Handguard clearance

[Coyote Kev]

So without jacking another guys thread, this needs to be specifically asked. How much clearance does one need? What I mean specifically is how much do you need to allow for barrel whip?

I have a 22” Dracos barrel in 6mm creed that sits under a SLR helix 16” handguard. Nothing touches but it’s pretty close due to the large diameter of the Dracos barrel. In fact, I can push the barrel up with my hand and the gas chamber hits or I can push it down and the bottom of the barrel hits my m lok rail screws for my bipod. I have dremeled some more clearance on those m lok screws but I can still push it down and touch them. Have I noticed accurance problems? Hard to say, still working on loads as this is a new build. This thing has been a bitch to load for but then so has my 260 with a Dracos barrel. The 260 has plenty of clearance on an aero m5e getup.
Any thoughts?

 

[...]

If you can fit a few pieces of paper between the barrel and the hand guard you are all set.

Barrels don’t “ whip” that much

ide be much more concerned to make sure to have clearance when its under loading from a bipod

 

[BLDTYLRY]

Depending on how much you load your bipod you can still have issues. Had a 0.875 Gas Block hit the MLOK screws ever so slightly and caused my groups to expand. Swapped out handguard with more clearance and group closed back up. BTW it was a SLR 16.5" Solo with their non-adjustable gas block, not enough clearance. SLR even told me it was on the tight side.

 

[longshot2000]

If you can fit a few pieces of paper between the barrel and the hand guard you are all set.

Barrels don’t “ whip” that much

ide be much more concerned to make sure to have clearance when its under loading from a bipod

I would disagree with that statement. The barrel actually much more, depending upon thickness between the chamber and the gas port. There is much more movement in lightweight, M4 and Gov't profiles than you might think. The barrel becomes a "wave" that whips and curves during firing. Slow-motion pics will show you much more movement than "a few pieces of paper."

I am not sure I can measure the harmonic movement, but what I have seen is at least 1/8" and possibly just more than 1/4" on all sides. HBAR and SOCOM profiles have much less movement.

 

[...]

I would disagree with that statement. The barrel actually much more, depending upon thickness between the chamber and the gas port. There is much more movement in lightweight, M4 and Gov't profiles than you might think. The barrel becomes a "wave" that whips and curves during firing. Slow-motion pics will show you much more movement than "a few pieces of paper."

I am not sure I can measure the harmonic movement, but what I have seen is at least 1/8" and possibly just more than 1/4" on all sides. HBAR and SOCOM profiles have much less movement.

assuming this is the barrel in question

https://www.dracosbarrels.com/product/6-5-creedmoor-ar-10-barrel-22-inch/



yeah..... that barrel is not going to become a"wave".......


if a few thou is enough clearance for a bolt gun......its enough clearance for a gas gun

 

[Snuby642]

Ask around and borrow an old school fat handgaurd to test.
Everybody is going slender these days, someone is bound to have a spare?
My YHM has about .200 above the gas block and over .250 the rest of the way around or better.
It's a medium 556 barrel.
That would be a cheap acid test.
Disassembly to big of a pain to give you proper dimensions .
Maybe the hand guard is what is flexing, looks very thin to me!

 

[Coyote Kev]

Ask around and borrow an old school fat handgaurd to test.
Everybody is going slender these days, someone is bound to have a spare?
My YHM has about .200 above the gas block and over .250 the rest of the way around or better.
It's a medium 556 barrel.
That would be a cheap acid test.
Disassembly to big of a pain to give you proper dimensions .
Maybe the hand guard is what is flexing, looks very thin to me!

I actually have a aero percision on a 260 rem that has plenty of clearance. Only problem is it’s a m5e style so I would have to switch out the barrels. It seems to shoot fine, I just find it odd how far I can flex the barrel without a ton of pressure. I can flex it up down or side to side and hit the handguard just using 1 hand and medium pressure.
So far I have just shot it off bags. No bipod.

 

[Strykervet]

Barrels do whip, thicker and shorter ones obviously whip less, but it's not observable to the naked eye. Any of the handguards out there will be fine, the new M110's use the URX4 tube and a thick barrel and it's not a problem; thin barrels work fine too and have more room. URX4 is damn thin too. Barrel whip is inherent to the barrel and they all do it to some degree, even fat ones.

Generally it'll get too hot to hold before the barrel whips into it IME and if it hits the handguard, you're gonna have other problems to worry about. The whip is enough to cause MOA fluctuations downrange but that's about it. If whip were any more noticeable then firearms wouldn't be practical because that whip translates to increased angle with respect to the trajectory, or in other words, tiny MOA shift at the muzzle, big MOA shift downrange.

The SOCOM cut barrels SEEMED to cut down MOA but the army has a 4MOA requirement for the M4 and a higher quality barrel would have cost more but weighed less and still been more accurate than the heavier cuts. The SOCOM barrels did hold up to more abuse and that's why SF got 'em. I saw some of the shit those guys brought back and I thought regular 11B's were rough on shit.

The ONLY time I ever saw an M4 barrel warp was this one guy who came into the SF gunsmith shop to get an M4 fixed while I was in there; he should have just DX'd the motherfucker. It had broken extractor lugs, the carrier itself broke I recall (which is what shut it down) and the barrel was no-shit warped from being shot to shit. And as you'd guess, the barrel shot loose. FWIW, he took good care of it though and it looked like a new rifle on the outside! All except for the powder burns and heat damage...