Benchmark 2 groove, twist question Help

C

chadflys

Guest
I'm almost there as to decide to buy a used 40x with a Benchmark, 2groove, I think 1/18 twist Benchrest rifle. Is was hard to measure..first I got 1/19, then with a brush I got 1/18. Does anyone know what twist rates the benchmark barrels came in. What I might need to be aware of?

With the Eley match 1060...What was strange was almost all holes were slanted as if the bullet wobbled. Not sure what to think. I know its known as keyholing, as many threads as I have read I still am puzzled as to what causes it. When shot with Wolf match extra nice clean holes..no flyers..better score

I test shot it today at about 42 degrees almost calm wind and shot a 244 4x with eley match 1060 (234 not counting the reshot). I reshot one bull cuz it I missed went out of the box hard at 9 o'clock position....anyway the next test was with wolf match extra and shot a 246 5x...nice clean holes...

the gun has a tuner, but I didn't mess with it...

Any advise is greatly appreciated.

Chad
 
Chad
If memory serves me, most of those were 17 1/2 twist. A year or so ago there were lengthy threads discussing the cold weather keyholing many encountered, along with a variey of reasons and logic mentioned. There were some who felt it was related to the type and amount of bullet lube on the Eley ammo. One fellow claimed he could eliminate it by wiping the lube off the nose of he bullet. That is not allowed in some competitions though. Still would be an interesting experiment.
Don
 
Benchmark offers a range of twists. If yours is an 18, you might have a hard time getting it to shoot in cooler temps. I know of only one guy that shot an 18 with any success in cooler temps.
 
Benchmark

I have a benchmark 16 twist and it shoot well. If I were to replace barrel it would be with 16 twist.
Jim M
I'm located in Northern Pa
 
I just conversed with Gene Davis, the man that built the gun. It was a 17 3/4 twist barrel. He did educate me on the situation. Long story short...............

Eley EPS slightly longer bullet than the older stuff. Tight barrel elongates even slightly more. In the winter the lube slows the twist further as the bullet exits the barrel. Yes causing key holing......I even saw this with my CZ when shooting Eley...CZ barrels are tighter than the Benchmark barrels, thus elongating more and maybe too much..Strange..

Solution:

In the winter or when temps start to drop below 60 shoot round nose ammo with less lube. There are plenty of good one's to choose from. I don't think Mr Davis said wipe off the lube, but I suppose its worth a try.

In the summer shoot away with what ever it likes. Slower twist rate barrels are slightly less affected by the wind. Which is what I need around here. Looks like there have been several records set with the 17 3/4 twist.

Chad
 
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