I have been researching tanks for quite a while and i have been under the impression that once the M4 Shermans were upgraded with the 76mm gun M1, they were well capable of engaging Tigers from any standard combat distances.

Now suddenly, i heard of this phenomenon called shatter cap and according to this phenomenon, the 76mm gun M1 could not penetrate the Tiger at anything more than 50 meters.

Is this true? If it is true, do all guns of the time suffer of similar issues?