Weirdness with Lot-Tested Center-X

[DownhillFromHere]

Summary:

• Had my 1st-gen Vudoo tested at Lapua's AZ test center early 2020. Bought 2 cases Center-X. I'm down to three (3) bricks of it.
• Over thousands of rounds, this ammo has averaged ~1080fps with an SD ~7-9, depending on temperature.
• Accuracy is a consistent 1.0 - 1.1 MOA @100, with plenty of 1/2-3/4" groups to be had.
• Then, last month at a monthly gallery-style match, I missed four 100-yard targets. Perspective: to that point, over the last three seasons and 18 matches, I missed a total of 7 100-yard targets.
• I thought my scope (ZCO 527) had crapped the bed... Yesterday I learned otherwise: Every round chronographed in one box of this ammo was 50-70fps slower than the historical average. JUST THE ONE BOX.
• Ammo has been stored in benign HVAC-controlled environment, temp 65-75 F. / humidity 45-55%. Definitely no solvents, WD-40, etc. stored in the same room or even in the same wing of the building.

So today I took the remaining 20 rounds from that "bad" box to the range along with the remaining seven boxes in the brick (two boxes fired at the disastrous match). I tested 5-10 rounds out of each box. None of the rounds tested from the "unknown" seven boxes chrono'ed low; in fact, four box's samples tested about 10-15fps high. After each "unknown" sample, I fired a couple of rounds from the "bad" box - all of which were 50-60fps slower than historical average.

Lessons learned:

• Before using the remainder of this lot-tested Center-X in competition, I will test five random rounds from each box.
• In fact, from now on, I'll sample a few rounds from every box from every lot I ever buy again before competing with them.
• I'll only buy one case after the next test session. Given the "profile" of how these weird rounds presented, I doubt that the ammo's age is the cause of these two boxes (from the same brick) having such low velocity. (Note: I shoot a lot of SK ammo to save the lot-tested stuff.)

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Anybody else ever experience anything like this? I've seen some puzzling things in six decades of shooting, and this one is brand-new!

 

[Defender32]

This is the RimFire Lottery. Even though its lot tested it does not mean every box will be the same. If you had gotten 2 rounds of the bad 50 spread across 25 bricks it would have never crossed your mind. It's just a random thing it happened in 1 box.

doing what you say of pulling random shells from each remaining box in bricks and testing is all good and within reason. Just check it morning of your matches.

Id say you are lucky to have 2 cases last 4 years. I'll shoot almost 2 cases a year.

 

[DownhillFromHere]

This is the RimFire Lottery. Even though its lot tested it does not mean every box will be the same.

I'm well aware of the rimfire lottery... there has been "a lot of lots" of other ammo down the tubes (Vudoo, Rim-X) besides the Center-X. As well as my C-X lot shoots, there have been the random rounds that drop a few tenths low at extended ranges (>150 yards).

I'm still finding it hard to believe that I have an entire box, plus at least part of another box, from the same brick (out of 20 bricks purchased) that are so consistently slow. And when I say "consistently" - I'm talking similar ES/SD numbers to the rest of the lot, just 60fps slower. IN ONE BOX.

With that said... over the last four years shooting that little gallery-style match, the season points races have come down to the same handful of shooters running Vudoos and one guy with an Anschutz. The smallest targets on the 150-yard racks are just over 2 inches wide, situated in a corner of a square range with berms immediately behind and beside. Wind swirls around those berms, which are covered with brush (essentially no splash). Only one of those guys runs SK ammo; I run C-X, another ran Midas+ but has moved to Lapua Long Range. The Anschutz guy runs nothing but X-Act. We're all within a target or two of each other on any given match day. The high-dollar labels aren't doing notably better than the mid-range stuff.

 

[justin amateur]

I hear y'er complaint Downhill.

It ain't news to me.

I've had issues with supposedly match quality cartridges from RWS, Lapua, Eley and Fiocchi Italia.
Chrony spread in excess of 40 fps for a box of 50. Odd strays that don't fit wind direction/speed.
I was told my rifle didn't like the brand, or I was at fault as high end 22lr doesn't have those issues.

Nope, just less than desirable quality cartridges rolling off the assembly line.
Or cartridges that had shipping/handling problems before delivery.
Statistical sampling at the factory doesn't catch all the problem cartridges.
The factory has acceptable defect rates per 100,000 units and a sampling confidence level
that allows lesser quality cartridges to end up in consumer hands.

Remember the problems with Eley's recent long range 22lr?