AR15 5.56 M.O.A.L. to long using a mic

[helz_mcfugly]

So I tried to use my M.O.A.L. mic on my AR15 which is chambered in 5.56 and I used a 55 grain V-max. I normally just load .223 to AR15 spec which is 2.260. Well when I mic it It shows I should have them at 2.395 to have no free travel. Now that wont even fit in a 5.56 AR15 Mag. Ide have to chamber each round like a bolt action that opens it self after each shot. I wouldnt have a problem doing that being I mostly shoot benchrest. Also it wouldnt leave much of the bullet in the brass to crimp dwn on. i would have to use 75 to 80 grain because they would be long enough to load that long. my question is would this affect accuracy at all having .135 of free travel from case to rifling (in an AR)? I know it would in a single shot rifle. If so I guess getting a barrel chambered in .223 rather then 5.56 would be the only fix.

 

[wcwhitey]

My opinion but you cannot treat an AR like a bolt action rifle. The less "free travel" the better but you are limited to magazine dimensions. For the 55 grain bullet load it to the max OAL of 2.260 and enjoy. Unless you are getting poor accuracy and you have explored all the possible combinations of bullet weight vs. twist, powder, primer and brass type I don't see what the expense of getting rifle barreled in .223 is going to help. I have a question of your twist, depending on what twist you have such as 1/9 you will loose more going to the 75/80's than you will by having the bullet jump .135. If you have a rifle that just does not perform a new barrel is easier to buy and install than to have the old one sent out and rechambered.

My DPSMS Low-Pro is use Sierra 53 HP loaded to 2.25, plenty of jump but the gun loves them. My rifle likes the extra bearing surface over the boat tail because I tend to shoot at only 100 yards, does not need to settle as much. I only found that out by trial and error.

 

[chevy69002000]

I'm a noob at reloading as I have only been doing it for a few months now, so take my answer with a grain of salt. From what I have been told by experienced people is that there should be a space in between the case and the barrel. IIRC this is called bullet jump and there should be .020-.050 in a AR. When I load my 55grn V-max I load to a O.A.L of about 2.250 or maybe a little less. I get more than enough accuracy from this but then again what is acceptable for me may not be for you. I don't know if I answered your question so I will be tagging along to see others responses.

Ryan

 

[chevy69002000]

lol I was a little late on my response.

 

[Walkalong]

there should be a space in between the case and the barrel.

I am sure he means the bullet and the barrel.

If you want to shoot your AR with little to no bullet jump, you will have to load one at a time, as you have found out, unless you have a match barrel with a short throat/leade.

I mostly plink with AR's, but very good accuracy can be obtained loading good bullets to fit the mag and having a fair amount of bullet jump to the lands.

There are many here who shoot AR's competitively who can give a better answer.

 

[helz_mcfugly]

Its pretty dang accurate as it is. I get dime to quarter size groups at 100 yards. after shooting damn near every grain bullet and every powder, 50 grain v-max or blitzking with 23.6 grains of benchmark seems to be what it likes best. but still no matter how good it shoots Im always going to try for that 5 leaf clover. I was just wundering about that free jump my bullet has and if anyone had some input on it. ive loaded some at 2.385 and it didnt change much but I didnt load many so I dont think I had enough to really compair. I should probably jump to the 200 yard range now and start grinding on that for a while. My barrel is E.R. Shaw 24" BBL 1-9 twist, the rest is Bushmaster which started as a M4 A1, and a jewel trigger. I would like to get a barrel chambered in 223 so I CAN use my MOAL mic like I do on bolt actions. and ide like to go down to a 20" barrel with a 1-8 or 1-7 twist.
This is my AR and one of my groups.

 

[rcmodel]

The 5.56 chamber has a very long leade, in order to handle military tracer ammo, which is very long with a short ogive.

But the limiting factor is still the magazine.

Don't even worry about using your M.O.A.L. mic, because it won't work anyway with a 5.56 chambered AR.

Unless as you noted, you want a very expensive single-shot.

rcmodel

 

[ants]

My humble observation on your rifle - it's good to go.

With 1/9 twist, those very long 77 and 80 grain bullets will shoot OK but not perfectly. The gain made by seating them close to the rifling will probably be lost with the slow twist (1/7 or 1/8 is more optimum). Benchmark is probably a little too fast to get maximum performance from heavier bullets in a 24" barrel, Varget is the most likely choice of powder. But I don't think you need to go to 77 or 80 grain.

Your Shaw barrel is excellent for 55 to 69 grain bullets, and the jump to the rifling lands won't kill your accuracy. With Benchmark, try Nosler 55g Ballistic Tip, and maybe increase the charge in increments toward the max load. My 24" barrel likes 25.0 grains Benchmark with premium 55g bullets. Alliant Reloader 15 also gives excellent performance with a 5.56 chamber.

Or try 69g Sierra SMK with Varget (work up toward max load). Two boxes of 69g bullets will use up a pound of Varget, so it's cheap enough to try.

With a nice barrel and nice trigger and nice sights, you can achieve those small groups by prepping the brass consistently and working with the bullet/powder combo as wcwhitey mentions. Like rc model says, save the micrometer for your bolt actions.

 

[helz_mcfugly]

thanks for all the info guys. Im going to keep loading them at 2.260. and just mess around with 50 grain v-max, blitzking, and noslers with the benchmark.