Load Development for an SBR

[alamo5000]

For example I made some numbers up and plugged them into a ballistics calculator.

I figured out of a 10.5" barrel I might get roughly 2500 fps using 55gr bullets.



If you notice at 100 yards I still would have over 2100 fps which I am sure would be enough to do major damage.

That would be about equivalent of shooting a bad guy at 250 yards with a 55 grain bullet out of a 16" gun.

[alamo5000]

Maybe Molon can come back and look at my posts and tell me if I am full of shit or not

[DeviantLogic]

We don't need Molon for that

I did a lookup on what to expect on muzzle velocities for 10.5" barrels. Expect a muzzle velocity drop of 300-350 fps across the board. Main point of reference is http://www.sadefensejournal.com/wp/?p=1093

Pulled out my Sierra reloading manual, going off the second column. For 55 gr = 2800 fps, 77 gr= 2500 fps. Take off 350 fps and you're then looking at 2450 fps and 2150 fps.

Plug in the data to Hornady's online ballistic calculator for Sierra 55 gr BlitzKing and Sierra 77 gr MatchKing.

Below are the results I got. Again...I'd take the 77gr

[alamo5000]

We don't need Molon for that

Hardy harr harrr harr !!! LOL HAHAAA!!!

It's worth taking a look at either. Another aspect is cost. The 55 gr is plentiful and cheap. The 77 is much more expensive on a per round basis.

At the end of the day though it's kind of cool that we are able to come up with these possibilities.

I did hear/read somewhere that a 77 gr bullet will not fragment below 2100 fps or something like that. I don't know the exact number...so based on that that would make the terminal ballistics of that really bad ass 50 yards and in... not that I would care to be shot with it at any range.

Again Molon needs to get back on here and let us know these things :)

But if a 77 won't fragment under 2100 fps (or whatever that number is) that kind of limits it for my wants... whereas with the 55gr it's still going to do what it will do out to and past 100 yards (per my requirement)

This is definitely going to need more brain power and time... and of course experimentation....

[alamo5000]

http://www.m4carbine.net/showthread....t-barrel/page2

Read the second response down...

[alamo5000]

From the 'other site' that I just found....

https://www.ar15.com/archive/topic.h...&f=16&t=363223

"A much more realistic threshold for reliable fragmentation with the 75-77 grain OTM loads is 2,250 FPS. From your 10.5� barrel, this will give you a fragmentation range of approximately 48 yards."

(found about 10 posts down the page)

[alamo5000]

At this point I am looking at 'which' 55gr to start tinkering with :)

I might even go 50gr....

Or a 55gr soft point... ???

[Slippers]

You should check with markm. He's done some fragmentation tests with the 77 smk out of SBRs. I believe he found it still fragments fine at 100-150 yards with a short barrel.

Also, do keep in mind that devgru use mk262 (77 smk) for training and 70 gr Barnes tsx for shooting bad guys, and they use a lot of SBRs. If it wasn't lethal, they would not be using it.

[alamo5000]

You should check with markm. He's done some fragmentation tests with the 77 smk out of SBRs. I believe he found it still fragments fine at 100-150 yards with a short barrel.

Also, do keep in mind that devgru use mk262 (77 smk) for training and 70 gr Barnes tsx for shooting bad guys, and they use a lot of SBRs. If it wasn't lethal, they would not be using it.

Another reason I'm on wevo :)

I dont recall seeing markm around but f you do pass the word.

I would like to hear his input. The more the better.

[Molon]

I figured out of a 10.5" barrel I might get roughly 2500 fps using 55gr bullets. . .

If you notice at 100 yards I still would have over 2100 fps which I am sure would be enough to do major damage. . .

The established fragmentation threshold for M193 (determined through extensive testing by actual experts in the field of terminal ballistics such as Dr. Martin Fackler) is 2700 FPS. Below a striking velocity of 2700 FPS the M193 projectile will not reliably fragment and instead will simply yaw 180 degrees and travel base forward.










The wound profile of the M193 projectile striking at 2650 FPS is little better than the wound profile from a .22 LR. Ask yourself, would a .22 rimfire be your first choice for a self-defense load?











Even when the M193 projectile has a striking velocity of 2700 FPS or higher, it’s only going to perform “as advertised” approximately 15% of the time. The other 85% of the time, the ballistic neck (the distance that the bullet travels in tissue before bullet upset occurs) is so long that the bullet will have passed through much of or all of the body before fragmenting.









Fackler, ML: “Literature Review”. Wound Ballistics Review; 5(2):40, Fall 2001


“In 1980, I treated a soldier shot accidentally with an M16 M193 bullet from a distance of about ten feet. The bullet entered his left thigh and traveled obliquely upward. It exited after passing through about 11 inches of muscle. The man walked in to my clinic with no limp whatsoever: the entrance and exit holes were about 4 mm across, and punctate.

X-ray films showed intact bones, no bullet fragments, and no evidence of significant tissue disruption caused by the bullet’s temporary cavity. The bullet path passed well lateral to the femoral vessels. He was back on duty in a few days. Devastating? Hardly.

The wound profile of the M193 bullet (page 29 of the Emergency War Surgery—NATO Handbook, GPO, Washington, D.C., 1988) shows that most often the bullet travels about five inches through flesh before beginning significant yaw. But about 15% of the time, it travels much farther than that before yawing—in which case it causes even milder wounds, if it missed bones, guts, lung, and major blood vessels. In my experience and research, at least as many M16 users in Vietnam concluded that it produced unacceptably minimal, rather than “massive”, wounds.

After viewing the wound profile, recall that the Vietnamese were small people, and generally very slim. Many M16 bullets passed through their torsos traveling mostly point forward, and caused minimal damage. Most shots piercing an extremity, even in the heavier-built Americans, unless they hit bone, caused no more damage than a 22 caliber rimfire bullet.”




With all the advancements that have made in bullet technology over the last decade, the 55 grain FMJ bullet is a very poor choice for a self-defense load.

I personally only use factory loaded ammunition for my self-defense loads. That being said, if you’re going to hand-load ammunition with an eye toward terminal ballistic properties, here are a few things that you might want to consider.


to be continued . . .


...

[voodoo_man]

https://youtu.be/HODSWc_Nid0

[alamo5000]

OK so I am back to 77gr????

I wonder about say like a 40gr soft point or other varieties of bullets...out of a 10.5 barrel this whole ballistics thing gets interesting.

I basically want to shoot what I shoot. In my other rifle I have one load. That's it. No rezeroing. None of that.

I just wonder if there is a 'really good' all around projectile?

Whatever I end up deciding on I am just going to buy and make a bunch of those loads.... so far there is strong evidence that says 70-77 grain range is a the better option.

[BoilerUp]

Hmmm...I've been considering 62gr Gold Dots (Federal Fusion) as my go-to home defense round for 5.56. My understanding is that it gives good expansion plus barrier performance. Unfortunately, I don't think the bullets are readily available for rolling your own.

[alamo5000]

Hmmm...I've been considering 62gr Gold Dots (Federal Fusion) as my go-to home defense round for 5.56. My understanding is that it gives good expansion plus barrier performance. Unfortunately, I don't think the bullets are readily available for rolling your own.

Are you trying to do that out of a 10.5 SBR?

I can find all kinds of bullets... I am just wondering which ones are going to be most wicked :)

Hard to argue with voodoo man or slippers... but I am just wondering and trying to figure out what to get and/or roll for a 10.5 rifle.

[alamo5000]

This is my first SBR but this thread might should be mandatory reading for anyone considering an SBR... 11.5 or 12.5 opens up a lot of world when it comes to terminal ballistics.