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Posted: 11/8/2011 10:25:50 AM EST
Link Posted: 11/8/2011 10:37:15 AM EST
[Last Edit: 11/8/2011 10:40:48 AM EST by limaxray]
That....sucks.  

My understanding is receiver blocks aren't usually for barrel installs.  It only stabilizes the bottom of the receiver, and when you torque on the front end, it twists too much  and puts too much pressure exactly where yours cracked.

For flattop uppers, I use a cutting board.

Seriously.  Went to Walmart, picked up a $6 Delrin cutting board.  Cut two pieces about 2" wide.  Trimmed one so it would fit between the lugs.  Put one piece on top, one piece between the lugs, put in vice, crank down (tight, not "crush like a soda can").

Looks like this:



I just put together a DPMS .308 upper using a cutting board without a problem.
Link Posted: 11/8/2011 10:44:02 AM EST
Link Posted: 11/8/2011 11:31:05 AM EST
[Last Edit: 11/8/2011 11:31:14 AM EST by limaxray]
Originally Posted By SilencerShop:
Thanks for the response.  That seems like an excellent low-cost solution that should work pretty well.

I guess I need to head over to Wal-mart before my new receiver gets here.

Seriously, I don't mind buying new gun stuff - but I hate replacing things that were perfectly good before I broke them.


Nothing like that, "oh, CRAP" feeling, is there?    
Link Posted: 11/8/2011 11:35:31 AM EST
[Last Edit: 11/8/2011 11:37:39 AM EST by RDTCU]
Originally Posted By limaxray:
Looks like this:



That's what I do, I've got some scrap UHMW laying around, but I use the mill vise, which has smooth jaws and stays perfectly parallel.


It looks like OP warped it while UN-torquing the barrel nut.  Either removing the original or during the loosening/tightening sequence.
Link Posted: 11/8/2011 11:45:12 AM EST
Link Posted: 11/8/2011 2:18:16 PM EST
[Last Edit: 11/8/2011 2:19:18 PM EST by Rich_V]
With a mill vise I use cardboard, compresses well but does not damage the Aluminum
Originally Posted By RDTCU:
Originally Posted By limaxray:
Looks like this:
http://kevinholman.com/byor/ar10noveske/upperclamped.jpg


That's what I do, I've got some scrap UHMW laying around, but I use the mill vise, which has smooth jaws and stays perfectly parallel.


It looks like OP warped it while UN-torquing the barrel nut.  Either removing the original or during the loosening/tightening sequence.


Link Posted: 11/8/2011 3:14:12 PM EST
Originally Posted By SilencerShop:
Nothing like that, "oh, CRAP" feeling, is there?    


I'm hoping that I'll eventually get old enough to stop doing this sort of thing.



I'm hoping we never get so old we stop screwing around with things that require that much effort to break.  
Link Posted: 11/8/2011 3:34:28 PM EST
[Last Edit: 11/8/2011 3:39:26 PM EST by bloodsport2885]
I've always been shouted down because "it didn't break mine!!" when I tell people not to use receiver blocks that hold the take down pins.  

Sorry for your loss OP.  Try the clamshell type.  Cheap, simple, and they work.
Link Posted: 11/8/2011 3:36:12 PM EST
Impressive.
Link Posted: 11/8/2011 4:02:25 PM EST
Link Posted: 11/8/2011 5:01:07 PM EST
Originally Posted By SilencerShop:
Originally Posted By bloodsport2885:
I've always been shouted down because "it didn't break mine!!" when I tell people not to use receiver blocks that hold the take down pins.  

Sorry for your loss OP.  Try the clamshell type.  Cheap, simple, and they work.


I remember being nervous that I was torquing the upper when I first started using these lug-type receiver blocks - but nothing ever happened and I gradually grew more comfortable.  In this case, I didn't even think anything of it until I took the upper out of the vise and turned it over.

I'm sure you can imagine that sick feeling when I first saw the damage.

Anyway, I'm just looking at this as a life lesson - it would have been far worse if I had damaged a barrel or a registered lower...

I just got back from Wal-mart with my new $5 cutting board that will become a receiver block in the morning.


Helpful hint––if you use a power saw (chop saw, table saw) to cut the board, you WILL get a bunch of cotton-candy looking plastic pieces that smell of burning hobo all over your shop.  
Link Posted: 11/9/2011 11:50:43 AM EST
Link Posted: 11/10/2011 10:03:57 PM EST
anytime I rebarrel an AR, I but the barrel in vice blocks real close to the upper and crank down on the vice handle. then torque the barrel nut to spec. I've been doing it this same way for years, never had a problem.
Link Posted: 11/10/2011 10:37:10 PM EST
phew...

what receiver block were you using?

Also, what torque were you at (80? 20?)
Link Posted: 11/11/2011 2:19:21 AM EST
Link Posted: 11/11/2011 2:58:05 AM EST
Originally Posted By phideaux:
anytime I rebarrel an AR, I but the barrel in vice blocks real close to the upper and crank down on the vice handle. then torque the barrel nut to spec. I've been doing it this same way for years, never had a problem.


This.  Clamp the barrel.

Link Posted: 11/11/2011 9:50:12 AM EST
In a pinch, I've used two chunks of wood.  The one area I was cautious about was to make sure the piece that went between the lugs fit real close lug to lug.  Since I don't have a clamp for an ar10, this is the method I use.
Link Posted: 11/12/2011 6:20:26 PM EST
The correct tool is this:

http://www.brownells.com/.aspx/pid=22385/Product/AR-15-M16-UPPER-RECEIVER-ACTION-BLOCK

You will never crack an upper with this setup
Link Posted: 11/15/2011 7:09:06 AM EST
Originally Posted By bloodsport2885:
I've always been shouted down because "it didn't break mine!!" when I tell people not to use receiver blocks that hold the take down pins.  

Sorry for your loss OP. Try the clamshell type.  Cheap, simple, and they work.


This
Invest
Link Posted: 11/15/2011 11:05:43 AM EST
Originally Posted By phideaux:
anytime I rebarrel an AR, I but the barrel in vice blocks real close to the upper and crank down on the vice handle. then torque the barrel nut to spec. I've been doing it this same way for years, never had a problem.


I think this is the USGI way.  Worked for me last time.
Link Posted: 11/15/2011 1:23:50 PM EST
I've used the same block to rebarrel uppers or put new freefloats on several brands of uppers and never had a problem. LMT, LAR, Alexander Arms, Accurate Armory, DSArms (Cardinal Forge) and none have cracked like that. Hate to see damage like that SS!

Posted Via AR15.Com Mobile
Link Posted: 11/17/2011 4:55:45 AM EST
Originally Posted By CAR-15:
The correct tool is this:

http://www.brownells.com/.aspx/pid=22385/Product/AR-15-M16-UPPER-RECEIVER-ACTION-BLOCK

You will never crack an upper with this setup


I had one like this and it shattered the 3rd time I used it.
Link Posted: 11/17/2011 12:01:03 PM EST
Originally Posted By phideaux:
anytime I rebarrel an AR, I but the barrel in vice blocks real close to the upper and crank down on the vice handle. then torque the barrel nut to spec. I've been doing it this same way for years, never had a problem.


I also use the aluminum vice blocks on the barrel.

Link Posted: 11/18/2011 6:21:54 PM EST
Originally Posted By Flamethrower:
Originally Posted By CAR-15:
The correct tool is this:

http://www.brownells.com/.aspx/pid=22385/Product/AR-15-M16-UPPER-RECEIVER-ACTION-BLOCK

You will never crack an upper with this setup


I had one like this and it shattered the 3rd time I used it.


You got a bad one.  My Brownells works great and takes lots of torque.
Link Posted: 11/18/2011 6:37:42 PM EST
Originally Posted By magnum_99:
Originally Posted By Flamethrower:
Originally Posted By CAR-15:
The correct tool is this:

http://www.brownells.com/.aspx/pid=22385/Product/AR-15-M16-UPPER-RECEIVER-ACTION-BLOCK

You will never crack an upper with this setup


I had one like this and it shattered the 3rd time I used it.


You got a bad one.  My Brownells works great and takes lots of torque.


Good thing about Brownells is everything you buy from them is guaranteed for life.
Link Posted: 11/18/2011 6:40:24 PM EST
Link Posted: 11/18/2011 7:02:06 PM EST

Seriously.  Went to Walmart, picked up a $6 Delrin UHMW   cutting board .



squeeze it from the outside, with a spacer in the upper so you don't crush it.

Link Posted: 12/7/2011 6:35:26 AM EST
use a clamshell clamp from brownells.
Link Posted: 12/7/2011 7:18:03 AM EST
Originally Posted By KiowaCreekRaider:
Originally Posted By bloodsport2885:
I've always been shouted down because "it didn't break mine!!" when I tell people not to use receiver blocks that hold the take down pins.  

Sorry for your loss OP. Try the clamshell type.  Cheap, simple, and they work.


This
Invest


I have broken a couple barrel wrenches using a cheater bar while using the clamshell, trying to dislodge an Armalite barrel nut.  No damage to the upper.
Link Posted: 12/11/2011 4:10:11 AM EST
Originally Posted By bloodsport2885:
I've always been shouted down because "it didn't break mine!!" when I tell people not to use receiver blocks that hold the take down pins.  

Sorry for your loss OP.  Try the clamshell type.  Cheap, simple, and they work.


People use the pin style block the wrong way.  They pin the upper then put the block in the vise.  It's gonna break!

Do this.



Two pieces of delrin well do the same.

Link Posted: 12/23/2011 1:33:19 PM EST
Nothing but a clamshell for me. It puts all the stress on the beefiest parts of the upper.
Link Posted: 12/29/2011 1:59:51 PM EST
Originally Posted By madcratebuilder:
Originally Posted By bloodsport2885:
I've always been shouted down because "it didn't break mine!!" when I tell people not to use receiver blocks that hold the take down pins.  

Sorry for your loss OP.  Try the clamshell type.  Cheap, simple, and they work.


People use the pin style block the wrong way.  They pin the upper then put the block in the vise.  It's gonna break!

Do this.

http://i32.photobucket.com/albums/d37/madcratebuilder/Temps/pri02.jpg

Two pieces of delrin well do the same.



This, especially with the DPMS block that supports the inside of the receiver too. Use one of the pieces of cutting board to protect the rail and the receiver block at the bottom.

FWIF I usually one of the clamshell blocks because it was cheaper and quicker to get my hands on when I needed one than the pin style block, but the pin style block is easier to use when installing some forearms and that sort of thing, so I feel that it is a little more versatile.

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