打ち

From the verb 打(う)つ (utsu).

打(う)ち • (uchi-) 

1. adds emphasis to the verb, (e.g. 打(う)ち寄(よ)せる (uchiyoseru), 打(う)ち捨(す)てる (uchisuteru), 打(う)ち続(つづ)く (uchitsuzuku))

   不幸(ふこう)が打(う)ち続(つづ)く

   fukō ga uchitsuzuku

   the misfortune continues

2. makes the verb softer, a little bit, briefly, (e.g. 打(う)ち見(み)る (uchimiru, “to glance at”))
3. makes the verb more abstract, (e.g. 打(う)ち明(あ)ける (uchiakeru), 打(う)ち解(と)ける (uchitokeru))

From the verb 打(ぶ)つ (butsu).

• 打(ぶ)っ (bu')
• 打(ぶ)ん (bun)

打(ぶ)ち • (buchi-) 

1. add emphasis to the verb, violently, strongly, quickly, suddenly, (e.g. 打(ぶ)ち込(こ)む (buchikomu), ぶっ殺(ころ)す (bukkorosu), ぶん殴(なぐ)る (bunnaguru))

This term is often spelled in hiragana.