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Posted: 6/30/2008 1:40:26 PM EDT
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So I have a DSA Type 1 upper that is about 5 years old. From the factory, the receiver had a larger than .294 diameter hole for the locking shoulder which I discovered recently while installing a new barrel. So I order a custom LS from DSA and wait a month, no big deal. LS arrives today with correct OD for LS hole on receiver, yet LS is .258 when I ordered a .260. Needless to say, Bolt will not close on GO gauge, this is how I discovered I had the wrong size shoulder. Having an all around bad year, and sick of waiting, I chucked the LS in the vise and began to slowly remove metal on the area where the rear of the bolt locks and have opened it to just shy of.260. I pushed the shoulder back in, and now the bolt does close on the GO gauge, but a little snug. I can push it in with one thumb, but I am not weak. I don't want to go too far so question for the experts is..... Is it safe and acceptable what I am doing? File more off the LS or leave it where it is? I still need to tap the BC out through the gas nut hole, but I can close it on a GO gauge at this point. Opinions from serious builders welcome. ETA: I thought about what I posted above and realized I was headed in the wrong dimension. I now have the GO gauge closing and opened the LS up to around .255 not .260 like originally stated. The BC closes on the LS now with a firm press of the thumb but will not close on the NO Go gauge, I would think I should be ok with what I have done here. I still have to grab the rat tail with pliers to pull it loose, but it closes really nice on the GO gauge now. Any thoughts? |
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I don't understand. If the bolt wouldn't close on the .258 LS it certainly won't close on the larger .260. You should be able to close the bolt on the Go with minimal pressure on the bolt. Too much needed, then your headspace is too short. If you shoot it, you can damage the weapon or yourself due to exceeded chamber pressure. |
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Your head space, as described, is way too tight. When set properly, you should feel a slight resistance when closing the BC on a GO guage. I understand that desire to get it built and being sick of waiting, but please buy a new LS. Maintaining a critical angle like the one on the locking shoulder is IMPOSSIBLE with a hand file. It may work for a while, but you are setting up a problem "down the road." |
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Yeah I hear you guys, and yes if it wouldn't close on a .258 I am only growing it longer with a .260. What I have determined here is that since the O.D. of the hole is larger than the standard .294, you have to take that into account when ordering a locking shoulder because the thicker LS will push the BC further forward. So, if the rifle headspaces on a .260 pin, that would be assuming you are using a LS with a .294 O.D. However, since I need a .298 O.D. LS, the .260 LS would now become a .256 LS? I have been a long time DSA fan and blame them in no way, but the LS hole being so out of spec really pisses me off. This has been a problem with this receiver since day 1. anyone know a good way to figure out the actual LS headspace size if using an oversized LS? |
relax dude....you're still in the ballpark and don't need to order any new parts.  I had the same problem with my DSA when I rebarreled it last month.....my original locking shoulder was a .262 and I needed a .257. I also needed a slightly larger LS and got one from the FALfiles marketplace.....turned out that it wasn't the right size, so I broke out the files and started hacking on the original.eta: Hebrew is correct--it's not easy to maintain the 11 degree angle.....but plenty of people have done this and you're going to get a mix of opinions--obviously, having done it, I disagree with his assessment.....but I'm confident that I did it correctly. A little Sharpie on the bright metal only proves that I maintained a nice, even cut.....if you have the patience and skill to use a file, go for it...if not, you need to order another locking shoulder. 1.630 is the minimum headspace for commercial 308. (also the same size as the Forester GO gauge) If your bolt closes on it, it's safe to shoot.....as tight as it is, you may have some feed problems, but you're not going to separate any case heads. A Forester NO GO is 1.634"....since it's obviously not closing on that, you know that you have at least .004" of wiggle room to file on your new locking shoulder and still be safe to shoot commercial 308. The minimum 7.62x51 headspace is 1.632", max is 1.636"....which leaves your target locking shoulder size .002" smaller than it is now--this will give you a comfortably safe headspace for commercial ammo and enough slop to reliably feed surplus. |
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