I believe the 6.5mm 130gr SMK use to be HPBT then when "new management" took over, belive they got bought out, they changed a lot of the SMK to a Pointed Or Closed Nose HPBT to squeeze a lil more BC out of them. They may still offer them in HPBT as well, but the newer bullets(probably y ur 2nd box had the new designation) are a Closed Nose HPBT. Hince the HPBT-CN abbreviation. I'll attach a pic from Sierra's website saying they have some SMK now in the HPBT-CN, Pointed or Closed Nose. It is only done to the MatchKing line though as it's purely to squeeze tad more BC and supposedly accuracy.
I have 2 boxes of the 130gr HPBT-CN from 2 dif lots, and they are no where near .038" difference between them. After checking 10-20 of each box I had a avg. of .002-.003" dif, so maybe .005" dif I could see but gotta think the almost .040" dif is probably due to the change to the meplat/nose if its OAL ur referring to, if base to o-give then when made new process or whatever they may slightly changed the o-give to be more streamlined and a closed nose but doesn't technically have the new .27cal degree o-give like the newer 6.5mm 150gr & 22cal. 95gr SMK have. I've seen the 6.5mm 142gr SMK & .22Cal 80gr SMK starting to have a closed or pointed nose. Also the BC the guy said the Sierra Tech told him is the same as what's on their website for it lol.
I would guess it's the only way they r making them now tho, as well as probably most semi-popular & up SMK bullets r being transitioned to a pointed or closed nose to get lil more BC and try to keep up with Berger and etc.