Newest Rig Finally Done! (UPDATE: Small Issue Found With This Configuration Pg. 3)

OZZ said:
LMT sounds full of s**t to me, when you leave extra height 'speed bumps' to take up slack you are then not making your upper milspec, right?
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Milspec is not a percise measurement by any means, each component may have an acceptable tolerance of plus or minus of a hundredth of an inch, so parts can be oneside or the other from the nominal measurement , yet still be called in "spec".

When they say "match or blueprint" a rifle, in a nutshell they goes through buckets and buckets of parts to find pieces that has the lowest tolerance to each other as possible, sometime you will have to go as far as refinish the mating surfaces to get it as tight as possible.
 
hbean said:
Milspec is not a percise measurement by any means, each component may have an acceptable tolerance of plus or minus of a hundredth of an inch, so parts can be oneside or the other from the nominal measurement , yet still be called in "spec".

When they say "match or blueprint" a rifle, in a nutshell they goes through buckets and buckets of parts to find pieces that has the lowest tolerance to each other as possible, sometime you will have to go as far as refinish the mating surfaces to get it as tight as possible.
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I get it really but like I said if you design extra height "speed bumps" then your asking for this kind of trouble.

My way of knowing which is 'more out of spec' :) would be to try both offending upper and lower with different uppers and lowers. If LMT uppers only work with those companies listed above then they should say so from the start.
 
50calshooter said:
This is true. I believe now that Questar will make mention of that on there website im sure..
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For as long as we've been selling the LMT uppers (including the MRP's) you are the first person (I can remember) to indicate any problem in mounting their upper to a lower... and with all due respect to Rick and his lowers, his lowers are not "name brand factory lowers"... they are very small-run units that are made to Rick's specifications... he has set/chosen the dimensions and the tolerances used in manufacturing the lowers he produced... they may or may not have been set to any actual Mil-Spec.

If I remember correctly, back when Rick started shipping his lowers there was a thread on Gunnutz that had at least one person who posted he was having "fit" issues with his upper on the ATRS lower. We have also seen this on occassion with some billet machined lowers (Tactical Innovations were also very tight and we experienced some instances where certain brands of upper did not fit properly... they were too tight).

The LMT product is actually produced to a Mil-Spec (as supplied by DoD contract and as tested and accepted by them).

I think if you had tried that LMT upper on other name brand lowers (prior to modifying it) you would have found that it fit without issue.

Even with all of that said... let me again remind you what LMT said in their email... remember the issue of tolerance stacking when you talk about fit problems between "Mil-Spec" parts. It is not that uncommon to see various AR sub-assemblies and parts that don't "fit" properly due to the issue of tolerance stacking... where two components that are both technically within the tolerance allowances but because they are at the extreme outside edge of the allowance don't fit each other as expected or required. We see this on occassion with Rails and Sights/Mounts... bolts... and sometimes with receivers.

With respect to the LMT MRP uppers I have yet to experience an issue mating them to any name brand factory lower (except of course the oversize pin Colts).

Mark
 
Questar said:
For as long as we've been selling the LMT uppers (including the MRP's) you are the first person (I can remember) to indicate any problem in mounting their upper to a lower... and with all due respect to Rick and his lowers, his lowers are not "name brand factory lowers"... they are very small-run units that are made to Rick's specifications... he has set/chosen the dimensions and the tolerances used in manufacturing the lowers he produced... they may or may not have been set to any actual Mil-Spec.

If I remember correctly, back when Rick started shipping his lowers there was a thread on Gunnutz that had at least one person who posted he was having "fit" issues with his upper on the ATRS lower. We have also seen this on occassion with some billet machined lowers (Tactical Innovations were also very tight and we experienced some instances where certain brands of upper did not fit properly... they were too tight).

The LMT product is actually produced to a Mil-Spec (as supplied by DoD contract and as tested and accepted by them).

I think if you had tried that LMT upper on other name brand lowers (prior to modifying it) you would have found that it fit without issue.

Even with all of that said... let me again remind you what LMT said in their email... remember the issue of tolerance stacking when you talk about fit problems between "Mil-Spec" parts. It is not that uncommon to see various AR sub-assemblies and parts that don't "fit" properly due to the issue of tolerance stacking... where two components that are both technically within the tolerance allowances but because they are at the extreme outside edge of the allowance don't fit each other as expected or required. We see this on occassion with Rails and Sights/Mounts... bolts... and sometimes with receivers.

With respect to the LMT MRP uppers I have yet to experience an issue mating them to any name brand factory lower (except of course the oversize pin Colts).

Mark
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Sure, but it's still worth mentioning is it not? I mean I had this ATRS lower mounted on several uppers, Stag, DPMS, Bushmaster etc. they all fit fine. Again as the fellow from LMT suggested both the MRP upper and billet lowers have just too tight of tolerances. Don't get me wrong Mark once this was all explained to me it all made perfect sense. As said before I will do this build again because I like the idea of these two manufacturers together. Thats what building AR's (to me) is all about, I took two of the best products offered today and combined them. It wouldn't have been the same if I just slapped any ol' random lower on it, it's a pretty unique setup to say the least.

I think this discovery has merit, the public should know that they may have issues with this type of configuration. (before they buy) I apologize if I came of sounding like I was trying to bash LMT or Questar. I was just trying to be a helpful gunnut is all.
 
That's really the crux of the matter - mating a tight tolerance match grade lower to a milspec (whatever the hell that means) upper. Personally, I'm not surprised that there were fit issues, neither having to do with the quality of either part.

FWIW I would have modified the upper as well as opposed to fooling with a match grade lower. But that's just me...and 50calshooter, apparently.
 
Modifying Stuff: The unwritten rule is to "modify" the cheaper of the two parts 'cause once it's "chopped up" it's lost more value (not to mention if you need to replace 'said' part).
I've learned this the hard way. ;)

Either way, nice build and as long as you are happy~ it's all good.
 
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