Weatherby 338 RPM

I hear you Jim I’ve been very tempted to do one in 6.5-284, but because im generally a bit of a pussy I think I’ll do a swede or super swede.
 
I heard right here that the 6.5 creedmoor is a pussy plinker extraordinaire

6.5-06 AI not as cool as the 280 AI?
 
^ me too, that’s why I like boring stuff like the 270 win and 7mm RM.

Since savage has embraced the 280 AI in the axis maybe it has lost its hipster appeal
 
Slimbo said:
On another forum there was a member claiming to be the head engineer for Kimber. He said that the action was scaled down to minimum dimensions for a standard 308/30-06 based cartridges and the 284 wouldn’t leave thick enough chamber walls.

I’m no engineer or gunsmith, just relaying what was discussed many times over on another gun forum
Click to expand...

Why don't we just run the numbers on the hoop stress in the barrel tenon with that diameter of cartridge?
 
Slimbo said:
Please do….I look forward to seeing the results.
Click to expand...

Confirmed! To be a terrible idea, that is, to chamber a Kimber 84M or 84L in a cartridge with the case diameter of a 284 Winchester (0.501" base diameter).

Here's the stats: If we calculate the hoop stress in a barrel tenon based on the minor diameter of the thread and, thus, the stress at the relief cut by the shoulder, most guns seem to run around 110,000 to 120,000 psi with the largest available factory chamberings. This is load on the steel, not pressure in the chamber. Logically, higher chamber pressure OR thinner chamber walls increase the load. Some guns, like the Sako TRG42 in 338 Lapua, are about 130,000. This all lines up with the yield strength of steel in the usual hardness used for rifle barrels. HRC 28 to 32 hardness steel gives 133,000 to 150,000 yield strengths, respectively. 140 ksi seems like a pretty hard limit if we want some safety margin with the strongest steel commonly used in barrels.

Kimber 84 has a barrel tenon with a 0.84" x 20 TPI thread. Minor diameter of that thread size is 0.765".

A 308 Winchester (0.473" diameter) running 62,000 psi chamber pressure in a Kimber 84 will have 137,700 psi hoop stress. That's cutting it close...I would not use just any old barrel blank on a Kimber 84; make sure you know the yield strength of the steel used to make the blank.

With 64,000 psi chamber pressure in a 284 case, there will be 160,128 psi hoop stress in the steel! The load is higher than your yield strength even without an over-pressure cartridge...very bad!

Now, the force applied to the barrel tenon by the torqued action threads adds some strength there as does the major diameter of the barrel threads. But you still have the completely unsupported relief cut by the shoulder; this is where you will first see the deformation. I've seen photos of a cutaway barrel that bulged at the relief cut when some gun plumber decided to chamber an AR15 in a cartridge with too large of a diameter.

Long story short: The Kimber 84 action truly is designed to have zero excess diameter (and weight) when chambered in a 0.473" diameter cartridge. Do NOT go any bigger if you value your eyes/face/hands/life.

The End.
 
rifleman762 said:
Confirmed! To be a terrible idea, that is, to chamber a Kimber 84M or 84L in a cartridge with the case diameter of a 284 Winchester (0.501" base diameter).

Here's the stats: If we calculate the hoop stress in a barrel tenon based on the minor diameter of the thread and, thus, the stress at the relief cut by the shoulder, most guns seem to run around 110,000 to 120,000 psi with the largest available factory chamberings. This is load on the steel, not pressure in the chamber. Logically, higher chamber pressure OR thinner chamber walls increase the load. Some guns, like the Sako TRG42 in 338 Lapua, are about 130,000. This all lines up with the yield strength of steel in the usual hardness used for rifle barrels. HRC 28 to 32 hardness steel gives 133,000 to 150,000 yield strengths, respectively. 140 ksi seems like a pretty hard limit if we want some safety margin with the strongest steel commonly used in barrels.

Kimber 84 has a barrel tenon with a 0.84" x 20 TPI thread. Minor diameter of that thread size is 0.765".

A 308 Winchester (0.473" diameter) running 62,000 psi chamber pressure in a Kimber 84 will have 137,700 psi hoop stress. That's cutting it close...I would not use just any old barrel blank on a Kimber 84; make sure you know the yield strength of the steel used to make the blank.

With 64,000 psi chamber pressure in a 284 case, there will be 160,128 psi hoop stress in the steel! The load is higher than your yield strength even without an over-pressure cartridge...very bad!

Now, the force applied to the barrel tenon by the torqued action threads adds some strength there as does the major diameter of the barrel threads. But you still have the completely unsupported relief cut by the shoulder; this is where you will first see the deformation. I've seen photos of a cutaway barrel that bulged at the relief cut when some gun plumber decided to chamber an AR15 in a cartridge with too large of a diameter.

Long story short: The Kimber 84 action truly is designed to have zero excess diameter (and weight) when chambered in a 0.473" diameter cartridge. Do NOT go any bigger if you value your eyes/face/hands/life.

The End.
Click to expand...

So avoid Kimbers. Got it. Thanks for the info. - dan
 
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