Dual diameter 40-82 revisited

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semtav
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Re: Dual diameter 40-82 revisited

Post by semtav » Sat May 15, 2021 8:38 pm

Was reading the 7* thread and got to thinking about paper rings.
Every one of my shells had a very tiny paper ring on it, and I thought maybe if I could find a couple of my bullets, I could see if there was a ring or something show up .2 from the base, where my ring should have come from.
I searched til I found two bullets. It appears one went thru the door, and one was one of my sighters trying to find the door.
I knew there would be some damage, but I was particularly looking to see the rifling and where the bullet sat at the mouthof the case.
I can see no damage in this area to make me believe the paper ring is doing any damage to the bullet.
It also appears this 12.5-1 alloy is bumping up the full length of the paper right to the molded ring.


40-82 bullets.jpg
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powderburner
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Re: Dual diameter 40-82 revisited

Post by powderburner » Sat May 15, 2021 9:22 pm

I havent yet figured out where they come from but it would seem if they were from the chamber mouth they would pull the back half of the patch off, but i dont know that.
I always thought they came from the bullet base as it cleared the case mouth.
I used a chamber swab with the std chamber to pull the rings out. They were always very consistent in size. Without the swab chambering was not possible.
Maybe my wad stack pulls them off the case mouth. Didnt ever have them there.
Dean Becker
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bruce m
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Re: Dual diameter 40-82 revisited

Post by bruce m » Sat May 15, 2021 10:53 pm

brian,
your photo shows well the fact that harder lead/tin alloys bump into the rifling well.
however it also minimizes nose setback.
from studying confetti i have found that 12:1 requires shorter patches than 16:1.
these 12:1 bullets also require a little less comeup than 16:1, suggesting that reduced setback of the nose improves b.c. by maintaining a longer ogive.
there is an argument that harder lead/tin alloys are lighter, and therefore start faster with the same charge, and thus shoot flatter.
while this could be true, i feel that at 1000 yds the b.c. advantage would have more effect.
the lighter bullet of the same dimension, if that dimension remains the same in both cases, will have a slightly lower b.c than the heavier one, but the lighter one retains a more original shape.
this debate could be tested by live firing over a chronograph, but who has the time?
the fact that the harder bullet shoots with less drop is all you really need to know, and less drop = less time of flight = less wind deflection.
given that few if any can only calculate wind deflection to a percentage of what it really is, the less you have to start with, the less wrong will be your call.
this could mean 1 or 2 shots on the better side of the line, which could be 1 or 2 more points in a match.
who does not want that?
bruce.
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bruce m
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Re: Dual diameter 40-82 revisited

Post by bruce m » Sat May 15, 2021 10:55 pm

powderburner,
does recovered confetti give you any hint as to where the rings might come from?
i have seen base bits with a bit of patch attached up to about the case mouth area.
bruce.
ventum est amicus meus

semtav
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Re: Dual diameter 40-82 revisited

Post by semtav » Sun May 16, 2021 6:48 am

powderburner wrote:
Sat May 15, 2021 9:22 pm

I always thought they came from the bullet base as it cleared the case mouth.
Dean,
You may be spot on.

Little cold this morning so I went confetti hunting while I wait for it to warm up.

All were found 2 steps in front of the line








40-82 PATCHES.jpg
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powderburner
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Re: Dual diameter 40-82 revisited

Post by powderburner » Sun May 16, 2021 6:56 am

Not really. Its really hard to find here unless i can shoot over a sagebrush.the range is barren and there is always wind
The patches i have recovered usually are just the base fold. They are unwrapped and the biggest pieces found.
The lower strings in your picture is about what i find, the rest is little squares unless i use a heavy patch then i get what you show.
Dean Becker
only one gun and they are 74 s
3rd asst. flunky,high desert chapter F.E.S.
MYWEIGH scale merchant
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semtav
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Re: Dual diameter 40-82 revisited

Post by semtav » Sun May 16, 2021 7:44 am

From that patch info, i would surmise that neither the patch, nor the bullet are bumping up into that transition area upon initial ignition.

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powderburner
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Re: Dual diameter 40-82 revisited

Post by powderburner » Sun May 16, 2021 8:11 am

Once you get the bullet across the transition and bumping up in the barrel i think you are where you want to be.
Dean Becker
only one gun and they are 74 s
3rd asst. flunky,high desert chapter F.E.S.
MYWEIGH scale merchant
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semtav
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Re: Dual diameter 40-82 revisited

Post by semtav » Sun May 16, 2021 11:54 am

40-82 test 2.jpg


Tried again with same load.
barely perceivable wind from the left when I started.
first two shots were the bottom two and pretty sure the bottom one was the fouling shot, shot with a clean , lubed barrel.

after shot 4, the wind changed to a left quartering tailwind and started increasing.
shot 6 and 7 were with more wind than 5.

I was only going to shoot 5 shells, but thankfully I had 2 extra or DD would have blamed shot 5 on the old PP Syndrome !!
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bruce m
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Re: Dual diameter 40-82 revisited

Post by bruce m » Sun May 16, 2021 4:48 pm

well brian,
doesn't that picture tell a story.
keeping notes on what the wind was doing is a crucial part of it.
roughly a 1 moa change in elevation with a tail wind and so on as shots progressed.
you and the rifle/load were performing well enough to demonstrate that.
sometimes it could be easy to overlook potential by blaming yourself or the load. :?
the problem now is applying that to what to do in competition under pressure.
the old dead guys kept intricate notes of such things in their sight setting book, as well as barometric pressure, which helped them a lot in the days of no sighters.
i knew an old aust palma shooter who went to raton with a team many years ago, and he always related the story of how high the aussies shot with their original aust sight settings. thinner air and higher elevation than at home.
looking at your confetti shows 2 kinds.
the bottom ones seem to seperate at the foldunder, while the top ones seperate a bit up the shank.
could the latter seperation be at the case mouth/ elsewhere?
does it matter, and if so why?
bruce.
ventum est amicus meus

semtav
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Re: Dual diameter 40-82 revisited

Post by semtav » Sun May 16, 2021 5:34 pm

That was my whole plan this summer, to see if i could improve my wind skills.

I May play a little with the paper, but otherwise leave the load alone. I'm only camming it the width of the rim, and it barely takes any pressure.

I need to look at that confetti again to see what you are talking about. I only see one total separation and thats at the fold in the base.

bruce m
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Re: Dual diameter 40-82 revisited

Post by bruce m » Sun May 16, 2021 5:50 pm

brian,
the load looks good enough to use for developing wind skills :D
bruce.
ventum est amicus meus

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desert deuce
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Re: Dual diameter 40-82 revisited

Post by desert deuce » Mon May 17, 2021 7:19 pm

Agree with Bruce, dispense with the testing and get on with the shooting! Wind or no wind.

After all, it is the target that matters. Good to know you can hit a refrigerator from 300 yards though. :D
Sometimes you get the chicken, and sometimes you get the feathers!

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powderburner
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Re: Dual diameter 40-82 revisited

Post by powderburner » Tue May 18, 2021 7:34 am

Brian are those patches heavy vellum? How thick are they?
Dean Becker
only one gun and they are 74 s
3rd asst. flunky,high desert chapter F.E.S.
MYWEIGH scale merchant
reclining member of O-G-A-N-T

semtav
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Re: Dual diameter 40-82 revisited

Post by semtav » Tue May 18, 2021 9:02 am

It was a package of Sears 9 lb onion skin

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