Re: Question on body taper.
+1 JE CUSTOM
I taper .010" per inch of case body when I fill out a reamer order form.
This has worked fine for me.
It is possible to go totally straight, but you would be more limited in pressure potential for the cartridge. On firing, a chamber expands similar to brass, but it definitely springs back fully, or your in trouble! Not always so with brass.. And that chamber can springback to an interference fit with brass that didn't.
With no taper, under highish pressure, the body nearest the web(thicker brass) would springback more(by relative percentage) than nearest the shoulder(thinner). So the case would be held by the chamber walls near the shoulder and drag out. Would not rechamber at all without FL resizing.
But this would only occur with high enough pressures to cause brass yield(some loss of springback), or over annealed cases(too low on the body).
Now high pressure to me might be common for someone else.
But keep in mind, with enough pressure, even well tapered cases 'pop' on extraction because the brass web area can actually yield(it is technically ruined). This is often used as a pressure sign. With some cartridges, it is very accurate.
These are now cases with loose primer pockets..
An advantage to low taper, and high shoulder angles, is reduced case lengthening. Long cases with high taper require constant trimming, and occasional donut reaming. As mentioned, these can also affect bolt pressure.
I don't like shoulder angles under 30.
So far, I have never needed to trim a reload, and shoulder bumps take and hold with precision.