#4 build question

Some of you may have seen sarco advertising barrelled enfield receivers. The #4 receivers are $70. My plan is to get one, yank the old barrel out (make that sound easy, don't I?), and install a new criterion barrel. These receivers don't have bolts. I know I'll have to fit the locking lugs on the replacement bolt to engage properly.

So, here's my question. I read somewhere that the #1 receivers were basically case hardened at the locking surfaces, so you can't just lap the lugs. Is that true of the #4s?

I know someone is going to ask why I want to spend all that money and time. The answer is this. I can make sure everything is built nice and tight, and exactly the way I want it. Now, if I can find a bubbatized #4 with a bad bore that I can get cheap, I'll go that route. However, people are asking $300 and up for some rather poor specimens.

JC?

I do not believe that the No 4 Bolt head were cased hardened. Though that is not that difficult a process. (Once you have done and have access to a heat treat oven) I suppose that the Criterion barrel will be short chambered to make head spacing easier. After my past dealing with Sarco (they Suck) I would advise caution I would not even think about the 45-70 actions modified by their trained chimps.

It would be nice if Criterion started making bolt heads too! especially number 3's please

I think you have to fit the bolt to the receiver and not the receiver to the bolt; as it's the receiver that is hardened I believe.

You don't mess with the receiver, only the lugs on the bolt body. I have seen it said before by Peter Laidler over on milsurps.com (he was an armourer for many years) that if there was setback of the areas on the receiver they would be condemned as they were then beyond repair, and that applies to all of them.

I wonder if that tool is available. As I understand it, the locking surfaces on the bolt are helical, so chucking the bolt in a lathe and turning the lugs down is out of the question. A milling machine could do it with the proper jig.

Does anyone have Laidler's write up concerning bolts? I have not read that yet.

The lug engagement was set up during proof firing. The firing of the heavy proof loads set the lugs back against their bearing surfaces, I have never heard of a special tool for the job.
You may have to do some careful stoning of the lugs to get them to fit.
Use bearing blue to check the fit and stone the high lug.