2 out of 10 rounds ~50FPS off

[FFAZ]

I'm trying to resolve/identify why 1 or 2 rounds out of a 10 round string would absolutely trash an otherwise great SD/ES for my .308. Using a Magnetospeed v3.

Heres my data from two 10-round strings:

String 1
SD: 24
ES: 79
String 2:
SD: 19
ES: 60
2 rounds in both strings were WAY off, one much faster, one much slower.
If I remove those two from the math, I'm damn near single digit SDs and ESs below 20.


Here are my components:

• Alpha Brass (once fired, and annealed)
• Federal match primers
• Sierra matchkings
• RL15
• neck tension: .0025-.003.
• Primer pockets uniformed and flash-holes deburred.
• .015 jump

I'm using an RCBS chargemaster lite. I have always had a hunch that its the problem. So what I did was weigh all my primed cases, record. Then throw the powder, weigh the case plus the powder, and then see if the scale was at least consistent. Seemed so... However, this does nothing to check the precision of the scale.

What is the likelihood that its simply the margin of error of my scale? its not the most top-of-the-line, and since it says +/- .1gr, I would think that could make a significant impact...

I have been told to try different primers, perhaps CCI BR... Can a primer really make a 50 FPS difference?

What else could it be?

 

[hafejd30]

My first suggestion would be primers as well. I’ve personally had better consistency from CCI 200 or BR2 vs Federal

 

[Maurygold]

I would also try a different primer I already shoot magnums regardless of magnum caliber or not. Ignition can make a big difference. I’d also weight my bullets if using Sierra and make sure you don’t have problems there. If that doesn’t work change the load you could be outside the optimal node. Lastly I’d change powders I’m not a Alliant fan and would shoot either hodgdon or vitavhouri but others may have good things to say about alliant

 

[FFAZ]

I would also try a different primer I already shoot magnums regardless of magnum caliber or not. Ignition can make a big difference. I’d also weight my bullets if using Sierra and make sure you don’t have problems there. If that doesn’t work change the load you could be outside the optimal node. Lastly I’d change powders I’m not a Alliant fan and would shoot either hodgdon or vitavhouri but others may have good things to say about alliant

I've been working through my load development process with these "flyers" present. I've already tweaked my seating depth, charge weight, neck tension, etc. I'm shooting under or around half-minute groups at 100 but I don't feel comfortable pushing this gun out long range with those numbers. That being said, thats +2 on trying different primers so I'll have to search around...

 

[Maurygold]

Are you monitoring velocity for the whole load work-up process? What chrono? The best group on paper may not be the best on chrono are you seeing flyers on paper?

 

[Brettmparker1]

Magneto speeds are good chronos but I would run that against another one if you have access. The charge master light is a good scale. Accurate enough for good sd/es but also you could be right your scale could be fucked.
I had some issues with my LabRadar awhile back it was clocking the first shot of every string 50 ish feet higher than the rest I have no idea why but it came out of it after I reinstalled firmware, and tweaked some settings. I was confused as shit too on cause of that big of swing with a known load. Good luck with it I hope you figure it out. Above are good suggestions too.

 

[FFAZ]

Are you monitoring velocity for the whole load work-up process? What chrono? The best group on paper may not be the best on chrono are you seeing flyers on paper?

Using a magnetosphere V3. This load groups very well and has good numbers minus those 2. The thing is I've ALWAYS had this problem with a couple rounds

 

[Maurygold]

Using a magnetosphere V3. This load groups very well and has good numbers minus those 2. The thing is I've ALWAYS had this problem with a couple rounds

Have to wonder if it’s a magnetospeed issue it would be worth trying a second form of chrono to verify. I’m not a fan of looking at sd/ es while changing barrel harmonics (ie strapping a magneto to barrel). I’ve shot over chronos a lot and can tell you strapping something to your barrel matters but not so much for what you’re seeing.

 

[hafejd30]

Using a magnetosphere V3. This load groups very well and has good numbers minus those 2. The thing is I've ALWAYS had this problem with a couple rounds

Are those couple rounds the same brass? Same lot or even same pieces each time?

I run Lapua brass for my 308’s

But personally I let my target dictate how my gun shoots and don’t pay as much attention to the numbers

How do these rounds with high/low FPS compare on target to the others at longer ranges?

Take it out further and let the rifle tell you what it likes

 

[Emerson0311]

it's the shooter not the gun not trying to pic on your but if 9 shots are fine and the 10th trash you messes up maybe you got excited , lost considerations , broke your rhythm , pulled the trigger when you should have restarted your shot process . taken a break , walked around used the can what ever it was other than pulling the trigger . flyers are an all the shooter thing like not taking notice you changed something . you can do it rinse and repeat .

Would that change the chrono’ed velocity 50FPS?

 

[Brettmparker1]

Would that change the chrono’ed velocity 50FPS?

Recoil management can change your velocity

 

[Emerson0311]

Recoil management can change your velocity

Maybe holding around a corner or something, vs solid on a bench. Easy to test when there is a chrono there. When I shoot my 44 Blackhawk standing, will my velocity be off by 50 vs the bench?

 

[FFAZ]

How do these rounds with high/low FPS compare on target to the others at longer ranges?

Take it out further and let the rifle tell you what it likes

Same lot and batch of cases. My groups are around a half minute or so, but to be honest I didn't look at where each progressive shot went because I lose my consistency when I break my position. That being said, I probably should take her out to a longer range to see if the numbers are angering me for no reason

 

[Dave62677]

Primer seating depth is the last piece of puzzle I solved with my load. I test 5 rounds with .004~0.005 primer depth result with 35 ES. Other 5 rounds with .002 primer depth got me into 12 ES.

 

[Dave62677]

Here is what I do and got some positive result.

I do monitor my seating force (I’m using arbor press) , my best result is around 70-80 in/lb seating force. I dip the neck with imperial dry neck lube before seating the bullet. I do also resize my neck .004 under, then open back up .002 with expander mandrel. Did I over work the brass? Yes, maybe but I do anneal every firing. I loaded my brass 8x without any issue. I do inspect each of my brass before dropping in my charge. What work for me might not necessary work for you, but you can always keep that in mind. Hope this help. Enjoy and be safe.

If nothing work for you, check your firing pin spring

 

[RegionRat]

Food for thought...

You didn't mention the rig you are using? New to you, or old reliable?

Has this rig ever had a brand or batch of ammo where it had a low ES?

Have you tried anything like a reference ammo that you know plays well?
Maybe some FGMM just for a baseline to help eliminate the bolt and chamber's share of the ignition issues?

No copper fouling or severe carbon fouling?

Check the bolt and firing pin?

A "normal" string SD would show an estimated ES that is 6X with enough samples to develop the Bell Curve.
To be a flyer, a value will run more than 4 sigma away from the average. Otherwise it is just a wide Bell Curve.

You would need enough samples to get a more clear picture of the shape of the Bell Curve versus the flyers to know.
Having the extreme at both the high and the low, instead of always a high or always a low is also a clue.

There is a share of possible ignition issues that can be caused by the gun, and a share that can be caused by the primer.
Next in line is the tune of that recipe. Some powders and bullet weights don't play well together regardless of the ignition.
Some primers and powders don't play well together in colder weather.
Then there can be issues from things like variable neck tension, galling, barrel friction due to fouling, etc., that can affect an otherwise good recipe.

Hope you root it out.
Good Luck.

 

[Doom]

As for the chargemaster, that is the last place to look. In 308 you can figure a tenth of a grain is worth about 6 fps.

 

[KZP]

I stopped messing with deburring flash holes a long time ago. Caused me problems like this. Could be unrelated in your case, but if you have some brass where you didn't mess with them, might be worth trying a few more strings to compare.

 

[FFAZ]

Alright Gents, after sleeping on it, I came to some obvious but stupid conclusions.

It's cold right now in UT, and I looked over my data book. Late summer and fall when I discovered my velocity node and tuned my seating depth, I was getting single digit SDs and low ES, plus grouping well. My MV avg was 2684. It was between 60-80 degrees those range days.

My current MV avg is 2590 with temps in the high 30s and low 40s. Obviously RL15 is very temp sensitive, so does that mean that in the winter, I've dropped out of the node?
Temp affects MV so should I expect to drop out of the node when I'm almost 100fps slower than my "sweet spot"?

 

[KZP]

Did you have some rounds that were at the car's temperature, not yet at ambient temperatures, then fired with some ambient temperature cold rounds in the same string? Or had let them all get cold, one sat in the hot/warm chamber getting it well beyond ambient temperatures of the other rounds when they were fired?

 

[Dead Eye Dick]

Me, I always verify loads that were thrown with telectronic powder scales. If purchasing and using a quality beam scale to verify the charge is too much money, get a set of scale weights and verify the scale every ten rounds. I may be old fashioned, but I have seen the electronic scales drift more often than not. Seen, with my own too eyes and with a verified beam scale.

 

[FFAZ]

Did you have some rounds that were at the car's temperature, not yet at ambient temperatures, then fired with some ambient temperature cold rounds in the same string? Or had let them all get cold, one sat in the hot/warm chamber getting it well beyond ambient temperatures of the other rounds when they were fired?

Good question... I kept all the rounds with me outside with my gun. I always let my cuber cool 2 minutes or so before my next shot. I don't let rounds warm up in the chamber any longer than a few breaths before my next shot

The fps isn't slowly increasing or decreasing through the strings so that would indicate (to me) that it's not the gun or ammo temp.

 

[gigamortis]

I was running myself ragged when doing load development with my new to me at the time 6.5CM. I run the Magnetospeed Sporter. My .308 load was always single digit SDs. My 6.5 had reported wide ES and SDs issues that were maddening, but the tight waterline on 800 yard targets suggested single digit SDs was the reality. I bumped up the sensitivity on my Magnetospeed one increment, and my reported SDs became single digit, which logically matched up with the tight waterline at 800 yards.

My .308 load is a Berger 175gr OTM. My 6.5 load is a Berger 130gr AR Hybrid. My issue was the smaller bullet needed the sensitivity bumped up on the Magnetospeed for consistent reporting. My wife's 80gr Amax .223 load needs the sensitivity bumped up yet another increment for solid reporting.

As far as primers go, I normally run Federal 210Ms or Wolf LRP. Both of those show the same low ES and SDs. I bought a 1000 CCI BR primers and the ES and SDs more than doubled in my 6.5 load. This was verified at the same range visit with identical settings on my Magnetospeed. I don't know if I just got a bad batch of CCI BRs, or the RL-16 powder needs some more brissance than what the CCI BRs provide.

 

[FFAZ]

bumped up the sensitivity on my Magnetospeed one increment

You may be on to something.... I'm shooting suppressed. That would explain why my groups are very tight, but the numbers are janky. The paper doesn't lie.... but the magnetospeed might be acting strange with the can!

I'll give this a try ASAP!

Thanks to you and everyone else, I've got a solid list of things to try.