Yes ... the softer metal tubes (brass tubes) can expand a bit when the pen components are pressed in.
If you are working with unyielding materials, like stone pen barrels, then you will want to sand down the components where they mate up with the tube, or ream/sand out the tubes for a much looser fit, and locktite them in place rather than press fit. The pressures of a press fit will crack most types of stone.
Alternatively, attempting to press parts into a much harder barrel material could give you headaches later ... even pressing a part into an all-brass barrel was a major issue for me, recently!
The pen I sent off to Doug (Alankulwicki) was a gold finished slimline in solid brass .... each barrel (upper and lower) was composed of 51 separate 1/4" brass washers press fit on the brass barrel (reamed out with 1/4" drill bit till they barely slipped onto the barrel). After the turning was finished, I coated the barrels with CA and gave it a matte finish ... if the CA were removed, you'ld see a highly polished finish on the pen. Pressing the parts to the pen were extremely difficult, as the brass barrel was now reinforced by a LOT of solid brass, and simply didn't want to move. At several points, I was afraid I might not be able to even press the twist mechanism in far enough, but it went in, in the end. That pen will very likely fail to properly disassemble, even with the appropriate tools and kits, it's just way too tight a fit.
Attempting to press your parts into a solid steel barrel would give you similar headaches ... I don't recommend it.
