04-16-2018, 04:15 PM
ricsmall Wrote:https://tacticalcannon.com
Stonehenge,
Check this guy out. He has a YouTube channel with some testing. I blv a 7.5 twist would be ok for say a 55 grain. Ill load some up this week and try them for you. Be interesting to see the velocity and accuracy.
It would definitely be interesting to see your results, but it's really accuracy at range that concerns me. My retired 1:8 twist 24" 223 bull barrel pushed 40 gr Nosler BTVs at 3600 and got around 3/4 MOA at 100. Never used them on a p dog past 250, but when I tried them on 6" steel at 350 and beyond, there were more misses than there should have been and they were completely random putting them in the realm of "increased dispersion" . It could be the bullets but I don't think so. The 70 gr Nosler BTVs launched at 2950 out of my 1:10 6x45 track true out to 550. I recall having an SG of around 3.5 with the 40s and that's what I get putting 55s in Berger's calculator at expected grendel/Valk case based speeds.
Could be that the fast rotation causes minor deformities in the jacket that throws things off just a tad. There's also the theory that the fast spinning makes it more difficult for the nose of the bullet to adjust and track the line of travel (which is a constant adjustment down) which then increases dispersion. Think the comparison between a Tom Brady perfect spiral hail mary pass and an RG3 pass thrown way too hard that begins to float 20 yards down the field.
Also, at my elevation, the decreased air density that helps in so many ways sends SGs a lot higher than sea level. A 55 at Grendel speeds at sea level may have a SG in the high 2s, but it's going to get into the mid to high 3s at 5k ASL. My gut tells me 1:9 would probably work but that 1:10 is probably ideal.
Let's go Brandon!