Gas Block Advice Please

Status
Not open for further replies.

tbass23

Member
Joined
Apr 23, 2011
Messages
18
Location
Cincinnati, OH
Hello,
So a few months ago I put a free float hand guard on my AR15 and went with an aluminum gas block. I allowed the guy at the LGS to talk me into it and I almost immediately regretted it. I have taken the rifle out once since I installed the GB and put a over 100rds through it with 100% reliability.

Since then I have bought a steel gas block because everything I have read online has said aluminum GB are a failure waiting to happen. So here are my questions:

1. Would you ahead and put the steel GB on the rifle or wait until there is an issue?
2. Has anyone had success with aluminum GB's? How many rounds have you put down range with it?

Thanks everyone,

Ty
 
If you have the tools to do the work I'd replace the aluminum gas block. While I was at it I'd replace the gas tube as well.

Is your replacement gas block a clamp on or pin on variety?
 
Simple answer. Replace the aluminum gas block with the steel and keep the aluminum one as a back up in case of failure of the other unit.
 
If it is a rifle length gas system, leave the aluminium gas block on it, they were meant to be used with rifle gas.
 
The original front sight base on the M-16 is aluminum, which is also a gas block, and they work fine. Unless your SPECIFIC design of gas block has a history of problems, it should be fine.

That said, if this is a weapon you will be trusting your life to, and the steel gas block gives you more peace of mind, then swap it out. If this is a fun gun, just leave it.
 
I have never had a failure in an aluminum gas block, as long as it did not use set screws.
 
The original front sight base on the M-16 is aluminum, which is also a gas block, and they work fine. Unless your SPECIFIC design of gas block has a history of problems, it should be fine.

That said, if this is a weapon you will be trusting your life to, and the steel gas block gives you more peace of mind, then swap it out. If this is a fun gun, just leave it.
You are not even remotely correct. The front sight post on the M16 is made from a steel forging. If it is in proper spec to the technical data package this front sight base will also be parkerized separate from the barrel, and pinned in place with taper pins when installed.

OP, I would ignore the above quoted post.

If you want a dead nuts reliable gas block it should be made of steel and should be pinned in place. Anything less is a compromise used out of convenience and cost savings.
 
If you want a dead nuts reliable gas block it should be made of steel and should be pinned in place. Anything less is a compromise used out of convenience and cost savings.

Pinning a low-profile gas block is unnecessary for an AR to be "dead nuts reliable".
 
Really?

So why do Colt, LMT, Daniel Defense, Bravo Company, SIONICS weapon systems, and other reputable manufacturers of duty grade AR's use pinned gas blocks exclusively? Think of all the time and money they could save by just using clamp on blocks or blocks that utilize a set screw and dimpled barrel.

What proof do you put forth to support your claim?

I can point to the US military's technical data package, as well as the common practices of top tier AR builders, all of whose experience indicates that a pinned in place gas manifold is the way to go. Given that the US military is the single largest end user of this operating system in the world, it stands to reason they may know a few things about what works and what does not.
 
Steel is always better, but attachment method is more important. The best is pinned on (if your barrel has the holes for the pins). Next best is clamp on. Worst is the ones with the stupid little allen screws.
 
Most AR assemblers are just that.

They have no clue other than buying stuff off the internet and throwing it together; literally.

If one would take the time to contact the barrel manufacturer and get a print of the specs.
If one would take the time to contact the gas block manufacturer and get a print of the specs.

If the two will have a good tolerance of fit then they will function together using those stupid allen screws, which in MHO are the next step from a pinned gas block.

Using the cookie cutter set screws into a machined flat in the barrel is as secure as it gets.

Good luck AR assemblers, enjoy yourself :)
 
My 1st match gun used a cut down GI gas block. It worked fine through the 4500 rnds I shot through it before replacing the barrel. It leaked at the gas block from the gas tube from day one.
The 2nd barrel uses an aftermarket aluminum gas block that looks more snazzy and has held up through 1500 rounds so far. It leaks around the gas tube.
This is exclusively a 24" NRA High Power match gun. I'll post here if it gives me any trouble.
 
I have used set screw aluminum and steel gas blocks, pinned ones, and cut down sight assemblies back before low pros were readily available, and i agree that steel is better. I also agree that pinned is better than clamped or set screwed. But i haven't had a failure with any. I also won't use a gas block that isn't made well no matter where it came from. BTW if you use one with set screws use locktite! And you can drill and pin any gas block once it's all set up right.

Sent from my LGLS740 using Tapatalk
 
Really?

So why do Colt, LMT, Daniel Defense, Bravo Company, SIONICS weapon systems, and other reputable manufacturers of duty grade AR's use pinned gas blocks exclusively? Think of all the time and money they could save by just using clamp on blocks or blocks that utilize a set screw and dimpled barrel.

What proof do you put forth to support your claim?

I can point to the US military's technical data package, as well as the common practices of top tier AR builders, all of whose experience indicates that a pinned in place gas manifold is the way to go. Given that the US military is the single largest end user of this operating system in the world, it stands to reason they may know a few things about what works and what does not.

You're making a very silly argument, on a few levels. To sum up my point, it's called real world shooting. There are tons, literally, of ARs out there with low-pro gas blocks that aren't pinned, and virtually none of them have problems. There is no pattern of guns having problems as a result low-pro gas blocks not being pinned, but still being correctly attached. Until you can show me that, you're just a guy who argues about theories and stuff not meeting his personal standards on a gun forum. But since I have the time, here are the problems with what you are saying...

1. Not all of the companies you list pin their low-pro gas blocks. In fact, only 2 of the 5 do.
2. The TDP is irrelevant, because we've already deviated from that standard by not using a FSB.
3. A FSB performs functions that a low-pro gas block doesn't, like being a sling attachment point. It is also more exposed on the barrel.
 
You're making a very silly argument, on a few levels. To sum up my point, it's called real world shooting. There are tons, literally, of ARs out there with low-pro gas blocks that aren't pinned, and virtually none of them have problems. There is no pattern of guns having problems as a result low-pro gas blocks not being pinned, but still being correctly attached. Until you can show me that, you're just a guy who argues about theories and stuff not meeting his personal standards on a gun forum. But since I have the time, here are the problems with what you are saying...

1. Not all of the companies you list pin their low-pro gas blocks. In fact, only 2 of the 5 do.
2. The TDP is irrelevant, because we've already deviated from that standard by not using a FSB.
3. A FSB performs functions that a low-pro gas block doesn't, like being a sling attachment point. It is also more exposed on the barrel.
BCM pins their gas blocks (at least all the ones I have handled had pinned gas blocks), so does Daniel Defense (I own one), so does Colt (at least on their 6920 with the shaved FSB gas block all other are pinned full FSB's). LMT did the last time I checked too.

Don't confuse the Colt Competition rifles with real Colt's they are not actually made by Colt's Defense.

Turns out SIONICS does not pin their gas blocks, I thought that they did.
 
In the future to sidestep ITAR consequences I see a lot of shooters going to clamp on gas blocks. Gunsmiths won't work on pinned blocks in the future.

If a gas block is a problem it's because of it's spacing from the shoulder - TDP requires the handguard spacer to place it correctly, remove it and the block moves back against the shoulder enough that some guns start to malfunction due to gas being choked off. It's reported a lot on DIY forums.

Aluminum blocks will eventually erode faster than steel - goes to how much they will be used. If the gun is a rental and getting 200,000 rounds thru it annually I could see the staff armorer not choosing them. On a recreational gun that may not see 1,000 rounds a year, not so much.

As said, milspec is to pin the FSB - it's a bayonet attachment point more than the sling pressure. Along with the actual sight tower sticking out getting banged around doing combat vehicle exits thru narrow doors - the FSB has the potential of being torqued severely, along with not needing to be monkeyed with by untrained users who have no idea what they are doing. Therefore Stoner pinned them on - but you don't have to. And in the future, your gunsmith isn't likely to touch them, either.

I see the great majority of barrels being sold with clamp ons in the future. It's what I used on my builds - and I don't have to take them to a gunsmith for alterations. A clamp on gas block eliminates that expense and makes the AR a more versatile design. It also eliminates drilling thru the barrel and then peening a pin into place - which has distorted the rifling on a barrel. It becomes even more difficult on pencil barrels or alternate calibers.
 
BCM pins their gas blocks (at least all the ones I have handled had pinned gas blocks), so does Daniel Defense (I own one), so does Colt (at least on their 6920 with the shaved FSB gas block all other are pinned full FSB's). LMT did the last time I checked too.

Don't confuse the Colt Competition rifles with real Colt's they are not actually made by Colt's Defense.

Turns out SIONICS does not pin their gas blocks, I thought that they did.

BCM doesn't pin their low-pro gas blocks, nor do they offer it as an upgrade option when buying from them directly. The gas block that they offer doesn't even have a hole for the pin to go through.

Colt doesn't pin their low-pro gas blocks, and yes I am talking about their competition series. The reality is, they are the only Colts, or "Colts", with low-pro gas blocks. The shaved FSB gas blocks are just that, shaved down front sight bases. They are pinned because that is the only way to attach them to the barrel.
 
Unless you are actually taking your rifle into harms way, I'd just set the steel one aside for a spare and replace the current one only if it fails. A gas block that is also the front sight sees a lot more stress than one tucked underneath a hand guard, so it needs to be pinned.

I've only seen one failed gas block, don't know if it was steel or aluminum, (I only saw a photo) but it failed at the thinnest cross section about even with the centerline. Could have been random infant mortality failure (all parts and technologies have some of these -- burn-in screening for high reliability electronics is to weed out these), but my guess was that the setscrews were overtightened.
 
I have pinned steel blocks, set screw aluminum and steel and clamp on steel blocks, with thirty rifles i have never had a gas block problem other than the one he set screws froze solid and i wanted to change rails. Many barrels are dimpled for the set screw on a gas block. Always take into consideration the spacer found on the frontsight/ gas block units (0.035) when installing your block.
 
Steel is always better, but attachment method is more important. The best is pinned on (if your barrel has the holes for the pins). Next best is clamp on. Worst is the ones with the stupid little allen screws.

Actually, set screw gas blocks have proven to be more reliable than the clamp on style. Clamp on gas blocks tend to bend the screws and they break.

When installing a set screw type gas block, drill dimples in the barrel for the set screws and stake the set screws in place
 
Pinned is secure - but you cannot reuse the holes. They are individually drilled to that specific FSB at the time of the installation. Matching them with another one is going to be an upscale machinists installation. Just redrilling the barrel isn't good, either.

They never came with a jig that installs them identically one barrel to the next. It was never considered as milspec never removes the FSB unless damaged, and it's high level depot maintenance to even bother.

Because slip on gas blocks are so much shorter the resulting installation on civilian guns previously pinned it to expose the front hole for all and sundry to see. These guys sell a DIY kit to pin your own lopro block http://modernserviceweapons.com/?p=8597 - but the point is check the pics. It was an FSB barrel with that gas block removed, and when done you have a ragged unused pin hole hanging in front of the new lopro block. They are all shorter than the FSB.

I suppose you could fill it with some JB Weld . . .
 
They never came with a jig that installs them identically one barrel to the next. It was never considered as milspec never removes the FSB unless damaged, and it's high level depot maintenance to even bother.
The cost of replacing the FSB on a M16/M4 would be more that 75% of the price of a new barrel assembly. The front sight base is not a stocked item, no NSN, in any case. That means even the depots cannot order a new one.

They can remove/reinstall the FSB on the same barrel to facilitate replacing the barrel nut, but if the FSB is damaged beyond usability, the whole barrel assy is scrap.
 
Tirod, Several companies make a low profile gas block that has sufficient length to cover the pin notches left when removing the sight/ gas block, they use ser screws for retention, check Brownells.
 
If you're not in Fallujah kicking down doors, doing mag dumps, I really doubt a clamp on aluminum gas block is going to fail you. However, steel is technically superior.
 
Last edited:
Status
Not open for further replies.
Back
Top