I've never used one like this style, but is putting that much torque (the 30-50 lbs different barrel nuts require) on the takedown pin holes of the upper a problem?
Gunsmithing AR Action Blocks
- Thread starter jda2631
- Start date
If you are installing barrels on an AR, you should already have an armorer's wrench for the barrel nut. This is what you want for the barrel itself, engages the locking lugs of the barrel, no torque on the upper receiver. Good unit.
https://www.brownells.com/gunsmith-...l-sku080000637-27452-53686.aspx?sku=080000637
https://www.brownells.com/gunsmith-...l-sku080000637-27452-53686.aspx?sku=080000637
I was actually told those aren't good to use by one of the guys at Compass Lake. I never had issues the few times I've used mine but was told the most issues they've seen were shearing index pins, which seemed to be pretty frequent, so I stopped using it after that.
I use a clamshell block to install barrel nut. It can put some marring on your upper so if it matters, some sort of tape on the receiver sides to prevent marring. I like how it braces off the entire receiver without putting stress on specific areas.
For timing muzzle devices or anything else I run with a reaction rod, although I stopped using crush washers a while back and just use timing shims for muzzle devices.
For timing muzzle devices or anything else I run with a reaction rod, although I stopped using crush washers a while back and just use timing shims for muzzle devices.
I dont, not when I hear one of the top precision AR companies out there has seen problems with them. Perhaps you should share your credentials since you are calling out theirs. Every time I have seen a thread with a sheared index pin I wondered how they did it. A sheared cam pin or sheered index pin are the only two ways I can think of an AR can fire out of battery.
WTF gives your short sighted self the idea that I called out their credentials. According to you, the world should stop using reaction rods because they either had or are aware of problems with indexing pins being sheared. Tell me the facts about the incidents where somebody sheared a pin. 80-90 lbs. torque maybe, tried to torque without torquing then loosening, then torquing and loosening...
All I stated was the fact that I have had NO problems whatsoever using a reaction rod! If you choose not to use one, you are certainly welcome not to, but you sure as hell are not the be all, end all in the AR world!
Once upon a time somebody said the world was flat...
This is what makes me think that. Care to explain this remark to me then? It would look to me like you are questioning their knowledge,abilities, and advice based on your "many barrels done." So qualify your remark.
dude never called anyone out....calm down
also, them being a top company doesnt preclude them from the potential of fucking shit up like the rest of us.
frankly ive not heard of anyone having this issue.....im sure they did manage to break a couple....if youre doing hundreds of guns a day, chances are you are going to run into weird issues that most of us wont see...however if it were a wide spread issue im sure it would be plastered everywhere by now.
I use the Magpul BEV block to support the upper assembly when tightening to removing barrel nuts. Like the reaction rod, it is splined to engage the barrel extension.
ETA: the BEV block has a recess and cross hole that mates with the upper's front lug and comes with a pin to stick in there so it provides support for both the barrel and receiver. It also has a backwards facing stud with an oring to connect to a bolt carrier inserted in the upper.
So it can be used for any upper work including barrel nuts, muzzle devices, and even working on the bolt carrier itself.
ETA: the BEV block has a recess and cross hole that mates with the upper's front lug and comes with a pin to stick in there so it provides support for both the barrel and receiver. It also has a backwards facing stud with an oring to connect to a bolt carrier inserted in the upper.
So it can be used for any upper work including barrel nuts, muzzle devices, and even working on the bolt carrier itself.
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Being a top company lets me know they build a lot. People who are at the forefront in the industry tend to be the ones finding these kind of problems. When I first saw the design of the splined the wrench I wondered about the receiver trying to walk over the index pin on tightening. Maybe its a problem, maybe not. Unfortunately a couple dudes in their garages may go a life time without finding a problem in a design. So maybe its not a problem. Out of battery tends to be a very destructive.
It isn't just an isolated issue within Compass lake and their products. The problem with the reaction rods is they don't support the receiver so when the barrel nut is being torqued on, the receiver can shift and leaves the pin to take all the torque. I've also seen it before when people just tried to use a barrel vice and I'm sure others have back in the day as well.
While I wouldn't really call it a wide spread issue, it's been happening for a couple years now and there have been multiple reports of the index pin shearing off when using a reaction rod. Some people have also claimed that they had extensions loosen up (which may or may not have been torqued to the proper 150 ft-lb or whatever) and some claims of the index pin shearing when changing muzzle devices.
It may be possible that some user error can be called into play in some of those instances but the use of reaction rods has caused quite a number of issues over the years and there's probably more than people would want to admit publicly on a forum or just in general.
While I wouldn't really call it a wide spread issue, it's been happening for a couple years now and there have been multiple reports of the index pin shearing off when using a reaction rod. Some people have also claimed that they had extensions loosen up (which may or may not have been torqued to the proper 150 ft-lb or whatever) and some claims of the index pin shearing when changing muzzle devices.
It may be possible that some user error can be called into play in some of those instances but the use of reaction rods has caused quite a number of issues over the years and there's probably more than people would want to admit publicly on a forum or just in general.
He said it all, this is what you need to do. Clamshells work well and don't put stress on any one critical location. The part that replaces the bolt is supposed to help. URX4 tubes go on with between 120 and 180 (IIRC) torque. The tube is the barrel nut, it's one piece. Still, no problems. And I recently had one that went all the way up to the max in order to line up the gas tube.
I wouldn't use the ones you pictured though, those takedown pins holes on the receiver aren't that strong. Another way to do it without the clamshell OR the other one is to take two pieces of wood (I use thick plywood) and cut one to fit between the lugs, and another to cover the top rails. You can also put a piece of leather between the upper and the wood. Lock this down in a vice. It won't move, it won't damage the lower and you can torque the barrel to spec without any worry. This was the only way to build an AR10 for a long time and I suspect may still do it today. If you aren't gonna build a lot, this is probably the way to go. Just be careful not to tighten the vice TOO much. Just snug enough it doesn't move when you use the wrench.
A reaction rod is THE way to go for muzzle devices. Why weren't those out sooner? Geissele made mine. KAC sells ones for their rifles too, so be sure you get the right one --KAC barrel extension is proprietary. They're costly, so if you only need it once and know someone with one close by or can meet up with a member here, that may be the way to go.
Good luck!
Please critique my method for AR barrel installs, I am not a gunsmith although do my own barrel installs on bolt action of my own starting with a blank, not a savage style install. I put the AR barrel in a barrel vise and then tighten the barrel nut using a standard armorers wrench. Having the barrel in the vise reduces any torque applied to just that supported by the shear force on the barrel indexing pin.
I find the argument that one method will tend to shear the indexing pin as strange because if you apply the same torque to the armorers wrench the shear forces on the pin will be equal as that is the only component on the barrel that is keeping the barrel from rotating with respect to the upper receiver. Please prove me wrong on my argument about the shear force, when I do the engineering statics analysis on the torques and forces involved I find no difference in the shear forces on the indexing pin.
Thanks
wade
I find the argument that one method will tend to shear the indexing pin as strange because if you apply the same torque to the armorers wrench the shear forces on the pin will be equal as that is the only component on the barrel that is keeping the barrel from rotating with respect to the upper receiver. Please prove me wrong on my argument about the shear force, when I do the engineering statics analysis on the torques and forces involved I find no difference in the shear forces on the indexing pin.
Thanks
wade
the forces applied are the same....where they are applied is not.
when you hold the action.....there is no force being applied on the barrel at all........you are holding the action and you are screwing a nut to the threads on the action.
when you hold the barrel......force is being applied to the pin......as you tighten the barrel nut, its is going to rotate the action in the same direction you are tightening, and since the barrel is fixed in place, thats where the force on the pin comes from
Either way there is force applied to the front of the barrel extension so there is force on everything.
I've tried a lot of methods. For flat tops, I like the clamps that grab the Picatinny rail because there is a pretty good bit of aluminum connecting the front of the rail to the receiver snout.
I just got a BEV block to try out. I like the concept but I wish they were adjustable so the barrel extension and upper were equally supported. I might jam in a feeler gague to accomplish the same thing.
I think a reaction rod with a fin to engage the charging handle slot might be even better than the BEV block but adjustable for equal support would be good there also.
I've tried a lot of methods. For flat tops, I like the clamps that grab the Picatinny rail because there is a pretty good bit of aluminum connecting the front of the rail to the receiver snout.
I just got a BEV block to try out. I like the concept but I wish they were adjustable so the barrel extension and upper were equally supported. I might jam in a feeler gague to accomplish the same thing.
I think a reaction rod with a fin to engage the charging handle slot might be even better than the BEV block but adjustable for equal support would be good there also.
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