New Brass vs Old Brass

[ChiefStone]

No sir

You might be over working your brass when you are resizing. If so, then I agree with the others that have said this could be a neck tension issue, along with a slight change in the case volume.

You might want to grab a set of calipers and a Hornady case comparator set so that you can set your resizing die up to only bump your shoulder back ~ .002" from your fired case.

Another experiment would be to anneal a few of your fired cases and see if your group sizes go back down?

 

[Longtine88]

I think there are several reasons this is happening to him but I know from experience that he gained 2% case volume in that nosler brass. I shoot new nosler brass in one particular rifle. Only new until I get a lot load of once fired brass then go through the ladder again to find the node again. It always climbs around 2% between virgin to once fired. I guarantee you this is the main problem along with the no shoulder bumping. I hate trying to dissect a problem when you don't have all the facts or not seeing his loading technique. If he runs a ladder again his node will be higher weight than before.

 

[skipglo]

I tried searching but I guess I don't know what to search for.
My question to the guru's is my groups change from using new brass to old brass. I full length size both my new and old brass. Use same load, same bullet(I weigh the bullets). My group size at 100 yds is 3/4" with new brass and 1.1" group with old brass. I have verified this doing it more than once. What causes this?
Thanks!

As Rick said ...neck tension but also case stretching during fire forming would be another factor i would think....test with a little extra powder!

 

[Roninco]

I find it takes about a 1% powder charge reduction loading fired brass to get the same velocity as new brass. Accordingly, if you work up a load using fire formed brass then increase the load about 1% to get approximately the same velocity with new brass. The increased charge provides the necessary pressure to fire form the new cases. This of course assumes you have no pressure signs in either load.
As stated earlier, it is important to know how much you are resizing your cases. This will prevent over sizing the brass, lengthen case life, and provide better consistency.

 

[Oklahunter1]

I appreciate all the info! I'll let you know what I find.

 

[LRNut]

I always thought new brass gave reduced velocities, but last week I chrono'd some Lapua loads with new brass and got exactly the same velocity as old. FWIW, I anneal every time with AMP and use a mandrel, but that said, new brass always seems to have higher neck tension; perhaps that "evens" things out. Again, it was only one test.

I was out practicing at 500 in the wind yesterday. One of my rifles is a 300 RUM shooting 200 ABs. Last time I shot that rifle was Sunday and the last shot was 3188. I went to shoot and discovered I was out of "old" cases and had nothing but new ones to shoot, so I went ahead and fired. Velocity was 3188, exactly the same as the previous shot with "old" brass.

 

[cdherman]

I don't think there is a general rule about how shooting new brass versus fired brass behaves in terms of accuracy and velocity. What is clear is that there will be variation between the two. I try to pretty much work up loads using neck sized brass that has been once fired in my gun. I get the most consistency that way. But other people approach it differently.

There are guys that anneal and FL resize every loading and swear that gets them the best accuracy. What I know is that FL resizing every time will eventually result in stretch and your case will eventually separate. I don't like that at all.....

 

[LRNut]

I don't think there is a general rule about how shooting new brass versus fired brass behaves in terms of accuracy and velocity. What is clear is that there will be variation between the two. I try to pretty much work up loads using neck sized brass that has been once fired in my gun. I get the most consistency that way. But other people approach it differently.

There are guys that anneal and FL resize every loading and swear that gets them the best accuracy. What I know is that FL resizing every time will eventually result in stretch and your case will eventually separate. I don't like that at all.....

I don't know of too many competitive shooters that neck size only; one of my smiths shoots F class and he says if your bolt is closing hard your accuracy will suffer. If you neck size and have somewhat hot loads, it will be difficult to close and open the bolt.

Brass life can be funny; I bump everything back 2 to 4 thou depending on bolt closure pressure. My 28 Noslers never separate. I don't recall ever seeing a Lapau separate and RUMs are pretty rare. What isn't rare is to have my Edge cases show enough of a ring that I discard them. I am not setting them back that much either. Then again, the loads are pretty hot.

 

[cdherman]

I don't know of too many competitive shooters that neck size only; one of my smiths shoots F class and he says if your bolt is closing hard your accuracy will suffer. If you neck size and have somewhat hot loads, it will be difficult to close and open the bolt.

Brass life can be funny; I bump everything back 2 to 4 thou depending on bolt closure pressure. My 28 Noslers never separate. I don't recall ever seeing a Lapau separate and RUMs are pretty rare. What isn't rare is to have my Edge cases show enough of a ring that I discard them. I am not setting them back that much either. Then again, the loads are pretty hot.

Perhaps some terms need to be clarified. Strictly speaking, I have always thought that if someone says "Full length resized" then they are taking the resizing die down to the shell holder.

If they adjust the die to bump the shoulder .002", then I would call that a partial resizing. That's actually what I aim for as well. I don't always start bumping back the shoulder after the first firing, but always do so after second etc....

If the OP means just shoulder sizing with the term "Full Length" then I think that needs to be clarified.

 

[Oklahunter1]

Wanted to update everyone. I finally got a chance to shoot again and tried what roninco suggested and increased my load 1%. Went from 51.5 gr to 52 gr. When I did my group shrank back down to less than moa. I made no other changes. At least for now I think I'm set. Thanks for everyone's ideas. I really like a forum where guys are really willing to help someone out!

 

[scope-eye]

I bought some brass from a neighbor once he was having a yard sale and I asked him if he had any gun stuff "I always ask" He said yes and went inside and when he came out he was holding a clear freezer bag it was 30-30, I asked him how old it was he said I don't know I bought during the Johnson administration. I kid you not that's what he said.LOL
I sill have it.

Dean