C3a1 project

A while back I got the bug to build a C3A1 clone from one of the PH M84 single shot receivers floating around out there.
Well, that's when the search for parts started to get real interesting. At this point, all I had was the receiver in the condition you see in the photo. After many months, I was able to locate a few parts from the US, UK, and Canada. The big challenge has been the bottom metal. I was only able to find a trigger bow, mag catch, and screw. Finally, I got a big break with finding 2 magazines that were unfinished. Basically the main mag body was formed and welded, 2 spacers, and the bottom insert. No springs or followers.

After over a year of searching, I was able to find a bolt. It took a while to find the correct bolt. Apparently one of the lugs is longer, which is different than your standard mauser-style.

This is when my excitement melted into a warm, steaming pile of disappointment. This bolt was not finished at the factory and I soon found out why. It became clear during the machining, the firing pin hole was not in line with the center axis of the bolt. I decided to move ahead and threaded the bolt handle to accept a C3A1 syle knob. I also bushed the firing pin hole to bring it into alignment.

While working through each challenge and researching any information I could find, it became apparent that some of these receivers may not have been heat treated sufficiently. I could tell from working on the bolt that it certainly did not have the appropriate hardness. I connected with a local metallurgical testing company and they were kind enough the help me out. Good and bad news. The receiver tested out at 43 HRC, the bolt.....a whopping 8 HRC. No problem, just send the bolt for heat treating, right? Well, for those that may not be aware, the heat treatment technicians need to know the exact composition of the alloy if you're going to have a shot at obtaining the hardness you need. You can't just call Parker Hale and ask. Once again, the metallurgical experts to the rescue! Enter the amazing world of XRF, or X-ray fluorescence spectroscopy. using XRF, they were able to determine that the bolt was 4140. Off to heat treat, and it came back 43-45 HRC!

Bottom line, everything is off. But, after many hours of struggling, head scratching, researching, we're getting somewhere. I fully admit that the juice may not be worth the squeeze. But, the whole point of this exercise is to learn, and there is a metric **** ton of learning being done.
Come to find out that the firing pin, mainspring, cocking piece assembly is off center as well due to the misalignment of the hole in the bolt body. I fiddled with the firing pin for hours to get it to move without binding. It is something on the order of 0.050" eccentric from the base of the firing pin (where the spring stops) to the tip.

Trued up the top and bottom of the receiver, milled in the slot for the scope base, including the dovetails near the front. Opened up the mag well. That geometry was very challenging to execute.

Trued up the threads and face of the receiver, best I could. You can appreciate how off center everything is. Hence why machinists with vastly more experience and knowledge decided to scrap this. And here I am trying to give this thing life. Idiot!

I received my barrel from PacNor and proceeded to thread/chamber. Worked out some pillars and completed the bedding. Even the pillars were a pain in the ***. I had to keep in mind that the rear pillar does not contact the receiver directly because the rear portion of the trigger is between them. I decided to make the rear pillar with a sacrificial portion to maintain the spacing while bedding. I then milled off the exact amount from the rear pillar for the trigger.

Made the mag box from scratch using photos. Also fabricated the front portion of the bottom metal that secures the receiver front. The real fun was trying to make a follower from scratch. I'm using a spring from another magazine that I will secure to the follower with a rivet once parkerizing is complete.

And this is as far as I've gotten. Next step is metal finishing, testing, adjusting, and parkerizing.

Attachment 111788

Maybe testing and adjusting before metal finishing...parkerizing... Quite an accomplishment. That almost blank receiver would be the end for most. Off center barrel ring, not easy to deal with even if you knew. Well done...

Quote:

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Originally Posted by Molonlave

After over a year of searching, I was able to find a bolt. It took a while to find the correct bolt. Apparently one of the lugs is longer, which is different than your standard mauser-style.

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Amazing work...i'm glad to see another project c3a1.

A comment on your bolt - sorry to tell you this, but the c3a1 bolt body is a standard 1200tx bolt with the standard mauser 98 "anti bind" rib at the top, and standard bolt locking lugs.

The extended left locking lug was a feature usually found on the m84 actions.

I have found that adding the top "antibind" rib seems to decrease the smooth operation of the action.

And I trust you noticed that the scope mounting holes on the centre section of the action are not in line with the bore.

Thank you for the comments and information! Like I mentioned before, this is about learning and I appreciate any knowledge sent my way. Please keep the info, suggestions, and comments coming!

Great info regarding the bolt. I'm assuming the M87 action was used for the C3a1. If that is the case, then the action has the clearance for the anti-bind rib of the bolt?

Regarding the scope mounting holes, are the holes off bore center in general by design or just in my specific case?

The c3a1 scope mount 2 forward holes are offset left, the rear hole is in line with the bore.

Molonlave,

The bolt used in the C3a1 is 98 Mauser design like the 1200TX with the gas flange on the bolt shroud milled with clearance for the safety. The M87 receiver does not have the race cut for the the "anti bind" bolt rib and needs to milled for this feature. M87 does not mean identical to C3a1. They are similar and need to be modified for the bolt raceway, scope mount, no front holes and no roll stamp.

The C3a1 scope bracket holes are not on center as Lee Enfield points out - forward 2 are offset. They are offset intentionally and will be over the bolt rib race way. Recently I've seen a couple reproduction C3a1 scope brackets (very well made) with the holes on center. Careful how you layout your mounting hole and what you buy.

Hope this info answers your questions.

Ron (Canada)

Thank you for the info, this is exactly what I was looking for!

I'm not a C3 fan, but that's very impressive work!:thup: