Testing AR-15 1:9 twist rate barrel with 3 new ammo choices

[Joe L]

This is my Friday assignment, since I had a relatively minor lower back nerve surgical procedure this morning and can't walk a straight line yet...

I have a ton of 55 gr M193 ammo now, and the rifle likes Federal 55 gr just fine.  I bought some IMI 55 grain to try.  For comparison, I also bought some Atlanta Arms 55 gr match ammo, and one box of 65 gr ammo.  I've shot heavier bullets in this 1:9 twist barrel, but didn't really test it at any distance.  72's didn't tumble is about all I can say. 



What I plan on doing is 5 five round groups starting with the IMI, then the AA 55, then the AA 65, then another of the IMI 55, all at 100 yards with a 1-4x scope from a bench.  What I am most interested in is the comparison of the IMI rounds to the AA "match grade" 55 rounds.  I'm hoping there isn't much difference.  Then I want to confirm that the 65 shoots well and then see what the zero shift is with the heavier bullet. 

Suggestions/comments are welcome.  I'm not much of a rifle guy, but I've raised my standards for rifle results after shooting several 3-4 inch groups with a subcompact 9mm pistol at 100 yards, that's for sure.  I bought a bunch of the IMI ammo because I know I will have to LEARN to shoot good groups with the AR, just like I did with the pistols.   

Joe

[Joe L]

John A.--thanks for the comment.  I haven't even considered going lighter than 55 gr.  Good point.

Joe

[Wobbly]

If previous JoeL adventures are any indication, then this is going to be a fun thread to watch !

 

[Joe L]

If previous JoeL adventures are any indication, then this is going to be a fun thread to watch !

Well, I had lumbar nerves deadened on Thursday, have some pain in my back today, it is windy and overcast with rain expected by noon, and it's Friday so the range will likely be crowded.  A perfect day to try ammo and try shooting the little rifle with the long barrel, well, longer than 5", that is. 

Seriously, I hope I get some meaningful results and not just trigger time.  Not that there is anything wrong with that.   

Joe

[Joe L]

I survived long enough to run 20 rounds of each ammo through the Stag Arms 2T at 100 yards from a bench, using a 1-4x Nikon scope.  The test went well, especially for the IMI ammo, which equaled the Atlanta Arms 55 gr FMJ but at a different velocity judging from the shift in zero.  The 65 gr AA groups were larger than either of the 55's, but I only bought one box, just to try it, and the groups weren't bad, just 2.5" compared to 1.7/1.8 for the 55. 

I gambled and it worked out well.  I bought 1200 rounds of the IMI 55 before testing it.  I did shoot some Federal 55 and it looked good, so it just came down to cost and availability. 

 

I didn't pull the stock in to my shoulder so hard today and that took some of the wiggle out of the reticle due to pulse transmission to the rifle.  But a B-8C target bullseye is a little large to place the Nikon reticle in, so I think I can tighten these groups up for all the ammo with a little more tweaking on my part, relative to the sight picture and sight alignment.  I'm thinking just stick with the IMI 55 gr ammo and learn to shoot the rifle.  I am pretty sure it is a 1 moa AR-15, but I have a 2 moa sight picture.  I will try a smaller aim point. 

As is per usual, gun and ammo are fine, shooter needs work.   

Joe

[Joe L]

I've thought about it a little more and I couldn't be happier with the IMI 55 gr M193 ammo.  So I will put the "good" Atlanta Arms ammo away and shoot the IMI while refining my skills. 

I am going to try the 65 gr ammo one more time, probably Tuesday.  I was a little rushed this morning, and 10 shots in less than 15 seconds twice in the wind isn't really a fair test.  I'm thinking the group size will be much closer to the 55 on a more "normal" day, when I am interested in more than "Is this IMI ammo GTG or not?".  That question has been addressed, so now I can refine the tests and my technique and shoot the 65 gr with a little more enthusiasm and focus.

First thing to change is to use something other than black for a bullseye color, since the biggest problem I had today was placing the black Nikon scope reticle in the middle of a large black bullseye, the B-8c target.  This target works perfectly with the RED dot sights on the pistols, but I need a red or yellow bullseye when using a black reticle!  I remember (now!) doing just that for the .308 Savage bolt gun with the Bushnell G2DMR reticle--I used colored 3x5 index cards at 500 meters for the targets.  That scope is a 3.5-21x however, not a 1-4x like on this little rifle. 

This is a good start to learning how to shoot an AR-15 well at 100 yards.  I should be able to get a little more out of the IMI ammo next week.  Shooter needs work. 

And, yes, I have already cleaned the AR-15 bore so it is ready to go on Tuesday. 

Joe

[joedirt199]

My buddy's rock river has a 1-9 twist and shot some surplus cheap stuff pretty bad. Hornady sent us a case of Tap 55 ballistic tip for testing so we ran some of that through there. Nice little groups.

[Wobbly]

Did the same thing with my Rock River years ago. Had a groups about 2 feet in dia at 100yds with discount bullets. Changed over to first rate bullets and the group got considerably smaller.

[Joe L]

Well, I'll be shooting the AR some time today, I hope.  Thunderstorms right now and the range floods easily.  I may have to drive out there to see how much water is standing.  I will shoot anyway if the gate is open. 

I'm not going to change anything but the aim point today.  With a black reticle, I'm going to use a red aim point, so I can see the reticle lines over the target.  I'm betting that alone will get me much closer to 1" groups using the IMI ammo.  I may try the 55 gr Atlanta Arms ammo one more time also, just for a comparison against the IMI, once I get my technique refined.  I'm putting the 65gr to the side right now. 

Edit to update for Tuesday--Outdoor range is closed due to standing water.  Not sure when they will be able to open again.  Common difficulty in the Hill Country.  In the desert, we rarely got rained out, but it got hot! 

Joe 

[Joe L]

I made it to the range today for a short time, shot 40 rounds of the IMI 55gr with predictable hits, so I'm happy with the ammo and the rifle.  I have a new scope arriving today since I can't find my little Nikon 2-8x, and I will try that tomorrow at 100 yards and see how good a group I can shoot with the little AR.  Using Red for an aiming point helped, but I am still having problems keeping the gun steady for each shot.  I think it is a shoulder or cheek weld problem, still picking up too much pulse rate pulsing, which will only look worse through a good scope!   

Joe