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ExtremeX
10-04-2013, 1:10 PM
Just curious what bullet weight you guys have very good luck with…

I have a bunch of 75gr match bullets (average about 0.965” in length) I have been using for my AR but I worry it might be on a heavy side for that twist.

Seems like the 68/69 grain range is ideal, but curious if others have had luck with 75/77gr bullets.

tacticalcity
10-04-2013, 1:23 PM
It is 1:9 so the light stuff will be just fine. I would really rather they put a 1:8 twist on that rifle so you could take advantage of the heavy national match ammo. But they didn't consult me when designing it, lol.

It is a really nice rifle. I like it a lot. Thinking about getting the 308 version.

707electrician
10-04-2013, 1:24 PM
Agreed, it would be nicer with a 1:8 but they probably figure people are mostly using them as varmint rifles shooting lighter bullets

I would try the 75s and see how it likes them. They might be on the heavier side though

ExtremeX
10-04-2013, 1:28 PM
It is 1:9 so the light stuff will be just fine. I would really rather they put a 1:8 twist on that rifle so you could take advantage of the heavy national match ammo. But they didn't consult me when designing it, lol.

It is a really nice rifle. I like it a lot. Thinking about getting the 308 version.

Ya not too thrilled with the 1:9, I too prefer 1:8 which is what my AR match barrels are.

Only reason I bough the .223 version is because I had amazing luck in the accuracy department in my .308 SPS Tactical with a couple upgrades like trigger and stock.

ExtremeX
10-04-2013, 1:31 PM
Agreed, it would be nicer with a 1:8 but they probably figure people are mostly using them as varmint rifles shooting lighter bullets

I would try the 75s and see how it likes them. They might be on the heavier side though

Varmint bullets I have better luck with the SPS Varmint in 1:12 twist... I load for a friends rifle and the 52gr bullets really do well.

Twist Rate Stability Calculator puts my 75 grain bullets border line, I'm guessing I have to push them hard. They are shorter than the Hornady 75gr bullets which is an advantage for the 1:9 twist.

I just wanted to see if anyone has first hand experience with 75/77 grain with the SPS Tactical.

phish
10-04-2013, 2:02 PM
Berger's twist rate calculator gives a SG of 1.45 at 2700 fps, sea level, 59F, according to the info you gave on your bullets. They should stabilize.

NorCalFocus
10-04-2013, 2:06 PM
I say try em see if they stabilize.

russ69
10-04-2013, 2:09 PM
It depends on what you are doing but I'm having very good luck with the Sierra 55 grain Blitzking in just about all of my 223s. It's a varmint bullet but it's made with match grade jackets. It's a very good bullet.
You know, when you are working up loads and you have a bullet that might be borderline, the best way to sort it out is to just go ahead and load it up and try it. If it isn't stabilized you'll know soon enough.

Cypriss32
10-04-2013, 2:19 PM
75gr AMAX MIGHT and I mean MIGHT work, its 50/50. Some do, some dont.

70gr VLD will
75gr VLD prolly will

Those are what I would shoot if I had a bolt gun with 1-9tw.

ExtremeX
10-04-2013, 2:34 PM
Berger's twist rate calculator gives a SG of 1.45 at 2700 fps, sea level, 59F, according to the info you gave on your bullets. They should stabilize.

The velocity is what I was concerned about... 1.4 SG is on the boarder line of marginal stability and comfortable.

Generally find a good accuracy node somewhere between the min/max charge in a load book. Hopefully I can find a good node in the upper end of the charge.

phish
10-04-2013, 2:44 PM
Litz added a buffer of 0.4 to the SG calculation in his book. Anything above 1.0 should be stable. Berger went one more step further and added another 0.1 and recommends a SG of 1.5.

Only way to find out for sure is to try them in your rifle.

NiteQwill
10-05-2013, 12:02 AM
Mine shot Hornady 75 BTHP AMAX just fine. And that round is looong.