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Posted: 4/13/2012 2:39:29 AM EDT
| I'm expanding my ar smithing skills to barrel work. I've got all the tools except for an block to mount the upper into a vice. The problem is there are so many kinds to choose from! Clam shells...pin mounted...etc. which is the style for me? What are the advantages and disadvantages of the different styles? I've heard the clam shells can allow some wiggle and rub up the finish for example. Looking to keep price down and place an order soon so any feedback is really appreciated. |
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I'm expanding my ar smithing skills to barrel work. I've got all the tools except for an block to mount the upper into a vice. The problem is there are so many kinds to choose from! Clam shells...pin mounted...etc. which is the style for me? What are the advantages and disadvantages of the different styles? I've heard the clam shells can allow some wiggle and rub up the finish for example. Looking to keep price down and place an order soon so any feedback is really appreciated. The absolute safest way to mount a barrel to a receiver is by using barrel blocks. This is also the cheapest.....Bushmaster has USGI type aluminum barrel blocks for about $16 They also have the genuine USGI barrel wrench for $12 Example of the original (and almost forgotten) method.... 
Rubber inner tube or leather scrap can be use for purchase (traction) and protection. With barrel blocks you are also prepared to safely perform muzzle device work. The other fixtures can't make that claim. The next level of safety would be the clamshell w/carrier tunnel plug Billet uppers don't fit in the clamshell. The Brownell's branded clamshell is well made. Then there's the Panther Claw type that bears on the receiver lugs. People like them, but the "Claw" will never cross my threshold because I simply don't like the design where torque is borne by the receiver lugs. |
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That's kinda like a Ford vs. Chevy question. A lot depends on what you're going to do.
Clam shells are really secure and probably the least likely to distort the upper, but you'd need a left and right handed one if you're going to build both. Also, they don't fit some of the billet uppers such as Mega, that different profiles than the standard forged upper. Blocks that slip into the upper and DON'T hold the takedown luhs work on most uppers –– both left and right, but I've heard that under heavy torque the upper may be damaged. Blocks that hold the takedown lugs only work on any upper, but the risk of deforming the upper under high torque is greatest since the lugs aren't designed to take sideways stress. I personally use a home-made block that holds just the takedown lugs, but I put the upper into the vice sideways so that the jaws hold the block and the rail on top. The block is 3/4" thick, so the takedown lugs do not make contact with the vice jaws. RUBBER JAWS, obviously. The problem with this is that it can't be done for an upper with an integrated carry handle. The 35 - 80 foot-pound needed for assembly probably won't deform an upper, but breaking loose a barrel nut may need more force AND the direction of the force puts the greatest stress on the thin area under the ejection port. |
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Well I guess it comes down to clamshell vs. Barrel block. Thanks for the input folks! On a side note, when torquing 3 tunes does one tighten to 30, loosen, then tighten again? It seems that's the procedure but I don't get why. That's the recommended way of breaking in the threads. You have a steel barrel nut meshing with aluminum threads. The softer aluminum deforms (yields) slightly as the barrel nut is tightened. You could go 28, then 30, stop and have a look at where you have to go for alignment. On the last pass go for alignment...don't over run it. IMO I don't think it's the end of the world if you don't do the 3x method. It's far worse if you miss your prime alignment and then try to go for the next notch which puts you in the upper reaches of the torque range. Or not lubricating the threads (with the correct moly grease). Torque range is 30 ft lbs to 80 ftlbs I just did one that aligned at 38-40.....I was happy. |
| Been looking into the barrel block...will this work with multiple barrel profiles? Will it hold the upper assembly securely enough to remove a barrel as well as install? It has some appeal for me because in addition to barrel changes I seem to have just gotten in the mail the absolute most stubborn crush washer ever made...may need a more secure way to hold the barrel so I can TRY to index this thing. |
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I have a block that uses the pins to secure the upper. I have built 4 uppers with it, no problems getting any of them to line up. It won't work on my .22 upper. I am waiting for brownells to ship my barrel block to me. Once I saw the TM I decided I wanted to change, so I could do pistol builds and swap to a FF on my .22.
MAHA |
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Been looking into the barrel block...will this work with multiple barrel profiles? Will it hold the upper assembly securely enough to remove a barrel as well as install? It has some appeal for me because in addition to barrel changes I seem to have just gotten in the mail the absolute most stubborn crush washer ever made...may need a more secure way to hold the barrel so I can TRY to index this thing. The blocks will usually do two different diameters like 3/4" and 1" Some do three diameters. Midway has some as well as Shrub for reasonable prices. Think about pre-crushing your crush washer a bit in your vise or sweeping the narrow side across a whetstone so you don't have to apply a bunch of torque on your muzzle. Muzzle device torque is a low 15 - 20 ft lbs. |
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I tried pre-crushing, whacking with a dead blow etc...no luck. Still times about 45 degrees off. Oh well. I need a block that'd accommodate 300 blk, heavy barrels, 675 etc. Not a good idea. Try using grease on all contact points. Tighten and loosen as needed |
| Im not using a wrench that allows for attaching a torque wrench so i honestly don't know, I've always just done it by feel with no problems. My usgi barrel wrench isn't in yet, but when it is I'll use that and let you know....if I havent figured something out by then. |
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It was greased and all of that. I've used them before but never had one this bad. It just won't give. I've tightened and re tightened...Waaaay more than the recommended torque. Even using all of my strength it still won't "crush". Going to try stoning it What are you trying to crush? Maybe I'm missing something... |
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It was greased and all of that. I've used them before but never had one this bad. It just won't give. I've tightened and re tightened...Waaaay more than the recommended torque. Even using all of my strength it still won't "crush". Going to try stoning it What are you trying to crush? Maybe I'm missing something... started as receiver blocks, after that was figured out, he brought up barrel blocks and he is indexing his muzzle device, so crushing the crush washer 
I bought 3, and DPMS brand seemed to crush easier than YHM, and whatever OPS Inc sends with their brake |
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