minimum amount of powder to cycle a AR in 556

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just wondering how small a amount of powder (335) can you load and still cycle a AR with a 62gr bullet?.
The question is very rifle dependent. There are too many mechanical variables to say this or that, will or wont, cycle.
Depends on many things like carbine length vs rifle length gas tube, buffer weight, recoil spring length/spring rate etc.


Hodgdon lists 19.3 gr as start charge for 62 gr bullet - http://www.hodgdonreloading.com/data/rifle
62 gr SFT SCIR H335 Dia .224" COL 2.260" Start 19.3 gr (2,678 fps) 47,500 PSI - Max 21.4 gr (2,887 fps) 53,600 PSI
And you can reference load data for slightly heavier bullet
63 gr SIE SP H335 Dia .224" COL 2.200" Start 22.5 gr (2,820 fps) 41,000 CUP - Max 25.0 gr (3,051 fps) 50,000 CUP


BTW, here's a recent thread on loading 62 gr FMJ/BTHP and H335 for 16" AR - https://www.thehighroad.org/index.php?threads/hodgdon-h335-and-62-grain-pills-in-5-56.825086/
 
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Reliably, for most guns, without testing I’m going to daily that it’s slightly above the minimum published load.

Realistically though, any load can just about cycle a gun under perfect conditions. Give the gun a pistol length gas system with a carbine length barrel, oversized gas port, light weight bcg, light buffer, light buffer spring, and a solid shoulder for it to recoil against and your pretty well good to go with just about anything more that a squib.
 
H335 is a ball powder that may not work well (squib), when loading below the published starting loads.

Hodgdon has youth loads using H4895 that may work better, when reduced.

But in an auto loaded, that needs the correct pressure curve to function , mostly a waste of time and components.
 
H335 is a ball powder that may not work well (squib), when loading below the published starting loads.
This was my first thought as well. My answer would have to be the book minimum for H-335, whatever that turns out to be. If you are flexible on which powder, that is another question.

I did a low velocity cycling test after a question here about 55 Gr, and 2600 FPS was as low as I could get reliable function using AA 5744.
 
What about a stick powder like IMR 4895 or 3031. I have loaded both in .223 and I have assembled reduced loads in .308 win with IMR 4895.

I agree h335 sounds like it is not a good candidate for this.
 
I read somewhere that in order to cycle a typical AR15 you need a pressure of 12,500 psi. at the gas port. So, what ever charge of powder will get you that amount of pressure at the gas port will be the minimum. That said, some powders (I don't know if H335 is one of them.) can cause pressure spikes if the loading too small.
 
H335 is a ball powder that may not work well (squib), when loading below the published starting loads.

I too would stick with published loads on this one. Find the source with the smallest “minimum” charge and your question is answered, if it runs in your rifle.
 
I tested some reduced h4895 loads a while back and it turned out 17gr under a 55gr bullet would reliably cycle a plain jane 16" carbine gas system AR. Could probably go lower with lighter buffer weights and bcg. At some point I want to play around with a shorter gas system with an adjustable block just to see what I can get to cycle.
 
2.5 grn. of shot gun powder will stick one in the barrel for sure!:cuss: you know why I know.

CC
Gotta smile on that one. I used to use 700X and 45 Gr bullets in .223 cases to mimic a .22 Mag, but it was a bolt gun.

I am not suggesting this, just thinking out loud.
 
I tested some reduced h4895 loads a while back and it turned out 17gr under a 55gr bullet would reliably cycle a plain jane 16" carbine gas system AR. Could probably go lower with lighter buffer weights and bcg. At some point I want to play around with a shorter gas system with an adjustable block just to see what I can get to cycle.
Yes, H4895 is a powder than can safely be downloaded to 60% of a normal max charge.

I did that with an AR pistol, and found that the minimum charge that would cycle THAT gun would not cycle any of my other ARs, due mostly to the gas systems all being mid-length or rifle-length, as opposed to the pistol-length on the AR pistol. But the best load I found for the pistol was with H4198 (the fastest burning rifle powder I had in my inventory).
 
I don't load 62 grain bullets, but I have been loading 60 grain in 223 for 40+ years, so this might be relevant. For IMR-4198, Hodgdon has a starting load of 18.3 grains yielding about 2,800 fps and a maximum load of 19.5 yielding a bit over 2,900 fps. I have loaded IMR-4198 down to as low as 15 grains and had it reliably function my semi-automatic rifles. At the time I did this, I didn't have a chronograph so I don't know how much that slowed it down.

Also, IMR-4198 is a "fast" for 223 so you get more of the impluse quicker than with "slower" powders. I don't know whether it would make a difference in how the gun functioned, but it might.

Finally, the "me" that managed to live well into adulthood would no longer dream of overloading or underloading a cartridge outside the range of published data.
 
To answer the OP’s question, 18.0-19.5gr.
55gr bullet. Velocity 2,450-2,700fps.
Too fast for accuracy with a cast bullet...
 
In my experience, starting loads do not usually or reliably cycle carbine length AR-15's. Somewhere above the starting load it should begin to cycle. Then there is another checkpoint - remember that it will cycle but not lock the bolt back after the last round is fired. It takes more powder transferred to gas to get it to do that. As always, how much powder it takes to do these things depends on temperature, primer, gas system length, recoil buffer weight, recoil spring weight, gas port size, etc.
If you're going for the ragged edge on the minimum, I would suggest to give yourself a little margin unless you like pogo'ing. You may work up a great load, only to find out that at a cooler temperature it turns into a single shot pogo stick :)
Accuracy is another story. Maybe someone has worked up a minimum load that prints well, I have never been that fortunate.
 
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