Case capacity and charge weights

[LGKLAS]

Hello Everyone- When I first bought and started shooting my 6.5mm CM, I bought factory ammunition from several makers. Hornady, Federal and Winchester. To get an idea of which round my rifle would 'like'. I'm now reloading and been using Hornady brass. The average case capacity is 53 gns of H2O. I recently fired 3 boxes of Federal and its brass case weighs more and its case capacity is smaller in the 50.08 gns of H20.

I'm very happy with the loads and charge weights I've worked up using my Hornady brass. Should I reduce the charge weights when I use the smaller capacity Federal brass cases? I'm not loading to full case capacity , and around 90%. Also all of my charges are under the loading books' tables.

Just wondering that if my case capacity is smaller, I should lighten the charge weight in order to avoid an over pressure problem. Thanks in advance. lg

 

[Comrade Terry]

In a word, yes.

 

[seymour fish]

Hello Everyone- When I first bought and started shooting my 6.5mm CM, I bought factory ammunition from several makers. Hornady, Federal and Winchester. To get an idea of which round my rifle would 'like'. I'm now reloading and been using Hornady brass. The average case capacity is 53 gns of H2O. I recently fired 3 boxes of Federal and its brass case weighs more and its case capacity is smaller in the 50.08 gns of H20.

I'm very happy with the loads and charge weights I've worked up using my Hornady brass. Should I reduce the charge weights when I use the smaller capacity Federal brass cases? I'm not loading to full case capacity , and around 90%. Also all of my charges are under the loading books' tables.

Just wondering that if my case capacity is smaller, I should lighten the charge weight in order to avoid an over pressure problem. Thanks in advance. lg

Yes

 

[grovey]

Yes

 

[Uncle Ed]

Using Quickload and .223/5.56 cases with capacities at 28.0 grains of H2O and 30.6 grains of H2O there is 6,000 psi difference in chamber pressure with 25.0 grains of H335.

 

[dcali]

You should expect higher pressures with the same load in a smaller capacity case. Whether or not those will be over pressure depends on how close you were to the limit with the higher capacity case. Its not usually a huge difference between manufacturers, but it is significant.

 

[LGKLAS]

Thank you all for your replies. I knew there would be a difference in pressure in this case, (pun intended) higher. How much higher was what I did not know. Thanx Uncle Ed too, for posting the chart. Even though for 5.56 and I shoot 6.5mm it gives me an idea of the pressure amount change, with an approximate 3 gns H2O less volume. @ Damoncali, I am working with 4 bullets and three powders and have developed 9 loads. Seven are well under a grain max load and two are right at max. (I wanted some alternatives for if the day comes when I can't get my favorite powder or bullet)

I'll do as we always do. Start out low and work up. I've 80 1XF Federal cases and will have 120 1XF Winchesters. I've not measured the difference between the Win and Horn yet. The Federal brass is real nice. It is quite a bit heavier than the Hornady and goes through my sizing die real nice. I've lots of Hornady brass, from buying their factory ammunition of different bullet types and weights, so have the time to work with these other two brands.

Anyway, I thought I would ask around and see what you others came up with and I thank you. Of the three reloading forums I hang out in, this one is my favorite. lg