17HH flash holes; culprit?

[20 EXTREME]

Originally Posted by Kevinj

http://s1281.photobucket.com/user/ke...3497f.jpg.html

Some pictures of 17 hh primer pockets.

Unfired brass measured at extractor groove.
[IMG][/IMG]

Factory ammo measured at extractor groove showing about 0.005" expansion of the web.
[IMG][/IMG]

Happy to say that all I have left of the 17 HH are 7 screwed up brass and the memory of the last shot fired blowing up in buddy's face.

As of yesterday I will not have to fireform any more brass or work up loads for the 17 AH as well.

[sgtg]

20 EXTREME; Was that blown primer factory, or some of the bad brass that you loaded? I will say my 17 HH experience started a little rough with the bad brass and on my Savage the crown was just terrible. I fixed the crown and it is now a tack driver and the star of the show out prairie dog shooting. sgtg out

[lanenebraska]

Originally Posted by Kevinj

http://s1281.photobucket.com/user/ke...3497f.jpg.html

Some pictures of 17 hh primer pockets.

I just did a hundred that were the same. That's a lot of brass to take down. I ended up placing the cases in my cordless drill, then gently chucking them in. They don't move, and with no power to the drill, just push them over my Lyman case prep reamer. Made the whole process a dream
now they all look like your pic:

[Tilleyman]

Originally Posted by wally bennett

You dont need to dunk brass after annealing its the heating that anneals it not the cooling.
Wally

That's correct... the quenching is to stop the heat travelling further up the case and softening the head area

[Tilleyman]

At .2930" dia that brass is WAY undersized compared to any factory ammo or new brass I've seen... which all measures .2945"...

[20 EXTREME]

Originally Posted by Tilleyman

At .2930" dia that brass is WAY undersized compared to any factory ammo or new brass I've seen... which all measures .2945"...

The blown primer was a factory round. I measured the brass in the extractor groove which measured about .2930" on all unfired brass. This gives a better measurement of the web expansion as the extractor groove is cut into the web area. Expansion at the mouth of the primer pocket was greater at about 0.007" This is what I believe gave Hornady the impression that it was a tapered primer pocket issue. However this was a perfect example of too much pressure for the web to handle. The five rounds shot before this had progressive expansion to the point that the sixth one blew. This indicated to me that chamber temperature contributed to an already over pressure factory load.

[Tilleyman]

Aha... thanks for the clarification, I thought you were measuring just in front of the groove, which on Hornady, RWS and PRIVI brass is .2945".

Out of interest, do you have that measurement on the blown Hornady cases?

It would also be interesting to see how much web thickness is left if the primer pockets have to be deepened significantly to get within standard specifications and leave a square end face to seat the primer.
Any chance of sectioning a case please?

When I sectioned a 17 Hornet Hornady case I was surprised to find there was not a decent radius where the case walls meet the head... standard engineering practise to reduce stress risers. I can understand why it is not present in low pressure 22 Hornet brass but the 17 Hornet operates at a max of 50,000 psi according to SAAMI.
It does however, maximise case volume... and when combined with the proprietary Superformance powders therefore maximises velocity.

If the web thickness has been reduced it may affect hoop strength of the head area and lead to primer pockets expanding more readily as loads approach maximum.

Such a pity Hornady dropped the ball on the 17 Hornet, its a great little cartridge

[Bill K]

Interesting a few weeks back the proper place was to measure expansion of the case, was .002 above the data line or web. Now it is at the extractor grove Blown primers are most often due to excess pressure on reloads.
I know numerous people that have used thousands of factory rounds and have not had one blow the primer like shown. It has always been a reloader using a charge that is too much for his weapon. Especially in the 17HH or other high intensity rounds of small size, which can jump in pressure with just a tenth of a grain, compared to large capacity rounds that can take 1/2 to one full grain to show pressure.. VERY INTERESTING ??? Bill K

[ray h]

Could you give a little more detail about the 6 shots that went from ok primers to blown primers. I'm trying hard to wrap my old brain around that.

[Bill K]

Originally Posted by ray h

Could you give a little more detail about the 6 shots that went from ok primers to blown primers. I'm trying hard to wrap my old brain around that.

And also the measurement, as one other poster asked about before and after the blown primer, at the extractor groove Bill K