Heating a barrel can cause it to warp a bit, but even if it doesn't touch the barrel channel, the barrel whips when fired, so some heavier hunting calibers need at least 1/16" of clearance at all times. Most rifles don't have that much clearance from the factory, some are bearing at some point along the channel.
In this particular case; however, barrel fouling may be the culprit. Barrels are more likely to foul when new, especially if heated too much.
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