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GunNut
Posts: 7,642 Senior Member
Seems counterintuitive to me... reloaders?
GunNut
Posts: 7,642 Senior Member
Hogdon gives the same loads for rifle and handguns in the same chambering. The below seems wrong to me when using slow burning powders like H110 in a carbine vs let’s say a Ruger with a 4.6” barrel. I would think a longer barrel would allow a build of a longer pressure spike before barfing out a bunch of unburnt powder no? Can someone smarter than me explain this?
From the Hogdon manual:
The first thing to remember is that the chamber dimension does not change based upon application. A 223 Remington chamber is the same whether the gun it is in is a handgun or a rifle. The chamber dimension determines the pressure. So, the pressure is the same when fired in that chamber in a rifle or a handgun. The barrel length has no impact on the chamber pressure and hence the reloading data (powder charge and pressure).
The first thing to remember is that the chamber dimension does not change based upon application. A 223 Remington chamber is the same whether the gun it is in is a handgun or a rifle. The chamber dimension determines the pressure. So, the pressure is the same when fired in that chamber in a rifle or a handgun. The barrel length has no impact on the chamber pressure and hence the reloading data (powder charge and pressure).
Replies
In a perfect world, I dont think barrel length would be an issue. As the bullet travels down the barrel the area the burning propellant has to expand into keeps getting larger. In QL the main pressure spike seems to happen in the first 1-2" of bullet travel,assuming the calculations for the graph are accurate.
The above is of course a simplistic discription that negates other potential variables.
Pressures also reach their peak at different times during ignition. Also measured in miliseconds. This is measured and calculated into published lab tested data with the use of electronic transducer pressure instruments.
This is why Weatherby rifles and 5.56 chambers are throated differently than standard or 223 chambers. Anything that contains the pressure longer or at a different point during the ignition event. Again measured in miliseconds. Changes or increases the amount of pressure produced for a given load recipie.
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Mike
N454casull
Chamber pressure of 5.56 NATO is something on the order of 55,000 to 60,000 PSI
As the bullet travels down the barrel, the remaining pressure at the gas port of an M4 carbine is under half that. Move the port out to the length of an M16 rifle, and you're down to 10,000-15,000.
Peak pressure is reached FAST. In the chamber, you have to first overcome the friction with the cartridge case, then you have to swage the bullet into the rifling. Due to the vagaries of the powder burn, you may make peak pressure while that's still going on, but if you don't it will be VERY shortly after, because bullet friction goes WAY down after it gets squeezed and volume of bore for that gas to expand in goes WAY up as the bullet travels.
What the longer barrel does is give more time for that expanding gas to push on the bullet.
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