I don't know if you've noticed, but 308 Win/7.62x51 is hard to come by these days, and is expensive when you do find it. That means I've got practically no ammo for my CETME based PSG-None build, and heck if I'm paying the asking price for what is available. A lot of militaries around the world have some sort of lower power/cheaper to shoot alternative to their standard issue rifle rounds. Many have 22lr conversions or 22lr variants of their standard weapons for training. HK was no exception and 22 conversion kits for HK G3 rifles are available, but they're expensive and not very common.
The Germans came up with another option for the G3. DAG makes a blue plastic cased training round that uses 12 grains of powder with a 10 grain plastic bullet. It kicks about like a 22lr, but the super light bullet loses energy very quickly. It's said to be accurate to 100 meters, and has a total range of only 300 meters. Still dangerous so treat them like any other bullet, but perfect for plinking, and best of all, it's still cheap(around $.22/rd at the moment).
A round this weak will not unlock and cycle a standard G3, but they have that covered too. They designed the UB training bolt, a lightweight bolt without any locking rollers that functions as a blowback with the training ammo. It's around 5oz lighter than a standard G3 bolt carrier, and the bolt face is around .030" smaller than standard so full power 308 rounds CANNOT be used with it accidentally. They're also reasonably cheap(around $100 at the moment). Here's what the UB bolt looks like next to my CETME bolt, note the UB electropenciled on it, and the lack of locking rollers on the bolt head:
So this is great, right? Cheap conversion bolt, cheap ammo, this sound perfect for...oh, right, G3 bolts don't fit in CETMEs... The problem is that the bell on the cocking end is too big for the CETME cocking tube. No problem, I can fix that. First thing was to grind down the bell mouth, then using some Unknownium™ tool steel from my pile, I turned a new bushing to slip over the end, and used JB Weld to attach it. The length difference between the G3 and CETME bolt carriers isn't a problem because the UB bolt is made for blowback it doesn't need the cocking handle cam action to unlock the rollers like a standard bolt.
A close up of the bushing, the ground ring is just bigger enough to act as a bearing surface so that the whole bushing doesn't drag in the cocking tube.
I tend to share my guns a lot, and take people shooting that aren't super experienced. To make sure that people know to use the training bolt with training ammo, I decided to paint it. I also painted a mag to match so that people know the blue bolt goes with the blue mag, and uses the DAG blue bullets. As much as I like KG Gunkote, I couldn't justify the price for the little bit I needed so I decided to try high temp brake caliper paint, mostly because I want to see how it holds up.
Thanks for making this write up. I bought the training bolt to go in my C308 and got really disappointed when it didn't work at the range. I shoulda known better but ya live ya learn ��♂️ too bad the Spanish never made anything comparable so I didn't have to modify the HK bolt.
ReplyDeleteHello thanks for the article, just two questions.
ReplyDelete1. What do I need to use to grind down the bell on my training bolt?
2. Is a bushing absolutely necessary after you’ve ground it Down? If so, what size should I look for or do you know of any companies that have bushings that would fit on that like yours? Thanks mate!
1. Any kind of grinder will work to grind down the bell. It's hardened steel, but not super hard. I used my angle grinder, a bench grinder or Dremel would probably work just as well.
Delete2. The bushing is not necessary if you grind it carefully. I accidentally got ahead of myself and ground the bell all the way down. If you can grind it so that it fits in the CETME cocking tube without dragging it should be fine without the bushing.