Mark
What do you do with LMT uppers? Ive seen a few in the past and have bought one myself where you can get upgraded LMT bolts/ carriers purchased seperately from the uppers? Do you guys at Questar use a no go gauge or something when you ship out an order with mixed parts like what I said above? Or is it just sold as is? Or because all the parts are from LMT are they somehow checked there and the tolerances are maintained?
If you are buying "parts" then you are building it yourself and it's up to you to check headspace... we might think you are intending to put those parts together... but you might just as easily be intending on putting that bolt into a different upper that you may already have... we have no way to know and frankly it's not up to us to guess or assume. If I was building it for myself then I would personally be quite comfortable putting an LMT bolt with an LMT barrel (factory new items) and shooting it without testing the headspace... unless it "felt" wrong during assembly, the odds are VERY GOOD that headspace will be okay... but it would still be a good idea to check it first and be 100% sure
I've actually spent quite a bit of time speaking with engineers and staff at LMT about their in-house process for headspacing their rifles, uppers, barrels, etc.. they helped us a lot in creating the method we used to headspace our Questar barrels. I won't get into details of how they do what they do, but their barrels are headspaced using effectively three different "test bolts" that were specifically built and designed by them for that purpose. Think of these test bolts as a min and max bolt (both ends of their tolerance spectrum). The barrel is headspaced to the "middle" spec bolt... then tested against the min and the max. If it's correct then it works with all 3... if it's off (in either direction) then it will only work with 2 of the 3 and it is corrected or rejected.
This process is supposed to insure that the LMT barrel will work will all LMT bolts (since the bolts are also tested during manufacture to confirm they are within tolerance specs).
When LMT builds/assembles a complete upper half (whether sold on it's own or as a compelte rifle) that upper half is tested (headspace is checked as part of that process).
If the barrel is sold as just a barrel or the BCG is sold as just the parts then there is no final assembly test since there is no final assembly at the factory.
Having said all of that... mistakes happen... parts fail... tolerances are not always perfect (that's why they call them tolerances)... to simply assume that someone else checked it or it's made to a specific tolerance and therefore doesn't need to be checked is just dumb.
It is VERY RARE that an LMT bolt won't properly fit and headspace to an LMT factory barrel (both parts being new factory units)... but I have seen it happen.
When we built our Questar barrels we spent an inordinate amount of time determining how we were going to headspace our barrels and to what bolt specs/tolerances. We literally used a base group of close to 100 bolts from 2 different manufactures (LMT was one of them) to find the min and max to test against and to determine the middle of that range to set at. These in effect became our tolerance test units for the manufacture process.
It took quite a bit of time and cost us a fair buck doing it but the end results appear to have worked well... we have not had a single barrel that did not headspace to any of our name brand bolts... unless the bolt itself was out of spec.
Mark
