Optic Mounting Problem - Cross Bolt Keeps Snapping

Captains1911 · November 30, 2017, 08:45 AM

I've been trying to mount a Sig Romeo 5 red dot to a standard flat top AR-15 upper, and three times now the cross bolt has snapped into two pieces. I know what you're thinking...I'm over torquing the bolt, however, I used a torque wrench set to 20 in-lbs for the first two bolts (per the instruction manual that came with the optic), and the the third time I dialed it back to about 16-18 in-lbs, and had the same result. After the first time it happened, Sig sent me a new base along with a replacement bolt and nut, which I swapped out before the third attempt, so I know it's not an issue with the base. It doesn't feel like I'm putting all that much torque on the bolt, certainly not enough for it to break like it is. I have mounted tons of optics like this with very similar cross bolts and never once had an issue. Any ideas?

GorillaGunworks · November 30, 2017, 10:24 AM

sorry to ask but are you sure you are using inch pounds? and second just hand tighten it with the correct size bit and snug it down with some blue thread locker you should be fine. it should not go anywhere AR's do not have much recoil no reason to go super crazy torquing to specs, you can snug it down by hand a use a little thread locker.

Captains1911 · November 30, 2017, 10:26 AM

Quote:

Originally Posted by GorillaGunworks

sorry to ask but are you sure you are using inch pounds? and second just hand tighten it with the correct size bit and snug it down with some blue thread locker you should be fine. it should not go anywhere AR's do not have much recoil no reason to go super crazy torquing to specs, you can snug it down by hand a use a little thread locker.

Yes, definitely inch pounds....

Smoke & Recoil · November 30, 2017, 10:48 AM

I agree with GorillaGunworks...but I will add, there are book smart engineers and hands-on-people...follow GorillaGunworks advise.

reynolds357 · November 30, 2017, 06:50 PM

I have always used 8 in.lbs in those size bolts. Go to the hardware store and get some grade 10 alloy bolts if you want to put a death grip on them.

November 30, 2017, 08:45 AM	#1
Captains1911 Senior Member Join Date: November 18, 2009 Location: West of the Blue Ridge, VA Posts: 684	Optic Mounting Problem - Cross Bolt Keeps Snapping I've been trying to mount a Sig Romeo 5 red dot to a standard flat top AR-15 upper, and three times now the cross bolt has snapped into two pieces. I know what you're thinking...I'm over torquing the bolt, however, I used a torque wrench set to 20 in-lbs for the first two bolts (per the instruction manual that came with the optic), and the the third time I dialed it back to about 16-18 in-lbs, and had the same result. After the first time it happened, Sig sent me a new base along with a replacement bolt and nut, which I swapped out before the third attempt, so I know it's not an issue with the base. It doesn't feel like I'm putting all that much torque on the bolt, certainly not enough for it to break like it is. I have mounted tons of optics like this with very similar cross bolts and never once had an issue. Any ideas? Last edited by Captains1911; November 30, 2017 at 09:03 AM.

November 30, 2017, 10:24 AM	#2
GorillaGunworks Senior Member Join Date: August 5, 2013 Posts: 116	sorry to ask but are you sure you are using inch pounds? and second just hand tighten it with the correct size bit and snug it down with some blue thread locker you should be fine. it should not go anywhere AR's do not have much recoil no reason to go super crazy torquing to specs, you can snug it down by hand a use a little thread locker. __________________ "No free man shall ever be debarred the use of arms." - Thomas Jefferson, Virginia Constitution, Draft 1, 1776 https://www.youtube.com/channel/UC1b...RUE9AMVlI88MrQ

November 30, 2017, 10:48 AM	#4
Smoke & Recoil Senior Member Join Date: August 23, 2008 Location: East shore of Lake Michigan. Posts: 714	I agree with GorillaGunworks...but I will add, there are book smart engineers and hands-on-people...follow GorillaGunworks advise. __________________ Sent from my Tandy 1000

November 30, 2017, 06:50 PM	#5
reynolds357 Senior Member Join Date: December 10, 2012 Posts: 6,165	I have always used 8 in.lbs in those size bolts. Go to the hardware store and get some grade 10 alloy bolts if you want to put a death grip on them.