Powder Compression Strangeness????

[oldracer]

Yesterday I was loading up some nice shiny 45-70 cases that were a mixed lot of various manufacturers. The load had 68 gn of Goex FFG, through a 24 inch drop tube, compressed with a milk carton wad on top of the powder. I use a home made compression die, made from an extra expander die and the amount of compression is just enough to have the Lee 500gr pointed bullet seat 0.002 inches off the lands.

Here is the weirdness, every now and then on the the loads would take much more pressure on the RCBS ram arm to seat the powder! I look at every load just before the compression to make sure it has close to the same volume of powder and they ALL were. The powder was from a new can and when pouring it into the hopper it looked smooth and even with no chunks or large pieces. Each one that was harder to compress, I set the load aside and was surprised to find that ALL brands of cases were in the mix so I don't think it is a brass issue? All cases were fire formed and had the mouth expanded slightly so as to scrape the chamber when inserting as per Doug Knoell's suggestion which seemed to tighten the groups by about 20%!

So my question is this, has anyone else experienced this and do you know what caused it?

[chuebner]

Basically the issue is with the interior volume of the differing cases. I also noted what you did when reloading Winchester, R-P and Starline cases. Winchester has the greatest interior volume and R-P the least so the Winchester cases will have a lower powder column in the case as compared to an R-P case. This difference is noted when compressing the load. Case wall thickness is the culprit. I segregate my brass according to rifle, Winchester for the trapdoor, R-P for the rolling block and Starline for the Sharps.

charlie

[oldracer]

The interior volume was my first thought also. But this happened to a mixture of the cases, not just one brand? I also measured the height of the powder before compression and it was the same as I have a "tamping stick" with lines on it for each volume of powder I have tried since I am not using a weight measurement right now?

An additional item, when I compress the powder, before putting in the news wad and bullet, I look in the case to see if anything has come up past the wad (milk carton) and so far nothing has?

[TXGunNut]

Have any of the cases been resized? When I quit resizing my 45-90 I had to up the charge about 1-2 grs to take up the extra space.

[oldracer]

No resizing has been done since I started shooting, just the fire formed and belled case mouth. The pressure to bell the case mouth is barely perceivable on the press when moving the arm so I don't believe there is any case distortion taking place?

Any other ideas please?

[RMulhern]

:groner::killingpc:not listening::dung_hits_fan:

[oldracer]

Well, I don't know if I would go that far??!! As I noted when I started the black powder cartridge shooting, three seems to be some fairly high %%%% of voodoo or black magic involved here. This might be one of those items since accuracy does not seem to be affected as neither does velocity?!

[RMulhern]

As has already been brought out.....case interior dimensions are different brand to brand...and even with the same brand possibly from Lot to Lot! Cases SHOULD BE SQUEAKY AZZED CLEAN; best way is by ceramic media and tumbling!! I also run a .45 caliber brass cleaning brush attached to a drill down through all of mine before charging! I also put a little powdered graphite inside the case using a shoe dauber, invert the case and tap out any remaining. Just the slightest film of the graphite on the case walls eases compression pressure a great degree!!

[oldracer]

Well, my cases are clean, both inside and out as I do check the interior after I use my RCBS prep machine and put a slight bevel on the opening edges, clean the primer pocket and use a brass brush inside each one. As noted in other posts I do tumble clean with ceramic ball media after decapping and soaking in water/Dawn. The reason I check each case was one shot had several balls stuck at the bottom of the shell case and when shot they made a funny colored addition to the smoke cloud?

One thing I have not tried is the addition of the graphite and I actually have some (forget why I bought it) that I can try next time I load some. That will probably be next weekend after shooting some.

As I noted in the first post, the brand of cases was mixed and I counted them as follows: 3 Starline, 2 R-P and 2 Winchester so they were mixed??!! That is why I was thinking about this as an anomaly. The thing I have not tried is to get a pipette and measure the actual volume of each case with liquid, by sealing off the primer hole and I was hoping that would not be necessary.

[shovel80]

I'm wondering...if you are measuring powder by volume..with a dipper? Maybe some of the time the dipper is run harder though the powder to pick it up and sometime more lightly?

Terry

[TXGunNut]

Just for grins (and consistency!) use cases of the same lot, same manufacturer. Same lot may not be necessary but would certainly be a good idea. I do this for smokeless and BP rifles, even 45 Colt.

[oldracer]

Good ideas and the cases I have are all from a large bag(s) at the local gun show at Delmar CA. Many were new and have been fired, some were once fired and all have been fired in my guns. That sort of eliminates the same batch idea but is good to keep in the back of my mind.

I don't use a dipper but get the powder from the drop tube and powder measure and cycle it several times and them measure against a known muzzle loader powder measure by volume. I also visually check to level in the case for each through and they are all looking the same before I pop in the carton wad.

[TXGunNut]

At the very least sort by headstamps and weight (+/- 1-2grs). Just realized you may not have a scale. Hmmm...45-70 cases vary widely. If you want precision loads either invest in new brass or a scale, or both. Accuracy requires consistency, random cases will not deliver either.

[ss40_70]

an easy way to sort your cases by volume with out a scale .. with the fired primer still in the case wash and clean the case as normal ... then find something such as a large syringe that you can refill with a consistant volume of water every time .... then add the same amount of water to each case .. and sort by water level in the cases

[oldgeezershooter]

I check all of my cases with water volume and sort accordingly, sometimes the same brand will vary.

[Boz330]

With out a scale I think you are wasting your time. The measure can throw pretty accurate charges, MOST of the time, but occasionally it will bridge and give you a difference. If you are getting vertical stringing that would indicate that there are discrepancies and these may not show up much until you get past 200yd. One single lot of cases would also help.

Bob

[semtav]

One thing I started doing, is after drop tubing and putting the wad on lightly, is measuring the depth from the top of the case. there is usually at least .050 difference in a lot of 50. This is with weighed charges of same batch same manuf shells.

Then I sort them by depth. I haven't done any DanT type testing to see if there is a difference, but the first time i did that , I won the match, so I'm biased toward it.

you might also try using your comp die to seat the wad by hand each time, and you will be able to tell if any of the cases are tight on the die.

[Don McDowell]

Agree with Boz, if you're not weighing your charges you'll get an extra dollop of powder in a case every now and then, just like you might get shorted a grain or so.
You might want to dump the "hard" to compress charges in a scale pan to see what you got in there.

[Gunlaker]

Even whe using cases of the same brand there can be volume differences. This often happens with "fireformed" cases that have only been shot once as well. It seems that in order to truly conform to the chamber dimensions you need to shoot 'em a couple of times.

There really is no voodoo with BP shooting. It's just a steeper learning curve than smokeless with hard bullets. Hard bullets and smokeless powder shooting are quite forgiving when compared to shooting these rifles. There are a lot of details that really matter. The more you pay attention to them the better the results. Consistency in everything that is under your control...

Btw old racer, what did you race? My dad, brother and I did a fair bit of drag racing 15-20 years ago.

Chris.

[oldracer]

Thanks for the discussion everyone. I do have a Cabelas scale and so far did not weigh the cases. I tried weighing the powder charges when working on the different loads when I bought my 1st rifle. It seemed to like the 68 Goex FFG load best and after switching to volume exclusively this past spring 68 by volume seems to give best accuracy, at least out to 300 yds which is as far as my range goes.

I did note earlier that I am considering a volume check of the cases and will probably try that with this next bunch I shoot. I would be more inclined to use that as a standard instead of weight since the alloy of the cases and other factors can easily effect the weight of each case. That means I'll not decap the cases until I get home but that should not cause any issues I think. They soak in water/Dawn so the powder residue will be pretty much gone.

As I noted earlier, I use the powder dispenser and a drop tube and no scoop and I eye ball the level of powder in the case for each load to make sure none are too full or too low due to sticking powder in the charger.

I used to race everything, from dirt track stock cars in the 60's to road race motorcycles in the 60s and 70s to bicycles/triathalons in the 80s to vintage sports cars from the mid 90s until a couple of years ago when my arthritis got so bad I can't get around well without pain meds and driving 140MPH plus in a pack of 30 or more cars is not safe any longer. It pained me to sell the Porsche 914-6 but it is in a museum over seas resting now! Attached is a picture at the last race I did at Willow Springs Raceway in CA.

[montana_charlie]

New brass from the same lot number can still vary in weight.

I bought 250 new Bell 45/90 cases and weighed them.

Most (150) had basically the same weight.
33 cases were more than a half grain light, so they got sequestered into a 'set' for load development.
67 cases weighed more than a half grain heavy, so they became my everyday shooting brass.

The 150 matched cases are to be used for ammunition to be fired in competition ... if I ever get satisfied with load development.

Rarely, but occasionally, after preparing a set of loads to fire in the next shooting session, I will weigh a few completed cartridges.
It makes me think my ammo is carefully and consistently built when those loaded rounds all weigh the same.

If I were going to check the water capacity of fired cases, I would deprime ... get cases thoroughly clean ... dry ... and put the old primers back in for the test.

CM

[Lead pot]

I dont like using water because of the difference that gets left behind from case to case.
I use a ball powder like H380 or salt, both are uniform in size.

[bigted]

I dont like using water because of the difference that gets left behind from case to case.
I use a ball powder like H380 or salt, both are uniform in size.

should be using a cc tube designed for cc'ing engine cubes. you refill the glass tube with every pour and de-duct the amount with the cc marks on the glass...always use a dry case as with the cylinder of an engine...you can get very close measurements thusly from hole to hole.......done a lot of this in building drag bikes outta old thumpers.

do the same with your syringe......just measure what is gone from the same filled state instead of trying to measure the amount of water in the case.

fill the syringe to the same mark every time and note how much water is gone when the case is filled to the same point every time. the case should fill to make a small bubble of water over the top of the mouth and this is going to be the same for every case regardless of the whole amount inside the case. this "bubble" on top of the case is critical and will prolly take a couple of filled cases to get a 'feel' for when to stop dribbling in water....oh and also need to have cases in a stable mount with every fill as well.

just an ol bike builders 2 cents woth.