.308 Win Winchester brass vs Lapua brass

[jwrowland77]

Could someone with Quickload help me out real quick? I'm looking for the main differences in pressure, MV etc between using Winchester headstamp and Lapua headstamp or if they're pretty close to the same.

Rifle: Savage Axis 22" barrel. Not sure of bullet length or water capacity of cases. Cases trimmed to 2.005.

Specifics (as best as I can get) fairly accurate load in my rifle: current load:
Winchester headstamp
CCI 250
155gr SMK Palma
IMR 4895 44.5gr
OAL 2.900

Proposed load:
Lapua Headstamp
CCI250
155gr SMK Palma
IMR4895 44.5
OAL 2.900

Any help would be greatly greatly appreciated.

 

[steve4102]

QL cannot determine/calculate data by headstamp. If you wish for QL to calculate the difference between different headstamps, you have to measure case capacity in grains of H20 from fired cases.

 

[rduckwor]

Here are some brass weights and case capacities from my bench. NOTE: The WCC shown is a NATO case and NOT Commercial. The BHM is a Black Hills Commercial match case and they get their brass from Winchester.

So it doesn't totally answer your question but comes close.

RMD

 

[USSR]

jwrowland77,

Don't have QuickLoad, but I can tell you from experience, I would not load 44.5gr of IMR4895 behind a 155gr in Lapua brass. The brass is quite a bit heavier than Winchester brass, with a reduced case capacity. Personally, I would start at 42.0gr and work up towards 43.0gr while looking for pressure signs. Just MHO.

Don

 

[jwrowland77]

jwrowland77,

Don't have QuickLoad, but I can tell you from experience, I would not load 44.5gr of IMR4895 behind a 155gr in Lapua brass. The brass is quite a bit heavier than Winchester brass, with a reduced case capacity. Personally, I would start at 42.0gr and work up towards 43.0gr while looking for pressure signs. Just MHO.

Don

That's kind of what I was thinking. I was trying to figure out if I should reduce 10% or 5% and work my way back up.

Thank you sir.

 

[jwrowland77]

Here are some brass weights and case capacities from my bench. NOTE: The WCC shown is a NATO case and NOT Commercial. The BHM is a Black Hills Commercial match case and they get their brass from Winchester.

So it doesn't totally answer your question but comes close.

RMD

Thank you RMD. Did you come up with this or was this somewhere out in cyber world? I like it just wondering if I could find something like this to print and keep in my binder.

 

[steve4102]

Actually, weighing cases is not a very accurate way to determine internal case capacity. A heavier case may indeed have less case capacity, it may also have more.

If you want to know the actual differences between headstamps you need to measure the internal capacity in grains of H20.

Here is an example of how case weight compares to internal capacity. Note that there is no direct correlation between case weight and case capacity.

http://www.6mmbr.com/223rem.html

 

[Rule3]

Actually, weighing cases is not a very accurate way to determine internal case capacity. A heavier case may indeed have less case capacity, it may also have more.

If you want to know the actual differences between headstamps you need to measure the internal capacity in grains of H20.

Here is an example of how case weight compares to internal capacity. Note that there is no direct correlation between case weight and case capacity.

http://www.6mmbr.com/223rem.html

+10 on that site. I was gonna post it also, I use it for several calibers. It seems good to me.

 

[jwrowland77]

Got on there and noticed that the Winchester and Lapua case capacity were fairly similar. I'll probably just reduce by 5% and work back up.

 

[rduckwor]

The data I posted was weighed on my bench and the Case Capacity was a weight capacity actually measured with water-filled cases consistently filled to the same point. Once fired brass unsized post firing.

Not a huge data sample, but at least some useful data.

RMD

 

[rduckwor]

The site posted is a great site.

I wish they had posted the same data for common 308 cases.

Save us a lot of dribbling and weighing.

RMD

 

[USSR]

Got on there and noticed that the Winchester and Lapua case capacity were fairly similar.

Winchester and Lapua .308 brass are NOT similar, other than they are both .308 cases, regardless of what that site says. Hodgdon lists a 46.0gr load of Varget with a Sierra 168gr MatchKing bullet in Winchester brass. You do that with Lapua brass and you will have a serious overload. A 5% reduction will put you between 42.0 and 43.0 grains, which is fine.

Don

 

[steve4102]

Got on there and noticed that the Winchester and Lapua case capacity were fairly similar. I'll probably just reduce by 5% and work back up.

You are guessing. Not a great idea when it comes to building ammo.
If you want to know how much difference there is in YOUR 308 brass, you have to measure the internal case capacity with H20.

 

[jwrowland77]

Do you weigh the water from fired cases or FL resized cases, or does it matter as long as both cases are the same?

I would NEVER just guess at something like this. Hence the research, and the 5% reduction in charge when I do my workup. Something this serious I would never guess on. I enjoy my hands, rifle and life too much to guess. Plus I'm pretty sure my wife doesn't want to collect my VGLI just yet.

 

[steve4102]

Fired cases. Weigh the empty case, fill with water , weigh again and subtract.

 

[jwrowland77]

Awesome. Thank you sir

 

[scottishkat]

I did not read whether you are shooting 308 win palma brass or 308 win only 155 smk palma bullets. That being said I am unaware of any differences in using palma brass with small rifle primers and 308 win brass. I use lapua brass in my 260 remingtons and there is a noticable difference in case capacity with remington winchester does not make 260 rem brass.

I see data for the 308 win and IMR4895 as high as 47gr for the smk 155 hpbt on the hogdon website note this is not for the palma hpbt. Do you have pressure signs at 44.5gr? If so you definitely need to reduce charge when changing components of any type and as you state 2 grains is a good place to start and work up as before.

I have some lapua brass in 260 that has been reloaded 12 times neck sized probably 9 times and full length sized 3 still going strong. I note the max pressures for 260 and 308 are the same.

 

[jwrowland77]

Sorry, not using Palma .308 brass just the bullets.

In my initial workup, I went all the way up to 46.0 grains of IMR4895. My best load was 44.5 and starting at 45 and above, my groups really started to open up and going by what my mentor told me, this is the first sign of high pressure. My 44.5 load gave me 3 touching holes that could be covered by a dime, horizontal grouping.