I have a load which prints 4 shot 1.5" groups at 300 meters. The brass is WW Super. After sizing new brass in a die set for the chamber of my rifle, is there any appreciable loss in accuracy between fireformed and new brass loads?

The cartridge in question is the 7RM. The rifle is based on a Sako L61R and a 26" Hart barrel. In short, a capable hunting rifle but not a benchrest rifle.

Bobby B.

with fire formed brass to the chamber it should yield better accuracy. first off if you just neck size you will gain more volume than with a fl resized case that may affect the accuracy better or worse, you need to shoot to determine which. If you follow good benchrest loading methods your accuracy should be better.
dave

The difference will depend largely on how loose your chamber is. As a rule of thumb, neck sizing is generally more effective in increasing accuracy in looser (factory made) chambers. A chamber built tight in a custom gun will not allow as much brass expansion and will work to accuracy's advantage in two ways. Firstly, the FL sized cartridges (most especially those formed in a die made to conform to the exact chamber size) will not move around in the chamber as much as in a factory gun. Secondly, the brass is not worked as hard in sizing and is yet returned to a known size and internal volume, as opposed to neck sized brass which is allowed to expand and retract as it will, leaving an unknown internal volume.

The difference is negligible until and unless you are shooting for match grade accuracy. The use of body bump dies can also return cases to a more predictable volume.

Generally, I use Redding neck sizing dies. However, my 7RM dies are FL RBCS adjusted to neck size only. Having said that, Adjusting the die to only neck size is the same as adjusting the die to FL resize; strange coincidence I've never encountered before.

I'll simply bang off the first time loaded brass as 'gong bongers' then reload them to spec.

Bobby B.

You should be fine just bumping the shoulder, assuming that is what you mean by set to the chamber of your rifle. I had a 300 WSM that liked virgin brass the best. But that has been the exception to the rule in my experience. The same platform,the same manufacturer of the brass, the same dies, the same reamer, just a DIFFERENT barrel, and a DIFFERENT lot of brass, liked the brass that had been fire formed, and shoulder bumped the best. You should be fine the way the you are going at it.

PaPa 260

I used to be a fanatic about shooting only once-fired, neck-sized brass in my rifles to assure the best accuracy. But over the years I have found that the first loading of new factory brass frequently does just as well, and sometimes better, than my carefully custom tailored brass.

I always neck size-only (usually with a Lee Collet die) when the rifle, load, and brass will allow as this helps brass life considerably, but it is usually a toss-up between new and neck-sized brass for accuracy.

Truing cases in particular neck turning, so it's true with the case body goes a long long way for accurate cartridges.IMO !. Maintaining it with neck sizing and if necessary bumping the shoulder slightly so as to relieve tight chambering issues .

You should be fine. I had a 300 WSM match rifle that actually liked new brass the best. But that is an exception to the rule IMHO. I always full length resize with no accuracy issues. Just set the die to bump the shoulder and you will be fine.

PaPa 260

I should been more clear about what I was driving at. The load producing the 300 meter 1.5" groups utilized brass fired once in my 7RM then loaded with 168 VLD, Retumbo powder, WW Super brass and WLRM. What I was curious about whether new brass will produce the same accuracy as firefomed brass will with the other components held constant.

Bobby B.

I was going to say 1.5" groups at 300 M and you are wondering how much better it will get!!!

I'll see if I can get this right. What I really meant to ask was "Will be a difference in accuracy from fireformed brass to new brass in the same rifle using the same components?" In other words, do I first need to fireform new brass to achieve the accuray levels of fireformed brass or will new brass provide the same accuracy as fireformed brass if all the same reloading components sre kept the same?

Bobby B.

Bobby B.

If I had posed that question, I would be satisfied that I got some good answers. I think your question was understood. Merg

Hey Bobby, At first glance I tend to agree with what "hivelocity" originally posted. For me, I've found that P-FLRing the case makes for more accurate Loads in Blind Comparison Testing. It is because that forces the CenterLine of the Case to be in complete alignment with the CenterLine of the Chamber. Neither FLRing or NSing do that.

quote:

Originally posted by Stonecreek:
But over the years I have found that the first loading of new factory brass frequently does just as well, and sometimes better, than my carefully custom tailored brass. ...

I pulled this comment out because it is not the first time I've seen it mentioned. Long, loonnng ago we had a poster named "Mike375" who (I think) was the first person to mention this phenomenon.

When I think about what is happening in the Chamber during the Firing Sequence, it is not logical that "new un-fired" cases would provide better accuracy than Weight Sorted, Fully Prepped Cases, custom tailored to a particular chamber. I've not seen it happen in any of my rifles, but I have no reason to think the people who see it are pulling a clinton on us.

With that in mind, I do not know if your reloaded cases will shoot better for you than "new un-fired" ones or not. Only way you will know is to shoot them and see for yourself.

Best of luck to you.

I received an email not long ago about a new 1000 yard record group. I read the article and the gentleman was using brand new brass with a load he had never chronographed. He shot a 10 shot group at 1000 yards that measured just over 3".

He stated that the brass was brand new and I don't know if he even sized it before loading it.

I don't have the link anymore, but I'm sure it can be Googled............

It does make more sense that once fired brass that is partially neck sized only would produce the best accuracy and Hot Core states the reasoning.

Thank you all for your replies. Sincerely, I do appreciate them. Nonetheless, I do believe that my questions are being misunderstood. Obviously, I am not presenting them very clearly. Please allow me to clarify,

With a certain load, which includes fireformed brass, my rifle is shooting 1.5" 4 shot groups at 300 meters. If I duplicate this load using virgin brass, can I expect the same accuracy?

Bobby B.

quote:

Originally posted by Bobby B.:
Thank you all for your replies. Sincerely, I do appreciate them. Nonetheless, I do believe that my questions are being misunderstood. Obviously, I am not presenting them very clearly. Please allow me to clarify,

With a certain load, which includes fireformed brass, my rifle is shooting 1.5" 4 shot groups at 300 meters. If I duplicate this load using virgin brass, can I expect the same accuracy?

Bobby B.

You'll probably get the same or maybe better accuracy.

I think

quote:

With a certain load, which includes fireformed brass, my rifle is shooting 1.5" 4 shot groups at 300 meters. If I duplicate this load using virgin brass, can I expect the same accuracy?

I think it depends on luck, the gun and a lot of other factors. I have a target load worked up for my .300 Win Mag that shot a 1.17" group at 300 yards. The load was developed with Winchester brass that had been fired and partially neck sized only along with all the other careful brass prep steps you'll do. I thought I would get some "good" brass and bought some Nosler.

I loaded the same load and got good accuracy in the virgin brass. Not as good as that great group, but acceptable....about 2" at 300. The gun has never grouped to 1.17" since even with the other brass. With the virgin brass at a charge .5 grains lower it shot 3 shots in .8" . Knowing that 3 shots isn't a group I fired shots 4 and 5 which printed high and made the group about the same as the higher + 5 gr. charge.

It will be trial and error and I bet your accuracy will be about the same as with the other brass.

There's a lot of misconception going around about how cases fit a chamber. A popular one is that sizing a fired case some particular way makes its axis align perfectly in the chamber's axis.

Nothing could be further from the truth. First off, the back end of the case has its body pressed against the chamber wall by the spring loaded ejector. Rimless bottleneck cases have their shoulder jammed into the chamber's shoulder centering the front of the cartridge in the chamber; regardless of how the case was sized. Even new rimless bottleneck cases have their front ends perfectly centered up front.

What happens is every round's a tiny bit cock-eyed in the chamber. Belted cases, behave somewhat different becasuse they headspace off their belt when new. Fired belted cases sized such that their shoulder's not set back will perfectly center in the chamber's front end just like rimless bottleneck cases. But their back end's still pushed off center by the spring loaded extractor.

I've tried all sorts of neck and partial sizing wearing out some 30 calbiber magnum target barrels. Nothing shot as accurate as new cases or full length sized cases with their shoulder set back a few thousandths and body sized all the way back to the belt. In other words, resizing the belted case bringing it back to virtual new case dimensions.

quote:

Originally posted by Bart B.:
There's a lot of misconception going around about how cases fit a chamber. A popular one is that sizing a fired case some particular way makes its axis align perfectly in the chamber's axis.

Gotta disagree with this, because it is full of beans.

quote:

First off, the back end of the case has its body pressed against the chamber wall by the spring loaded ejector.

Not if the Cases are Fire Formed properly and P-FLRed.

quote:

Rimless bottleneck cases have their shoulder jammed into the chamber's shoulder centering the front of the cartridge in the chamber; regardless of how the case was sized.

Wrong again. Any FLRed Case has headspace and there is no way the Case Shoulder is "jammed" against the Chamber Shoulder in a Controlled Feed rifle.

quote:

Even new rimless bottleneck cases have their front ends perfectly centered up front.

Since all "new" Cases are shipped at SAAMI Minimum Specs, there is no way even the rankest Beginner should buy into this bologna.

quote:

...Belted cases, behave somewhat different becasuse they headspace off their belt when new. Fired belted cases sized such that their shoulder's not set back will perfectly center in the chamber's front end just like rimless bottleneck cases. But their back end's still pushed off center by the spring loaded extractor.

Actually that would be the Ejector. The rest of the statement is only true if the initial Fire Forming Load was way too low and the Case was not P-FLRed.

quote:

...resizing the belted case bringing it back to virtual new case dimensions.

Finally got one correct, only if it is FLRed.