Q: Can't get a/c system to charge after replacing new components.

Had a bad a/c compressor so it got replaced with a brand new one also drier and orifice line brand new. Added the correct amount of oil, replaced o rings and springs in connections. Made sure everything was connected back correctly. Pulled a vacum for about 40 min and let sit for same amount of time. Good seal so I proceeded to fill with a small can of r-134. About 12 oz I believe. Takes a cans charge only and line turns cold for only a few seconds. Truck on a/c running and compressor kicks on, pressure is about 40 psi. but then spikes up to 60. Temp outside is around 80degrees. Doesn't want to take another can it just won't go in. And if it does take anything it over pressures and causes compressor to cycle from over pressure. High side starts at around 300 and spikes up to around 550. Any advice.
My car has an automatic transmission.