300 WM brass destroyed.

r3volut1oner · Jan 26, 2025

Hornady brass, 5 cycle with 79.4 grain StaBALL HD with 208 ELDM with speed 2940 fps.
Rem 700 LR SS 26" 1 - 10.
Around .030" from lands ( I think so )

Brass deformed and crack formed near the belt.
No visible signs of pressure on primer. Should look on photo to understand what happens.

The difference in 5 cycle I switched to S&B magnum primer, before for 4 cycles used Ginex.

My question is what do you think went wrong? Or 5 cycle is the lifetime of the Hornady brass?

What you would suggest to not get it again?

918v · Monday at 2:57 PM

How much are you bumping the shoulder?

r3volut1oner · Monday at 3:07 PM

918v said:
How much are you bumping the shoulder?

I pumped around .003" and .004".

Measured with comparator .420" diameter:
Before bump around 2.2725" after 2.268-2.270"

I purchased this brass from someone who fired this one's and in this 1st cycle the measurements where around 2.275".

Beefmanne · Monday at 3:36 PM

Over pressure.

Rangemaster · Monday at 3:57 PM

You have a carbon ring, get a bore scope and look at where the lands start right around the bullet. I had this on my creedmoor, and it took bore paste and some heavy scrubbing in that area.

ggmanning · Monday at 4:00 PM

How much are you sizing the shoulder set back, are you using the Willett collet die for above the belt? Hornady brass sucks.

918v · Monday at 4:05 PM

ggmanning said:
How much are you sizing the shoulder set back, are you using the Willett collet die for above the belt? Hornady brass sucks.

I got 15 reloads using Hornady brass running 208s at his velocity with H1000. I bumped the shoulders .002” tho.

ggmanning · Monday at 4:16 PM

That is very good with Hornady brass. I'd have no complaints there but it has not been my experience with it. I've had poor comparison results with Hornady vs most others for longevity.

Halfnutz · Monday at 4:19 PM

That first pic makes me wonder if you had lube or something in the chamber. Does any other brass look like that?

I've seen creases like that from too much lube in a sizing die but never from in a chamber.

918v · Monday at 4:26 PM

Halfnutz said:
That first pic makes me wonder if you had lube or something in the chamber. Does any other brass look like that?

I've seen creases like that from too much lube in a sizing die but never from in a chamber.

Could be from the gas escaping out the crack

XLR308 · Monday at 4:34 PM

918v said:
How much are you bumping the shoulder?

^^ This would be my first question as well.

r3volut1oner · Monday at 6:03 PM

Halfnutz said:
That first pic makes me wonder if you had lube or something in the chamber. Does any other brass look like that?

Other brass just have cracks in the bottom.

r3volut1oner · Monday at 6:21 PM

ggmanning said:
How much are you sizing the shoulder set back, are you using the Willett collet die for above the belt? Hornady brass sucks.

I am using Redding bushing full sizing die + mandrel.
Shoulder set back 3-4 thousands, probably too much.

supercorndogs · Tuesday at 5:42 AM

Three possibilities.

Your brass started out way too short.

Your chamber is way too long.

You're bumping your shoulder back too far. (It's almost always this one.)

CHS in 3-4 firings requires a lot of shoulder movement.

Rocketmandb · Tuesday at 10:31 AM

Rangemaster said:
You have a carbon ring, get a bore scope and look at where the lands start right around the bullet. I had this on my creedmoor, and it took bore paste and some heavy scrubbing in that area.

I recently devised a way to get rid of carbon rings with no abrasives and no scrubbing using commonly available solvents. Will be putting out a video on this at some point.

Doom · Tuesday at 10:35 AM

Since you don't know what the measurements were on first firing you don't know how much stretch the case went through on initial firing.

ggmanning · Tuesday at 7:51 PM

I found bumping the shoulder .001 to .002 and using the Larry Willet collet die for the belt area made my 300WM brass last much longer.

XLR308 · Tuesday at 8:27 PM

ggmanning said:
I found bumping the shoulder .001 to .002 and using the Larry Willet collet die for the belt area made my 300WM brass last much longer.

I used primarily a Lee 300wm die set and never had any issues and match grade accuracy but I didn't run Nuclear loads either and pretty much only used Nosler custom brass.
My 200 grain nosler accubond load with H1000 was not crazy but certainly not watered down considering the bearing surface of that bullet in a factory barrel 24" long running 2860fps average and routinely shot 1/2 moa or better.
Chasing velocity is a fools errand in most cases and yealds minimal returns but oversized brass especially in a belted case is a crash course in reloading.

ggmanning · Tuesday at 8:34 PM

I don't chase speed. I chase the most stable node with small ES and accuracy. Most times it's fairly well below max. Sometimes it's on the edge. If it is that's what I shoot. I still find relative max on any work up because all barrels are different. Brass prep techniques I recomnended make cases last longer with pedestrian loads and pushing it as well. I didnt even mention my practice in the context of chasing speed or nuclear loads.

918v · Tuesday at 8:54 PM

r3volut1oner said:
I pumped around .003" and .004".

Measured with comparator .420" diameter:
Before bump around 2.2725" after 2.268-2.270"

I purchased this brass from someone who fired this one's and in this 1st cycle the measurements where around 2.275".

How do you know this was once fired brass?

918v · Tuesday at 8:56 PM

r3volut1oner said:
I am using Redding bushing full sizing die + mandrel.
Shoulder set back 3-4 thousands, probably too much.

3-4 thou is fine

XLR308 · Tuesday at 9:29 PM

ggmanning said:
I don't chase speed. I chase the most stable node with small ES and accuracy. Most times it's fairly well below max. Sometimes it's on the edge. If it is that's what I shoot. I still find relative max on any work up because all barrels are different. Brass prep techniques I recomnended make cases last longer with pedestrian loads and pushing it as well. I didnt even mention my practice in the context of chasing speed or nuclear loads.

Sorry dude wasn't trying to single you out but many can't seem correlate the difference between belted rifle cases and actuall headspace measurements beyond the belt.
To much crap info circulating that contradicts the actual fact and what most use.
The belted cases can deliver beyond match accuracy regardless of mainstream group think and it's a shame.
I will be be quiet now and let others fill in the blanks.

r3volut1oner · Wednesday at 7:07 PM

supercorndogs said:
Three possibilities.

Your brass started out way too short.

Your chamber is way too long.

You're bumping your shoulder back too far. (It's almost always this one.)

CHS in 3-4 firings requires a lot of shoulder movement.

My chamber is long, I measured jam 3.640" it's long for 300 WM, no?
But what exactly it means, how it's can affect the brass.

I also seat bullet 3.6" that can be the reason for high pressure?

CHS what does it stand for?

r3volut1oner · Wednesday at 7:08 PM

ggmanning said:
I found bumping the shoulder .001 to .002 and using the Larry Willet collet die for the belt area made my 300WM brass last much longer.

Where do I get this die?

ggmanning · Wednesday at 7:10 PM

https://www.larrywillis.com/ read the reloading questions tab. Explains some good info on the die and belted magnum case prep.

r3volut1oner · Wednesday at 7:17 PM

918v said:
How do you know this was once fired brass?

Not sure, but for my friend it's working for about 10 cycles already.

ggmanning · Wednesday at 7:22 PM

r3volut1oner said:
My chamber is long, I measured jam 3.640" it's long for 300 WM, no?
But what exactly it means, how it's can affect the brass.

I also seat bullet 3.6" that can be the reason for high pressure?

CHS what does it stand for?

I ordered a "match" chamber on purpose because I wanted more freebore to allow loading of long secant ogive/VLD style bullets out further. Eliminates having to seat these long bullets deeper in the case and eating up powder capacity. I measured the longest I could seat Berger 215's with just the boat tail below the bottom of the neck and had the chamber cut with that length freebore to the lands. That is not the same as a chamber too long though, it's just longer freebore. If the chamber is cut to spec the less bump of the shoulder in sizing the better. Less movement on firing/resizing cycles means longer brass life especially with bigger bore/magnums. I never go over .001-.002" that I recommended above. I want just enough resizing to chamber well and no more. You may (and likely do) have a chamber cut to spec with just more freebore. All a guess from the keyboard though.

r3volut1oner · Wednesday at 7:23 PM

XLR308 said:
Chasing velocity is a fools errand in most cases and yealds minimal returns but oversized brass especially in a belted case is a crash course in reloading.

This is probably the case here, I want to get max velocity. I see no pressure signs on the bottom of the brass, but probably over pressure is definitely there.

But what do you think about the COAL of 3.6" for 300 wm. Is it okay if it's .040" far from the lands?

918v · Wednesday at 7:32 PM

All my 300wm chamber are long. The shoulder length grows .020” on the first firing. It’s not a problem that would cause case head separation after 5 reloads.

XLR308 · Wednesday at 7:36 PM

r3volut1oner said:
This is probably the case here, I want to get max velocity. I see no pressure signs on the bottom of the brass, but probably over pressure is definitely there.

But what do you think about the COAL of 3.6" for 300 wm. Is it okay if it's .040" far from the lands?

There is nothing wrong with being .040" off or even more than that.
I had a remington 700 once that had such a long throat that a 168 matchking would damn near fall out of the case touching the lands but it shot great.

ggmanning · Wednesday at 7:47 PM

r3volut1oner said:
This is probably the case here, I want to get max velocity. I see no pressure signs on the bottom of the brass, but probably over pressure is definitely there.

But what do you think about the COAL of 3.6" for 300 wm. Is it okay if it's .040" far from the lands?

Sure. I have some VLD loads in other stuff that prefer jumping .040 to .120" off.

260shooter · Wednesday at 7:50 PM

r3volut1oner said:
I am using Redding bushing full sizing die + mandrel.
Shoulder set back 3-4 thousands, probably too much.

yes. To much.

r3volut1oner · Wednesday at 8:13 PM

ggmanning said:
I ordered a "match" chamber on purpose because I wanted more freebore to allow loading of long secant ogive/VLD style bullets out further. Eliminates having to seat these long bullets deeper in the case and eating up powder capacity. I measured the longest I could seat Berger 215's with just the boat tail below the bottom of the neck and had the chamber cut with that length freebore to the lands. That is not the same as a chamber too long though, it's just longer freebore. If the chamber is cut to spec the less bump of the shoulder in sizing the better. Less movement on firing/resizing cycles means longer brass life especially with bigger bore/magnums. I never go over .001-.002" that I recommended above. I want just enough resizing to chamber well and no more. You may (and likely do) have a chamber cut to spec with just more freebore. All a guess from the keyboard though.

Yeah, I actually wanted to get .001-.002 shoulder pump, just measured it sloppy and did proper measurements after the incident.
Making sure I am not pumping too much I believe gonna help. Wasn't aware of this problems belted brass have.
I think my chamber cut to specs, but having this freebore I think your right.

r3volut1oner · Wednesday at 8:18 PM

918v said:
All my 300wm chamber are long. The shoulder length grows .020” on the first firing. It’s not a problem that would cause case head separation after 5 reloads.

I have another 40 one time fired hornady cases that I gonna try.
I gonna measure shoulder pump much better.
Also gonna remove 0.6 gn. from the charge.
We gonna see how it's gonna help.

ggmanning · Wednesday at 8:32 PM

r3volut1oner said:
I have another 40 one time fired hornady cases that I gonna try.
I gonna measure shoulder pump much better.
Also gonna remove 0.6 gn. from the charge.
We gonna see how it's gonna help.

Good luck. The two most common culprits in my experience are too much horsepower and too much shoulder bump or both. Belted cases are not a detriment but in my sequence takes another step with the collet and paying attention to shoulder bump. Non belted magnums like the PRC have issues to overcome as well. PRC click and sticky bolt after some firings takes a work around also.

supercorndogs · Wednesday at 8:54 PM

.

r3volut1oner said:
This is probably the case here, I want to get max velocity. I see no pressure signs on the bottom of the brass, but probably over pressure is definitely there.

But what do you think about the COAL of 3.6" for 300 wm. Is it okay if it's .040" far from the lands?

Your jam length is not going to tell you your chamber length. You need to measure your shoulder length.

I seriously doubt pressure has anything to do with this.

An over pressure round would have brass extrusion into the ejector and case head expansion. That also happens at the .200 line. Not higher up the case.

secondofangle2 · Thursday at 9:55 AM

r3volut1oner said:
Other brass just have cracks in the bottom.

This is not “cracks in the bottom” this is “impending case head separation” and the problem is over-resizing till proved otherwise

I’d trash the whole batch of brass, get new brass, measure new and then after 2 firings, from the datum line

Could also measure chamber with go-no-go gauges

supercorndogs · Thursday at 12:27 PM

Can't measure shoulder with go no go in belted mags.

Incipient case head seperation.

r3volut1oner · Thursday at 2:00 PM

supercorndogs said:
Incipient case head seperation.

Found some images of it on internet, that's for sure what happened.
Now looking into depulled cases I see this "cracks" inside.

And now I know that have to check cases from inside to prevent case head separation.

Case looks like this photo from internet.

XP1K · Thursday at 2:34 PM

ggmanning said:
Good luck. The two most common culprits in my experience are too much horsepower and too much shoulder bump or both. Belted cases are not a detriment but in my sequence takes another step with the collet and paying attention to shoulder bump. Non belted magnums like the PRC have issues to overcome as well. PRC click and sticky bolt after some firings takes a work around also.

Cortina makes a mandrel die that sizes the base also. I emailed them as a 300winmag die wasn't listed, and they said one is in the works by popular demand. I'll probably pick one up when they're available. I've heard about the collet die, but if I can hit the base and mandrel in one step, all the better.

spife7980 · Thursday at 4:26 PM

r3volut1oner said:
Found some images of it on internet, that's for sure what happened.
Now looking into depulled cases I see this "cracks" inside.

And now I know that have to check cases from inside to prevent case head separation.

Case looks like this photo from internet.

No, limiting shoulder set back in sizing is how you “limit” it. The stretched brass ditch inside is how you identify its progression

supercorndogs · Thursday at 4:38 PM

XP1K said:
Cortina makes a mandrel die that sizes the base also. I emailed them as a 300winmag die wasn't listed, and they said one is in the works by popular demand. I'll probably pick one up when they're available. I've heard about the collet die, but if I can hit the base and mandrel in one step, all the better.

I don't ger it. If someone needs to buy new dies, why not just move to 300prc?

Earnhardt · Thursday at 4:47 PM

Guys, click on the OPs name.
That shows you where he’s located at…

XP1K · Thursday at 4:55 PM

supercorndogs said:
I don't ger it. If someone needs to buy new dies, why not just move to 300prc?

I'm already pretty heavily invested in the winmag. One $65 die isn't a deal breaker at this point. I will concede though, if someone is fresh getting into a magnum 30, the prc is probably the way to go.

ggmanning · Thursday at 5:47 PM

supercorndogs said:
I don't ger it. If someone needs to buy new dies, why not just move to 300prc?

Already had the special sauce before 300 PRC was introduced. Got it figured out so no need to switch to the PRC and its' inherent problems. Starting new maybe the right choice though. As I said earlier the PRC is not without issues. Guys having to DIY hone chambers or get chambers cut with a particular reamer to prevent PRC clicking. Ballistically they are twins. Neither without work arounds for issues inherent to the case design. I would have also most likely bought the Cortina die vs Larry Willis collet, FL bushing, and mandrel dies had it been available when I started the 300WM journey years ago. It looks to be a all in one for what I have found works for brass life and concentricty/neck tension with what was available at the time.

XLR308 · Thursday at 5:54 PM

ggmanning said:
Already had the special sauce before 300 PRC was introduced. Got it figured out so no need to switch to the PRC and its' inherent problems. Starting new maybe the right choice though. As I said earlier the PRC is not without issues. Guys having to DIY hone chambers or get chambers cut with a particular reamer to prevent PRC clicking. Ballistically they are twins. Neither without work arounds for issues inherent to the case design. I would have also most likely bought the Cortina die vs Larry Willis collet, FL bushing, and mandrel dies had it been available when I started the 300WM journey years ago. It looks to be a all in one for what I have found works for brass life and concentricty/neck tension with what was available at the time.

I think there is a reason KMW is primarily still using the 300wm in many of his rifles.
The accuracy and performance speak for its self and the old adage if it isn't broke don't fuck with it.

supercorndogs · Thursday at 5:58 PM

There is no special sauce, what we had was a case with stupid belt on for no good reason. That works pretty good if you headspace off the shoulder and find a way to deal with the secondary belt. And often time deal with the initial brass stretch which often goes I to the .02s unless you get Peterson long brass of fireform.

Those are not case design problems of the PRC. Those were manufacturing problems we often see when a new case comes out and all the brass makers and reamer makers and die makers have to get traltively on the same page.

I.E traders to small brass too big dies too small.

I don't see any reason to choose or stick with the 300wm unless you have a bunch brass or already bought dies to deal with belt buldging. Or have ammo.

supercorndogs · Thursday at 5:59 PM

XLR308 said:
I think there is a reason KMW is primarily still using the 300wm in many of his rifles.
The accuracy and performance speak for its self and the old adage if it isn't broke don't fuck with it.

Was the 300h&h broke? Did the 300wm fix it?

ggmanning · Thursday at 6:02 PM

supercorndogs said:
I don't see any reason to choose or stick with the 300wm unless you have a bunch brass or already bought dies to deal with belt buldging.

Pretty much exactly what I said and the special sauce is the die to deal with belt bulging. Or just say screw it and go to the next level with 300 Norma. If I was choosing now that would be the case 300 PRC or bump up to 300 Norma but I already am invested in the 300WM with the results I need so no reason to change.

XLR308 · Thursday at 6:04 PM

supercorndogs said:
Was the 300h&h broke? Did the 300wm fix it?

Not really just minor improvements to the case design to modernize it by reducing body taper and case growth though the performance was pretty damn close.
I guess one could argue the same between the 300wm and the 300PRC.

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