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Gas Blocks

This topic contains 21 replies, has 12 voices, and was last updated by Profile photo of First Sergeant First Sergeant 1 year, 7 months ago.

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  • #45838
    Profile photo of First Sergeant
    First Sergeant
    Moderator

    Max and I had a conversation about gas blocks during the FoF weekend.

    People are going to low profile gas blocks and are installing them at home. Several of the gas blocks on the market come with screws. This is a bad idea. Why? No matter how much loctite you use, there is the possibility that the screws are going to back out. When that happens, you now have a bolt action rifle. An example of that can be seen in one of the videos from Idaho.

    If you get a gas block, get one that uses taper pins to install it. It isn’t easy to take them out or put them in, but once installed, the chances of them backing out are almost zero.

    If you look at an AR that has a standard FSB, they are installed using taper pins, not screws. That should be a clue.

    I can hear it already, “but I have a gas block that uses screws and have never had a problem”. Not yet, but the potential is there for it to happen. Just like the guy in Idaho, never had an issue until he did.

    FILO
    Signal out, can you identify.
    Je ne regrette rien...
    Klagt Nicht, Kämpft

    #45841
    Profile photo of Joe (G.W.N.S.)
    Joe (G.W.N.S.)
    Moderator

    …never had an issue until he did.

    It’s surprising that anyone here would still be thinking that nonsense. :unsure:

    Here’s some “geek” technical data to consider for those ignoring First Sergeant’s and Max’s guidance concerning this issue.

    From Loctite:

    Loctite Threadlocker Red 271 is designed for the permanent locking and sealing of threaded fasteners. The product cures when confined in the absence of air between close fitting metal surfaces. It protects threads from rust and corrosion and prevents loosening from shock and vibration. It is only removable once cured by heating up parts to 500°F (260°C).

    So at 500°F Loctite Threadlocker Red 271 fails to be permanent!

    From Weaponsman:

    600-700 degrees F is where cook-offs begin, and that’s reached in as few as 140 rounds on rapid semi-auto fire.

    Note: That’s less than 5 “30 round magazines.”

    Here’s a table with some key temperatures for you (Weaponsman):

    Your choice, but I’ll stick to pinned!

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    #45845
    Profile photo of Max Velocity
    Max
    Keymaster

    Yep. These rifles that do not use pins are ok for plinking and three gun etc. But they fail when run under ‘combat conditions.’ Such conditions are simulated on MVT classes.

    #45850

    BRD engineering gas block drilling jig

    If not that, go with rockset not locktite

    CRCD/CP April 2014, CP August 2014, RC1,
    CTT/CP June/July 2015, Run n Gun/CQB/FoF 2016, DA Georgia 2017, DCH Georgia 2018

    #45852
    Profile photo of Joe (G.W.N.S.)
    Joe (G.W.N.S.)
    Moderator

    If not that, go with rockset not locktite

    A better glue is not the answer IMHO.

    #45858
    Profile photo of Jake
    Weber
    Participant

    I had never considered pinning my gas blocks until Max mentioned it and First Sergeant started this thread. There’s no reason not to do it, especially when a couple of guys, that may know a thing or two about the subject matter, are recommending it. It’s one less variable to worry about. I have a couple of BCM rifles, both of which have set screws on the gas block, which I’m going to take to Adco and have them both pinned. Good post. Hopefully everyone is listening.

    My mom said I could be anything I wanted to be when I grew up. So I chose to be a man.

    #45870
    Profile photo of Chris
    Chris
    Participant

    Just finished building an AR in my mom’s basement for DM role. Gas block is not pinned so I ordered a jig from BRD. Gas block will be pinned before the first round is fired from that weapon….. (I was in ID and saw one of the guys have to go to his back-up AR due to gas block not being pinned).

    Now that I'm over 50 I realize that my People Skills are fine...it is my tolerance of Idiots that needs work.

    #45871

    I am sort of OCD with certain AR stuff. If I do the low pro gas block myself, i mark put em on, shoot the gun a bit to test and make sure it is right then I pin it in place. BRD jig works

    CRCD/CP April 2014, CP August 2014, RC1,
    CTT/CP June/July 2015, Run n Gun/CQB/FoF 2016, DA Georgia 2017, DCH Georgia 2018

    #45892
    Profile photo of
    Anonymous

    A good gunsmith can take your F marked front sight post and cut off the post above the gas block, so it will fit under a free-float rail. Problem solved.

    #45897
    Profile photo of First Sergeant
    First Sergeant
    Moderator

    A good gunsmith can take your F marked front sight post and cut off the post above the gas block, so it will fit under a free-float rail. Problem solved.

    The key part of that statement is a “good gunsmith”.

    FILO
    Signal out, can you identify.
    Je ne regrette rien...
    Klagt Nicht, Kämpft

    #45932
    Profile photo of dnb
    dnb
    Participant

    Got a brd gas block jig for a geiselle gb. If someone needs to use it, let me know and we can work something out.

    #45983
    Profile photo of arealcorker
    arealcorker
    Participant

    I am one of the guys from the class in Idaho who had two guns go down. I thought I would give an update as to what I found wrong. To say that I was completely pissed that my guns went down was an understatement! I barely finished the class and felt I could have done a lot better if I had not had that snafu. But, that being said. I am glad that it happened in training and not when I needed them the most. So here goes. Gun number one which is a bushmaster that I put a free float geissele rail on and a geissele gas block that came with it. Not cheap parts and very well made. I never had problems with it at home but did not run it as hard as in class. It started fine but ended up double feeding so bad I could not clear it by the normal methods. When I go home I started going through inspections of all the parts and found the extractor spring had failed which is common in ar’s. But Why? So I replaced the spring and it worked better but still would get the occasional double feed. My gas block was not loose but I did notice some leakage from around the tube pin. I swapped out a spare gas block and it did not help. Still the double feed. At this point I was scratching my head and not sure if it was overgassed or under gassed. So Off came the gass block and I measured the port size. It measured .071″ WOW.. From the factory. It was way overgassed which explained why it trashed the extractor spring. So I either had to replace the barrel or put an adjustable gas block on it? I did some research and found probably the best gas block on the market. made by superlative arms. It is fully adjustable and will bleed off any excess gass not needed. And can be purchased with the clamp on style instead of set screw. Installed, adjusted and have ran 400nds with no stoppages. Love that gas block. My back up gun, yes is a home build that I skimped on the gas block and put a cheap no-name on. Big mistake. It did not come loose but was leaking around the gas tube enough causing it to be under gassed. Put another superlative gas block on it and it is running like a champ. Lessons learned. Hope it helps.

    #45989
    Profile photo of BrigandActual
    BrigandActual
    Participant

    FWIW, some leakage around the gas tube pin is normal. Every one of mine have it to some degree.

    All of my gas blocks are pinned. Two are factory BCM uppers with tower FSB, one is a BCM tower I had drilled/pinned to a barrel. AndThe last is a Centurion arms barrel I had matched with a pinned gas block when I bought it. In the end, it’s cheap security.

    "Man is still the first weapon of war" - Field Marshal Montgomery

    Matt B - VA

    #45998
    Profile photo of First Sergeant
    First Sergeant
    Moderator

    Your Post

    Thanks for coming here and giving an update.

    Yeah, .071″ is way to big for the gas port. It should be somewhere between .061″ and .063″.

    That is what caused your extractor spring to wear out. That is one of the issues with an over gassed rifle.

    Being over gassed is very common with Bushmasters and other manufacturers.

    This next part is not directed at you arealcorker, but to everyone in general:

    Stop buying rifles from manufacturers that don’t have a clue what the hell they are doing. “Just as good as” doesn’t fucking exist.

    Colt
    Bravo Company
    Daniel Defense
    LMT
    Larue
    KAC

    Stick with these. Anything else is a crap shoot.

    Note-I edited this and added KAC, I left it off earlier.

    FILO
    Signal out, can you identify.
    Je ne regrette rien...
    Klagt Nicht, Kämpft

    #46000
    Profile photo of Joe (G.W.N.S.)
    Joe (G.W.N.S.)
    Moderator

    Colt
    Bravo Company
    Daniel Defense
    LMT
    Larue

    While all of these are excellent AR’s I believe Colt is the best bang for the “buck” in the current market. Remembering that the Colt Expanse is a hobbyist choice IMHO.

    #46001
    Profile photo of First Sergeant
    First Sergeant
    Moderator

    Colt
    Bravo Company
    Daniel Defense
    LMT
    Larue

    While all of these are excellent AR’s I believe Colt is the best bang for the “buck” in the current market. Remembering that the Colt Expanse is a hobbyist choice IMHO.

    With prices now, yes Colt is the best bang right now.

    Agreed on the Expanse.

    FILO
    Signal out, can you identify.
    Je ne regrette rien...
    Klagt Nicht, Kämpft

    #46003
    Profile photo of arealcorker
    arealcorker
    Participant

    No offense taken! It use to be that Bushmaster made great guns. There for a time Bushmaster was hired by Colt because Colt could not keep up with the government contracts and their Q.C. was going down hill.. Now Bushmaster has been sold and Colt finally got their act together again. I believe Windom Weapons is made of mostly guys from the old bushmaster company and make a great ar!

    #46004
    Profile photo of
    Anonymous

    Stop buying rifles from manufacturers that don’t have a clue what the hell they are doing. “Just as good as” doesn’t fucking exist.

    Colt
    Bravo Company
    Daniel Defense
    LMT
    Larue
    KAC

    Stick with these. Anything else is a crap shoot.

    Note-I edited this and added KAC, I left it off earlier.

    FNH.

    #46007
    Profile photo of Joe (G.W.N.S.)
    Joe (G.W.N.S.)
    Moderator

    While all of these are excellent AR’s I believe Colt is the best bang for the “buck” in the current market.

    Something I wanted to add about the Colt offerings, since First Sergeant’s began his input on his recommendations on quality AR’s I’ve been seeking out friends and acquaintances current Colt AR’s to test for myself. Prior to these evaluations my experience with Colt had been it’s older offerings.

    The other First Sergeant recommendations I have some limited experience with and you certainly get great value at a premium price.

    #46020
    Profile photo of Jamison
    Jamison
    Participant

    Does anyone stake their gas block bolts if they use bolt on?

    It works for the gas key?

    Could someone use the same process on a steel gas block?

    Admit nothing. Deny everything. Make counter-accusations.

    Nulla fatere. Nega omnia. Accusatis calumniatorem. Demanda probationem.

    #46027
    Profile photo of riflemaniv
    riflemaniv
    Participant

    I just finished pinning my BCM gas block using the BRD jig. It took me about an hour start to finish with disassembly, pinning and reassembly. The hardest part was getting my hider/suppressor mount off. I used a roll pin for my pin because I misread the jig’s description on BRD’s site. The roll pin from a standard trigger guard fits perfectly. The jig does NOT include the taper reamer something I misread. I will be getting the taper reamer at some point and pinning my block correctly. I used a drill press and I think that is the way to go. If you were to use a hand drill I think I would drill from both sides a little at a time to make sure the hole lines up perfectly with both sides of the jig.

    CTT1504, NODF 1504, CP 1610

    #46039
    Profile photo of First Sergeant
    First Sergeant
    Moderator

    No offense taken! It use to be that Bushmaster made great guns. There for a time Bushmaster was hired by Colt because Colt could not keep up with the government contracts and their Q.C. was going down hill.. Now Bushmaster has been sold and Colt finally got their act together again. I believe Windom Weapons is made of mostly guys from the old bushmaster company and make a great ar!

    Where did you get this info? At no time did Colt hire Bushmaster.

    Bushmaster has never made quality AR’s. Some have gotten lucky with the ones they have.

    Stop buying rifles from manufacturers that don’t have a clue what the hell they are doing. “Just as good as” doesn’t fucking exist.

    Colt
    Bravo Company
    Daniel Defense
    LMT
    Larue
    KAC

    Stick with these. Anything else is a crap shoot.

    Note-I edited this and added KAC, I left it off earlier.

    FNH.

    Nope. Never recommended them and I wont.

    Ya’ll need to go read this thread to find out why I recommend the companies that I do.

    AR Manufacturers Parts 1, 1.5 and 2

    FILO
    Signal out, can you identify.
    Je ne regrette rien...
    Klagt Nicht, Kämpft

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