Black Powder Compression

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  • Last Post 28 September 2009
Dead Tree posted this 17 September 2009

I am a newby. Trying to become good enough to compete. Working up loads for a 45-70. Casting and testing bullets. I have been very careful of case capacity, drop tubing, vibrating and very slight compression. Trying to do everything just right.

Last night I read a article in “Black Powder Cartridge News", by Bob Woodfill that in short says, “Compression has no effect on velocity or accuracy". His test used upto 1/2 inch compression. His premise was well suported with statistics. Also bullet seating depth had little effect.

I would like to ask others with more experience their thoughts.

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Notlwonk posted this 17 September 2009

There is a book by J. S. and Pat Wolf...."Loading cartridges for the original 45-70 Springfield Rifle and Carbine".That would be very beneficial to you for reloading Black Powder, especially if your shooting a trap door. The book is very consistent in saying that you need to:

  1. drill flash holes to .096

  2. Use only Win. MAG or Fed. MAG primers

  3. Use heavy compression of the powder

  4. Use 405 gr hollow base or 500 gr bullets that are cast 20:1 or softer.

  5. Taper crimp.

Me?  Can't find the proper primers and there are a couple other tricks he uses that I'm not set up for. Maybe when the primers become available I'll give black another try.

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JetMech posted this 18 September 2009

I've been working with a Browning BPRC in 45-70 for about 2 years. My experience has been that Goex 2X requires a fair degree of compression for good consistancy. Swiss, less so. I actually had 45 cases seperate just below the bullet because I had .050 compression and, during the trip to the range, bouncing around in the Jeep, apparently the powder broke down alittle and I ended up with some air space under the bullet! Now I use about .200 compression and seat the bullets so they engage the rifling when the action is closed. Primers, another good subject. Initially, I whent with the published reccomendations and used Federal Mag primers. After some research, I switched to CCI Standard Match. The reasoning is that during the BP era, primers were mild by todays standards. In fact, they were too weak to consistantly ignite the new-fangled “smokeless” powder (viewed a passing fad by hard core BP enthusiasts). Primer manufacturers were forced to come up with newer, hotter primers. The thinking is that all the care taken to carefully drop the powder charge, compress the charge, seat wads is a critical process in the creatin of a good, long-range BR cartridge. Modern, hot primers, especially mag primers, upon ignition, disrupt that carefully assemled powder column. Most successfull BP shooters have tried a variety of ways to soften the effect of the primer on the powder column. Over-primer wads have been used with success, as well as pistol primers. I currently use CCI LR match primers with a 100# weight bond paper over-primer wad. By the way, I shoot a Lyman 525gn Postell. Over time, my 100 yd groups have shrunk from an initial 4” 10 shot string to 1 1/2". The nature of the beast is that those group sizes stay fairly consistant out to the 200yd line! HTH.

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John Boy posted this 18 September 2009

I would like to ask others with more experience their thoughts. DT, IMHO the debate about compression will continue for many years: hard - some - little compression or none at all.  Plus, agree with Dollar Bill that specific powders have specific compression wants to make for good or just average groups.  And it also is bullet caliber dependent, I believe.

Shooting Goex Cartridge in a 45-70 just loves a hard powder column (75grs) and gets me out to 1000yds with excellent accuracy.  But when I pack 48grs of it into a 38-55 - poor groups.  And what I could never figure out is how this caliber round had 55grs of FFg packed in it, aka the 38-55 round.

So, the best answer I can offer up is - one has to fiddle with compression, caliber and loading data specific to determine what one's rifle likes with a given bullet.

The theory with original powder is little or no compression to lite the powder column with as little briance as possible - the reason now to use primers with smaller briance that are currently made to ignite nitro powders specifically and use a wad in the primer pocket or under the primer hole.

Lastly, I just received my BPCR News today and haven't read the article about bullet seating depth had little effect.  There are 2 basic ballistic axioms:  the best bullet base one can cast and the bullet presented to the axis of the bore for concentricity.  Seating a bullet to the crimp groove, for me, creates less accuracy than seated in the leade or engraved in the leading bore cuts (engraved).  Then again, I get real good groups using the 457124 and 457125 bullets and they are nowhere near the leade or bore cuts.  So, :thinking: could it be bullet dependent? 

I'll offer this up for discussion:  a fat round ball presented to the forcing cone will shoot like blazes.  Present a skinny pointed conical to the forcing cone and it will wabble into the bore

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Maven posted this 19 September 2009

Re compression:  Several years ago I was given an old, unfired.50-70 round (with rounded primer) that I later pulled apart.  The BP it contained was compressed into a very hard “cake” or mass and burned very quickly. (Don't ask how I know this!)

Re primers:  The experts have gone back and forth about them:  LR regular v. LR magnum primers.  The only way you'll know for sure is to test each for accuracy and velocity to determine which is better in your rifle with a given powder charge and CB.

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Tom Acheson posted this 19 September 2009

Typing this on a Mortola Q so scuse the 'penmanship'.

First summer with my first BP rifle a C. Sharps .40-65. Tried Goex and Swiss 1.5. Mould is a Brooks custom 415 gr. and alloy is 20:1.

First get OAL set, have bullet contact the lands. Swiss works best for me. Min. charge should be enough to require a 'touch' of compression. Then try stiffer charges. Eventually one will surface as 'the best'. My charge range was 57 to 62 gr. 59 is best (for my rifle). MV is 1283.

Tried all of the 'expert suggested primers'. FC 215mag match were best.

I was at the CBA Nat Tournament in Raton last week and had time to 'play' on the BP sil range. Got all of my sight settings for the 4 animals. Was a blast!

Lots to learn but am off on the right foot.

Tom

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Dale53 posted this 19 September 2009

I shot BPCR Silhouette for about 15 years until vision problems took me out of the game.

However, when I was shooting, I was competitive. I put a twenty power scope on my rifle and tested, off the bench, to five hundred yards.

I learned, that for me, I was best off with seating the bullet into the lands (just touching).

I would load up a series of cartridges starting with NO compression. Then, the next load would be increased two grains. And so on. Starting out the groups were invariably rather large. Then, they decreased in size as compression increased. At a certain point, the groups would start opening up again. That is where you go up and down by just one grain. You're there. The load is correct. With the lot of Goex I had, I needed .350” compression for best results. Swiss only required .085” compression.

Believe me, it DOES make a difference. To recognize this you have to be able to shoot a rather heavy recoiling rifle off the bench at match accuracy levels and the twenty power scope is a BIG help.

After the proper load is found, then load up LOTS and shoot, shoot, and shoot some more.

Regarding primers - let your rifle tell you what it likes. Remember, only change ONE thing at a time in your quest for accuracy.

Dale53

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JetMech posted this 21 September 2009

Dale53 wrote: Believe me, it DOES make a difference. To recognize this you have to be able to shoot a rather heavy recoiling rifle off the bench at match accuracy levels.After the proper load is found, then load up LOTS and shoot, shoot, and shoot some more.

Remember, only change ONE thing at a time in your quest for accuracy.

Dale53Great advice, Dale. In think half my time has been spent on bench technique, to include the best recoil pad I could find! Shoot, shoot, then shoot some more.

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chuebner posted this 22 September 2009

With the lot of Goex I had, I needed .350” compression for best results. Swiss only required .085” compression.

Dale,

Your compression is measured from where.  I often see a figure given for compression but no reference is made as to where it was measured from.  Say I'm loading 65gr. of 2F GOEX and using a 24” drop tube.  The powder column is “X” below the case mouth.  That same charge just poured into the case will result in another “X” column height.  Now I need to load a 457125 that I know needs to be seated .525” into the case in order for it to chamber properly.  Both case loads with different powder column heights will need to be compressed the same amount to achieve the proper bullet seating depth.  The drop tubed case will obviously need less compression than the case with powder just poured in.  In my mind saying a load needs “X” amount of compression is meaningless since the only measurement that matters is column height below case mouth to achieve the proper bullet seating depth.  Or am I missing something here.  

Charlie

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Tom Acheson posted this 23 September 2009

Guys,

I'm really new to the BPCR game also and this compression dimension has always been a bit of a mystery. The guys writing about this are (I think) making an assumption about where this dimension is being taken. They assume you are entering the powder into the case through a drop tube and are measuring from the case mouth downwards into the case to the top of the powder/wad column before nad then after compressing the powder.

Ignoring the obsessing over compaction depth, from what I can tell there are two key considerations”¦the cartridge overall length (COAL) that works best for your rifle AND not allowing any gap between the bullet base and powder. (On that point I won't roll the dice on an expensive rifle by experimenting.)  So if we know our COAL, then the only dimension we care about is how far into the case does the bullet extend? That dimension is where our powder/wad column stops. The more powder you put in, the more you compress it to maintain that dimensional relationship. The dimensional value of that compression seems to be a non-factor assuming youhave found the powder charge that works best for you. All we really care about is knowing that some brands/grades of powder give different performance results with different amounts of compression. It really says that it comes down to the volumetric differences of the various charge weights. Being squished down to conform to a fixed volume zone in the case just allows us to maintain our critical bullet/case engagement dimension.

I don't size the case after firing. I have a custom made BACO (Buffalo Arms) case mouth expander that modifies the case just enough to let me insert a bullet by hand where it comes to rest on top of the wad above the powder. Then I run the load through a Lyman taper crimp die just enough so the bullet stays put. You can rotate the bullet while it's in the case but you can't pull it out or move it up and down, even slightly.

About the newest Black Powder Cartridge News and the article on compression... I have to be missing something. It appears that the variations in compression depth were achieved by pushing the bullet farther into the case for each successive increase in compression depth. OK but why then do we need to report on the group size? The COAL varies with each incremental load combination which influences accuracy. What did I miss?

 

Tom

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canalupo posted this 23 September 2009

I am in a weird train of thought on this compression question. I do not shoot black powder cartridge but I shoot muzzle loader. I have found that the important factor in both accuracy and safety is to make sure the powder is compressed enough to force all the air out of the powder load and the bullet is fully seated. In an accuracy load If I have excess powder exit the barrel on firing I reduce the load simple as that. A hunting load is a little more complicated but not much. I expect some excess powder with the load because I am trying to gain some power.

My thoughts on bullet seating is to make sure there is no air space. To be honest I don't have a clue how to eliminate air space in a cartridge. I imagine it is a personal choice rather than a rule set in stone.

My thoughts only. I am rarely right on anything, so my wife tells me.

Bob D

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Tom Acheson posted this 23 September 2009

Bob,

The readings I've seen on the “gap” subject claim that if too much space is left between the base of the bullet and the top of the wad (most BPCR shooters use some kind of a wad, thickness and material varies) that “barrel ringing” will happen. You are correct we cannot remove or displace all of the “air” no matter how tight we squish things together. With our modern smokless loads, the air space concern seems to be a non factor.

 

Tom

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canalupo posted this 23 September 2009

Tom

I believe there is very little problems with air in smokeless powder because it is a propellant. Where as black powder is an explosive. Smokeless powder is designed to burn as it exits the barrel in a controlled stream. Black powder goes boom if there is too much excess airspace. 

I also have read that it is a myth that you could fill a muzzle loader barrel with black powder and it won't cause dangerous pressures. I actually met an idiot that tried it and blew his rifle in to many small parts.

I won't be trying that anytime soon.

Bob D

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beltfed posted this 24 September 2009

People,

The issue with air space in a BPCR cartridge is to NOT have air space between the wad and the bullet.  It is considered that when the ctg fires, in that instance, the wad gets moving and then when it hits the bullet, its like a bore obstruction at that moment with a resultant pressure spike and the result may be a ringging of the barrel at that point.

There should be no problem with ringing if the wad is against the base of the bullet and there is some air space between the wad and the powder column, which, of course will level itself against the wad when the rifle  is loaded and horizontal.

Anyways, it is indeed important to accuracy with BP to have 100% or greater(compresssed) loading density. 

beltfed/arnie

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beltfed posted this 24 September 2009

Oh, BTW,

As has been stated, Many BPCR people, including myself have found best accuracy with weaker primers, such as the Fed 150 LP primer, including paper wads in the primer pocket or inside the base of the case over the flash hole. In my loads I am achieving S.D.s in the low single digits.

Only place i  still use rifle primers in BPCR is in 45-70 loads for my Trapdoor Spfld, since it has such a heavy hit from the firing pin and we must be concerned about pierced primers. 

beltfed/arnie

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JetMech posted this 24 September 2009

beltfed wrote: There should be no problem with ringing if the wad is against the base of the bullet and there is some air space between the wad and the powder column, which, of course will level itself against the wad when the rifle  is loaded and horizontal.

Anyways, it is indeed important to accuracy with BP to have 100% or greater(compresssed) loading density. 

beltfed/arnie You might be right, and then you might not. Airspace between the powder and the wad caused 48 case splits on my first attempt at BP shooting, I believe. I had followed the conventional wisdom and loaded 50 rounds of 45-70 for my Browning BPCR. Loads were Winchester case , primers were Federal 215M, powder Goex 2X drop-tubed, charge weight around 58gns, if I remember correctly. This was measured and calculated to give me around .020 compression when I seated a .030 wad under a Lyman 525gn Postell. Off to the range I went. 30 miles, mostly highway until the last 2 miles, which were washboard gravel. 50 rounds went down range, each case carefully inspected (I thought). Groups were ho-hum at best, but then I was more concerned with bench technique, blow-tube, etc. When I got home and cleaned everything, 48 cases were split, circumferentially, 10-50%, right where the base of the bullet or wad were seated. Not quite sure what was going on, I loaded 50 new cases, 10 each the starting load and upping the charge 2gn for each successive 10 rounds. All rounds, after loading, were inspected and shaken a little to see if I could here if there was any air space. Everything seemed fine. Next week, off to the range I went. When I got there, I checked every round again and low and behold, the 58 gn rounds now had airspace. Assuming the rough travel had caused the powder to break up slighly and settle, I took them home and, using a collet puller, pulled the bullets. Shaking the round, I could still here powder rattling around under the wad. The rifle was fine, no chamber ringing and after upping the powder charge, I have not had any problem. Go figure. The only conclusion I could come up with was airspace between the charge and wad. The only other way a problem could be caused would be the magnum primer starting the bullet forward until it contacted the rifling, before the main charge was fully ignited, but the location of the splits indicated the bullet had not moved when the case split.

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beltfed posted this 24 September 2009

Dollar Bill,

I will probably never use Magnum primers for BP

beltfed/arnie

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Dead Tree posted this 27 September 2009

Thank you for the responses to my post. As a newby your information is very much appreciated.

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Dale53 posted this 28 September 2009

chuebner; Sorry for missing your question. I have learned over the years that my rifle responded better to just seating the bullet into the lead.

That establishes the location of the base of the bullet. All compression is measured from there. The first load tried is with “0” compression. I load ten cases. The next load I add two grains more powder (the powder is compressed by two grains). I continue this until I get groups that start to open. Then I fine tune by one grain steps either side.

I use a .060” LDPE wad under the bullet. The compression is by means of a compression die. My tests showed me that I got NO difference in group sizes by the use of a drop tube, so I eliminated that step. I just dropped the powder from the powder measure, inserted the wad and compressed the load. After I determined my best results (from actual bench rest tests)I then measured both the quantity of powder and the depth of compression (easy to measure from the case mouth to the seated, compressed wad after this is determined). However, and I consider this important, when I state it is compressed “so much” I am stating the amount measured from the powder level with the wad inserted before it is compressed to the position after it is compressed.

I hope this is understandable...

Dale53

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