My latest S.W.A.T magazine tested a wilson 1/9.Results 100yd W/75gr Horanady 7/8in.
My latest Guns& Weapons tested a Rock River 1/9.Results .67.I'm still waiting for my 75gr so i can see with my guns,but it seems like the chances of working well With a 1/9 are better than what some would have us beleive.Especially since hornady 75gr tap is being marketed with stats using a 1/9 bushmaster as i have mentioned in the past.

The most accurate factory load is the Hornady 75 BTHP Match in my RRA chromed lined 16" with a 1:9 twist.

Big Al

I have no doubt that many 1-9" twist rifles will shoot excellent groups with 75gr TAP rounds, but there are many that will not.  

For example, I have both a Bushmaster 16" HBAR and a 16" M4 complete upper receivers that will not hit a 10" wide by 3 foot tall steel plate a 100 yard with any kind of consistency.  The same two uppers will never miss with Q3131a, XM193, IMI193 or Black hills 68gr OTM rounds.  On the other hand I have a Bushmaster 14.5" upper with 1-9" twist that will print 2" groups with 75gr tap rounds at 100 yards.  So in conclusion there is truth to the ideal that 1-9" twist MAY not be adequate to stabilize the 75gr TAP round.

The Azalin

Azalin,
It sounds more like either your barrels need a good coppery scrubbing (my 14.5" did before it would shoot the 75gr correctly), OR there was somethign going on during manucaturing and they are closer to 1:10 than 1:9.

Have you checked the twist rate of those non performing barrels?

Both barrels are obviously marked 1-9, but since the actual twist rate can vary slightly how can I check the twist rate for myself?

The Azalin

Put a jag on a cleaning rod and put a tight-fitting patch on it.  Start the patch into the rifling and make a little mark on the cleaning rod.  Push the rod in, and the mark should rotate out of sight as the rifling turns the patch.  When the mark is back on top, you've made one revolution.  Measure how far the rod has gone in.  If it's gone in 9 inches, it's a 1/9 twist, 7 inches, 1/7 twist, etc.

It helps if you put a piece of paper on the workbench under the rod; put a little mark on the paper at the point where you first mark the rod, and then mark the paper again at the point where the rod mark comes back to the top.  Then measure between the marks on the paper.