Evaluating unknown powder - advice please

[MrPhil]

Long story short, I purchased 20 pounds of BW-36 powder for $100. It came in 2 lb sealed bottles in a sealed carton. It's 1990 vintage. Smells like new. Supposedly a 3031 equivalent, a short extruded granual. It came with loading data for .223, .243, 30-30, 308, 30-06, 303 British, and 8mm Mauser. Mostly midweight bullets, midrange velocities.

I load a lot of 308. The data shows velocities on the low side of what I'm used to. Starting load for a Sierra 150 grain soft point is 40 grains. I backed off to 37.5 to start, using military brass. Last night I loaded 37.5, 38, and 38.5 grain charges (10 each) behind Sierra 150 grain boat tail ballistic tips. Today I shot them all over the chronograph. They all grouped pretty well although I was mostly focused on not shooting my chrony. All extracted easily. Very light recoil.

The velocity data puzzles me. Mean velocity did not change load to load. Standard Deviation decreased significantly with increased charge.

Here's some data:

37.5 grains BW-36
High: 2583.9
Low: 2427.9
Mean: 2514.1
S.D.: 49.4

38.0 grains BW-36
High: 2578.9
Low: 2460.0
Mean: 2511
S.D.: 34.3

38.5 grains BW-36
High: 2542.1
Low: 2476.0
Mean: 2512
S.D.: 24.6

What does this mean? My inclination is to bump up to 39.0 and 39.5 grains to see what happens.

 

[MTKTM]

What does this mean? My inclination is to bump up to 39.0 and 39.5 grains to see what happens.

In the loading data that you rec'd with the powder, what was the range between the starting load and the maximum load? Assuming it was more than a couple of grains, I'd probably be inclined to go straight to the 40gr. quoted starting load and increase .5 grain at a time from there. Sounds to me like maybe that particular powder needs a certain loading-density before it begins to build pressure over a minimum base level.

 

[ArchAngelCD]

If that powder you bought is in fact very smiler to 3031 then it's not really suited for loading the .308 for the most part. Yes it will wok but it's too slow a powder to achieve maximum velocity as you proved for yourself. The only thing that will happen with a powder that fast in the .308 is an increase in pressure with a corresponding increase in charge weight.

With a powder in that burn rate I would suggest keeping the charges light to prevent pressure spikes. Try lowering the charge weights until you see a drop in velocity. When you see a drop go back to the last charge where the velocity was the same.

 

[canoe on the yukon]

Ditto to Arch......If it's comparable to 3031,it's too fast to be efficient in the 308 case.Pressure will rise disproportionately to the velocity.As has been said,it will work but don't expect anything near optimum performance.

 

[Recon]

MrPhil:

You might try asking Western Powders in Miles City, Montana. I looked at long list of commercial powders they carried at that time. I don't know if they still carry commercial powders or not but they have a ballistics lab on site and maybe they know of the powder you have and can advise further.

Regards..

 

[MrPhil]

Thanks for your replies. Very helpful information. 3031 (or it's possible equivalent) is not a great powder for 308. It's just that I have (now) 19 and a half pounds of it. I'm going to work up loads for pretty much everything I own. It seems that it may be a winner for 223 Rem.

MTKTM - I worked up to 40 grains today. Data is below. You were right! I should have gone straight to the starting load. I'm going to work up from there. In any event, it's a good science experiment.

Some of you may remember Iowegan. I always enjoyed his posts on this forum. I noticed his absence and was pleased to find him on another forum. Here's a link to the discussion we've been having on this topic: http://www.rugerforum.net/showthread.php?t=14904

Anyway, I copied-and-pasted my most recent data. Today was a gorgeous day to shoot.

Iowegan, thanks for your feed back. I especially like your case volume comparison technique. A lot neater than measuring grains of water. I don't want any of that dihydrogen monoxide near my loading equipment. I'm very clear on the inverse proportionality of pressure and volume.

Your information reinforced my inclination to increase powder charge. Today I loaded 3 more strings of 10 each. Started where I previously left off, using the same 150 grain boat tail ballistic tip. Went to the range and ran them over the chronograph. The data are revealing.

39.0 grains BW-36
High: 2628.9
Low: 2529.2
SD: 36.1
ES: 99.7
Mean: 2578.8

39.5 grains BW-36
High: 2608.4
Low: 2556.7
SD: 19.4
ES: 51.7
Mean: 2581

40.0 grains BW-36
High: 2646.3
Low: 2609.2
SD: 13.5
ES: 37.9
Mean: 2622.9

Look what happens with the 40.0 grain starting load. Extreme spread drops significantly. Velocities on all 3 loads are higher than the data posted on 6/19. Temperature was mid sixties on both days. Extraction is still easy. Primers are flat with no evidence of cratering, unchanged from Friday.

 

[Paul5388]

It looks to me like you have a slightly slower burning powder than what IMR is using, provided their data isn't inflated like so many are.

I think it would be safe enough to use 3031 data and compare what you're getting with the data on their website. http://data.hodgdon.com/main_menu.asp

 

[MrPhil]

Paul, thanks for the input and the link. Looks like 3031 max loads run right at max SAAMI pressure. I will approach them with my eyes wide open, behind appropriate PPE of course.

 

[okie john]

Things are starting to shape up at 40 grains. A 150-grain bullet at 2,600 is 300 Savage country. The military 30/06 150-grain load was only 100 fps faster. That load will kill deer all day long with very mild recoil, so it's ideal for the kind of lightweight rifle you'd want for still hunting or mountain hunting. It will also reach out a lot farther across a clearcut or a sheep meadow than you'd think.

Anything more might justifiably be considered icing on a very nice cake.


Okie John

 

[MrPhil]

Thank you all for sharing your info. okie john, you are correct that these loads are nothing to sneeze at. They are very easy recoiling and group fairly well. I've never analyzed incremental loads over this wide a range before. It has become an end in itself.

Anyway, I loaded 3 more strings of 10. Again using .5 grain increments, starting at 40.5. Same bullets and COL. Here are the data:

40.5 grains BW-36
High: 2704.5
Low: 2661.3
SD: 16.3
ES: 43.2
Mean: 2685.7

41.0 grains BW-36
High: 2740.6
Low: 2675.5
SD: 19.1
ES: 65.1
Mean: 2708.9

41.5 grains BW-36
High: 2726.6
Low: 2697.2
SD: 10.1
ES: 29.4
Mean 2711.1

Velocities are quite a bit higher than those posted on 6/23. Weather was sunny and 70. Groups were OK, no standouts. None were as good as any of my 168 grain Sierra Match Kings. Extraction was easy. Cases looked good. Primers are flattened, significantly more so than Benchmark and Varget loads. Frankly, I think this is near the top of useful range.

On a side note, I cleaned the bore pretty thoroughly the night before shooting the new test loads. I had been running Hoppe's powder through it after every session. This time I hit it with Hoppe's Bench Rest. A lot of copper came out. A good lesson. After this session I really went at it with Sweet's 7.62. Even more copper came out; lots and lots of blue patches.

As always, I look forward to your replies.

 

[ArchAngelCD]

Looking at the data you provided above I would think a charge of 41.0gr is just about as high as I would go. Maybe a tenth or two more but not 41.5gr I would think.