I would venture to guess it wasn't the free bore or lead length.
If that was the case, you would certainly have a little resistance closing the bolt but not much.
That condition would also likely result in you pulling the bullet if you tried to remove a round already in the chamber.
If it didn't pull your bullet, you would have certainly noticed serious rifling marks engraved into the bullet's ogive.
Additionally, "most" barrels are chambered with reamers that cut the chamber, lead and throat at the same time. All 3 of those features are built into the reamer so it would be almost impossible to accidently get a short free bore but very easy to miss the headspace.
I would have guessed it was more likely a simple case of short headspace.
This condition would make it difficult to close the bolt on a round and would not leave much, if any signs of the conflict on the round if examined.
Regardless of the issue, MHS is top notch and will get you squared away.
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