I need to fireform 100 new cases and have limited time. It would be efficient if I could load test simultaneously, but I'm concerned that I'd reach excess pressures when approaching max charges with bullets in the lands. Would removing the ejector pin help keep the casehead against the bolt face? This is in an older (L61R) Sako belted mag. Any thoughts or suggestions?

What caliber are you loading for and what the is the base case

7mm Rem Mag, before and after. Seeking best accuracy, head spacing on the shoulder.

Are you just wanting a batch of 1X brass? If so, I'd just set my bullets just off the lands per normal and work on my accuracy loads and let the fire forming take care of itself. It's always worked for me.

Re wasbeeman's post:

There is a definite lack of concurrence as to whether the ejector and firing pin push the case forward and therefore interfere with proper fire forming. I wish I had an answer. I don't have the necessary measuring tools to do the test. If anyone has done so, I would love to see the results. In the meantime I must assume the worst.

if your loads are so close that you are worried about this, you have other problems .

back off a couple percent --

Since your caliber is a belted mag (7 mag) which headspaces on the belt, your cases being fireformed from new to 1x fired are going to go through a radical transformation in case volume no matter what you do (unless you have one of those very rare hydraulic form dies).

IOW the new case will travel from .002" to .010" (averaging here) forward until the belt stops forward movement. The shoulder, however will expand forward from .015" to .040" (depending upon chamber size and new case dimensions). It won't matter if you have seated the bullets to the lands or created a false shoulder, the internal volume of your case is going to change.

IMO seating into the lands to prevent forward case movement is a false hope anyway. The firing pin strike and the subsequent explosion of the primer into the primer pocket WILL push the case forward and seat the bullet until the case belt hits the chamber stop anyway. I suppose if you put a serious crimp on the bullet and seated into the lands then that might mitigate, lessen or alleviate the forward movement, but that heavy crimp will create issues of it's own.

I once did a test on a multiple fired case that was fully expanded and fit the chamber with no slop (slight crush fit) and just a primer. It set the shoulder back .0015". The primer pocket is mostly closed in with only a small hole so much of the force of the primer is exerted on the inside of the primer pocket until the primer pressure escapes through the hole into the case. I read somewhere that primer psi measured at the muzzle can reach 400 to 500 psi. Do you think a bullet will stop that?

Especially a belted mag case needs to be fired at least 2x if not 3 or 4 before internal volume stops increasing.

Of course there is a small (miniscule IMO) chance that you would find a load with new cases that would not change from what you get with fired cases or that the variance would be insignificant. But I don't see how that could be predicted beforehand. IOW you can find a good load with new cases and have it be repeatable ON NEW CASES. But you'd best plan on verifying and working on a load with the expanded cases later.

JMHO

Just stick to normal practice.

New lot of brass = new component. So start with a lighter load & not max.

Now you have fire formed cases and you should neck size only to base of neck and make sure the shoulder is not pushed back too far. NOTE - if you do not size it enough, the shoulder will move forward!

With correctly neck sized brass you can try for full power loads.

Since it is a hunting caliber & rifle, I would keep the bullets 0.030" off the lands for safe & reliable hunting ammo. I do not load hunting bullet close to the lands like target or varmint ammo.

My Basic Principles - Hunting ammo should first be safe. Secondly it should fit the magazine reliably every time and third comes accuracy. Max velocity is a nice to have - depending on your rifle and what it likes.

Accurate, high velocity ammo is useless if it will not fit your magazine or if it is unsafe.

I certainly agree with Naki regarding the standards for hunting ammo. The objective in this situation is accuracy, not max velocity. I'll be using Redding Comp Neck and Seating dies.

I tried to sell the shooter on a 280 Rem or 280AI, but no such luck. So my idea is to treat the case as if there was no belt, but to do so the shoulder must be set forward. I'm trying to find a way to do that efficiently and safely. More testing is obviously in order.

No. If you are really fire forming, and want the case to fit and not stretch, regular firing will not do that; as the firing pin will drive the case forward, if you have any extra space.
True fire forming, if there is any extra space (I am not calling it "headspace"), is done in one of two ways; seat a bullet hard into the lands, or form a false shoulder. SAAMI tolerances allow belted mags about .017 between a max chamber and a min brass. Do not use grease on the case. I know, some say it works.

Obviously the ideas you have intrigue you but truth be told, you're talking about a factory rifle shooting hunting ammo. Much of the esoteric info you've been given is designed for ultra precision rifles where to shave 1/8" off of your groups is occasion for celebration.

Remember that the belted magnum is designed to head space on the belt. So jamming the bullet in the lands is not going to make any difference to the stretching of the brass at the shoulder! The base of the case is already firm against the bolt face & cannot move further forward.

By using the bushing type neck sizing die you are head spacing on the shoulder like all rimless cases.

One other point, I always do full prep of new cases, including sizing. Yes some people do not bother with that extra work on new cases. But I have found a lot of variance in new brass with plenty of case mouth dings which will scratch your bullets at the time of seating & affect accuracy. You will be chasing your tail as an otherwise perfectly accurate load may produce flyers due to scratched bullets & dinged case mouths! Same goes for dented bullets from dropping a box on the floor etc.

Neck tension will also be variable with new brass & so they need to be sized before the first load.

Ignore the belt and make it seat on the shoulder, like all rimless cases do. Relying on the belt is the cause of all the brass problems in belted cases. Naki, please re-think what you said; jamming the bullet into the rifling will certainly insure that the shoulder moves forward, and the brass does not stretch in the middle, just like fire forming any wildcat.
Even though the belted cartridge is "designed" to headspace on the belt, there is so much built in tolerance there that you are guaranteed to stretch cases if that is what you rely on.

"Brass is already firm against the bolt face".
Not likely unless you are lucky. Look up the SAAMI tolerance allowed between chambers and brass; it is over two times the "allowable" normal headspace tolerance.
It is .015.
Since we can't change the belt length, the only thing we can change is the base to shoulder length, just like any rimless case.

Thanks everyone for the help. Just to let you know:

I'm using new Nosler brass. I've read that it is supplied by Norma. Anyway, Nosler is the best, in terms of weight and dimensions, I've ever encountered. Can't say about the metallurgy. Nevertheless I will be neck sizing with a bushing die, to assure consistent neck tension, among other factors.

I'm well aware that fire forming is gilding the lilly for a hunting rifle, but the accuracy is a bit of an ego thing for the shooter (not me). He seldom practices, but wants to receive that little piece of target with a bug hole in it. I'm retired. There are worse things I could be doing.

Fire forming on belted mags, using wildcat forming methods, is not for accuracy, as much as brass longevity.

Use the cheapest bullet you can find, use a moderate charge of the fastest recommended powder for the caliber/bullet, seat it way out into the lands and fireform as a separate operation.

You are just not going to be able to safely fireform hunting loads while testing to the degree you want to get the brass fireformed. Too close on pressure and too much of a chance of sticking a bullet in the lands and dumping the powder in the action if you have to eject an unfired round.

Or just shoot your good safe hunting loads and have pretty good fireformed brass and resize it off of the shoulder next time.

You are wasting your time if it is accuracy that you are after. Your field positions will cost you more in accuracy than the less than perfect ammo.

quote:

Originally posted by Brice:

I will be neck sizing with a bushing die, to assure consistent neck tension, among other factors.

If you have excellent and very consistent neck thickness then you are good to go

If your neck thickness varies at all you need to outside neck turn or leave the expander in the bushing die

I will be checking the neck wall thickness and will trim the high spots if needed. We will see how consistent the Nosler brass is in this respect.

The Nosler brass arrived. I neck-sized it with a Redding .309 bushing and measure the wall thickness. Varietion was about .013 t0 .014".

I hope to test two fire forming methods this week.
-With bullets well into the lands
-With bullets off the lands, perhaps .050"

I will post results, measured with an RCBS Precision Mic.

I've fire-formed cases and worked-up loads at the same time, many times.

You can do it safely, while seating the bullet into the lands, although with a belted magnum seating into the lands seems unnecessary.

Work-up from well below, looking for pressure signs and monitoring velocity at the same time.

When pressure signs show-up or excessive velocity occurs...stop.

quote:

Originally posted by Brice:
I need to fireform 100 new cases and have limited time. . . . Would removing the ejector pin help keep the casehead against the bolt face? This is in an older (L61R) Sako belted mag. Any thoughts or suggestions?

First, the ejector on the Sako L61R is a fixed blade that sits at the rear of the action. It is totally uninvolved with the case head when a case is chambered.

Second, while the Sako is typically one of the more precision built and accurate hunting rifles, you are unlikely to be able to discern any difference in accuracy with brand new cases versus "fireformed" cases. In fact, new (or full length sized) cases often yield superior accuracy to fired, neck-sized cases in hunting rifles, probably because of better concentricity with FLS cases compared to some neck-sizing methods. At any rate, using "fireformed" cases won't turn a 2-MOA gun into a half-MOA gun, or even a 1-MOA gun into a 3/4-MOA gun.

The belt will limit the stretching of cases to some degree. In fact, the tolerance between the belt and the belt rebate in the chamber is almost always less than the tolerance between the shoulder of a rimless case and its datum point in the chamber.

But regardless of whether you find a way to limit case movement on the first firing or not you're going to end up with essentially the same fireformed case. If the case is allowed to move forward due to headspace tolerance (no matter whether it headspaces on a belt, a rim, or a shoulder), then it will stretch rearward at the pressure ring (about a quarter-inch forward of the rim). If it is held more tightly in place with something like a false shoulder (the only reliable method), then the stretching will occur in the forward end of the case, which is a bit more desirable in terms of case life, but amounts to the same thing in terms of case-to-chamber fit.

Jamming a bullet into the lands will NOT prevent rearward case stretch. Jamming is only a useful method when headspace is overly long to provide positive firing pin contact. As others have pointed out, when the primer ignites the case will move forward, anyway, since the bullet's grip at the neck won't be sufficient to hold it rearward.

Bottom line: Develop the loads for your Sako in new brass and pay no attention to whatever overly generous headspace may exist. Your loads will have the same pressure and shoot to the same point of impact with both new or "fireformed" brass. Once you've fired a load in a new case, be sure that your sizing die (if using an FL die) is adjusted so that it barely kisses the shoulder, if at all. Or, use a Lee Collet die or other dedicated neck-only die if you prefer. Neck sizing-only will extend the life of your cases even though it may not appreciably improve accuracy.