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'Clumping' Retumbo--Kirby/anyone?

 
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  #8  
Old 09-05-2013, 10:05 AM
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Re: 'Clumping' Retumbo--Kirby/anyone?

The strange thing is that 100g load from this jug of 8lbs purchased last Sept. were fine in April. Normal MV and no pressure signs. But the pressure signs went way up when these same loads were fired a few days ago.

From running some 99g loads over the chrono yesterday and having them chrono the same as when I worked up with this new jug of powder last Sept., it appears that the velocities per load are the same, but pressures have increased. That's only chrono-ing one load, 99g, but the appearence is there.

Pulled the bullets on the rest of the sixteen 99g loads and reloaded at 97g and -.020 vs. my typical -.015 using the Forstner micrometer seating die and Davidson seating depth checker...

Strange. Not happy about losing the velocity, but must find a load here very soon. High buck starts 9/15...
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  #9  
Old 09-05-2013, 12:00 PM
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Re: 'Clumping' Retumbo--Kirby/anyone?

This morning at 97g Retumbo (normal load was 100g last spring with same jug at 2954fps) and -.020 instead of the normal -.015, I'm still getting pressure signs, though less. First round through dirty, cold barrel went 2824fps, then the next three went 2879, 2872, 2867 and grouped well under 1/2 MOA prone at 205 yds on paper, but the first was 2" to the R of the 3 shot group and why the low MV. ??!! But still a shadow of ejector mark on 338 Lapua Brass. This thing should be doing 2950fps with no problems.

I do have some left over Retumbo from an older 8lb. jug that I switched from last year. My load with that was 101g and 2979fps. Perhaps I should investigate if anything has happened with that. Regardless, it sure appears to me at this point in time that something happened to this lot of Retumbo over the last few months....
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In the beginning God created the heavens and the earth. Genesis 1:1

"And can the liberties of a nation be thought secure when we have removed their only firm basis, a conviction in the minds of the people that these liberties are the gift of God?" Thomas Jefferson - Notes on the State of Virginia

www.wildsidesystems.com - Shelter for Your WildSide - http://www.youtube.com/watch?v=tYwgo...&feature=g-upl
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  #10  
Old 09-06-2013, 12:12 AM
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Re: 'Clumping' Retumbo--Kirby/anyone?

Quote:
Originally Posted by royinidaho View Post
My load of 101 gr of 50 BMG in a 338 RUM is compressed behind the 300 OTM and does cake pretty solid.

However, pressure isn't a problem either immediately loaded and shot or if they set for as much as several months.

With Retumbo in the 375 AM with Kirby's std load of 142 grains and the 350 SMK which has been quite a moderate load considering my nature , the last time I was in Townsend and not on a very hot day, she blew a primer.

It's no way a compressed load.

I haven't shot her since.

Maybe there's something going on with Retumbo???

We'll see next week.
Roy, What's your plan going forward with this issue...?
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In the beginning God created the heavens and the earth. Genesis 1:1

"And can the liberties of a nation be thought secure when we have removed their only firm basis, a conviction in the minds of the people that these liberties are the gift of God?" Thomas Jefferson - Notes on the State of Virginia

www.wildsidesystems.com - Shelter for Your WildSide - http://www.youtube.com/watch?v=tYwgo...&feature=g-upl
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  #11  
Old 09-06-2013, 07:01 AM
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Re: 'Clumping' Retumbo--Kirby/anyone?

Quote:
Originally Posted by jmden View Post
Roy, What's your plan going forward with this issue...?
This is a very busy week so won't get anything done regarding shooting.

Next week I'll take'r to the hills along with the chrono and validate things.

The expectation is that that blown primer was a "fluke". Donno. I haven't checked primer pocket expansion yet. Will most probably do this first.

This is the powder and charge weight that Kirby validated accuracy with, with an anticipated velocity of 3250.

I have good base line data. They have been chrono'd right at 3250 average.
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Old 09-06-2013, 08:27 AM
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Re: 'Clumping' Retumbo--Kirby/anyone?

Well, I hope you figure it out and all is OK.
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In the beginning God created the heavens and the earth. Genesis 1:1

"And can the liberties of a nation be thought secure when we have removed their only firm basis, a conviction in the minds of the people that these liberties are the gift of God?" Thomas Jefferson - Notes on the State of Virginia

www.wildsidesystems.com - Shelter for Your WildSide - http://www.youtube.com/watch?v=tYwgo...&feature=g-upl
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  #13  
Old 09-06-2013, 08:29 AM
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Re: 'Clumping' Retumbo--Kirby/anyone?

Have you guys taken an abrasive cleaner to your barrels at all, like the KG or JB, and made dang sure your carbon has not built up. I use a lot of Retumbo and I'll start getting pressure signs if I don't address carbon aggressively once in a while.
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Old 09-06-2013, 09:24 AM
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Re: 'Clumping' Retumbo--Kirby/anyone?

Quote:
Originally Posted by bigngreen View Post
Have you guys taken an abrasive cleaner to your barrels at all, like the KG or JB, and made dang sure your carbon has not built up. I use a lot of Retumbo and I'll start getting pressure signs if I don't address carbon aggressively once in a while.
I have wondered if there's a barrel change as the same issue came up when I used a reduced load of an older lot of Retumbo as a test yesterday. So two different lots of Retumbo from two different 8lb jugs purchased 3 years apart or so, the newest purchased last fall and each showing significant pressure at reduced loads that should be very pedestrian and have proven to be in the past for this rifle. The odd thing is this barrel was shooting well 3.5 months ago, sat in the safe and the loads seem to have changed significantly even after doing a thorough cleaning.

I have not used abrasive cleaners on my barrel. Just BoreTech Eliminator (do use brass brushes as I've talked to folks who scope a barrel after using nylon brushed and then compare to using brass brushes and say theres a quite a difference) and then a pass with gun oil and then patch dry. More to it than that, but that's the basics.
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In the beginning God created the heavens and the earth. Genesis 1:1

"And can the liberties of a nation be thought secure when we have removed their only firm basis, a conviction in the minds of the people that these liberties are the gift of God?" Thomas Jefferson - Notes on the State of Virginia

www.wildsidesystems.com - Shelter for Your WildSide - http://www.youtube.com/watch?v=tYwgo...&feature=g-upl
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