Set screw gas block and loctite [Archive]

loki993

11-11-15, 08:01

I have a 6920 with the A2 front sight. Im going to run a PRO on it eventually and id also like a different handguard so I need to change over to a lo pro gas block. I've been reading and you either pin them or use set screws. Screws seem easier because you can DIY that easily.

So all that aside, Ive seen people say put some loctite on the screws to keep them from moving. I understand the idea behind it but when I actually think about it Im curious. Most people say use the red. The thing is to remove the red you heat it up to 500 degrees. Considering hot gas is going through that block every time you shoot id expect it to get pretty hot. 500 degrees hot? I dont know, but it wouldn't surprise me. Also loctite has a continuous work temp of 300 degrees max.

So I guess the question is people putting the loctite on their gun thinking its locking the screws down, when in reality after shooting it for a while it may not be doing anything at all.

Again I don't have any actually data, aside from the temps for the loctite, this was just something Ive been thinking about since Im trying to figure out what gas block to get ans wonderinf if it has crossed any else mind...or even if someone has tested anything like that.

How hot does the gas block get actually on average?

rjacobs

11-11-15, 08:08

cut down your existing FSB. Cost=0(if you have the tools). Longevity=100, its never going to move.

I think its funny when people say "red loctite takes 500 degrees of temp to break loose" which isnt my experience with it, at least on small fasteners, and I use plenty(I am sure more than the recommended amount). Ive never had a problem breaking small fasteners loose that were "secured" with red loc-tite. Is it better than nothing, absolutely, but I personally dont think, at least on the small fasteners on firearms, that its that hard to break loose. For real high temp thread locker you want to look at rocksett. Withstands something like 2000 degrees but only takes around 30ft. lbs. to break loose. Thats what I use on set screws on gas blocks.

loki993

11-11-15, 09:23

556BlackRifle

11-11-15, 12:14

I was just going strictly off of the instructions for the loctite. Thats where the 500 degree thing comes from.

And just another thing wont I have to remove the gas black anyway if I ever want to change the barrel nut for a free float tube?

Here. (http://www.loctiteproducts.com/tds/T_LKR_RED_tds.pdf) It has a service temp of -65F to 300F. (To remove, heat to 500F.)

556BlackRifle

11-11-15, 12:24

OP, if you're not going to shave your FSB, have your barrel dimpled for the GB set screws. I've used Loctite Red and never had a problem with one coming loose. Rockset (http://www.brownells.com/gunsmith-tools-supplies/general-gunsmith-tools/thread-locking-liquids/flexbar-rocksett-2-oz-sku100010681-54624-105809.aspx) would be another good option.

Re the FSB, I like to save everything so if I ever want to put it back the way it was, I don't have to go through all the trouble and expense of fitting a new FSB. Shaving will work and if done correctly, it can look original. You'll find lots of threads if you do a search.

Auto-X Fil

11-11-15, 12:43

Shaving is fine. I prefer that to most aftermarket blocks, in fact.

Also, they make clamp-on blocks that are much better than the set-screw type. Just get one of those if you don't have the tools/skills to chop your FSB cleanly.

loki993

11-11-15, 13:06

Here. (http://www.loctiteproducts.com/tds/T_LKR_RED_tds.pdf) It has a service temp of -65F to 300F. (To remove, heat to 500F.)

Right, so all I was saying was does the gas block get hotter than 500 degrees? 300 even because the locktite is losing strength at that point. It was more a curiosity than anything else, but also bringing it up because that locktite may not be working as well as they think it is.

Im not opposed to shaving, I was just saying eventually Ill probably want a free flat tube and then Ill have to take it off anyway. So if the shaving is just to save the work of taking it off thats not an issue,

but now I think if it shaving saves me at least 50 bucks, having to dimple my barrel or have someone pin another gas block on. Not to mention...it works....

JasonDTM

11-11-15, 13:11

Rockset (http://www.brownells.com/gunsmith-tools-supplies/general-gunsmith-tools/thread-locking-liquids/flexbar-rocksett-2-oz-sku100010681-54624-105809.aspx) would be another good option.

iirc Rockset is not good for small set screws and the like.

Iraqgunz

11-11-15, 15:28

As I recall I have heard about similar issues as well. But, alas as humans we have to reinvent shit instead of using what works.

iirc Rockset is not good for small set screws and the like.

Iraqgunz

11-11-15, 15:30

Clamp on blocks are crap compared to set-screw type. I have seen screws breaks and misaligned blocks more times than not. Set screw blocks work fine when installed properly.

Shaving is fine. I prefer that to most aftermarket blocks, in fact.

Also, they make clamp-on blocks that are much better than the set-screw type. Just get one of those if you don't have the tools/skills to chop your FSB cleanly.

GH41

11-11-15, 15:35

Setscrew GB... Use cup tip screws properly torqued and staked and you will be good to go. Isn't staking of the gas key and castle nut acceptable?? I thought so.

ace4059

11-11-15, 16:23

Also, they make clamp-on blocks that are much better than the set-screw type. Just get one of those if you don't have the tools/skills to chop your FSB cleanly.

negative ghost rider.

Clamp on are prone to breaking the screws and the gas block itself. It's the way the torque clamps the gas block and binds the screw when added with heat cause problems. They can also be torqued too tight and in rare cases cause problems. Clamp on are NOT the way to go. If you can't or do not have the tools to shave the fsb or dimple the barrel for set screws then pay a competent gunsmith.

rjacobs

11-11-15, 16:27

iirc Rockset is not good for small set screws and the like.

In my experience no thread locker is good for small set screws. I can break red easily with no heat and I can break rocksett easily on small screws using no water(the supposed dissolver of rocksett). I will take something over nothing though and on a gas block I tend to use rocksett over red loc-tite.

Auto-X Fil

11-11-15, 17:22

Clamp on blocks are crap compared to set-screw type. I have seen screws breaks and misaligned blocks more times than not. Set screw blocks work fine when installed properly.

Fair enough. I'm fine with clamp-on when installed with proper alignment, high-quality fasteners rated for the job, and proper torque. I've seen a few cheap set-screw blocks fail, but they were un-dimpled. I agree that a quality block dimpled and staked would be fine. Of course, both methods require some skill and care to do right, although it requires less sophisticated tooling to install the clamp-on style.

In either case, I wouldn't use anything but pins on a block not covered by a rail - that's not the discussion here, though.

elephantrider

11-11-15, 22:01

Im not opposed to shaving, I was just saying eventually Ill probably want a free flat tube and then Ill have to take it off anyway. So if the shaving is just to save the work of taking it off thats not an issue,

but now I think if it shaving saves me at least 50 bucks, having to dimple my barrel or have someone pin another gas block on. Not to mention...it works....

I would just shave the existing A2 FSB and use that when you are ready to switch over to a FF handguard. Your 6920 barrel is already pinned for your existing FSB, and it really doesn't make sense to use anything else, since another gas block will require additional $$, modification to your barrel, and not do any better of a job as a gas block.

556BlackRifle

11-12-15, 09:58

Right, so all I was saying was does the gas block get hotter than 500 degrees? 300 even because the locktite is losing strength at that point. It was more a curiosity than anything else, but also bringing it up because that locktite may not be working as well as they think it is.

Im not opposed to shaving, I was just saying eventually Ill probably want a free flat tube and then Ill have to take it off anyway. So if the shaving is just to save the work of taking it off thats not an issue,

but now I think if it shaving saves me at least 50 bucks, having to dimple my barrel or have someone pin another gas block on. Not to mention...it works....

loki993, Sorry. I misunderstood your question. Yes the GB can reach temperatures well above 500F depending on rate of fire. Shaving is definitely the cheapest and quite possibly the most reliable way to go.

SteveL

11-12-15, 10:06

I would just shave the existing A2 FSB and use that when you are ready to switch over to a FF handguard. Your 6920 barrel is already pinned for your existing FSB, and it really doesn't make sense to use anything else, since another gas block will require additional $$, modification to your barrel, and not do any better of a job as a gas block.

This is what I would do as well.

556BlackRifle

11-12-15, 10:09

iirc Rockset is not good for small set screws and the like.

I've only used it on one build but I guess one could argue that no thread locker at all might be just as effective. It's an upper that I built for a buddy. He's used it in a few carbine classes and a shitload of shooting sessions (guessing maybe 5,000 to 6,000 rounds by now) and it's still going strong.

GH41

11-12-15, 17:08

I've only used it on one build but I guess one could argue that no thread locker at all might be just as effective. It's an upper that I built for a buddy. He's used it in a few carbine classes and a shitload of shooting sessions (guessing maybe 5,000 to 6,000 rounds by now) and it's still going strong.

It would still be going strong with nothing on the screws. Next time you build one put the thread locker of your choice on one screw and nothing on the other. Let us know when one of them falls out. This thing has been way overplayed.

Iraqgunz

11-12-15, 17:22

I have seen it numerous times.

It would still be going strong with nothing on the screws. Next time you build one put the thread locker of your choice on one screw and nothing on the other. Let us know when one of them falls out. This thing has been way overplayed.

Auto-X Fil

11-12-15, 20:01

Clamp on blocks are crap compared to set-screw type. I have seen screws breaks and misaligned blocks more times than not. Set screw blocks work fine when installed properly.

Ok, you made me sufficiently paranoid.

http://ptmaynard.com/guns/IMG_5252.JPG

Clint

11-12-15, 21:53

In my experience no thread locker is good for small set screws. I can break red easily with no heat and I can break rocksett easily on small screws using no water(the supposed dissolver of rocksett). I will take something over nothing though and on a gas block I tend to use rocksett over red loc-tite.

This is exactly why we provide knurled tip set screws with our gas blocks.

The knurled tip provides a bit of mechanical lock with no concerns about heat and eliminates the need for a chemical thread locker.

556BlackRifle

11-12-15, 23:30

Ok, you made me sufficiently paranoid.

http://ptmaynard.com/guns/IMG_5252.JPG

Clamped and pinned!! LOL.. I don't think you have much to worry about there. :) But the ainti-roll pin people may beg to differ. ;)

Hwikek

11-13-15, 00:46

Get a low profile gas block pinned to the barrel. A properly pinned gas block is the most secure. Most FSBs are pinned so that is why people recommend that you shave one down as it will not come loose during the process. Loctite is good for keeping your sights and rails attached to your rifle but most people seem to prefer blue Loctite for this purpose.

patriot_man

11-13-15, 01:30

A crucial step that people do not perform is cleaning and de-greasing the threads with acetone before applying loctite.

Iraqgunz

11-13-15, 02:03

Correct. I have had to resort to extreme measures to remove some gas blocks after heat and Un-Cure would not work.

A crucial step that people do not perform is cleaning and de-greasing the threads with acetone before applying loctite.

BufordTJustice

11-13-15, 07:38

Correct. I have had to resort to extreme measures to remove some gas blocks after heat and Un-Cure would not work.
Same. If the surface prep is properly done, things get mad-scientist real fast when Loctite red 271 was used. I have had to drill a gas block's screws out because the Allen bit still rounded off even after the healthy application of heat using a torch; I started to worry about the temper of the barrel steel because I didn't have my infrared thermometer on hand. I even broke a broken-screw-extractor bit AFTER soaking it for hours in uncure, hence the drilling.

I am an ardent proponent of the Knurled cup tip set screws. I've also had good experiences with Resbond 907TS Blue high temp, medium strength thread locker.

Slippers

11-13-15, 09:49

Besides proper surface prep and using knurled cup tip set screws, another trick is to take loctite 290, the penetrating variety, and put a couple drops on the barrel right at the front of the gas block. It wicks between and then sets and expands, making an extremely tight fit. It doesn't matter if you go past 500 degrees, either, because it's a friction fit from the expansion rather than relying on the grip.

This is how you "bed" a WOA national match front sight base, which is only secured with two side set screws and a bottom set screw, and no barrel dimples. And let me tell you, when you want to remove the front sight base, it's a pain in the ass.

Plasman

11-13-15, 10:58

Same. If the surface prep is properly done, things get mad-scientist real fast when Loctite red 271 was used. I have had to drill a gas block's screws out because the Allen bit still rounded off even after the healthy application of heat using a torch; I started to worry about the temper of the barrel steel because I didn't have my infrared thermometer on hand. I even broke a broken-screw-extractor bit AFTER soaking it for hours in uncure, hence the drilling.

I am an ardent proponent of the Knurled cup tip set screws. I've also had good experiences with Resbond 907TS Blue high temp, medium strength thread locker.

Besides proper surface prep and using knurled cup tip set screws, another trick is to take loctite 290, the penetrating variety, and put a couple drops on the barrel right at the front of the gas block. It wicks between and then sets and expands, making an extremely tight fit. It doesn't matter if you go past 500 degrees, either, because it's a friction fit from the expansion rather than relying on the grip.

This is how you "bed" a WOA national match front sight base, which is only secured with two side set screws and a bottom set screw, and no barrel dimples. And let me tell you, when you want to remove the front sight base, it's a pain in the ass.

"Blue" Loctite 242 will do this too. I had a hell of a time trying to get a gas block off that was put on with a healthy amount of blue loctite on the screws. It wicked between the gas block and barrel and even after the screws were removed made it very difficult to get the block itself off even after heating it up with a torch.

lysander

11-13-15, 10:59

Right, so all I was saying was does the gas block get hotter than 500 degrees? ...
At a steady rate of fire of 10 rounds per minute, after about 20 minutes the temperature of the barrel at the gas block (20" barrel) will stabilize at around 400 degrees F.

For the same rate of fire, with a CLGS the temperature would probably be just around 500 degrees F, maybe a tad less (gas block approx. 7 inches from the breech).

If you get your rate of fire up to 60 rpm, you can easily exceed 500 F in 20 minutes.

But, you are burning through a lot of ammo....

AM-15

11-13-15, 18:32

Do you people really think that if the temperature gets above the point Loktite starts to soften that your nub/cookie cutter type screws are going to walk out and disengage ?
Really ?
If you use the nub screws with the cookie cutter end, it will bite into the barrel and when properly torqued will not move.
I apply blue Loktite just for insurance(as Loktite is used for).

To clarify;
Oil/grease free clean the barrel and gas block in question.
Install gas block on barrel in proper position.
Apply your choice of Loktite to cookie cutter type nub screw THREADS (not the tip/cookie cutter portion).
Torque and let dry 24 hrs.

Your done.

Clarence

lysander

11-13-15, 21:46

Clamp on gives better grip, and if the screws are torqued properly will not break.

BufordTJustice

11-13-15, 23:14

Iraqgunz

11-14-15, 02:11

I had to cut some off the barrels. My hypothesis was that it was a combination of the knurled tip screw, the type of dimples and the Loctite 271.

Same. If the surface prep is properly done, things get mad-scientist real fast when Loctite red 271 was used. I have had to drill a gas block's screws out because the Allen bit still rounded off even after the healthy application of heat using a torch; I started to worry about the temper of the barrel steel because I didn't have my infrared thermometer on hand. I even broke a broken-screw-extractor bit AFTER soaking it for hours in uncure, hence the drilling.

I am an ardent proponent of the Knurled cup tip set screws. I've also had good experiences with Resbond 907TS Blue high temp, medium strength thread locker.