If you load a brand new case and a once fired case with the exact same primer and powder charge, will they have the same velocity and point of impact??

Assuming the same brand of brass (no Virginia, I don't weigh brass), it'll be close. Not something you'd want to do in a competitive match but certainly within hunting specs.

How about velocity??

Shouldn't be any significant difference in velocity or POI.

Mart

If you are only kneck sizing and running very short free jump on your 1st shot brass your new unfired brass will chrono faster

So what is the advantage then of once-fired brass?

Accuracy

But not if the shoulder is pushed back too much

I bump no more than .005

And this is no guess.....I measure at the C/L datum

Once fired cases may make a bigger difference in belted magnum cases. On my 264WM, the once fired cases have a slightly sharper shoulder. They look almost "improved". I just neck size after that and the consistancy got much better. Velocity was about on par, but accuracy was better since I believe headspacing on the shoulder instead of the belt helped consistancy.

Ugggghhh. This subject comes up occasionally and someone is always assuming that the greater capacity of the fired brass translates into greater capacity of the combustion chamber, which is patently untrue.

The brass case, regardless of whether new, neck-sized, or full length sized, will expand to the size of the chamber. It is the (relatively) inelastic size of the chamber which determines the capacity of the pressure vessel, NOT the very elastic brass case, which you should think of as a rubber bladder inside a water pressure tank, or perhaps a plastic garbage bag inside a garbage can -- it is the can, not the bag, that determines how much volume it will hold.

Hence, all things being equal, pressure, and therefore velocity, will be the same regardless of whether a case is new or once-fired.

Of course, all things are never equal. The case neck will harden with each resizing and thus the bullet pull will be a tiny bit different. There may be a very tiny difference in the time over which the primer ignition occurs since a neck-sized case is held more tightly against the bolt face. There may be other tiny differences. But whether and how much a case body is sized or not sized, new or used, is not a factor in velocity.

In my Blaser R 93 it doesn't seem to make any difference.

I've seen accuracy improvement. I have never seen a difference in velocity between new and once fired. With equal powder charges you are going to have to see an increase in pressure to see a velocity increase. The chamber will determine the pressure not the case.

The advantage of fire formed brass is accuracy, not velocity nor trajectory.

With the same powder charge you won't find any difference. I have found that neck-sizing can give you a bit more powder space but probably not enough to make much difference.

Thanks Fellas! So much knowledge here.

I am having my beloved M70 7mm Rem Mag rebarreled so I am wondering about my once-fired
brass that I have from my old barrel.

I am having it done by Hill Country Rifles...they also blue-printed it for me a few years ago. I am going with a 26" Benchmark 5R 1:9 twist barrel, that I plan on loading with the new 168gr Nosler Accubond LR's.

In all likelihood you'll need to full length resize your fired brass from your old chamber in order for it to fit your new chamber. If the brass is only once- or twice-fired, then there should be no need to anneal the necks and it should act pretty much like new brass when resized. Depending on how tight a chamber HCR uses, some FL dies possibly may not reduce the cases enough, but that's a bridge to cross when you come to it.

Stonecreek,
Instead of FL, what about using my Redding Body Die??

So if the cases chamber in my new barrel then I'm OK....am I correct?

Yes, if the cases will chamber in your new "gun" then they are fine. They will fire-form to the new chamber with the first loading.

quote:

Originally posted by ramrod340:
I've seen accuracy improvement. I have never seen a difference in velocity between new and once fired. With equal powder charges you are going to have to see an increase in pressure to see a velocity increase. The chamber will determine the pressure not the case.

I agree 100%(assuming you are talking new and once fire brass from the same lot- which I'm sure you are).

quote:

Originally posted by Stonecreek:
Ugggghhh. This subject comes up occasionally and someone is always assuming that the greater capacity of the fired brass translates into greater capacity of the combustion chamber, which is patently untrue.

The brass case, regardless of whether new, neck-sized, or full length sized, will expand to the size of the chamber. It is the (relatively) inelastic size of the chamber which determines the capacity of the pressure vessel, NOT the very elastic brass case, which you should think of as a rubber bladder inside a water pressure tank, or perhaps a plastic garbage bag inside a garbage can -- it is the can, not the bag, that determines how much volume it will hold.

Hence, all things being equal, pressure, and therefore velocity, will be the same regardless of whether a case is new or once-fired.

Of course, all things are never equal. The case neck will harden with each resizing and thus the bullet pull will be a tiny bit different. There may be a very tiny difference in the time over which the primer ignition occurs since a neck-sized case is held more tightly against the bolt face. There may be other tiny differences. But whether and how much a case body is sized or not sized, new or used, is not a factor in velocity.

^^^This^^^

As soon as the primer ignites the powder the brass case expands to fit the chamber. This happens before the bullet exits the case and before peak pressure. So, the once fired case and the "New" case will have equal pressures and velocities.

quote:

Originally posted by Leopardtrack:
Thanks Fellas! So much knowledge here.

I am having my beloved M70 7mm Rem Mag rebarreled so I am wondering about my once-fired
brass that I have from my old barrel.

I am having it done by Hill Country Rifles...they also blue-printed it for me a few years ago. I am going with a 26" Benchmark 5R 1:9 twist barrel, that I plan on loading with the new 168gr Nosler Accubond LR's.

I would not use brass from another barrel.You may not get the same fit in the chamber and can get a different POI and alot of fouling.
From the one rifle I chronoed old and new brass with I did get higher velocity with the new brass.It was from a 458 Lott.If I remember correctly it was around 30fps(it could have been noticed with two rifles but it was done repeatedly with the same results).
Yes use your Redding body die if you need to resize.I have reloaded for the 7mmRem mag using Redding competition dies.
I had good results with Reloader 22.

Almost everyone uses brass from one rifle in another - tens of thousands of rounds of it.

quote:

I would not use brass from another barrel.You may not get the same fit in the chamber and can get a different POI and alot of fouling.

quote:

Once Fired Cases....maybe a stupid question but...

In my opinion, there is only one stupid question, and that is One That Is Not Asked.

For me, and I consider myself an average shooter/hunter, this question along with those concerning the advantages of a short action versus a long action, belted versus non-belted, variable scope versus fixed power, synthetic stocks versus wood stocks, the effectiveness or ineffectiveness of the .270 and the list goes on to infinity, I just can not fathom how the average hunter/shooter will or can ever notice any real difference in any of these comparisons/situations.

I admit there is a lot of wisdom/knowledge among the membership of Accurate Reloading and it is the main aspect of the site that attracted me.

But, one of the drawbacks of so much wisdom/knowledge and it is not just on AR or similar sites for it also occurs in everyday life among various groups, is that things go from practical application to things becoming esoteric.

es·o·ter·ic
adjective \ˌe-sə-ˈter-ik, -ˈte-rik\

: only taught to or understood by members of a special group : hard to understand

: limited to a small number of people

To read the various responses to the question, a lot of you folks are super knowledgeable concerning the issue. In real world/real time normal hunting situations, will the average hunter be able to discern any real difference between a factory new case, loaded and ready to be fired the first time and a case that is on its fourth time around, if both are loaded with the exact same powder, exact same weight of powder, exact same bullet and primer, the only difference being the number of times each piece of brass has been fired, on say a white tail deer at 160 yards?

Also, how much of this knowledge, is based on personal beliefs/ideas/concepts?

I agree with Ted. I've measured the headspace on new cases and on once fired cases and some vary substantially. Some brass is very short when compared to other brands. I recall experiencing this with some WW a year or so back but I don't recall the calibre, I think it was .308 Win.

Depending on the brass and the chamber of the rifle there could be little difference or a large difference.

Some of my rifles shoot both well, some don't. I often need to up the powder charge in fireformed brass slightly to match the velocity attained in new brass.

You will need to measure a few things and shoot a few groups to know for yourself. Just because one rifle and brass behaves one way won't imply that another will be the same. Grumulkin's Blaser in .300 Bee doesn't seem to be bothered, but your rifle may think otherwise. And his may behave differently with R-P .300 Bee brass for example.