Powder compression

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TAA
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Powder compression

Post by TAA »

As I read various posts, the subject of compressing powder is often seen.

When the amount of compression is noted, where is this measured?

A. You fill the case to the top and then compress the powder?

B. You pre-weigh the power and pour it into the case and the top of the powder column is where you take your starting dimension and then compress 0.XXX”?

C. You use a drop tube and the resultant top of that powder column in the case is the starting point that compression is measured from?

But maybe these gyrations are a non-factor and compression is compression?

Thanks!

Tom
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CaptnJack
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Re: Powder compression

Post by CaptnJack »

45-70 and my 45-110 I measure the powder, drop it through a drop tube (I have a 32" drop tube) into the case, Say 70 gr of OE for the 70. I put a .060 plastic wad on top compress it. I like .2000 and a real light crimp just to hold everything together. If I want to use a little more powder say 72gr. I have to compress it some to get the extra powder into the case then the wad. With the 70gr. OE it works out just right I can install the wad then compress. PP only.
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desert deuce
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Re: Powder compression

Post by desert deuce »

Compression is compression.

Compression...……..is the distance a column of powder residing inside a cartridge case is compressed inward.

Example given:

#1.- Drop tube 70 grains 3F Swiss in a 45-70 case

#2.- Place .025" card wad on top of powder column

#3.- Place bullet on top of card wad and measure cartridge over all length

#4.- Remove bullet, using powder compression die press column of powder deeper into case

#5.- Replace bullet and remeasure cartridge over all length

#6.- Subtract #5 from #3 to get compression depth of powder column
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Lumpy Grits
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Re: Powder compression

Post by Lumpy Grits »

The amount of compression depends on caliber, bullet type and powder maker.
Some powders like to be really compressed, as I have found with Goex.
Others like Swiss, run well with 1/8" or so.
G.
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Coltsmoke
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Re: Powder compression

Post by Coltsmoke »

Tom you want just enough powder with the wad you are going to use in the case to give you the over all length of the load that you want. Let's say that is 70 grs. drop tubed with a .060 wad sitting on top, with the bullet sitting on top of the wad and you have the over all length you want. That is "0" compression on the powder. If you go up to 72gr. of powder that will add around .040 to the powder column height in a 45-70 case, around .020 in height per grain of powder. So with the 72gr. charge you will have to compress that powder and wad down .040 to maintain the same over all length of the loaded round. Now you have a load with .040 of compression on the powder. If you are loading a .40 case you will gain more than .020 on the powder column height. As you add powder you will make the powder column taller and this will add more compression to maintain the same OAL.
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TAA
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Re: Powder compression

Post by TAA »

Thanks. That is a good explanation.

The chambering is 40 2 1/2 (40-70 SS) and the bullet is a Paul Jones Money with the front two bands smaller in diameter than the rest. I've been fooling around with 1, 2 or 3 poly wads. The OAL has the bullet just starting to engrave the rifling. Any longer and I'd need one of those "cheater cams" to close the action. I retired in Jan. but before I did I bought 25-pounds of Old E 1 1/2 so that's the powder I'll have to use. The current load is 68-grains, 1323 mv.

My main question was if you do not use a drop tube you'll apply more compression to get the top of the powder column and wad in the correct location to maintain the desired OAL. So if someone says their compression is 0.xxx" without knowing if they use a drop tube you really don't know the total compression....right?

Thanks for the help!

Tom
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Re: Powder compression

Post by sandhillcowboy1 »

TAA wrote: Sun Jun 30, 2019 7:27 am
My main question was if you do not use a drop tube you'll apply more compression to get the top of the powder column and wad in the correct location to maintain the desired OAL. So if someone says their compression is 0.xxx" without knowing if they use a drop tube you really don't know the total compression....right?

Thanks for the help!

Tom
Yup, compression is a relative thing :)

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Coltsmoke
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Re: Powder compression

Post by Coltsmoke »

The answer to you main question is yes. Without a drop tube, just dumping the powder in the case, it will stack up higher which will add more compression to achieve the same OAL. If someone says they have 0.xxx compression, all we can do is assume he knows how to measure compression regardless of how he put the powder in the case.
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martinibelgian
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Re: Powder compression

Post by martinibelgian »

Or in other words, compression is a result, not a goal... You usually achieve it by changing the powder volume.
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desert deuce
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Re: Powder compression

Post by desert deuce »

Or in other words, compression is a result, not a goal... You usually achieve it by changing the powder volume
To expand on MB's assertion a bit, because I have read enough of his posts to understand what he is saying, I think.

By intention the goal MB mentioned is improved, hopefully optimum, accuracy from the procedure of loading of ammunition.

The result is observed by the grouping of shots fired at the target at a prescribed distance. Here, smaller groups are better groups.

A common method of increasing compression without adding powder is adding wads to the wad stack.

Compression does affect accuracy. Adding powder may not improve at the target accuracy. There appears, in most rifles, a balance between the two.

The underlying object, though seldom mentioned and even less understood, is the development of a balanced load. Which in practice is the holy grail of black powder cartridge shooting. Alas, this forum IS NOT the place for that discussion.
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Coltsmoke
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Re: Powder compression

Post by Coltsmoke »

10 shots, one hole, that's all folks. Don't care what you call it, or how I get there.
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desert deuce
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Re: Powder compression

Post by desert deuce »

True, that would be optimum accuracy for that distance or any distance for that matter.

Best I have seen at 300 yards was 5 shots one ragged hole 45-90

Best I have seen at 600 yards was 4 shots in one inch ragged hole 40-60 Maynard.

Ever notice nobody talks about those worst targets ?
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Coltsmoke
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Re: Powder compression

Post by Coltsmoke »

Don't shoot loads that produce worst targets. :lol: I've been loading ammo all day inbetween company and working on an icemaker and posting on this forum during break times. I know where this lot of powder shoots as far as the compression range. Today I'm loading a new bullet and covered all the bases as far as powder charges and compression goes. Even loaded several half grain increments to cover all the bases with compression with this load and bullet. It will be interesting to see if this load shoots at the same level of compression. The load I'm comparing it to is a PP load, this load is a GG load with neck tension, totally different. One bullet setting in the bore, the other jammed into the rifling and squeezed by the brass.

I tried the PP load with 2 different brands of brass, both brands shot well. The powder charge was different in the two brands of brass, but the compression was the same on both loads. I don't know what this new GG bullet will do, compression may be different since it is jammed into the rifling. That is the great thing about our addiction, get bored with putting 10 shots in one hole :lol: just buy a different bullet mold. :P
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desert deuce
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Re: Powder compression

Post by desert deuce »

New Bullet Mould? Better yet get a new rifle. That will take things back a ways.
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Coltsmoke
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Re: Powder compression

Post by Coltsmoke »

Finished up testing the GG bullet and the winning load only had .028 compression on the powder charge. Big difference between it and the PP bullet. But it is a totally different ballgame.
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