Twist Rate

[marineimaging]

If you are looking for general plinking your AR might do well with any 55 grain off the shelf bullet. However, if you are looking for heavier hunting rounds you should know what your twist rate is and match the bullet weight with the twist rate. There are other factors, but if your AR is not shooting consistently you might be having bullet issues, not gun issues.

The twist rate is show as a value like this somewhere on your gun or your paperwork. 1:7, 1:8, 1:9 up to about 1:16. That means that the bullet spins 1 time for as many inches as indicated. A 1:7, or one turn in 7 inches is much faster than 1:16 or 1 turn in 16 inches. If a bullet is too heavy the slower spin is not good for it. However there are so many values that play a role I am not going into all of them. I will just say to try different bullets before you throw your firearm away.

 

[MarkRohfrietsch]

Interesting data; I have never ventured above 55 grs. My AR has a 20" 1:12 with a 5.56 chamber. I have never used 5.56 commercial ammo, but hope to before the snow flies. So far, my AR is shooting tighter groups than my friends Troy Parr pump rifle; but I have a lot more experimentation to do.

 

[marineimaging]

Interesting data; I have never ventured above 55 grs. My AR has a 20" 1:12 with a 5.56 chamber. I have never used 5.56 commercial ammo, but hope to before the snow flies. So far, my AR is shooting tighter groups than my friends Troy Parr pump rifle; but I have a lot more experimentation to do.

Can you post some pictures of your targets and what ammo and range you are using to produce the shot grouping?

 

[MarkRohfrietsch]

Can you post some pictures of your targets and what ammo and range you are using to produce the shot grouping?

I will be posting some pictures a bit later; lots of revelations from yesterday's trip to the range.

 

[marineimaging]

I will be posting some pictures a bit later; lots of revelations from yesterday's trip to the range.

I was going to the range yesterday to adjust my scope but it was so hot I didn't even make it to the truck. Turned around and went back into the AC. I am such a woosie in my old age. LOL

 

[MarkRohfrietsch]

I was going to the range yesterday to adjust my scope but it was so hot I didn't even make it to the truck. Turned around and went back into the AC. I am such a woosie in my old age. LOL

When I got in the Jeep yesterday, it was 5 Degrees C. LOL It felt good!

Anyway, I saved two targets as representative. Note the measuring scale. These were both shot yesterday off of the bench, not using the Caldwell rest shown in the video I posted earlier, but from a cheap vertical grip bi-pod bought from the local paint-ball department of a local surplus store. Rifle is homebuilt, using a Chinese chrome lined 20" Dominion (Norinco) barrel chambered for 5.56 with a 1:12 twist.

As I experienced with the red dot, the Federal American Eagle Bulk 55 gr. was a disappointment; Typical groups 3-4" at 100 yards. Much more muzzle blast is noted as well. This one measures 3 13/16" center to center on the furthest spread.

My 55 Gr. home loads; my varmint round from days gone by, consistently shot groups at 1 1/8" or less; this one is 1" center to center:

So, now I have to start reloading again. LOL

 

[marineimaging]

When I got in the Jeep yesterday, it was 5 Degrees C. LOL It felt good!

Anyway, I saved two targets as representative. Note the measuring scale. These were both shot yesterday off of the bench, not using the Caldwell rest shown in the video I posted earlier, but from a cheap vertical grip bi-pod bought from the local paint-ball department of a local surplus store. Rifle is homebuilt, using a Chinese chrome lined 20" Dominion (Norinco) barrel chambered for 5.56 with a 1:12 twist.

As I experienced with the red dot, the Federal American Eagle Bulk 55 gr. was a disappointment; Typical groups 3-4" at 100 yards. Much more muzzle blast is noted as well. This one measures 3 13/16" center to center on the furthest spread.

My 55 Gr. home loads; my varmint round from days gone by, consistently shot groups at 1 1/8" or less; this one is 1" center to center:
View attachment 243300 View attachment 243299

So, now I have to start reloading again. LOL

Something I am playing with myself. I understand that the boat tail on a 55 grain FMJ actually hurts the 5.56 for 100-200 yard shots because it reduces the ballistic coefficient which is more helpful for our range. Meaning that the flat tail really doesn't hurt anything in those shorter ranges. The military uses the BT because they encounter either really short range targets or they want to reach out further than we typically hunt, so their shooting characteristics are focused to better to use BT FMJ whereas we might be better off with flat tail. Thoughts?

 

[MarkRohfrietsch]

Something I am playing with myself. I understand that the boat tail on a 55 grain FMJ actually hurts the 5.56 for 100-200 yard shots because it reduces the ballistic coefficient which is more helpful for our range. Meaning that the flat tail really doesn't hurt anything in those shorter ranges. The military uses the BT because they encounter either really short range targets or they want to reach out further than we typically hunt, so their shooting characteristics are focused to better to use BT FMJ whereas we might be better off with flat tail. Thoughts?

I got on the HPBT kick many years ago when I shot groundhogs at long ranges with a .22-250 and 6.5 x 55 and had phenomenal results. Before I got rid of my bolt action, I had picked up some Hornady V-Max 55 gr. which are a flat tail. For what ever reason, they did not want to feed in my AR. I did fire off a group with them, after much fighting and a lot of miss-loads, and it was comparable to the boat tails at 100 yards; but not being able to shoot more, I can't say that they were any better or worse than the boat tails.

Truthfully, anything loaded consistently is going to shoot better than that bulk stuff.

I will also at some point try heavier bullets to see if this barrel likes them or not. I need to get a set of carbide dies first. LOL.

 

[Aryeh Jay]

I thought that carbide dies were only for straight walled pistol rounds or the odd rifle round like the .45-70. I see that they make necked case dies now, the older I get the more things I like are invented but the less I can do.

 

[MarkRohfrietsch]

I thought that carbide dies were only for straight walled pistol rounds or the odd rifle round like the .45-70. I see that they make necked case dies now, the older I get the more things I like are invented but the less I can do.

They were available back in the 70's, but were stupid expensive; more affordable now.