For just the mechanics or reaming,a larger Starret tap wrench,and and a skill of letting the reamer follow the bore,not inducing side loads,I would not hesitate to put the barrel verticle in a vise and do it without a machine.
I have very successfully done it start to finish on rifle chambers before.
If you have a really fine monarch or hardinge grade toolroom lathe(I do not) then the headstock-tailstock relationship can be great to push the reamer
The 1941 South Bend I get to use cannot claim that.Any deflection the tailstock influences to the center of the reamer will be doubled in the chamber,example,deflect the reamer .002 and the chamber dia goes up .004.
And,yes,that is why there are floating reamer holders.I bought one,an Elliot or PTG.It works,and is a great improvement.After I finished that project,I gave it to my local gunsmith.He is happy,and it increased his ability to make money..I lost a tool I can borrow back,and would mostly gather dust.
There is still a moment of deflection as the reamer engages and the torque is transferred to whatever tool is holding the reamer.
These cartridges headspace on the case mouth,you need headspaces gages and the skill to use them.
That discussion was merely on chamber reaming,not on your proposed project.
What you are asking is roughly the equivalent of reaming a Ruger 10-22 out to 22 magnum.
The folks that caution you that you have an unlocked,straight blowback gun that is a balanced package for 40 cal are telling you the truth.
Before you begin,try to find someone with an old Winchester semi-auto in 401 self loader,or .351.The prison warden rifle,it might be an 07,I'm not sure.
They were blowback.My vague memory ,for some reason,tells me the bolt weighed close to 4 pounds.The wood forend is a shell,and inside is where a forward extended bolt,like an UZI,runs.
I have avery fine CZ semi auto 22 magnum they use the same trick,The bolt on that rifle is massive,about 7 inches long,and it rides up in the forend.
It is a beautiful,old school looking hand checkered,nice walnut and blued steel takedown rifle,winchester and rem would have been proud of it pre-64.
It shoots,too.But that bolt,is roughly the size of a 1911 slide.
How a bolt absorbs energy is a function not only of pressure,time duration of the pressure pulse,it is also about the area of the case head.22 mag has far less area than 10 mm.
Paraphrasing "Jaws" You are going to need a bigger bolt"
But,the,it is also a bigger hammer when it impacts receiver.
Your plan is ill advised.
