Pressure Signs ?

[OLEJOE]

The ejector marks only show up on this one particular lot of brass. I have some Winchester 7mmRM brass I loaded and there are no marks on it but it’s only been loaded and fired 1 time. The brass I formed started out fitting the chamber a Lot better and is probably thicker than the brass that has ballooned out. The marks are on the ones I loaded at 62 grns which is well below max. Thanks

 

[bcarico]

You said you made 7mm brass from 300wm brass correct? Could you be having a neck clearance issue in the chamber? The necks on the 300wm brass will be thicker necked down to 7mm than normal 7mm brass.

 

[Bart B.]

Is it possible to get ejector marks on the head of the brass without having excess pressure ?

I don't think so.

Typical cartridge brass starts flowing into bolt face cutouts at about 80 to 85 thousand psi. I've shot dozens of 7.62 NATO proof loads at that pressure and no fired cases had ejector hole bumps on their heads. Therefore, I believe ejector hole mark's on case heads results from pressure well over safe levels.

Yes. It can be seen on factory ammo running in the 61,000 + PSI range.

With proper piezo transducer psi measurements verifying that pressure in SAAMI spec barrels?

I disagree. Especially when dozens of factory ammo pressure is about 65,000 psi. Check SAAMI cartridges pressure specs.

Typical for a belted magnum. They set the shoulders back a mile on them. 7mm rem mag is famous for this exact thing on factory brass

First time I've heard such claim. Is their brass much softer than others across all case manufacturing companies?

Also, a belted mag ‘balloons’ to fill the chamber at the shoulder/case, it does not stretch from the web forward on the first firing.

My new belted mag cases headspacing on their shoulders stretch from belt to shoulders on first firing. New belted cases headspacing on their belts also stretch from belt to shoulder on first firing.

Both evidenced by their fired cases in each instances have a ridge a few thousandths forward of the belt where the case body expanded at the barrel chamber wall edge back from the headspace shoulder. No part of the barrel touched the case body in that place at peak pressure with the case head hard against the bolt face.

 

[OLEJOE]

I turned the necks of the brass because part of the shoulder of the 300 brass gets swaged in to the neck. I’ve got 6 thou clearance on the fired necks. I also kissed the shoulder with the cutter.

 

[243winxb]

I disagree. Especially when dozens of factory ammo pressure is about 65,000 psi. Check SAAMI cartridges pressure specs.

From Olin

modulus of elasticity- Cartridge Brass-
Material is 70 copper/30 zinc with trace amounts of lead & iron , called C26000. Material starts to yield at 15,000 PSI when soft (annealed), and 63,000 PSI when hard.
Material yields, but continues to get stronger up to 47,000 PSI when soft, and 76,000 PSI
when work hardened. Modulus of Elasticity is 16,000,000 PSI. This means to pull a 1.000 inch long strip to 1.001 inch long induces a 16,000 PSI stress.
So if you pull a 1.000 inch strip to 1.005 inch long, you get about 76,000 PSI, which is the max obtainable.

When i reload, i dont want to see/have extractor mark, primer flow, hard bolt lift or loose primer pockets with 5 or less firings.

I have seen the faint ejector mark on some factory ammo. Not all cartridges.

 

[Bart B.]

View attachment 1085700
From Olin

When i reload, i dont want to see/have extractor mark, primer flow, hard bolt lift or loose primer pockets with 5 or less firings.

I have seen the faint ejector mark on some factory ammo. Not all cartridges.

Cartridge brass is work hardened several times when made. Once for each stamped coin's cup and draw (3 or 4 each case, head bunt, rim and neck process. Then the neck is annealed. Case head areas are much, much harder than case necks.

 

[Dusty Stevens]

Cartridge brass is work hardened several times when made. Once for each stamped coin's cup and draw (3 or 4 each case, head bunt, rim and neck process. Then the neck is annealed. Case head areas are much, much harder than case necks.

And theyre annealed several times as cups

 

[243winxb]

Bart,

The brass is annealed a few times also. When some 5.56 was being made, they tried skipping 1 anneal. This caused a problem near the case head area, separations or cracks. I forget what one.

When the extra anneal was done on the neck shoulder area, heat went down to the case head area. This stress relieved the brass. Stress is removed at a lower temperature than annealing. Around 400 f degrees , if i remember correctly.

Do a search here. https://discover.dtic.mil I am not going to look it up again .

Ok, so i search it again. Annealing info- https://apps.dtic.mil/dtic/tr/fulltext/u2/a030722.pdf

See Conclusion page 43.

 

[Bart B.]

And theyre annealed several times as cups

Yup, they are. In finished cases, necks are softer than heads

But 65,000 psi average doesn't push case head brass into bolt head cutouts with commercial brass in minimum spec chamber and bore. Nor does max allowable psi a few thousand higher.

If my new cases did, I would talk with their maker. Anybody done that?

 

[Bart B.]

Yes. It can be seen on factory ammo running in the 61,000 + PSI range.

What are the rifle and ammo details that led you to this conclusion?

Many modern cartridge peak pressures are higher, 308 Win at 62,000 psi, and they don't produce such case head bumps.

 

[Zero333]

Here is a Quickload print for reference. Using 150 Accubond LR and H-4831sc
=========================================================

Cartridge : 7 mm Rem. Mag.(SAAMI)
Bullet : .284, 150, Nosler Accubond LR 58734
Useable Case Capaci: 73.267 grain H2O = 4.757 cm³
Cartridge O.A.L. L6: 3.290 inch = 83.57 mm
Barrel Length : 24.0 inch = 609.6 mm
Powder : Hodgdon H4831 SC

Predicted data by increasing and decreasing the given charge,
incremented in steps of 2.0% of nominal charge.
CAUTION: Figures exceed maximum and minimum recommended loads !

Step Fill. Charge Vel. Energy Pmax Pmuz Prop.Burnt B_Time
% % Grains fps ft.lbs psi psi % ms

-20.0 79 53.60 2431 1969 31397 9858 88.0 1.561
-18.0 80 54.94 2493 2070 33519 10192 89.3 1.519
-16.0 82 56.28 2554 2173 35790 10518 90.6 1.479
-14.0 84 57.62 2616 2280 38216 10835 91.8 1.436
-12.0 86 58.96 2678 2390 40811 11142 93.0 1.391
-10.0 88 60.30 2741 2502 43587 11437 94.0 1.349
-08.0 90 61.64 2803 2617 46556 11719 95.0 1.308
-06.0 92 62.98 2866 2735 49739 11986 95.9 1.268
-04.0 94 64.32 2928 2856 53118 12238 96.8 1.230 ! Near Maximum !
-02.0 96 65.66 2991 2979 56725 12474 97.5 1.193 ! Near Maximum !
+00.0 98 67.00 3053 3105 60588 12690 98.1 1.157 ! Near Maximum !
+02.0 100 68.34 3115 3233 64731 12888 98.7 1.123 !DANGEROUS LOAD-DO NOT USE!
+04.0 102 69.68 3178 3363 69176 13065 99.1 1.090 !DANGEROUS LOAD-DO NOT USE!
=====================================

Hodgdon's data shows 68 gr MAX with 150 TTSX,. but on the other hand they show 62 gr MAX with 150 Partition

 

[MagnumManiac]

Bart, the expansion line you describe has not stretched forward, it has only stretched outward to contact the chamber wall.
I fireform 300 Weatherby/340 Weatherby/375 H&H into 375 Weatherby, if I do not use enough powder, the case only expands about halfway up the case and the cases have SHRUNK in length, your theory cannot be correct if the cases reduce in length, the other telling factor is that the necks shorten in length on the first firing, this confirms that the brass is being ballooned and pulled from the neck/shoulder into the body as it expands, not from the web.

Cheers.

 

[Bart B.]

Bart, the expansion line you describe has not stretched forward, it has only stretched outward to contact the chamber wall.

Yes. It didn't get there until peak pressure pressed the case head a few thousandths back against the bolt face

The case belt was hard against the chamber headspace shoulder, head a few thousandths off the bolt face and the case shoulder was a few thousandths back from the chamber shoulder, when the round fired.

When pressure was high enough, the case shoulder and head were pressed against their chamber limits. The case belt moved back as far as its head did and the case body next to the belt expanded to the chamber limit.

Most all cases are shorter in length after firing

 

[OLEJOE]

SAAMI chamber spec states.220 + .007 case head to forward edge of the belt. That’s why some people have to use the collet die to resize just above the belt. Most brass runs .215 to .217. With the shoulder being pushed forward and a tight die brass may not go far enough in to the die to resize that area when trying to head space on the shoulder. I’ve reduced the load and increased the jump to the lands another .010 and ordering some different brass. I still don’t understand why the primers still have all of the radius left on the edges if the pressure was that high. Do magnums not flatten primers ?

 

[Dusty Stevens]

SAAMI chamber spec states.220 + .007 case head to forward edge of the belt. That’s why some people have to use the collet die to resize just above the belt. Most brass runs .215 to .217. With the shoulder being pushed forward and a tight die brass may not go far enough in to the die to resize that area when trying to head space on the shoulder. I’ve reduced the load and increased the jump to the lands another .010 and ordering some different brass. I still don’t understand why the primers still have all of the radius left on the edges if the pressure was that high. Do magnums not flatten primers ?

Your magnum primers show excess pressure to most here- not sure what youre used to. They pair up exactly with the faint ejector marks

 

[243winxb]

.5136" + .002" is chamber diameter in front of the belt.

 

[Bart B.]

I still don’t understand why the primers still have all of the radius left on the edges if the pressure was that high. Do magnums not flatten primers ?

Not in my experience using the same primer lot in normal max loads in both 308 Win and 30 caliber magnum cases. Both had identical primer edge radius sizes. Ditto with new factory ammo with same primer type in each.

Very normal when many standard and magnum named cartridges have virtually identical pressure specs

 

[Bart B.]

Your magnum primers show excess pressure to most here- not sure what youre used to. They pair up exactly with the faint ejector marks

The primers pictured in post #5 look normal to me; lots of space from their flat edge to pocket shoulder.

 

[243winxb]

head space on the shoulder.

Leaves the brass unsupported in front of tne belt.

The firing pin strike would have to move the case forward in the chamber, pushing the shoulder back on firing to avoid the bulge in front of the belt.

Belt chamber maximum headspace .227"
Cartridge minimum .212"
Slop is .015" maximum.

 

[OLEJOE]

Thanks for all the help. I was definitely over max on the charge weight. The ejector marks are on all of the brass from 62 grns up. They are on the Winchester and not on some reloaded Remington brass. I may have multiple issues. Thanks again