Hibs
New member
Just got in a New Frontier Armory LW-15 polymer lower, and when I bolted it to my upper receiver, I noticed it has a pretty noticeable gap between the upper and lower receiver. There is NO WIGGLE, both receivers are TIGHT around the front and rear takedown pins, but there is a gap most of the way in between the takedown pins. I measured with a set of quality feeler gauges, and at the loosest point in the middle is .021"..... Should I be worried? Or just leave it? I have handled another New Frontier lower and it had a perfectly flat fitment to it's upper. A quick google search showed me this....
Quote
age 0021-21 of TM 9-1005-319-23&P actually has a set of procedures to check the gap between the upper and lower receiver which deals with lateral flex instead.
Figure 29. Use of Thickness Gage.
1. With the upper receiver attached to the lower receiver, and the pivot pin and takedown pins in place, perform the following test:
a. Apply hand pressure to push the upper receiver as far to one side as possible.
b. Attempt to insert a 0.020 in. thickness gage between the pivot pin lugs of the upper and lower receivers.
c. If the thickness gage penetrates to the pivot pin at all accessible locations, repair by replacement of the upper receiver or replacement of weapon is required.
2. If weapon fails the above test, remove the upper receiver and install a "NEW" upper receiver and perform the test again.
3. If weapon now passes the above test, it shall be considered serviceable and continue in use.
4. If weapon fails the test with a new upper receiver, this failure shall be considered a shortcoming. This shortcoming requires action to obtain a replacement weapon. Once a replacement has been received, evacuate the original weapon to depot for overhaul.
I did not do the lateral flex when measuring. Simply measured as the firearm was sitting there on the desk. Lastly, I want to add, I have tried fitment on TWO different complete uppers I have here at the house... Same fitment (with gap) on both.... Here is some pictures...
Quote
age 0021-21 of TM 9-1005-319-23&P actually has a set of procedures to check the gap between the upper and lower receiver which deals with lateral flex instead.Figure 29. Use of Thickness Gage.
1. With the upper receiver attached to the lower receiver, and the pivot pin and takedown pins in place, perform the following test:
a. Apply hand pressure to push the upper receiver as far to one side as possible.
b. Attempt to insert a 0.020 in. thickness gage between the pivot pin lugs of the upper and lower receivers.
c. If the thickness gage penetrates to the pivot pin at all accessible locations, repair by replacement of the upper receiver or replacement of weapon is required.
2. If weapon fails the above test, remove the upper receiver and install a "NEW" upper receiver and perform the test again.
3. If weapon now passes the above test, it shall be considered serviceable and continue in use.
4. If weapon fails the test with a new upper receiver, this failure shall be considered a shortcoming. This shortcoming requires action to obtain a replacement weapon. Once a replacement has been received, evacuate the original weapon to depot for overhaul.
I did not do the lateral flex when measuring. Simply measured as the firearm was sitting there on the desk. Lastly, I want to add, I have tried fitment on TWO different complete uppers I have here at the house... Same fitment (with gap) on both.... Here is some pictures...
