No.7 Powder Test – 5 rounds
The No.7 Powder in this test was screened with 2/3 of the Granules falling through 10 Mesh screen and being trapped on a 20 Mesh screen; 1/3 of the Granules screened to fall through a 20 mesh screen and be trapped by a 40 mesh screen. This was powder that has been stored in a large Vitamin Pill Jar for the last - 60 days or so. No fines (less than 40 mesh in size) were in this test mix.
Humidity was high today at 71%; so I decided to put it in the Dehydrator at 130 degrees for 1 and ¼ hours; just to remove moisture as a variable in the Testing.
Load data is mixed .308 Winchester cases, CCI number 200 Large rifle primers, 30 Grains of No.7 powder, and RCBS 200 Sil powder coated Boolit with aluminum gas check.
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No.7 Powder Test – 5 rounds - Group and Velocity
Shot the 5 Test rounds this afternoon. Temperature was about 57 degrees, with a light drizzle. Target was a 7/8 inch spotter on standard 8 ½ x 11 inch letter paper; at 100 Yards.
Velocities:
1354
1341
1421
1395
1442
Average velocity:
1390 feet per second. Still 300 to 400 fps lower than my desired goal; but we will see what can be done. Looked down the barrel each shot; and the unburned kernels were a little less than when firing a commercial WC860, WC870, or WC872 powder without a "Kicker". Could look at a small smokeless powder of 2 to 3 grains over the primer to boost the ignition temperatures; but that goes against my goal of "Home Made" that meets my goals without commercial products (less the reused numerous times 308 Winchester brass).
Group size was 3 and 3/8 inches.
Attachment 326763
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No.7 Powder - Experiment trying to Extrude Sticks of No.7 Powder
My thoughts on attempting to improve the granule structure beyond screening resulted in me once again attempting to use a Spaghetti Press to make a for of extruded sticks (similar to IMR powders from the 1920’s until now). I had bought this spaghetti press a few months ago; and initially tried it unsuccessfully as the screw on cap with the holes popped out of the threads that held it in place. This was from amazon: https://www.amazon.com/Stainless-Fet...cx_mr_hp_atf_m
For this attempt to make the No.7 into “Stick Powder”; I used the above listed spaghetti press and selected the extrusion cap having 1.5mm diameter holes. I selected this cap because it was the smallest holes; and the closest size to the original IMR 4895 Stick width.
This batch has the same ratio of chemicals in the batch as previously used; with these amounts:
Ammonium Nitrate 221 Grains
Potassium Nitrate 65 Grains
Lead Nitrate 53 Grains
Charcoal 65 Grains
I wanted to limit the amount of water as previous batches produced were very watery, with equal volumes of water and chemicals used – just as described in the original manual for producing No.7 powder. I mixed all the chemicals above in a small glass jar; rotating by hand the mixture in the jar to mix for about 4 to 5 minutes; at which time by appearance it was thoroughly mixed. I dumped the batch into the middle of a Glass Pie Pan; and added 125 drops of water. I then used Auto Body filler plastic spreaders to mix the chemicals and 125 drops of water. The result was a wet black dough looking substance.
Attachment 326842
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No.7 Powder - Experiment trying to Extrude Sticks of No.7 Powder
I placed the mixture into the Spaghetti Press; and twisted the compression crank slowly. Under compression; excess black water began to come through the extrusion holes:
Attachment 326843
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No.7 Powder - Experiment trying to Extrude Sticks of No.7 Powder
As I continued to turn the compression crank, resistance dramatically increased. It became apparent that I was about to experience a repeat of my first attempt weeks ago where the Extrusion Cap would fail and come apart at the thread where it screws in.
I removed the extrusion cap and twisted the compression crank until a solid “Puck” of the No.7 mixture was expelled onto a Glass Pie Plate. In the picture the “Puck can be seen, and below it the pool of thick black water that was extruded before the puck was removed.
Attachment 326844
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It appears that the chemicals when mixed well in a limited amount of water actually form a thick semi-solid under pressure that will not pass through the 2mm holes I was using. The black colored water was extruded, but not most of the chemical mixture . The Puck resulting is looking a lot like what the Muzzle Loader group is producing in their thread My Home Made Black Powder: https://castboolits.gunloads.com/sho...ck-powder-quot
Analysis of attempts to Extrude No.7 Powder into stick powder
My thoughts are that during the production of Nitro Cellulose (used to make Commercial Smokeless Powders since the late 1800’s – NOT USED IN PRODUCING No.7 POWDER); the cotton or wooden fibers used for the cellulose are broken down in the acid to a very small size molecularly. These small fibers are able to pass through the extruder holes in the commercial extrusion process; whereas in my experiments, the No.7 chemical mixture ( and possibly Black Powder Mixtures) are not passing through extrusion holes. The chemical mixtures do not (will not?) pass through – rather they bind together under pressure instead of flowing through the extrusion holes. Perhaps a different extrusion die set up with higher pressures might work with the No.7 powder mixture; but I am not set up for that type of experimentation currently.
At a later date; I may try an Extrusion Cap with for the Spaghetti Press with Larger holes; or perhaps one that is rectangular in shape and see if that might give a different result. Reason for my thoughts down this path are my previous experience in experiments with increased velocities and narrower pressure ranges for larger granulations of N0.7 powder. It will require some more thought and experimentation down stream.
I am currently dehydrating the "Puck" and the black water from this experiment in my electric dehydrator at 130 Degrees after this experiment. Might be interesting to see if the "Puck" when ground up will have same, less, or greater velocities and velocity spreads.
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Analysis of attempts to Extrude No.7 Powder into stick powder
So the Puck of No.7 Powder made while attempting to make "Stick Powder" described above completed a 24 hour drying cycle in the electric Dehydrator at 130 degrees. I crushed the puck and separated/screened it into 10 - 20 mesh, 20 - 40 mesh, and 40 and smaller mesh sizes. The amount produced after crushing for each was:
74.5 grains 10-20 mesh
110.3 grains 20-40 mesh
192.3 grains 40 & smaller mesh.
377.1 grains total screened weight
The original total weight of chemicals used in this batch was 404 grains. There was approximately 27 grains difference in weight; probably due to the materials carried with the water when compressed through the extrusion holes, and residuals inside the spaghetti press lost when cleaned.
One of the trends I have noticed in producing No.7 powder through dehydration vs cooking is a grayish color on the surface of the dried mixture. This indicates to me that one of the chemicals has a portion of the chemical being drawn to the surface by the evaporating water. Not sure which chemical it is, or if it may have some impact on the ultimate velocity and velocity spreads of the N0.7 Powder as compared to cooking it on a stove.
Attachment 326867
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Previous experiments in this thread indicate that the 40 mesh and smaller No.7 "kernals" do not provide top velocity for the powder - and they produce much larger velocity spreads. Seems based on my current testing and documentation results, that we are looking at ~ 50% of the batch as having to be put into the "Recycling" container for inclusion into the next batch as it screens too small for effective use.
It may be that other techniques will produce a greater "1st time" percentage of useable powder. Comparing current and past efforts by memory is highly suspect; but my memory/gut indicates that "Cooking" the No.7 mixture resulted in harder kernels, and the % of larger grain structure was higher for batches. I will have to explore that possibility in future testing by doing one or more experiments with cooking No.7 to gather data. A harder kernel will make crushing more difficult before screening; but if it produces a greater quantity of "Acceptable" No.7 powder per batch, it may be beneficial to return to cooking.
I prefer not cooking, as it removes the risk of small particle fires during cooking of the chemical preparation. The original reference for N0.7 powder stated when cooking to keep water at hand to quench any particles that catch on fire during preparation; I used a spray bottle of water and had to do a spritz one or two times during cooking No.7 powder to put out a "Glowing" particle area in the batch. As I stated; I may investigate cooking again, and collect velocity data afterwards to see if there is a difference in velocity and velocity spread between Cooked and Uncooked No.7 Powder.