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9/22/2017 12:11:25 AM
Posted: 4/11/2002 10:41:41 AM EDT
Another thread has me interested in RRA's Varmint upper. Standard twist rate on the upper is 1:8 but the 24" version has the option for 1:12. First at what length does the .223 bullet start to slow down? Second, what is the optimum bullet weight for each twist rate? Third, is there a weight that is more accurate at a certain range than others?

I know thats allot to ask, but any help is greatly appreciated.
Link Posted: 4/11/2002 10:01:09 PM EDT
Any takers?
Link Posted: 4/12/2002 1:58:11 AM EDT
I'll be a taker,

O.K....let me see if I can remember some things and explain this.

I don't think there is a definative answer to "what length does a 223 bullet slow down". This, I believe, is because no one has tried to find out.

Regarding bullets weights. I *think* about 40 grains or about is good in the 1:12 barrels and bullets upto 80 grains in the 1:8.
Link Posted: 4/12/2002 4:23:07 AM EDT
Read the ammo FAQ in the ammunition forum here. It goes into twist rates and bullet weights.
Link Posted: 4/12/2002 4:47:50 AM EDT
I have the RRA upper you are describing. I have been using 69 gr sierra bullets in it with superb accuracy
Link Posted: 4/12/2002 6:11:59 AM EDT
Thanks guys, thats just what I was looking for.
Link Posted: 4/12/2002 8:15:43 AM EDT
Note that twist rate is linked to bullet LENGTH not weight (but since most rounds are lead they tend to have a correlation). I posted some good information on this recently in the Ammo forum (formulas & web links). Here is the thread www.ar15.com/forums/topic.html?id=107772
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