VV N340 is not an ideal powder for reliable cycling of an AR, the burn rate is too fast. N110 is very comparable to H110 but not as temperamental and N133 is pretty close to AA1680.
That being said I'm assuming that you simply have some on hand and want to use what's available...the usual liability waivers and disclaimers apply:
According to a mock up in QL:
168gn HPBT
2.10" OAL
6.6gn of V340 nets 64% case capacity
1220 fps from an 11" barrel
As a best practice I would not reduce this load below 50% case capacity which is about 5.2 grain.