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Posted: 2/18/2007 11:53:50 PM EST
[Last Edit: 8/11/2012 8:01:24 PM EST by DoubleFeed]
Link Posted: 9/17/2007 12:51:37 PM EST
[Last Edit: 9/17/2007 4:41:25 PM EST by jham]
Okay, let's say that you have an upper that's already barreled.  You've fired MAYBE a hundred rounds down the pipe.  Now you want to change out the entire bolt carrier assembly put in something better/stronger/lighter (pick one) and leave the rest of the upper alone.  What do you say about checking for headspacing in this scenario?  Better to be safe than sorry?
Link Posted: 11/12/2007 3:59:00 PM EST
[Last Edit: 11/12/2007 4:14:57 PM EST by AR15Texan]
Nevermind
Link Posted: 1/7/2008 6:43:07 PM EST

Originally Posted By jham:
Okay, let's say that you have an upper that's already barreled.  You've fired MAYBE a hundred rounds down the pipe.  Now you want to change out the entire bolt carrier assembly put in something better/stronger/lighter (pick one) and leave the rest of the upper alone.  What do you say about checking for headspacing in this scenario?  Better to be safe than sorry?


I'd like to know about this too.
Link Posted: 1/16/2008 8:02:43 AM EST

Originally Posted By jham:
Okay, let's say that you have an upper that's already barreled. You've fired MAYBE a hundred rounds down the pipe. Now you want to change out the entire bolt carrier assembly put in something better/stronger/lighter (pick one) and leave the rest of the upper alone. What do you say about checking for headspacing in this scenario? Better to be safe than sorry?




I'd like to know about this too.

+1
Link Posted: 1/17/2008 1:37:07 PM EST
[Last Edit: 1/17/2008 1:38:15 PM EST by DosZap]
I would do it/have done it, in a nano sec, and not look back.

I had a Dealer that was a Smith, and he also had the Colt contract for warranty work.
He said in 30 years of business, and working on AR's, he never checked HS on new, nearly new sticks.

Waste of time.



CAVEAT to this, an OLD barreled upper, and a new bolt, or a new Upper, and an OLD bolt.

Check.
Link Posted: 2/2/2008 12:55:55 AM EST
Need some help with headspace.  I finished building a 24" Varmint AR15.  I bought the Forster .223REM GO and NOGO headspace gauges and checked the chamber tonight.  The GO Gauge has 1.4636 and the NOGO has 1.4666.  I could not close the bolt on either the GO or the NOGO gauge.  Below are the rifle's details:

DPMS lower with Rock River Arms LPK and two-stage trigger kit.
RRA A4 Stripped Upper with charging handle and foward assist
DPMS 24" Bull Barrel with Extension installed.
JP Enterprise free-float handguard
DPMS flat top gas block and gas tube
Mil-spec BCG
Magpul PRS stock with Rifle buffer tube, spring, and buffer

I separated the upper and lower receivers.  I then removed the extractor and ejector.  I placed the bolt back into the bolt carrier.  Installed the key, firing pin, and retaining clip into the bolt carrier.  I inserted the GO gauge and then slide the BCG into the upper.  I pushed the BCG forward and saw that the bolt started to rotate about 10 degrees and stop.  The NOGO gauge was about the same.

I then grabbed another BCG that has seen about 350-400 rounds.  I only removed the extractor as I was having trouble getting the ejector roll pin out.  I then installed this BCG assembly into the upper.  I applied more pressure than before as I could feel the ejector spring compress.  The bolt then snapped into battery.  I then tried the NOGO and it too snap into battery with about the same pressure.  I figured I was pushing too hard in order to overcome the ejector spring and concluded that this test was no good.

I then spent some more time on the used BCG and finally got the ejector roll pin out.  I then tried it back in the DPMS 24" upper.  This time the bolt closed on the GO gauge but it still took more pressure than I thought should be used.  Shouldn't I see the bolt rotate easily on the GO gauge?  Next I tried the NOGO gauge on the used BCG.  The bolt started to rotate a few degrees but then stopped.  

I then tried the brand new BCG on the older upper.  This is a J&T kit upper with a 16" barrel.  The new BCG would not close on the GO or NOGO gauge.  So it looks like my chamber and bolt are too tight.  Doesn't the GO gauge measure maximum SAMMI length.  Should I not run any ammunition through the new AR?  Should I try some other bolts?

Link Posted: 2/5/2008 9:53:44 PM EST
[Last Edit: 12/25/2010 5:56:08 PM EST by FALARAK]
Link Posted: 2/5/2008 10:03:23 PM EST
[Last Edit: 12/25/2010 5:54:56 PM EST by FALARAK]
Link Posted: 2/17/2008 6:24:26 PM EST
[Last Edit: 2/25/2008 11:34:49 AM EST by AR15Texan]

Originally Posted By FALARAK:
Most NATO chambered AR's will close on a civilian NOGO.  It does sounds like you are checking them correctly... but the fact you are tight on a civvy GO gauge in both weapons is highly suspect.  Are you sure both chambers and bolts, and barrel extension are impeccably clean?  What you are describing is extremely rare, and likely something else is happening.  Have you tested using a live round?  How much force is required to chamber that?


Sure did make sure they were clean.  There was only one small spec of dirt or grease in the DPMS barrel extension that I could see.  I scraped any traces of carbon off the bolt face of the J&T bolt assembly.  The DPMS bolt face was brade new.  The barrel of 24" DPMS barrel has 223 stamped in it so I don't believe it to be NATO spec'ed.

ETA, I had to use the forward assist in order to chamber a live round.
Link Posted: 2/18/2008 11:27:23 AM EST
I hate to change subjects, but...

What actually causes a change in headspace value as rifles are used?  Is the bolt face wearing down, or does the barrel chamber or extension go through changes over time?  And how many rounds can go through an assembled upper before the problem part needs to be replaced?
Link Posted: 2/18/2008 12:58:55 PM EST

Originally Posted By cybrscream:
I hate to change subjects, but...

What actually causes a change in headspace value as rifles are used?  Is the bolt face wearing down, or does the barrel chamber or extension go through changes over time?  And how many rounds can go through an assembled upper before the problem part needs to be replaced?


Wear.  The bolt's lugs wear on the backside and the extension lugs wear on the front. The bolt face doesn't wear much at all unless primer leakage and that is limited to the primer area.  That is HIGHLY apparant.

Wear rate depends on a myriad of influences like port pressure/timing,  abrasives/lubricant and overall fit of the parts.  The majority of wear happens in the first few hundred rounds until all lugs are lapped in and bearing uniformly.  Swapping bolts is a sure way to increase wear as the lugs are now bearing with varying loads until lapped in again.
Link Posted: 2/21/2008 9:54:01 AM EST

Lower Receiver Extension (Buffer Tube)
Rifle - 35 to 39 Ft. Lbs.


I'm wondering where I can buy a 5/8" wrench with a square 1/2" hole in it to attach my torque wrench to for achieving proper buffer tube torque.

I found an armor's wrench on CDNN for $20 but not sure if it will work.  I would rather just check out the hardware store but I'm not sure if this is a specialty tool.
Link Posted: 2/23/2008 5:57:04 PM EST
[Last Edit: 2/23/2008 5:59:45 PM EST by 556Cliff]

Originally Posted By BBsteel:

Lower Receiver Extension (Buffer Tube)
Rifle - 35 to 39 Ft. Lbs.


I'm wondering where I can buy a 5/8" wrench with a square 1/2" hole in it to attach my torque wrench to for achieving proper buffer tube torque.

I found an armor's wrench on CDNN for $20 but not sure if it will work.  I would rather just check out the hardware store but I'm not sure if this is a specialty tool.


Brownells AR Buttstock Tool.

It's the best one I can find.
Link Posted: 2/29/2008 7:10:45 PM EST
[Last Edit: 3/1/2008 5:42:35 PM EST by cardude]
About the 5/8' wrench for the buttstock and torque spec. I use a GI M16 tool. meets all my needs. Another tool that will work for you is a 'crow foot wrench' get a 5/8" with a 1/2" drive hole. That will work great

On a different note.

is it necessary to break in a chrome lined barrel. such as a bushmaster? chrome lined was not mentioned in the procedure listed about.

Link Posted: 3/2/2008 11:36:54 AM EST
There really is no "break in" for chrome lined barrels. Just shoot it. The process of breaking in a new barrel is to polish the surface. Chromium is already a smooth polished surface.

When a Chrome lined barrel finally "breaks in", IT'S BROKEN!!
Link Posted: 4/27/2008 11:46:21 AM EST
Does any one have a source for the 1.465" gauge? I could not find one labeled that way. The closest was a 1.464"
Link Posted: 5/18/2008 12:58:32 AM EST
[Last Edit: 6/4/2008 1:13:37 AM EST by samurairabbi]
-------- added June 4 -------------
I found the answers to my original questions at the Indy gun show this last weekend. The 3-thou range of these Forster guages is intended for checking headspace on BOLT-ACTION .223 rifles.
------------------------------------

I offer a question on the .223 Forster go/nogo guages.  I have a set of these go/nogo guages marked the same as in AR15Texan's earlier post: 1.4636 Go and 1.4666 Nogo.  Clearly these are different guages than the "3-decimal" Forster ones compared in the lead post of this thread.

The "military" headspace range for a "New" rifle is given in this thread as 1.4646" to 1.4706".  This is a 6-thousandth range.  The "4-decimal" Forster guages give a 3-thousandth range between the Go and Nogo range, which is HALF the allowable military new range.  Does that difference indicate that the "civilian" .223 headspace range has become far tighter than the 5.56 military headspace range?

An earlier post by Falarak in this thread indicated that some new in-spec military chambers could still close on a Forster (civilian) Nogo guage. Is this another aspect of the tighter 3-thou range of the newer Forster guages?  
Link Posted: 6/7/2008 1:53:26 PM EST

Originally Posted By samurairabbi:
Does that difference indicate that the "civilian" .223 headspace range has become far tighter than the 5.56 military headspace range?


From my research and talking with others the 5.56 x 45 NATO chamber has a longer leade than the .223 REM chamber.  Therefore the .223 REM should be "tighter" than the 5.56.  Correct me if I'm wrong but this is why one can get away with shooting .223 REM in a 5.56 NATO barrel but not vice versa.
Link Posted: 6/21/2008 9:43:12 PM EST
[Last Edit: 7/10/2008 8:22:01 PM EST by Patriot32]
I am bulding a complete rifle from scratch. I have a stripped colt upper, Rock river barrel, Dpms Lower, the bolt was a brand new bolt I don't know what kind it was given to me. This rifle will be put together with many other various parts. When I am done should I have the headspace checked? I will have about $400.00 in this rifle when I am done.
Link Posted: 8/13/2008 12:13:34 PM EST

Originally Posted By Patriot32:
I am bulding a complete rifle from scratch. I have a stripped colt upper, Rock river barrel, Dpms Lower, the bolt was a brand new bolt I don't know what kind it was given to me. This rifle will be put together with many other various parts. When I am done should I have the headspace checked? I will have about $400.00 in this rifle when I am done.


Yes, if you get the barrel and bolt together no need to check, anytime the bolt did not come with the barrel it should be checked.
Link Posted: 11/12/2008 12:31:29 AM EST
What if you change out a barrel on an existing AR upper? Use the same BCG, but with the new barrel. As long as the barrel is in spec, would headspace change?
Link Posted: 11/12/2008 12:38:26 AM EST
[Last Edit: 11/12/2008 12:39:14 AM EST by FALARAK]
Originally Posted By Beyond_Visual_Range:
What if you change out a barrel on an existing AR upper? Use the same BCG, but with the new barrel. As long as the barrel is in spec, would headspace change?


This was answered above.... change a bolt, change a barrel - same thing.

Bolts are NOT (generally in production) fitted to a barrel. There are in spec barrels, and in spec bolts. As long as the new bolt barrel is in spec, then there is no issue with headspacing. Replace away.

However, you have two choices:

1) trust the bolt barrel is in spec
2) check the headspace with a COLT II FIELD GAUGE to ensure the headspace at least meets minimum safety specifications.

My advice - is simply to shoot it. Headspace issues are extremely rare.
Link Posted: 11/12/2008 2:35:53 AM EST
[Last Edit: 11/12/2008 2:42:09 AM EST by friendlysniper]
Is there a way to reliably install a barrel without a torque wrench (or for that matter, anything else) but still get in the specified range of torque?  I'm installing a YHM free float and don't have an armorers tool or even the upper yet.  Was more concerned about getting enough magazines first.  

Ok, I've changed my mind.  Is there any way to reliably install a barrel in an upper WITH an armorers tool and no torque wrench?
Link Posted: 12/7/2008 2:50:07 PM EST
Where are some good vendors to get 1/7" Barrels ?
RRA has some good looking 1/8"
Link Posted: 12/7/2008 10:55:44 PM EST
[Last Edit: 12/7/2008 10:58:12 PM EST by FALARAK]
Originally Posted By friendlysniper:
Is there a way to reliably install a barrel without a torque wrench (or for that matter, anything else) but still get in the specified range of torque?  I'm installing a YHM free float and don't have an armorers tool or even the upper yet.  Was more concerned about getting enough magazines first.  

Ok, I've changed my mind.  Is there any way to reliably install a barrel in an upper WITH an armorers tool and no torque wrench?


You do not need a torque wrench to install a barrel.  It helps for people who have no experience with torque values, and cannot tell the difference between 30ft-lbs and 80ft-lbs with their arm.  A torque wrench is simply nice, to set the nut initially to the MINIMUM spec. Then you simply turn more until the next gas tube hole lines up.  You don't have to use a torque wrench for this.  The risk would be... if you just snugged it up WAY too loose, and then aligned the next gas tube hole - the final torque setting may be under spec (not likely and not a safety issue).  The other risk would be - if you set the initial torque too tight... you could not get it to the next gas tube hole - because the nut got too tight and started to gall/malform the upper receiver.  Of course with the latter, you would figure that out pretty quick... and just back off, and tighten to the gas tube hole that does line up without breaking your arm.

I do like to snug the nut 3 times... then back it off, then get out the torque wrench, set it to 30 lbs.... click.... then I simply check the gas tube alingment, and tighten until the next hole lines up.  However, if I didnt have a torque wrench handy - I wouldn't sweat it a bit.  If you are a total newbie... it is better to have one handy.
Link Posted: 12/8/2008 7:13:32 PM EST
Okay, I have a DPMS which all I want to do is change the upper receiver from an A1 DPMS to an A4 RRA.
As long as use the same barrel and bolt from my DPMS I will not need to check headspace, correct?

Thanks,
J
Link Posted: 12/8/2008 11:12:40 PM EST
Originally Posted By AR-15Jim:
Okay, I have a DPMS which all I want to do is change the upper receiver from an A1 DPMS to an A4 RRA.
As long as use the same barrel and bolt from my DPMS I will not need to check headspace, correct?

Thanks,
J


Correct.  Again - headspace is set from the bolt rear lugs, to the front of the barrel extension lugs.  The upper receiver has no effect on headspace.... if the bolt will close at all, the measurement is simply set by the bolt and the barrel (extension)
Link Posted: 1/3/2009 12:14:45 PM EST
A torque value for the thread on AR-10 gas keys:

Originally Posted By ArmaLite:
Hold the boat!

35-40 inch pounds is an error that hit ArmaLite several years back.

In creating written work procedures we decided to buy specialized torque wrenches to assure we met GI specs.  The Army TM specified, if I recall, 35-40 Inch pounds so we followed that standard.

It was a disaster.  Lots of complaints of loose gas.  We verified all was in spec but still had the problem.  Finally we went to the source... the screw manufactures.  The correct spec was 55 inch pounds plus/minus 5.  We changed and the problem went away.  We contacted our friends at Rock Island and the manual has been changed to a similar rate.

Yep, our discovery led to a change in the manuals.  Problem is that most people have old versions.

So increase your torque...

Some ArmaLites with the lighter torque may still be untightened.  It's easy to do in the field.


Link Posted: 1/3/2009 12:51:25 PM EST
Crap.  I am going to risk looking like an idiot here by saying this, but I don't understand this headspace stuff at all (even after reading the links at the top of the post).

I just recently built my first AR and it's a pistol.  Since I lack certain tools to get the job done right, I cant be certain that I tightened the barrel nut down to spec, but I did it as much as I could by hand using a barrel nut wrench.

I have not test fired it yet as I'm still waiting on a few parts and finishing touches but now I'm concerned that I may have an AR just waiting to kaboom on me or something.  I have no idea.

How important is all this headspacing stuff if I pretty much followed the typical procedures for assembling an AR (minus torquing the barrel nut down to exact specs)?
Link Posted: 1/6/2009 2:59:24 PM EST
hello this is my first post here... I am assembling my first AR as many here. I understand headspacing and have delt with it on other rifles, but i've never owned an AR till now.. am I correct to assume that if I have a good dpms upper and BCG and a good quality barrel I should be able to just assemble to propper specs and shoot away?
also when I gauge my head space after assembly to double check. what does it mean if it doesn't gauge right? I'm not that far yet I'm just curious if headspace was wrong how is it fixed?
Link Posted: 1/9/2009 7:47:58 PM EST
What I am having trouble getting is why would you need a go gauge.  Say your action will not close on a field gauge but will on a live round when you go to test fire then wouldn't the rifle be safe to fire?
Link Posted: 1/9/2009 9:54:40 PM EST
I'm certain i'll get a lecture for this, but I usually just fire a round (from the hip/etc) and look at the brass (assuming it chambers a round, and they always do). I figure if the brass shows no signs of ugliness I'm in good shape. It's my understanding that headspace issues are rare, but w/the abundance of mfgrs out there these days it does give one cause to wonder.
Link Posted: 1/11/2009 6:35:57 PM EST
Originally Posted By Xtragg:
What I am having trouble getting is why would you need a go gauge.  Say your action will not close on a field gauge but will on a live round when you go to test fire then wouldn't the rifle be safe to fire?


Provided the round is sized to spec - yes.  A go gauge is only needed to give an indication of the exact size of the chamber, used in conjunction with many other sized gauges - up to the Colt Field II gauge.  

If it wont close on a Colt Field II gauge, and it will close on a live round that is sized to spec, then yes - it will be safe to fire.

Link Posted: 1/13/2009 9:25:03 PM EST
[Last Edit: 1/13/2009 9:27:03 PM EST by VaFish]
What is the torque value for the barrel extension?

Or does it vary with head space?

I can't find anything that tells me how to install the barrel extension on a stripped barrel.  Everything I find has the barrel extension already installed in their instructions.  Someone must have to put the extensions on.  I see barrel extension sockets for sale on several sites.
Link Posted: 1/20/2009 5:36:08 AM EST
[Last Edit: 1/20/2009 5:39:28 AM EST by ggreer]
I've built a lot of AR's and have used a torque one time and it slipped off and blood came from my fingers. I talked with a old guy that work on M14's in the Marines and what he called toy guns before retireing. He said tighen it (the barrel) a couple of times then tighen it to get the gas tube in and go with it. He also told me to take the BCG and hold it with out the charging handle to the back of the recevier and let it go and if it locked in place put the pins in it and put it in the cage. Oh well it works for me and I still have all my finger and eyes I guess that is saying something.
ggreer
Link Posted: 1/20/2009 8:30:09 AM EST
Originally Posted By VaFish:
What is the torque value for the barrel extension?

Or does it vary with head space?

I can't find anything that tells me how to install the barrel extension on a stripped barrel.  Everything I find has the barrel extension already installed in their instructions.  Someone must have to put the extensions on.  I see barrel extension sockets for sale on several sites.


This should only be installed by a competent barrel-smith.  It is not something for the typical home builder, because this is where headspace is set, by the barrel manufacturer, and finish reaming of the chamber is done.  

http://www.ar15barrels.com/making.shtml

I have seen the torque value posted before, but I dont recall it.

Link Posted: 1/28/2009 8:57:49 AM EST
I've found a reference to the torque value as being 150 ft lbs.

http://www.ar15.com/forums/topic.html?b=3&f=4&t=403752

I'm going to give it a try.
Link Posted: 2/23/2009 5:29:17 PM EST
I bought an aftermarket mil spec complete bolt and carrier and just dropped it into my ar.  It fired without a problem.  Should I have checked the headspace?
Link Posted: 3/2/2009 5:00:17 AM EST
Headspace gages don't measure leade only base to shoulder margine which is a point about mid point of shoulder slope angle. Only headspace gages that match your 5.56 or .223 chamber should be used although I've never had a problem using either on either chamber, I've also never had a barrel bolt combination fail headspace on an AR period. I'd flat be worried about a bolt that was hard to close on a go gage or closed on an no-go gage. trust them thats what they are for.
Originally Posted By AR15Texan:
Originally Posted By samurairabbi:
Does that difference indicate that the "civilian" .223 headspace range has become far tighter than the 5.56 military headspace range?


From my research and talking with others the 5.56 x 45 NATO chamber has a longer leade than the .223 REM chamber.  Therefore the .223 REM should be "tighter" than the 5.56.  Correct me if I'm wrong but this is why one can get away with shooting .223 REM in a 5.56 NATO barrel but not vice versa.


Link Posted: 3/18/2009 7:33:45 PM EST
That is correct except headspace doesn't show the leade or freebore on a chamber.
Originally Posted By NAVYRETIRED1:
Headspace gages don't measure leade only base to shoulder margine which is a point about mid point of shoulder slope angle. Only headspace gages that match your 5.56 or .223 chamber should be used although I've never had a problem using either on either chamber, I've also never had a barrel bolt combination fail headspace on an AR period. I'd flat be worried about a bolt that was hard to close on a go gage or closed on an no-go gage. trust them thats what they are for.
Originally Posted By AR15Texan:
Originally Posted By samurairabbi:
Does that difference indicate that the "civilian" .223 headspace range has become far tighter than the 5.56 military headspace range?


From my research and talking with others the 5.56 x 45 NATO chamber has a longer leade than the .223 REM chamber.  Therefore the .223 REM should be "tighter" than the 5.56.  Correct me if I'm wrong but this is why one can get away with shooting .223 REM in a 5.56 NATO barrel but not vice versa.




Link Posted: 3/23/2009 12:40:01 AM EST
I'm currently waiting for my uppers to arrive, but believe in being prepared.

I've read both articles regarding break-in and now am more confused that I thought

one of the articles states that proper break-in proceedures are necessary, the other says it's B.S.

I guess I need to get some honest opinions from you people with regards to the necessity of this or not

Jeff
Link Posted: 3/31/2009 6:32:49 PM EST
I am no expert on metallurgy, I would suggest reading what the barrel manufactures suggest, since they are the experts, and do extensive testing on these things. But just like anything that is going to have metal to metal contact even after finish machining is going to have a break in period.
Link Posted: 4/19/2009 5:09:42 PM EST
How do you use a torque wrench with the armorer's tool?

Since the drive socket is offset from the barrel, the lever arm is longer giving a mechanical advantage when using the armorer's tool compared to using the torque wrench alone.  How do you account for the extra moment?  Do you have calculate by knowing the lever arm length of your torque wrench and re-multiplying by the new lever arm lenght while using armorer's tool?  Or, does the spec of 30 ft-lbs, 80ft-lbs already account for using the tool?

For those that actually use the torque-wrench with the armorer's tool, how do you do this?
Link Posted: 4/19/2009 8:27:09 PM EST
Originally Posted By jas000:
How do you use a torque wrench with the armorer's tool?

Since the drive socket is offset from the barrel, the lever arm is longer giving a mechanical advantage when using the armorer's tool compared to using the torque wrench alone.  How do you account for the extra moment?  Do you have calculate by knowing the lever arm length of your torque wrench and re-multiplying by the new lever arm lenght while using armorer's tool?  Or, does the spec of 30 ft-lbs, 80ft-lbs already account for using the tool?

For those that actually use the torque-wrench with the armorer's tool, how do you do this?


The posted values take this into account.  The distance between the torque wrench hole, and the centerline is a standard.  Torque values are NOT a big deal on the AR barrel nut - because they are a simple minimum, then turn to the next hole.  The maximum doesnt really apply.  This isnt like a cylinder head.  You snug it up three times, then tighten until the next gas hole lines up.

Link Posted: 5/11/2009 8:09:14 PM EST
How critical is the 40 inch pounds for the receiver extension? Inch/pounds torque wrenches are pretty expensive. I installed a new Vltor stock tube and I snugged it up but it was probably more than 40 inch pounds. Is overtightening the buffer tube a bad thing?
Link Posted: 5/29/2009 1:01:30 PM EST
OK, another new builder headspace question...



I bought a complete upper and used some Loctite retaining compound where the face of the barrel extension ring meets the upper receiver (this was my attempt at "bedding" the barrel.)  I torqued to 30 ft.-lb.



This will obviously add some length to the headspace (although I can't imagine it would be more than a couple thousandths.



Anyone see a potential problem with this?
Link Posted: 5/30/2009 1:53:03 PM EST
Originally Posted By sniperfrog:
How critical is the 40 inch pounds for the receiver extension? Inch/pounds torque wrenches are pretty expensive. I installed a new Vltor stock tube and I snugged it up but it was probably more than 40 inch pounds. Is overtightening the buffer tube a bad thing?


Non-issue.  That is not a critical torque spec.  Just get it snug.  Then - optionally stake it if you want to, or you can use *one drop* of *blue* loctite to optionaly add some insurance against it loosening up over time.  I do neither.  Just get it good and snug and I am sure I am well over 40 inch pounds.

Link Posted: 5/30/2009 2:03:12 PM EST
Originally Posted By eracer:
OK, another new builder headspace question...

I bought a complete upper and used some Loctite retaining compound where the face of the barrel extension ring meets the upper receiver (this was my attempt at "bedding" the barrel.)  I torqued to 30 ft.-lb.

This will obviously add some length to the headspace (although I can't imagine it would be more than a couple thousandths.

Anyone see a potential problem with this?


That will not add ANY length to the headspace.  You need to understand where the headspace is set by.

First - using a bedding compond like that will consume the space mostly between the upper receiver and barrel entension on the sides of the extension.  When you torque down the barrel nut, any locktite compound will be squeezed out of the area between the edge surfaces of the upper recevier, and the barrel entension ring.... this could not possible even equal .001 in additional material.  The specs on the receiver wont even be that kind of tolerance... more than likely +-.003".   In fact - a populare AR build will often SHIM this area with very thin shim stock - to modify the barrel nut/gas tube alignment so he gets the best possible torque spec at the correct alignment location.  Not necessary - but cool.

Now - if we did push the barrel forward another .003" (for instance) this still has ZERO effect on headspace.  The headspace is set from the bolt FACE to the chamber.  This distance is set by a factor of the back of the bolt lugs, contacting the barrel exension lugs.  This is why, ONLY the barrel extension, when installed to the barrel, controls the headspace.  All bolts are made to the same spec.  Therefore, the position of the barrel in the upper receiver makes no difference, because the bolt carrier is freely moving, and will just simply slide an extra .003" forward in this case.  There is a large margin of tolerance here.

As an end user - you CANNOT have any impact to headspace.  This is set by the barrel maker when they install the extension on the barrel and pin it.  Nothing you do to the weapon can increase or decrease headspace.  All you can do is *verify* headspace with a gauge, and replace the barrel if it is badly out of spec, which is extremely rare.
Link Posted: 6/1/2009 12:37:57 PM EST
[Last Edit: 6/1/2009 1:36:58 PM EST by eracer]




Originally Posted By FALARAK:



Originally Posted By eracer:

OK, another new builder headspace question...



I bought a complete upper and used some Loctite retaining compound where the face of the barrel extension ring meets the upper receiver (this was my attempt at "bedding" the barrel.) I torqued to 30 ft.-lb.



This will obviously add some length to the headspace (although I can't imagine it would be more than a couple thousandths.



Anyone see a potential problem with this?




That will not add ANY length to the headspace. You need to understand where the headspace is set by.



First - using a bedding compond like that will consume the space mostly between the upper receiver and barrel entension on the sides of the extension. When you torque down the barrel nut, any locktite compound will be squeezed out of the area between the edge surfaces of the upper recevier, and the barrel entension ring.... this could not possible even equal .001 in additional material. The specs on the receiver wont even be that kind of tolerance... more than likely +-.003". In fact - a populare AR build will often SHIM this area with very thin shim stock - to modify the barrel nut/gas tube alignment so he gets the best possible torque spec at the correct alignment location. Not necessary - but cool.



Now - if we did push the barrel forward another .003" (for instance) this still has ZERO effect on headspace. The headspace is set from the bolt FACE to the chamber. This distance is set by a factor of the back of the bolt lugs, contacting the barrel exension lugs. This is why, ONLY the barrel extension, when installed to the barrel, controls the headspace. All bolts are made to the same spec. Therefore, the position of the barrel in the upper receiver makes no difference, because the bolt carrier is freely moving, and will just simply slide an extra .003" forward in this case. There is a large margin of tolerance here.



As an end user - you CANNOT have any impact to headspace. This is set by the barrel maker when they install the extension on the barrel and pin it. Nothing you do to the weapon can increase or decrease headspace. All you can do is *verify* headspace with a gauge, and replace the barrel if it is badly out of spec, which is extremely rare.


So what you are saying is:



The bolt travels as far as it needs to for the lugs to engage the barrel extension (which is why the position of the barrel extension to the upper receiver is irrelevant.) There is nothing in the upper receiver that limits the forward travel of the bolt, at least as far as headspace is concerned.  I mistakenly thought the bolt travel was controlled by the upper receiver, and the headspace was controlled by the length of the barrel extension.



I think I understand much better now. Thanks.

Link Posted: 6/2/2009 7:06:01 PM EST
If I don't have a head space gauge can I use a dummy round to check how it feeds and what not?
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