Why aren’t there more OTMs in 5.56

[1168]

For what it's worth, chasing an extra 50-75 fps isn't worth the potential problems.

while I generally agree, the spread between different brands of factory 75/77 gr ammo is a little over 200fps. I assume each brand uses different powder, so arrives at a different “node” for production.

[mark5pt56]

while I generally agree, the spread between different brands of factory 75/77 gr ammo is a little over 200fps. I assume each brand uses different powder, so arrives at a different “node” for production.

Referencing factory AND reloaders who chase velocity only "trying to beat the wind" I get it, fast efficient bullet is the way but the difference in a safe and accurate load and one blowing primers and not as accurate is what I referenced.

[ST911]

while I generally agree, the spread between different brands of factory 75/77 gr ammo is a little over 200fps. I assume each brand uses different powder, so arrives at a different “node” for production.

Point of reference, same 16" barrel, both 77 SMKs
Federal TRU T223M3, 2380
Mk262 Mod 1, 2630

BHA 62 TSX, 16"
5.56, 2900
.223, 2770

Looked for a 55 weight class difference, but I remember that the 55 GDSP 5.56 (d/c) and .223 were about that far apart too.

The difference in the TRU and 262 matters, start stretching them out (800-1000+) and the difference really shows.

[mark5pt56]

I will say this and it was a one time experience, MK262 in a .223 LTR proves the over pressure hole in the receiver works rather well. Worst sound I ever heard and took a few minutes to make sure I wasn't leaking anything. I didn't know any better and then learned the difference in chambers and pressures.

Maybe it was a fluke, but I won't test the theory again.

[sinister]

National Match shooters will normally shoot a 68-77 grain bullet at 200 and 300 yards, and an 80 at 600.

There were a few years where the Marine chain of command told their teams no 80-grainers for the long lines (600 yards for the National Match Course and for the Palma Course fired with a service rifle at 800-900-1000 yards) because single-loaded ammo is not a standard military item.

The Marines gave away a LOT of points and lost. Often. Good for the Army.

While Army was shooting 80s and 7.62, Marine 77s would get to 1,000 having passed through trans-sonic and into sub-sonic speed. At Quantico we watched as one went "Blat" through the target, hit the impact berm, bounced back up-range and landed on the catwalk, spinning like a little top.

A young Marine bent down to pick it up for a souvenir, then dropped it, howling. That thing was only a second out of a rifle at around 55K psi pressure and heat.

[Wake27]

So all of this reloading discussion is going way over my head. I’m in the Rockies of moving from CO to NC right now and transporting my guns and factory ammo alone fills up most of my Grand Cherokee. I can’t imagine adding reloading components on top of that.

As for the question on what we’re using to determine 5.56/.223, I was only referring to what they’re marked on the box from the factory. But the driving point behind the question was due to bullet drop and ability to fight wind. Shooting at 600m with the winds that can whip through the CO plains is not easy for someone that’s pretty much brand new to it.


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[markm]

A young Marine bent down to pick it up for a souvenir, then dropped it, howling. That thing was only a second out of a rifle at around 55K psi pressure and heat.

I've often wondered about some of our lower velocity bullets past 1000 yards.... if the extended flight time cooled the bullet much.

[turnburglar]

No it won't cool the bullet enough to touch it. It was only flying for a second, metal doesn't cool that fast. I have grabbed tons of pistol slugs right after shooting steel and without a glove its funny pretty quickly.

That federal velocity of 2380 FPS from a 16" barrel is why I got into reloading in the first place. I dont want to pay big dollars for neutered rounds. It might shoot good 100 yard groups, but shit will you notice your holding higher than any other load if you actually shoot 500 yards or more.

I recently changed my reloading mindset. I used to make loads well above any published book max, but once I got a few blown primers in my lower and realized I was only hurting my precious creed moor brass I looked for Nodes at or slightly below max.

[markm]

No it won't cool the bullet enough to touch it. It was only flying for a second, metal doesn't cool that fast.

I was wondering about flights well over 1 second. But maybe there's some principles of physics beyond my knowledge that are at play.

I recently changed my reloading mindset. I used to make loads well above any published book max, but once I got a few blown primers in my lower and realized I was only hurting my precious creed moor brass I looked for Nodes at or slightly below max.

I've gone to small rifle primer Creedmoor brass for that reason. Hornady standard/large primer pockets actually hold up pretty good though. I run hornady pretty hot and have had 3-4 loads in some of it.

[tomme boy]

The reports I was seeing with the 41 primers popping was with some of the new wiz bang cartridges using small rifle primers. Part of what was found out was the brass was soft and less internal capacity than previous batches. At least with one guy anyway. Several other I seen were using 223 and popping primers. One was blanking, the other was blowing pockets. The one with the pockets posted and never came back to update.

My take on this is everything made in the last 2 years is suspect. QC no matter who it is get compromised when mad $ is to be made in big corporations.

As an example. I just got a bag of starline 556 brass to try. Local place had them. Got them home and they all measure 1.742"-1.746". I have not weighed them as I have them loaded up already for testing. This is the first time I have ever bought 223/556 brass. I normally use range brass for everything.

Another example, I have had 2 BA barrels and 2 Wilson Arms barrels I have sent back as they have bad chambers, bores with voids in the rifling. These were in the last year.