Thread: Is it Pressure or Powder Capacity?

Originally Posted by Cordite

Maybe think of it in terms of total volume of barrel + cartridge case. By the time the bullet is about to exit the muzzle it is at least evenly distributed, probably pressure slightly higher in the case itself. Come the point when the bullet leaves the muzzle, all that pressure now gets vented forwards unhindered, except for barrel resistance. In the case of a magnum size cartridge behind a .22 barrel, that will be quite a rush of fast gases hitting the throat area of the barrel and they will be at a relatively high pressure for longer due to the small diameter (=more resistance to gas flow) of the barrel.

But I don't disagree with this @Cordite....in chamberings running the same pressure, it's only natural that the smallest bore size will wear first.

Ok here are the last words I will post up on this 'pressure vs case capacity' thread (hopefully it will help people understand). I just found the below information so am quoting it:

"...after seeing a lot of 6.5x284's go south at 900 and a couple 6.5 WSM's go south at 500-600 I started thinking. Powder Burning does not cause the heat that destroys barrels it's the Pressure. The Pressure causes the extreme heat that's necessary to burn and heat check the barrel.
Anyway the 6.5 Saum case is near perfect because it allows you to throw a 6.5 140gr at 3100 at about 53,000 PSI with H1000. Other cases have too much capacity or not enough. The Saum case was picked not because it's magical, but because it is the perfect fit. In a perfect world, I would take the RCM case and shorten it a tad and give it a longer neck. That would truly be perfect!!!! At any rate, the 6.5 Saum is working as we thought it would.

Here is a thought to those that are still having problems understanding it. Shoot next to a 6mm REM, 243 ETC, any caliber that has a 63,000-68,000 PSI SAMI pressure. As soon as the rifle is fired eject the case into your hands. Those of you that have had a 223 brass land on you or go down your shirt know what will happen, it will burn the crap out of you. The 6.5 Saum with the load I'm talking about comes out only very warm and you can grasp it tightly with your hand without getting burned. Keeping chamber pressures low not only keeps your barrel from puking early it's also easy on your rifle and the components, IE Brass lasts a long time!!

Yes if you hot rod this caliber IE a load of 60.5 grains 4831 SC and the 130VLD at 3400fps you will be pushing 68,000 PSI and toast the barrel in 600-800 rounds.

Initial loadings were based on Quick Load predictions which are not 100% accurate but are ballpark. Bryan Yeung tested these loads with a strain gauge type pressure meter and the predictions were very close to the QL predictions 53 to 56k . Nobody has made a Pizo or CC test Barrel and got actuals yet. But I'm not that worried about it at this point as it's doing what we theorized it would do so it's a moot point. 3k+ with the recommended loads. 61gr H1000 on 140 , 63gr H1000 on 130. You want to add horsepower there is plenty of room but your barrel mileage will suffer.

The 6.5 did its job. I will pull the Barrel with just over 4000 rounds about 4034 or so give or take about 10, I kept a pretty good count. I will keep this barrel for training as it still shoots great, it just lost a lot of velocity. Hopefully, the Nay-Sayers will have the proof they wanted."