From http://forums.gunboards.com/showthread.php?228684-Debugging-tips-for-the-Star-B-and-BM
By Begemot.
Debugging tips for the Star B and BM
paul c and I have conducted a fair amount of research on feed jams in the Star B and BM pistols. We're planning to put together a formal guide, but haven't had a whole lot of time to devote to the project recently. I've noticed a steady trickle of questions related to the topic over the past few months, so I got Paul's okay to post a brief digest of our findings for those of you who are struggling to get these guns working properly.
I'm going to hit this fast and furious and I won't be taking the time to back this up with the data or the names of all the folks who helped us get this sorted out at the moment. You'll have to decide for yourself what to think of it until I can find the time to do this thing right. However, I would like to start out by thanking Lew Curtis and John Moss, of the International Ammunition Association, for their research assistance and for their patience.
The main problem with the Star B -- and you'll see this much more often with the Bulgarian Contract re-arsenalled guns -- is that the magazines may latch in too high. If you're getting failures to feed and / or to extract in which a partially chambered live round or spent case is jammed by the live round below it, then I can almost guarantee that your mag is seating too high.
Measure the height of the mag feed lip above the frame rail with the mag seated and pressed firmly down against the catch. Our experience is that if the mag latches in at near full insertion, as it properly does in the Star A, it will be too high in the Star B (or BM).
Although I can't give you a solid number at the moment, I've had success in adjusting mag seating height to around 1.25mm. As metal is easy to remove, but tough to put back, I'd reccomend you aim for 1.5mm, test, and adjust downward from there. If you don't see significant improvement in reliability by 1.25mm, PM me and I'll help you figure this out.
Another problem with the B is that the magazines allow for instability to develop in the cartridge column, because they can slop around foreward and rearward quite a bit. If you can find the factory blocked mags that Star developed early in the war, snap them up. They should remedy this particular problem. According to Antaris's book, Star stopped blocking the mags because it was an added expense in production that they thought they could do away with. Fact is -- the B needs an internally-blocked mag for high reliability.
You can make your own mag blocks and install either Norinco 213 followers and springs or Astra 600/43 followers and springs into them. They work like a charm. I'd be willing to bet that 9mm M1911 followers and springs, and probably a few other substitutions would work just as well, but as yet i haven't tried any others. I cut my mag blocks out of 1/8" mild steel. Cut them so they are just narrow enough and short enough to fit snug all the way at the back of the inside of the mag body. Radius the edges, and don't try forcing them into place. A bench grinder helps a lot with this job, btw. Now that you have the block fitting the full back of the mag, use something like a dremel cutting wheel and needle files to cut a two-tined "fork" at the top of that mag block. This will allow the slide to move freely between the mag feed lips. This may take some sweat and cussing, but it's very straight-forward and very much worth your time. Do not permanently attach the block. It will stay in place just fine with the spring and follower installed. As an added benefit, your mag will now hold and reliably feed 9 rounds, for a 9+1 full capacity. Don't mess with the mag lip length. So far, lengthening mag lips has only brought us headaches, with new types of jams resulting with certain types of ammo.
Ammo -- the above mods/repairs will get your B chewing through brass cased FMJ like nobody's business. If you don't want to do any of the above, just want a quick fix for a plinker or what not, or if you want to max out reliabilty, here's the skinny on ammo.
Steel cased ammo is what the Star B was designed to shoot, and TulAmmo 115gr steel case FMJ (a common Wal-Mart find) will run like a champ through Bs and BMs that absolutely refuse to cycle brass case ammo. This load is very close to the original Axis load that Star was contracted to make the guns work with. And you can make some very nice JHP loads with broken-down cases from TulAmmo. My 1944 B chewed through 50 rounds of TulAmmo steel cases loaded with Hornady 147gr JHPs and 4.2gr Bullseye like it was raining -- with the single exception of one nose hang-up on the feed ramp (which is not polished or throated in my gun -- and that, I'm certain, is why).
Other ammo tricks that work are:
firing FMJ with a long OAL. RWS 124gr loads are the best option of this type we've found so far. That long OAL tends to prevent the slop and instability that contributes to jams in the B. As a side note, the RWS 124gr we tested is loaded with copper-washed iron bullets very similar to those the Axis used in WWII. If you wanted to get really serious about replicating Axis loads, I suppose you could break down RWS, file the bullet bases down to a bullet weight of about 108gr, then load them into steel Berdan cases from broken-down TulAmmo or Wolf or Brown Bear or whatever. TulAmmo is, however, the only steel cased ammo we've actually tested in the Bs (three Bulgarian Contract Bs were used in testing).
And -- "Sub-gun" ammo, like Prvi Partizan, 158gr FMJ -- which fires bullets so heavy that the gun's recoil re-seats the ctgs to the rear of the mag and tends to keep them from slopping around and jamming. This is "sub-gun" ammo because it's sub-sonic, not because it's loaded "hot," but as always it's a good idea to use a brand new Wolff recoil spring in your gun. Just be aware that we're finding that the Wolff springs need a bit of a break-in to take a set and really start performing well. And -- the Bulgarian contract guns seem to generally have good springs.
Also -- as noted in a follow-up I posted below -- abrading the rear 2/3 of brass cases with 80-100 grit sandpaper increases the friction between cartridges and tends to make them stay rearward and neatly stacked in the mag. Higher case friction appears to be the factor that makes the steel cased ammo work as well. One thing we have not yet determined, however, is whether it's the steel or the lacquer that creates this effect. So, you might find that a light wash of laquer on brass-cased ammo may work as well. If you try it, please PM me your results and give me permission to use your data, with credit given to you, when we do put together a proper guide for the B.
Okay. What else? Extractors.
Extractors should be adjusted so that they just start to bite on a case head at the right spot as the ctg travels up the face of the breech. I've found the easiest way to determe this is to take a fine point sharpie to a clean slide face and mark the arc of the top of a cartridge rim at the level it's held at in the barrel's low/unlocked position. Then you can dis-mount the slide and use a casing to adjust toward that mark. Much more bite than this, and you'll get failures to fully chamber. Much less and you'll get more jams. Adjust by carefully and slowly cutting the inner foreward flat of the extractor. This takes time, patience, and a lot of assembly and re-assembly.
I think that about covers it. You must accept your own risks of injury, property damage, or death whenever you take tools to a gun. I am not a licensed gunsmith. Responsibility for wise decisions is yours and yours alone. No guarantees that you won't damage your gun trying any of this, either, but if you run into trouble, like I say, PM me and as soon as I can, I'll help you work through things.
One more thing -- In case you're wondering, it appears that the Bulgarians pulled their Bs apart and dumped all the small parts into bins, then re-assembled them after refinishing with whatever parts came to hand first. This is, apparently, why some of them work okay and some are absolute nightmares to debug.
Best of luck. I hope this helps. Last edited by Begemot; Yesterday at 04:35 PM. Reason: Attribution