rifle sizing

[roval]

after removing the scratches from my 308 die at least the rcbs sb die. i had sized a few cases and measured them with a hornady comparator which should measure from the base to the midpoint of the shoulder. i am using the anvil base that comes with it so i have a flat base. i previously only used a rifle case gage and after sizing, the base is within the gage specs. the measurements after sizing vary from 1.632 to 1.637 [saami says 1,
634- 1.637]of course there is user variatiom but within the same case after measuring it several times i go for the smallest length.

if the die sizes them shouldnt they all be the same size? from the mid shoulder to the base?

i go for the whole range. of the lever pull. making sure it bottoms out and the cases are well lubed.

this is not the whole length and before trimming.

btw they have different headstamps

 

[MrSpiffy]

It may vary based on the composition of the brass and how much it has been worked over time, wall thickness variations, flexing of press components, etc. So, it's never going to be perfect unless you get some super-precise equipment. But, it should be within maybe 0.003" range of variation or less, if using the same brand and lot of brass.

Even with my Lee Breech Lock hand press, I get variation of only 0.002" or less within the same lot of brass, if it's been fired the same number of times.

 

[fguffey]

after removing the scratches from my 308 die at least the rcbs sb die. i had sized a few cases and measured them with a hornady comparator which should measure from the base to the midpoint of the shoulder.

The 308 W datum is almost half way between the two shoulder junctures but when the 308 W case is used for .234 W or 7mm etc. the datum is not halfway between the two junctures. When using the Hornady Comparator use the tool as a comparator as in measuring before and again after firing. It seems they have a radius on the hole meaning it is not possible convert to SAAMI specifications unless the gage is corrected for error.

I use unfriendly case datums, my datums have a sharp edge that cuts the shoulder, The Wilson case gage has a datum but it is case friendly because it has a radius, Wilson corrects the problem when they grind the top of the Case Gage.

F. Guffey

 

[roval]

I use unfriendly case datums, my datums have a sharp edge that cuts the shoulder, The Wilson case gage has a datum but it is case friendly because it has a radius, Wilson corrects the problem when the grind the top of the Case Gage.

F. Guffey

i dont understand this part but i do use a wilson case gage.
i started looking into the datum as it was also my first time trying out and setting up my 308 WFT.

 

[Bart B.]

Use the Hornady gauge to see the difference between fired case and resized case headspace. That's all you really need to do. A couple thousandths spread is normal and causes no problems.

If you want to calibrate that gauge to read actual case headspace, get a 308 Win GO headspace gauge then set the gauge to 1.630" as its measuring it.

 

[witchhunter]

Make sure all brass is the same HS and you pause just a second or two at the deepest part of the die. Check again, it might be more consistent.

 

[roval]

thanks it is fairly consistent with the same brass. its between the different headstamps that i notice it more. i thought the fired brass should be similar as well if they were fired from the same gun an m1a.

 

[horsey300]

thanks it is fairly consistent with the same brass. its between the different headstamps that i notice it more. i thought the fired brass should be similar as well if they were fired from the same gun an m1a.

All brass is not created equal or people would only pay hornady prices on lapua cases.....I'm not saying hornady is bad brass....just not lapua.

 

[Bart B.]

Brass that's been fired in military style semiauto rifles will be fine for hunting and plinking. None has been used for best accuracy in good rifles. Their case heads were mashed out of square on out of square bolt faces. That alone increases test group sizes a half MOA or more.

 

[roc1]

Sorry about crazy posts couldn't get phone to reply correctly didn't mean to post same over again.
I was trying to post I had similar problem Forster and others said if you are using spray lubes can cause this problem. I had same with different brass HS so tried different lube and seems to help but different brass still can be little different just not as bad. I use the Hornady comparator as well tried different ones think it works as good as any others gave worst results not consistent. Wilson is only other one that is very consistent but gets expensive for every caliber. Just a thought
Thanks
roc1