Head Spacing a Rimmed Cartridge in a Coned Breech

[Ray Gross]

What does the front of the cartridge rim bear on?

I had a question come up regarding a 219 Donaldson Wasp chamber in a pre-64 Model 70, but I am curious what the general mechanism is for any coned breech action?

 

[WSnyder]

You need to leave a raised rim portion for the rim to bear against with a notch for the extractor.

 

[Will Henry]

Generally speaking, rimmed cartridges are not used in a coned breech. The 1917 enfield is coned, the P14 is not. If the breech is coned, the bolt face counterbore has to be shallower than the thickness of the rim, so that the rim can fit on the barrel face.
I can't recall what Winchester did on the Model 54 in 30/30 (This is annoying. I should know!). Maybe someone else will chime in. Either that, or I'll have to look it up because it bugs me, not knowing. WH

 

[WSnyder]

Michael Turner did this with his 30-30’s. I have or had pictures of it somewhere. You might be able to dig it up on BRC. He built his own actions and used a coned breech. He used a dremel or die grinder to do the notch for the extractor on the extension for the rim.

 

[Will Henry]

When I barreled a Remington clone in 30/40 Krag, I left a protrusion upon which I could seat the rim, then cut away for the extractor. Workable but not a good system for feeding. WH

 

[DaveTooley]

The front of the rim in this case doesn't touch anything. It headspaces like a rimless case. Most of the time my tenon length is -.010" less than the HS# so the end of the gage is exposed. If using a rimmed gage and a reamer that cuts the rim just HS as normal and then cut the cone and extractor groove.

 

[tobnpr]

It headspaces like a rimless case.

Yup.
I've built a lot of custom 54R rifles. I always looked at the breech extractor cut as tedious and unnecessary, so I called Dave Manson and asked him if there was any reason I couldn't headspace off the shoulder instead.
"Absolutely"- and he made me a custom "go" gage to do just that.

 

[Sniperhandle]

Yup.
I've built a lot of custom 54R rifles. I always looked at the breech extractor cut as tedious and unnecessary, so I called Dave Manson and asked him if there was any reason I couldn't headspace off the shoulder instead.
"Absolutely"- and he made me a custom "go" gage to do just that.

Back when UK59 barrels were plentiful and people were putting them on their Mosin's, The cases were rupturing because it was unsupported just above the rim.

To get them to clock properly people were just cutting the extractor groove wherever it headspaced leaving the case unsupported where the original extractor cut was. I have tried to find the pics but it's been too long. Leaving the case stick out far enough to get away without making an extractor cut is asking for trouble in my way of looking at it.

 

[tobnpr]

Leaving the case stick out far enough to get away without making an extractor cut is asking for trouble in my way of looking at it.

Not when done by a professional that knows WTF they're doing.
The extractor is much longer than it needs to be. Shorten it leaving enough meat to retain its integrity, still enough to grab the rim and clearance from the barrel breech. I set case protrusion at .125, same as with other flat breeches. The casehead on the 54R is no different than any non-rimmed cartridge so there's no issue.

 

[DaveTooley]

Yup.
I've built a lot of custom 54R rifles. I always looked at the breech extractor cut as tedious and unnecessary, so I called Dave Manson and asked him if there was any reason I couldn't headspace off the shoulder instead.
"Absolutely"- and he made me a custom "go" gage to do just that.

When we were working with the 30 American case everything was a rimmed case. .473" and .440"
I made or had Manson make custom go gages.

 

[Ray Gross]

Yup.
I've built a lot of custom 54R rifles. I always looked at the breech extractor cut as tedious and unnecessary, so I called Dave Manson and asked him if there was any reason I couldn't headspace off the shoulder instead.
"Absolutely"- and he made me a custom "go" gage to do just that.

We still make ‘shoulder gages’ for rimmed or belted calibers from time to time

 

[WSnyder]

I found Michael Turners old post on BRC with pictures. It has photobucket watermarks but you can still see what he did.

How I make the 30-30 Agg.

Several people have asked how I make the 30-30 shoot so well. Some of the tricks are common now with the popularity of the 30BR. Back when I first started shooting the 30-30, super slow twist were unheard of. When I asked Hart to make me an 18" twist barrel, they were not willing because they...

benchrest.com

Pictures of his action.

Why I Shoot the 30-30 in Benchrest

Pictures I said I would post pictures this evening, so here they are. The receiver is 17-4PH wire edm cut, H900 heat treat. Bolt lugs are S7, bolt body is 6AL4V titanium, bolt handle is 7075-T6, cocking cam D2. The bolt shroud, bolt stop, trigger guard, and action screws are all 7075-T6. I...

benchrest.com

 

[Sniperhandle]

I fixed his photobucket pic for you.

 

[WSnyder]

View attachment 1623654
I fixed his photobucket pic for you.

Thanks! You got me to go look and learn how to do that

 

[Sniperhandle]

Thanks! You got me to go look and learn how to do that

Well there's about 3 gazillion more photos on the interscreens just like it that need fixed. Photobucket broke the internet, I wouldn't use them if they were the only way there was to post a pic.

YW

 

[LVLAaron]

That looks really not fun to make.