Rimfire casings split after firing

[MARKFP]

Went plinking with a friend today, he was shooting a Savage 93 bolt rifle in 17HMR. About 7 out of 10 spent cases had problems not ejecting and after closer inspection they had multiple small lineal cracks starting at the mouth of case down the neck through the case bevel and slightly into the body of the case. He's had this rifle about 12 years he said and has run aprox. 15k rounds thru it. He said it started doing this a while back showing light splits first then failure to eject. We ran Winchester, Hornady and CCI ammo through it and all show signs of the splits some worst than others. Could the barrel be worn that bad at the chamber? We did not have a bore light to look at chamber, barrel in general looks ok even with that kind of mileage. All ammo is lead free by request of the land owner whose property he shoots at, I'm not familiar of characteristics of lead free rimfire ammo so don't know if that is common. Obviously this is not high end rifle so he's willing to chalk it up to loss but curious to know what could be cause. Thanks in advance guys for any insight, Mark

['ol shooter]

.17HMR's are known for that. Here is a whole page of complaints.

https://www.google.com/search?client=firefox-b-1-d&q=17+hmr+case+splitting+problem

[MARKFP]

Thank you for the link ol shooter, I had no idea that this issue was that common with that cartridge. Interesting read. Mark

[c good]

Yup....very common....

No worries though. I have an old Savage that has been doing that for years. Still a great shooter.

[FeuerFrei]

If a hmr starts having split cases all of the sudden I'd look to having the headspace checked. Only after ammo has been ruled out tho.

Same for any rimfire that always does it from shot 1.

Send it back to mommy if it's not the ammo. Savage is good about it.