Confessions of a flakeaholoic

M

Mauser69

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I am a large-flake powder junkie. There, I said it . . .

And I am proud of it. These powders are very flexible and perform very well for me (under sane conditions). But I am not immune to hubris, and that has bit me in the butt!

I have posted many times how well 700-X and Unique have measured for me (and I generally jump on and say this every time someone else starts yelling about how terrible they are). But I acknowledge that they DO have their limitation on ultra-light loads. And my recent experience has brought me back to reality.

My standard .38 Spl plinking load has been 3.0 grains of 700-X under a 148g HBWC pill. These loads have always metered just fine on my Lee Pro 1000 progressive press, and they perform quite well too. Well, about two years ago during a break in the late December weather, I decided to try an even smaller load. 2.5g 700-X seemed to load just fine, with my scale confirming good consistency in the powder throws. My first testing showed about 650 fps +/- 20 - pretty decent plinkers.

And then the hubris set in as the cold weather and snow settled back around us. Instead of being happy with what I knew was working, I decided I was invincible when it came to throwing charges of course flake powders! So I reset my Auto-Disk measure for 2.2g of 700-X and proceeded to load up a whole pile of plinking rounds, which I promptly stuck in a big can and forgot about.

When I finally dug those rounds out and started shooting them this spring, I just couldn't understand all the problems I was having. For the first time ever I was getting all sorts of variety in pops and bangs, and some of the bullets seemed to take a good 5 seconds before I could hear them bounce off of the stump in front of my bullet catcher 25 yards away! And then, horror of horrors, I started getting some total squibs with bullets stuck in the barrel of my BH - something that has NEVER happened to me!!.

No accidents or dangerous errors here - I checked the barrel each time I didn't actually see or hear the bullet strike down range, so I caught them all and cleared the problem. But DANGED am I embarrassed! I had been trying to just shoot them all up since there is no way to pull a flush wad cutter with a collet puller. But it was so bad that I finally gave in and got out the danged inertial puller and started hammering out several hundred of those lousy rounds last night.

Lesson learned - back to 3.0g 700-X, and REMEMBER that it is the bottom end of the reasonable charge range for these flake powders!!!!
 
I'm guessing the light loads didn't bump the bullets up to obturate the chamber throats. The cases may not have sealed against the chamber walls, either (visible soot behind the case mouth). In the first instance, since the bullet nose takes time to swage into the forcing cone, that's time during which the pressure can bleed off around it and out of the barrel/cylinder gap. In the second instance, you simply have an additional gas escape path all during the bullet's time in the gun.

If you have a typical production gun, the cylinder throats won't all be the exact same diameter. I have a Redhawk with 0.002" variation in its chamber throat diameters. That will account for some of the variation. If you used mixed brass or brass with different load histories and work hardening, that will vary the escape path around the brass, shot-to-shot, accounting for more of the variation. So, even if you metered the powder perfectly, as compared to your normal load, you have less gas you can afford to lose and are losing more of it through shot-to-shot non-uniform leak paths by the time the bullet reaches the muzzle.

So, you can feel relived that this doesn't necessarily reflect on your metering uniformity. It does, however, explain why people go to very fast powders for very light loads. They burn up before the bullet has moved much, making a higher peak pressure that accomplishes the sealing while the bullet gets underway. Clays, for example, might be just the thing for you if you want to do this with a flake. N310 is extruded, but has similar burning rate properties and would be another good choice for trying to find a minimum load.
 
It WAS Powder Variation

No, the problem was absolutely powder variation. That was obvious as I pulled the bullets. Even though the total powder for 2.2 or 2.5 grains of 700-X is quite small, the difference in how much powder I got out of each case was dramatic and very clear. Quite a few cases only had a few flakes in them, and a bunch of others were clearly about 1/2 of the expected.

My log shows that I did weigh the initial test loads of 2.5g, and they were quite uniform (also supported by the chrono results). But I actually weighed almost none of the 2.2g loads - I just ASSUMED that the charge was so close to the prior 2.5 grains that it HAD to measure just as well. I know - stupid, very stupid; I plead guilty.

My message, and the point of this thread, remains clear: I continue to believe very strongly that these flake powders measure just fine with good equipment and good technique. I have proven that numerous times. But there IS a lower end at which you cannot trust them in a volume measure, and that turns out to be very close to .40 cc, exactly like Lee states on their VMD data chart. For me, 700-X seemed to measure decently down to about .34 cc, but went to total shinola below that. From now on, I'll stick to .40 cc unless I do a LOT more scale checking with anything smaller.
 
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OK. Your post just said you checked them to be 2.2 grains, but not that you'd found uneven charges after pulling them. That makes an easier reason than problems with sealing.

Since you used a disc measure, it suggests there is an opening diameter at which the flake bridging behavior begins to occur easily. If you get a chance to measure the opening difference between 2.2 and 3.0 grains, it might be interesting to learn how many grain diameters it was. That could well translate to useful information when using other flakes.
 
That is a good point - all of these loads were done with the Lee Auto-Disk, where the hole diameter gets smaller, but the depth remains equal. I have also had excellent conformity using my very old RCBS Du-O-Measure, but that is a drum measure where the hole diameter remains the same and the depth gets smaller.

Next time I get a bit bored, I'll not only measure the Lee disk hole diameters, but spend an hour or two throwing test weights from both sides of the Du-O-Measure to see how the different drum hole sizes respond as the charge volumes/weights get down below 3.0 grains. (Hey, another project I can take on to put off doing my taxes a little longer!!):D
 
I finally gave in and got out the danged inertial puller and started hammering out several hundred of those lousy rounds last night.
Click to expand...

Ouch!:eek:

Sorry to hear that, but better than an accident.

Yes, I am one of the ones that has grown to despise 700-X because of the metering. I also use a Lee, but I use the adjustable charge bar with my dispenser. Perhaps I should go back to the hole system if it seems to work for you. What CC hole are you using for 3.0 grains?
 
3.0 grains of 700-X is with disk .40 - I think I actually get about 2.9 grains if I remember correctly, but I haven't loaded those in the last couple of years.

NOTE: While 3.0g is the starting load for 148 LHBWC bullets in the current Hodgdon load data for .357, current load data for .38 Spl shows the MAX load for this same bullet is only 2.5 grains! This is much lower than the charge weights for heavier lead bullets in the same data, but caution is still advised. My original load of 2.9g 700-X with the 148 gr HBWC comes from Speer #9, where it is shown as max laod for that bullet/powder.​

All of my 700-X is very old, and I know there have been at least three different formula variations over the years (one has holes in the flakes, two have yellow identifier flakes, etc.). Even though the load data never changed with the formulations (based on the old DuPont and IMR load data I have), I have no way of knowing if the VMD factor might have shifted a bit over time. But I'd still expect the .40 cavity will be pretty darned close to 3.0 grains.

I have never used the adjustable charge bar - I just can't get over what seems to be a really stupid design of that real wide channel with just a slight crescent at the end to try and funnel down small charges. I know how to modify it to improve the performance, but I just don't want to mess with it when the disks work well for me.
 
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You can figure the practical VMD for yourself. Just put in a bigger disc, throw ten charges and weigh them together, divide by ten to get the average weight of a throw, then divide the CC rating of the disc by that average throw in grains. Voila, your VMD for your lot of powder, as it actually works in your measure operated with your rhythm and vibration levels and all that jazz. It'll be a better number for you than the one in the table.

Also, you want to repeat that with each new lot of powder you buy. Western shows VMD's and bulk density tolerance for their powders. Some vary by up to ±5.6% by lot. I don't know how much others vary, but it's so easy to check the way I described that it makes sense to do it for your particular powder lots and put it on the container with a Magic Marker.
 
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