Pressure signs 7-08

SporterII

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I have a 9.25 twist 25" 700 in 7-08. The chamber measures a 162 AMAX at zero jump @ 2.934 oal.
Published loads with Varget [40.0], H4350 [44.0], H414 [45.0 AND ACCURATE]. These all leave cratered primers. None loose in Winchester brass.
Shiny just in front of the grove all. Some visably with a raised ring at the shiny band. Especially with 2.88 or more OAL.
The Hornady book shows 2.755 OAL W/ this bullet.
It seems like plenty jump and mabie too much for an accurate load with any significant speed. At least the 414 gets in there nicely.
I will chrono some 414 loads at 2.75" to 2.8". I sure hope this thing is going to run.
How much shiny can it stand?"
 

SporterII

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I just checked and found my new Winchester brass measures .010shorter to the shoulder than my brass fired in my new custom cut chamber. This with the Hornady tools in a Central caliper.
 

SporterII

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Same smith cut my 223 and it measures .002. Shoots too.
Guess I found my own answer. I am learning. The hard way but non the less.
600.00 machine work, 100 pcs. vaporware 7-08 brass and a box of Amax 162's.
 

Fuzzball

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"Shiny just in front of the grove all....How much shiny can it stand?"

I don't know what "grove all" or "shiny" is but the pressure signs for a 7-08 are exactly the same things as for a .223 or .375.

Cratered primers are most often due to a poorly fitted firing pin and bolt face.

New brass is always shorter to the shoulder than after it has been fired and stretched to fit the chamber.
 
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SporterII

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Fuzzball, You offered good advice wile I was starting out.
The shiny band is a polished surface. brass is polished .120 band - ring- front side of the extractor groove. some have a sharp raised ring anroun this ring. some show a slight rise. I may need to get a digital camera. It will show up.
 

Fuzzball

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"Fuzzball, You offered good advice wile I was starting out."

Still trying. :)
 

SporterII

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The shiny bands are .007" bigger dia. On some of these. Leading edge of the 'shiny' band being the raised - deformed spot.
 

SporterII

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I bought some Norma brass. Same case dia. near the base. [.4655 - norma, .464 - win].
Case to shoulder using .4" bushing nORMA > WIN. BY .002.
Win. case 2.027 oal, 2.034 fired.
Win. case fired .0035 longer to the bushing, and, way fatter near the base. .471. From .464 to .471
Looks like a diameter discrepency near the case head.
Is this brass still usable? Should I trim and size .0015 and see if this holds for a few firings?
I am going to try the Norma and compare results.
 

former naval person

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You have stretched the Win brass. Just bump the shoulder back .002 or so and shoot it. If you take it back to original too short dimensions it will separate sooner. You can avoid it in the new brass by expanding the neck to .308 and sizing it back to 7mm but at the proper bump length for your chamber. That creates a "false shoulder" that will hold the case against the firing pin blow and allow it to size to the chamber without stretching. JMHO
 

SporterII

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What I see more than .0035" stretch is the diameter 1/4" from the base. It fires to +.005 showing a raised diameter from .464 to .471.
Case starts out .464 in diameter. Chamber is greater than .471 causing brass to form a new diameter of .471. Visable and vaguely like a ring. Expanded just above the case head.
My best description.
This is what I question.
 

former naval person

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That is what I am addressing. The shiny ring is a stretch mark. Both length and width. If you'll use a Lee Collet Neck sizer until you have to bump, you'll not expand the case farther. Furthermore, if you send your present full length die along with 3 fired cases to the manufacturer of the die, they can fit a sizing die that won't overwork the brass.(At least RCBS will) You have a large diameter chamber. Live with it by fitting the brass and die to it, or have the chamber cut back and re-chambered to a tighter specification.
 

SporterII

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My RCBS fl die, adjusted, neck sizes and leaves the rest alone or I can cut a thou out of the headspace. They do seem to work this way in my seven and my 223's both.
I appreciate your input as to not needing an ambulance for my once fired brass in this gun. It is helpful as I am not experianced enough not to ask. I must admit it is not a perfect situation as my 223's need not apply to this. They shoot and brass keeps looking good.
As to large diameter, books all agree that the dimension in question is .470 and this is where it all begins for me.
 

SporterII

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O.K. I have a handle on this now. I made a paperclip tool. Went in and can find a definate thin spot. Right where the shiny band is. How about that. I have read and re read and it pays off. The brass is junk,I was wishing it still good. It aint and thats a fact. Measuring over and over was good excercize.
I have learned to find it and why its there.
My 7-08 will need a barrel with a better chamber. No disaster. fckin around would have been worse.
The cost at this point was worth it.
I know. I have confidance and power now. I will get to shoot 7-08 my way. Soon enough.
I have a 223 with a 'perfect' chamber and one with a pretty good one. I have the brass thing figured out pretty good now at the newbie level [need a smily face with a missing tooth].