View Full Version : Lower flex when torquing buffer tube
Hi all, I just finished up my SHTF SBR and I had a couple of questions. I used a bev block in the magwell and the lower receiver (Aero M4E1 Liberty) flexed A LOT when torquing the castle nut to 40#. I stopped cranking when I noticed and used my leg against the buffer tube to provide more support and then torqued it to 40# without any obvious issue. The buffer tube is straight, the lower looks straight and I can't visually detect any cracks or anything...
I know Colt has some proprietary alignment jig they use, but am wondering if that kind of flex is ok. I'm guessing not.
My two questions are:
1. Do I need to be concerned with any damage or weakening of my lower receiver from the flex? I had already installed the trigger etc. as well, could there be issues with the parts or the pin holes in the lower?
2. Is there a better way to do this?
Not only does this lower have my SBR stamp but it's also a limited run from last July 4th with a really pretty "Liberty" shield rather than the usual Aero logo, so I'm very concerned about having damaged or weakened it in a way I lack the expertise to notice.
Thank you!
And yes I searched.
Yeah I wouldn’t twist a receiver like that.
I hold the tube by the rail in a vice, and hold the receiver from spinning by holding it a big adjustable wrench on the flat that goes into the grip.
I torque to about 30#, lubed with oil, stake in two slots.
It’s not to spec, but I’ve never had one come loose in years of building some high round count lowers.
Yeah I wouldn’t twist a receiver like that.
I hold the tube by the rail in a vice, and hold the receiver from spinning by holding it a big adjustable wrench on the flat that goes into the grip.
I torque to about 30#, lubed with oil, stake in two slots.
It’s not to spec, but I’ve never had one come loose in years of building some high round count lowers.
Thank you for the response!
That sounds like a great way to install it. I'd rather damage a buffer tube than my lower receiver.
I didn't lube the threads, though it likely had some CLP on it.
I plan on staking it after i do a function test. Do you think it would be advisable to reinstall the buffer tube?
Is there any kind of metal fatigue or anything I should be concerned with?
Yeah I wouldn’t twist a receiver like that.
I hold the tube by the rail in a vice, and hold the receiver from spinning by holding it a big adjustable wrench on the flat that goes into the grip.
I torque to about 30#, lubed with oil, stake in two slots.
It’s not to spec, but I’ve never had one come loose in years of building some high round count lowers.
Ive installed thousands of buffer tubes using a receiver block and then a reaction block. Some twist can occur but its never been an issue. I also lube the threads with anti-seize
Ive installed thousands of buffer tubes using a receiver block and then a reaction block. Some twist can occur but its never been an issue. I also lube the threads with anti-seize
Did the receiver block utilize the magwell?
Thank you for the response!
That sounds like a great way to install it. I'd rather damage a buffer tube than my lower receiver.
I didn't lube the threads, though it likely had some CLP on it.
I plan on staking it after i do a function test. Do you think it would be advisable to reinstall the buffer tube?
Is there any kind of metal fatigue or anything I should be concerned with?
I think it’s ok. The castle nut is just a jam nut to keep the tube from being loose. It doesn’t do a whole lot. 40 ft/lbs is way overkill IMO.
7075 is tough, I highly doubt you hurt anything.
Did the receiver block utilize the magwell?
Yes, its an old brownells one. The reaction block is pretty kickass but having to slide the wrench on prior to insertion then use the grip instead of a stock to apply back pressure is a pain in the ass.
Thanks for the input. I'm definitely a perfectionist so the knowledge is appreciated!
fwiw I spoke with geissele and they stated they torque to 40#, as does Daniel Defense.
40 ft/lbs is way overkill IMO.
That torque is what keeps reasonable knocks on the stock from twisting the receiver extension. Staking and bump on the end plate are not strong enough by themselves.
I'm lazy, I install a pistol grip, then stand on it or put it in a vise so that there is as little room for movement when locking the castle nut in place.
I'm lazy, I install a pistol grip, then stand on it or put it in a vise so that there is as little room for movement when locking the castle nut in place.
This. Just snug it down to the exact spec of "pretty damned tight" and stake it. I've NEVER dragged out the torque wrench for this.
Thanks for all the responses guys!
1_click_off
09-04-21, 06:01
I usually pin the upper on it so it has some more support while tightening it. I guess you could even throw a old BCG in there to offer even more support.
bamashooter
09-04-21, 06:29
No doubt I've never taken one to 40 or staked any. Better to flex than to shatter.
I usually pin the upper on it so it has some more support while tightening it. I guess you could even throw a old BCG in there to offer even more support.
:blink: That wouldn't help in the least.
There should be no problem with going to the correct 38-42 Ft-Lb torque spec and there should be minimal flexing of the lower IF the lower is supported correctly. However, there is nothing correct about using a mag well vise block for the task... Those are merely to be used as a third hand to aid in installing things like triggers, mag catches, pistol grips and pivot pins.
What fixtures do you recommend for proper support?
What fixtures do you recommend for proper support?
Well, if you don't have access to Colt's proprietary jigs (which none of us do), then I recommend doing it in a similar fashion as listed in the TM.
http://i.imgur.com/iNpsHPzm.jpg
http://i.imgur.com/26MqnyOm.jpg
http://i.imgur.com/UMHsrwnm.jpg
What fixtures do you recommend for proper support?
https://geissele.com/reaction-block-ar15-m4-mil-spec-buffer-tube-only.html
https://geissele.com/reaction-block-ar15-m4-mil-spec-buffer-tube-only.html
I have one and I can't recommend it as it allows the lower to rotate while applying torque to the castle nut.
It's good for holding the lower while staking the castle nut though. However, I've been having mixed results with staking endplates lately, the heat treat is too hard on a lot of them, even the ones I've been getting through Colt. So instead of a nice little staking dimple I get the end plate warping and pushing down between the castle nut and the lower receiver.
1_click_off
09-04-21, 10:58
:blink: That wouldn't help in the least.
Why wouldn’t it? Help overall stiffness and the lower is making contact with the upper around the RE. So how does this not help in the least? Not arguing, just curious. I may be thinking about it too much.
You have to hold the tube and the receiver. Whatever Colt uses still allows them to get the tube torqed the right side of the notch. I can do better holding the tube by the rail and backing it up with an adjustable wrench on the grip flat.
I thought I was losing my touch, but I have noticed that end plates are too hard lately. I had to resort to using a sharp 5/32” center punch to get the stake started and then a rounded off one to get enough metal moved and look nice.
ViniVidivici
09-04-21, 14:47
In before the inevitable "ah never stake 'em, an' alwaiz use loctite, an' ain't never had a problem" response.
Ah. I have it but haven’t actually used it.
Anyway:
Stake your nuts and pin your blocks. That’s my story.
In before the inevitable "ah never stake 'em, an' alwaiz use loctite, an' ain't never had a problem" response.
Well in their defense they won’t have a problem until there is a problem and then it’s usually my problem because the upper is stuck on the lower and the BCG is halfway back so you end up cooking the thing with a heat gun trying to unlock the Locktite without burning the receivers with a torch so the whole thing can be disassembled to remove the primer that’s clogging the whole thing up. Or so I’ve heard.
You have to hold the tube and the receiver. Whatever Colt uses still allows them to get the tube torqed the right side of the notch. I can do better holding the tube by the rail and backing it up with an adjustable wrench on the grip flat.
I thought I was losing my touch, but I have noticed that end plates are too hard lately. I had to resort to using a sharp 5/32” center punch to get the stake started and then a rounded off one to get enough metal moved and look nice.
Hmmm, I never saw a Colt RE that wasn't in near perfect alignment with the lower. Maybe they retired their fancy jig with all the more recent crap going on over the last few years... I'd hate if that were the case, but I wouldn't doubt it.
And I'm glad you noticed the overly hard end plates too! I actually just recently sent my torque wrenches into Snap-On to be recalibrated because I thought that maybe they were out of calibration and were under torqueing the castle nuts, causing the end plates to not be secure enough to handle the staking. Turns out they were fine, but it cost me about $260 for unneeded overhaul/recalibration and recertification on the wrenches. Now that Colt's endplates are suspect I really have no idea where to find end plates of the proper hardness for a quality staking job???
Why wouldn’t it? Help overall stiffness and the lower is making contact with the upper around the RE. So how does this not help in the least? Not arguing, just curious. I may be thinking about it too much.
The upper is basically just floating on top of the lower and being retained by the takedown and pivot pins, I'm trying to envision a way in which it might be offering any support to the lower when torqueing a castle nut while the lower is being held by a mag well vise block, but I'm coming up empty?
titsonritz
09-06-21, 19:20
Yes, its an old brownells one. The reaction block is pretty kickass but having to slide the wrench on prior to insertion then use the grip instead of a stock to apply back pressure is a pain in the ass.
That is my only complaint about Magpul's wrench, Midwest Industries armorer's wrench solved that issue. Prior to that I would use BCM barrel nut wrench.
Or use the PWS ratcheting castle nut set up. Finger tight then two clicks past that and Bob's your Uncle. (puts on nomex suit to shield from the purists)
the AR-15 Junkie
09-08-21, 21:51
Here ya go.
https://i.imgur.com/HCXsyRt.jpg
Here ya go.
https://i.imgur.com/HCXsyRt.jpg
Now that's similar to what the Geissele Reaction Block should have been... But Geissele tools always leave out half of the equation.
Or use the PWS ratcheting castle nut set up. Finger tight then two clicks past that and Bob's your Uncle. (puts on nomex suit to shield from the purists)
I actually like this idea. I have one that came on a PWS rifle, and I honestly can't fault it. Not entirely sure it's needed, in the sense that once the extension is attached, it's attached. But it sure makes it easy to have a secure castle nut without having to stake.
Am actually ordering another to complete a pistol lower I'm building, to go with their mk111 upper I've got coming.
I actually like this idea. I have one that came on a PWS rifle, and I honestly can't fault it. Not entirely sure it's needed, in the sense that once the extension is attached, it's attached. But it sure makes it easy to have a secure castle nut without having to stake.
Am actually ordering another to complete a pistol lower I'm building, to go with their mk111 upper I've got coming.
I do like them. I started using the old design many years back and it was lacking. It was machined into the RE and had 3 set screws which just made it a pain. But when they came out with this new design? Winner. BDU usually sells them for 20 bucks give or take. They're on all my rifles now.
I thought the castle nut torque spec was 40 INCH-pounds, not 40 ft-lbs.
ETA: Copy of page from ARMY TM 9-1005-319-23&P
66418
The rifle extension is 35-39 ft-lbs. The carbine castle nut/locking ring is 40 in-lbs.
I thought the castle nut torque spec was 40 INCH-pounds, not 40 ft-lbs.
ETA: Copy of page from ARMY TM 9-1005-319-23&P
66418
The rifle extension is 35-39 ft-lbs. The carbine castle nut/locking ring is 40 in-lbs.
Well known typo.
Well known typo.
Thanks. Well that's what I get for not just using German specifications. Hope my carbines don't lose their extensions.
titsonritz
09-09-21, 22:10
I thought the castle nut torque spec was 40 INCH-pounds, not 40 ft-lbs.
ETA: Copy of page from ARMY TM 9-1005-319-23&P
66418
The rifle extension is 35-39 ft-lbs. The carbine castle nut/locking ring is 40 in-lbs.
That is an old manual and a mistake. 40 inch pounds = 3.33333 foot pounds, think about it.
Thanks. Well that's what I get for not just using German specifications. Hope my carbines don't lose their extensions.
If you used 40 inch pounds you really need to re-torque and re-stake.
That is an old manual and a mistake. 40 inch pounds = 3.33333 foot pounds, think about it.
Well I'm old (and likely a mistake). :D
When I started assembling AR carbines the available locking ring wrenches (pre castle nut) were about 4 or 5 inches long:
66419
So a greatly reduced torque value vs a rifle extension didn't seem outlandish. I used more than 3.33 ft-lbs, but no where near 40 ft-lbs.
I learned something today, so I'll fix it.
I use the Gorilla Method. No torque wrench. Just an armorer's wrench (pipe wrench works in a pinch too) and I keep putting pressure on it until I grunt like a Gorilla. Or the wrench slips. It's fun for the whole family. Oh and definitely drink at least a 12 pack of Old Milwaukee before attempting this. It helps with lubrication. The more you know.......
Someone should make a polymer brace like the one that lines up the receiver extension with the pistol grip. If they swung the polymer forward a bit, they could also have a surface for clamping the middle of the receiver in a vice.
Robertthetexan pointed to plastixrevolution for some good products, I wonder if they could put this together.
Essentially, drop the receiver “down and back” into the jig, then slide the receiver extension forward into the end plate/castle nut and then receiver.
Here ya go.
https://i.imgur.com/HCXsyRt.jpgi wonder if something could be rigged with the Geissele buffer tube tool jig, add on some steel parts to extend to the pistol grip boss. like somebody said, the Geissele jig is only half the equation. so that the whole thing could be clamped in a vise.
I’m going to reiterate the preference for a strong polymer here. At scale, we wouldn’t be faced with Geissele + aluminum prices for something that could be effectively printed.
Hammer_Man
09-20-21, 07:01
The receiver was probably flexing like crazy because you didn’t lube the threads. Lube the threads of the RE, and receiver with Aero Shell, and torque to 40 ft. lbs.
50 bucks - Kley-Zion Buffer Tube Buddy - it works
99cobra2881
09-20-21, 14:46
The receiver was probably flexing like crazy because you didn’t lube the threads. Lube the threads of the RE, and receiver with Aero Shell, and torque to 40 ft. lbs.
Is the torque spec in the manual for lubricated threads versus dry?
IME, lubed fasteners will be overtorqued by the time the tq wrench clicks.
Thats my engine building experience where the tq specs are for dry non lubed fasteners.
I understand this is not an apples to apples comparison but the fastener being torqued doesnt care and neither does the tq wrench.
Is the torque spec in the manual for lubricated threads versus dry?
IME, lubed fasteners will be overtorqued by the time the tq wrench clicks.
Thats my engine building experience where the tq specs are for dry non lubed fasteners.
I understand this is not an apples to apples comparison but the fastener being torqued doesnt care and neither does the tq wrench.
Yes, the torque spec in the TM is for lubed threads. Barrel nuts, rifle receiver extensions and castle nuts all get lube.
Hammer_Man
09-22-21, 14:03
Is the torque spec in the manual for lubricated threads versus dry?
IME, lubed fasteners will be overtorqued by the time the tq wrench clicks.
Thats my engine building experience where the tq specs are for dry non lubed fasteners.
I understand this is not an apples to apples comparison but the fastener being torqued doesnt care and neither does the tq wrench.
Yes, the torque spec in the TM is for lubed threads. Barrel nuts, rifle receiver extensions and castle nuts all get lube.
The TM specifies lubricating the threads with Aero Shell 64 grease. To answer your other question, yes there will be a difference in final torque when it comes to lubed vs. non lubed. That’s why it’s important to know if the manufacturer specifies lube or not.
In regards to the receiver extension, it’s very much the same situation as the barrel nut. You’re torquing a steel nut onto an aluminum component. Without lube, these two metals create friction and you run a high chance of stripping or galling the threads.
If any of you happen to have a 3D printer or access to one, there are some excellent models online for buffer tube vise blocks that you can print. I just printed one and used it to torque the castle nut on, and I was honestly surprised at how perfectly the buffer tube fit inside the block and at how sturdy it was. Well worth the ~$2 in plastic it cost to print.
Deadman William
10-12-21, 15:23
Here ya go.
https://i.imgur.com/HCXsyRt.jpg
i don't know what this is, but it looks like it clamps the receiver extension - rather than the receiver - in the vise, and this is correct... or at least what i've always thought was correct. i surprisingly don't see (perhaps i missed it?) anyone mentioning that the receiver extension is the part you clamp when tightening the nut, not the receiver - as the OP has observed, that unduly twists the receiver. obviously not something you want to do on an NFA receiver.
i have two bored out wooden blocks i use to clamp the receiver extension whilst tightening the nut. and i've also never torque-wrenched it... a good hard snug up is all you need. i'm pretty surte the only AR parts i've ever bothered to break out a torque wrench for are barrel nuts.
as to end plates not wanting to take a stake - it seems like most plates these days want to crack into the stake notch rather than just nicely, plasticly, forming into the notch, as another poster posted somewhere above. is this a heat treat thing, or have they started MIMing end-plates?
the AR-15 Junkie
10-12-21, 19:54
i don't know what this is, but it looks like it clamps the receiver extension - rather than the receiver - in the vise, and this is correct... or at least what i've always thought was correct. i surprisingly don't see (perhaps i missed it?) anyone mentioning that the receiver extension is the part you clamp when tightening the nut, not the receiver - as the OP has observed, that unduly twists the receiver. obviously not something you want to do on an NFA receiver.
i have two bored out wooden blocks i use to clamp the receiver extension whilst tightening the nut. and i've also never torque-wrenched it... a good hard snug up is all you need. i'm pretty surte the only AR parts i've ever bothered to break out a torque wrench for are barrel nuts.
as to end plates not wanting to take a stake - it seems like most plates these days want to crack into the stake notch rather than just nicely, plasticly, forming into the notch, as another poster posted somewhere above. is this a heat treat thing, or have they started MIMing end-plates?
This is or was a prototype. I was told about 2 weeks ago these are in production and I am at the top of the list to get one.
This is or was a prototype. I was told about 2 weeks ago these are in production and I am at the top of the list to get one.
They have a website for ordering?
the AR-15 Junkie
10-13-21, 12:17
They have a website for ordering?
Not yet, this was made by a machinist friend of a local Armorer. I made that pic back in July when the armorer was demonstrating it. Thats all the info I have. I contacted the armorer about 3 weeks ago and all he told me was its in production and I was at the top of the list to get one. If I ever do I will post up ASAP. Its home made in some ones garage shop so who knows. I offered him $200.00 for his, he just laughed.
Not yet, this was made by a machinist friend of a local Armorer. I made that pic back in July when the armorer was demonstrating it. Thats all the info I have. I contacted the armorer about 3 weeks ago and all he told me was its in production and I was at the top of the list to get one. If I ever do I will post up ASAP. Its home made in some ones garage shop so who knows. I offered him $200.00 for his, he just laughed.
Got ya. Definitely keep us posted, the tool looks promising.
for those who don’t want to spend 200 dollars:
50 bucks - Kley-Zion Buffer Tube Buddy - it works
from the website:
KZ AR15/M4 Receiver Extension Buffer Tube Block
Will work with both mil-spec & commercial buffer tubes
Mounts receiver in 12, 3 , 6 or 9 o'clock positions
Two polymer screws firmly holds buffer tube in position.
Mounts in any vice
6061 T6 Aluminum
Clear, Type II class III hard Anodized
Only, 3.5" wide, 6" tall
Lightweight only 11.6oz
Lifetime warranty
100% Made In USA
i have no connection to the company and generally avoid them but this thing does what is asked of it.
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