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Old 05-23-2013, 07:17 AM   #1
Rifleman
 
Joined: Nov 2009
From: Graham, Wa
Posts: 240
Comparison of barrel twist to bullet weight

Just an interesting look at how different bullet weights perform out of the same barrel. This is obviously not an exhaustive list, I was just playing around with some loads. 3 bullets: Hornady 55gr VMAX, Hornady 60gr VMAX, and the Nosler 77gr Custom Competition HPBT. All are loaded in once fired NATO brass, loaded to 2.26 OAL with Remington 7 1/2 primers and Hodgdons H335. I haven't tested the powder charge or tried to perfect the jump to rifling. I just chose a "middle of the road" charge and shot. I also have a box of Berger 70gr VLDs that I wanted to include, but I haven't quite figured out the details on that load, so I didn't shoot them.

Rifles used were a 16in, 1/7 stainless FN barrel (ST), and a 20in, 1/8 heavy match barrel (RG). It was drizzling a bit, and right at 55 degrees. 100yds.

ST, 55gr VMAX, 25.5gr H335. 1 3/4 inch.



ST, 60gr VMAX, 25gr H335, 1 3/4 inch.



ST, 77gr N-CC-HPBT, 23.5gr H335. Less than 1/2 inch (!!)



RG, 55gr VMAX, 25.5gr H335. Just a hair under 1 inch. Ignore the holes to the far right, just the holes bracketed by the marker.



RG, 60gr VMAX, 25gr H335. Over 2 inches.



I shot the 77gr N-CC-HPBT out of the 20 inch 1/8 barrel, but my groups were too big to get a decent picture. My groups were in the neighborhood of 6-8 inches. You can see that the rifle really liked the 55gr bullet, and then really started opening up on the 60gr. This confused me as a tighter twist like the 1/8 should love heavier bullets, and over stabilize something as light as 55gr. But clearly, it really likes the 55gr. I will take out some 50gr VMAX next time and see what happens.
 
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Old 05-23-2013, 07:28 AM   #2
Rifleman
 
Joined: Nov 2009
From: Graham, Wa
Posts: 240
What really struck me was how "finicky" the longer, match barrel was. 1/8 should be more "tolerant" of a wider range of weights than the 1/7, and as a match barrel, should be more accurate. But clearly, the 16 inch barrel with a 1/7 twist was able to at least hold a decent "minute of combat" group with a wider range of bullets. And damn, 1/2 in group with a 16 inch barrel? I'll take that any day..
 
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