View Full Version : Okay dog gone it
September 12, 2010, 07:54 AM
You know that every once in a while you come to a revelation in your life and it makes you feel so dumb?
I use the CVA 1400 flask. I have two of them, one with a 30 grain spout and the other has a 15 grain spout.
Last week I took the CED M2 Chronograph for the first time and I found that my bullet speeds with the ROA were low, under 500 fps. But they were only low when I measured from the 1400. When I shot the ROA or the Walker using my teloscopic measure (which I don't like but which allows me to measure bigger charges) I got anticipated speed.
This morning I was so miffed by the presumably unexplained bullet speeds that I decided to check the spouts. The 30 grain spout is actually a 20 grain spout when measured volumetrically. It throws a charge of GOEX fffg that weighs 19 grains consistently. (The missing grain of powder comes from me pressing my finger into the end of the spout.)
The 15 grain spout actually throws a charge weighing a consistent 12 grains.
I am well aware of the discussions to the effect that we measure poweder volumetrically but that the measure is actually weight. I have read and participated in these discussions and fully understand the concept.
My error was in assuming that the seller of the flasks (I bought both of them used from eBay) knew what he was talking about. I am a little embarrassed that I did not check them at the get-go. But I am mighty thankful that I have a chronograph which works well enough for me to infer these data.
Oh well...Live and learn.
September 12, 2010, 09:26 AM
For us newbies would you reveal what the Chrono velocity then was when you threw an actual 30 grain charge behind the 177 ball and curious if you chrono with a wad and without, I am thinking you were about to experiment with wads on another thread.
September 12, 2010, 10:03 AM
Doc, as far as I concerned You da man! The fact that you came back and fessed up what was going on says you deserve an atta-boy. I love it when folks post results backed by weights, measurements, science then backed up by verification and common sense.
It is not uncommon on this forum to see folks post results based on 50 grains of powder in their ROA or 40 grains in their 1858. On the one hand I think "Huh, that's not possible" and on the other hand the poster doesn't disclose if he used GOEX, Swiss, AP, 777, 2Fg, 3Fg, etc. Specifically, it is the volumetric posts that are hard to determine the usefulness. It seems that your discovery is way too common. IMHO, there isn't anything wrong with measuring your BP on a weight scale, be it 2Fg or 3Fg. The volumetric approach is based on original black powder...2Fg as I've been reminded previously by one poster. That is, 30 grain of 2Fg by weight is equal to 30 grains by volume. Its a one-to-one correlation. There are going to be some differences by manufacturer as things like powder density come into play. However, IMHO unless one has calibrated their volumetric measure then a weight measurement is more than likely to be more accurate.
I don't think any of us should assume our volumetric measures are 100% accurate. It would be a useful exercise for all of use to see how they compare by weight.
Now based on your recent discovery I guess you'll have to up your estimates for annual powder usage. :D
September 12, 2010, 10:49 AM
BTW, here are a couple of threads about powder density that could be useful:
Sieve Ratios and Comparative Densities (http://www.theopenrange.net/forum/index.php?topic=6157.msg46290#msg46290)
Various Powders by Weight/Volume Measure (http://www.theopenrange.net/forum/index.php?topic=12.0;highlight=density)
Kudos to the authors who posted that info on another forum.
September 12, 2010, 10:55 AM
Actually, I did not use 30 grains at any time. When I thought I was using 30, I was actually right at twenty. Speeds at that charge were 420 - 480. I am shooting round balls exclusively so the bullet weight using my scale for a .454 is about 132 and for a .457 is about 137. When I went up to 40 I think I remember getting 700 and change. The Walker at 40 got just a bit higher (Heavier pistol - More mass for the explosion to exert force against and longer barrel - explosion contained for a longer time.) When I went up to fifty grains in the Walker the speeds wnet to 980 fps but accuracy went to crap.
I never used wads but I am going to try it out. I use lube on the ball and then lube over the ball. The lube I use is my own concoction of 50/50 Crisco and wax rings from toilets.
Don't start in on me, folks!
Now based on your recent discovery I guess you'll have to up your estimates for annual powder usage.
You got that right....In fact I cobbled together a fixture for the top of my CVA flasks which allows me to:
1. Use one spout to measure any powder charge up to 40 grains
2. See that the spout is completely filled with powder.
It is a clear plastice tube of about 1/4 inch internal diameter threaded on one end to turn into the spout hole on the flask. Then it is cut off at a length of 4 1/2 inches. I made a plunger from an aluminum cleaning rod and fitted the plunger with felt gaskets. The plunger goes into the plastic tube and remains in place. Turn the flask upside down. Open the valve and watch the powder flow into the tube. Let the valve go closed and turn the flask right side up. Flick it a couple times to get the powder to settle and remove the voids. As long as the tube is full, the measure is accurate. With the plunger withdrawn as far as it will go, the charge is 40 grains. The tube is graduated for lighter charges.
Soon as my wife gets back from church with the camera (Remember...She goes to church and I get to play with my pistols.) I will take some photos of it.
September 12, 2010, 11:07 AM
I use a clear acrylic measure made by Thompson Center (http://www.midwayusa.com/viewproduct/?productnumber=714741).
Setting the measure at 40 grains for Goex 3Fg it throws 37 grains by weight. And setting the measure at 30 grains it throws 27 grains by weight. So, which is the right answer if I want 30 grains of 3Fg for my BP revolver? Which one is giving results that most approximate a true 30 grains of BP as originally conceived when they came up with the volumetric scale for BP? And, if I bought another one of these Thompson Center powder measures what is the likelihood that I'd get the same result?
September 12, 2010, 11:46 AM
I can remember using this CVA with the solid brass spouts and turning the thing upright after having filled the spout (I thought) only to discover that there was a major void in the powder in the spout. So when I thought it was full it was actually significantly less than full. In addition, using one's finger to cover the spout automatically reduces the powder charge by a small amount because of the portion the skin on one's finger that pushes inside and below the rim of the spout. All of these issues are quite minor and easy to overcome.
On the other hand, it is completely understandable why folks insist upon using scoop type measures so as to avoid these issues as well as to reduce the chances of a flask explosion as we have discussed previously at length.
I am familiar with that Thompson's measure and I like it but I can imagine the requirement to refill it with each chamber might introduce some opportunities for spillage. That measure was the inspiration for the one I just cobbled together this morning.
September 12, 2010, 01:36 PM
Here are some photos of the device I fiddled with this morning.
The is the measure replacing the spout on the CVA 1400.
Here are the parts. Note the felt washers at the bottom of the plunger. You set the plunger to the right charge (Black rings are 40, 30, 20, and 10. Red rings are 35, 25, and 15.)
Then fill the measure and close the valve. Take the plunger out and dump the measure into the chamber.
Here is the measure set for 20 grains and filled with powder.
September 12, 2010, 03:43 PM
The Thompson Center measure (above link) that I use has both a wiper to to insure a consistent fill and a funnel shaped top so that there isn't any spillage when pouring into a chamber.
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