Blanksguy wrote:Der Alder,
On the subject of the MG3 FH and Barrel-Bearing..........knowing the added weight for the SA42 Bolt-Assembly that will probably end up being the "challenge" that must be over come............would it be better to suggest the switching back to MG42 FH, Booster-Cup/"Nozzle", and Barrel-Bearing as jbaum and I have suggested (?). The MG42 parts being more adaptable/adjustable by switching parts......that added advantage of Booster-Cup/"Nozzle" being able to be changed (?).
Regards, RichardS
US Army, Retired
The MG42 8mm type is much more tuneable and that's exactly what I'd do at this point.
My thoughts are that the one peice MG3 FH'er combined with it's barrel bearing (which the OP has) is desiegned to work with 7.62 NATO ammo. Provided he is using mil-spec 7.62, it should fuction...unless there is a problem else where.
Which is why I mentioned looking for binding and such earlier. These semi's run right on the edge of fuctionality at best. It dosen't take much to cause issues and going to a lower power caliber can bring issues to light, which of course over boosting can sometimes over come.
Things I would check; binding on rails, hammer clearance, make sure the recoil spring is seated properly (which can matter on a semi), run it wet, try different ammo and belts. Being that it ran good in 8mm maybe switch back and run a few hundred rounds through it and break it in before switching calibers.
Part of a good tuning kit should be various size booster nozzles, but another thing that is often overlooked in these semi guns is it can be helpful to have various size recoil springs lengths in your tuning kit. The added weight and length of the semi bolt carrier plays a big role in these semi guns. Springs are pretty cheap so it doesn't hurt to have a few on hand.
I have several that are a coil or 2 longer and or shorter. If it is short stroking try a shorter one (less spring=less resistance), if its not going fully into battery or needs a lttle umph stripping rounds try a slightly longer one. But again this is only after you make sure there is no binding elsewhere that you could be masking. Just don't go too long to where it binds on full recoil.
I even have firing pins that vary in sizes. JBaum used to sell a nifty FP gauge set and I used that to make several FP's within its range which can fix ammo related problems. Thing is the tuning phase of these guns is often the trickiest most time consuming part and changing ammo types can make things more complicated. I'd find a good base line with the 8mm set up and 8mm ammo being that it ran good with that, run a few hundred rounds through it and go from there. Just my 2 cents.