Brass still good to go ?

[Jimm]

I have been checking the extractor groove on a batch of Lapua brass as I marched it through several ladder tests with the tops of the ladders ( last 4 or 5 rounds ) being pretty stout .

After 4 firings I took the dial caliper to all the cases in this 50 lot and checked the primer pockets and ext. groove dimensions . 24 out of the 50 had expanded 5 thou in the groove and primer pockets are 2 thou under primer size . The other 26 are 2 to 3 thou larger in the groove than new and 3 to 4 thou smaller in the primer pockets than the primer .

I also checked the internal neck size after collet neck sizing with the Lee collet die . The necks are staying same as when first sized , that is , 4 thou under bullet size . This is true for all 50 cases .

Finally I sliced a case that was the most enlarged in the groove and primer pocket dimensions . Not having viewed cases before in this manner I would appreciate input on the pix I am hoping to attach to this post .

Bottom line is that I have been operating under a idea that when the groove dimensions are beyond 3 thou enlargement that the brass was likely to have case wall thinning to the point of separation . I don't know where or when I picked up this idea but I really don't want to throw away good brass .

Thanks as always guys , Jim B. [image]

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Pic is pitimous cause my camera buff middle son isn't here to show me how to get the closeups in focus , this camera has more knobs sticking out of it than a sow that just had a litter . [image]

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[robbor]

The pics, Usually it is macro mode. For a digital there sould be a button showing the pic of a flower.

 

[gonehuntingagain]

For those close detail shots, it also might help if you use a tripod. I know it sure helps me!

 

[Buffalobob]

Pretty good work with the saw.

Did you uniform the flash holes or did it come that way? I am about to convince myself that the Lapua flashholes are uniform enough without me screwing them up.

 

[abinok]

Measureing of the extractor groove is meant to be an indicator of pressure... not of head seperation. As long as you don't have a lot of differance between your virgin brass and your chamber.... headspacewise.... and you are sizing with the lee die, you are going to split necks loooooooong before you have head seperation issues. if youve got .005" expansion of Lapua brass, your loads are hot. Id expect .001" on the first firing, but no more than .001" more (.002" total) for the life of the case. I usually load 3 cases to distruction during load development so I know that pressure issues don't manafest long term. That way I can put 5 shots on a piece of brass in 15 shots. if im seeing more than .002" total after the 3rd-5th loading, I know its time turn the volume down a bit.
Ill bet youre in the 68000-70000psi Range if youre seeing .005" expansion at 4 firings. Remember the 243AI Lapua brass you showed me with the ejector mark on the head? About the same pressure, but the magnum brass won't manafest ejector marks as soon because its thicker, and of a harder alloy/annealing.
If its still holding primers fine, id keep shooting it, but back down on the powder buddy.

 

[Jimm]

Ahh sooo! Abinok one ,

Thanks are many , /ubbthreads/images/graemlins/cool.gif I was beginning to wonder if anyone had seen the question mark in the post title /ubbthreads/images/graemlins/crazy.gif

This brass has not had any body sizing and it chambers without any problems . So , shoot it some more you think ?


BTW , for those that use a RCBS bench mounted primer tool , when pockets are only 2 thou smaller than the primers the handle on the primer tool will almost fall of its own accord . It is long and the leverage will fool you . I tried pushing a primer in with my thumb and then pushing on the bench at the 2 thou difference level and you can't / don't want to do it . There is plenty of tension at this level of differences in primer pocket size and the primer size itself .

Thanks again all for your input ( Input , need more input /ubbthreads/images/graemlins/grin.gif )

Adam , did you blow any thing up yet? /ubbthreads/images/graemlins/smile.gif

Jim B.

 

[Jimm]

Hey BB ,

used a thin abrasive cutoff wheel on a air tool . Looks better than it is but I would not / do not fool with Lapua primer flash holes . I can't hold some tool good enough to beat what they are like when I get them . In addition to that I am only loading fot the 700 to 1000 yd distance at this point.

Abinok surmises that I have pushed this brass pretty hard ( which I have , by my chrono readings and other data that I have gotten from this site ) Yet the brass is still chambering without excessive bolt pressure , holds primer well and still gives 3 to 4 thou neck tension obtained with a Lee collet die . Oh yeah , the length is not sufficiently different in length as to require a trimming either ( trimmed after the fireforming round)

Thanks again Adam for the clarification regarding the chamber pressure vs the headspace / case head separation issues .

Jim B.

 

[abinok]

Nope not just yet... probably saturday. Oilfield guys will be over laying some waterpipe... ought to get their attention /ubbthreads/images/graemlins/smile.gif Been on vacation doing some fishing and hiking for the last few days.
Id still use that brass... id just back off a couple of grains.