Transonic bullets... what is actually going on here??

[markm]

Back to the original thread title. What is the transonic concern? Have you experienced an issue? Or are you just asking if it will be an issue?

[turnburglar]

Back to the original thread title. What is the transonic concern? Have you experienced an issue? Or are you just asking if it will be an issue?

When I was deployed a SFC told me that if the bullet makes a whiffle noise, that meant the AK's where 6-800 meters away. This explanation was given to me that the bullet was tumbling as it went transonic. I haven't shot my AR this far before and I know lots of dudes on the boards (like yourself) push these to the limit, so I wanted to get some insight before showing up in the morning.

I love the idea of 69 TMK's, just dont have any in the safe and ammo availability is low for the moment. I understand that my 14.5" isn't the ideal barrel length for shooting 6-700 yards. A 18" with true 556 pressure 77's would do great I'm sure, just not what I have on hand.

[Joker]

Some bullets will make the transition fine. Others cannot handle the turbulence and destabilize when transitioning through the sound barrier.

At the 1,000 yd line, I've seen and heard many bullets that didn't cut the mustard. You'll really just have to try your combination and see how it performs.

[markm]

Some bullets will make the transition fine. Others cannot handle the turbulence and destabilize when transitioning through the sound barrier.

At the 1,000 yd line, I've seen and heard many bullets that didn't cut the mustard. You'll really just have to try your combination and see how it performs.

I've only ran into this trouble with 168 smks out of my bolt gun. Same bullets go trans in several other guns with no issue, including some shorter than 20" gas guns. Twist rate is my guess, but at 1000 yards, my 308 was fanning out over a 10+ yard impact area.

None of our .223 has issue with it. But we run all good or great bullets. 62 gr FMJBT W/C being the cheapest. And it has a pretty long boat tail which seems to handle trans very well.

55 gr, as sinister pointed out, dumps velocity CRAZY fast, and most 55 gr bullets don't have a world class shape that's going to do well in trans. I'd honestly only run 55 for 200 yards max. Beyond that, the 77s are just WAY more accurate. And at 750, the 77s really start to smoke the 62s quite noticeably.

[sinister]

I trained my buddy Stephen to get the most out of his ARs. We started at 300 yards with a 16-inch mid topped with an ACOG against steel GI E-type targets. He was hitting consistently and was amazed. A paratrooper and artilleryman by training, he commented, "Man that's a long ways away."

Fast-forward a year and he's built an 18-inch SPR, topped with a 3-10x scope. Same targets, he was annoyed he wasn't getting consistent hits and running out of steam at 850-875 yards shooting Hornady 75s.

The look on his face when I laughed and asked him, "Do you remember last year when you thought 300 was far?"

[1168]

I would highly recommend “Applied Ballistics for Long-Range Shooting” by Bryan Litz. Chapter 9 applies mostly tp transonic behavior. Also, there’s a blurb on p352 that talks about conventional bullets being mostly stable in the transonic region, where copper bullets, less so. “Understanding Firearms Ballistics” by Robert Rinker is also a good read.

I’m fond of 68/69 gr projectiles because I’m more of a “medium range” shooter, when I do stretch out. They are a good balance of velocity and BC that works well for 300-600. The velocity helps with range estimation errors in those ranges. As ranges stretch, heavier bullets like 75/77 become increasingly advantaged. Wind will beat you up more than drop. 55 gr bullets are not particularly good at anything but being cheap.

[Failure2Stop]

I have competed in and currently run "Mid-Range Gas Gun" competitions that stretch out to past 1,000 yards.
https://www.facebook.com/QuantifiedPerformanceLLC/

69+gr 5.56 from a 14.5" barrel will get you to 1k.
The biggest issue with extended range and 5.56 is compensating for wind effect, and being able to spot that teeny little puff of dirt for misses.
Drop charts are fine, but in a match you need to have a fast reference for exactly what you're shooting. There are a lot of solutions for that, but you will be better off if you can see the board from behind the optic. Write down each target in a sequence that makes sense to you with the hold or adjustment needed as predicted by your ballistic calculator or Kestrel.
Lots of references out there, what I linked to is a collection of high performers that can teach you a whole lot in a short span.
If you have questions, I can answer here as well.

[markm]

The look on his face when I laughed and asked him, "Do you remember last year when you thought 300 was far?"

Yep. That's a cool thing to accomplish for a new guy. I remember being in amazement at a 500 yard hit.

[Failure2Stop]

Yep. That's a cool thing to accomplish for a new guy. I remember being in amazement at a 500 yard hit.

You really come to grips with the perversion when you're figuring out how to add another 50 mils to the turret max without holding more than 10, and you have enough time between shot and impact to ask if someone can grab you a beverage from the cooler.

[markm]

You really come to grips with the perversion when you're figuring out how to add another 50 mils to the turret max without holding more than 10, and you have enough time between shot and impact to ask if someone can grab you a beverage from the cooler.

Ha! I don't want to get to that level. 1 mile is where I stop the madness.