Need help chambering 1917 for a belted magnum

A friend of mine dragged me into the world of chambering a belted magnum case for a coned breech rifle. My experience to date has been mostly mausers with a smattering of other actions but mostly breech faces without a cone. The 1917 enfield we are chambering has given us fits. We cut a chamber and extractor cut in one attempt to find that we had very little belt inside the chamber. Thinking of the horrors of too little case support, we turned off a thread to time our previously made extractor cut (.100") and cut another chamber. As we formed the shoulder and cone we put marking fluid on the bolt face and watched for transfer rubs on the coned breech and nose of the bolt. When everything seemed right we started reaming the chamber. All went well, but when we got the go gauge dimension correct, we only had about .020" of the belt inside the belt cut of the chamber. Chamber drawings I have seen only show the belt to case head dimension and do not show detail on how much of the belt is enclosed in the chamber. So the question is, how much of the belt has to be enclosed in the chamber to be safe? We have had some preliminary feedback indicating that the web of cartridge case is adequate if the belt is enclosed minimally because the web is strong enough in the case. Others think that most of the width of the belt should be almost fully enclosed in the chamber. Any advise on this would be appreciated.

You can grind the pointy end of the bolt off and get the end of the barrel further back. On my fathers 1917, I ground the bolt back round till it was even with the extractor side lug. I set the barrel back far enough so that the bolt enters the barrel like a modern Remington. a cut was made for the extractor. I had some one else chamber and reblue it. Later I had to take it apart and enlarge the chamfer on the chamber as the case necks would hang up feeding slow, it now feeds fast or slow.

I am not sure how you would modify it to feed a magnum without the original large barrel chamfer but it can be done with 06 family of cartridges.

I will let others comment on how much of a magnum case can safely stick out as I have no idea.

On cone breech Winchester M-70, there's about half of the belt that is left unsupported once you cut the extractor slot, the enfield is a similar design so it's probably normal.

here's the link to a picture I found online

http://http://1.bp.blogspot.com/-JCZipJFQlV0/UGeyeM2azDI/AAAAAAAAADo/j--HwGazglY/s1600/P1050508.JPG

P

I'm thinking the fatter the case, the more of it that's going to be in the chamber since the cone is fixed in relation to the bolt face. So this has to be a little better than the original -06 was. And the extractor cut is what it is. Good enough for the -06, probably good enough for a belted mag.

Are you head spacing off the belt or the shoulder?

what angle are you cutting the cone? Are you checking the bolt nose clearance with the extractor removed? I cut the cone to near depth then screw the action on and feeler gauge between the barrel shank and receiver face the cut the cone that much deeper plus .010 for clearance.

Also are you sure it's a 1917 and not a P14? What was the original chambering?

The P14 was fitted rather differently,and did in fact enclose the rim of the case.To accomplish this,a semicircular slot is milled in the barrel to give clearance to the locking lug.When the yanks appropriated the design ,it was changed to be the same as the 1903 Springfield,with a goodly portion of the case hanging out of the chamber.This simplified production,and was in fact also used on the 1896 Mauser that the rifle was mainly copied from.It is dangerous,and if the case blows out through the primer pocket,it a big kaboom.Fifty years ago I worked for a company which sported military rifles in bulk,and Norma put out a kit to convert 1917s to 308 Norma magnum.This reamer was used with an extension to allow the barrelled action to be rechambered in one .We did hundreds,and never a problem or complaint.If you want the case fully enclosed ,buy a Remington 700 with the three rings of steel.Regards John.

Thanks for all the comments. The action is definitely 1917, not 1914. The cone is 45 degrees and it was cut so that there was a slight rub mark from the bolt when the action was closed. The headspace is correct. My concern is only the protrusion of the belt and whether or not the belt is supposed to be fully supported by the chamber walls. The belt is currently about .020" inside the chamber with the remainder of the belt outside. We headspaced the chamber on the belt, not on the shoulder. What do you think?

The angle on the bolt is meant as a bolt stop to prevent wedging the brass in the chamber or resizing the brass if the bolt is slammed home extra hard. I think it has actual clearance and only contacts, again when pressure is exerted on the bolt handle.
I read a gun smithing book from the fifties that recommended safety breaching, that is why I did mine that way. From the other comments you may be completely safe with what you have. Take one of your cases and cut it in half and see how thick the brass is where it is hanging out.
The photo is the bolt that I modified, I used split bushing to hold it in a short Hardinge 5C fixture.

I think that it sounds like you did everything correctly.

The belt was originally intended to provide a positive stop for the long, almost straight case cartridges that were used in British single-shot and double rifles at the end of the 19th century. They had almost no shoulder, so something else was required to control cartridge position in the chamber.
The belt has no relation to case head strength. The fact that the full belt is not enclosed in your newly cut chamber means nothing if the head space is correct.

RWO

You can always measure a selection of your cases to see how high the web is. Using a digital caliper, zero it with the depth stem sitting on the web and the end of the body sitting on the case mouth. Then measure OAL of the case and the reading will be the web height. Then you can see how far up the web is.

Well, I got a call from my friend, turns out the receiver is 1917 but the bolt is 1914! From the comments posted, I think it's time for a long cord and something to hold the loaded action. Thanks for all your help, and sorry for the misinformation.

fishoot said:

Well, I got a call from my friend, turns out the receiver is 1917 but the bolt is 1914! From the comments posted, I think it's time for a long cord and something to hold the loaded action. Thanks for all your help, and sorry for the misinformation.

Click to expand...

My 416 Rigby has a 1917 receiver and a P14 bolt. The diameter of the boltface for the cartridge is larger on the P14 bolt.

fishoot said:

Well, I got a call from my friend, turns out the receiver is 1917 but the bolt is 1914! From the comments posted, I think it's time for a long cord and something to hold the loaded action. Thanks for all your help, and sorry for the misinformation.

Click to expand...

I know this is an old thread, and hopefully you have it figured out by now.

Two options when using a 14 bolt with a 17 receiver.

#1-Match the 14 bolt with a corresponding 14 barrel breach face which is flat.

#2- Cut the cone for the 1917 and grind the front left lug on the 14 bolt to match the contour of the 17 bolt. It doesn't take much.

An unmodified 14 bolt in a 17 coned barrel will not get the bolt close enough to function safely.

On our .300 Win Mag pressure test barrels in a Universal Receiver there is a feed cone (60* center) .125" deep on the chamber. With a .220" min HS on belt , that leave only .095" supported. We have loaded pressures to over SAAMI specs, hit 75,000psi and only blown primers.