There is no such thing as a .308 vs 6.5CM bolt.
You can create the same issues in both chamberings shooting longer bullets with slower-burning powders.
You can also have the same problems in a bolt gun, regardless of the chambering.
It has to do with firing pin aperture size to firing pin head size and protrusion.
When pushing modern centerfire rifle cartridges that will work at 58,000-65,000psi and using a sloppy aperture-to-pin head fit, you will get primer cup flow behind the firing pin indentation, called "
blanking", which tries to turn the FP indent from an "innie" into an "outie".
You will also get a blanked cratering effect when you aren't necessarily in a place where you should be experiencing cratering from excess pressure. Many new shooters or reloaders will misinterpret this symptom as an excessive pressure sign, when it is really a sloppy fit, thin-walled primers, or both.
A lot of military rifles are designed with a sloppy fit between the firing pin head and the FP aperture in the bolt, so they can deal with debris and field conditions better after extensive testing in harsh conditions. Since military ammo has crimped, hard primers fired from cases that they don't care about reloading, these issues aren't a concern for them.
On the civilian side, some shooters want to be able to reload their brass and none of us want blanking primers being forced against the bolt face and firing pin aperture, especially on a self-loading, rotating bolt lock-up design that can have pretty extreme rotational loads (torsion) on those critical components.
Have you ever noticed a round area that is worn differently around your FP aperture on your AR15 or AR10 bolts?
This is also why the Military Technical Manuals call for detailed inspection of the bolt faces, looking for uneven wear and pitting in that area.
If you plan to shoot 175gr or longer target bullets in the .308 Win., or 130gr and longer in the .260 Rem or 6.5CM, it's a good idea to use the "high pressure" bolts and firing pins from the same reputable company who actually knows what they are doing, not the ones who copy everyone else because they saw people asking for these things.
JP is the easy answer in that case.