She's running a little hot

[thebigslide]

You're over hodgdon's max load - plain and simple. And it appears that your rifle is happy with that.

It could be a difference in brass thickness, bbl length, throat length, powder batch, chamber temperature, etc, etc.

If the chamber was getting hot and you let cartridges sit in there before shooting, that could definately do it.

SAAMI says 52000 CUP for that chamber, but the hodgdon's loads stop at about 40ksi. That tells me that the cartridge is prone to pressure spiking and I'd be careful. Primers don't deform at any particular cartridge limit, they deform at their deformation pressure, which is often in the ballpark for many cartridges. Just because the pressure isn't high enough to deform the primer doesn't mean it's not over the SAAMI spec. CCI 450 and BR4 primers for example have a .025 thick cup that can take 65ksi before you get piercing or severe flattening. CCI 400 primers are generally good up to 40ksi or so and they may give you more indications of overpressure.

If the rifle shoots well enough at those speeds than it's probably fine, but, assuming your chronograph is accurate, the charge is definately hotter than hodgdon's max load.

 

[KDX]

I read somewhere that Remington's factory loads run about 4100-4200fps. I'm not totally sure on that though.

 

[jethunter]

I assume web expansion is related to the case diameter?

Web expansion is a measurement of case diameter at the web portion of the brass, and in this context it relates to pressure.

If web expansion on your reloads exceeds web expansion in 1F factory ammo fired from the same rifle, then this is an indication you are probably well over max pressure. The factory ammo needs to be same manufacturer as your reloads for this to work - ie rem factory ammo and rem brass reloads.

The theory behind this is that factory ammo in modern cartridges is usually loaded fairly close to max pressure as defined by SAAMI. If you start to get more web expansion in your reloads than the 1f factory cartridge you can be fairly sure you have exceeded the SAAMI maximum pressure set for that cartridge.

 

[vagrantviking]

I read somewhere that Remington's factory loads run about 4100-4200fps. I'm not totally sure on that though.

Velocity and pressure are not always directly related.

Is all the powder burning in the case in .0001 seconds or is it using the whole barrel and burning in .005 seconds? Your velocity might be the same but the pressure sure won't be.

Do the checks that people here are recommending and tread carefully.

The hottest load isn't always the most accurate either. Is that gopher going to feel 200fps difference? The red mist will still be a very pretty sight!

 

[zimbu]

The most likely cause for increased velocities as the rifle warms up is because the powder in the chambered round gets warmed up more before the shot is fired. A load that was developed in cool weather can be dangerous on a hot summer day, especially when the barrel and chamber pick up heat that much faster on a warm day.