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Author Topic: Virgin brass vs. once fired  (Read 525 times)

Offline Crunchy

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Virgin brass vs. once fired
« on: January 20, 2021, 01:33:12 PM »
So I developed a really good load while fire forming virgin brass.  It is shooting 1/4 Moa at 200.  Today I had reloaded 8 pieces, and shot the last 3 of virgin brass.

Virgin brass still holding 1/4 Moa.  Once fired reloads opened up to roughly 3/4 Moa. 

Virgin brass ES of 11 SD of 5.7
Reloads ES of 34 SD of 11.

Should I run another ladder over the chrono now that the case volume has changed from virgin to once fired?  Maybe the sweet spot powder charge has changed from virgin to once fired?  Just curious what might have opened up the load.

Offline birdshooter1189

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Re: Virgin brass vs. once fired
« Reply #1 on: January 20, 2021, 01:50:03 PM »
I have a hard time believing the case volume is changing enough to have any effect on velocity.

I would suspect it might have more to do with neck tension and the brass hardening or softening after being once fired.

Could also be your test batch size....perhaps the spread didn't show up in a 3 round string but it did show up in a 8 round string.

Other possibilities could be barrel heating up, or barrel getting dirty.

Offline Stein

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Re: Virgin brass vs. once fired
« Reply #2 on: January 20, 2021, 02:17:13 PM »
I haven't experienced that, I would try it again to verify it's the once fired issue and not something else.

Did you full length or neck resize?

Offline callturner

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Re: Virgin brass vs. once fired
« Reply #3 on: January 20, 2021, 02:20:22 PM »
 :yeah: Did you anneal your brass? Was it annealed before? What brand is it? Lots of variable's.

Offline buckfvr

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Re: Virgin brass vs. once fired
« Reply #4 on: January 20, 2021, 02:33:22 PM »
Did your average velocity remain the same ?  If not, match once fired velocity to virgin velocity.

Offline Buckjunkie

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Re: Virgin brass vs. once fired
« Reply #5 on: January 20, 2021, 03:14:49 PM »
I have several rifles that like (good quality) new brass and the rest don’t seem to care.

For this rifle, I would either shoot all virgin, or start over working up a load with 1x + fired brass.

Offline Crunchy

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Re: Virgin brass vs. once fired
« Reply #6 on: January 20, 2021, 04:16:10 PM »
Did your average velocity remain the same ?  If not, match once fired velocity to virgin velocity.

the reloads averaged 8fps faster than the virgin brass.  I would note that this round of shooting was about 50 fps slower than previous.  I assumed it might be because of the temp difference.  Guess I need to load another batch to figure out what is going on.  Everything is the same.

Offline Crunchy

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Re: Virgin brass vs. once fired
« Reply #7 on: January 20, 2021, 04:17:27 PM »
:yeah: Did you anneal your brass? Was it annealed before? What brand is it? Lots of variable's.

It is ADG brass, came looking as if annealed. I anneal every other firing so I have not cycled enough brass to anneal yet.  Next firing I will.

Offline Crunchy

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Re: Virgin brass vs. once fired
« Reply #8 on: January 20, 2021, 04:20:47 PM »
I haven't experienced that, I would try it again to verify it's the once fired issue and not something else.

Did you full length or neck resize?

I full length resize.  The groups are night and day from virgin to reloads.  The virgin brass might be less than 1/4 Moa it is shooting great at 200.  At 100, three shots are one hole.  the reloads are prob .75 Moa so I know it is not me.

Offline NWShooter

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Re: Virgin brass vs. once fired
« Reply #9 on: January 20, 2021, 08:37:43 PM »
Fairly simple. Shoot “Virgin” brass. Next would be to work on the shoulder bump as per the chamber dimension.
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Offline Magnum_Willys

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Re: Virgin brass vs. once fired
« Reply #10 on: January 20, 2021, 08:48:35 PM »
Yup can be frustrating.  Have a 338-378 that with virgin brass I just have to fill with powder,  stuff bullet in and shoots 1/2 moa out to 1000 yards.  Difficult to match with resized brass tho tried many ladders, loads, tensions and annealing every time.  Took 3 different dies before I found one and a load that matches virgin accuracy.   Its a hunting rifle so I just use virgin brass.

Offline bugs n bones

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Re: Virgin brass vs. once fired
« Reply #11 on: January 20, 2021, 09:00:05 PM »
Long story short... if your brass is fire formed in your weapons chamber , you then neck size only second go around . 99.9 % time that always has a better group .

Offline Crunchy

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Re: Virgin brass vs. once fired
« Reply #12 on: January 20, 2021, 09:03:18 PM »
Fairly simple. Shoot “Virgin” brass. Next would be to work on the shoulder bump as per the chamber dimension.

I am only bumping the shoulders back 2 thou.

Offline Crunchy

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Re: Virgin brass vs. once fired
« Reply #13 on: January 20, 2021, 09:06:14 PM »
Yup can be frustrating.  Have a 338-378 that with virgin brass I just have to fill with powder,  stuff bullet in and shoots 1/2 moa out to 1000 yards.  Difficult to match with resized brass tho tried many ladders, loads, tensions and annealing every time.  Took 3 different dies before I found one and a load that matches virgin accuracy.   Its a hunting rifle so I just use virgin brass.

I loaded up another ladder.  The load in virgin brass is 67.6 grains of H1000. So I am starting at 67 and going to 68.5 in .3 steps.  Hope to find the "magic" again.

 


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