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Old November 25, 2021, 11:49 AM   #1
kymasabe
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Do upper receiver vise blocks cause damage ?

I recently got another barrel for a new build and sent the barrel seller a pic of the extremely short indexing pin, I need to return the barrel. But in the pic I sent him, he saw my vise block that encloses the upper receiver and told me my block was crap, that receivers twist and deform when tightening the barrel nut and that I should buy a Magul bev block.
Am wondering how much truth there is to it.
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Old November 25, 2021, 12:53 PM   #2
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I dont use the clam shell type blocks to install barrels. A “action rod” type that locks into the receiver extension should be used. Your smith is correct.
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Old November 25, 2021, 01:16 PM   #3
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Don't know what you kids are doing these days, but 45 years ago when I was installing new barrels in M16A1s, it was THE BARREL that went into the vice blocks, NOT the upper receiver.

I mean, just think about it, when you need to clamp something so it doesn't move, which is better, clamping on a thick walled STEEL tube or a thin walled oddly shaped aluminum one??

I vote for the steel.
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Old November 25, 2021, 01:26 PM   #4
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If you find you needing a lot of force to get the barrel nut to line up, stop. Get shims or lap your receiver and start over. Adding shims or lapping the receiver on ARs is simple enough. If you are using a non-standard handguard or tube, shims or lapping may be a necessity.

I’ve used the BevBlock from the get go, but it mates with the barrel extension, not the receiver itself.
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Old November 25, 2021, 03:58 PM   #5
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They all have their pros and cons.
Action rod / bev block styles, for example, put all the stress of torquing the nut into the barrel extension pin and the tiny bit of aluminum that it engages on the receiver.

I have seen more than one person remove a barrel that was installed with an 'action rod', because they have a gas tube alignment issue that is causing reliability problems, only to find that the pin sheared a piece of the receiver off during installation.


Clam-shell styles *should work fine if they fit properly, especially at the front of the receiver, where there's more meat and better geometry to avoid twisting.
Most, however, don't seem to fit well at all.

*One thing that I have never seen, however, is proof of the clam-shell style actually twisting or damaging a receiver. Many claims. Many unsupported stories about Bob's uncle's gunsmith's buddy's girlfriend's armorer's roommate.
Never any proof.
If your gunsmith wants to claim that your tools are known for damaging or twisting receivers, ask him to back it up. While I do believe clamshells to be a poor choice, there is so much negative talk without any supporting evidence, that I am beginning to qualify it all as Fuddlore.

I have seen photos of pin style vise blocks ripping out the pivot and takedown lugs, but never any evidence to prove clamshells twist or damage receivers.


There is no perfect solution for the AR. You're either putting all the torque through the barrel extension pin, or finding a less than ideal way of holding the thin receiver.
Pick your poison.
Not gonna lie. I've used a picatinny rail vise block to torque more than one barrel nut. Not a good method. But none of them are.
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Old November 25, 2021, 04:16 PM   #6
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But in the pic I sent him, he saw my vise block that encloses the upper receiver and told me my block was crap, that receivers twist and deform when tightening the barrel nut and that I should buy a Magul bev block.
With how much torque?

I use a clamshell and like to end up with 80 ft lbs or a bit better. I've never bent one. I bought a couple of uppers with some odd shapes that don't fit the clamshell, so I'm going to try some wood and leather to clamp the barrel. I'm not optimistic about getting full torque that way.
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Old November 25, 2021, 06:17 PM   #7
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80ft/lbs? Why so much torque?

Is there something that much different about ARs today than the M16A1s I worked on??

30 Ft/lbs was the Army spec (and then tighten to align the barrel nut with the gas tube hole). So, what's so different today that twice that amount of torque is used??
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Old November 25, 2021, 08:26 PM   #8
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It's just the recipe I picked up, but I couldn't justify any of the specifics otherwise.

It's a cycle of tightening and untightening a greases barrel nut three times, getting progressively tighter, and ideally ending with the nut aligning perfectly at 80 ft lbs. I've never broken anything doing this, and when I needed just a but more to make things line up, I've exceeded 80.

I've had a few that I've taken through the cycle more than three times because I couldn't make it work the third time. My theory behind working up to the maximum of the range is that higher poundage may make up for some variation in dimensions that other guys fix by truing the receiver and/or shimming the barrel extension, neither of which I've ever done.

I did just get some shim material to try in the future.

I was impatient about getting to a vise earlier this summer, and put together a 22lr upper on my living room floor. The first surprise was that it showed excellent accuracy. The second surprise was how nearly impossible it was to get unscrewed with my bare hands after testing. Apparently enough 22lr crud had found its way into the threads to tighten things up.
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Old November 25, 2021, 08:52 PM   #9
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I thought barrel nut spec was 30-80 lb torque. I tighten to 30 lb twice, then 30+ on third tightening, but just enough to clock the barrel nut correctly. I seem to get the best accuracy at the lower end of the torque range. If using a free float handguard with a nut that doesn't need to be clocked, I torque them to 50lb.
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Old November 25, 2021, 09:25 PM   #10
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TM 9-1005-249-34

I'm sure you computer savy folks can find it online. It's the shop manual (Direct Support / General support levels) for the M16 the Army used back in the 70s.

That's where I got my torque values.
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Old November 26, 2021, 02:45 AM   #11
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Don't know what you kids are doing these days, but 45 years ago when I was installing new barrels in M16A1s, it was THE BARREL that went into the vice blocks, NOT the upper receiver.

I mean, just think about it, when you need to clamp something so it doesn't move, which is better, clamping on a thick walled STEEL tube or a thin walled oddly shaped aluminum one??
Isn't that the worst thing to do . Think about it You have a threaded bit ( the receiver ) and a nut . You need both to be secured in order to tighten one to the other . In all actuality the barrel is irrelevant really . If you "only" clamp the barrel what is stopping the receiver from turning/spinning as you torque the nut down ? Don't you dare say the alignment pin . That "steel" pin being forced HARD against the soft aluminum should put the barrel out of alignment with the receiver . That's not good if using a pinned front sight base that utilizes flats on the bottom of the barrel for it's alignment to the gas port and that little pin on the extension . Not to mention if the barrel has M4 feed ramps because they to need to line up with the feed ramp cut outs in the receiver as well .



So I'd say you need the receiver clamped down and the barrel free floating for proper alignment .

FWIW I use the upper receiver vise clamp all the time OK not all the time but still haha . I put the bolt carrier with bolt removed inside the receiver to be sure not to deform the receiver when clamping . That likely helps it from twisting from torque as well . I started doing that when I noticed I could not slide the BCG into the receiver after I clamped it down . This was on the first receiver I ever clamped down and it told me I was squishing the receiver and likely bending/deforming it . They make a special insert for that purpose but I don't have one yet . I just don't change out barrels often enough to get one but I know I should .
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Old November 26, 2021, 08:31 AM   #12
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I typically use a reaction rod but regarding vises, I much prefer the PlastXrevolution. It can be use for right hand / left hand guns due to its unique design. Cheap and very effective. Not sure but when I got mine I ordered without the "torque plates". Never saw the need for them and still don't. The kits other than the basic kit include a set of pins for doing light work.

I got their basic model years ago. No plates, no allowance for pins. https://www.plastixrevolution.net/co...ver-vise-block


One example:

https://www.youtube.com/watch?v=-aqrZI0ylN4

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Old November 26, 2021, 11:24 AM   #13
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Originally Posted by Metal god View Post
Isn't that the worst thing to do . Think about it You have a threaded bit ( the receiver ) and a nut . You need both to be secured in order to tighten one to the other . In all actuality the barrel is irrelevant really . If you "only" clamp the barrel what is stopping the receiver from turning/spinning as you torque the nut down ? Don't you dare say the alignment pin . That "steel" pin being forced HARD against the soft aluminum should put the barrel out of alignment with the receiver . That's not good if using a pinned front sight base that utilizes flats on the bottom of the barrel for it's alignment to the gas port and that little pin on the extension . Not to mention if the barrel has M4 feed ramps because they to need to line up with the feed ramp cut outs in the receiver as well .







So I'd say you need the receiver clamped down and the barrel free floating for proper alignment .



FWIW I use the upper receiver vise clamp all the time OK not all the time but still haha . I put the bolt carrier with bolt removed inside the receiver to be sure not to deform the receiver when clamping . That likely helps it from twisting from torque as well . I started doing that when I noticed I could not slide the BCG into the receiver after I clamped it down . This was on the first receiver I ever clamped down and it told me I was squishing the receiver and likely bending/deforming it . They make a special insert for that purpose but I don't have one yet . I just don't change out barrels often enough to get one but I know I should .
I agree. I can't image how clamping the barrel would work for an AR. It is the correct way for other designs with threaded barrel shank, such as Mauser bolt action.

The vise blocks, either the block type or the clamp shell type, are to stop the receiver (aluminum) from turning, so the aluminum is going to take the torque either way. Getting as much aluminum involved as possible is the only way to not damage the receiver. Both types are trying to do that, but in different ways.

Clamp shell is by external friction, same as plumber clamping down a steel pipe. The friction comes from huge clamping force which could collapse the receiver. A mandrel will need to be put inside to keep this from happening.

The block type is by internal reaction force on one side of the receiver opening. There is always a bit of slop and that reaction force is prying on the side of the receiver opening.

Take the poison is the right statement. I take the clamp shell with mandrel. I like its sturdiness and it is the way my instructor taught me.

There is a reason the torque spec is a rather wide range. Tighter doesn't mean better. I never had to shim or lap anything yet. But if I have to lap, I probably will do it on the barrel nut.

-TL

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Old November 26, 2021, 11:52 AM   #14
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If the barrel is held, the turning friction is on the barrel flange. Torque is transferred to the barrel extension lugs and to the tool. Minimal torque is transferred through the thread friction to the pin and the slot in the receiver, proper lube helps.

If you clamp the receiver only then all the torque is transferred to the receiver.

But my opinion is if you don’t apply more force than necessary you won’t damage either way.

Over-torquing things causes much damage in any technical endeavor on and is a common mistake.
Better to tighten something to its minimum specification than to over tighten anything.

As a lifelong technician on expensive machines, I’ve made a fair amount of money repairing things damaged by people over tightening fasteners.
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Old November 26, 2021, 01:15 PM   #15
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Ok, I dug up my old manual.

TM 9-1005-249-34
Department of the Army February 1972
0
Quote:
I can't image how clamping the barrel would work for an AR.
There is a picture on page 19. And it says torque to 30 ft/lbs then tighten to align the nut.

Quote:
If you "only" clamp the barrel what is stopping the receiver from turning/spinning as you torque the nut down ?
Probably the fact that there is no significant force being applied to the upper receiver.

Quote:
Don't you dare say the alignment pin . That "steel" pin being forced HARD against the soft aluminum should put the barrel out of alignment with the receiver .
I dare say it, the alignment pin.
The steel pin isn't being forced anywhere, it does not move when the barrel is correctly secured in the barrel blocks of the vice. And, if not correctly clamped in the vice and the barrel turns in the vice blocks, so does everything, including the upper receiver, which is literally just hanging in space, on the end of the barrel.

As rickyrick correctly observed, the force of the nut turning is being applied to the barrel, NOT the upper receiver. And, 30 ft/lbs (plus a little) is not a lot of force.

I replaced barrels on M16A1s dozens of times, in the Army, using their tools and method, NEVER had any problems with the barrel alignment pin damaging the upper.

I'm not saying you are doing anything wrong, obviously you are using different tools, a different method, and apparently, different torque specs,,,what I'm wondering is why?

I freely admit I haven't built any ARs using current commercial parts since the early 80s, and the ones i did back then were all with "A1" pattern parts. So, what I'm wondering is what, if anything, changed requiring a such a different method of installing the barrel?
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Old November 26, 2021, 01:32 PM   #16
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Probably the fact that there is no significant force being applied to the upper receiver.
Nope , ever torque a nut onto a bolt and at some point the bolt starts turning ?

Quote:
I dare say it, the alignment pin.
The steel pin isn't being forced anywhere, it does not move when the barrel is correctly secured in the barrel blocks of the vice.
Correct . it's the receiver being forced hard against the alignment pin to stop the receiver/bolt from turning . This can indent the receiver misaligning the barrel to the receiver . This is not to say the rifle would be unusable but rather you needing to adjust the rear sight a couple more clicks from center zero then optimal .





Quote:
I freely admit I haven't built any ARs using current commercial parts since the early 80s, and the ones i did back then were all with "A1" pattern parts. So, What I'm wondering is what, if anything, changed requiring a such a different method of installing the barrel?
Easy , they became very popular in the private market and when you take something out of the hands of the government and place it in the private market . Everything about it gets better and more efficient
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Old November 26, 2021, 01:52 PM   #17
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The torque applied to threaded parts is to overcome reaction force from the mating surfaces, not the friction. In other words, even with frictionless threads, the torque is still needed if you want to mate the barrel to the receiver with certain force. The receiver will have to bear the torque, regardless the methods of application. If the barrel is clamped stationary, the torque is indeed transmitted to receiver by the pin, full force minus friction between the nut and barrel.

I don't have the manual, but I believe the info and pictures are there. It doesn't have to always make sense though. Didn't some manual from similar time suggested no cleaning was needed? 30 ft-lb min and torque to align. No max limit? I believe newer spec has max torque.

-TL



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Old November 26, 2021, 02:01 PM   #18
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Maybe the better explanation is what is going on with the reaction point, or more specifically, where that reaction point is.

Some devices put the reaction point at the barrel extension, but clamping the receiver makes the receiver itself the reaction point.

The threads are going to see some force either way. If you damage the threads, then you’ve done something wrong.

The barrel clamp puts the forces in a minimal area instead of into the receiver.
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Old November 26, 2021, 02:12 PM   #19
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The torque is to generate the force to pull the barrel and receiver together. Unless you don't need that force, the torque between the receiver and the barrel nut is always needed. I don't see any way to weasel the receiver out of it.

Just to clarify, the receiver has threads, the barrel nut has threads, the barrel doesn't. There is no way the torque is only between the barrel and the nut, with the receiver being an "spectator".

-TL

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Old November 26, 2021, 03:11 PM   #20
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Quote:
There is no way the torque is only between the barrel and the nut, with the receiver being an "spectator".
By using a tool that reacts on the barrel extension no torque is transferred into the receiver aside from the threaded part of the receiver. There has to be some force on the threads.
If you clamp the receiver, the force is transferred into the receiver beyond the threaded portion up to wherever the reaction point is.

That being said, there’s people that pin the upper and lower together and use an empty magazine for leverage.

A tool that engages the barrel extension keeps all the forces in the area of the fastener only. Other methods transmit the forces to other places... places that may not have been designed to tolerate twisting.

The same reason that you wouldn’t clamp the barrel at the muzzle to tighten the barrel nut at the receiver.
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Old November 26, 2021, 04:51 PM   #21
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By using a tool that reacts on the barrel extension no torque is transferred into the receiver aside from the threaded part of the receiver. There has to be some force on the threads.
The some force is not because of friction. You can't lube it to zero. It is because of the force needed to pull the barrel into the receiver.

Imagine the alignment pin is gone. Can you still torque the nut to 30 ft-lb minimum? I think not. The receiver is going to spin with the nut. The pin is the what stops the receiver from spinning, and hence it is what transmit the same torque on the nut to the receiver, but in opposite direction.

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Last edited by tangolima; November 26, 2021 at 05:11 PM.
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Old November 26, 2021, 05:43 PM   #22
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Quote:
If you "only" clamp the barrel what is stopping the receiver from turning/spinning as you torque the nut down ?
Quote:
The pin is the what stops the receiver from spinning
No. Just no.

What stops the receiver from spinning is that big lug that fits in the charging handle channel.
https://www.brownells.com/gunsmith-t...rod123846.aspx

I use all 3 types you guys are arguing about, pin block, receiver blocks, and action rods. None of them are ideal for varying reasons. And, just to be clear, if you are damaging the receiver when torquing the barrel nut, ease up on the breaker bar. There is no reason to torque beyong about 30-40 ft-lbs.

People who damage receivers are generally doing something wrong. In 30 years as a smith I have only seen 1 receiver damaged while installing a barrel, and that guy wasn't using receiver blocks, he just clamped the receiver in a vise.
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Old November 26, 2021, 06:30 PM   #23
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No. Just no.

What stops the receiver from spinning is that big lug that fits in the charging handle channel.
That is not at all what we are debating .

Quote:
Originally Posted by 44amp
Don't know what you kids are doing these days, but 45 years ago when I was installing new barrels in M16A1s, it was THE BARREL that went into the vice blocks, NOT the upper receiver.

I mean, just think about it, when you need to clamp something so it doesn't move, which is better, clamping on a thick walled STEEL tube or a thin walled oddly shaped aluminum one??
What we are debating is what 44 said about only clamping the barrel when installing the barrel . This excludes the ways you described which seem to all involve the upper receiver held in place in some way .
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Old November 26, 2021, 07:11 PM   #24
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Didn't some manual from similar time suggested no cleaning was needed?
I seriously doubt that. What is most likely is that the "it never needs cleaning" was GI BS probably from some NCO answering troops questions about why they got M16s and no cleaning kits.

The Army fielded M16s in Vietnam several months, before they got cleaning kits to the troops.

SO most likely is the "doesn't need cleaning" is what some idiot with a bit of rank told a private and it just kept constantly being repeated, even to this day.
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Old November 26, 2021, 07:15 PM   #25
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To piggyback on what Scorch said. Lube the surfaces with appropriate lube, make sure you don’t cross thread and don’t over-tighten and most methods should work.
He did remind me of the lug on the BevBlock that indeed rides in the charging handle channel.

Standard barrel nuts seem to go on problem free. Some of the proprietary handguard types tend to be a little more difficult getting things lined up if you don’t have shims.
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