Load for a 16" barrel

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gdcpony

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I need a special load for my new upper coming in soon. Pretty much every load is for a 20-24" barrel. I hate waste and the idea of having powder still burning after the bullet has left is just that. I have had good luck with H-335 and A2230 in a 20" AR, and with those and Varget out of a 25" Howa 1500. However, I am certain that a faster powder will perform the best in a 16" barrel. I just need help deciding which one.
I would like some velocity, even though I know I am giving up allot in the barrel length. I guess I got spoiled spitting little 40gr screamers out of my Howa. Varget has the edge in the longer barrel, but will that still hold in the 16"?
The rest of the load will be a 55gr bullet, one of either Remington or Winchester cases, and Federal primers. They will be seated (for starters) .001 off the rifling, in a 1/9 twist barrel.
I have this table and that is it to go on as far as velocity loss for an AR.
http://counterstrikefox.freeservers.com/mv.htm
This is the upper to be mated to a DPMS lower, and a 1.5-5 Konus Pro Shotgun scope (trust me it is the best for this gun).
DPMS-A3-16Inch-BullBarrel-400.jpg
 
My favorite powder for my AR is Reloder 15...it gets more speed and better accuracy than any other powder in my rifle...YES...even from the 16 inch barrel.

AA2230 is a pretty darn fast powder...it works OK with lighter bullets.
 
Whatever powder gives the highest velocity in a 20" barrel will also give the highest velocity in a 16" barrel.

Think about it.
Any powder normally used in a .223 is finished burning well before the bullet gets to the gas port in the barrel and residual bore pressure unlocks the bolt.

If it didn't work that way, the gun would blow up!

Or at least the case wouldn't come out of the chamber if it still had pressure on it!

Further, dinking with fast powder in a gas operated rifle designed to work with normal loads is going to put undue strain on everything.

rc
 
IMR3031 had crossed my mind. And H322 is right there too. Reloader15 is a slower burning powder. What kind of load do you work with?
I am not looking for a pistol powder for this and it would be a "normal" load. Just on the quicker burning end. Don't worry, no Unique in my plans. I am thinking about the 322. Might be a good thing to try. I was thinking about the Benchmark as I have yet to try it out.
As far as the gas port idea I would need a visual to demo this right, but I will try. The gas is still pressurized when it reaches it. I don't know about burning. A high velocity "jet" -for lack of a better term- of gas is shot back the tube. The bullet leaves the barrel before the jet hits the carrier allowing the case to re-compress and the bolt to unlock. For this reason the distance of the port back to the bolt carrier will always be longer than the port to barrel end. I have been told the jet is initially moving at the same speed as the projectile and that is the momentum that moves the bolt back. This also serves to reduce recoil as it places things in motion. It get complicated. Here is a personal pic of it in motion.
l_50f89ba35d7f41dbac80553e09473478.png
And here is a burn rate chart:
http://www.varmintal.com/pburn.htm
Just to make things interesting I am going to try the opposite in my 26" 257Roberts and see what happens there. 40gr of Varget is throwing 100gr bullets at 3150fps right now. I'm thinking a slower powder would work in it and give better results (7/8" average benched).
The same powder (27.5gr Varget) had my 40gr 223 load flying at 3600fps out of my current upper (20"), but they wouldn't group less than an inch. 55gr bullets in front of 27g Varget are moving at 3250-3300 from it and going to .75" average. I'd like to keep velocity around 3000 if I can.
I do have an advantage. My supplier is willing to let into his stash of powders to load some different loads and try them out. He'll charge me for one pound and give me that much in assorted powders to try out. Since I got my bullet picked I'd only need find the powder and charge for it. Then I can order that. Same goes for the 257Roberts. I'd have another thread for that soon if not for the offer. I think a day at the range is in order this spring! Testing 30 different loads would be a blast!
 
I believe gas port pressure in the AR is about 15 - 18 thousand PSI, depending on whether it is a rifle or carbine length gas tube and port.

By the time the pressure reaches the bolt carrier & unlocks the bolt, bore/chamber pressure has dropped to near zero.

rc
 
I've been using H335 with my Bushmaster M4 16" barrel.

I'm shooting Barnes 62g solid copper X bullets with a pretty good group at 100 yards.

I'm in the process of loading some 55g FMJBT bullets with that same powder at a "middle-of-the-road" powder load. I have yet to see the group on that, but don't care, as long as I can pull about a 6" or tighter group at 100 yards, I'll be happy with them. I'm just going to measure then throw the charges, instead of measuring every single charge. The 55g bullets, I don't really care if they aren't tack-drivers. The way I look at it, they will most likely STILL be more accurate than a lot of factory ammo.
 
I measure just long enough to get my throws right. Then I check every 10 or so. I end up with some good loads. I use a cheap Lee measure too. Your H335 loads leave allot of flame out the barrel? I had a small burst from a 20" (25" had next to nothing) and was wondering.
 
I believe gas port pressure in the AR is about 15 - 18 thousand PSI, depending on whether it is a rifle or carbine length gas tube and port.

By the time the pressure reaches the bolt carrier & unlocks the bolt, bore/chamber pressure has dropped to near zero.

rc
Click to expand...
Forgot to mention that drop as the bullet leaves the barrel (from the 15-18 down). Sorry. However, I never put a number to it. I guess that in that load the powder was done burning and the gasses are decompressing allot from the bullet travel? Gas operation really plays havoc trying to figure out interior ballistics. All I want is to make the best use of the length I got. (and the wife laughs hysterically for some reason).
 
I just added it to the list to get from my guy.
Reloader 15
h-335
h-322
Varget (I ran out)
a-2230
imr3031

My current plan is to load ten rounds (2 groups of five) each from low to high spaced on the grain. For example Varget is from 25.5min to 27.5max. That is 3 loads or 30 rounds. 25.5, 26.5, and 27.5. I do all my load testing this way, but usually have to go through a pound of powder before I can try another kind. The offer of a sampling makes things so much better. Too bad I only have a little gear so my data will be generic (velocity, group). I'll take a day to go once the upper arrives and I have it broke in. I have enough Varget rounds for that
 
gdcpony:
I haven't noticed a flame, but then I never shot it at night. Anytime I ever shot it was on very sunny days.
 
I do allot of last light shooting. It would be enough to be seen in the scope. I still used it until I found A2230 worked a little better and cleaned up easier. Then I went back to it for my bolt gun, then to Varget.
 
Fast powders for short barrels is one of the most widely believed and most incorrect myths in all of handloading.

I don't care if you're loading bottlenecked rifle cartridges for a 10" handgun or a 26" rifle 99% of the time the fastest propellant is the fastest propellant regardless of barrel length. A powder must be of proper burn rate for the bore case ratio NOT barrel length.

Any and all propellant that will be consumed will have done so in the first three or four inches of barrel. Remember it's high pressure gas that drives bullets not burning opposite action reaction thrust like a rocket
 
I guess I'm a victim of myth then. I understand that pressure drives the bullet not the burning. But the burning causes it. A slower powder should burn longer in the barrel and thus give a more even pressure wave and a longer push to the bullet (though I understand that the increased volume created by the bullet's movement down the barrel may work against this). At the same time it follows that too slow and it is still burning past the point where it can be used.
I'm confusing myself!!! I've never heard of a bore case ratio. Please explain.
I know what it could mean. I've always thought a case size should fit the caliber (Hence my cartridge preferences of the .223 over the 22-250, 257Roberts over the 25-06, and 7x57 over the .308), but I was thinking of exterior ballistics when I thought of it, not powder burn rates.
 
In an 18" Galil ARM I have used WW748 and AA2460 with good results over a chronograph, with 3000 fps/55 FMJBT no problem at all. Also used a lot of H335, but can't find any chrono data for it. Despite the speed gap between WW748 and AA2460, safe max loads exceeded 3000 fps and considerably more in one set of data I looked at.

I like ball propellants for .223 because of ease of use in a progressive press, they meter extremely well, and load density is good. Also like mag primers for ball in any caliber.
 
On my 16" AR bull barrel I started looking at Nosler's .223 pistol data that used a 14" barrel and went with that data. I played around with H322, Benchmark and H335 using a 40 gr. Nosler bullet and stuck with 27.5 gr. H335, which also happened to be Nosler's most accurate powder and most accurate load.
 
A slower powder should burn longer in the barrel and thus give a more even pressure wave and a longer push to the bullet
Click to expand...

Nope the powder is all burned in the first couple of inches. Most of it is burned before the bullet is all the way out of the case.
 
I've been working up a load using AA-2230-S Data Powder (surplus) with good results in a 16" Saiga with 1:9 twist using 55 gr FMJBT for range practice. A bit over 2800 FPS for this combination seems to be the sweet spot for my rifle.

This powder is a ball powder that is, according to the Accurate rep, 4% faster burning than their regular AA-2230 powder.

I would think regular AA-2230 would give pretty close results.
 
The software package Quickload lets you see what fraction of the powder gets burned.

Just because there is a bright noisy fireball at the muzzle does not mean a faster powder will get higher velocity.

H335 is hard to beat for velocity in the .223, especially if you ignore the 55kpsi SAAMI registered maximum average pressure.
 
Quickload is a very good internal ballistics program. I have not seen anything in Quickload that indicates that 100% of the powder is burned in the first few inches of any of the loads that I have simulated.
 
100% of the powder NEVER burns. All of it that will burn is burned in the first few inches. Once the pressure drops all combustion stops though.
 
To get 0.001 off the lands are you loading single shot or does your barrel have a super short leade? With an AR, Unless you load one-at-a-time, I thought most guys just loaded the max OAL that fits in the mag.

The concept of Relative Case Capacity and how it influences powder selecton is explained here:

http://kwk.us/powders.html

...and can be applied here:

http://kwk.us/powley.html
 
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