I've tried the same test, 1 polish regiment (1400) against a russion one (1800). Instead of giving the "attack unit" order, I gave the "scout" one.
The outcome was interesting: when the two regiments met in the field, the polish formed a good, long line, while the russian charged with their 3 batallions, loosing nearly 100 men due to the first polish volley (at nearly 150 meters). At 50 meters, the russian halted, fired (without inflicting casualties), but the polish routed.
The same thing happened many times, with the advancing russian suffering casualties but holding, and the polish running away before the bayonette charge. It was all quite realistic, only the russian fire seemed a bit too much ineffective.