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MH64
04-11-07, 18:47
Have a low profile gas block that I need to install on a barrel. The gas block has two set screws on the bottom and the barrel already has a dimple for one of the set screws.
What type of locktite should I use on those set screws?

Also, I need to get a strap wrench to install a DD M4 rail and was wondering if there is anything you guys recommend? Or what to look for or avoid?

Figured I'd try to find something local (Lowe's, HD, auto parts...) instead of ordering.

uranus
04-11-07, 19:39
Red threadlocker on the set screws.

A thinner wrench with a thinner strap seems to work best. There isn't a lot of space between the handrail and the upper receiver, and it can be difficult using a wrench with a wide base or wide band. Lowe's and Home Depot have strap wrenches, but there will likely be a better selection at an auto parts store. IIRC, I paid 6.99 for a two-pack of strap wrenches with plastic/composite handles. I also have a heavy-duty aluminum strap wrench, but I don't use it on handrails. (The auto parts store will have the Locktite or similar, too.)

talbalos
04-11-07, 19:47
Red threadlocker on the set screws.
No more than a drop on the thread of each set screw before screwing them in. No need to bed the block to the barrel.

And I use blue threadlocker on fasteners as small as gas block set screws.

Robb Jensen
04-11-07, 21:05
For guns that I'm trying to squeeze all the accuracy I can out of I use green Loc-Tite to bed the block to the bbl (it keeps the rounds from stringing in between distances) and I red Loc-Tite the bbl to the upper receiver. I also use red Loc-Tite or Rocksett on the set screws after dimpling as least the rear one into the barrel a tiny bit (at least 1/8" on a .750" bbl). When it's an option I prefer to cutdown the FSB and make it fit under a FF tube or rail as a pinned gas block is the most reliable (and use green Loc-Tite to bed it and use a tiny bit on the pins).

I use a small strap wrench from Brownells.

Jinete_Palido
04-14-07, 18:49
Gotm4,

Could you explain a little more about bedding the gas block? Where are you putting the Loctite (i.e. so it doesn't get into the gas port)? Also, when you put red Loctite on the barrel, will there be issues if you ever want to separate the barrel and upper?

I am starting to get a little more serious about tinkering with ARs, and am curious about some of the tricks used by those with more experience. Thanks in advance.

JP

Ellery Holt
04-14-07, 19:03
Gotm4,

Also, when you put red Loctite on the barrel, will there be issues if you ever want to separate the barrel and upper?


I don't use the red loctite in the barrel-to-receiver mating, but it wouldn't be a problem because I, like at least a few others, consider the barrel and receiver to be a permanent pairing. When I retire a barrel the receiver gets retired too; buy a new barrel I buy a new receiver to go with it.

Razorhunter
04-14-07, 20:23
I too am interested to hear what "bedding the gas block to the barrel" means. ????
Does this mean smearing loctite on the bbl, under the gas block, thus promoting some type of seal or fastening method or what?????
Thanks...

Dan Carey
04-14-07, 20:55
Most gas blocks are slightly oversize to facilitate installation and removal. I build AR's and always check the size of the ID of the gas block and cut the barrel area that will be under the block .002 smaller than the hole in the block. I don't bed the block but I do hone the ID of the block before measuring it to remove any burrs. On factory barrels and whomever's block, you will have a much greater clearance between the two and you could Loc tite them with some success.

Jinete_Palido
04-15-07, 14:19
Paul,

I'm no expert, but my understanding of bedding the gas block is similar to why you bed a standard bolt-action rifle action to a stock, i.e., to eliminate play between the two components. Accuracy is promoted by consistency, whether that be in your ammunition, the way you hold the firearm, or the arrangement of the components of the firearm itself. In theory, if there is play between the gas block and barrel, they can be in slightly different relation to each other between shots, therby affecting barrel harmonics and all the other little demons and bug-a-boos that affect accuracy. I am not sure how much difference it makes, and it depends a lot on what you are looking for from your rifle. I come from a competive benchrest shooting background, where tenths or even hundredths of an inch in a group at 100 yards can matter quite a bit. With what most of us use an AR for, that amount of difference just isn't going to matter. Still, coming from that background, I can't help but be interested in the tweaks that can make an AR more accurate. That being said, I am building a rifle I hope to be able to use for multiple purposes, including shooting little ground squirrels up to 250 yards away.

I have a Noveske barrel and a Larue low profile gas block I am putting together. There is no noticable play between the barrel and the gas block when I slide it onto the barrel. Should I even worry about bedding the gas block under these circumstances? If I was going to do it, it seems like the best/easiest way would be to use an overabundance of Loctite in the set screw holes and try to keep things oriented so that no excess runs to the top of the barrel where it might interfere with the gas port. But that is just my best WECSOG guess.

The barrel is going in an Vltor MUR upper, and there is some slight play between the barrel and upper. I guess with the upper being a little more expensive than a standard one I was thinking I might reuse when I eventually shoot the barrel out (me being cheap, and all). I guess I should either just bite the bullet so to speak and go ahead with the red Loctite when I install the barrel, or install it without the Loctite and see if it shoots to my expectations. If it doesn't, maybe I could then to take it all down and reinstall with the red Loctite to see if that makes any improvement. I am probably overthinking this (I have a tendency to do that).

At this point I am kind of thinking out loud and appreciate any thoughts or suggestions from those with more experience. Thanks Dan and Ellery for the responses so far, as well as anyone else willing to contribute.

JP

C4IGrant
04-15-07, 15:26
When I am doing a custom build, I like to build up the area around the GB with KG or Cerakote and then tap the GB on (VERY tight fit). I also coat the barrel extension to I get a very tight fit as well.

GB's that are going on SERIOUS use weapons, need to be pinned.


C4

Robb Jensen
04-16-07, 04:50
Gotm4,

Could you explain a little more about bedding the gas block? Where are you putting the Loctite (i.e. so it doesn't get into the gas port)? Also, when you put red Loctite on the barrel, will there be issues if you ever want to separate the barrel and upper?

JP

The LocTite makes the gas block/FSB fit the barrel fit very tightly and glues it to the barrel. This keeps the assembly tight, if it's slightly loose (so little that you can't feel it) the FSB can move a tiny bit which changes the harmonics of the barrel and makes the rounds string up and down when shooting at longer distances because everytime the rifle fires the harmonics are acting differently. If the gas block/FSB to barrel relationship are rock solid the harmonics are always the same. I've never had enough get into the gas port where it effected function. The 20K psi and heat pretty much keeps it clear. If I ever want to remove a gas block mounted in this way or a receiver from a barrel a very hot heat gun is my friend. On ARs where I've painted the gas block and barrel with GunKote or Norrells I don't use LocTite to bed as it's not required then. The finish makes for a tighter fit.