How do you get harder, fuller buds?

You should be able to take any F line (including F1) from any reputable place and get nice, dense nugs. Saying that we don't have this naturally is just not true, that would be like saying 'the market underground never converged on THC dominance as primary'...in the same way, dense cali style nugs were bred into just about everything by selection. Now folks foxtail on purpose, and look for looser strains, specifically for washing. So genetics is taken care of, as long as you get good seeds. proper DLI and proper steering is required for completing this as it would be at a dispo craft style... 90% genetics, remaining 9% is lighting, and 1% making sure you don't have a hormonal imbalance likely due to pgrs....

Genetics 100% Agree with what Fruitgrower said. You can also cheat and use PGR's but I would not. Fishy stuff.

Firstly genetics, reputable suppliers producing solid strains. Indica/hybrid varieties more dense than sativas too. Secondly, enough light at the right spectrum. Third, soil, light, aerated and plenty of it. Fourth, nutrients, applying the correct ratios of n at the beginning and PK during flower and making sure to provide a form of calcium and magnesium to facilitate these nutrients better. Fifth would be plant training and defoliation, Training your plants to use as much light as possible, trimming the branches from lower down that would only ever make an airy half gram of bud (lard). Taking off big fan leaves throughout the flowering phase to slow light to penetrate down and below. Sixth would be , fans, cannabis is wind pollenated so the more " wind" your indoor plants receive will produce bigger flowers. Now I'm sure you're doing most of these things, but if there's something here you suspect you could do more off, give it a try!

A plant's developmental blueprint is shaped by both its genetics and its environment. Genetics provide the inherited instructions, while environmental factors like sunlight, temperature, water, and nutrients influence how those instructions are expressed, a concept known as phenotypic plasticity. This interaction results in the plant's final structure and function. Instruct the plant to create 3x as many flowers on the same stem, increase density. Reduce internodal spacing, temperature itself has alot to do with how the nugs develop too. Turgor pressure. Don't feel bad though, 95% of those rock hard McDonald's cheeseburger looking nugs you see are almost always using PGRs to achieve the look.