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We tested various brands of 45 acp jhp in 3 different 1911s. Winchester xpd1 (I think), Remington golden saber, black hills, federal hydrashocks, and Speer gd dots. We were using colt defender, colts series 80 government model, and rock island armory. We got good results from the colts. The RIA seemed to have bullet tumbling issues very consistently. We were shooting into phone books and magazines. We're we're not testing for effects of bullet in body like gelatin or anything like that. We're we're just comparing differences between 5" and 3" barrels. My questions are: would cheaply made or defective barrel cause this tumbling problem? Would it necasarily make it inaccurate? It is an accurate gun. Or does the tumble begin upon impact? And if so why did the colts never have the tumble issue? Thanks in advance.

when you say tumble do you mean that they keyholed going into the target? Usually such a thing can happen in guns that cannot stabilize the bullet you are lobbing out.

Check the bore of the Rock Island. If the rifling is leaded up, or if it just is too shallow, those are two of several reasons why rounds might be tumbling.

My BUG had a similar problem, sent it back to the manufacturer (what a hassle) and got it back with a different barrel, which works every time.

Just a guess, but it could be the bore diameter. Certain Colts are known for having a tighter bore [smaller than nominal diameter] than other manufacturers.

What Jim said. Check the barrel on the Rock Island it may be cruddy, shallow rifling, or shot out. The barrel on my XD started keyholing after about 25,000 rounds espedially with lead bullets. A new Storm Lake barrel cured the problem.

The things one can learn by just browsing around on this forum.