rssc Posted April 14 Report Share Posted April 14 I was out with a buddy today shooting a Vollmer hk51b. We were able to get it to run for short bursts. It seems like it would constantly have issues with the first few rounds of the belt but then run the remaining 12 or 15 just fine. The gun seemed to run better when I lifted the belt and took the weight off. For those that have one of know about them, are you aware of any tips tricks to do when prepping the belt? These are mg42/mg3 links recently purchased from RTG. Any other tips or tricks (on anything hk51b related) would also be appreciated. We are new to the gun. Thanks! Quote Link to comment Share on other sites More sharing options...
RCD1952 Posted April 15 Report Share Posted April 15 Is the caliber 7.62X51? If so, the jaws of the MG42 links need to be opened up. The 7.62 case is a larger diameter than 8MM. I used small needle nose pliars to force the link jaws slightly wider by using reverse pressure on the pliar grips with the needle noses inside the opening of the link. I did this for my MG-42 since I only shoot 7.62. Hope this helps. Quote Link to comment Share on other sites More sharing options...
rssc Posted April 15 Author Report Share Posted April 15 (edited) It is 7.62x51. Thank you very much for the advice! Earlier today someone mentioned that mg3 links worked better. I looked at the mg3 and apparently it is chambered in 7.62x51. The mg42 is chambered in 8mm so it makes sense that if we were using 42 links they would add drag to the stripped of the rounds and negatively impact the function of the gun. Mg3 links would work better. Thanks so much! Edited April 15 by rssc Quote Link to comment Share on other sites More sharing options...
mattnh Posted April 15 Report Share Posted April 15 (edited) I assume you are using M13 links. HK21/21E/MG3/51B all use M13 links when run in 7.62x51 (unless the gun it setup for belts which requires different feed mech parts). FWIW. I've never seen a 51B setup for belts You can try opening the links a bit, but my guess is that you have a weak recoil spring. Edited April 15 by mattnh 1 Quote Link to comment Share on other sites More sharing options...
MGTedFL Posted May 1 Report Share Posted May 1 Matt, quick question. I picked-up my 51B years ago, and sent it straight-off to Mike at TSC. He "tuned it up", rebuilt my stocks with new recoil springs, cut my DLO box for the ejector and set it up to run MG3 belts. I would prefer to use my M13 pig-links (upside down, of course). You mention different 21 mechanics for belt vs. links. Is there a different pitch sprocket that is needed? Is the pitch (spacing) of the M13 links different than the MG3 belt? I rarely shoot it, as I'm just fine with the standard 51, but would like to try a belt of links, just don't want to damage anything. Any input would be appreciated. Quote Link to comment Share on other sites More sharing options...
mattnh Posted May 1 Report Share Posted May 1 1 hour ago, MGTedFL said: Matt, quick question. I picked-up my 51B years ago, and sent it straight-off to Mike at TSC. He "tuned it up", rebuilt my stocks with new recoil springs, cut my DLO box for the ejector and set it up to run MG3 belts. I would prefer to use my M13 pig-links (upside down, of course). You mention different 21 mechanics for belt vs. links. Is there a different pitch sprocket that is needed? Is the pitch (spacing) of the M13 links different than the MG3 belt? I rarely shoot it, as I'm just fine with the standard 51, but would like to try a belt of links, just don't want to damage anything. Any input would be appreciated. I’m not the right person to give you a definitive answer. I suggest asking some HK experts (like over at hkpro, Mike at TSC, Mike at MM). My knowledge on these is secondhand from a guy I used to know that had a couple of them and his used M13. At a minimum, I believe the feed mech requires a different belt-specific sprocket and the bolt head is also different (belt-specific). Quote Link to comment Share on other sites More sharing options...
jbntex Posted May 1 Report Share Posted May 1 (edited) The original HK21 with the slide in feed mech was originally designed to run with on-disintegrating MG42 / DM-1 belts. There is a meaningful pitch/spacing difference between the rounds in an DM-1 belt and a belt of M13 links. Some US gunsmiths have figured out ways to get M13 disintegrating belts to run in the older HK21 slide in feed mech guns my modifying the star drive teeth to better allow for feeding of a belt of M13 links. Also keep in mind the the original HK21 recoil spring has to work harder as the HK21 only advances the belt on closure. So the gun has to be able to strip a round from the belt, then fully advance the star drive to bring the next round into position and finally still have enough ommph to chamber the round, overcome the friction of the locking lever and finally trip the sear. If you feed M13 belts into unmodified HK21s the gun works much harder and you will see dents in your brass where the teeth of the star drive are pinching the rounds and the bolt head is riding rearward over the round trying to push the round down on the drum and also crushing the case neck on the star drive. I have never seen a HK German M13 specific parts for the older HK21. Its always a US gunsmith modification of the star drive and feed mech to make it work better with M13 links. The HK21E with the swing down feed mech is completely different design. The HK21E doesn't have to work as hard as the feed mech advances the belt on both recoil and closure stroke so each forward/aft movement of the bolt only has to advance the belt half way. For the HK21E there are different feed mech parts that were optimized for DM-1 belts but should also run DM-6 links and which will also kinda run M13 links. In regards to the DM6 German Links are similar to M13 but have some forming features making stripping the round easier and are supposedly made to a more uniform tolerance. M13 links themselves can vary dimensionally from manufacturer to manufacturer with some tighter and others looser. I can see this when I link ammo by hand and you can see and feel the difference between the links. I have also seen E guns that will run reasonable well with used M13 links (that have some stretch in them with use) and loaded Fed LC ammo but refuse to run new foreign made factory M13 linked ammo. The last gen of HK 21E guns had parts optimized specifically to run M13 linked based belts in order to make it much easier on the gun but at the expense of not really being able to run DM-1 belts anymore. To convert an HK21E from the older DM-1 belt optimized feed mech to M13 Link optimized feed mech you have to swap out a bunch of internal feed mech parts. There is a HK21E M13 specific star drive sprocket, two M13 specific control ring pawls, an M13 specific belt roller, and an M13 specific backlash lock. If you know what you are doing it takes about an hour to fully disassemble an HK21E feed mech and reassemble swapping in the M13 link/belt specific parts. I have done a handful of conversions to M13 over the years on E gun feed mechs that are were finicky when it comes to M13 belts with the DM-1 optimized feed mechs. Once the feed mechs are set up with the optimized M13 feed mech parts you can feel how much easier it is to pull a belt of M13 through the feed mech ands seat a round in the feed tray using a starting tab vs. the older DM1 optimized feed mechs. There is also an M13 specific E bolt head which is cut slightly different on the underside and an M13 E carrier (I believe the carrier difference is merely a marking difference) Edited May 1 by jbntex . 1 1 Quote Link to comment Share on other sites More sharing options...
har1690 Posted May 1 Report Share Posted May 1 ^^^^^ Great write up^^^^^ on the 21 and 21e feed mech. Quote Link to comment Share on other sites More sharing options...
smdub Posted May 1 Report Share Posted May 1 6 hours ago, jbntex said: There is a HK21E M13 specific star drive sprocket, two M13 specific control ring pawls, an M13 specific belt roller, and an M13 specific backlash lock. You are the first person I've seen say what other parts get swapped for the different pitch belts/links. Thank you! I have a BPP23E that I gathered 21E parts for. It runs w/ links M13 currently as the late belt unit I got from hkparts is marked for that. I've only had it out for testing once. But there is some discusion that it may not be entirely correct/orig and was put together w/ non-german parts. I've been interested in converting back to use a DM1 belt (crank loaders are easier to use and belts are easier to pickup at the range.) I'll look through the parts manuals I have to try and find the specific part number differences. Not that that matters much as nothing is really available anymore. Quote Link to comment Share on other sites More sharing options...
rhouston8 Posted May 2 Report Share Posted May 2 MM23E/21E owner here.....my gun def runs M13 w/o issues or mods. Good write up on the M13 v other link/belt types ...I had always just figured the HK51B ran M13 links as its prefered food. Quote Link to comment Share on other sites More sharing options...
johnsonlmg41 Posted May 3 Report Share Posted May 3 Good info, but academic since most 51B builds don't run regardless of what links are used or the combinations of parts. So much going on at once, it's difficult to get it all to work in harmony. Starting with the 21 platform is the first problem, since that was not too dependable in the first place, and that was for original guns, not "builds" which adds another level to the already marginal design. If you are successful in getting it working, it will be short lived. VERY cool on the gun room wall though! Quote Link to comment Share on other sites More sharing options...
MGTedFL Posted May 6 Report Share Posted May 6 I'd be lying if I didn't agree that is spends most of its time in the safe...or on the wall But, it does run well with the MG3 belts...... Quote Link to comment Share on other sites More sharing options...
rssc Posted May 7 Author Report Share Posted May 7 Hello fellow Floridian! Do you have any tips on how you get yours to run well? I've heard the mg3 belts work better than the mg42 belts due to being made for 308 vs 8mm. 2 hours ago, MGTedFL said: I'd be lying if I didn't agree that is spends most of its time in the safe...or on the wall But, it does run well with the MG3 belts...... Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.