Brass volume new vs once fired

[Wodez]

I recently did a ladder test because I changed to new Peterson brass in my 243w
I found it again liked it hot with the max load. I shot 6 to confirm and was pretty happy with the results. But then I reloaded some full length resized once fired brass and they shot pretty bad. The only difference being once fired.
I did a case volume test on full length sized new vs fl once fired (3 of each) and the once fired had 1gr more volume.
Should I try a little over max load to compensate for the extra case volume?
And why is there a difference in volume if they are both full length resized.

 

[MidGAHunter]

I've noticed the same. I've gotten to where I do my max charge testing with new brass but then use once-fired to find my optimal charge weight. Sometimes I will even work up OCW on new AND once-fired (typically do this with hunting rifles). I also chrono frequently to make sure a given load stays consistent through brass firings. Once your new brass is fired, even a full length sizing die isn't going to completely return it to factory dimensions.

 

[Wodez]

I always assumed that full length sizing brought everything back to the same.
I have heard of those that only neck size having to fire form their new brass, but I have never heard of having to do it with full length sizing.
this was my first ever batch of new brass. I’m still struggling to get a good load out of the shot brass.

 

[shmtastic]

I use a chrono and find the velocity of the load that shoots well with new brass then I shoot once fired to see if it's the same velocity. If not I add/subtract to make it the same then test again, should get you right where you want.

The chrono info will help you any time you change lots for powder, cases and primers, and bullets may need adjustments of distance from lands. All important info for when you have a good load worked up, so write it down.

 

[kjw]

I wouldn’t think a full length resize would do much except for maybe straighten up the case mouth a little. I’m assuming that new brass is going to be small enough to safely chamber in every action out there and then after the first firing it has expanded to chamber size and is ready for its first true full length re size. Not completely sure but just the way my little thinker sees it.

 

[Cahunter805]

It’s due to new brass being undersized and usually short in the shoulder. Once fired everything forms to your chamber.
I would setup your FL die to just bump the shoulder .001-.002 and test that they chamber. Then load some tests again.
I would load some test loads increasing in .2-.3gr increments and see if things don’t tighten up some.

 

[Wodez]

My once fired groups have come no where near my new brass groups. I dont have a chronograph which has made it difficult only looking at groups. But as I dive deeper into reloading I can see they are necessary.
My new brass groups were .5gr below max load. I tried max load with the once fired brass to compensate for the 1gr larger case volume but they Shot bad. I trie .3 above max load(.8 above the new brass load) and still average.
I would have thought this would have compensated for the 1gr case volume difference and don’t really want to go any higher above max.

 

[Cahunter805]

Something doesn’t seem right. What powder and bullet are you loading?
Also what dies? Have you setup your FL die to just barely bump the shoulder?

 

[Wodez]

Powder - ar2213sc
Hornady 95gr sst
Redding dies. Set all the way down, just missing the shell holder.
If I was just barley bumping the shoulder back then would I have a larger difference in case volume compared to new brass? Which would make this original problem worse?
Or is it a case of having to fireform new brass even if full length sizing?

 

[Cahunter805]

I normally setup my die to just bump the shoulder. You could be pushing the shoulder back quite a ways depending on your setup.
I screw the die in to touch the shell holder with that ram all the way up. Then back the die up a full turn. Take a fired case and size it. Keep measuring using a headspace gauge and sneaking the die down until I get about .002 bump. If you don’t had a gauge you can soot the shoulder or color it and keep adjusting til you see it make contact and then check that the brass will chamber.
Have you tried your load with new brass again to verify your in the node?

 

[Wodez]

Stumbled across my own old thread with a question that went unanswered. The notification must have skipped through my email.
Still unresolved issue due to me shooting bow mainly and leaving the rifles at home.

I am about to go down the same path with my 300wm- new Peterson brass load development.
Hopefully I don’t find the same issue with the larger round. I’m thinking the difference in case capacity being a smaller percentage it may not show as much.
While I’m at the range I’ll be trying the 243 again with once fired brass. 4th time lucky.

I have verified the new brass load. Although not as good as the first group it still shot better than anything I have shot with fired brass, including those where I changed powder weight up and down .5gr and .8gr

 

[Pickettpuncher]

Since you revived your own old thread…..

Have you ever measured new brass and compared the numbers to once fired? What I’ve found, especially with cheap run of the mill stuff, like Remington, Winchester, Hornady, and federal, is that the headspace is pretty short. I’ve not used Peterson, but they do make a long version for their belted stuff which allows you to headspace on the shoulder instead of the belt. My guess, is unless you get the long version, they’re all short on headspace a bit to ensure it fits in the gun. With full length sizing, you’ll not get the headspace measurement back to virgin brass from once fired, unless you take some off the die or use small base dies. I’m still not sure small base dies will get it back to virgin headspace. Measured some Norma brass I have, comparing virgin and once fired, and there was over .020 difference. I don’t know that that’s enough for a grain difference, but it’s a change for sure. Take the whole case and how much it swells and what actually gets sized and it could be enough for a grain.

 

[Wrench]

Im not picking up what you're putting down. His headspace is measured from the belt to the case head.... which isn't going to change.

Case volume may change on once fired based on your chamber dimensions. A tight chamber may be incredibly close to your die size and a more modest one my be a thou or two over.

Other issues arrise from firing such as primer seat depth, neck tension (anealed or not), brass flow and case length. These can affect case capacity, but in the example of the 300wm, the difference should not cause a node change on a single firing. Neck tension may show a accuracy shift.

I suggest using a chronograph to dissect your results to figure out if it's velocity reduction, deviation or an anomaly.

Shooting conditions can play a part and LOADING conditions are an overlooked source of deviation as well. Humidity matters. Very few consider this.

 

[N.AmericanTrophyHunts]

I recently did a ladder test because I changed to new Peterson brass in my 243w
I found it again liked it hot with the max load. I shot 6 to confirm and was pretty happy with the results. But then I reloaded some full length resized once fired brass and they shot pretty bad. The only difference being once fired.
I did a case volume test on full length sized new vs fl once fired (3 of each) and the once fired had 1gr more volume.
Should I try a little over max load to compensate for the extra case volume?
And why is there a difference in volume if they are both full length resized.

Short answer to this is yes.. Fireform fresh brass to form to chamber, bump shoulder 1-3K. If you size your brass back to SAAMI, you’re overworking it. When your brass is truly fireformed (sometimes 3 firings depending on what brass) add more powder. The goal is for 90-100% load density. Example;
Let’s say (for easy numbers) that your case H2Ovolume with fresh brass was at 50gr and loading 40g of powder gave you a 90% load density. You 1x fire, resize 2k shoulder bump and trim and now you’re at 52gr H2O. Add powder to make the difference and get back into the 90s. Or seat your bullet deeper to get back to an optimal load density. Book max is reference. Your rifle will tell you when you’re at pressure. I have some rifle and loads meet pressure way before book max and some I don’t hit pressure until a few full grains after. Just work it up carefully.

 

[Wodez]

Short answer to this is yes.. Fireform fresh brass to form to chamber, bump shoulder 1-3K. If you size your brass back to SAAMI, you’re overworking it. When your brass is truly fireformed (sometimes 3 firings depending on what brass) add more powder. The goal is for 90-100% load density. Example;
Let’s say (for easy numbers) that your case H2Ovolume with fresh brass was at 50gr and loading 40g of powder gave you a 90% load density. You 1x fire, resize 2k shoulder bump and trim and now you’re at 52gr H2O. Add powder to make the difference and get back into the 90s. Or seat your bullet deeper to get back to an optimal load density. Book max is reference. Your rifle will tell you when you’re at pressure. I have some rifle and loads meet pressure way before book max and some I don’t hit pressure until a few full grains after. Just work it up carefully.

This is the confirmation and solution I needed. I’ll measure the volume and crunch some numbers.
Thanks

 

[Wrench]

The above depends entirely on chamber dimensions. Some guns can easily go back to saami size with little brass movement, some will be 3+ thou off. The capacity offset by seating depth can have ramifications. Seating depth is very critical on secant ogive bullets.

 

[BRTreedogs]

You also need need a headspace comparator set so you can measure the case length to the shoulder.
My 300 win grows the brass 11 thousands on the 1st fire, only but it back 2 tho.
Don't over think it if your rifle is not showing pressure signs its not.

 

[35WhelenAI]

Did you check case volume with water on your .243? One grain of water is minuscule with respect to the amount of powder (weighs less per the same volume) it would take to fill that space. You should not do a thing to your powder charge to compensate for that. As a percentage of total case volume it's a moot point.

With respect to a magnum, I've set my 300 Win Mag to headspace on the shoulder as close as possible after the initial firing. Initial firing makes the perfect case for the chamber. Touch the case as little as possible with the die until the round chambers freely. The belt still takes care of the job at the back but keeping it as close as possible upfront works the brass less. Because the round headspace is on the belt, I've always wondered if chamber dimensions for the magnums with respect to the finished product aren't as uniform as one that head spaces on the shoulder.

 

[Wrench]

It's a lot easier to control the machining from the belt to the case head. There's no tapered flutes to match grind nor taper for inches. The rest of the case reamer can be tricky to finish.

 

[Wrench]

One of my primary arguments to the brass capacity arguments is Ackley cases. I've built several and they always shoot well with both parent and formed cases.