Best bullet weight for 1/9 20" barrel

[jbmi]

I have a Colt H-bar, 20" 1/9. Been shooting 5.56 55gr. Tactical XM193, not the greatess groups. Tried some Black Hills 223 50gr.V-Max and got some really nice groups, but they sure do cost a lot more.
What would be a good bullet, (weight) for just all around plinking with decent accuracy?

[Baedarlboo]

Every gun regardless of twist seem to have their own "favorite" round. How far are you trying to "plink" out to? Your job is to try different rounds and figure it out. If you like tinkering, you'll get better results by reloading your own ammo and trying different powder, projectiles, powder, case length, bullet depth....ect :D

[saddlerocker]

Military ball ammo is just not accurate, its probably not the weight.
55gr is right in the sweet spot for a 1:9" twist

I would try some better 55gr first, even if its just some cheap Federal or Fiocchi or PMC. Try some commercial .223 ammo, I think itll be better than XM193

[shootist~]

The Colt 20" 1x9 I had in the '90s loved B.H. 68 gr match and shot IMI M193 to 300M almost as well.

[kmrtnsn]

Back in the day, my 20" HBAR 1/9 loved the Black Hills 68gr BTHP.

[Frens]

my colt 16'' barrel with 1/9 likes 69gr match ammo for accuracy...for plinking I just use any 55gr FMJ ammo, mostly S&B

[markm]

+1 to the 69/68 grain suggestion.

[Todd.K]

I have a Colt H-bar, 20" 1/9. Been shooting 5.56 55gr. Tactical XM193, not the greatess groups. Tried some Black Hills 223 50gr.V-Max and got some really nice groups, but they sure do cost a lot more.
What would be a good bullet, (weight) for just all around plinking with decent accuracy?

I think you already answered you own question. It's ammo/bullet quality, not bullet weight that is giving you poor accuracy with the XM193.

You can try some different makes of ball ammo, while I wouldn't expect 62gr ball to be more (or less) accurate than 55gr ball you may find something that shoots better.