I have a Kel-Tec SU-16 in .223 and am getting only fair accuracy with 55 grain bullets. About 3-4" at 100 yards. It has a 1:9 twist. Would heavier bullets tend to do better?
Might just be that the SU-16 isn't particularly accurate. I don't know that (have never shot one, and have never been interested enough to read about it), but that could be the case.
thanks for the replies. I'm using W-W commercial sp ammo, PMP (South African) fmj, and remanufactured commercial sp reloads. all about same groups. I'll try some 62 grain loads.
You of course can try a lighter bullet but that might be a waste of bullets and time. 1 in 9 is a faster twist and more suited to heavier bullets (actually longer bullets...weight is not part of the stability formula). Bullets in the 60's grain weight class are a better choice.
The problem with pushing lighter (shorter) bullets out a 1 in 9 barrel is that the centrifugal force of the fast twist may cause the bullet to tear itself apart and not even make it to the target. This happen to me so it is not a theory. If the bullet is tough enough then it may be fine. You can not over stabilize a bullet. Standard hunting bullets are not tough enough. If you just have to use the lighter bullets reduce the velocity and the centrifugal force will be reduced, with the possibility of the bullet not coming apart.
The easy way out of this is to use good bullets (USA made) in the 60 to 70 grains weight class. you might see the accuracy get better.
That would be my first thought. Almost any .223 ammo should do better than 3-4" at a 100 yards - in almost any rifle - unless there is a problem with it. What are you using for a rest to shoot from? I shoot my .357 Winchester Trapper better than that offhand.
I hate to disagree with LD, But I have four 5.56s in the 1in9 twist two of these shoot sub moa with 55 grain bullets and two shoot sub moa with 52 grain bullets. I have tried heavier and lighter but the above is what they like best.
Whether the lighter bullet in a fast twist disintegrate before hitting the target is a function of the velocity and the construction of the bullets. I found old designs meant for hunting would not hold together yet more modern designed bullets would stay together.
The faster twist came about for 223 when the military moved way from the then common 55 gr bullets and over to the 60+ gr bullets. So the twist is for heavier bullets. Older non-military rifles often have a slower twist and shoot the lighter bullets fine but 1 in 9 is a faster twist and the bullet MAY suffer. Lowering the velocity of the lighter bullets reduces the chance of centrifugal forces disintegrating the bullet.
A shooter can shoot anything he wishes but a lot of time, money, and energy can be saved if he limits his choices to those that fit the design of the gun. 1 in 9 is for heavier bullets.
Just as point of reference, this disintegrating bullet scenario happened to me. Those that wish to do the scenario over to come up with similar or different results is fine with me. I am only just offering my experience.
I have a 1:9 twist Styer heavy barrel. I bought some commercial ammo, 55gr heads, to get the brass. Those rounds produced lousy precision. I reloaded the brass using 69 gr Sierra Match Kings and after working up the load produced a ragged hole for 10 rounds at 100 yards.
Each gun has it's own favorite load, and part of the fun of shooting is developing and discovering that special load.
Remember there are 60, 63, 68, 69, 75, 80 gr bullets. The 1 in 9 twist is probably better for those in the 60's whereas the 75 and 80 gr bullet might well need the 1 in 7 twist. If in doubt use the Greenhill formula for this to determine the minimum twist rate for a particular length of bullet. There well maybe some overlap but in general the longer the bullet the faster the required twist rate. If the bullet is well made then turning it faster than Greenhill rate does no harm. But as I related before, turn lighter constructed bullets too fast and they MAY come apart.
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