New guy question

Discussion of BPCR loading techniques, SAFETY, Case Cleaning and Prep, Indexing, BP Choice, Primers, Wads, Compression, Drop Tubes, Vibration, Load Testing, etc.
macca
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Re: New guy question

Post by macca » Tue Sep 06, 2016 5:27 pm

Hi Bruce
the charcoal portion of bp is very fragile and crushes very easily. If you compress to the same level from different starting points (poor drop tube technique) then you end up with powder columns of different consistency and hence different burn rates.
One of the advantages of breech seating is an unpacked powder column
cheers macca
A Sudoku a day keeps alzheimers away ........I think

Brent
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Re: New guy question

Post by Brent » Tue Sep 06, 2016 6:56 pm

I don't find that bp crushes all that easily and it never crushes uniformly though the case. The top always compresses more and, if breakage occurs, that's where it happens. Much of the fragmented powder, however, is often due to having to dig the powder out of the case once it has been crushed. The digging does it more than the compression.

Frankly, we know that compression works, including for Swiss. How much depends on other details that we don't understand, but we can find via experimentation. Personally, I compress it less than 0.1" but then, I probably do a better job of settling it in the case first, but all that matters is what works on the target.

Muzzleloaders use, effectively, zero compression. Yet, they shoot pretty darn well. On the other hand, they don't seem to have any special hold on the accuracy trophies relative to compressed cartridge loads.

What is pretty clear is that Swiss powder is more accurate for far more people, than any other manufacturer's powder.
I'm not from here, I just live here.

Kurt
PostsCOLON 636
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Re: New guy question

Post by Kurt » Tue Sep 06, 2016 10:15 pm

Here is an example of compression from .050" .100" .400" .200" .300" .500"



ImagePowder compression from .050"-.100"-.400" by Kurt, on Flickr

ImagePowder compression from .200"-.300".500" by Kurt, on Flickr

bruce moulds
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Re: New guy question

Post by bruce moulds » Wed Sep 07, 2016 12:18 am

kurt,
what king of powder is that?
the swiss I use does not seem to compact that solid.
that said I have never really gone over 0.250.
inability to chamber bulged cases can rear its ugly head when compressing.
macca,
breech seating is the opposite of compressing, or negative compression
the airgap makes it the equivalent of using loose powder.
the only reason to droptube here is to get more powder in the case.
keep safe,
bruce.

Kurt
PostsCOLON 636
JoinedCOLON Mon Nov 21, 2005 8:05 am

Re: New guy question

Post by Kurt » Wed Sep 07, 2016 8:07 am

Bruce.

I don't remember for sure if it was Goex Express or Schuetzen I was using back then.

I will say this, I would nut breach seat with .300" compression with a 1/4" gap between the bullet and the compressed powder even with out a wad used. Even the .200" compression was solid the first 1/2". It crumbled when I handled it, but it was solid. It would hold the air like a wad would when the load was set off.

bruce moulds
PostsCOLON 85
JoinedCOLON Mon May 04, 2015 11:47 pm

Re: New guy question

Post by bruce moulds » Wed Sep 07, 2016 4:29 pm

kurt,
with breech seating, there is no point in compressing.
just droptube the case full such that the wad is level with the top of the case.
droptubing gives a consistent packing of powder.
all tuning is done by adjusting the airgap, which might be as small as 1/16" in a 32, up to 1/8" in a 40 or 45.
each gun has its own rules of course.
keep safe,
bruce.

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