I got a secand-hand custom Contender barrel in 6mm TCU. IT's a Virgin Valley 14" fluted with what appears to be a 1 in 9" twist. I had intended on using this barrel for varmint hunting using 55gr to 70gr bullets. What is the effect of too much twist on light bullets? Is this barrel useable for this purpose? or will I have ot stay with 85gr or above? What are my limits?

Within reason, you can't overstabilize a bullet, but you can certainly understabilize one. The 1:9 is a terrific twist for the 6 TCU. Most of my small 6mms have had a 1:10 and one had a 1:9. Accuracy with lightweights was never a problem, although I must add the majority of my shooting with the little sixes centers around the 80 grain bullets, esp. the Sierra SSP. But I've worked up loads with the 55, 58, 60 and 70 grainers, and assembling accurate loads has never been a problem given a good barrel.

Skid, I owned a bullberry 21" tcu in 12 twist.

It shot well with 70's and 85's. Worked ok with 85's but if I did another, it would be at least 10 and likely an 8 twist. I shoot 8 twist in 6BR rifle-26" and it shoots great with 70's.

Unless shooting a bench gun, I always felt a lot of 'writers' are overly concerned about OVER stablizing bullets.

I have NEVER wished for a SLOWER twist in any rifle/pistol. On the contrary.........there were times i.e. 260's with 9 twist that NEEDED an 8.

Enjoy, it will do great, esp. at the pistol velocities you will be shooting.

double check your 6mm barrel from VVCG. Most I have encountered were 1-10.....mine is a 1-10 and shoots 58 gr. v maxs into spectatular groups. They are 'prairie dog accurate' to 400 yds.

Just ordered a TC factory 6 TCU barrel with the standard 1:10 twist. Hope it will stabilize 90s.