According to R' Nehorai, who says that Avshalom (and any other Nazir Olam) gets a haircut every 30 days,and especially according to R' Yose, who holds every 7 days, isn't the Pasuk (Shmuel bet, 14:26) a problem because it says that his hair would weigh "two hundred shekels by the kings weight" and the braita in Sotah 10b states that this his hair weighed 200 times the weight of the stone with which the people of Tiveria and Tzippori weighed. If I am not mistaken, I believe that Rashi dibbur hamaskil "Midi Hava Taima" (Nazir 5a) explains that the word "koved"-"heavy" is not a problem with R' Yosi because it would mean his hair is "heavy" compared to his brothers- other princes who would shave every week. Still, this would not answer that there is now way his hair could grow to weigh 200 times the rock in 7 or even 30 days!
Thank You
Elisha Yagudayev, FLUSHING
1) The Chazon Ish (Even ha'Ezer, end of 137:1) writes that one should not be amazed that Avshalom's hair grew so quickly, because the Gemara in Sotah 10a tells us that there were give five people who were created like the "Dugma," the form, of "the higher beings." (The other four were Shimshon (his great strength), Shaul (his neck), Tzidkiyahu (his eyes), and Asa (his legs). Rashi in Sotah (10a, DH me'Ein) writes that these were the only five people in history who were physically different, in a magnificent way, from everyone else in this lower world. This implies that the hair of Avshalom was possibly similar to that of the Mal'achim. At any rate, it cannot be compared to human hair.
2) There is another Gemara, in Nidah 24b, which describes how huge Avshalom was. We are told that Aba Shaul, who himself was the tallest person of his times, once found himself in a cave full of buried bodies, and stood up to his nose in the eye socket of a dead body. Afterwards he was told that this was the remains of Avshalom.
3) Rashi (Nazir 5a, DH Midi Hu Ta'ama) is in fact referring to the opinion of Rav Nehorai who says that the Nazir Olam takes a haircut every 30 days. Rav Nehorai learns this from ordinary Kohanim who take a haircut every 30 days so that their hair not become heavy. Similarly, Avshalom's hair would become heavy if he did not take a haircut every 30 days. However, it is all relative, because Avshalom's body was much larger than everyone else's and therefore capable of supporting the hair which weighed 200 Shekel-weights.
Kol Tuv,
Dovid Bloom