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Are there any issues with tightening the barrel nut with the barrel clamped and the upper floating
as opposed to clamping the upper and tightening the nut?
Thanks
Not sure if I understand your question...you're asking if you can do it backwards? Standard procedure is using a vice, block for receiver, secure receiver in block, tighten vice, then tighten barrel nut to spec (30-80ftlbs) while aligning holes for gas tube. That's the way I do it, never tried to clamp the barrel and tighten...
It wont work. Go into your kitchen and try screwing the top onto a jar without holding the jar itself. See what happens when the lid starts to get tight. That's effectively the same as what you are talking about.
That's the way I do it, never tried to clamp the barrel and tighten...
That's the way I do it also but my upper clamp is on "loan" and I have barrel clamps
Never heard of doing that way so was curious..
Eric,
Wouldn't the indexing pin(?)on the barrel ext that goes in the notch on the upper prevent that?
Wouldn't the indexing pin(?)on the barrel ext that goes in the notch on the upper prevent that?
You don't want all that force on the index pin. It'd gouge the relatively weak notch in the upper or just shear off the pin.
Bad idea.
You don't want all that force on the index pin. It'd gouge the relatively weak notch in the upper or just shear off the pin.
Bad idea.
I was forgetting about the index pin, honestly, but this correct. It's not made to take that much force. Good opportunity to buy a receiver block, maybe? ;)
Are there any issues with tightening the barrel nut with the barrel clamped and the upper floating
as opposed to clamping the upper and tightening the nut?
Thanks
Yes... Don't do it. There is a high probability that you will shear off your index pin.
Not gonna do it.
Thanks!!
I agree with the others, a receiver block is better.
However.....securing the barrel will work as it is even the described method in the army technical manual. I think you'd have to be unlucky to shear the pin - but I'd still advocate a receiver block.
http://i822.photobucket.com/albums/zz143/Kwanger/Capture.jpg
you'll get Al scuffs on the outside of the barrel that will take time to remove.
you'll get Al scuffs on the outside of the barrel that will take time to remove.
That's what handguards are for. But seriously, don't use a barrel clamp if you don't have to.
When I built my FAL, I had to put it together with a barrel vice, since the actual barrel is threaded on. After it was timed correctly I had G1 markings on the barrel from where the cast was made. Made my IMBEL barrel look pretty cool.
oddly enough, it wasn't that long ago that barrel blocks were the only option.
Robb Jensen
09-30-11, 05:51
I wish there was an affordable device to clamp the receiver and the barrel at the same time for barrel nut tightening.
So is the consensus upper receiver clamp the best to use to prevent damage, or is there a better solution?
I've only used upper reciever clamps in the vice, so my knowledge is limited.
So is the consensus upper receiver clamp the best to use to prevent damage, or is there a better solution?
I've only used upper reciever clamps in the vice, so my knowledge is limited.
I'd like to know this too. I would have thought that clamping the barrel was not a good alternative for the reasons noted above. I don't ever want to throw bad information around though.
The barrel clamp (vice jaw barrel blocks) have been used by the military for a long time. I never saw a rifle damaged using them either. I have seen some barrels slightly marked though if that is a concern.
So is the consensus upper receiver clamp the best to use to prevent damage, or is there a better solution?
I've only used upper reciever clamps in the vice, so my knowledge is limited.
The very best solution would be as Robb said above - secure both the receiver and the barrel to stop any possibility of lateral twist of any kind. I am surprised no-one has come out with a handy one piece that can do it all.....guess people think it is probably overkill. You could set something up yourself if you have two vises I guess.
But barring that, the general consensus these days is to use an upper receiver block of some kind (opinions vary on which one...user preference, I personally like the DPMS Panther Claw type). IMO the benefits of using an upper receiver block are that they are generally easier to use than clamping up your barrel when you might require some reasonably heavy torque (at the upper end of the scale 80ft/lbsish), and you've less chance of some sort of marks being left (like aluminum on the barrel which takes a good bit of scrubbing to get off).
I wish there was an affordable device to clamp the receiver and the barrel at the same time for barrel nut tightening.
A fixture with two vises! :D
Robb Jensen
09-30-11, 13:29
A fixture with two vises! :D
I generally use a DPMS claw block and if it requires more than 50ft lbs of torque I install it sideways in the vise with one jaw on the bottom of the block and the other jaw with a bronze vise jaw against the top of the flat top receiver. If an A2 upper requires more than 50ft lbs of torque I use the Brownells clamp type.
A setup that held both the receiver and barrel at the same time wouldn't work.
As the nut is tightened it draws the barrel extension into the reciever, and if both ends are fixed to not move, then the barrel extension cannot seat, yet it will seem to take the proper torque.
Well, right up until you take it out of the jig and the barrel starts to flop around because the extension never fully seated in the upper receiver.
To get the receiver extension to seat using such a device would require gobs of torque more than what is currently called for as either the reciever or barrel has to get closer to the opposite so as to seat, which would potentially also leave linear marks along the barrel equal to the amount of distance the nut pulled the extension into the receiver. Might be 5-10 thousandths, might be 1/2". Just depends on how things were initally set up before any real tightening occurred.
**
In restrospect, having both the receiver and barrel clamped 'could' work without having to fight the draw, if one or the other was on a linear dovetail to allow the pulling together to occur, or the barrel was in an affixment that prevented all rotation but would allow linear slide.
Though any amount of slide via dovetail or otherwise will eventually translate into rotational movement regardless as clearances are taken up during torque and/or the jig starts to wear from use.
WAY too tedious a device to design and build, and would likely cost about 136 times more than it could ever possibly be worth even on a level of volume associated with factory manufacturing production let alone someone sitting at home building thousands less than that a year.
I agree with the others, a receiver block is better.
However.....securing the barrel will work as it is even the described method in the army technical manual. I think you'd have to be unlucky to shear the pin - but I'd still advocate a receiver block.
http://i822.photobucket.com/albums/zz143/Kwanger/Capture.jpg
THIS will work. This is the way I've done them since my first build/assembly in the late 80's. The military manual was all I had. The later builds have all been pre-assembled uppers. Although I do now own a receiver block, I have never used it. I agree the receiver block is probably the BEST way to go but the old school method in the mil manual will work fine. Also someone mentioned aluminum scuff marks on the barrel when you're done--take some steel wool and WD40 to it--20 seconds and you're done.
Also someone mentioned aluminum scuff marks on the barrel when you're done--take some steel wool and WD40 to it--20 seconds and you're done.
Or just wrap the barrel in a bit of leather or rubber inner tube when clamping it in the blocks and not create the scuffs to begin with.
oddly enough, it wasn't that long ago that barrel blocks were the only option.
+ 1 Used them for many years before they came out with the "clamshells" for the receiver. I used rosin and a thin sheet of lead to wrap the barrel and prevent slipping. It was also easier to clean up afterward.
Now the clamshells do not work on all recievers because the manufacturers have changed their outside dimensions. On the "odd shaped" receivers, I use a AR-15/M16 BARREL EXTENSION TORQUE TOOL from Brownells.
Brownells also has barrel vise jaws that are lined with polyurethane elastomer in order to grip tight and prevent marring. (I know the OP already owns his vise jaws and is not looking to buy a new set)
I did one with the barrel blocks only, way back when - and did not have any issues. But I think it timed to the gas block hole without a lot of force. Might make a difference.
I use a receiver block now.
Brownells also has barrel vise jaws that are lined with polyurethane elastomer in order to grip tight and prevent marring. (I know the OP already owns his vise jaws and is not looking to buy a new set)
These new lined barrel blocks will not clamp onto a light-weight barrel. Even the small groove side is too large. The old all-aluminum version works though.
Thanks, never tried the new blocks.
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