View Full Version : Belt fed CETME
04-24-2010, 01:25 PM
I had a crazy idea to make a belt fed ala MG47 in .308, but using the barrel, trunnion and a modified bolt and carrier from a CETME.
My idea with the carrier was to remove the recoil spring from the top and use a dual recoil setup mounted to the sides of the carrier. Then see about modifying the bolt head to feed from the top.
I know, highly unorthodox, but could be interesting.
04-24-2010, 02:58 PM
I'm just thinking simple but you might have a better idea already.
But why not just turn the bolt & trunnion upside down like the AK47 design? Your thinking of taking off the recoil spring part off the top so that will be facing down now.
I'd think the hardest parts would be setting up the side mounted recoil springs and hammer?
04-24-2010, 06:30 PM
I was moving the springs to the sides to clear a path of travel for the hammer. The reason I want to try to keep everything right side up is to hopefully reduce any extraction issues the design might have, as well as leave the option to use the butt-ton of G3 mags I have in an IMI Negev setup.
04-24-2010, 06:55 PM
Why not look into an HK-21 type belt feed design ??? That saves radical mods to the bolt carrier, recoil spring, etc.
The H-21 type uses sprockets like a six pointed star to feed the belt across the feed plate. Two such sprockets on a small shaft are rotated by a vertical acting lever which is cammed downward by the bolt carrier tail end.
The feed system is underneath the action and very compact.
04-24-2010, 09:53 PM
I've never seen the internals of a 21. And I'm going to have an extra carrier once I replace the one that Century hacked on my CETME, as well as a barrel.
07-01-2010, 07:32 AM
wanna sell that extra barrel? hehe anyway i've actually been having some of the same thoughts in my mind (home brew cetme beltfeed that is) an idea i had was removing the the charge tube part on the blot carrier turning the bolt, carrier and trunnion upside down and having either the dual springs or lengthening the rear of the receiver to fit a spring that would have a spacer tube with a groove for the hammer like the semi mg42 builds. i kinda like the mg42 spring idea and without the the charge handle tude part on the carrier a receiver could be made from a long tube with weded in rails heck make it long and have a barrel shroud. then maybe use an mg3 top cover and feed tray and weld on a lug on the bc to run the feed mech and as far as the ejector somehow mount it on the underside of the top cover i guess it would be an interesting looking gun and if anyone knows anywhere i could have a chamber fluted without my wife skinning me when she see's what I've paid then i would try building this exact idea only in 8mm with like a mauser take off barrel hehe then you could always take off the top cover and feed tray and put on an addapter like the hk 21 had and have top mounted mags or something like that. anyway i'm not trying to hyjak your idea too much but i got excited. i like your idea of making the bolt feed from the top or bottom, hmmm i'll have to stare at my bolt and carrier for a while and think hmm you might have problems ejecting cases if you put a feed tray on top and dont turn your bolt and carrier upside down, I'll be watching this thread, if i can help in any way i'd love to but i'm afraid the only think i know about building hk's is from reading tutorrials and staring at my cetme kit
07-02-2010, 07:09 AM
I think my current barrel is shot out, so, its the project barrel. I'll update when I can, but I'm PCSing and going into training, so....
07-02-2010, 09:51 PM
That's cool I had a feeling you wouldn't want to sell your extra barrel haha. All those ideals I posted earlier I've consolidated and am going to make myself a belt fed cetme based rifle too, I figure I'll use my one semi modded grip and fcg on my belt gun and someday my regular cetme, that way the only extra cetme parts I need to buy are trunnion, bolt/carrier and butstock/mount. if my plan works it will be like a weird child of a cetme mother and an mg 42 father haha. I'll probably use an mg42 barrel and try making it 8mm as well
07-03-2010, 12:47 AM
It seems that you are trying to re-invent the German WW-II MG-42V. It was a simplified MG-42 using the roller delay lock system of the StG-45M (today's HK and CETME). Some were built in Switzerland after the war as the SIG 710 series. The recoil spring is behind the bolt/carrier as was the StG-45M prototype. Cool concept !!!
07-03-2010, 04:31 AM
Yeah viper your right I guess, I don't know why I didn't catch that either. I love mg42's (m53's are more my price range) but my "mg45" type idea is more reasonable (probably money wise but maybe not time wise) then even an m53. I've even placed this idea on the front burner and will aquire the needed parts as soon as I have the extra money in a few weeks. I need to research the mg45 more hehe anyone know where to find pictures if there are any? Maybe I'll drill a hole through the bolt and bolt carrier for an mg42 type ejection where a rod is pushed forward to knock the case out haha maybe not I might make it too coplicated to ever fet it finished. Anyway I've hyjacked this thread long enough, I'm tying to think of how the mg3 feed prawl system can be driven without the long drive channel thing that is almost the length of the top cover. Then a guy could use a moddified mg3 cover and feed tray upside down for a poor man's hk21 type rifle, maybe a couple of L shaped levers and springs when the carrier recoils back and a spring to return them after the bolt and carrier come to rest in battery. Hmmm I'll have to chew on this idea and see what there's room for between the feed tray and trigger group when I eventually get my parts.
07-03-2010, 02:10 PM
The belt-fed CETME solution may be to simply copy the HK-21 sprocket type belt drive device. It is a WW-I concept. It works like a racheting 6-pointed star spool that rotates one click at a time from a long lever depressed by the bolt carrier. Pirate here on gunco just got one of these you may recall.
The MG-42 type feed (also MAG-58, M-60, French Mlle-52, Swiss M-51, and SIG 710's) requires a long receiver with a top opening. That design seems more akin to a Brit Bren or Russian DP.
Also keep in mind that the CETME and HK systems require a fluted chamber. So an 8mm Mauser caliber conversion will require a fluted chamber too.
07-03-2010, 03:57 PM
Thanks viper yeah I've been studying what pictures I could find of the hk21 system I was thinking for a lower belt feed to use an upside down mg3 type with a cut down top (bottom) cover to make it fit then a new way to engage it mainly to avoid trying to make an hk star wheel type from scratch. Baisicly the two L shaped levers I thought of would have one that functions like the star sprocket but would move back to its original position and the second L shaped lever ( maybe not an actual L but angled kinda like the cetmw ejector maybe) would be pushed down by the rear of the bolt carrier, that second lever would would engage the first lever to move the feed prawl to the right (actually left since it would be upside down) advancing the belt then when the carrier was forward and clear of the second lever I mentioned a sring would pull the first small lever (and thus also the second) back to their starting position which would also move the feed prawls back the the left (right since upside down) and behind the next carteidge in line. I'm just trying to think of how to use the already availible mg3 stuff with maybe making as little stuff from stratch but it might be just as difficult getting the mg3 feed mech to feed upside down. On the other hand if some lucky guy that happens to own an hk21 would take measurements of some of the parts required for the hk21 feed system that would need to be milled I could probably get them made pretty reasonable.
By the way not trying to be condesending by explaining how the mg3 feed system basicly works, that was for explaining my mod ideas and for the benifit of others reading that might not know.
As far as my "mg 45" cetme I understand I'll need a fluted chamber but thank you for reminding me if I want a fancy barrel bravo 5 said they would sell me a fluted chambered blank (so I could do 8mm) but to keep cost down while I'm still seeing if I can even get the think to work I was thinking a cheap mg 42 barrel and then at worst cutting the flutes best I can with hand files (or even a die grinder with a long tiny carbide bur and a giude) welldog on here and I have been talking about a multi blade broach idea the might work well to cut the flute very nicly (it would have a center piece that's basicly chamber shaped to cam the cutters to folow the chamber profile) but we won't have the time to work on it for a while.