Years ago I experimented with Viht N310 and Hornady 148 HBWC. They were impressively accurate but very sensitive to the load. At 2.7 gr, they worked great. Much higher and they started to wobble much more than with Bullseye. I suspect pressure spikes much more quickly than with Bullseye.

I have never used N340, so I don't know if it behaves the same, but you might try reducing the load and see if the bullets stabilize.

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