That isn't good.

[Mule3006Elk]

300 WM using Hornady Headspace gauge:

Unfired: 2.255
Fired: 2.275
Shoulder Bump: 2.273-2.274. I bump the shoulder 0.001-0.002.

 

[KineKilla]

300 WM using Hornady Headspace gauge:

Unfired: 2.255
Fired: 2.275
Shoulder Bump: 2.273-2.274. I bump the shoulder 0.001-0.002.

The rifle builder I spoke with said that brass has a total of 0.02 worth of stretch in its useful life. From your specs and mine it appears that we are seeing that 0.02 in the very first firing.

So who makes brass built to a higher tolerance? ADG, Nosler Custom, Norma, Winchester?

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[Mule3006Elk]

The rifle builder I spoke with said that brass has a total of 0.02 worth of stretch in its useful life. From your specs and mine it appears that we are seeing that 0.02 in the very first firing.

So who makes brass built to a higher tolerance? ADG, Nosler Custom, Norma, Winchester?

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Normal for a factory 300 WM after first firing.

Belted "factory cartridges" are made to headspace on the belt. This causes the first firing to blow the case shoulder forward - this can be as much as .020" to .030", and it really stretches your brass (Larry Willis website).

If you don't know this and you bump the shoulder back to the unfired specs: 1) excessively work the brass when you bump the shoulder back only to blow the case forward another 0.02-0.03" when fired again. This will result in a very short case life. I would guess 2-3 firings and you will get case head separations.

When I first started reloading the 300 WM and saw the how much the fire formed brass stretched at the shoulder I was perplexed. More like WTH. I called Redding and they were great. Explained the above to me in detail.

I'm using Nosler brass. Current brass, fired 3-4 times, and still going strong. Running 175 grain LRX 3011 fps. I inspect the brass closely after tumbling/cleaned.

After the first firing, now fire formed, only bump the shoulder back 0.001-0.002. If you do this correctly the brass isn't getting worked much. Due to the shoulder angle on the 300 WM I don't get a lot of brass flow into the neck. Therefore, minimal if any trimming after firing (x < 0.001). My 30-06 on the other hand, shoulder angle is less, I get more brass flowing into the neck, and I usually need to trim 0.003-0.005 off the neck after firing.

 

[KineKilla]

Thanks everyone for their input.

Now that I have measured my new brass, new sized brass and fired brass I believe I will be fine shooting the new stuff for the first time then bumping the shoulder less than I used to be. As of now, I have 16 loaded rounds that have never been fired, 20 that have been fired one time then re-sized (unfortunately sized using my old settings). I think I'll be ok for the hunt that is coming up in a few days if I just shoot the new, never fired stuff.

I just do not have the time to fire form a bunch of brass and then reload it all to the new specs by then. The public range is closed and I have so many other things going on to get ready for the trip that this stress was not helping.

I'm really only taking my rifle along as a backup plan to my bow anyways.

 

[Cahunter805]

I would use the 20 once fired rounds to hunt with. I assume it’s sighted in with your current load already.

 

[KineKilla]

Yeah it is dialed in with this load and actually has the CDS dial engraved to match the load's performance. The rifle doesn't care whether the brass is new, once fired, fired three times, etc. It shoots them all VERY well....as long as it is a 160gr Accubond over 61grains of RL-22.

I was hitting water filled milk jugs at 350 this past weekend with loads that were splitting the brass during the shot. If it weren't for the safety issue, I wouldn't really care what the brass looked like after firing.

I'll utilize the ammo I have rather than unloading it to salvage a few components but will load any new ones differently going forward. My end goal will be to get it back to the same performance as the existing so my CDS turret is still spot on.

 

[KineKilla]

Update:

I measured 4 different pieces of brass from a recent hunt. 3 once fired, 1 twice fired.

The average of them is 2.1185.
2.1185, 2.1180, 2.1175, 2.1190 respectively.
I currently have my die set to 2.119 as mentioned before. Should I be resizing these so that the shoulder measurement is as long as possible while still fitting in the chamber nicely, without too much struggle?

Thoughts?

Edit: just removed the ejector spring and pin, found that I can chamber a case as long as 2.1215 without issue. Might be able to go even a bit longer but I'm out of fired brass to test.


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[MidGAHunter]

If the twice fired is 2.1190 base to shoulder, then I would set my sizing die to bump the shoulder to 2.116-2.117 range. You don't want difficulty chambering a hunting rifle. The other option is to prep your twice fired brass and shoot it....then see what its shoulder measurement is. By 2-3 firings the brass should have formed to your chamber pretty well.

 

[16Bore]

Adjust the dies to the rifle, not the ruler, then read the ruler for reference.

 

[KineKilla]

The new, unfired brass measures at 2.101.
My fired brass measures 2.118.
My dies cause the brass to grow to 2.124 +/- before bumping it back to 2.120 (where it is now currsnrly set)

So, from 2.101 to the max measured length of 2.124 is .023 worth of case stretch.

It almost feels like I'm using up all the life a piece of brass has to offer in just one firing/sizing process.

Even if I were to go from 2.1185 (fired length) to 2.116 as suggested, the brass would have already been stretched to 2.124 or so during the sizing process.

Other than neck sizing only, is there any way to NOT stretch the case prior to bumping the shoulder back? I'm thinking I'll need to buy a neck sizing die.

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[16Bore]

New brass is always undersized. The initial stretch isn’t bad, resizing to factory is. You’re on the right track taking the ejector out. Back your die out and size, then try to chamber and keep going until you feel the resistance closing the bolt. Now you know exactly the distance from the boltface to the shoulder. Then however further you feel you to be off the shoulder.

Belts are notoriously undersized new and over-resized after, leading to case head separation like you’ve got there.

That way always worked for me. You really want to see some “stretch” monkey around with AI something.

 

[wind gypsy]

The new, unfired brass measures at 2.101.
My fired brass measures 2.118.
My dies cause the brass to grow to 2.124 +/- before bumping it back to 2.120 (where it is now currsnrly set)

So, from 2.101 to the max measured length of 2.124 is .023 worth of case stretch.

It almost feels like I'm using up all the life a piece of brass has to offer in just one firing/sizing process.

Even if I were to go from 2.1185 (fired length) to 2.116 as suggested, the brass would have already been stretched to 2.124 or so during the sizing process.

Other than neck sizing only, is there any way to NOT stretch the case prior to bumping the shoulder back? I'm thinking I'll need to buy a neck sizing die.

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As you're observing, it is common for the case stretch (shoulder moving forward) to not fully fill your chamber on the first firing. If you know there is another 0.006" the shoulders can move forward, I wouldn't bump shoulders back to 0.008" (2.116" in your case).

I would set your dies such that they are sizing the neck but don't allow for the sizing of the body that is happening at the same time to push the shoulder further forward than 2.123 or 2.122". This is admittedly not something I have a ton of experience with but that is what makes sense to me.

 

[KineKilla]

Thanks for the continued input....

What I think I'd like to do is get a neck sizing die, shoot brass until it stops growing then determine what my final desired dimension will be.

The stretch then shrink action my FL dies cause worries me. Seems that even if it is set as far out as possible while still resizing the neck, I will have stretched the case from the bottom.

Won't know for sure until I do some more shooting because as of now all my brass is either new or has already been reloaded.

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[Ram94]

Take a look at a Lee collet die / Redding body die combo. Less induced runout than most all other sizing options. Use the body die once your brass has grown to chamber length.


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[KineKilla]

I also noticed yesterday that some of the once fired brass (2.1185) had a line appearing above the belt already. Right where cases tend to split or separate. It isn't a mark left by the resizing dies and you can definitely feel it with a fingernail.

I wonder if I have a combination of over-sizing, generous chamber specs and a bad batch of brass that is thinner in this area all working together to stress me out? I've had this rifle for years and have always reloaded for it using the same processes but it is just recently I am having this issue so maybe this brass is just thin enough to highlight the other flaws in my system.

FWIW...I picked up a Redding neck sizing die yesterday from guy that was selling a number of different dies. Figured since I was getting dies for 9mm and a 300WM neck sizer from him I may as well give him another $10 and get the 7MM neck sizer as well. Last night I disassembled all the dies and thoroughly cleaned them in my sonic cleaner, have not used them yet.

 

[Mainmechanic]

Good advice above. The one pic of the casehead appears to show moderate primer flattening I believe. False shoulder method works the best for myself for all new belted magnum brass also

 

[Harvey_NW]

I've had this exact same learning experience with a 7mm mag, I started out using the Hornady and RCBS die setup videos and reloading tutorials and got case head separation on new Winchester brass 3rd firing. After doing research and learning about the magic .002 measurement with a bump gauge, it alleviated the issue completely.

Personal opinion about Norma, when I originally took the plunge down the rabbit hole into the long range and reloading game my buddy had me buy 100 pieces and worked up a load for me. I think I put 6 firings through it smashing it back down to the "camover action on the press handle" before I bought a new bag of brass to attempt working up my own load. Point being Norma is the shit and I believe it to be WAY more resilient than cheaper brass, and (as stated above) I'm hoping to score some of that ADG to try, because Norma is wiped off the shelves A LOT.

I love informative threads like these. Sounds like you're on the right track to getting the most out of your brass!