How do I avoid pipe distortion of PVC joins

[urbanfarm]

Have joined some pipe - PVC Class 12 50mm (OD 60.35 ID 53.7)
to a T for a piston design however the pipe seems to squash in an oval fashion by a few 1/100 upto maybe a mm so my original piston no longer fits and any piston that does fit will not be as great as could be achieved if the pipe dimensions could somehow not be so distorted when joining.
I have made a working piston now however it is not the precision one hopes for, hopefully something can be learned from this.

Anyone be able to help me out here? or is it unavoidable?

Less primer...more primer... less glue?????

I currently cut pipe ends very neat and square with a dock saw, and the most major distortion does occur at this point naturally perhaps I should file the inner pipe before joining so a smaller lip is created?
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...............\ like this? although I am thinker sharper will be better, anyone figured it out?

I am no noob when it comes to pvc joining either however my previous plumbing projects never demanded this precision.....

edit: been thinking about this and think the best solution may have been to use a snap on T, lesson learned I think... but booohoo my 1st project is not perfect....However the original question I think is still worth answering.

PS: looking forward to seeing some snap on T piston housings to make me jealous... ohh man the precision you guys will get...