Different twists on different twists

[dmy]

About to load my first .223 Remingtons and was hoping for some insight to shortcut my experimentation. I have a Colt M4 with a standard 16" barrel with a 1:7 twist and only plan to use it for lighter loaded target shooting. I understand that heavier bullets generally perform better with faster twists and vice versa. My questions are:

1. If I load a 55 gr FMJ with a lighter load, should it perform better with the 1:7 twist barrel than a medium load?

2. If I use a medium or lightly loaded 62 gr FMJ projectile, should it perform better with the 1:7 twist barrel than a lighter loaded 55 gr projectile?

3. Is the increased accuracy with faster twist barrels due to the heavier projectile or the slower speed of the projectile?

Finally, I bought a set of RCBS .223 Remington dies. I presume I cannot use them to reload 5.56 x .45 nato cases because of the longer neck of the latter. True?

Thanks.

[baih777]

you use 223 Remington for 556. GTG

[racinjason233]

25 grains of BL-C2 load 100 and let'er rip 10 rounds at a time of coarse...

no really that is a great load for 100 yard plinking and you can customize length and crimp with all the other detail from there.

reloading ammo is often way over thought, load your 1st hundred with different over all lengths and enjoy the process don't forget to trim!!

[jericho89]

as stated 223 dies are correct for 556 nato. There is not dimensional difference in the outside of the cases. The nato cases tend to be thicker because they are run at much higher pressures. If you study up on the two rounds you will find a lot of good information and a lot of confusing information.

As for twist rate the faster twist is used for heavier bullets to get them to stabilize better. I have not seen any studies on the performance of each run at different velocities. I think you will need to see what your rifle likes best and go from there.

Good luck

[OpenSightsOnly]

I have an 1:7 A2 upper, and I have fed that upper with reloaded ammo from 52 gr. SMK to 82 gr. Berger bullets.

Not one issue at all.

[kcheung2]

I think you're overthinking the wrong question. Presumably you're looking for an accuracy load, if that's the case pick a powder, pick a good projectile, look up the manual, load a few charges, and see what your gun likes.

So many people get fixated on twist rates, but the fact is that most projectiles work fine with most twists. What projectile are you using? (and no, not all 55gr fmj are the same) And why are you using 55gr for an accuracy load? What powder? what primer? What OAL? All of those criteria would affect accuracy much more than twist rate.

[LynnJr]

FMJ should only be used if your after mediocre accuracy.
If your after better accuracy look for a better bullet.
On your twist questions a bullet requires a certain amount of twist so it is gyroscopically stable. You want a Sg of around 1.5 for good overall accuracy. Lighter bullets for a given bore diameter would be shorter than heavy bullets for the same bore diameter all things being equal. The longer the bullet the faster it needs to be spun to be gyroscopically stable. You can look up Green hill formula if you want to see the math.
40 grain bullets will work in a 14-15 twist barrel and 80-90 grain bullets will keyhole.
If you go to a 7 twist barrel like you have the heavy bullets will stabilize and the very light bullets will actually be over stabilized.
They will still work but you are past what they require to shoot well.
An analogy would be leaving your car in low gear on your way to work.
The engine will need to rev higher than is necessary to go 40 MPH.

[dmy]

thanks all

I haven't actually loaded any bullets yet. I bought some Hornady 55gr FMJ, Winchester cases, Winchester 748. Haven't bought primers yet, but will probably go with Federal or CCI. I plan to crimp at the cannelure whatever length it turns out to be.

[6mmintl]

It's all about rpm, bullet quality, and barrel quality.

I've shot 55 gr. Fmjbt ball at 2800 out of a 1x8 twist and had less then 1 moa accuracy, shoot it at 3200 fps out of a 1x7 or 1x9 and accuracy goes all to he'll .

My first HBar in 1983 had such a rough barrel it would cut bullet jackets on smk 69 grain bullets and they would fly apart at 2800 fps.

[ar15barrels]

3. Is the increased accuracy with faster twist barrels due to the heavier projectile or the slower speed of the projectile?

Faster twist barrels decrease accuracy.
Shooters looking for the best possible accuracy use the slowest twist rates that will properly stabilize their bullets.
If your barrel twist is fixed, you would simply choose longer bullets to reach that point where the twist rate is perfect for the bullet length.
In a 1:7 twist 22 caliber barrel, you need 80-90 gr bullets to be at that point.

[micro911]

I used a Wilson SS 1-8" barrel and shot Federal 55 gr soft point bullets. It was pretty accurate. Actually, I took the Topgun award in my instructor class.