Help needed in diagnosing bullet speed variations

[Fairchaser]

I shoot FTR and have a pretty elaborate process for loading. My SDs average about 5-6 fps as measured by a garmin Chronograph but the ES might be 25 fps. My most recent MRP match 3x600, I dropped 5 points and 3 of those I could trace back to speed anomalies.

Where would you start looking for the cause of these speed fliers? Sometimes they are too slow 15-20 fps and sometimes too hot. That’s enough to leak one high or low.

I use all the expected components and equipment and even point bullets but I don’t weight sort my Lapua SRP brass or weigh sort primers. Is that what I’m missing or is it a tuning issue?

 

[Fairchaser]

Powder charge inconsistency
Neck tension ( too light maybe )
Primer weight extremes
Maybe the receiver doesn’t like the current primer
Weak firing pin spring
Seating depth might be off a tad bit causing fliers

Why point bullets for mid range ?

I weigh to the kernel.
Neck tension is 40 and I sort out anything outside of 40-42.
Primer weight?? CCI BR4.
I change springs every barrel change 2000 rds
Seating depth is 10 thousand past touch. Bullet is always touching the lands.
I point bullets because everything matters in this competitive environment even at Mid-Range.

Thanks for the feedback!

 

[Straightshooter1]

I shoot FTR and have a pretty elaborate process for loading. My SDs average about 5-6 fps as measured by a garmin Chronograph but the ES might be 25 fps. My most recent MRP match 3x600, I dropped 5 points and 3 of those I could trace back to speed anomalies.

Where would you start looking for the cause of these speed fliers? Sometimes they are too slow 15-20 fps and sometimes too hot. That’s enough to leak one high or low.

I use all the expected components and equipment and even point bullets but I don’t weight sort my Lapua SRP brass or weigh sort primers. Is that what I’m missing or is it a tuning issue?

IMHO, sorting brass and sorting primers by weight can really help identify outliers that can make that kind of difference you're mentioned. For sure, it can't hurt, and if it doesn't help, then at least you've eliminated this as a cause so you can look elsewhere.

BR4's are supposed to be pretty consistent, but until you weight them, you really won't have a good idea of just how consistent.

 

[JFrank]

@Fairchaser
Pardon my deletion, I’ve been trying to reframe from posting, now that I’ve opened my big mouth I’ll just finish this thought.

For my game I weigh primers and shoot the bell curve together, the extremes are fouler’s and sighters.
It makes a difference on my 1000 yard targets.

( I sort cases also but use a different method )

Jim

 

[jackieschmidt]

Just curious, if you drop back to 200 yards, and taking your time and shoot a 10 shot string, what would your actual spread be. Not MOA, but actual measurement.

I ask because last spring, a fellow club member who had just got a FTR rifle and was having a similar problem. He was tuning by ES and SD, and the numbers were pretty good. The problem was it was shooting 1 1/4 groups at 200 yards.

We worked with his load, found a seating depth that it really liked, and got the rifle shooting nice round 1/2 to 3/4 groups at 200. We were shooting over my flags.

But The ES and SD were not that good. I suggest what @Straightshooter1 said to do, keep the same load and seating depth and star sorting the cases, weighing the primers, and weight the powder closer than .1 grain.

I have not seen him since, so I don’t know how it came out.

 

[Doom]

I shoot FTR and have a pretty elaborate process for loading. My SDs average about 5-6 fps as measured by a garmin Chronograph but the ES might be 25 fps. My most recent MRP match 3x600, I dropped 5 points and 3 of those I could trace back to speed anomalies.

Where would you start looking for the cause of these speed fliers? Sometimes they are too slow 15-20 fps and sometimes too hot. That’s enough to leak one high or low.

I use all the expected components and equipment and fps SD means you have even point bullets but I don’t weight sort my Lapua SRP brass or weigh sort primers. Is that what I’m missing or is it a tuning issue?

A 5-6 fps SD will mean that 95% of your rounds will fall within +/- 2xSD or +/-12 fps of the mean velocity. That means 5% will be >+/-12 fps or 24 fps ES. About .7% will be 30fps or more. It pretty unrealistic to expect better than 5 fps or even to accurately measure it.

The source of the variation is due to the various items that change with each round (case,bulllet,powder, primer, neck tension, etc).

 

[mgunderson]

5 to 6 fps sd is outstanding in a 308! It is a tuning, wind, or gun handling issue. What bullet. Have you tuned the jump at distance?

 

[FeMan]

I have the same thoughts as Jackie and mgunderson. My 284 F-class rifle will hold the X ring at 1k easily but has an ES of 45 fps. I tune at 800 yards though. My vertical flyers are almost always related to gun handling.

 

[ShtrRdy]

Interesting information here.

 

[Fairchaser]

As you can see below, shots 11 and 12 correspond to shots 9 & 10 on target due to sighters. The speed on 11 was high and shot 12 was low speed resulting in a high shot and low shot on target. I agree had my wind call been better on shot 9, it wouldn’t have mattered but it did.

What’s also troubling is these two were back to back which could rule out loading errors and tend more toward gun handling. Can shoulder pressure cause this much speed variance? Something to test.

 

[Fairchaser]

A 5-6 fps SD will mean that 95% of your rounds will fall within +/- 2xSD or +/-12 fps of the mean velocity. That means 5% will be >+/-12 fps or 24 fps ES. About .7% will be 30fps or more. It pretty unrealistic to expect better than 5 fps or even to accurately measure it.

The source of the variation is due to the various items that change with each round (case,bulllet,powder, primer, neck tension, etc).

Agree 100%. It’s the .7% which is the 9 that loses the match. Thanks for putting it to the numbers.

 

[Fairchaser]

I have the same thoughts as Jackie and mgunderson. My 284 F-class rifle will hold the X ring at 1k easily but has an ES of 45 fps. I tune at 800 yards though. My vertical flyers are almost always related to gun handling.

I tune at 600 yds and shoot for 1/4 MOA for 5 shots in ideal conditions. Usually these fliers don’t show up in practice but only during matches with 60-80 rds and then only 1-3 shots. So, it’s hard to pin down. Thanks for your helpful input.

 

[222Jim]

I shoot FTR and have a pretty elaborate process for loading. My SDs average about 5-6 fps as measured by a garmin Chronograph but the ES might be 25 fps. My most recent MRP match 3x600, I dropped 5 points and 3 of those I could trace back to speed anomalies.

Where would you start looking for the cause of these speed fliers? Sometimes they are too slow 15-20 fps and sometimes too hot. That’s enough to leak one high or low.

I use all the expected components and equipment and even point bullets but I don’t weight sort my Lapua SRP brass or weigh sort primers. Is that what I’m missing or is it a tuning issue?

I often get velocity high/low "weird ones" when I'm within +/- 0.0030" of touching the lands. After a lot of research I learned that's due to a combination of small errors including minor case base-to-datum variations, bullet inconsistencies, etc. and static vs. dynamic bullet engraving forces altering the shot start initiation pressure.

 

[JFrank]

I don’t put a lot of value in ES/SD beyond loading practices simply because it doesn’t mean errant shots.
As you can see below the ES is terrible but the rounds POI is good.
If you’re looking for weird stuff to eliminate ,
FPS sorting doesn’t take much effort to chart the cases that display odd speeds and just set them aside for further testing.

 

[AlNyhus]

I ask because last spring, a fellow club member who had just got a FTR rifle and was having a similar problem. He was tuning by ES and SD, and the numbers were pretty good. The problem was it was shooting 1 1/4 groups at 200 yards.

We worked with his load, found a seating depth that it really liked, and got the rifle shooting nice round 1/2 to 3/4 groups at 200. We were shooting over my flags.

But The ES and SD were not that good. I suggest what @Straightshooter1 said to do, keep the same load and seating depth and star sorting the cases, weighing the primers, and weight the powder closer than .1 grain.

I have not seen him since, so I don’t know how it came out.

One of our local shooters was having trouble with his 30BR VFS gun. It's a well built gun with all the right parts to be competitive. The shooter came to the short range game from the PRS world. At the range, he had his LabRadar set up and was tuning at 100 yds using the ES/SD numbers.

I didn't think a good 30BR could be made to shoot as bad as that gun did.............

 

[LCazador]

Have you checked your sizing die bump and brass springback? Are you getting clikers on that brass that shoots a 9?

 

[Fairchaser]

Have you checked your sizing die bump and brass springback? Are you getting clikers on that brass that shoots a 9?

No clickers! I’m using the slower node. But that’s a good thought. I run the sizing die twice and dwell for 2-3 seconds. I usually eject into a tray before I know the impact so I don’t keep up with the brass. Maybe I could do that during practice to eliminate outliers. Thanks for your input.

 

[L.Sherm]

I can remember loading for my 30-28 when it was first built trying to find pressure and shot 3 shots all same charge that were 3201FPS and was the worst 3 shots I have ever shot through that gun

 

[FeMan]

I tune at 600 yds and shoot for 1/4 MOA for 5 shots in ideal conditions. Usually these fliers don’t show up in practice but only during matches with 60-80 rds and then only 1-3 shots. So, it’s hard to pin down. Thanks for your helpful input.

I spent a year shooting paper at 1k strictly to practice gun handling, see what worked and what didn't and get consistent. I shot 3, 20 shot strings twice a month. It took a while but I got to the point that I could call the vertical flyers as soon as the gun went off. Once I could do that I could eliminate (well almost eliminate) them. The biggest factor was inconsistency in shoulder pressure followed by cheek weld variances. its amazing how little you have to change things to throw a 9!

 

[Codyway]

As you can see below, shots 11 and 12 correspond to shots 9 & 10 on target due to sighters. The speed on 11 was high and shot 12 was low speed resulting in a high shot and low shot on target. I agree had my wind call been better on shot 9, it wouldn’t have mattered but it did.

What’s also troubling is these two were back to back which could rule out loading errors and tend more toward gun handling. Can shoulder pressure cause this much speed variance? Something to test.

Looking just at your target, you got a change in wind on shots 7-10. It settled down and it tighten back up. That's how it goes shooting ftr.
A head or tailwind will give me vertical big time.