tighten the carry handle on the m4

[ridgerunner70]

how tight should the bolts be torqued on the carry handle?

[Iraqgunz]

You shouldn't have to tighten them more than finger tight.

[ST911]

Thumb screw, thumb tight.

[JSantoro]

^^^This. If you're feeling puckish and want it tighter, go to finger-tight and add 90deg with a tool in the slot of the thumbscrew...but be prepared to carry that tool with you if you ever need to get it off for some reason or another.

Whether you go finger-tight or a bit extra, use a paint pen or something to make witness marks on the screw and the interface they're mounted to so you have a visual indicator of where they ended up. That way, if they back off, all you have to do is re-tighten to the witness marks. That gives you the consistency you need to ensure that you maintain whatever zero you end up putting on that thing, whenever you have occasion to remove/reinstall the carry handle.

[Quib]

http://farm5.static.flickr.com/4067/4446995164_1567257fba_o.jpg

[tracker722]

******

[armakraut]

Do they actually stay tight over time like that?

The only time I never used loctite on an ACOG scope mount, it was flopping around by the 2nd mag.

[GeorgiaBoy]

Do they actually stay tight over time like that?

The only time I never used loctite on an ACOG scope mount, it was flopping around by the 2nd mag.

I hate being a necroposter, but I am very interested in this.

I would think that with all the loctiting/tourqing/ect. that is always recommended with the AR platform would carry over to things like carry handles. It kind of surprises me that a SIGHT should only be "hand-tightened" on...

What exactly keeps it tightened? How do you know that the screws don't back off? If they back off, and are re-tightened, can this affect your zero?

[GTifosi]

'Usually' mounting such items calls for tightening down, firing several rounds, then tightening again.

Doing such, for want of a better phrase, shakes the loose spots out where things might not neccisarily be fit as well as they could be with the initial tightening.

Done properly loctite or whatever isn't needed.
Provided of course the screws and nuts are of a a quality make and material.

FWIW I take the easy way out becuase I have spastic fingers: penny tight, nickle loose.
As in never use anything tougher or bigger than a penny to do the tightening on the slotted nuts. The penny will bend if you get too tight giving a decent indicator that you sould probably stop there.
Using a nickle to loosen will always overcome the penny due to the size, and thus leverage, difference.

Removal, retightening, etc. and maintaining zero is a function of mount quality and rail quality.
If all are in suitable spec then there won't be enough room for things to shuffle enough to lose zero.
Sloppy rails and mounts make for sloppy affixment and inconsistant zero retension.

[everyusernametaken]

I use a nickel for both tightening/loosening on my ACOG and carry handle, whichever I'm using at the time. I never have any loosening whatsoever, even over a couple hundred rounds in a single session.

After positioning whatever I'm mounting on the rail, I apply downward and forward pressure on the scope/handle against the rail grooves, while tightening the screws to finger tight. This always aligns the device precisely the same from one time to the next, and I often don't need more than maybe one click adjustment of the scope to get back to perfect zero. Last time didn't even need one click.

[Bauer C]

I go hand tight then i use the back edge of my pocket knife and go just a little tighter. Never had it rattle loose and usually returns very close to zero @ 100 yards.

[Doc Safari]

A quarter works great. Don't overtighten.

Most of the time finger tight is plenty. I think I only had to tighten with a quarter on one CH on one rifle years ago.

[LtNovakUSA]

you could just hand tighten, and then use witness marks on the knobs to see if it works loose

[Blankwaffe]

Don't forget this little detail either:

http://m4carbine.net/showthread.php?t=60561

[a0cake]

Don't forget this little detail either:

http://m4carbine.net/showthread.php?t=60561

Yep. Push all devices forward in the rail slot and maintain forward pressure as you're tightening.

As far as torque on thumb screws, I go just barely past hand tight (how far depends on feel - but you should know what feels right - you shouldn't hear anything creak), then paint witness marks.

[masakari]

You shouldn't have to tighten them more than finger tight.

We had countless Marines whose RCOs and carry handles came loose while firing because they followed this practice, and subsecuently their shooting suffered.
Mount carry handle on receiver and push it forward in the rail. Tighten finger tight, then with a tool or quarter tighten one quarter to one half turn more. Use a silver sharpie or paint pen to mark index marks so that proper torque and zero may be attained after removal and reinstallation.

EDIT: i just realized that this thread is over two whole years old. Really people?

[matemike]

An old mechanical proverb:


Tight is tight, too tight is broke

[GeorgiaBoy]

EDIT: i just realized that this thread is over two whole years old. Really people?

Yes, really. I wasn't going to start a whole new thread when I could just revive this thread to follow up on some info in it. And guess what? I have learned some new things out of it I might not have known.

Necroposting to add useless or senseless information to a dead thread is one thing. To ask an additional question or a desire to have clarification is another.

[Blankwaffe]

An old mechanical proverb:


Tight is tight, too tight is broke

Yeap.....and there are different meanings of tight to different folks.I think saying hand tight,or thumb tight as IG and the others recommend is best overall advice for the majority of folks.

Personally Im a ham fisted monkey and can squeeze the eye balls out of a bowling pin.Adding a tool/coin to the scenario might actually let someone like myself tweak something if they are not paying close attention..

[GTifosi]

That's why I suggested the penny.
They have a fairly consistant yield strength so sort of act like a torque wrench when employed.
When it starts to distort, stop turning.

I couldn't tell you how many fixtures I've screwed up over a lifetime going for 'just snug', 'finger tight', or 'tightened securly'.

[Iraqgunz]

Here is my thought. I currently have a cut down carry handle BUIS on one carbine and have had carry handles on others over the years. They never came loose. Maybe there is some overthinking going on?

[Kokopelli]

Asimple torque wrench goes a long way for consistency. IIRC.. All mine say 65 inch-pounds for rail mounted devices. I normally use 45 inch-pounds.. Just because.. Cheers.. Ron

[ST911]

Maybe there is some overthinking going on?

It's the stuff the internet is made of.

[Kokopelli]

Simple really, just like any other fastener.. Read the spec and torque accordingly.. doesn't matter much exactly what it is.. LMO.. Ron

[everyusernametaken]

Simple really, just like any other fastener.. Read the spec and torque accordingly.. doesn't matter much exactly what it is.. LMO.. Ron

The torque spec on my ACOG mount per the manual is "tighten to finger-tight, then use a screwdriver or coin to tighten an additional 1/4 to 1/2 turn".

I normally follow torque specs very closely, and extensive mechanic experience from my years of racing have taught me an intuitive feel for how a threaded fastener is responding to tension, even beyond correct use of torque wrenches (fatigue can cause failure well below specs). This experience certainly helps even with more mundane tasks like this, but I don't know what is specified for these screws.

[Doc Safari]

Judging from this thread, and my post above from five years ago, I may have gradually developed the habit of tightening mine more than needed. I used to not do that.

I used to just hand-tighten then go past hand tight a little with a quarter, but somewhere along the line I started tightening until the nuts won't go any further because they loosened a couple times on my ACOG.

Lately, I've used a pair of slip-joint pliers to hold the quarter to tighten each nut all the way down until it stops. My ACOG came with the thumb nut mount, and particularly, the mount would eventually loosen from firing without torquing the nuts all the way down. I came back from the range a couple of times before I started cranking all the way down and the ACOG mount had actually loosened enough that I could turn the thumb nuts freely. I started putting a drop of nail polish on the threads before cranking down and never had any further problems. (I've since switched to an American Defense quick detachable mount for the ACOG).

So I may be inadvertently tightening too far on the carry handle. I've never noticed that this radical overtighteniing has damaged either the upper receiver or the clamp components, but maybe I should go back to just hand-tightening and go just past hand tight but more than I used to? Hmmmmm?

[Iraqgunz]

You are in the Top 10 spot for Necropost of 2017.


Judging from this thread, and my post above, I may have gradually developed the habit of tightening mine more than needed. I used to not do that.

I used to just hand-tighten then go past hand tight a little with a quarter, but somewhere along the line I must have had one loosen after doing that.

Lately, I've used a pair of slip-joint pliers to hold the quarter to tighten each nut all the way down until it stops. My ACOG came with the thumb nut mount, and particularly, the mount would eventually loosen from firing without torquing the nuts all the way downr. I came back from the range one day before I started cranking all the way down and the ACOG mount had actually loosened enough that I could turn the thumb nuts freely. I started putting a drop of nail polish on the threads before cranking down and never had any further problems. (I've since switched to an American Defense quick detachable mount for the ACOG).

So I may be inadvertently tightening too far on the carry handle. I've never noticed that this radical overtighteniing has damaged either the upper receiver or the clamp components, but maybe I should go back to just hand-tightening with a little more? Hmmmmm?

[Doc Safari]

You are in the Top 10 spot for Necropost of 2017.

Thanks, I do it just for you cuz I know you appreciate it.

(And if I'd started a new thread, you'd have said, "Why did you start a new thread. Didn't you do a search?") :jester:

[tehpwnag3]

It's good to see not a lot has changed in the last 7 years :sarcastic:

[1_click_off]

It's good to see not a lot has changed in the last 7 years :sarcastic:

Other than they stopped putting carry handles on the 6920 from the factory....

[kirkland]

Y'all must have some weak hands, I've never had a thumbscrew work loose on my rifle and I've only ever made them finger tight.

[jimbob2525]

hand-tight with a little blue loctite for good measure

[Doc Safari]

Of course, after posting this answer to another thread, my Google Fu found this thread that I wanted in the first place:



There is an ongoing debate as to how much to tighten the thumb nuts on a carry handle:

1. Thumb tight (that's why they're called "thumb nuts")
2. 1/4 turn or thereabouts past thumb tight with a quarter
3. Tightened down as far as the thumb nuts will go with a quarter and a pair of pliers. "Spend the quarter" is the motto here as you will probably bend the coin out of shape using this method.

The $64,000 question is whether overtightening is necessary to keep the sight from loosening, and whether excessive overtightening damages the carry handle or receiver.

The answer to all questions is "yes".

This is anecdotal evidence, but it has happened to two rifles (one Colt once BCM) and two quality carry handles.

One carry handle had been torqued 1/4 turn past thumb tight with a quarter. One had been tightened until it wouldn't move any further with a quarter clamped in a pair of pliers.

Here is the damage observed:

1. Both AR upper receivers sustained a minor "mark" in the form of a disturbance to the finish, and a tiny, almost imperceptible indent where the carry handle had clamped the receiver. The indent was roughly the width of a line on a piece of paper and had a depth that was only noticeable under a bright LED light at certain angles under a magnifying glass. This appears to be mostly cosmetic since it happened to a solid part of the rail. It did not get any worse with removal of the carry handle for installation of other optics. The other optics both had quick-detach clamps. The indent would not have even been noticeable in normal use, i.e. unless a person were looking for it under an extremely bright light, it was barely visible.

2. Both carry handles, on the other hand, sustained damage to the little "gasket" that goes up inside the thumb nut. Overtightening the thumb nuts harms this gasket. When the carry handle that has been overtightened is removed and then replaced, these "gaskets" on both carry handles shredded into strips as the thumb nuts were tightened a second time. This damage to the "gaskets" inside the thumb nuts did not prevent the thumb nuts from tightening down adequately, but in all cases the nuts were tightened past witness marks placed on them during the first tightening for reference.

The BCM rifle with the overtightened thumb nuts had fired between 6,000 and 7,000 rounds after the carry handle was installed, with no loosening of the carry handle or any additional scoring or other damage to the receiver rail. I always put a drop of nail polish or black paint on the top of the thumb nut bolts (thumb nut side) to prevent loosening from vibration.

Other rifles in which the thumb nuts were only hand tight suffered from loosening of the thumb nuts after less than 500 rounds (I did not take an exact round count; it could have been as few as 100-200 rounds before I noticed the loosening).

Conclusion: overtightening does appear to damage both the receiver rail and the thumb nuts, but in the case of the receiver rail it appears to be largely cosmetic. The damage to the thumb nuts probably necessitates overtightening that carry handle from then on since the inner "gasket" sustains quite a bit of damage from overtightening.

My take: I plan to use a large flat blade screwdriver or quarter to overtighten "just beyond" hand tight. A person with substantial hand strength may be able to get by with truly "hand tight". I have never had thumb nuts on an optic that did not eventually loosen when left just "hand tight", so if you plan to go that route then re-tightening the thumb nuts occasionally becomes part of the necessary equipment check.

Personally, I have decided if I need a rifle with strictly iron sights, I will seek out an AR with a fixed carry handle and avoid the hassle altogether.

[Knight NATO]

Please help me.����



I install my carry handle and use screwdriver to tighten the mount. But the carry handle moves rearward when I charge and close the bolt. It's fine or not . Thank you :confused:

[kirkland]

I chopped my carry handle so I can use it behind my aimpoint. So it only has one thumb screw. I feel the thumb screw for tightnes every once in a while when I pick the rifle up. It's never been loose and if it was I would just tighten it up real quick. Not a problem.

[opngrnd]

The guys I shooting with switch between irons and optics regularly, with both mounts using thumbscrews. They always do 40 inch pounds and it always gets them a good return to zero. I don't know if it's too much but it's been working fine for us.

[kirkland]

Consistency would be the key I think, whether it's thumbtight or if you measure it with a torque wrench.