Jim,
Don't know what you mean by "gummy." E-Tips are made of gilding metal, the mild brass (copper with 5-10% zinc) that most bullet manufacturers use for jackets on lead-core bullets. Gilding metal is harder than pure copper, so tends to foul bores less. Essentially, they're Ballistic Tips without a lead core. They do raise pressures slightly over, say, Partitions--but in my experience not much--and the lack of grooves on the bullet shank (like those in TSXs and GMXs) results in a slightly higher ballistic coefficient. As with any bullet, once in a while you'll find a rifle that doesn't like them, but I've usually had very good luck in getting them to shoot. My NULA .257 Weatherby averages three 100-grain E-Tips in around .6" at 200 yards in average conditions, and on the rare calm days here in Montana will shoot even better.
