On my new build my handguard ever so slightly touches my gas tube at the start of the handguard where the metal ring bit is on the end. I am thinking I can grind it down with a dremel to get the handguard free floating appropriately, but wasn't sure if I should do that or just find another gas block. Any opinions? Thank you.
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Handguard touching gas tube
- Thread starter ROAR
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That's not OK at all for accuracy, and you're not going to get enough clearance to account for flex unless you cut away the handguard completely around the gas tube. You'd need a different handguard to work with that gas block correctly, or change to a low profile block with the gas tube down close to the barrel.
Is the handguard parallel to the barrel?
It shouldn't do that unless the gas block holds the gas tube too high.
If it's not parallel, I would look at the barrel nut end and see if there is a way to fix it there instead of start grinding.
It shouldn't do that unless the gas block holds the gas tube too high.
If it's not parallel, I would look at the barrel nut end and see if there is a way to fix it there instead of start grinding.
I was wondering if I would get enough clearance by chopping away at it, which is why I considered just going with another gas block. There didn't seem to be a ton of .875 low pro blocks out there, but I'm sure I can track something down that should work. Thank you for the reply.
It should be parallel, no reason to believe it isn't. I think what's happening is the metal edge at the top/front of the handguard comes down a bit more than the actual handguard so there is reduced clearance there. If the gas block sat inside the handguard it probably wouldn't be an issue.
I don't think that applies to the handguard I have. Thank you for the idea though, it's not something I would have even considered if I did have the style that would work on.
https://lancer-systems.com/awc/carbon-fiber-handguards/#1484056665701-5a6e674e-4eb5
Wasn't even thinking of the what style of handguard was only suggesting that if the receiver hasn't been squared that the barrel could possibly be sitting nose high as a result.
See I wasn't thinking right at all, I should have hushed. Thank you for clarifying though. Good to know this stuff. I'll have another look at things.
You really need more clearance than just a little bit you might get by grinding. Barrels, handguards, and receivers all flex under load and while firing; you don't want the barrel or anything attached to it to contact the handguard at any point if you're looking for accuracy and consistency.
The minimum amount of clearance I'd want all around that gas tube is about the thickness of your handguard, so obviously if you grind that much away, you'll be left with an open slot and the handguard will be weak.
I think you are overestimating the required clearance, the standard for free floating a barrel on a bolt action stock is one or two dollar bills thickness.
I would want to see more than that but it doesn't have to be 1/8", the gap can be pretty small.
I would want to see more than that but it doesn't have to be 1/8", the gap can be pretty small.
You think so? LOL. Maybe you should spend a minute investigating barrel and forend flex on any of your rifles before you get back to us.
I'm not overestimating anything, I'm speaking from experience. The dollar bill thing with a rifle at rest isn't a "standard" for anyone except bubba with a deer rifle that only needs to be a 4 moa gun. I'd bet the OP is looking for something better than that. If you don't try to flex the barrel and forend around to see where/if they touch, you really don't know until you see the contact marks in the forend.
I'm not overestimating anything, I'm speaking from experience. The dollar bill thing with a rifle at rest isn't a "standard" for anyone except bubba with a deer rifle that only needs to be a 4 moa gun. I'd bet the OP is looking for something better than that. If you don't try to flex the barrel and forend around to see where/if they touch, you really don't know until you see the contact marks in the forend.
Thanks for all the info guys. I have looked around for another .875 adjustable block that the gas tube sits a bit lower in, but it appears that the adjustable factor is what causes the tube to be raised up more than with a non adjustable block. That and the .875 gas block options seem sparse. I may just go with a non adjustable block, but losing the ability to adjust the gas is a bit of a damper. I would think accuracy over desired gas operation is ideal though (assuming the block at least allows the gun to cycle properly 
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Is it just me or does it look like there's a gap between the bottom of the gas block and the journal? Otherwise, that's just too small of a hand guard for that set up. Lancer?
It is beveled inwards a bit, but there is still a gap there. I just inspected it and can see light between the block and journal (small gap).
Can't really tell about bevel in pic but shouldn't be any gap (at least any more clearance than necessary to slide gas block on). Any chance it's a .936 block on .875 journal?
Looks like a sizeable gap to me - especially when there should not be any gap. And it's not like .061 is a light year either. The difference between .936 and .875 is the smallest of all the gas block size steps. It wouldn't be the first time it was done. At any rate, this is incidental to the original question (other than it's a big gas block and a small hand guard). Maybe it's just the pic.
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I agree with that.
That's the point though - to have enough clearance that it won't touch under whatever conditions you'll put it in. The dollar bill clearance you recommended doesn't even come close to accomplishing that, unless it's measured at maximum flex of both the barrel and handguard in opposite directions.
Looking at the block to barrel fit at the top of the barrel compared to the bottom it looks wrong. Should be no light between barrel and block.
I would fix that first. That would most likely give you your clearance.
Looks like a Faxon Carbon Fiber. I wouldn't change that out either. Got a 17" version for a 12.5" SBR to recces the suppressor. Super nice light weight hand guards.
I would fix that first. That would most likely give you your clearance.
Looks like a Faxon Carbon Fiber. I wouldn't change that out either. Got a 17" version for a 12.5" SBR to recces the suppressor. Super nice light weight hand guards.
The gas block is beveled inwards at the bottom and not the top, so it makes the fit look funky in the picture, but like I stated in a prior post, there is a visible gap at the bottom too. It is the Lancer LCH5 hand guard and sometime tomorrow I am going to take some measurements on some things as well to potentially clear up some of what is going on.
Short of an obvious burr, other imperfection, or debris, the chance of significant barrel misalignment is minimal. Pull the gas block off and you should be able to look at the barrel/hand guard alignment easily enough to see if something's off. If there is, it's most likely the hand guard.
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A small angle at the barrel nut can move it enough out at the gas block journal.
You can lap or otherwise true your upper received to make sure the barrel seat is square to the receiver bore.
The human eye is pretty good at spotting angles so if you take the handguard off and just look at the barrel, you'll probably see any problem. You could also put a straight edge on the flat top and measure down to the barrel close to the barrel nut and out at the gas block journal. Add half the diameter of the barrel where you measure and that will tell you if there is any slope.
The act of taking it apart and carefully inspecting everything is the first thing to do. Then put it back together paying attention to anything that might not line up properly. Repeat until you have either identified or resolved the problem.
You can lap or otherwise true your upper received to make sure the barrel seat is square to the receiver bore.
The human eye is pretty good at spotting angles so if you take the handguard off and just look at the barrel, you'll probably see any problem. You could also put a straight edge on the flat top and measure down to the barrel close to the barrel nut and out at the gas block journal. Add half the diameter of the barrel where you measure and that will tell you if there is any slope.
The act of taking it apart and carefully inspecting everything is the first thing to do. Then put it back together paying attention to anything that might not line up properly. Repeat until you have either identified or resolved the problem.
Superlative Arms has a bleed off style gas block with a height of 1.552" and if from your link I have the right handguard the I.D. is 1.7" giving you clearance of .074" at the closest dimension. The gas tube is actually fitted slightly below the top of the block so you'll gain a couple thou more so it might have enough pending flex and possible expansion due to heat. If you are certain you want to keep the handguard I would give it a spin, will cost you 100 bucks though. I've started using those and so far I've been impressed.
I would happily buy a 100 dollar gas block if it works. However, looking at the dimensions of the block you mentioned, I don't think it will fit. I believe gas blocks are generally not symmetrical on the barrel. The top is usually taller than the bottom, of course due to the tube needing to come out of it etc. So if you take the dimension of 0.922, which is that gas blocks measurement from the middle of the "barrel" to the top of the gas block and assuming my handguard is equally as straight as the barrel, you can divide 1.7 by 2 and get 0.85, which doesn't accomodate for 0.922.
This should really give me something to go on and seems like solid advice. I am going to hit the garage in a minute and have a peek. Thanks again.
JP sells a pretty small OD Adj. GB... and I assume that is a LCH5 FF tube .. right ?
https://www.jprifles.com/buy.php?item=JPGS-10D
The height of the JP is 1.32" so the gas tube should be better off... compared to the ODIN 1.564 "height"
https://www.jprifles.com/buy.php?item=JPGS-10D
The height of the JP is 1.32" so the gas tube should be better off... compared to the ODIN 1.564 "height"
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