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Something odd has started to happen...

I have just swapped from 180 Targets to 180 Hybrids in my 7mm SAUM, I used to jam the Targets by 5 thou but the Hybrids are 13 thou off the lands. I do need to bump the shoulders back on these cases as they are getting tight. The load is 60 grains of N560. chronoing today gave quite keen results with one oddity:

2890
2888
2892
2891
2883
2875**
2883
2889
2889

So ignoring the ** one I see 2883 to 2892 or 9fps spread - Not great but certainly not bad. Today I stated seeing sooting on the necks and moving back down the shoulders like this, it is not a uniform ring as it extends down slightly in one quadrant on all the cases I fired today. Cases have been shot 5 times and not annealed so far so they are due to be done. Anyone got any views on why it is has suddenly started sooting like this? The barrrel has around 500 rounds through it and I will haul the borescope out over the weekend to take a look at the throat. :

My guess is that annealing will cure the problem as the necks are not sealing the chamber during firing because they have got hardened.
With an overbore cartridge like the 7mm saum this will happen sooner than a less overbore cart.
Just my guess.

Garry

ovenpaa wrote:Something odd has started to happen...

I have just swapped from 180 Targets to 180 Hybrids in my 7mm SAUM, I used to jam the Targets by 5 thou but the Hybrids are 13 thou off the lands. I do need to bump the shoulders back on these cases as they are getting tight. The load is 60 grains of N560. chronoing today gave quite keen results with one oddity:

2890
2888
2892
2891
2883
2875**
2883
2889
2889

So ignoring the ** one I see 2883 to 2892 or 9fps spread - Not great but certainly not bad. Today I stated seeing sooting on the necks and moving back down the shoulders like this, it is not a uniform ring as it extends down slightly in one quadrant on all the cases I fired today. Cases have been shot 5 times and not annealed so far so they are due to be done. Anyone got any views on why it is has suddenly started sooting like this? The barrrel has around 500 rounds through it and I will haul the borescope out over the weekend to take a look at the throat. :

necksooting.JPG

Annealing is my offer, 2875 probably the hardest case of the bunch?

How you handle them matters too, as any 'working' of the metal, bashing them together, dropping them on a hard surface etc. will contibute to the hardening process.

Thank you both of you, annealing does make sense so I had better get some Tempilaq in and get it done. It will make sense to anneal before bumping the shoulder back and probably make the process easier at the same time. I also need to get some more gas as all I have at the moment is MAPP that will all but vaporise the necks.

I take it you managed to miss your own Chrono then and only shoot other peoples :lol:

Alan

:lol:

That was rather harsh :lol:

I think even my Chrono was nervous and despite the sand bags holding it down it still eventually threw itself on the floor, I think it surrendered at that point!

ovenpaa wrote:That was rather harsh :lol:

I think even my Chrono was nervous and despite the sand bags holding it down it still eventually threw itself on the floor, I think it surrendered at that point!

chrono.JPG

Sorry mate I couldn't resist :lol:

It sounds like you had a good day reading the other thread.

I'm hanging on a bit before I replace my (your )Chrono, I can't make up my mind which to have, and with the AR hopefully imminent (assuming Lincoln get my variation done) I need the cash.

Alan

Midway claim to have a deal on a crono on their home page

http://www.midwayuk.com/

DM