procedure for measuring case volume

[Trickymissfit]

I tried spent primers but I find this easier. I turned a Delrin plug with a decent base so inserting and removing the plug is just a twist of the fingers. The top of the plug is slightly cone shaped so it always bottoms out on the edges of the flash hole.

You should have this little ditty copywrited!!!
gary

 

[g0rd0]

here is the Homer Prowley method
1. useing brass fired in your rifle (10 0f them), neck sise, deprime, trim, and clean
2. put the bullet that you will use in the case mouth and chamber (so that the rifleing seats the bullet)
3. weigh all 10 of them recording each, add the total weight and divide by 10 giveing your average empty weight
4. now useing a syringe fill them up with water through the flash hole, then useing a q tip wipe out the water in the primer pocket and weigh all 10 again then add the total divide by 10 to get your average weight full
5. subtract your average empty from your average full and that is your case volume in grains of water

after you pull the bullets and empty the water you can give them a bath in pure rubbing alcohol to remove any left over water drops

PS when you chamber the case and bullet in step 2 you can put a cleaning rod down the bore to find your true barrel length for that perticular bullet do this by marking the rod at the muzzle then add the length of the preloaded bullet (the projectile not the oal of the loaded cartage) to the mark on the rod this will give you a true barel lenght for the load. We do this to get the expansion ratio of your rifle's load (case cap. X cal X Barrel length = expantion ratio)

 

[rscott5028]

here is the Homer Prowley method
1. useing brass fired in your rifle (10 0f them), neck sise, deprime, trim, and clean
2. put the bullet that you will use in the case mouth and chamber (so that the rifleing seats the bullet)
3. weigh all 10 of them recording each, add the total weight and divide by 10 giveing your average empty weight
4. now useing a syringe fill them up with water through the flash hole, then useing a q tip wipe out the water in the primer pocket and weigh all 10 again then add the total divide by 10 to get your average weight full
5. subtract your average empty from your average full and that is your case volume in grains of water

after you pull the bullets and empty the water you can give them a bath in pure rubbing alcohol to remove any left over water drops

PS when you chamber the case and bullet in step 2 you can put a cleaning rod down the bore to find your true barrel length for that perticular bullet do this by marking the rod at the muzzle then add the length of the preloaded bullet (the projectile not the oal of the loaded cartage) to the mark on the rod this will give you a true barel lenght for the load. We do this to get the expansion ratio of your rifle's load (case cap. X cal X Barrel length = expantion ratio)

Notwithstanding adjustments for temperature and pressure, that seems like an ok way to get an average case volume.

At this time, I'm more interested in the relative comparison in order to form a very consistent batch.

Thanks!
Richard

 

[BountyHunter]

regular water will form small bubbles and cling to the case walls at the shoulder. Soap will not always work. Sometimes even tapping them will not get them to release.

Use 91% rubbing alcohol and that ends the air bubble issue once and for all. Plastic bottle at any drug store sells for under $2 so super easy to get and cheap.

I just did an experiment with 100 new 25-06 cases and less than 1% difference in case capacity on high end vs low end of weight extremes as compared to volume. Most weight variance issues are not in the walls, they are in the bases.

I have run this scenario multiple times with multiple calibers with a lab scale and Oehler 33 with 4 ft and 8 ft spacing. That is less than 1% variance on the chrono which is better than anything but a commerical Oehler 43.

Unless you have a lab scale that accurately measures down to the .02 minimum, I fail to see any gains over sorting by weight to 1 grain or at least 1%. The margin of scale error for the RCBS chargemaster and Dillon Terminator is way outside of those measurement accuracies anyway. Lot of wasted effort for scales that cannot measure accurately enough to determine anything.

 

[Mikecr]

I just did an experiment with 100 new 25-06 cases and less than 1% difference in case capacity on high end vs low end of weight extremes as compared to volume. Most weight variance issues are not in the walls, they are in the bases.

Would you clarify your contention here?
Seems mixed amid 'weight' -vs- 'volume'.

 

[rscott5028]

BountyHunter,

I checked my fisrt batch of 50 weighing them to the nearest .02 grains.

I recorded the weights and marked the cases with sharpie.

I don't think I had any bubble issues.

However, I should win some kind of prize for stupidity.

Not wanting water anywhere near my dies, I rinsed the cases in alcohol to help dry out the water so that I could decap the upside down primers.

Naturally, the alcohol removed the sharpie.

So, I'm left with a pile of shiny cases and a batch of data that I can use to figure mean weight, volume, weight to volume ratio, etc. But, no chance of sorting until I rerun the procedure.

bummer!

-- richard

 

[sp6x6]

Having any fun yet

 

[Trickymissfit]

regular water will form small bubbles and cling to the case walls at the shoulder. Soap will not always work. Sometimes even tapping them will not get them to release.

Use 91% rubbing alcohol and that ends the air bubble issue once and for all. Plastic bottle at any drug store sells for under $2 so super easy to get and cheap.

I just did an experiment with 100 new 25-06 cases and less than 1% difference in case capacity on high end vs low end of weight extremes as compared to volume. Most weight variance issues are not in the walls, they are in the bases.

I have run this scenario multiple times with multiple calibers with a lab scale and Oehler 33 with 4 ft and 8 ft spacing. That is less than 1% variance on the chrono which is better than anything but a commerical Oehler 43.

Unless you have a lab scale that accurately measures down to the .02 minimum, I fail to see any gains over sorting by weight to 1 grain or at least 1%. The margin of scale error for the RCBS chargemaster and Dillon Terminator is way outside of those measurement accuracies anyway. Lot of wasted effort for scales that cannot measure accurately enough to determine anything.

when I do sort cases (and I do), I usually work with a two grain window (+/- 1 grain). I seldom measure volume, as it's just a pain in the rear. Photoflow will make water spread like nothing I've ever seen. Get zero bubles out of a hand sprayer if it matters much. Like I said I use the Photoflow for a completely different application, and along with alcohol and the right kind of soap I get no suds as well. In my cleaning machine, bubbles would drive me nuts and kill the pump. I use nothing but 93% alcohol, and for your ap it sould work very well. The 70% stuff will attract water if that matters. Either way just let them set out in the air for a day or so to completely dry
gary

 

[Bart B]

Gary Trickymissfit's comments on my Hart barrels:

I think he uses 17PH-4 rearc melt stainless steel, but where he gets it from is another story. (Refering to the Hart in AL). Seems like I read an interview with him, and he said that.

Those Hart barrels I referred to were not from AL; they were made in LaFayette, NY. Stainless 316 if I remember correctly, and it came from a steel mill near Chicago, IL. From the mid '60's to late 90's, the best Hart 30 caliber barrels were button rifled and lapped by Al Hauser, a former USMC riflesmith at Quantico, VA (again, as I remember...geesh, that's a long time ago). Most of the high power match rifle records were set with them as well as the vast majority of big matches won with them. Their top users switched to Kreiger barrels after Al Hauser's retirement from Hart; they just didn't make 'em as good afterwords. And John Kreiger's barrels did plenty good enough.

 

[Trickymissfit]

Gary Trickymissfit's comments on my Hart barrels: Those Hart barrels I referred to were not from AL; they were made in LaFayette, NY. Stainless 316 if I remember correctly, and it came from a steel mill near Chicago, IL. From the mid '60's to late 90's, the best Hart 30 caliber barrels were button rifled and lapped by Al Hauser, a former USMC riflesmith at Quantico, VA (again, as I remember...geesh, that's a long time ago). Most of the high power match rifle records were set with them as well as the vast majority of big matches won with them. Their top users switched to Kreiger barrels after Al Hauser's retirement from Hart; they just didn't make 'em as good afterwords. And John Kreiger's barrels did plenty good enough.

small correction. The material would have been 416 stainless steel. 316 is what most stainless nuts and bolts are made out of, and not good barrel material at all. 17PH4 is a completely different alloy yet, and much harder to work with than 416. It's pretty tough stuff, and is what they made landing gear out of for ship board landings. Trying to place what steel mill that would have been near Chicago. Would have been in either East Chicago or Gary Indiana (all very close to Chicago). My guess is that it came out of Newcore a little south of there, and they did a lot of specialized alloys (known as a "mini mill") Alro is the big supplier in Indiana, and they don't use much from this area. Just kinda interesting as I've never ran accross a single supplier for SS steel within 350 miles of Indy. I would have bought steel from them had I known who they were.
gary

 

[rscott5028]

Here's the chart from the botched attempt.

The values were adjusted/exaggerated in order to get a better perspective of the relationship. The ascending line underneath is the sorted empty 6br case weights.

There is actually less variability in case weight than illustrated here since seating upside down primers has the effect of losing some of the anvils. So, I am about to start over and will be more precise in all respects.

Nonetheless, there appears to me to be some inverse relationship between case volume and case weight. That stands to reason because the exterior dimensions of the prepped, fired, partial neck sized cases are pretty uniform.

Still though, you can see that there are fluctuations.

-- richard

 

[rscott5028]

should've listed the stats above...

6br lapua brass... prepped, fired, partial neck sized
sample size = 50

H2O weght in grains to the nearest .02gr
38.91 mean
0.23 standard deviation
39.34 max
38.34 min
1.00 extreme spread

Also, I put about a capfull of Hornady sonic cleaning solution into a 1/2 cup of water that had been sitting for a few days and had no issues with bubbles.

-- richard

 

[rscott5028]

here's the 2nd iteration of same 50 cases...

This time I made a delrin plug as suggested by JRu rather than the upside
down primers.

The results are within about .02gr which is about what the scale claims. So, it seems to be repeatable.

H2O weght to the nearest .02gr
38.89=mean
0.25=s
38.22=min
39.28=max
1.06=range

 

[Trickymissfit]

I'm telling you that whoever it was that came up with that plug idea, should have it's design and use copywrited. Something like one of those "Swiss Turnning" machines would spit out five hundred of them in 24 hours without breaking a sweat. You'd have to use something like Delrin rod (alcohol won't bother it), and that's stuff's kinda pricey, but you'd could still make a nice profit at $10.
gary