The stock HK-91 has been known to have a good kick.
That's the sacrifice for it's more dependable action.
That being said ,the PTR-91s have a heavy barrel that has 10
internal flutes instead of the 12 in a standard HK-91/G3 barrel.
JLD did this in an attempt to reduce the recoil slightly without effecting
the PTR-91's dependability.
Stock ,my PTR had a slightly lower kick than an HK-91.Just barely,
but it was noticeably heavier to carry.
As for dependability ,I've never had a jam in well over 1,000 rounds.
I've used ammo that most wouldn't even think about putting in their
FALs or M1As.
If you don't like the kick on the HK-91 /PTR-91 there are 3 easy
ways to reduce it.
1.Get a soft rubber recoil pad .HK made these for the HK-21 belt fed.
Aftermarket slip ons are also available .
2.Muzzle break.Some of these are quite effective.Unfortunately they
effect night vision devices and some dot/holographic sites.
3.(My personnal favorite) The G3 Heavy buffer .This is a 2 stage
buffering system.With one of these on my PTR-91 ,my wife enjoys
shooting it ,where as before she was affraid of the recoil.
To be honest ,if you include the HK heavy buffer,an HK-91/PTR will
shoot with far less recoil than any of the other 3 ,and maintain it's
dependability.