OCW Testing Velocity Outliers

[Mark1954]

I've been reloading for some time but only now trying things like OCW tests. My question is about the possible cause of an excessive (?) velocity outlier. For example:

Shot 1: 3651
Shot 2: 3509
Shot 3: 3642
Shot 4: 3675
Shot 5: 3643

The 3509 result seems too far away from the others. All the brass is the same brand (WIN) but a mixed bag of unknown history. They were all cleaned and trimmed to the same length. Powder charge was trickled to weight on and RCBS electronic scale. Is it possible the outlier is a result of neck tension and is it so extreme it must be a powder scale problem?

Thanks in advance for your help

 

[straightshooter1]

I've been reloading for some time but only now trying things like OCW tests. My question is about the possible cause of an excessive (?) velocity outlier. For example:

Shot 1: 3651
Shot 2: 3509
Shot 3: 3642
Shot 4: 3675
Shot 5: 3643

The 3509 result seems too far away from the others. All the brass is the same brand (WIN) but a mixed bag of unknown history. They were all cleaned and trimmed to the same length. Powder charge was trickled to weight on and RCBS electronic scale. Is it possible the outlier is a result of neck tension and is it so extreme it must be a powder scale problem?

Thanks in advance for your help

I used to have similar problem with my ChargeMaster 1500 as sometimes I'd have an ES of 1.6 grs on my charges, which would give me that kind of "excessive (?) velocity outlier". Now I use a second scale with a resolution of .02 gr along with it to get that ES down to .04 grs.

See my comment in other thread: https://www.snipershide.com/shootin...-to-improve-consistency.7004144/#post-8538794

 

[Doom]

I don’t think you have a scale issue. As far as measuring is it possibe you missed trickling that round? You didn’t give the cartridge or powder/bullet info but I’m guessing it would take around a grain or more to get that kind of spread. That kind of error should be obvious on inspection of the cartridge prior to seating the bullet.

Its possible that neck tension is the problem or it could be chronograph error. What chronograph are you using?

Did POI show significant deviation?

 

[nn8734]

I've been reloading for some time but only now trying things like OCW tests. My question is about the possible cause of an excessive (?) velocity outlier. For example:

Shot 1: 3651
Shot 2: 3509
Shot 3: 3642
Shot 4: 3675
Shot 5: 3643

The 3509 result seems too far away from the others. All the brass is the same brand (WIN) but a mixed bag of unknown history. They were all cleaned and trimmed to the same length. Powder charge was trickled to weight on and RCBS electronic scale. Is it possible the outlier is a result of neck tension and is it so extreme it must be a powder scale problem?

Thanks in advance for your help

Just some questions, as I will have this issue every so often as well:

1) do you weight sort and/or capacity-sort your brass after initial cleaning, primer removal?
2) do you uniform your primer pockets (I just started doing this to see if it has any measurable impact on my loads’ consistently)
3) was every charge exactly the same weight with those 5 rounds?
4) was every bullet seated with the exact same jump into the lands?
5) Did every primer seat with the broadly same amount of tension/firmness?
6) Have you done testing with samples of 10 or 20 to see how often this may appear in a given randomly grabbed set of loaded rounds in that particular load?

 

[Mark1954]

I don’t think you have a scale issue. As far as measuring is it possibe you missed trickling that round? You didn’t give the cartridge or powder/bullet info but I’m guessing it would take around a grain or more to get that kind of spread. That kind of error should be obvious on inspection of the cartridge prior to seating the bullet.

Its possible that neck tension is the problem or it could be chronograph error. What chronograph are you using?

Did POI show significant deviation?

I don’t think you have a scale issue. As far as measuring is it possibe you missed trickling that round? You didn’t give the cartridge or powder/bullet info but I’m guessing it would take around a grain or more to get that kind of spread. That kind of error should be obvious on inspection of the cartridge prior to seating the bullet.

Its possible that neck tension is the problem or it could be chronograph error. What chronograph are you using?

Did POI show significant deviation?

I’m using a LabRadar. Although I’ve failed to observe the velocity for each hit on the target, the group for the velocity data I shared is very tight with one flyer so it’s logical the flyer is the low velocity shot. I’m not sure I can discern one grain out of 35 looking into a 22-250 case. I also agree it’s very unlikely the scale is that far off. I’m light throwing the charge into the scale pan then manually trickling to final weight. I’ll going to repeat the ladder using my balance.

What should I be doing to make the neck tension more consistent?

 

[7mMike]

I’m using a LabRadar. Although I’ve failed to observe the velocity for each hit on the target, the group for the velocity data I shared is very tight with one flyer so it’s logical the flyer is the low velocity shot. I’m not sure I can discern one grain out of 35 looking into a 22-250 case. I also agree it’s very unlikely the scale is that far off. I’m light throwing the charge into the scale pan then manually trickling to final weight. I’ll going to repeat the ladder using my balance.

What should I be doing to make the neck tension more consistent?

Use a mandrel and pin gauges

 

[47guy]

How did it group?

 

[Doom]

If you have the brass identified you can resize as before and then measure neck ID and compare with the others. If it’s different you may need to anneal this brass or cull out the bad stuff. If you have a tight chamber then neck thickness may be an issue, but I doubt it.

I’m not familiar with Win brass in 22-250. Its possible there is a difference in case volume. But again this seems like to much velocity loss for typical lot to lot variations.

One possible explanation for this could be a piece of tumbling media in the flash hole or tumbling media left in the cartridge that interfered with the primer jet.

 

[Dthomas3523]

To many reasons to bother checking.

Load a couple other sets at that charge weight and make sure it’s just something weird.

Could be any number of things with the round or labradar picked up something funny.

As long as you’re not getting some sort of consistent problem, the energy it takes to attempt to figure out that one discrepancy isn’t worth the squeeze.

 

[Mark1954]

Thanks everyone for sharing your thoughts and helping me understand it’s too large a difference to be neck tension or a scale issue. I’m leaning towards Doom’s theory that I left a piece of tumbling media in the flash hole. Dthomas is correct it’s not worth the time trying to figure out a one off.