HK lightweight practice carrier in a Cetme

[bladeworks123]

An HK recoil guide rod is in fact shorter than a CETME's but the rod being shorter won't block the bolt travel to the rear. So changing the length of the recoil guide rod won't change anything, the tube on the HK is too short when cut off to allow the CETME cocking tube support to push the bolt back manually. And when cut off the HK tube will then slide inside the cocking tube support of the CETME . That is why you need to cut the tube off at the exact same length as the shoulder on the CETME tube, and weld the bushing on the end of the HK tube, rather than back farther like the guy in the post says. He stands the chance of his modified carrier buggering up the leading edge of the cocking tube inside his receiver, with the sleeve he welded in there going past it on it's way back. If you would like a picture I can post it.

[bladeworks123]

Here ya go, maybe this will help....I have experimented a lot with making a G3 carrier work with a CETME cocking tube. I know from experience that you do not want to weld the collar any farther back than the original collar on your CETME bolt or you stand the chance of doing damage to the inside of your cocking tube where it fits inside the receiver. Also the shorter recoil spring guide rod of the HK is necessary to prevent the guide rod bushing from coming all the way out the end of the carrier at its most rearward position during firing. If you use a CETME recoil rod it will pass all the way through the carrier when it is in it's rear most position and will sometimes hang up, preventing your bolt from closing. One more reason why CETME and HK bolt carriers will not normally interchange.

[Buelligan]

I will weigh the 2 again and post it tomorrow .

[bladeworks123]

Weight won't be an issue if he is going to cut down the HK DAG bolt to work in a CETME.

[Buelligan]

The modded HK UNDER BAULT 0r under weight bolt is a bit lighter . It is milled to be lighter, I think this helps it to operate . I tryed my OEM bolt with the rollers out and it did not work.

[Buelligan]

Here is my 2cents and the weight off all 3 bolts . I think to shoot DAG-BLUE ammo the bolt must have the rollers removed and be lightened .Well for CRYING OUT LOUD. I spent like a half an HR taking pics of all of the diffent bolts and there weights , and now I cant find them. Any way The OEM G3 bolt weighs 757, the OEM CETME bolt weighs 725 and the Under BAULT for DAG-BLUE practice ammo weighs 580 . I think these weights are in GRs . I bought a scale from HORRIBLE FRIGHT to do this study. Thanks for getting my head out from under my BMW and kicking me in the butt to get this info that I said I would produce MONTHS ago.

[Buelligan]

OK .It is 1230 I have been messing with this since 7am and this is the best I can get up.

[bladeworks123]

I want to be sure that BIGKID gets the point here on what he is trying to do. He has the $100 HK Practice Bolt and is trying to modify it to work in a CETME. What we were talking about in another thread was modifying a CETME bolt to function with practice ammo. I appreciate the weights though, cause I haven't gotten around to the CETME bolt mod yet. Thanks Buelligan.

BIGKID found out, like you, that the HK Bolt won't close in a CETME. Then this guy had written to Dan's and gave him modification info that is not right. By putting a bushing 1 1/2 inches back on the tube of the HK Practice bolt, he stands a good chance of doing damage to the cocking tube in his rifle.

Anyway, I hate to be Johnny Raincloud here, but the modification that this guy gave to Dan's might work, but it is not safe for the gun and could result in having to have a new cocking tube welded on an otherwise perfectly good rifle. It might fire a thousand rounds before it catches on the leading edge of the cocking tube inside the receiver. But as soon as it does, it is cut the gun apart and install a new cocking tube time...not worth it for trying to shoot practice ammo.

[BIGKID]

I am looking for a doner cetme carrier, so I can cut the guide forward and weld it to the shortened HK carrier. I also thought of cutting a similar piece on my lathe. Another thought would be to thread the cut HK tube and thread the wider guide area. I'm just not sure there is enough meat on the guide tube for threads. I'm not a welder and not sure about that route.
I looked at the info I got from Dans and realized the guy just welded a sleve onto the cut HK tube. After measuring both I found that could cause other problems.

TJ

[TheGun]

UbBoltMod.jpg

Sorry to revive an old thread but was hoping to hear if anyone who has tried to adapt the HK Ub Training to a CETME actually had any luck and what method they used. I purchased one & took a slightly different tack. I did some measurement & found that grinding the bell shaped end down to a diameter of approx 16mm or so & then creating a ridge & then reducing the diameter of the front part of the formerly bell shaped end to approx 14.5mm might work. This actually left me with a cocking tube gap of approx .007in. The image above probably explain it better. Yes, it is somewhat Bubba-esque. Just took a Dremel to it. May clean it up a bit or depending upon replies; modify it simular to the method Bladeworks123 suggests. I test fired it today. Worked pretty good. 1st loaded an HK mag with 1 round of DAG Blue. Fired perfect. Next 2 rounds in the mag; no issues. Loaded 10 rounds in the mag; fired a few rounds without incident then got a couple of FTF & a FTE. Tried a different HK mag loaded with 20; just a few FTF & another FTE. Next tried 17 rounds in a CETME mag: 2 FTF if I recall correctly. Opened a new box of DAG Blue & loaded 20 rounds in the CETME mag; no failures of any kind. Also; tried 2 rounds after putting the standard bolt group back in. Fired without issue but had to manually cycle the action. My concern is whether the manner in which I modified the bell shaped end of the carrier tube could damage the inside of the cocking tube.

Thanks,
TheGun