A dud inner tube?

snaphappyspen

I recently replaced one of my inner tubes with a "self sealing" inner tube from Halfords with a presta valve.

I started to inflate said tube and after a few pumps it was as if i came to a brick wall and it became very hard to inflate. I took the pump off and tried to let the air down and i noticed it was difficult to let the air back out. Is this a common thing with self sealing inner tubes? Is it a dud valve and should i swap it for another one?

cooldad

They are rubbish anyway, just use normal tube.