My SLR, some thoughts...

[scourge18a]

You bet and it works fine. I just set the two set screws that push down to the bottom of the receiver out slightly and its all good to go. Wouldnt be a big deal to take a file to the edges of the triggerbox if you need to clearance a hammer or to get access to adjustment screws.

Did you get the safety in fine?

 

[Robmcleod82]

yep safety was no issue. I tried to put a hyperfire in another one but i couldnt get the safety to go without taking about an 1/8" off the trigger and I dont think the safety would have functioned if i did that.

 

[scourge18a]

Thank you Robmcleod82

 

[Murray 3-D]

Yaaaaaah, after reading all the opinions I think I'll just stick with clamping upper in soft jaws and torquing by hand with a AR wrench. KISS concept.

 

[scourge18a]

Yaaaaaah, after reading all the opinions I think I'll just stick with clamping upper in soft jaws and torquing by hand with a AR wrench. KISS concept.

I used a Magpul BEV block with the BCG in the back end. No issues. This puts most of the torque on the barrel while also holding the receiver via the magwell and BCG.

 

[Shorerider]

Yaaaaaah, after reading all the opinions I think I'll just stick with clamping upper in soft jaws and torquing by hand with a AR wrench. KISS concept.

Get a reaction rod from TNA cheap insurance

 

[Lip]

I used the TNA "Reaction Style-Rod" it did the trick!

https://drive.google.com/folderview?id=1LzGeBJdwxio5hfx9PwocsG7tE6hGAS8u

 

[AB_blaster]

I never use a torque wrench. Tighten, loosen, tighten, loosen, tighten, you'll feel it when it doesn't want to go any tighter then you just give it enough to line up the barrel nut to allow the gas tube to pass through into the receiver.
There are torque specs for the barrel nut, use the a torque wrench and do it properly.
Plus I doubt that most on here that do use a torque wrench are doing the calculations needed to adjust the torque setting on their wrench correctly to compensate for the extra leverage given by attaching to the armourers wrench 2 inches from the nut center. Increasing the leverage given to the wrench changes what it's actually delivering to the nut for torque so they're probably not tightening to the correct spec anyway (they would be over tightening with the increased leverage).
If you install the torque wrench perpendicular to the barrel nut wrench you don't need to make any adjustments as you haven't increased the length of the arm.
Assembling an AR or ARish rifle is quite easy and doesn't require magical skills but you should use the right tools which includes properly holding the receiver or barrel while tightening the barrel nut. Without the right tools you risk not only scratching it but breaking the thin aluminum receiver that was not designed to absorb torque stresses or be crushed in a vise.
Right, so use a torque wrench and do it properly.
I like the reaction rod because no torque is transmitted to the receiver body, it all goes through the barrel extension.
I've also got a tool that can be clamped into a vise that has a side to hold a pic rail and the other side can grab an upper by the takedown pin holes but I use that to hold the receiver during small parts assembly not barrel nut torquing.

If you don't have the right tools and can't borrow them then at minimum don't put the receiver in a vise but instead use a couple blocks of wood to make a barrel clamp and put the barrel in the vise when you tighten the barrel nut. At least this way you won't risk damaging the delicate receiver.

Good luck everyone and if anyone in the Edmonton area need access to the right tools PM me and I can help you out.



No flames from me, just trying to educate and help the inexperienced.

In Red

I have to dispute this very common perception.

With the AR-15 type design, the barrel nut is torqued onto the upper receiver. The flange of the barrel nut is simply sandwiched in between those two parts, with its position indexed by a single pin that engages the upper receiver.

The key is that first statement, the nut is torqued onto the upper. The upper must experience torque. The nut must experience torque. Any attempt to support the assembly via the barrel extension means that all that torque is transmitted through the index pin. Reaction rods and barrel clamps fall into this category. Do it if you must, but do not purport it to be a preferred arrangement.

The best arrangement is to support the upper directly, and torque the nut directly, and then no torque will go through anything else.

The milspec proper method is to clamp the barrel. I guess Bill Geissele is a moron as is Knights armament, both of which offer and recommend a reaction rod for assembling AR's.

Pretty sure I've read that the standard military practice is to use a barrel clamp. I could be wrong though, I'm not a trained armourer.

Right.

Yeah. reaction rod torqueing presses 80 ft-lb of torque through the 1mm diameter barrel index pin into the pin recess in your barrel nut threads:

I would much rather use simple upper blocks, or an upper clamp in a vice, the force of torqueing is spread over a much larger surface area.

Reaction rods indeed the right tool to secure a barrel to a barrel extension, or to install muzzle devices. But very few people buy AR barrels and barrel extensions separately.

The reaction rod is not for attaching barrel extensions, it is for installing handguards and barrel nuts. Again, you must think Bill Geissele is a moron as is Knights Armament. The clamshell is average at best for torquing the barrel nut, and the value is between 35-80 ft/lbs. You don't need to reach the top end of the limit.

This is 100% correct. The clam shell style upper receiver action block is about th best way for uppers that conform the milspec shape. Unfortunately billet uppers usually don’t fit. The two CF armours I know both use Giessele reaction rods, so while not 100% the correct way to do it, it seems to be a much more convenient way with a extremely small potential for damaging the upper.

Clamshell is average. Reaction rods are far better.

You're also likely to shear the index pin off your barrel using a reaction rod to torque a barrel nut.

The reaction rod is just not the right tool to torque a barrel nut.

And again, wrong. Please contact Geissele and tell them they have no idea what they're doing with regards to their reaction rod.

Y’all wild, I thought it was min 35ft/lb and do not exceed 80ft/lb, pffft! I R mechanic I could do 35 pounds by hand! We’re not torque turning heads bolts here fellas! It’s not rocket appliances! Just dont forget the lube!

Correct

Yaaaaaah, after reading all the opinions I think I'll just stick with clamping upper in soft jaws and torquing by hand with a AR wrench. KISS concept.

Don't half ass it with a bench vise. The reaction rod is the ticket and works just fine.

For those who don't know this is Bill Geissele and his reaction rod. Pay attention to 1:40 and on in the video. Bill is an engineer so don't waste my time with "he doesn't know what he's talking about." Yes he does..
https://www.youtube.com/watch?v=nmnN_1UBnAA

Here's brownells version of the reaction rod. Listen carefully to the description, it is NOT for barrel extensions, it is a barrel extension torque tool. In the video below they are installing a barrel nut for a free float handguard.
https://www.youtube.com/watch?v=n4Y_JrfDcXU

 

[BattleRife]

The milspec proper method is to clamp the barrel. I guess Bill Geissele is a moron as is Knights armament, both of which offer and recommend a reaction rod for assembling AR's.

The reaction rod is not for attaching barrel extensions, it is for installing handguards and barrel nuts. Again, you must think Bill Geissele is a moron as is Knights Armament. The clamshell is average at best for torquing the barrel nut, and the value is between 35-80 ft/lbs. You don't need to reach the top end of the limit.


Clamshell is average. Reaction rods are far better.

I did not say anybody was a moron, you are putting words in people's mouths.

Yes, the US armourer manuals recommend a barrel clamp, and yes this results in the same satisfactory-but-less-than-ideal situation as the reaction rod: torque gets transmitted through the index pin. It works, but requires more care and has greater potential for damage than the receiver clamshell. With care a reaction rod can work as well as a clamshell receiver block for barrel nuts, and it's more versatile for other uses. This is the advantage. But for barrel nuts alone, a reaction rod is not a better tool.

 

[griffin86]

I did not say anybody was a moron, you are putting words in people's mouths.

Yes, the US armourer manuals recommend a barrel clamp, and yes this results in the same satisfactory-but-less-than-ideal situation as the reaction rod: torque gets transmitted through the index pin. It works, but requires more care and has greater potential for damage than the receiver clamshell. With care a reaction rod can work as well as a clamshell receiver block for barrel nuts, and it's more versatile for other uses. This is the advantage. But for barrel nuts alone, a reaction rod is not a better tool.

If I put say 45 ft lbs of torque on the barrel nut using a reaction rod, how much torque do you think there is on the index pin?

 

[AB_blaster]

I did not say anybody was a moron, you are putting words in people's mouths.

Yes, the US armourer manuals recommend a barrel clamp, and yes this results in the same satisfactory-but-less-than-ideal situation as the reaction rod: torque gets transmitted through the index pin. It works, but requires more care and has greater potential for damage than the receiver clamshell. With care a reaction rod can work as well as a clamshell receiver block for barrel nuts, and it's more versatile for other uses. This is the advantage. But for barrel nuts alone, a reaction rod is not a better tool.

Watch the video and LISTEN. There is no torque on the index pin. 35-80 ft/lbs is the spec, clearly more torque may result in damage. Pretty sure Bill Geissele knows a lot more about mechanics and the reaction rod than you do. The clamshell is far from ideal as there is most definitely torque being introduced to the aluminum receiver.

 

[griffin86]

Any engineers want to chime in? It’s been 12 years since I was in engineering.


Shear strength of 8620 steel 95,000 psi
Index pin diameter 0.125”

Single shear formula t=F/A

F=(95000•(Pi•0.0625^2)

F= 1165lbs is force to shear 0.125” index pin

Diameter of barrel extension 1.200”
Torque t=rFsin@

t=(.6/12)•1165•1

t=58 ft lbs of torque to shear index pin


So it appears that it takes 58 ft lbs to shear off the index pin. But why do they recommend up to 80 ft lbs to torque the barrel nut?


The friction between the barrel extension and receiver. When you torque a bolt it creates axial force.

t=FKd

t=torque
F=force
K=0.2=constant
d=1.475=diameter of barrel extension thread

F=80/(0.2•1.475/12)
F=3265 lb of force against the receiver

Coefficent of friction anodized aluminum against steel= 0.22

3265•0.22=718 lbs of friction

t=718•0.2•(1.475/12)

t=18 ft lbs of friction between the shoulder of the barrel extension and receiver.

58 ft lbs to shear the pin and 18 ft lbs of friction is 76 ft lbs max torque. There is still friction between the outside of the barrel extension and upper. So I would say 80 ft lbs is reasonable.


So why are people shearing off the pins? Could be wrong choice of material or mongoloids over torquing the barrel nut. Probably didn’t calculate the extra leverage of the barrel nut tool.

 

[Betty-Lou]

Just out of curiousity, if the barrel isn't threaded why would the barrel twist at all? Other than the friction between the shoulder of the nut and the barrel.

 

[BioPace]

Just out of curiousity, if the barrel isn't threaded why would the barrel twist at all? Other than the friction between the shoulder of the nut and the barrel.

I sat with an upper in my hands and a barrel nut and that is all i could come up with - so if the binding parts are all greased and the grease retains its slipperiness at whatever load is generated with 45ft/lbs of torque on teh barrel nut then there shouldn't be any load on the pin or its notch...

But i am not an engineer or AR15 armourer so :shrugs:.

 

[Betty-Lou]

Also, why do they call it an index pin and not an anti rotation pin?

 

[griffin86]

Also, why do they call it an index pin and not an anti rotation pin?

To index the gas port and barrel extension.

 

[Sqr]

Yeah. reaction rod torqueing presses 80 ft-lb of torque through the 1mm diameter barrel index pin into the pin recess in your barrel nut threads:

I would much rather use simple upper blocks, or an upper clamp in a vice, the force of torqueing is spread over a much larger surface area.

Reaction rods indeed the right tool to secure a barrel to a barrel extension, or to install muzzle devices. But very few people buy AR barrels and barrel extensions separately.

I have seen extension pins broken and lose extensions from careless use of reaction rods. That being said impatient wrenches have damaged many builds even with the proper tools.

 

[ThatM305Guy]

Loving this discussion....
Only thing I can think to chime in is this:

The mating threads are on the action, not the barrel extension. Using a "Clamshell" or other device to hold the ACTION from rotating is counter acting the torque applied to the threads. At this point there is still a small amount of force being applied to the barrel and barrel extension. Though there is some due purely to friction between the mating faces. However with a little dab of grease applied to mating faces of the barrel nut/extension, you would pretty much eliminate that entirely.

Using a reaction rod holds the barrel firmly, however as the majority of the force/torque/twisting is being applied to the receiver via the mating threads, you are in effect relying on the index pin to withstand all the force being applied.

Remember the barrel is not what you are applying torque to, it's the receiver. The force you are applying is going into the threads, not into the sliding fit of the barrel/pin. Therefore leaving the action unheld/unsupported, means that literally the only thing holding the action from rotating with the force applied, is the index pin.

Just my 2 cents.

**Edited for better clarity of my thoughts.**

 

[Dr. Hunter]

Damn didn't realize AB blaster / Wyatt got banned.

 

[griffin86]

Damn didn't realize AB blaster / Wyatt got banned.

I noticed the SLR threads were a lot less combative. It was worth getting an infraction.