bill_d
10-20-09, 19:19
in these pictures, one can see the often discussed initial setback that occurs in a new bolt/barrel extension combination.
this was a brand new rifle and inspection pics were taken after 250 rounds of privi partisan 55gr ball, 62gr green tip ball, and some black hills blue box 55gr softpoint (250 rounds combined).
take note of the lugs surrounding the extractor slot. they have been known to experience different forces than the remaining lugs.
1. ( this is the problem armalite attempts to address by removing some metal in this area to enable the other lugs to more uniformly distribute the forces around the lug pattern. i think this leads them away from the TDP )
2. (since this is a bcm bolt, we can see how bcm machining techniques address this relationship. i think this is in accordance with the TDP; precise edges and reinforcing fillets , in short, more metal is left in place.)
3.(the knights solution to the bolt stresses involves more and different radius cuts in strategic places ; as does the lmt solution.)
there are several schools of thought on this load bearing lug relationship.
my purpose here is merely to provide a bit of empirical data for visualization.
the pics, that is.
this was a brand new rifle and inspection pics were taken after 250 rounds of privi partisan 55gr ball, 62gr green tip ball, and some black hills blue box 55gr softpoint (250 rounds combined).
take note of the lugs surrounding the extractor slot. they have been known to experience different forces than the remaining lugs.
1. ( this is the problem armalite attempts to address by removing some metal in this area to enable the other lugs to more uniformly distribute the forces around the lug pattern. i think this leads them away from the TDP )
2. (since this is a bcm bolt, we can see how bcm machining techniques address this relationship. i think this is in accordance with the TDP; precise edges and reinforcing fillets , in short, more metal is left in place.)
3.(the knights solution to the bolt stresses involves more and different radius cuts in strategic places ; as does the lmt solution.)
there are several schools of thought on this load bearing lug relationship.
my purpose here is merely to provide a bit of empirical data for visualization.
the pics, that is.