Question about velocity from new to 2x fired brass

[washingtonhunter121]

So Ive been reloading only for a couple years now and have a question pertaining to velocity. I worked up a load that I am planning to hunt with. Shot my test loads to confirm which exact load I was going to shoot with 2x fired brass and chronographed the velocity. Now I had 100 brand new brass at the start of this process and only used 36 to work the load up neck sizing only between loading the test loads. Now once I find my exact load I go up to the loading room and load all 100 up including the rest of my brand new brass. The next day I go to the shooting bench to 0 my rifle at 200 while also taking more chronograph readings to try to get s better average. I notice on about shot 4 I'm getting a large variance between shots. I think of the only difference is the new brass so I test the theory and come to the conclusion that the new brass on average was 35-40 feet slower then the 2x fired brass that was only neck sized after being fired. So I guess long winded but does anyone have experience with this to tell me this is a normal occurrence? Or do I have to go back to the drawing board? Hoping I don't have to start pulling bullets! Thanks for the help appreciate it

[Bwana Bob]

Your new brass is expanding to fill your chamber and that were the vel difference is coming from. Your 2x fired neck sized brass is a perfect fit for your chamber and it gives a bit more velocity. I usually fire new brass once before I use it for load work-up. Hope this helps.
 

[washingtonhunter121]

I was thinking along the exact same lines about the fire formed brass having more
Consistent pressure and fit in the chamber but just had to ask to confirm since I haven't done a ton of loading. Ya I knew not to test loads for accuracy in new brass but I want these loads to be my hunting load and don't like the variance so I will probably shoot the new brass out to fire form them. Neck size them down and be able to use them for the upcoming season. Thank you for your response 👍

[birddogdad]

not sure of all your standards... factory vs reload? are you leveling in chrono? distance from barrel same? how close are you loading grains? temps for shooting?  all these can affect outcome...

[washingtonhunter121]

Ya I know what you mean. I try to be conscious of always keeping Chrono level and the exact same distance every time. i do my best to take my time and make sure everything is the same to the best of my ability. Just adding the new brass to the equation was the only change that would be significant then something minor that would drop my ave velocity from 29451 to 2912. I also noticed this and tested the theory out and it held up so it would seem odd that just my powder in my new cases were off enough to change my velocity like that when I loaded a 100 rounds at once and was just zeroing in at 200 as well as checking my velocities to get a more accurate Chrono readings for everything.

[washingtonhunter121]

2951 not 29451 😁

[JackOfAllTrades]

Fireformed brass will generally have less velocity deviation too. And... When you first worked your load up, what were the local weather characteristics?  If your recent tests where this holiday weekend on the west side, The weather has changed a lot.  Some powders are more temperature sensitive than others.

-Steve

[washingtonhunter121]

I chronographed the first velocities Sunday then the next velocities were taken yesterday. Probably a 5 to 7 degree temp change. I was more trying to confirm if I was correct in thinking that the fire formed brass would be a little faster then the new brass that had not been fire formed yet. I was guessing this but needed a little confirmation for myself in that aspect. Made sense to me that the fire formed brass would perform better then the new but do not have a ton of experience in the loading process to know for sure. Just needed a little wisdom from some experienced reloaded 😄😄

[JackOfAllTrades]

OK, so there wasn't a temperature issue. Cool.   But yes, as new brass, or even sometimes full length resized brass takes that micro second to expand to the chamber walls, some pressure is not fully recognized as quickly as a cartridge that is already expanded to that chamber wall. The propellant to air ratio is also different. Subtle as this may be, a +50fps change is often experienced.

-Steve

[JimmyHoffa]

   The energy that isn't going into forming the brass is going to the bullet.

[washingtonhunter121]

Perfect thanks guys. Like I said it made sense when I thought about it but just needed that re assurance!

[magnumb]

OK, so there wasn't a temperature issue. Cool.   But yes, as new brass, or even sometimes full length resized brass takes that micro second to expand to the chamber walls, some pressure is not fully recognized as quickly as a cartridge that is already expanded to that chamber wall. The propellant to air ratio is also different. Subtle as this may be, a +50fps change is often experienced.

-Steve

 .........you ever notice that competitive offhand shooters always point their muzzles to a rather high point before slowly lowering their rifle to the offhand position they will eventually shoot from....?  They are allowing all of the powder in the chambered case to assume the same position in each and every case that they fire.  The powder is backed up against the primer and when ignited, the powder and air space left in the case are then as identical as they can possibly be which helps with the overall consistency necessary to get the most desired results.

During a study of non-compressed loads, participants brought their rifles to the offhand firing position from all angles possible to ensure that the powder inside the cases were never uniformly leveled out as per the 'accepted' protocol for shooting offhand.  What they found was that there was up to a 150fps variance in MZ when various angles were used in setting up for offhand shots.  The 150fps difference was exceptional, but 50-75fps variances were not. 

Before I read this article a # of years ago, I already tried, as best I could, to find the right combination of components that would allow me to have compressed loads.  It had always made perfect sense to me that the amount of powder in the powder column should make a difference when comparing a compressed and non-compressed load. 

I do know that my compressed loads are consistently more uniform in accuracy and MV than loads not compressed.  There are some cases that don't lend themselves to compressed loads, but I've spent many a day and dollar trying to make it so.

YMMV.........


As to fire-formed brass...........obviously dependent on the charge, new brass takes from 2-3 firings to become totally fire-formed.  Do I hunt with once fire-formed brass...?  Yep.  Has it caused me any issues or concerns or missed opportunities.....nope.  I just goes to show that above and beyond 'Handloadin 101', there is much more involved that we never even consider as being a possible issue or explanation to our accuracy concerns or woe's.

After 40 years of handloadin', I learn something new each and everytime I sit down at 'my bench'.  I don't expect that to change in the years remaining......either.

Good luck to all....... 

[washingtonhunter121]

Thank you for the wisdom magnum. I'm new in the game and trying to soak up all the knowledge I can. It is a fun and rewarding experience to load and shoot. So many things to learn and improve upon in that arena but s fun process to go through.

[Stein]

The other possibility is your chrono, they really are not as accurate as most of us would hope.

I notice no POI changes with new, 2x or 5x brass at all.  I started mixing headstamps and don't even notice anything there out to the max I shoot at a range which is 300 yards.