Compression of BP

[GregLaROCHE]

How much can you compress BP? What happens if you compress I too much?
Thanks

[martinibelgian]

The case will bulge and you won't be able to load the cartridge..

[Randy Bohannon]

What M.B. said.

[country gent]

I have worked loads up using a chronograph to watch the numbers along with the accuracy as I added powder and compression. I have also when at the velocity level experimented with adding just wads to increase only compression.

Its interesting to start at no compression / no air space in the case and work up in 2 grn increments choreographing them. Accuracy will be improving and the Extreme spread starts dropping along with Standard Deviation numbers. When you get to the best 2 loads the ES and SD numbers are very close and fouling is lightened and easier to work with. I then test at the mid point of these 2 loadings. Once the Ideal point is established I then try a wad .030 thinner and one .030 thicker just changing compression to see what it shows if a direction shows marked improvement in accuracy
ES or SD is shown then I work in that direction in .030 increments.

Some powders may have a couple of these "sweet" spots working up. But you will see it as going up to the point numbers are dropping And accuracy improving moving away they are increasing and accuracy is slightly enlarging to the point where again it all is starting to drop.

In my limited experience heres what I have found to be rough points. In the 38-55 - 45-90 case sizes.
Swiss likes the least compression is very consistant and light fouling seems to work around .060-.080 compression
Olde Ensforde likes a little more compression but when at the right spot fouling is easy to deal with. Seems to like between .150-.180 compression.
Goex seems to want ALOT more compression than the other 2. Fouling is the heaviest and may require wiping between shots. With right compression and lube fouling stays soft. Seems to want .250+ compression.

To much compression can swell case bodies, crush powder kernels, And possible bend ( banana rounds), if compressing with a bullet it can distort or bend these long soft bullets.

[rfd]

this is a good question, and once you know not to have loose bp powder that promotes unwanted air space in a case, some amount of compression is required to be sure there is no air space. the rest will always require experimenting - there's no way around that if yer looking to increase accuracy. that's how much compression you will require.

[Nobade]

If you have a stout enough container and can generate enough force it will become one solid piece. That's how you make rocket engines.

[Lead pot]

Attachment 233345Attachment 233346

When it gets down to around zero I do a bunch of things like why ?.....what if ?....how much ?..... well compression came one winter There was talk that compressing a load to get more velocity but there is an end when you don't gain any more. I never got enough powder in a case to find this out. The first photo is .050', .100" .200" 2nd, .300", .400" and .500". I never found the diminishing end where it stopped but it did slow down starting at .500" I had one more but lost the picture at .600" that was packed solid. At .100" it starts packing and it gets harder every .100" added down the line. What I did find on the snow was unburned powder including a big hard packed chunk that streaked the snow about 50 yards.
I think what is going on when you start compressing say the Goex that always left a brighter bore with compression is the hard pack with the .350" I used to compress it is the unburned compressed powder scrubbed the bore on it's way out.
I have compressed swiss all the way to .350" and I found two points with accuracy. One with .050" and again at .300". My OE powder I use in the .44-100 and the .45-90 for long range shoots well using .200" compression.

But your question, how much can you compress black I would suggest load some ladder load rounds with .050" compression and work up but I would bet that you would not need going past .200" and most likely the .050" will get the job done.

[indian joe]

Attachment 233345Attachment 233346

When it gets down to around zero I do a bunch of things like why ?.....what if ?....how much ?..... well compression came one winter There was talk that compressing a load to get more velocity but there is an end when you don't gain any more. I never got enough powder in a case to find this out. The first photo is .050', .100" .200" 2nd, .300", .400" and .500". I never found the diminishing end where it stopped but it did slow down starting at .500" I had one more but lost the picture at .600" that was packed solid. At .100" it starts packing and it gets harder every .100" added down the line. What I did find on the snow was unburned powder including a big hard packed chunk that streaked the snow about 50 yards.
I think what is going on when you start compressing say the Goex that always left a brighter bore with compression is the hard pack with the .350" I used to compress it is the unburned compressed powder scrubbed the bore on it's way out.
I have compressed swiss all the way to .350" and I found two points with accuracy. One with .050" and again at .300". My OE powder I use in the .44-100 and the .45-90 for long range shoots well using .200" compression.

But your question, how much can you compress black I would suggest load some ladder load rounds with .050" compression and work up but I would bet that you would not need going past .200" and most likely the .050" will get the job done.

LP
Dont know whether this fits your experience but I seem to get more resistance to compression in my bottle neck case (45/75) than in a straight case (45/70) ......so....... the 45/75 is more packed at the neck end and less so near the primer . ???

[Lead pot]

Joe I have three BN rifles, two .44-90 BN's and a .44-77 and all three shoot best with almost no compression. With moderate compression say .250" I have pulled the case necks off the .44-90 bn. Also it's important to keep the wad stack above the shoulder in the case neck.

[indian joe]

Joe I have three BN rifles, two .44-90 BN's and a .44-77 and all three shoot best with almost no compression. With moderate compression say .250" I have pulled the case necks off the .44-90 bn. Also it's important to keep the wad stack above the shoulder in the case neck.

ye ouch! blew the neck off - that would make us scratch the whiskers for a while.
I'm using homemade powder - less density in the poured charge to begin with - and with this stuff takes way more depth of compression to get to the same point of density in the charge as say goex (still have some 5FA I use for comparisons like this). I think from your pictures and if we disected a load you would tell me I am using light to moderate compression.
Wad stack --yeah -- the 45/75 is touchy there - If I use the 405 grain boolit seated for magazine feed the wad is right at the point of the shoulder (or a whisker below) -- only use a 30thou juice box wad for that load.
Also been shooting pointy boolits (single loaded) over a 45 thou HDPE wad but they loaded to kiss the lands and wad is nicely in the neck still - nice accurate load too! Have gotten some nice clover leafs that indicates if the bunny at the back end was better we could do MOA at 100yds with that - hadda fit a new magazine to do it. Had me some fun with all this last year

[Lead pot]

Here is one load session with too much compression with the .44-90 bn. I normally don't use a lube wad but I think this had something to do with the case separation and hard compression without a lube wad. if you look at the other cases they got pulled past the throat but held.

Attachment 233391

[indian joe]

Here is one load session with too much compression with the .44-90 bn. I normally don't use a lube wad but I think this had something to do with the case separation and hard compression without a lube wad. if you look at the other cases they got pulled past the throat but held.

Attachment 233391

Man ! that was not a fun session at the range
See if this fits your thinking
(I use a small press with more or less direct linkage for my powder compression - like to be able to feel whats going on as much as possible and I can also put a scale on the handle to get a comparison of the effort required)

I reckon from what I feel doing this is the powder at the neck end of the case compresses really tight but not much of that transferrs down the powder column
- had even considered compressing a half charge down in the body of the case then topping it up and compressing again to even up the amount of compaction down the column - didnt do it - (how much foolin around do we really want to do in the loading room?)

anyway I kinda picture a plug of compacted powder in the neck and down below the shoulder a bit and the body of the case is less so - AND - it seems to be peculiar to BN cases (yeah you get the same thing in a straight case but seems not to anywhere near the same extent)

I have dug a few compressed loads out of cases and seems to support the thinking here.

So --if thats happening we have kind of a plug of heavy compressed powder at the neck end of the case - being blasted out before it gets to burning - add in a paper patch boolit? and thats more grip on the neck of the case (even tho its a slip fit - once the fire starts - the paper patch has to be more sticky in the case neck than a greaser boolit) ?????

Dunno -- glad it was you had the excitement not me!!

[Lead pot]

Man ! that was not a fun session at the range
See if this fits your thinking
(I use a small press with more or less direct linkage for my powder compression - like to be able to feel whats going on as much as possible and I can also put a scale on the handle to get a comparison of the effort required)

Joe I load by weight and the case is filled with the same hight in the case for the amount of compression I want. I only use the minimum that I need so I don't even think about pressure. I use a Rockchucker for most of my loading as well as a Turret and for heavy work I use a RCBS A5 Big Max I converted the lineage for forming brass that needs a little more pressure than the Chucker has,

I reckon from what I feel doing this is the powder at the neck end of the case compresses really tight but not much of that transferrs down the powder column
- had even considered compressing a half charge down in the body of the case then topping it up and compressing again to even up the amount of compaction down the column - didnt do it - (how much foolin around do we really want to do in the loading room?)

Most of the rounds I load hold 82 to 118 grains of powder and I use none to very little compression and 80 grains will reach as far as my sights have elevation on the staff. My small caliber is a .40-65 I use for midrange and it gets loaded with 57 gr to 62 grains and not much compression again and this is enough to get the job done to 600 yards. I use the caliber for the match I'm shooting.

anyway I kinda picture a plug of compacted powder in the neck and down below the shoulder a bit and the body of the case is less so - AND - it seems to be peculiar to BN cases (yeah you get the same thing in a straight case but seems not to anywhere near the same extent)

A heavy compressed load I had in that .44-90 bn was 100 grains and that just about brings the powder up to the top of the case neck. Compressing that around .300" will compress it below the shoulder and that hard pack I think had something to do with pulling the necks with the added pressure the compressed mass below the neck and the lack of the lube wad that would have reduced the friction.

I have dug a few compressed loads out of cases and seems to support the thinking here.

So --if thats happening we have kind of a plug of heavy compressed powder at the neck end of the case - being blasted out before it gets to burning - add in a paper patch boolit? and thats more grip on the neck of the case (even tho its a slip fit - once the fire starts - the paper patch has to be more sticky in the case neck than a greaser boolit) ?????

My PP bullet is only in the case 1/8" so the bullet is not a factor it was the compressed mass of powder under the shoulder that did the dirty work.

Dunno -- glad it was you had the excitement not me!!

It was not much of a problem getting the pulled case necks out of the bore. I have tools to get this done in a hurry.

[ian45662]

I compress my Swiss loads about .160 or so. My OE loads are compressed a little more but I can’t remember off hand how much. There will be a point where accuracy starts to fall off. That’s when ya know your going to far.


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[indian joe]

It was not much of a problem getting the pulled case necks out of the bore. I have tools to get this done in a hurry.

I load by weight also - but using that small press gives a feel of it as well - a compound press like a Rockchucker just squashes stuff real easy - once I have a load I use a measured die rod in the small press to get even compression

What I was getting at is I think the bottle neck case somehow gets a more compacted slug in the neck/ top of shoulder than we get with a straight case. (compared to the restof the charge)

Am thinking of putting a 40 cal barrel aside for later - do you think the 40/65 has enough juice shooting grease boolits for 600yards??

Have a friend put a 40/82 together in a single shot - looked like a good idea at the time - its shooting good but he reckons it boots him.

[Lead pot]

Joe my .40-65 has a chamber to tight to load a groove diameter GG bullet, it will not except a patched bullet .404" in diameter loaded in a fired case so I can't say what a GG will do at 600 yards. But I will say this I shoot against shooters that use the GG in their .40-65 that whoop me using it
I also have a Browning BPCR chambered in a .40-65 but I have not used it past 200 yards. I take it to the range for a young person that wants to shoot a black powder rifle a few times so they don't get the heavy recoil I'm using.

[indian joe]

Joe my .40-65 has a chamber to tight to load a groove diameter GG bullet, it will not except a patched bullet .404" in diameter loaded in a fired case so I can't say what a GG will do at 600 yards. But I will say this I shoot against shooters that use the GG in their .40-65 that whoop me using it
I also have a Browning BPCR chambered in a .40-65 but I have not used it past 200 yards. I take it to the range for a young person that wants to shoot a black powder rifle a few times so they don't get the heavy recoil I'm using.

Thanks for the reply - it might help me make a sensible choice (not being renowned for sensible choices)