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6.8 trajectory?

1760 Views 5 Replies 4 Participants Last post by  CaseyJ
I'm looking to build a new rifle. I'm thinking something in the 18" range for a good compromise. I'm trying to decide if I want to do a 5.56 or 6.8. My only 6.8 is an sbr (10.5") and I don't get to shoot it enough due to lack of ammo locally and the price, compared to having plenty of 5.56/.223. Because of this, I'm afraid another 6.8 will sit but I'd really like a good 18" stout rifle.

Rarely would I ever encounter a situation to shoot past 400 yards.... maybe very very rarely to 500. My question is the trajectory of 6.8 compared to 5.56 in the 300 to 500 range. My sbr has a short range zero and I'm anxious to play with it to 400 but have yet to. Is there a good chart showing more accurate trajectories?
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The velocities used on the 6.8 loads in the chart are probably taken using a SAMMI chamber with a 1/10 6 groove twist. Using a barrel with the proper chamber and twist could likely increase velocities a notable bit.

I have SPCII chambered 1/10 6 groove shooting factory 110 gr VMAX and had velocities that were 60-80 fps faster. In my 20 inch DMR chamber 1/12 3 groove I was getting 170-200 fps faster with the same ammo. Of course an 18 inch would be a little slower but definitely faster than the velocities CaseyJ had to work with.

Here is what SSA shows for their 90 gr TNT load - 6.8 SPC 90 grain TNT Practice or Varmint Round, Ammunition, 20 rounds/box
</META></META></META></META>2,900 FPS from a 16" Barrel Excellent accuracy

And the price is about $16 a box if you buy 25 or more boxes. If I hadn't just spent all my money on a new refrigerator for the house and some needed parts on my truck I would be laying in about 30 boxes myself at that price.
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