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Old October 11, 2018, 03:47 PM   #1
kymasabe
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A2 front sight to Lo-Pro gas block questions...

Admin: If this is in the wrong category, please move to The Smithy.

I'm thinking of disassembling the upper that I currently have and ditching the A2 front sight post and delta ring and installing a free float handguard and low profile gas block. I have two concerns:

1: The A2 is pinned in place. When I slip on the new lo-pro gas block that has set screws on the bottom, am I going to have an issue with the set screws landing on the edge of the grooves the A2 taper pins sat in and moving the gas block out of position? Or, will that vary depending on which gas block I buy? Or should I buy a block that clamps on rather than uses set screws...or cut down/grind and reuse the old A2.

2. The old A2 currently has a ring in front of it that holds the handguard in place. If I get a new gas block, do I need to worry about leaving a gap between the gas block and the shoulder/stop on the barrel that it sits against, a gap roughly the same thickness as the old handguard retaining ring/cap? Do I need to worry about gas port alignment? Or, just ram the gas block all the way on, straighten, and tighten, as it's designed to seat fully against the stop on the barrel without worry?

Thanks for the tech tips !
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Last edited by kymasabe; October 11, 2018 at 10:14 PM.
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Old October 12, 2018, 06:36 AM   #2
Mobuck
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1:This IS possible but I've not had it happen that way. A clamp on is preferable IMHO regardless. A short gas block may not hide the groove for the forward pin BTW. I've cut down a couple of FSB but I'll say getting the pins out and re-using them doesn't work well. (you'll have to remove the FSB to replace the barrel nut if your free float HG uses it's own nut)
2: I've not had a problem with the lack of that front HG retainer causing alignment issues with the gas port. Side to side alignment is critical though.
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Old October 12, 2018, 04:36 PM   #3
kymasabe
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I chickened out and ordered a new barrel instead of stripping the old receiver I have. Just didn't have the heart to do it.
New slick side receiver is here, ordered the handguard yesterday (Odin Works Ragna 12.5 inch), ordered the barrel this morning, ordering the gas block tomorrow (probably Yankee Hill Machine clamp on).
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Old October 12, 2018, 08:43 PM   #4
Mobuck
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Sounds like an OK selection of assorted parts.
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Old October 12, 2018, 11:25 PM   #5
kymasabe
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Update: wasn't sure what gas block would fit under the Odin Works handguard so...I ordered an Odin Works low profile gas block with set screws, and a Kaw Valley set screw dimpling jig.

Here's the new rig I'll be building.

Anderson Slick side upper receiver: https://www.righttobear.com/Anderson...-p/m4slick.htm
Anderson .223 Wylde 1:8 nitride Barrel: https://www.andersonmanufacturing.co...black-nitride/
Odin Works Ragna 12.5 handguard: https://www.odinworks.com/M_LOK_Fore...f-12-ml-ra.htm
Odin Works gas block: https://www.odinworks.com/Low_Profil...ck_p/gb-75.htm
Kaw Valley dimpling jig: https://www.kawvalleyprecision.com/K...g-jig-.750.htm
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Old October 13, 2018, 02:21 AM   #6
marine6680
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Get some high temp red loctite and with a dimpled barrel, that gas block won't come off any time soon.

If you really want it to stay, in addition to the thread lock, get some loctite high temp retaining compound, and use that between the gas block and barrel, just don't get it in the gas port... That thing will not come off ever again. Lol

For a fresh barrel... I prefer set screws on a dimpled barrel. Done properly it's highly reliable. The military used set screw gas blocks on some rifles, and didn't have any issues.
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Old October 13, 2018, 08:05 PM   #7
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"If you really want it to stay, in addition to the thread lock, get some loctite high temp retaining compound"
threadlock is not needed with bearing and stud retainer, it's 100% effective alone.
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Old October 13, 2018, 11:14 PM   #8
marine6680
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Lol yup!

But some are paranoid.

For a defensive rifle I can understand wanting a but more assurance. BCM uses both, and their blocks don't come off easy.
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Old October 13, 2018, 11:40 PM   #9
kymasabe
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Well, I ordered two cobalt bits from McMaster-Carr, plan in putting the dimpling jig in the vise under my drill press to dimple the new barrel. I read that nitride barrels are a mother to drill. I did plan on using blue loctite on the set screws, never heard of retaining compound before though. Not sure if I'd want to use retaining compound though, if this barrel sucks, would like the option of removing it and swapping the gas block onto the next barrel.
Question: I ordered some aeroshell grease to put on the barrel nut threads, but Odin Works says to use vibra-tite thread locker on the barrel nut. Your thoughts on either?
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Old October 14, 2018, 12:24 AM   #10
ed308
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I've always used Aero Shell grease on the barrel nut threads. I've used Blue Loctite on the barrel extension that slides into the upper receiver it the fit was loose. I've also used Blue Loctite on the gas block threads and even between the gas block and barrel if loose as a way to seal it. Personally, I would never use Red Loctite since it can be difficult to break loose. I've never tried to dimple a Nitride barrel. Very difficult from what I've read so doubt I would bother. Really not that difficult to align and lock into place with the set screws. Never had one come loose.
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Old Yesterday, 06:03 AM   #11
Mobuck
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I use common mechanic's "never seize" on the threads. Thread locker? Why? The barrel nut is captured (so to speak) by the gas tube.
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Old Yesterday, 06:57 AM   #12
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What I've done is if I want to go free-float and you have a pinned A2 front sight - get out the die grinder. I cut the sight post and the bayonet lug off, clean it up and shape it with the air sander, then hit it with exhaust header paint.

That let's you still use the pins, which I feel is a far superior method of attachment. Plus you don't need to buy another gas block...
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Old Yesterday, 08:27 AM   #13
9x19
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"The barrel nut is captured (so to speak) by the gas tube."

Not with any of the slim free floating hand-guards in vogue today. The gas tube passes over the barrel nut rather than through it, and there is no need to index the barrel nut if the HG simply clamps to the nut. Those that attach to the nut via screws do still need to be indexed.

The HG kymasabe linked to is one of the slim (clamp-on) variety.
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Old Yesterday, 08:57 AM   #14
Ricklin
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Heat is your friend

Hi, My name is Rick and I am a Loctite addict.

Use your nose when working with Loctite. It does not take a lot of heat to release Loctite. Use your nose, you can smell the Loctite when you get it hot enough to release. It has a sickly sweet odor.

For fasteners where plastic, wood, or finished parts are adjacent use the appropriate driver bit in the fastener, and apply heat to the driver bit. Quickly switch to a cool driver bit and break the fastener loose.

A soldering iron can also transfer enough heat to a fastener.

I will admit to not having any experience with the high heat varieties of Loctite. The above methods work on the regular stuff.
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Old Yesterday, 11:35 AM   #15
kymasabe
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Thank you all, I appreciate the input.
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Old Yesterday, 01:28 PM   #16
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Quote:
I chickened out and ordered a new barrel instead of stripping the old receiver I have. Just didn't have the heart to do it.
New slick side receiver is here, ordered the handguard yesterday (Odin Works Ragna 12.5 inch), ordered the barrel this morning, ordering the gas block tomorrow (probably Yankee Hill Machine clamp on).
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You did the right thing IMO--I have removed fixed A2 front post sites but it's a colossal PITA IMO if the manufacturer has really locked it down good and hard--which most do.

I have several barrels without dimples that I've attached screw-on blocks and have run them for years with no issues of moving--torqueing down the screws make their own dimples. I'd be very reluctant to drill the barrel before verifying the block was properly aligned--so if it were me I'd probably run a few rounds first and then remove the block--you should see an incipient halo of carbon around the gas port which should give you an idea of how it's lined up as well as getting a gas system check for proper rifle functioning. Just my opinions--not saying that's the way it's supposed to be done.
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Old Yesterday, 01:55 PM   #17
9x19
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Aside from the parts, my biggest expense when changing barrels was a set of crow-foot wrenches to use on the latest style barrel nuts. My PSA 9mm upper went from 16" to 8" and got a shorter hand-guard to boot.
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