SMOS Precision build

[BoilerUp]

And I'd say that even if you do want to pin the GB, give it some time and a few hundred rounds to make sure you are happy with the set up first. The GSBs don't fit well under skinny handguards, either, so if you ever change out your handguard there is a good chance you'll have to change out your gas block, too.

[Das Jared]

I'm a fan of over-engineered stuff. I'm incredibly hard on my equipment. Buy once, cry once

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[Das Jared]

Well, got off the phone with Rainier. They won't pin my gas block. Oh well

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[Slippers]

If you install it correctly, pinning isn't necessary. A real mil-spec mk12 or mk18 doesn't have a pinned gas block, and keep in mind the mk12 had the gas block exposed, not protected under a handguard. If you call up Daniel Defense and have them build you a mil-spec mk18 upper with the correct gas port size, it will also include an unpinned gas block.

BCM also doesn't pin theirs, but removing the gas block from one of their uppers is extremely difficult.

Use high temp red loctite and knurled tip set screws, along with a proper dimple in the barrel, and it's not going anywhere.

[Das Jared]

If you install it correctly, pinning isn't necessary. A real mil-spec mk12 or mk18 doesn't have a pinned gas block, and keep in mind the mk12 had the gas block exposed, not protected under a handguard. If you call up Daniel Defense and have them build you a mil-spec mk18 upper with the correct gas port size, it will also include an unpinned gas block.

BCM also doesn't pin theirs, but removing the gas block from one of their uppers is extremely difficult.

Use high temp red loctite and knurled tip set screws, along with a proper dimple in the barrel, and it's not going anywhere.

Great post, thanks for the useful info. I had no idea about the spec mk12 & 18. My barrel is dimpled, and I will definitely be using the red loctite. Thanks again!

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[UWone77]

If you install it correctly, pinning isn't necessary. A real mil-spec mk12 or mk18 doesn't have a pinned gas block, and keep in mind the mk12 had the gas block exposed, not protected under a handguard. If you call up Daniel Defense and have them build you a mil-spec mk18 upper with the correct gas port size, it will also include an unpinned gas block.

BCM also doesn't pin theirs, but removing the gas block from one of their uppers is extremely difficult.

Use high temp red loctite and knurled tip set screws, along with a proper dimple in the barrel, and it's not going anywhere.

Let's see... a very small percentage of specially trained soldiers get issued MK12's and MK18's, while 99% of the rest use double pinned gas blocks... otherwise known as Front Sight Bases..

[gatordev]

Let's see... a very small percentage of specially trained soldiers get issued MK12's and MK18's, while 99% of the rest use double pinned gas blocks... otherwise known as Front Sight Bases..

I don't disagree with the intent of your post, but... MK12s get issued to not-specifically-trained-Marine-grunts. Marines in general aren't soft on gear. As for the MK18s...Lots of boat donkeys get issued MK18s, and they're not "all that" with their gear either. But I'm guessing Will isn't talking about an actual MK18 and instead meant a CQBR Block 2, in which case, both you and he has a point.

Personally, I have a few rifles that aren't pinned and don't even have red Loctite and they hold up fine (under a rail). But in a perfect world, given I don't ever want to use red Loctite, I'd pin my gas blocks if I had the means and/or the money. If for no other reason that a) peace of mind and b) I'm anti-red Loctite (because I'm lazy if/when I have to 'smith my own guns).

[UWone77]

I don't disagree with the intent of your post, but... MK12s get issued to not-specifically-trained-Marine-grunts. Marines in general aren't soft on gear. As for the MK18s...Lots of boat donkeys get issued MK18s, and they're not "all that" with their gear either. But I'm guessing Will isn't talking about an actual MK18 and instead meant a CQBR Block 2, in which case, both you and he has a point.

Personally, I have a few rifles that aren't pinned and don't even have red Loctite and they hold up fine (under a rail). But in a perfect world, given I don't ever want to use red Loctite, I'd pin my gas blocks if I had the means and/or the money. If for no other reason that a) peace of mind and b) I'm anti-red Loctite (because I'm lazy if/when I have to 'smith my own guns).

Yeah Will and I talked off line about pinned GB in the past.

Do you need a pinned GB? Probably not. However a pinned GB does ensure that the GB will come off if you decide to uninstall it later on. I'm with you on Red Loctite, I have a BCM upper that they slathered red loctite on and it never budged. I've seen other guys in my department just using set screws and they eventually had GB back out.

For me pinned GB are cheap insurance and make life easier when swapping out rails & barrels.

[Das Jared]

One question- what the actual fuck is a boat donkey

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[gatordev]

For me pinned GB are cheap insurance and make life easier when swapping out rails & barrels.

My apologies in this whole discussion...I was speaking from a recreational shooter's perspective. In any kind of service use, totally pin the GB. Because why not? I know, we're beating a dead horse.

One question- what the actual fuck is a boat donkey

It's a North American mammal that often lacks any kind of common sense or awareness of reality. Often times, they're witnessed to move in a path or direction that makes no sense, but it's what they know and are comfortable with because "that's what they did the last time." They are a peculiar breed, and one that will often times try and kill you if you're an outsider and/or have any outside knowledge of what happens beyond the lifelines of their tiny little ship. But at the same time, they also make your food and make sure you have a warm shower (sometimes), so it's sometimes necessary to tread lightly on their incapacity and/or deficiencies.

[BoilerUp]

I have a BCM upper that they slathered red loctite on and it never budged.

I love BCM, but this is pretty much what stops me from buying their complete rifles or uppers.

I like to put cheater marks on my set screws so I can tell if they are backing out with a quick glance.

[Das Jared]

So I tried to start assembling my upper last night; all sorts of problems. First off, the Geissele gas black is giving me all sorts of hell. Couldn't get the gas tube pin in, it ate 2 pins before it finally somewhat took a 3rd, and its still not how I want it. Then, it doesn't want to seat on the barrel, its freaking tight as hell. Into the freezer it went last night, and is waiting until I get home. 3rd, and this is my boneheaded fault, as I should have freaking checked before torquing the barrel nut on, but the dust cover door is out of spec, and doesn't want to latch closed. It seems like its too small. This build is fighting tooth and nail!

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[Pyzik]

Looking good. I'm in the process of an 18-20" 'SPR' now too and taking notes.

[Das Jared]

Well don't take notes from me, apparently I'm an idiot

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[Das Jared]

Oh, and for other people building using SMOS, your best bet for tightening the barrel nut is a crowsfoot wrench, size
1- 3/16. I ordered one off of amazon, but had to modify it with a grinder, because it was too wide to fit on the barrel nut.

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