Quote:
Originally Posted by Buffalobob
Gene
I would ask you two questions just so we start at the same point of departure.
1. Do you believe the 175 SMK is stable through the transonic zone as it is my understanding that it is not; although, I have never personally verified it?
2. Do You believe the old M118 SB (173 gr FMJBT) was stable through the transition zone; as it is my understanding that it was, and that was my observation of it?
The official Americal record in RVN with the 308 is 1600 meters (not yards) and the unofficial is further.
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Bob:
I don't think anything is stable through the transonic zone. Not being a wise guy about it. The differences are probably in the degree of instability. I also figure twist rate and velocity would play a role as that determines nutation or precession -- both of which probably have something to do with stability when transitioning.
I can comment on my observations of consistency at 1K though.
I would give the 118LR an edge over the 118 SB at 1K in terms of consistency given shooters who are relatively new to distance shooting. The difference is evident but in my opinion both are more than adequate for combat demands. However, neither are competitive in today's precision shooting sports.
I can say with certainty that 118LR and 118 SB held considerably better at 1K than the old 852 Match. However, that old 168 grain bullet from the 852 had transitioned completely to subsonic under most environmental conditions. Also, the bullet design of that one simply wasn't focused towards performance much beyond 300.
I kind of look at it like this. Maybe one percent of the competitive side of long range shooting will be good enough at those distances where results can be conclusively shown to be due solely to instability caused by transonic passage. So, the 'so what' factor plays a role at least in my terms.
As for a 1600 meter shot with a M-21 and the old 118 Match you guys used in Vietnam. With an ART scope? You are looking at about ten minutes per hundred after 1K meters with that cartridge out of a 21 so somehow the guy held about sixty minutes over? Man, I can't see how the shooter could even see another human with an ART scope at that distance unless they were in a high desert right at sunrise with absolutely no wind or mirage. Not to mention someone being able to spot the shot.
I do defer to Rick or Sinister on the transonic issue and the 118's though. To me, the discussion is a technical one that can't be predicted and certainly can't be changed by the shooter. So, it just doesn't hit the level of importance for my purposes and in my conditions.
Gene