I am looking at purchasing a stainless 16 inch barrel from Rock River Arms. Does anyone know why they use a 1/8 twist on the stainless barrels and what effect will this have on the use of lighter bullets?  I know 1/9 is best all around twist, but how does 1/8 compare?

I run 1/8 on my DCM rigs.  The barrel works well with 62gr and even better with 68+ when the distance requires it.  

In regards to the 1/8 and the 55gr the twist is too much and seems to destabilize the round; group will open up due to too much spin.

My DCM barrels are 20" barrels, so keep that in mind.   Also, considering that your going with a 16" barrel, and I doubt that the difference is really going to matter unless your planning on running match ammo or floating the barrel.

The other deciding factor will be directly related to ammo. If your planning on using a 5.56 Nato chamber, your going to have a hard time finding a round that will fit into the mag, and still be in correct position/distance from bullet to lands(OAL).  The standard Nato chamber just has too much jump from standard bullet to lands, and if you reload for this ideal relationship, the ammo is never going to fit into the mag.

On one of my practice rigs, I have had the 223 chamber throat enlonged up to allow the use of standard ammo, but this sacrificed the accuracy.  Since the rifle spends it time in others hands, and I don't have to have reloads to run, the sacrifice worked out well.

I guess what it boils down to is what is the purpose of the rifle.  If your not going to use it for a Three gun event, then your best bet will to just buy the barrel with a 1/9 twist and run the 55gr or lighter that will suit the barrel/your purpose the best.

Just food for thought.

Thanks for the info.  The rifle will be an all around weapon, that is I will be using most of the common ammo types.  I still don't understand why RRA is making a 16 inch barrel with a 1/8 twist.  Anyone know of someone making a stainless 16 inch barrel with a 1/9 twist?

Bushmaster www.bushmaster.com/shopping/barrel-assemblies/

Oly makes an M4 contour 16" barrel with a 1/9 twist in Stainless

I agree wi Dano on this.  I used to have a SS Kreiger barrle with a 1/8.  It loved the heavier bullets (62 grn. and heavier) but did not like the anything lighter than that.  I had wanted to use that rifle for some small varmint hunting while using some of the 50 grain softpoint ammo (great for those little critters) but the groups would open up to 2 MOA.

Based on that, I would really suggest the 1/9 for a good overall twist.

CMOS

packinheavy,

 I think the only barrel that Rock River Arms carries that is 1/8 twist is their varmint bull barrel.  Is that what you are looking at?  
 
 The bull barrels being used for long range shooting/target practice and hunting are probably going to be used with a heavier bullet.  The 1/9 twist barrels wouldn't stabilize the bullets as well.

 According to their website all their normal contour barrels have a 1/9 twist.  I may be wrong but this is what I saw.

It may be a mistake, but check the page with the car a4 with stainless barrels.  They state they have a 1/8 twist.  I will give them a call on monday to check.  I hope this is mistake as this is the one I want. Thanks guys.