Are coned breeches backward compatible with non coned bolts?

[Dirty D]

@karagias do you think that CdG barrels with coned breeches could be backward compatible with Savage or other actions that do not have coned bolts? Looking at the drawings the coned cut is so small down at the web of the case. What are your thoughts?

 

[Mike Casselton]

No, the tenon is longer to accommodate the cone bolt head.
If you skim cut the cone area off, it'll work. That's why a non coned barrel will worth with a coned bolt.

Feeding issues are another thing...

 

[Dirty D]

No, the tenon is longer to accommodate the cone bolt head.
If you skim cut the cone area off, it'll work. That's why a non coned barrel will worth with a coned bolt.

Feeding issues are another thing...

I neglected to specify that this is not a shouldered barrel, it uses a barrel nut.

 

[Mike Casselton]

The cone extends the length of the tenon by the depth of the cone. Here's a couple of pics to help.


Flat breech. Savage and Origin style.
Notice where the extractor groove ends and the body of the cartridge begins.

Coned breech. It's been modified to work with a Remington 700 bolt nose.

Remington 700 "3 rings of steel" style.

 

[Mike Casselton]

Oh, and shoulder or nut doesn't make any difference for the flat vs coned breech

 

[whatsupdoc]

If that picture of the CDG tenon is accurate it seems that quite a bit of the case head is unsupported.

 

[spife7980]

If that picture of the CDG tenon is accurate it seems that quite a bit of the case head is unsupported.

No, it looks like there is .147”+-.004 of case head protrusion.
So yeah, that much is “unsupported” but that’s also why the case head exists.
Pretty standard. It’s got to stick out enough for the extractor to grab onto. Case heads are thicker so it still extends further forward than just the extractor groove.

 

[lash]

This has been covered many times in the CDG thread. The case head exposure is exactly the same on the coned breach. Here’s a diagram of both types of breach.

Do the math and you’ll see that the case head protrusion from chamber face is exactly the same. Bottom left and bottom right diagrams.

 

[lash]

Coned breach: 0.147” unsupported case head

Flat breach: 0.822 - 0.675 = 0.147” unsupported case head.

Exactly the same. One could argue that the coned breach leads to a stronger system due to the fact that the cone led part of the barrel supports the bolt nose and extractor.