compression and bullet seating

[Black River Johnny]

Being a bp cartridge newbie I have a question on compression, Why do some loads say compressed or not? I mean are not all loads compressed? If I fill a case  to the top why can't I just use the bullet to compress the powder? how much compression should a load have and if you compress the powder you still need to seat the bullet and not have any air gap, doesnt that change the compressed load? also just looking for general answers on compressing.
Thanks

[Paladin UK]

This might help ya......

http://www.cascity.com/forumhall/index.php/topic,18257.0.html

Paladin (What lurvs the Holy Black) UK

[Ranch 13]

 Compression is probably an over used and confusing term. Basically you'll compress the powder as much as you need to to fully seat the bullet. What ever number you decide to assign as compression amount will likely impress the snot out of somebody.
Yes you can compress the powder while seating the bullet and wad.
The biggest thing you need to watch out for is not bulging the case when compressing extra large amounts of powder or finer grained powders. Using an excessively full case of 3f will bulge a case quicker than 2f, due to the smaller grains fitting together better in the first place.

[Deadguy]

I always fill my BP cases to the top and then compress the powder fully, then seat wads and bullet on top.  Works fine for me!

[Black River Johnny]

thanks guys for clarifing that for me , that helps alot

[Fox Creek Kid]

Compression is not a simple topic due to the mere fact that some powders like it & some don't. As a rule GOEX does & Swiss does not per my experiences and many others. For CAS shooting it is not that critical. For BP long range it can be very critical. Again depending on the gun & the load. The general rule of thumb for pistol type cartridges is that when the bullet is seated it will have compressed the the powder approx. 1/8". That rule of thumb has worked for me for countless years with pistol cartridges. If you compress too much you will have crushed the powder grains thereby turning FFg into FFFg or FFFg into FFFFg which gives erratic burn rates as well as pressures.

[Driftwood Johnson]

Being a bp cartridge newbie I have a question on compression, Why do some loads say compressed or not? I mean are not all loads compressed? If I fill a case  to the top why can't I just use the bullet to compress the powder? how much compression should a load have and if you compress the powder you still need to seat the bullet and not have any air gap, doesnt that change the compressed load? also just looking for general answers on compressing.

Howdy

For many applications real Black Powder is pretty forgiving as far as how much compression is applied.

I have always found that for CAS cartridges, a compression of around 1/16"-1/8" works fine. Yes, I compress the powder with the bullet as I seat and crimp it. It is not too critical exactly how much compression. Some of the original specifications for Black Powder cartridges like 45 Colt and 44-40 listed the powder charge as 40 grains. Modern cases are more heavily built than some of the 19th Century cases and do not have as much interior capacity as the old cases. So it is difficult to actually fit 40 grains of powder into most cases without a lot of compression, more than 1/8". Some shooters have tried mashing the powder down a lot in order to stuff 40 grains of powder into their cases. It can be done, but there isn't much point, the amount of powder that fits into a modern case with 1/16"-1/8" of compression will do the job just fine and any more powder is just wasteful. Black Powder actually varies in weight from manufacturer to manufacturer. I load my BP by volume. The amount of BP that gives me the compression I want with 45 Colt or 44-40 is as little as 33 grains with one brand, as much as 37 grains with another brand. The ballistics of cartridges made with these amounts of powder will obviously vary, but for CAS purposes at close targets, it is good enough.

When I load shotgun shells with Black Powder I compress the powder after I seat a cardboard over powder wad. I simply lean on the wad with a piece of 5/8" dowel until I hear a slight crunch. Compressing the powder in this fashion does not have the mechanical advantage of using a loading press, so the powder is very lightly compressed. I have never measured it, but I'll bet it is less than 1/16". For my purposes in a shotgun shell, it is enough compression and the loads work fine.

Precision long range shooting is a different thing entirely. There you want absolute consistancy. You also do not want to be damaging or mashing the bottom of the bullet out of shape at all, so most serious long range shooters of cartridges like 45-70 and the like never compress the powder with the bullet, fearing that any distortion of the base of the bullet will damage accuracy. Many long range shooters compress the powder with a special compression die, then seat a wad and finally the bullet with no more compression at all. This takes very careful setting of the dies so that the bottom of the bullet just kisses the wad without leaving any air space at all.

[Wills Point Pete]

 I shoot soft-cast bullets and so I do not compress my powder with the bullet. I compress the pistol cartridge rifle and revolver rounds with a homemade compression die and the shotgun rounds with a brass rod and muscle. It takes almost no effort to deform a pure lead or 20-1 bullet.  Being retired I don't mind that I load slowly.
I also use a drop tube for all my BP ammo, again I am in no hurry.

[Rusty Spurless]

To compress or not to compress... That is the question 

In broad terms IMO it depends on the situation. Compressing BP a little is a good thing. It encourages uniform & cleaner burning. Excessive compression has some arguments attached but I am inclined to agree with FCK on it.

For my own purposes I almost always compress. The only exception being a pair of Uberti 73's that will only shoot to POA with 200gr bullets. Those 200 grainers & my usual load of 30gr of FFFg just dont quite touch in the the case. I believe the base of the bullet just kisses but does not compress the powder.
Only real difference I see is in cleaning. Seems like those barrels have more crude in them.
All that said, this is for loads shot at CAS ranges

On the other side of the coin is when I load for my Sharps. Then I am using ever bit of mojo I can scrounge up. Drop tubes, over powder cards, vegetable wads & uniform compression are the rule then.

[Steel Horse Bailey]

I would have to agree with everything "said" here.  I go one step further.  I lightly tap the case after the powder is in the case to settle the powder down.  (Much the same result as using a drop tube - but I do the same with my 45-70 rounds even when I DO use a drop tube.)  THEN I compress 1/16" to 1/8".  To be fair, I also only use BP, (usually Goex 2f,3f, or Cartridge) no subs - nor can I afford Swiss (also real BP).  As Fox Creek mentioned, different powders like different compression ... like what Swiss recommends.  I think Hodgdon 777 instructions also specify not to compress, rather you simply make sure there's no air gap between the bottom of the bullet and the top of the powder level.

 
Wills Point Pete said in another post that the minimum compression is when the bullet touches the powder.  Yep.  You can do more ... but you take a chance if you do less.  A heavy charge of black powder and a sizable airspace (like what is often done with smokeyless powders) CAN   do damage to the gun.   (Chamber rings, excessive headspace, metal failure, etc.)  You could lose fingers or eyes ... or worse.
   

[Grapeshot]

I picked up a book by a gentleman named Wolf.  He was loading .45/70 Cartridges to Mil Spec circa 1873 to 1885.  In this book he stated that he measured each charge with a scale to 70 grains of Goex FFg and used a compression die to push the powder down into the case to be able to seat the 500 grain M1881 rifle bullet.

He also opened up the flash holes to 3/32nds of an inch and used Winchester or Federal Magnum Large Rifle Primers to light this load off.

He also used weighed Goex FFg charges of 40 grains in a .45 Colt case using a compression die to push the powder down far enough to load a 250 grain bullet.  These case were also modified with the larger flash hole and magnum large pistol primers were used.

I have done this with the .45 Colt cases.  You will never forget the experience as the gun rotates in your hand and the concussion flattens everything around you when you touch this load off.