Yeah, I bought all those parts from Bob back in, like, 2006 or so. My main issue was with the actual .308 BBL he supplied, the chamber dimensionality was cut to SAAMI cartridge specs, which wasn't a very good option when running all the various foreign NATO surplus M80-type ball fodder.
I kind of had the same experience you had initially, though it was fairly obvious the chamber was an issue, but I tend to think still that the OOW supplied BBLS were also overweight, considerably, even for the correct 7.62NATO BBL weights which are known to work well (Norwegian issue is still the best). I was almost through making a new BBL chambered with a custom Clymer reamer in the correct 7.62NATO dimensional parameters and contoured to the Norwegian profile, when Folke came up with another few of his original Norwegian surplus 7.62NATO BBLs, at which point I bought several from him then and there and all was fine. I still use the OOW-modified feed block and tray, though it is, to be fair, a hack job compared to the BRP version which only requires a modified front depressor which is a WAAAAAAAY better method.
I think you can get a workable combination if you do either-
1. re-profile the OOW supplied BBL to match a known profile(weight) that is known to work, i.e, similar to the Norwegian conversion BBLs, and then run a finishing reamer back in the chamber (proper 7.62NATO reamer) to re-throat the leade.
2. Pick up one of the newer conversion BBLs that BRP(Poling) is making and use that.
3. Alternately, you could try and get one of the 3-4 people who grabbed all the original Norwegian BBLs from Folke to part with one. ;-)
It really isn't too hard of a problem to solve, as long as you are confident the modified feedblock and tray are not giving you any presentation issues as they exist now; If they are presenting and feeding the shorter cartridges satisfactorily now, then all you really have to do is achieve a dynamic energy balance, which is likely centered on these overweight BBLs needing to be relieved in profile to lose some mass to match the available energies. Caution- DO NOT go trying to restrict the booster nozzle orifice below ~9.0mm, that is NOT the problem......if you increase the dynamic system recoiling energies on the front end, remember, they have to accounted for on the back end, and the stock MG34 buffer system is NOT designed for dealing with excess energy, over and above the std 8mm original wartime BBL mass and velocity it was designed to be accelerated (and thus DECELERATED) at. Your goal should be to match the accelerated mass energies of the std 8mm set-up while shooting the sharper recoiling NATO round, that means the NATO caliber BBL mass will need to be made to give that harmony. It can take a bit of experimenting.
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