Recessed rim vs belted vs rimed brass.

[Grimstod]

Another question for you guys. So of the three basic typs of cartridges rim designs which one do you think will give you the most case life.

My hornady books says
Rimmed cartridges do not stretch near the base rather they stretch in the neck and body
Belted ones do a little and are sorta in between the two types
Recessed rims stretch right near the base and get thicker near the mouth

Does this affect case life?

 

[CatShooter]

Another question for you guys. So of the three basic typs of cartridges rim designs which one do you think will give you the most case life.

My hornady books says
Rimmed cartridges do not stretch near the base rather they stretch in the neck and body
Belted ones do a little and are sorta in between the two types
Recessed rims stretch right near the base and get thicker near the mouth

Does this affect case life?

I know a book says it, and many think if it is in a book, it must be true.

But the above is not true.

There is a single mechanism that causes case stretch - the primer forces the whole case forward, until the rim, the belt, the shoulder, or mouth stops it - the powder creates pressure that forces the case walls to stick the the chamber, and more pressure forces the case head back to hit the bolt face - the case will always stretch at the thinnest part that is just behind the place that the body is stuck to the chamber walls.

Most often, it is just in front of the web.

 

[Grimstod]

So you haven't seen any difference in belted or rimless?

All the books I read say that where the case head spaces from affects this. For example rimed cases headspace off the rim. Belted off the belt. Rimless off the shoulder. Straight cases of the mouth.

Forgive me for being skeptical, I am sure you have more experience then me. Reloading is new to me. I am just a real book pounder thats all.

 

[bigedp51]

Below, an American SAAMI .303 British cartridge being fired in a British Enfield military chamber. Thin rims and thin case walls cause the case to stretch in the base web area.

As Catshooter stated above it doesn't matter on the design of the cases headspacing mechanism. The case stretches in direct proportion to its head clearance or the "air space" between the rear of the case and the bolt face when fired.

Below, a case being fired and stretching to meet the bolt face.

And sometimes the word headspace is meaningless.

The rifles design has its effects also, a rifle with a mauser type claw extractor will hold the case against the bolt face. And a rifle with an ejector button in the bolt face will push the case away from the bolt face and increase head clearance.

 

[Grimstod]

I think I am getting it now. Never even thought about the ejector pushing the case into the chamber away from the bolt face. I learned a few things. thanks guys.

 

[navyrad8r]

Ed thank you for the graphics...
cheers
doc

 

[bigedp51]

I think I am getting it now. Never even thought about the ejector pushing the case into the chamber away from the bolt face. I learned a few things. thanks guys.

In Hatchers Notebook Col. Hatcher kept reaming the chamber on a M1917 Enfield increasing the rifles headspace. This reaming experiment was kept up until it got too dark at the range to see clearly without any ill effects to the rifle or fired 30-06 cartridges. Hatcher later wrote that headspace was a over rated subject, what Hatcher forgot was the claw extractor was holding the case against the bolt face and preventing the case from moving forward.

If Hatcher had done this experiment with the British Enfield rifle that did not have the Mauser type claw extractor he would have has case head separations when increasing the headspace.

Below, the British .303 Enfield bolt head, when the bolt closes the extractor moves to the right and away from the case no longer contacting the rim.

Below the Mauser type claw extractor holds the case against the bolt face.

And the "modern" cost saving ejector button pushes the case away from the bolt face.

 

[Grimstod]

I have a few mosins. They have an ejector that is separate of the bolt as it is housed in the receiver. It does have an extractor that grabs the rim when the bolt handle is in battery. Would that particular setup be more sensitive to headspace.

Also how do you guys think tight chambers affect brass life? Does tighter usually mean longer brass life?

I am pretty sure that it doesn't do any thing for accuracy. I read that somewhere here on the sites articles section.

and what about those sakos that have dual ejectors, would they exhibit any different characteristics. I would think that one ejectors might tilt the bullet slightly in the chamber or at least push it to on side where 2 would be more evenly spread?

 

[bigedp51]

Also how do you guys think tight chambers affect brass life? Does tighter usually mean longer brass life?

If you want a crash course in rifle headspace then just buy a British .303 Enfield rifle. With its removable bolt heads I have set the headspace on one of my Enfield rifles from .006 under minimum headspace to .010 over maximum headspace testing case life and stretching.

In 1914 the Enfield chambers were reamed larger in diameter and longer in shoulder location to make room for "The Mud of Flanders Fields. Our American SAAMI cartridge cases do not match British military .303 cases and our cases fall apart quickly in the larger chambers if not properly fireformed.

In these "fat and long" Enfield chambers you fireform the cases by slipping a thin rubber o-ring around the rim to hold the case against the bolt face. Compressing the o-ring also centered the case in the rear of the chamber and helped promote equal case expansion and case alignment for reloading.

Thereafter you neck size or use minimum shoulder bump and allow the case to headspace on the shoulder and not the rim.

Remington doesn't even know where to put the shoulder of the case on the .303 British.

A fired case in a Wilson gauge, the amount the case is sticking above the gauge is how much further forward the shoulder of the chamber is compared to SAAMI specifications.

So buy a British Enfield rifle and learn about headspace maximus.