264 Win Mags - When would the brass cases be considered "Fire Formed" for each individual action?

[Alibiiv]

In my experience with belted magnums (264WM, 7RM, 300WM), the base to shoulder on virgin brass is VERY short. My 264WM grew over 25 thousandths on first firing with Winchester brass. My ADG 7 rem mag brass grew 15 thousandths if I remember correctly. These were both in minimum head spaced X-caliber Savage prefits.

With that much stretch happening, it might be good idea to "fire form" with a jammed bullet for the first firing. I did this using some relatively cheap bullets and a mid-level load. One firing got the brass near enough to its full size, with almost imperceptible growth after the second firing with a "normal" load.

If I were you, I'd at the very least check the growth. Measure a virgin piece of brass from base to shoulder, then fire a couple and measure. If the growth is extreme (>0.010") it might be worth using the jammed bullet method, which forces the case head to rest against the bolt face. Otherwise, the brass will stretch backwards and forwards, instead of just forward, potentially thinning the case walls at the web. If the rifles are good shooters, you'll likely get good accuracy out of the fire forming loads, so use them to plink around, get your scope close, break in the barrel, and just have fun.

After the first firing, you'll be able to adjust your die so that you just bump the shoulder back 0.002" or so, and subsequent firing cycles will result in FAR less case stretching, and therefore considerably longer brass life. A small shoulder bump is also probably better for accuracy and precision.

Would you explain the reasoning behind fire forming by jamming a bullet into the lands when a belt accomplishes the same thing. What is the benefit? Jamming a bullet essentially is like forming a false shoulder, the belt serves to do the same thing??? I load a 300 WinMag, after the first firing I no longer use the belt and bump the shoulder back.002-.003 thousandths. My thoughts are that once a full/heavy load is fired the case is pretty much fire formed. I'd fire forming using the COW method i do not consider that round to be fire formed until I put a full load through it. The difference between a COW fire formed case and a full load fire forming is definitely visible.

 

[entoptics]

Would you explain the reasoning behind fire forming by jamming a bullet into the lands when a belt accomplishes the same thing. What is the benefit? Jamming a bullet essentially is like forming a false shoulder, the belt serves to do the same thing??? I load a 300 WinMag, after the first firing I no longer use the belt and bump the shoulder back.002-.003 thousandths. My thoughts are that once a full/heavy load is fired the case is pretty much fire formed. I'd fire forming using the COW method i do not consider that round to be fire formed until I put a full load through it. The difference between a COW fire formed case and a full load fire forming is definitely visible.

Per post #9 and #10...

Not from my understanding. The belt can only keep the case from going forward into the chamber, and the bolt face doesn't "crush fit" the brass against the belt, so there's some amount of wiggle room.

If I'm reading the SAAMI drawings correctly, it looks like the measurement for the cartridge is 0.220" base to belt with a -0.008" tolerance, and 0.220" - 0.227" for the chamber. That could potentially set up a maximum headspace (short belt, long chamber) of 0.015", though such extreme tolerance stacking should hopefully be rare.

For best consistency, the solid belt should never contact solidly against the chamber or you will have issues resulting from bolt preload. Properly built full custom rifle may not have real issues, most factory rifles certainly will. Because of variations in belt thickness, a belted mag chamber should not be set to true zero headspace. As such, most are 10-20 thou long in headspace. When a round is fired, the brass expands to fill the chamber. Once fired, the loader should only size enough so the case chambers easily and no more so that it headspaces off the shoulder, making the belt irrelevant. Fireformed after one high pressure loading.

 

[Carey Farmer]

How many firings for each brass do I need to have true "Fire Formed cases"? I am assuming the brass type will also make a difference but only a few companies make brass for the 264 Win Mag.

As other posters have commented, belted magnum cases are typically 15 thousandths or more short of chamber length, so the front of the case gets work-hardened a bit upon first firing. I anneal .264 Win Mag cases with the flame pointed at the case wall / shoulder junction (rather than at the shoulder / neck junction) to help soften the front of the case. After the first firing, I anneal and resize but shoot to bump the shoulder back only to the same length it was when it came out of the chamber (resizing the case diameter causes the case to grow a couple thousandths in length).

With this approach, my belted cases are typically fully fire-formed after the second firing. After the second firing, I anneal and resize shooting to bump the shoulder back 1 thousandth.

I don't know how many firings it would take to fully fire-form without annealing after every firing.

 

[sesauk]

How do I actually know when I am pushing the shoulder back? I understand that you need to make sure the neck is correct but when do you know if or when you need to push the shoulder back? Some say .001 others .002 which is a better jump or does that depend on the rifle/chamber? or the bullet?

 

[Carey Farmer]

You have to measure the case length at the shoulder with a "bump gauge" and a caliper. Measure before sizing, then size and lightly "bump" the shoulders, then measure again. Adjust your die (or change your shell holder) as needed and try again.

Here's a source for bump gauges: https://www.precisionreloading.com/cart.php#!l=WHID&i=SBG420

Here's a video on how to set up your die for the bump you are looking for:

More bump will more reliably ensure that the case doesn't have to be compressed by the bolt to chamber, but at the expense of brass life.

 

[Fiftydriver]

My procedure is like lost of my procedures, extremely simple, here goes.

- screw your FL die into your press so that there is roughly 0.100" between the bottom of the die and the top of the shellholder.

- Take a fired case and some 0000 steel wool. Clean the neck and shoulder of the fired case using the steel wool by holding the wool on one hand, wrap around the case neck and turn the case with the other, pinching firmly on the case neck with the hand holding the wool. Yes this cleans the case neck but just as important, it leaves minute polishing lines running around the case neck. This makes it very easy to see the die contact points on the case neck.

- lube the case, run it up into the FL sizing die and the. Remove. Clean off lube and inspect the marks left on the case neck. This will give you some idea how far away you are from the case shoulder, should not be touching at this point.

- now check that case to see if it chambers in your rifle. If it does chamber easily, the chamber pressures are quite mild in the load used to fire that round, as such, case will be ready to prime, powder and load if it chambers easily with no real resistence when closing the bolt on that sized case. Often times however, with good top end loads, there will be resistance closing the bolt.

- turn your FL sizing die down into the press 1/10 of a rotation. Relube case, resize and recheck in your chamber. Repeat this process until you go from just feeling some resistance on the bolt when closing it on the sized case to the bolt closing easily. At that point, you know your roughly within 0.005" of having the case set up at 0 headspace in the chamber.

- sometimes you will feel a noticable bump sizing the case to get it to chamber properly. This becomes more common as the case gets more firings on it. New brass will often not give much notice that your bumping the shoulder while you size the brass so always best to go slow setting up the die.

I recommend this set up procedure be used each and every time you set up to size brass.

Also strongly recommend your brass be kept on the same firing number as closely as possible so that you can get consistent sizing of all your cases.

A case with 5 firings on it will need much more shoulder bump when sizing to properly fit in the chamber then a case with 1 firing so to keep consistency with your brass fit in the chamber, best way is to keep them all on the same round count.

Inconsistent chamber fit will generally always cause fliers in factory rifles, not as much in a full custom but still not a good thing just from an ignition stand point.

Really pretty old school but no need for fancy, costly gauges or tools, just need your rifle, brass, some steel wool and your press and dies.

 

[QuietTexan]

How do I actually know when I am pushing the shoulder back?

To keep this higher level - assume what I'm talking about is for factory chambers, starting with once-fired matched brass, and using factory FL dies.

The most common answer you're going to see if you search is to measure using headspace comparators. Measure case, size case, look at the change in measurement. An important point for this process is to only use a case ONCE for measuring. Don't keep resizing the same case multiple times to set a die, use a different (fired-unsized) case for each adjustment of the die.

It should be pretty obvious that you're only sizing the neck at initial set up of the die high off the shell plate - there's usually a visible ring of sizing where the die stops. So leave set the die high to only size the neck for as many firings as it takes until you can't rechamber a fired/un-sized case without pushing down on the bolt. Then resize cases progressively shorter until a case fits, only sizing a case once for a test fit then set aside until the end. Resize all the rest, shoot them all once, verify the sizing spec continues to work. If you anneal it should continue to work. If you don't you'll likely need to continually adjust the die down slightly for several firings. If adjusting the die down to the bottom doesn't solve the fit, there's something else other than headspace going on.

You'll know you're pushing the shoulder back because cases will fit in the chamber differently than before you sized them.

I understand that you need to make sure the neck is correct but when do you know if or when you need to push the shoulder back?

Bolt drop test (what Kirby and I generally described above). I strip the bolt down so it moves freely and doesn't engage the trigger/springs. You'll feel a big difference once you fire a case enough times to NEED sizing versus one dimension being off. It can take anywhere from 3-8 firings depending on the chamber to really fill out a case to where it NEEDS sizing to fit.

There are considerations for function though. Minimally sized case using this process can cause you problems if there's any chance of the case or chamber getting wet. To address functional concerns - you can still set the die using the above process, but then use a comparator to go an additional 0.001-0.003" of shoulder movement to put more space between the brass and chamber.

TL;DR - stop here if you're going to complain later. You were warned.

Trim length comes into play here also, depending on if you're using a cutter that indexes off of the case base or shoulder. Both work, but you can cause inconsistent trim lengths if you trim indexed off the shoulder before shoulders are fully grown/stabilized. 30-06 is what gives me the most problems with this - needs trimming much sooner than anything else I shoot. Some cases I never actually HAVE to trim over the full life of the cases, but compulsive unnecessary trimming is a subject for another thread. So save yourself a headache and if the cases don't jam into the lands when you re-chamber them, don't try to work on trim length and headspace at the same time. You'll end up running around in a circle.

All of what I said is based on what I see as one key fact - a single firing will not grow a case enough to NEED a complete resizing. If it does then IMO you've trashed the brass on the first firing with too heavy a load, your chamber is cut wrong versus the brass you're using, or you've spent so much time on a reamer/die/cartridge that it's perfectly dialed in (looking at @Fiftydriver ). It matters WHERE on the case the sizing is occurring, but that's more in-depth than your "am I bumping" question. To Kirby's point on feeling resistance after a single firing, there are more dimensions than just the shoulder at play. Case head just above the web is a common location that can be sized by certain dies when shoulders are still short of the max - this can cause headspace to GROW on your first sizing, or at very least become inconsistent when still short of max headspace. That leads you into reamer vs die dimensions, neck vs body sizing, and so on until you're the one writing a dissertation that ends in needing a custom die for a $799 Savage Axis II scoped combo rifle because you just know it has a 100-10x in it.