DIY Smokeless Powder - No. 7 Smokeless Powder Manufacturing

[The Cowboy Professor]

What's the latest, Mustang? What were your test results on homemade #7 powder? Thank you.

[The Cowboy Professor]

I see the full string now. I only had the January posts prior. Thank you for the results. Appreciated.

[MUSTANG]

One might want to try adding a burn rate accelerator to your current mix. I tried a couple of different ones, but settled on using ammonium dichromate or potassium dichromate. I have no idea if one dichromate is better than the other. I settled on using 3% of the total mix being a dichromate, but the range others have used is between 1% to 5%.

They are available from pyro houses. PLEASE READ WARNINGS ABOUT WHAT CAN HAPPEN IF ONE GETS A DICHROMATE ON ONES SKIN, etc. But given that it's widely used, others including myself have used it safely.

Unfortunately, I have no test data to share. My goal was much different than yours, so I never tested for velocity.

There are other accelerators and I didn't try all of them.

In post #120, Procter had postulated that addition of 1% to 5% of either ammonium dichromate or potassium dichromate (Accelerator's) might increase velocity (Mixture Burn Pressures). I ordered Potassium Dichromate from one of the fireworks houses to give this a try.

My first attempt I used 2% potassium dichromate. I took "Fines" from previous No.7 batches and mixed the potassium Nitrate in order to get a 2% concentration of Potassium Dichromate into the mixture. The entire mixture went into a small class jar and was rolled, swirled, shaken, to mix the blend. Humidity during this process was at about 68%, note in the picture the coupe of small orange granules area (unmixed potassium dichromate). Took a while to get those mixed into the blend:



After it was all dry mixed; I added 125 drops of distilled water. I then mixed the water and dry powder in a glass pie pan. The mixture was then dried for 24 hours at 130 degrees in an electric dehydrator. Afterwards, The mixture was scraped from the bottom of the glass pan using a razor scraper and screened to be between 20 and 40 mesh.

[MUSTANG]

I loaded 5 rounds using 30 grains each of the No.7 Powder enhanced with the 2% Potassium Dichromate. Temps were about 70% with a humidity of 78% according to weather site. Velocities of the 5 round test group were:

1361
1390
1297
1346
1308

Average Velocity was 1340 feet per second.

Group size was 4 and 3/8 inches at 100 yards. The red spotter is 13/16 inches wide/tall.



2% Potassium Dichlorate doe NOT seem to have increased pressures. Additionally; the average velocity of the 5 test rounds was about 40 feet per second lower than the Velocity in the Test of Post #122 previously. The low number of test rounds, temperature differences, humidity differences, etc.. may be skewing data. I think I will do another test later using 4% to 5% Potassium Dichlorate in the mixture - just to see if there is potentially a greater velocity not yet achieved.

I will say that the "VISUAL" on the 5 rounds of this test are that the cases after this test do not have the dirty black necks of previous testing.

[MUSTANG]

I decided to remake and test “Cooked” No.7 powder as follows.
I mixed theNo.7 Powder chemicals at the following weights:

Ammonium Nitrate - NH4NO3 - 110.2 grains
Potassium Nitrate - KNO3 - 32.4 grains
Lead Nitrate - Pb(NO3)2 - 26.54 grains
Charcoal C - 32.4 grains

The Lead Nitrate was clumpy based on pulling water from the atmosphere – despite keeping the chemical (previous small amounts used from this container) being kept in the original container with the lid on tightly. For mixing; I placed the Charcoal in the center of an 8 inch Cast Iron Skillet in a mound, and created a center cone where I placed the Lead Nitrate. Since Lead Nitrate is soluble in water; I put enough distilled water in the “Cone” of the charcoal causing the lead nitrate/water to fill to the top, and allowed it to sit for 2 to 3 minutes. I then poured the remaining chemicals onto the lead nitrate and charcoal. After this; I poured an additional 15 milliliters of distilled water onto the Chemicals; stirring all the chemicals for 2 to 3 minutes with a stainless steel spatula to ensure they were well mixed. Any small lump was crushed and stirred into the mix.

I turned the Propane stove on high heat until the chemicals/water bubbled. I kept a spray bottle within easy reach in case any particles should burn while cooking; today there were no particles catching fire. I stirred and pushed the mix until almost all the water was gone and a semi-thick black mixture began to form – I then turned the burner to very low. I continued to stir with the Stainless Steel spatula; scraping the bottom and sides of the pan to keep all the chemicals together. This results in the chemicals beginning to group together in scraped clumps – continued to cook on low heat until the chemical mixture looked “Almost dry”, at which time I took it off the fire and let the skillet cool. I then scraped all the cooked chemicals from the pan onto a glass pie plate, and placed it into the Dehydrator for 3 hours to ensure the moisture was all gone. As necessary; I used an old putty knife to scrape off chemicals sticking onto the spatula or spot areas of the Cast Iron Skillet.

I loaded 5 rounds of .308 Winchester using 30 Grains of the Cooked No.7 powder topped by an RCBS 200 Sil Boolit as in recent previous tests. Of note; for this batch, the cooked No.7 powder seems to be denser than the uncooked tests. 30 Grains in the case was “Below” the neck of the cases – quite evident that cooked powder is taking slightly less volume than the previous uncooked test powders.

Velocities for the 5 Round Test were:
982
1011
1071
1058
903
Average Velocity was: 1005

Test Group picture follows - Black spotter is 7/8 inch. Note stringing and larger size from previous testing.



Temperature was 64 degrees F., Humidity according to Weather Underground Internet site listed at 76%, and it was raining during test shooting.

[MUSTANG]

The significant modification to this test was the addition of about 3% Potassium DiChromate by weight to the Cooked No.7, prepared as described in the previous test in the previous post above. The DiChromate was added to the Ammonium Nitrate and Potassium nitrate in a small glass jar and rolled until it was judged to be equally spread throughout those two chemicals, which were then all placed over the charcoal/Lead Nitrate, water added, and cooked as described previously.

Weight of chemicals used for creating the test powder::

Ammonium Nitrate - NH4NO3 - 110.2 grains
Potassium Nitrate - KNO3 - 32.4 grains
Lead Nitrate - Pb(NO3)2 - 26.54 grains
Charcoal C - 32.4 grains
Potassium Dichromate - K₂Cr₂O₇ - 6.0 grains

The velocities of the 5 rounds for this test were:
1395
1296
1447
1322
1320

Average Velocity was: 1356 feet per second.

Test Group picture follows – Black/Orange spotter is 13/16 inch each side. Distance was 100 yards.



Temperature was 64 degrees F., Humidity according to Weather Underground Internet site listed at 76%, and it was raining during test shooting.

[MUSTANG]

In my mind, there is conflicting performance on these two tests and as compared to previous. But; trying to seek knowledge from the testing to date:

1. It does seem that cooking the No.7 mixture results in a denser powder than does the attempts to dehydrate the mixture in an electric dehydrator. Cooking should result in ability to se more powder in the .308 Winchester case - and "Should"; result in higher velocities, yet to be proven. The author in the original paper states that the cooking causes air space within the particles, aiding in burning.

2. As my comparative observation; No7 Powder is more energetic than is Black Powder in comparison. On a velocity comparison, Black Powder shooters (Muzzle Loaders I believe) are getting similar velocities as seen in Post # 8244 and # 8245 of the following link, where Homemade Black Powder is achieving velocities of low 1300’s to 1400's feet per second. This link is on the Cast Bolts Forum. https://castboolits.gunloads.com/sho...er#post5733323

These black powder velocities were achieved using about 60 Grains of black powder, compared to 30 Grains of No.7 powder in my Tests in this thread (i.e. 145 and 146 Posts above). The black powder link was using a 50 cal round ball which is about 200 grains – same general weight as my Powder Coated RCBS 200 Sil boolits in my tests. My assessment/thoughts are that this means the No.7 is generating about twice the energy (possibly twice the pressure?) of Black Powder. I would be very cautious using the No.7 powder in a Muzzle Loader - I Do NOT see myself as using No.7 in my muzzle loaders. I can make Black Powder for them, so I see no reason to travel down that path.

3. When I get low pressure results in these .308 Winchester Tests (for sake of argument less than 1300 feet per second) with the No.7 Powder; it seems that the brass does not expand rapidly enough to seal the chamber as the boolit exits the Neck of the brass. I base this on the necks and upper shoulder areas of the brass from the Cooked Only No.7 powder in Post #145 above, compared to the brass from adding the 3% Potassium DiChromate in Post #146 above. Picture of the brass follows; with Cooked only No.7 being brass cases 1-5 from the left in the picture; and the lesser blackened brass in cases 6-10 on the right.



This pattern is repeated throughout all tests to date - less blackening of the cases when Higher Velocities are achieved.

4. I may remake another two Test Groups as in posts #145 and #146 above; loading to 32 or 33 grains and see what the impact is of an additional ~10% of No.7 powder will achieve since there was sufficient unused case capacity in this test for additional powder.

5. There seems to be a conflict in results of the use of Potassium Dichromate between my 1st attempt using the "Dehydrated" No.7 process compared to the "Cooked" No.7 process. In the "Cooked" No.7 powder test above; I got a higher average velocity by about 350 fps with Potassium Dichromate compared to just the basic "Cooked" No.7 Mix.

Comparing this to previous "Dehydrated" No.7 mixtures. In Post #122 an average velocity of 1390 feet per second was achieved without Potassium DiChromate (30 Grains of No.7 used), while an average of 1340 fps was achieved using 2% Potassium DiChromate (30 Grains of No.7 Powder). A reduction of velocity of 50 feet per second with the Potassium DiChromate version in that test.

It seems indeterminate if the use of Potassium DiChromate will generate higher velocities. From a very limited testing and data collection; so far to me it appears that a 3% content of Potassium DiChromate may have shown benefit. This will require further exploration down stream.

[perotter]

Got wondering the other day about how much crimp are you using, if any.

On all the powders of this type I tested I used a heavy crimp to get the pressure curve shifted to the left plus a hoped increase in mass burn rate. I'm not a bench rest shooter and don't worry about a losing some accuracy.

I'm in no way questioning your loading methods nor telling you what to do, but am curious.

[MUSTANG]

Using Boolis sized to .310 after Powder coating. Brass is fully sized; then I use an RCBS .309 Neck expander die before seating the cast Boolit. The rounded base of the Gas Check (.014 Amerimax Aluminum) allows seating the boolit without shaving; as it pushes the case mouth out of the way just enough to allow seating without shaving. I found the standard .308 Neck Expander resulted in shaving. I use a 30 plus year old Hornady New Dimension .308 Winchester die that has a "Drop" neck guide that keep the Boolit/Bullet lined up so it does not go into the neck at a slight angle.