I was told not to use high velocity in them because the buffer would fail quickly
You were told wrong. The owners manual says to use high velocity .22 LR ammuntion. I have severeal old {1976, 1990 and 1997} Marlin semi's. They've all had tens of thousands of rounds of high velocity ammo fired through them. The 1997 version still has the original plastic buffer in it. They will all deteriorate/crack/ break over time and need to be replaced. I replaced the ones in my two older Marlins with the black, high strength aftermarket buffers from Brownell's years ago.
