Losing gas checks and I don't know why

[quack1]

Was out shooting Lyman 225462 and 225438 in a new to me 222. First time for cast out of this gun, I was running some loads over the chrono to get a general idea of where to start load development . After a couple groups, the chrono stopped registering the shots. Brought it back to the bench and took a look,and found out at least 4 gas checks had come off and hit it. Three of them hit the plastic screen I put in front of the display screen to protect it, and one hit the back screen and knocked a piece of plastic off the inside of the black case holding the rear electronics (it didn't penetrate completely). The piece of plastic was right on top of the sensor, blocking it from seeing the bullet.
What puzzles me is, I have shot those very same bullets through my 22-250 and 218 Bee and as far as I can tell, the checks stayed on them, or at least never hit the chrono. I was using the same box of checks, sizing the bullets to the same size, using the same lube and alloy, having about .002 neck tension on the bullet and seating the bullets so the check was completely in the neck for all three guns.
Any ideas why the 222 is shedding checks and the 22-250 and Bee never have?

Edit: I was shooting at 50 yards and didn't have any extra holes in the target, so I'm guessing the checks are coming off at, or very near the muzzle.

[JeffinNZ]

Possibly a quirk of the rifle. My first Chrony was put out of commission by an errant .22 GC many years ago. Providing they are grouping OK I wouldn't worry too much.

[Cowboy_Dan]

I don't know if the twist of the rifle would matter, but they are probably different. Also velocity and barrel length may or may not be a factor. I wouldn't worry about it unless it hurts accuracy, just protect that Chrony.

[243winxb]

Rough throat/leade would be my guess. Give it a good brushing.

[HangFireW8]

The 222 has a nice long neck, and is as cast-friendly as a .224" bore gets. Besides the rough throat possibility that 243winxb mentioned, you might have the Deadly Donut in your brass (thicker ring of brass at base of neck)... kind of unlikely, but at least eliminate that possibility.

I would measure the bases of some unchecked boolits from that batch, and compare it to other batches. You may have some slightly undersized bases in those batches.

[quack1]

Good suggestions, thank you.
Answers to some questions- All 3 guns have 24"barrels, the 222 is a Sako L 46 1-14" twist, the 22-250 is a Mauser with a Shaw barrel 1-14" twist and the Bee is a Model 43 Winchester 1-16" twist. The 222 barrel was given a good brushing while removing all copper prior to starting with cast, and has no visible erosion or roughness. The 222 and 22-250 barrels measure within .0005 of each other when slugged. The Bee is smaller at .2236. The 222 brass was once fired in this gun.
Both types of bullets are from the same batches currently being used in the other two guns.
The comment about the throat/ leade got me to thinking-there isn't any visible roughness, but, what about a sharp vs shallow leade possibly making a difference? Going to dig out the cerrosafe and make a casting of the throat/leade of all three guns and compare.
Also, I don't know if both bullets were shedding checks or just one. I shot a few of the 225462 first and was shooting the 225438 when the chrony quit. Also, I don't know if all the checks are coming off or if some are staying on. Best to have them all do one or the other. I'll need to shoot some more to find out, but it probably won't be until next week, woke up to 2" of snow with wind today and supposed to get 1-3" more tonight. Not exactly the best shooting weather.
Last of all, I am going to protect the chrony, it's already living on borrowed time. A tumbling pistol bullet took out a corner of the rear sensor unit years ago. Didn't kill it, and with some duct tape, a small piece of aluminum and a couple of screws, was back in business. Until I get the check problem figured out, load development will be without chronographing, just like the first 30-40 years of my shooting addiction.