5.56 Ballistics of 55gr vs 62gr. vs 77gr.

[GuitarmanNick]

My 1:7 twist barrels produce excellent groups with 55, 62, or 69 grain projectiles. My handloads are more accurate than factory produced fodder. Projectile length, not weight is the real determining factor in selecting the best twist rate.

I zero @ 25 yards using my 69 grain loads. This puts me back on around 260 yards depending on the rifle and gives a fairly flat trajectory out to 300 yards without holding over.

When shooting other loads, the elevation is usually pretty close their POI.

I use Strelok+ ballistic calculator when I really want to be precise. If ever needed for defense, any weight bullet will work well with no calculation required out to 300 yards.

My inventory includes 55 and 62 grain 5.56 NATO. Accuracy and POI are about the same with either.

Each barrel is unique so the OP should do some testing to find what ammo his likes best.

 

[Biggfoot44]

I'm too lazy to edit a quote of Alucard's post down to one sentence , so I'll just paraphrase the sentence .

" Why do you want to change ammo ? "

I'm not the OP , but there's an obvious widespread answer .

Seeking some form of * best * ammo , be it tightest groups , hunting , long range trajectory , whatever , and it's a 62/ 64/ 69/ 75/ 77 gr .

Meanwhile , common 55gr fmj is inexpensive and ubitquitis .

If zero'ed for your most best- est load , would the buy cheap stack deep 55gr be close enough POI for high volume plinking / shooting steel/ carbine drills / etc out to 100 yds or so ?

 

[outrider58]

I'm too lazy to edit a quote of Alucard's post down to one sentence , so I'll just paraphrase the sentence .

" Why do you want to change ammo ? "

I'm not the OP , but there's an obvious widespread answer .

Seeking some form of * best * ammo , be it tightest groups , hunting , long range trajectory , whatever , and it's a 62/ 64/ 69/ 75/ 77 gr .

Meanwhile , common 55gr fmj is inexpensive and ubitquitis .

If zero'ed for your most best- est load , would the buy cheap stack deep 55gr be close enough POI for high volume plinking / shooting steel/ carbine drills / etc out to 100 yds or so ?

The same thought occurred to me, and then it hit me; that's his defense.

 

[Biggfoot44]

Also consider if the 62g bullets have a penetrator in them. Folks say those projectiles aren't as consistent with their construction and may not provide as much accuracy as the lead filled FMJ rounds.

Makes a big difference .

As far as twist rates and stability , it's more the factor of the Length of the projectile , and weight is just a short hand .

Steel penetrator inserts are less dense than lead . An M855 62 gr would require a twist tate more or less comparable to that for a lead core 69 gr .

From personal experience with a vintage Commando upper with 1:12 twist , M855 is tumbling right from the muzzle , while 62gr lead core at least lands point forewards at the backyard distances I tested .

In non .223 bore sizes , over the years , has been a variety of twist rates in .30 , 7mm , and 6.5mm rifles . With heavy for caliber bullets , you will read about better accuracy and stability with flat base RN of same weight , compared to boat tail Spitzer , in rifles of slower twist .

 

[Baldheaded]

The reason I started this thread is to educate myself as much as possible on the options one has when trying to pick an ideal bullet. While I do understand there isn't a 1 bullet do all I do believe the average Joe just gets an AR15 and buys the cheapest most readily available ammo they can find and doesn't understand what goes into the decision to use a certain type/grain bullet. Some people are at the other end of the spectrum and go to great lengths to determine the best round for a certain situation. I probably fall somewhere in-between. Maybe at some point I will get to an expert level. That will also require me to spend a lot more time at the range that I don't currently do. There are a lot of people here that probably fall in the expert category and hopefully I can learn from them. I have learned from several of the posts in this thread. TY.

 

[Uncle Duke]

The reason I started this thread is to educate myself as much as possible on the options one has when trying to pick an ideal bullet. While I do understand there isn't a 1 bullet do all I do believe the average Joe just gets an AR15 and buys the cheapest most readily available ammo they can find and doesn't understand what goes into the decision to use a certain type/grain bullet. Some people are at the other end of the spectrum and go to great lengths to determine the best round for a certain situation. I probably fall somewhere in-between. Maybe at some point I will get to an expert level. That will also require me to spend a lot more time at the range that I don't currently do. There are a lot of people here that probably fall in the expert category and hopefully I can learn from them. I have learned from several of the posts in this thread. TY.

You're absolutely hitting the nail on the head when you allude to application.

Many folks are primarily interested in the ballistics of delivering a bullet from Point A to Point B. That's a science in and of itself. Then there's the terminal side of ballistics, also a science in and of itself. Terminal ballistics is less about the journey, and more about what work needs to be done, and thus about what happens when that particular bullet arrives.

As but one example, many handloaders are focused on shooting highly precise match grade or "Match King" type bullets, for a variety of applications. They're precision shooters, or long range shooters perhaps. There are others here, though fewer here in number I'd suggest, who shoot very few match type bullets. And that is because they're primarily hunters, and they would never shoot match bullets at game animals. Their bullet focus lies elsewhere. Defensive applications will likewise have some similar, yet also some differing considerations. As will more recreational shooters, where "acceptable" precision is plenty good enough, and the primary concern is best possible price.

Enjoy the journey!

 

[King Chicken]

There are a lot of people here that probably fall in the expert category and hopefully I can learn from them.

The pointier the bullet the farther it goes. YW!

I too am learning. I'm building my first AR and didn't know if I should zero using proper bullet for twist (69 grain) of what I'm using to break rifle in(cheap crap 55gr).

 

[Biggfoot44]

Ok ! I was conservative with my off the top of head rule of thumb in above post .

IF you are on board with aiming / zeroing strategy somewhat resembling the popular " Battle Zero " , you won't notice any meaningful difference in POI out to 200 yds . And if you switch to 77gr , simple Kentucky Windage ( elevation ) for close to 300 yds .

 

[BurkeM]

Question regarding an AR15 zeroed with 55gr. ammo and considering changing to 62gr. or 77gr. ammo. Should you stay with a certain grain ammo like 55 once you get zeroed or can you change to 62 or 77 without getting off zero by to much?

This is like asking the ancient questions:

Ford or Chevy?

.45 ACP or 9mm or .40 S&W?

Glock or Sig?

Crocs or Adidas?
-----------------

Only YOU can decide what works best for YOU. There are literally thousands of pages of research on the two types of ammo (.223 Remington or 5.56 NATO) with different loads (bullet weight, shape, and different powders). Different barrel lengths change the math, different rates of twist in the rifling change the math. Chrome lined vs unlined barrels change the math. How often you clean your rifle changes the math. The weather changes the math, day by day. What type of sling you use can change the math. What type of sights used will change your math.

What woks BEST is user consistency.

 

[brianns]

From personal experience with a vintage Commando upper with 1:12 twist , M855 is tumbling right from the muzzle , while 62gr lead core at least lands point forewards at the backyard distances I tested .

My 20” 1:12 twist does that inside of 25 yds with 62g. Didn’t know they were 62s when shooting it. Box wasn’t marked, upon further inspection they had something ferrous in them.

 

[Biggfoot44]

That's it , but this was 15 feet .

 

[brianns]

That's it , but this was 15 feet .

I checked my video to see if it was less than 25 yds. But no added info. But I offer some discussion on the topic.

 

[Biggfoot44]

" Playback on other websites has been disabled by the video owner " ?

 

[brianns]

" Playback on other websites has been disabled by the video owner " ?

I guess I don’t know how to fix that yet. Does it not take you there though if you click where it says watch on YouTube?

 

[brianns]

" Playback on other websites has been disabled by the video owner " ?

I fixed it. I have to allow 'embedding' on that video. Having videos appear in this sight is a form of embedding I guess. Probably should be doing this on most of my videos.

 

[Archeryrob]

Okay, so I have the 1:7 twist barrel and it seems that just is going to be a no go, for trying to make cast bullets work for 223 AR. So I am looking at 68 or 77 grain HPBT bullets to buy. What does anyone recommend?

They all seem to be match bullets and all hunting recommendations are only for the lighter bullets. As if these could kill something if they went through it. The use would be varmint and a SHTF load for the significant other. Target only as if her , or I, practicing.

These bullets I am looking at are some times called OTM or open tip match and it is like the jacket is not fully swaged with lead in the tip. Assuming the jacket will fold open immediately on contact as a HP would. Any reason why these would, or would not, be a good choice. Or would something else be better?