Just fig, I'd ask.
Its funny I shot 125 muzzys and they always hit just inches to the left of my feild points I went to a little stiffer arrow last year and the muzzys hit way to the left. I could'nt bring them together with my feild points. And the longer the yardage the wider the gap. So I went to a 160 grn two bladed fixed head and loved the way they flew hit perfectly with my feild points. (also 160s) . Well the last two days were pretty windy and I was doing some shooting and my pet 160s were wind planning (more so at longer yardages). So for giggles I put 125s back on retuned a bit and grabbed an old thunder head and despite the wind they grouped better. I then took the quiver off my bow tuned a little finer. And tonight after the wind died I grabbed 3 T-Headed arrows and 3 feild points and the grouping was amazingly tight. The only thing I can fig is that my 125 muzzys must be lighter than my 125 feild points. Or Thunder heads just fly better.
RE: Why do my thunder heads fly better than my muzzys
My guess would be that your inserts are not perfectly aligned with your arrow shafts. The O-ring system of the Thunderhead may help them align a little better. If your bow is tuned pretty well, you should not have problems getting Muzzys to fly and group well, unless there are problems with your arrows.
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RE: Why do my thunder heads fly better than my muzzys
Your muzzy is acting as tho the arrow is overspined. You stated you started shooting a stiffer spined arrow, so that may be it. The heavier head will bring the arrow back to the right.
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RE: Why do my thunder heads fly better than my muzzys
Why they hit so different are the muzzy 4 bladed? I know I will not slove your thought. But I don't like muzzy's but for hunting only hey why not..but they don't hold up during broadhead shoots. This is a good point as why to shoot before hand.