I am planning to build a 7.62 x 53R (7.62 x 54R using .308 caliber bullets.) Will there be any issues using RCBS standard 7.62 x 54R dies with a 30 caliber expander.

Not per se, no.

However, "standard" dies are frequently incompatible with "standard" chambers. This is more often true with custom chambers as custom reamers tend to be closer to minimum dimensions than reamers used for bulk chambering jobs.

Off-the-shelf RCBS dies will most likely work just fine with your custom chamber, but there is always a chance that they might be slightly different in one or another dimension.

Ok, but from personal experience with the 7.62x53/4, with 308 bores and bullets, and my PTG reamer, there is absolutely no problem. I have not noticed that SAAMI spec reamers from any of the usual makers are smaller.
If you want a smaller reamer you have to order a custom one to your specifications.
And I have 85 of them....

What prompted my question is that I seem to remember hearing that the RCBS sizer does not reduce the neck diameter enough, resulting in loose bullet tension even when using a 30 caliber expander. CIP dimensions vary slightly between 7.62 x 53R and 7.62 x 54R but except for bullet diameter are mostly within the tolerance range of each other. The Mason reamer that I plan to use (per them) is a 7.62 x 54R with a 30 caliber pilot.

Yes but I bet the neck is for a .311 bullet in order to use any ammo. Check it out. My reamer is made like that.
With a long tapered leade.
And American reamers are not made to CIP standards.
My die, does hold 308 bullets tightly.

I shoot a lot of cast bullets and generally have to ream and polish the necks in my size dies to avoid over working the case necks.
almost every '31 cal' size die I have ever used is 30 caliber in the neck area, and tight 30 cal at that.
if they weren't you wouldn't be lubing the inside of your case necks to get them back over the expander ball.

Right. I find the same thing.

No need to build the rifle for this caliber and bullet diameter. Find a Finnish Mosin Nagant 28/30 the barrels are .3082. I use .30 bullets and it's a 1"-1.5 groups in my 28/30.

SAKO uses the same bullets for 7,62*54r and 308w.

https://www.sako.fi/sites/defa...2018_datatable_0.pdf



The original Finnish name of the company was Suojeluskuntain Ase- ja Konepaja Osakeyhtiö (Firearms and Machine workshop of the Civil Guard).