It depends. A '.22' rifle, if you mean centrefire, includes alot of calibres as the term is generally used to mean any ammunition loaded with a .224 calibre bullet.
Such calibres include .222 Rem, .223 rem, .22-250, .22BR, .22 Dasher and plenty of others.
Of these, the .22-250 is by far the most powerful. It is essentially a .250 Savage case necked down to take a .224 bullet and so holds alot more powder than any other '.22' round.
In terms of foot pounds of energy, a .223 Remington will generally produce about 1,200 FPE whilst the .22-250 will produce about 1,750 FPE.
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However, if by "22 rifle" you are referring to the RIMFIRE .22, such as .22 LR, the .223 is much more powerful.
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