BRIDGE - What to do with 5 or more trumps in my partners (opening) major?
It depends on a few things, but basically you have a choice between a simple raise to 2M or a jump to 4M. First, did partner open in first seat, or later? If partner opened in first seat, your LHO has not had a chance to enter the auction yet and opponents are more likely to have a game. This makes the jump to 4 of the major more attractive. If LHO has already passed, opponents are unlikely to have a game, so the preemptive value of 4M is less useful and partner may have some extras. When partner has moderate extras, you're propelling your side to a shaky contract at best while the opponents are unlikely to find a plus.

Next, what is the shape of your hand? If it's 5332, 4M is less attractive. If it's 5431 or shapelier, 4M is more attractive.

If you decide to bid 2M only, your plan is to bid 3M over opponent's part-score interference and then go away, and not to accept partner's game tries. If you bid 4M, you've essentially shown your hand and you're done in the auction unless partner makes some forcing bid (essentially a cue bid or blackwood).