Upper Receiver Vise Blocks

[niner]

What is y'all's preferred upper receiver vise block when installing a barrel. I am sure y'all know I am deciding which barrel to get, and when I do I need a good quality vise block. My upper I am installing the barrel on is the MUR-1A (if that matters) I think I am leaning toward the Block-Worx or that DPMS block, or something similar. Any opinions out there?

Thanks!

[tac40]

Our armors use both the block-worx and the Brownells.

http://www.brownells.com/.aspx/sid=53369/pid=25011/sku/Action_Block_Vise_Block_Set

I have used both and they work great, no experience with the DPMS stuff.

[Quib]

I use the Upper Receiver Vice Block offered by Bushmaster. No complaints to report of.

http://farm4.static.flickr.com/3504/4075685413_42efc41a54_o.png

[spamsammich]

Any concerns with using a clamshell type block with a MUR?

[John Hwang]

I'm not a fan of a clam shell block as it can mar up the upper receiver. I have used the DPMS panther claw with some success but my favorite is the PRI block.

[spamsammich]

;) I never sweat a little plastic on my receiver, it usually comes off with brake cleaner and a bit of elbow grease.

[Quib]

If the very light evidence from the clam-shell bothers someone, a paper towel placed between the receiver and the vice block will eliminate the marring. I personally never found it an issue. If assembling weapons for a customer, I could see it being a concern.

[rob_s]

The BM clamshell conflicts with most of the nuts on FF rail systems. I had to grind on mine for days to make it work.

I found this guy on gunbroker and ordered a few of his things. He uses bolts instead of clevis pins to save a couple of bucks but I've been working with them for the past couple of weeks and am happy with them.

http://www.gunbroker.com/Auction/SellerAuctions.asp?User=1352096

with the blocks like this (http://www.gunbroker.com/Auction/ViewItem.asp?Item=145791690) you can either clamp the block in the upper, or turn the whole thing sideways and put a block up wood between the upper rail ad the opposite vice jaw.

The other advantage to this kind of block is that you can use it on 9mm uppers without removing the brass deflector. This was originally the whole reason I wanted one but now I prefer it over the clamshell.

On his lower blocks he's going to start making them so that you can insert it from the top which will be a nice tough for working on the lowers.

I'll have some photos of the upper and lower block on my site soon.

[Quib]

Reference the link above: I’m not sure I’d use that upper receiver vice block for barrel work.

Although it attaches and holds the upper receiver in the same fashion as the DPMS Panther Claw, using the upper receiver pivot and take-down pin lugs, it lacks the internal support structure of the DPMS Panther Claw.

Without the internal support structure that the DPMS Panther Claw offers, all the stress from torquing or loosening the barrel nut fall onto the upper receiver pivot and take-down pin lugs. My concern would be over stressing those lugs.

Here’s the DPMS Panther Claw for comparison (See below.). Take note of how the Panther Claw inserts into the upper receiver. This center support section absorbs the stress from torquing or loosening the barrel nut. The pivot and take-down pin lugs with their clevis pins, simply keep the upper receiver secured to the Panther Claw.


http://img.photobucket.com/albums/v489/Metroliner/pantherclaw.jpg


There was a gentleman on ARFCOM who was questioning the upper receiver block offered by PRI, for use doing barrel work (See link below.).

I cautioned him as well, referencing the Panther Claws additional support structure, and PRI’s lack of it. In PRI’s description they also do not mention that their block can be used for barrel work, but rather for sight adjustments or cleaning.

http://www.pri-mounts.com/mm5/merchant.mvc?Screen=PROD&Store_Code=PRI&Product_Code=05_0083&Category_Code=TOOLS

[federalist22]

I have used the DPMS Panther Claw in both .223/5.56 and .308 to install DD Rails on a few rifles. I have not used other receiver blocks, but the DPMS Panther Claw was very sturdy to use for torquing the barrel nut down. The other thing I like about the Panther Claw is that you can secure it in the vise to your liking--tight enough to do the job without worrying about your receiver being squeezed.

[John Hwang]

I can see where there could be concern not having the internal support for the PRI. Since the bottom of the upper and the lugs, it sits securely to put up to 65ft/lbs on the barrel nut. Building as many uppers we build each day, I can tell you with confidence it's not a concern on 98% of the uppers we touch. We do get uppers and rifles that were put together by gorillas that have over 85 ft/lbs on the barrel nut and we choose to use a clam shell style block. The PRI because its steel construction will not flex like the DPMS panther claw. Over time the DPMS panther claw will begin to warp in the lug areas with all the torquing required on upper receivers. For most Joes, it's a great block and probably a good choice for most enthusiasts. If you are a gun smith or build a lot, then you need more than 1 style.

It is important to note on the PRI that the lug area needs to fit pretty tight (not uppers do). Since the PRI mounts on the lugs, the area needs to fit pretty well on the block. We have 4 different type of upper blocks and they all get used but all of us who build on a regular basis continue to go back to the PRI because it works.

[Quib]

Don’t get me wrong, I’m not questioning your experience. But I’m just not convinced that the receiver blocks that only attach to the upper receiver via the pin lugs are the right way to go.

I don’t believe the upper receiver pin lugs were designed to take the kinds of stress loads they see utilizing those vice blocks for a barrel job. One might get away with barrel jobs and never see any stress fractures present in the lugs, until they fail at that one crucial moment.

I’m far more comfortable utilizing a receiver vice block that evenly displaces the stress throughout the upper receiver verses concentrating it on two thinly machined lugs.