I now use a mixed version of the old and new rules for primitive equipment.

Essentially, primitive weapons use BC and OW rules, capping their damage when attacking a target wearing modern armor but removing the cap if the target is unarmored or only wearing primitive armor because arrows where invented to kill, not to inconvinience.

Conversely, I keep the old version of primitive armor, halving their protection when getting hit by modern weaponry, because if historically the musket made plate mail almost useless I see no reason why it should easily stop a las-bolt, and I don't find halving a single-digit number that strenuous a calculation.

I think this strikes a balance, giving people outfitted with modern equipment a most definite advantage but not so large an advantage as to make them invincible behemoths against a more primitive foe.

Solarisjock said:

But, what's wrong with this? Of course he should be able to withstand a few guys amed with improvised weapons, he's an armoured soldier equipped to fight people with real weapons. Of course peope with lasguns and flak armour will be untouchable by people with bows and arrows.

Are we planning on running campaigns against the Roman Empire or something where this will be an issue?

bogi_khaosa said:

The thing is, real amour does not work that way.
Ignoring the effectiveness of protective vests in general for a moment. There's bullet proof vests and then there's stab proof vests. The former offers little protection against stabbing and the latter ofers little protection against shooting.
I know that 40k doesn't operate by the same rules as our observed reality but still I feel like flak armour shouldn't offer a night inpenetrable high protection against primitive weapons, especially the stabbing types.

Now muskets on the other hand should just bounce harmlessly off of flak and carapace armour.

Musclewizard said:

And then we have kevlar armor reinforced with trauma plates, which is effective against both methods of attack, and considering how prevalent melee combat is in the 41st Millenium, that's most likely how flak armor is designed.