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Posted: 4/24/2002 1:03:11 PM EDT
Did a search and really didnt find the answer to what I am looking for.

I want to build a kit from the ground up and the only part I am unsure of is installing the barrel. I have the ARMY TM so I am familiar with the torque values (30-60lbs), and the benifit of torquing and losening 3 times to ensure good thread contact. I am also familiar with lining up the barrel nut by tightning (if necessary) to allow clearance for the gas tube)

Why are action blocks recommended over barrel vices? The ARMY TM specifically shows the use of a barrel vice. Do I need a Action Block? I already have the Barrel Blocks.

I am deathly afraid of breaking the index pin, but am unsure of how it can be stressed if the barrel is securely locked in place in the vice. If the barrel does move in the vice, shouldn't the upper reciever move also? You would think that if the reciever moved with the barrel it wouldn't stress the index pin.

Another question I have is directly related to what is stated in the ARMY TM. The ARMY TM states that after you install the barrel you should lood through the upper reciever (through the barrel) and align it on a vertical object (so it bisects the hole in the barrel) then it says to look at your iron sights. The vertical line should align with the iron sights. If it doesn't the TM says you should reinstall, and if that doesnt work you have a worn out upper reciever.

So, since this will be a new kit, do I need to worry about the above? How will reinstalling the barrel make the iron sights line up better with the vertical object? Only thing I can think of is that the upper reciever has too much play right from the get go. But I could be wrong.

Thanks for all your help!
Link Posted: 4/24/2002 1:15:17 PM EDT
Done it both ways, but I prefer to use the Peace River action blocks. It gives good support and I don't worry about the index pin wallowing out the receiver slot and causing the front site to cant to the right. Just grease the receiver threads and extension flange before torquing. The PR blocks can be found on the Brownells and JP Enterprises web sites.
Link Posted: 4/24/2002 2:09:36 PM EDT
Link Posted: 4/24/2002 3:13:15 PM EDT
Depends.

The receiver block holds the parts much more securely than the barrel blocks and don't leave a bunch of aluminum all over the barrel, but the receiver blocks leave a little polished spots on the receiver finish where they contact the receiver.
Link Posted: 4/24/2002 3:34:04 PM EDT
Well, I'm getting the impression that reciever blocks are the way to go. I guess I probably knew that already.

Its just that money is tight right now and I already have everything short of the reciever blocks.

Would I, or Could I damage my upper or index pin just using the barrel blocks? If I torque to 35lbs would that be enough to cause wear on the upper where the index pin is or cause my barrel to be canted?

Thanks again
Link Posted: 4/24/2002 4:36:12 PM EDT
I've done it a couple of times with the barrel blocks. I'm sure it would be better using the receiver block but just did'nt seem to be worth the money for the 2 times. BM has barrel blocks for $15 and the rec blocks go for around $40. You could probably get a gunsmith to do it for $20. If you are carefull you should'nt screw up the index/alignment pin.
Link Posted: 4/24/2002 5:49:12 PM EDT
[Last Edit: 4/24/2002 5:52:58 PM EDT by gregw45]

Originally Posted By NewGuy:
If I torque to 35lbs would that be enough to cause wear on the upper where the index pin is or cause my barrel to be canted?
Thanks again



Save a little longer and buy the receiver blocks. I've used both and the aluminum barrel blocks only get used when I'm swapping flash hiders.

I haven't noticed any damage to the index pin or finish on the upper receiver using the receiver blocks (even when removing a barrel that was torqued to well over 80ft/lbs.).

All barrels I've installed using the receiver blocks have zeroed within a couple of clicks of mechanical zero right off the bench.
Link Posted: 4/24/2002 7:44:15 PM EDT
Thanks guys! thats the exactly the input I was looking for. Its good to know help is right there for the asking.

I appriciate it!
Link Posted: 4/24/2002 7:53:14 PM EDT
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