Carb cap for PET bottles issues

[bt1]

Having some issues with those screw on carb caps for PET soft drink bottles and would appreciate some advice.

Periodically fill 2lt ex soft drink bottles to share brews but it never seems to carb up enough.

Squeeze air out of bottle give it a good belt with the CO2 gas in line so nice and tight, then re chill, repeat and pre icing up swap over to the normal cap. It's not a leak issue it doesn't seem to carb it enough.

Any thoughts?

cheers
a flat bt1

 

[chug!chug!]

I don't need to swap the caps. Just bought heaps of snap in tyre valves and fitting.

My method chill in freezer>air out>40 psi>shake maybe 1 min>freezer to settle>gob.

Your issue maybe swapping the cap not sure.

Good stepping stone to kegging for guys on a budget I use with sodastream setup.

You don't need taps, kegs or a dedicated fridge for similar effect.

Grain to brain 7 days max.