Years ago HK advised against shooting 158gr in the HK94 due to higher recoil impulse, by inference may also apply to CA89K. Probably will only increase the wear rate and pounding on the receiver, if it was me I would shoot in other guns that don't have a second hand warning.
I shot my MP5 on full auto with 158gr Fiochi with a suppressor while at jeffs and it was dead quiet. I did not notice a large increase in recoil nor cyclic rate. These guns are overbuilt as it is. I would not worry too much about it hurting anything.
This has been discussed many times on subguns. The manual says not to shoot it because of higher pressure. I asked one time if I could shoot it in my Beretta 92. Dr Dater of gemtech said not to do it. If you do shoot it keep track of the bolt gap, and watch for roller marks on the side of the receiver. I've got 3000rnds of IMI bluetip 158 that I would like to shoot, I guess I'll have to buy an UZI to shoot it in. I still don't know why you can shoot 40cal and 10mm in the mp5's but not 158g.
I am sure any roller locking gun will be quite fine. You can throw your MP on the ground, stomp it, throw mud in it, and it will still shoot. I shot some very underpowered loads through mine one time and the worst thing that happened was when I was firing sideways. A piece of brass flew out, bounced off a barrel, and then fell back into the ejection port at the time I fired another round. Million to one odds that would ever happen again. The thing fired two more shots before working the brass into a spot where it cause a feed problem... the thing is sick.
Through my "old style" Octane HD, I've used the Fiocchi 158s in both my BW5 and my SIG P239. I used it sparingly in the BW5 for concerns of breaking the roller retainer. The ammo shoots very quiet in this combo, but then again so does any subsonic ammo. In the SIG, I had a dramatic POI shift using this ammo through the Octane. I'm talking like 6 inches low at 7 yards. I found that the powder used is not very clean burning. I was getting a LOT of powder and carbon backsplash in my face. Combined with the extremely dramatic POI shift, I won't ever buy this ammo again.
The Federal AE 147s meet all my needs for the Octane on the MP5 clone and the SIG pistol. It runs cleaner than the Fiocchis and the POI shifts are negligible. Until I can find a comparable load in bulk for less money, I'm sticking with what works, and it's not 158s!
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