This is an old thread but I find myself facing similar issues to Kepo. I am new to competitive shooting and, perhaps rashly, decided to go straight to an STI DVC Open gun, seeing as my eyes are not getting any younger and I really like using a red dot sight on another type of pistol. I went for the 9mm version due to the fact that .38 Super ammo is hard to find and expensive in Thailand, where I live, but I didn't do quite enough research in advance and was foolishly unaware that the gun might not run on minor ammo. Unfortunately, hand loading is not a legal option for private gun owners in Thailand and there is no Atlanta Arms or other major 9mm ammo imported or produced locally of which I aware. So far I have tried the gun with Speer TMJ and Magtech FMJ 115gr ammo and it seemed to run OK and I was very happy with the gun. Next I tried it with some locally manufactured 124gr FMJ and it stove-piped 3 or 4 times on each mag and made a nasty mark on the underside of the scope mount. I haven't chronoed the local ammo yet but Thai manufacturers don't comply with SAAMI specs and I suspect it is underpowered. I was hoping I could get this local ammo to run in the gun, assuming it has enough power to make minor, since it is the only brand that is readily available at ranges here, as well as being a lot cheaper than imported brands. So I started looking into whether a 7lb recoil spring might resolve things. I asked STI about a 7lb spring with shock buffer and got a prompt reply as follows:
"The factory recoil spring in a 9mm DVC Open is an 8lb spring. It might run minor ammo with a 7lb spring however it is unlikely. These pistols were designed to run on major ammo and in order to guarantee function with minor ammunition you would have to send it in for a “minor tuning package”. This would include the recoil spring and all modifications in order to run production minor ammunition. STI does not recommend shock buffers; they redirect the stop point of the slide onto the spring tunnel, which will crack over time and will not be covered under warranty. Price for the minor tuning package on a DVC Open in 9mm would be $285 + $90 for round trip shipping."
Unfortunately, legal obstacles in both countries prevent me from sending the gun back to STI, although perhaps the $285 minor tuning that the importer might have considered having done when ordering the 9mm guns. I don't trust local gunsmiths after some nasty experiences and few of them have more than basic expertise. If I lived in the US I would gladly buy Atlanta Arms major ammo or hand load but I guess my only options are to stick to whatever imported ammo I can find or try a 7lb spring, even though STI advises it is unlikely to help without their minor tuning package which is not option. Another option might be to try to get hold of 90 degree scope mount.