Inconsistant Velocity Issues

[Sitex31]

Hello all. I just got started reloading for 9mm about a month ago and I have a few questions. I have a Lee single stage setup with a Lee perfect powder measure and a Frankford Arsenal digital scale. I just recently got out to crono my first batch of test rounds and I was noticing a fluctuation in velocity. About 61fps being the max. I was wondering if anyone has experienced this. Dumb questions I feel I must ask to follow: Is it normal? Is it the scale? The powder measure? The powder? I'll list all the critical info below.

Brass: WIN
Bullet: WIN 115grn FMJ
Powder: Hogdon HS-6
First 10 rounds: 6grns HS-6

• 1007
• 1011
• 1053
• 1019
• 1026
• 1066
• 1068

The Lyman manual lists min/max grains for HS-6 at 5.7(956fps) to 7.2(1193fps). I started at the low end and need it to be a little higher but I don't want to proceed and end up loosing a hand. Thanks in advance!

 

[rclark]

: Is it normal?

Yes . Quite normal. Slightly different weight, where it powder sits in the cartridge when ignited, primer might be slightly different, case tension on bullet, wall thickness, crimp, depth of bullet ... lots of 'variables' you may not have complete absolute control over. With this powder ES (extreme spread) of 61 isn't bad.

Just for comparison :

.45 Colt
13.0g HS-6, 255g SWC, CCI-300, 1100fps, 19 SD, 62 ES, 14 Shots

.45 ACP
7.5g HS-6, 200g TC, CCI-300, 887fps, 16 SD, 51 ES, 14 Shots
8.0g HS-6, 200g TC, CCI-300, 934fps, 15 SD, 46 ES, 14 Shots
8.5g HS-6, 200g TC, CCI-300, 1010fps, 9 SD, 28 ES, 10 Shots

 

[chris in va]

I recently saw a video about the PPM. Seems you need to tap it a couple times before and after dropping powder. The guy showed a +-.1gr variance if that wasn't done.

 

[tkglazie]

I agree with both the above. There are tricks for most powder measures, apparently the PPM likes the same double tap that the AutoDisk does (thanks again Brian P for that tip).

Regarding 61fps ES with a 1000fps bullet- if the results on the targets are good you are more than fine right there. That is very close to the magic 5% number that I was taught is a nice rule of thumb for a good spread (factory quality). 2.5% would be a match quality ES.

 

[Sport45]

Also keep in mind that a $100 chronograph probably isn't going to be 100% accurate and repeatable. If you lined three in a row and shot through them, would they all report the same velocity?

 

[solocam72]

I bought a competion electronics pro chrono and I had some really weird issues with it, I shot my .44 magnum over it and got similiar results in deviation that you have, the real problem I had was a day later I turned the chrono on to look at the numbers again and it showed readings that weren't possible from anything I owned! I cleared the chrono out and shot over it again and wrote down my velocities on paper, the next day I turned it back on to check velocities again and sure enough it had changed numbers on its own again! I contacted competition electronics and explained it to them and they replaced the unit, I havnt had any issues with this one but it definately makes me wonder the accuracy of them?

 

[hounddawg]

never loaded any pistol for precision but could neck tension from a inconsistent crimp have something to do with it ?

 

[Lost Sheep]

Thanks for asking our advice. Welcome to the forum and to reloading.

All the above are correct, especially tkglazie's post.

If you load 20 cases exactly as you would have it you were assembling cartridges, but before seating the bullets weigh the charges. See the statistical spread of the charges. Then shoot them over your chronograph. For extra information, keep track of the charge weights in each cartridge (and even the bullet weights if you are so inclined) and see if the velocities have a relationship with the charge weights.

You also might try something that rclark mentioned. Shoot a few with the powder near the primer and another few with the powder near the base of the bullet.

Educational.

Lost Sheep

 

[the led farmer]

In the grand scheme of reloading a swing of 61'/sec amounts to exactly doodley squat

If anything it tells you at least you are throwing consistent loads

 

[Strafer Gott]

The perfect powder measure will even drop Unique to .1gr if you start and finish on the upstroke. Tapping helps, but not as much as simply giving it a chance to fill by stopping on the upstroke.

 

[wyobohunter]

Nothin Wrong

Avg. Velocity = 1036
Extreme Spread = 61 fps
Standard Deviation ≈ 31

Actually not bad. You probably would not use this for the 1000 yd. target at Camp Perry, but for HD, SD, Race gun, plinking etc. there's nothing wrong with it from these numbers. Does it group well?

Oh, and somebody mentioned something about a $100 Chronograph. Your chronograph will be accurate enough. I wonder if the guy that mentioned that has/uses one?

A $500 Chrony will not be 100% accurate. A $100 unit is 100% better than an educated guess.

 

[Sitex31]

Thanks for the replies everyone! I guess that an ES of 61fps is not that much, but I am somewhat anal retentive so it irks me just a bit. The accuracy is pretty good and the groups are tight. I've tried the tapping trick on the PPM and will find out next trip to the range if it helps any. I've been shooting steel challenge and just started shooting IDPA so I am not looking for extreme accuracy, but just enough to hit the zero ring on those longer shots. Also, I plan on changing to a better powder like Titegroup, so I want to make sure I know my equipment is accurate before I start loading that stuff. Thanks again!

 

[reynolds357]

That is about as good as it gets loading by volume and not weight.

 

[tkglazie]

That is about as good as it gets loading by volume and not weight.

I beg to differ! My LCT with an AutoDisk Pro throws a 4.8gr charge of HP38 (.46 disk) under a 200gr .452 LSWC (18bhn) that nets me an ES of 14 fps across a ten shot string (775fps). And thats with a tight FCD swaging the bullets a bit.

To be fair, thats the only load that I make with that good an ES, but 25-50fps is pretty easy in a midrange handgun load. I dont load hot (1040 is my hottest 9mm load, for example) so dont hold me to that statement for full power loads.

The AutoDisk is a remarkable tool with the right powder and some good technique.

Not to mention, lots of quality factory match grade ammo is charged by volume.