Powder Column Drag

[Don in PA]

Hoppy
I don't know if these causes apply to you.
Two things that I have read about that can cause this are:
1 To tight a chamber
2 using a wire brush to clean brass, especially if the brush is used in a drill, seem to make scratch inside the case for the powder column to catch on.
HTH
Don

[Hot Foot II]

Hi Don,

Thanks for the response,... I've been out of town all weekend and away from the computer so this is why my thanks for your input is late.

I agree with your points.  I think in the subject rifle (Argentine RBlk) there is plenty of clearance in the neck area as full diameter bullets will drop right thru the neck of fired cases.

Using a brush in a drill could also create a rough surface for the powder column to drag on.  The bore brush I have been using is bronze so I think I am alright as far as that goes.

I think in a bottleneck (with bp) there is much more going on with the powder column as it gets compacted and then has to try to squeeze its way thru the neck (this point was presented to me in a previous discussion on another board some time ago).  I have now switched to using only 1F powders to give the whole powder column mass more room (airspace between the granules) to hopefully lessen some of the compaction stresses and along with that hopefully reduce internal drag.   Minimum compaction of the powder charge is now part of the loading procedure... about .020".

The whole .43 Spanish project is on the back burner as I get ready for some upcoming matches where I will be shooting .45-70.  I will post more as things develop in the future.  I am also going to set aside a few unfired .43 cases and shoot them only with smokeless, most likely Accurate 5744 to see if I have case stretching problems where there is no powder column compaction factor present.

Thanks again for the ideas.

Hoppy

[crashresidue]

Cheers guys,

OK - so I'm slow!  How do I know if I have "powder column drag?

Is there somthing that I should look for?

I DO use a brass brush to clean the inside of my brass.

Gentle winds,cr

[Don in PA]

Crashresidue
It's when. on firing, a portion of the powder compacts and delays burning It expands, grips the case and drags on the case walls. This can cause to case to streach excessively or break. A couple of reasons for this to happen are a tight chamber or scratches on the inside of the case. If your cases are not streaching or breaking you have nothing to worry about
Don

[Sharpsman]

My old tired arse! I've heard it all now!

I've used bronze brushes for years to clean cases and shot groups that wouldn't do to tell here!

Find another excuse!

[crashresidue]

Cheers guys,

I'd ask you to go back in these posts and look at my "Brass Creep" post and tell me if this is something that I've got.

Also, I've been breaking "old" brass - about an inch from the base.  Is this a sympton?  Now, this brass is over 25 years old - so is it the "powder column drag" or is it only "old brass"?  Also an "old post".

Any answers are appreciated.

Gentle winds,
cr

[Don in PA]

I recall reading a artical in the SSE by Lee Shaver. He was having a problem with case seperation in a 45-70 RB if I remember correctly. The  only thing he could find that caused the trouble was powder column drag. That is the powder was compacting and draging on the case. He was using a heavy load. He solved the problem by using a duplex load ... 15% fffg over the balance of the load ffg. He also felt that using a wire brush could score the inside of the cases and contripute to the problem. I was only passing along the info guys ... take it of leave it.
Don

PS the artical is in the March 2002 issue of "Single Shot Exchange"
title "Case Stretching and Separation" by Lee Shaver.

[Sharpsman]

Don in PA

I don't think a brass brush or one wrapped with fine steel wool on a rotary drill will cause this case stretch! What I do think will cause case stretch more than anything else....is an improperly adjusted resize die....and the use of hard plastic wads whose sides will not compress nearly as much as a Walters type wad when the wad is compressed against the powder column!

[Timberlake]

Don in PA,

I experienced case separations some years back using heavy loads in my RB.  Back then (30yrs+) I wasn't cleaning cases, inside or out.  The rifle was shooting well........well as far as accuracy goes, but I had more than a few brass liners in the barrel.  Many of the cases that did not separate did show some bending.  After looking closely at the base portion of the separated cases, right where the separation occured, on top, in line with the sights, it was apparent that the action was springing.  I rebuilt the action and got the headspace back to .002".  (it was at .0010")  Same accurate load and no more separations.  I'm still pretty lax at case hygiene, but I ain't lost a one since in the roller.  RB owners, check your headspace.

TL

[Hot Foot II]

Timberlake,

What caliber/chambering is the rolling block you had trouble with?

Was/is it a bottleneck of some sort?

Hoppy

[Timberlake]

Hoppy,

The action is a number 5 Rolling Block.  The caliber was 45/70.  I was using 82 grains of 3f DuPont compressed with a Lyman 457125.  All separations occured just ahead of the case head.

George

[Don in PA]

All
Using a wire brush to clean brass doesn't cause case seperation. But, it can contripute to the problem. Other than bad brass or a faulty chamber, the author of the article felt that the cause for case seperation or streching was ... 1- low friction between the case and chamber wall. This could be caused be moisture or lube in the chamber. And ... 2-  high friction inside the case between the bullet, wad and powder column and the case sides. The increased friction could be cause by a wad that's to big, oversize bullet. or powder column the expands to much before getting out of the chamber. Among other things any scratches cause by a brass brush could contribure to the increasing the firction. Especially if you use the brush on a drill, the scratched will then running be around the case.
In his case he solved the problem by reducing the size of the wad and using a duplex load.  He also felt the there should be no case streching with black powder. From my experence I have found this to be true.

I have stopped using a brass brush. And have not found my brass to be any dirter, I now use a nylon brush. In fact, I think getting the brass into soap and water asap after firing contributes more to cleaning the brass then anything.
Don