you want.
Admittedly, I do not put much thought into this. I have used Geissele, BCM, Centurion Arms and the SIONICS blocks we have made. I cannot recall actually have an issue with any of them. In fact, I can't recall the last time one of my rifles had a malfunction when shooting.
Of course all my barrels are dimpled and set screwed or pinned as appropriate. All my gas tubes are properly aligned and all my BCG's used tested and vetted components.
IG- if YOU were building a 20" precision rifle..what low pro Gb would YOU use? Even give a top 3 or 5 list if you want.
Straight Shooter
02-28-19, 07:17
Thanks for that, IG.
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