[Philip Dedmon]

What is the slowest you have ever push a 55 gr. bullet out of an AR and it be reliable and accurate out to 100 yards?

[ChrisAR15]

Philip Dedmon, on Jun 23 2009, 05:33 PM, said:

What is the slowest you have ever push a 55 gr. bullet out of an AR and it be reliable and accurate out to 100 yards?

I have always worked at the "how fast" end of the spectrum, so I can't answer your question - but there are a few things you need to consider when thinking "slow":

Reliable:

You need to start thinking about how much gas is available to cycle the action. The AR was designed to work within a certain range of pressures. Start working outside that range and you may get feeding problems.

The second problem is that the cartridge needs pressure to seal the case mouth against the chamber. If you see black sooty residue around the outside of the case, your pressures are too low.

Accurate: Powders are also designed to burn properly at certain volumes and pressures. Drastically reduce the amount of powder in the case and all bets are off as to what will happen. Ignition may become inconsistent. I would choose a powder that has a lower density and load to the "starting" load given by the powder manufacturer.

Good luck

Chris

[Shawn Knight]

I agree with Chris. Slower isn't always better. Most of us try to get as much gas out of the system as we can to keep the gun reliable and work the comp if you have one installed. I have heard of people getting super high pressures as a result of having too much airspace in the case. If you are really interested you could look up some reduced course loads for AR's I am pretty sure most of them make minor.

You just need to keep the velocity above 2800FPS to stay safe for the chrono.

[SmurfJet]

FWIW I've found that detuning 55 gr. loads down to the 2600 fps. range significantly increases accuracy from my Sig 556 (1:7 twist barrel). Compared to fairly hot commercial loads like XM193 group size is roughly half-this is off a sandbag rest with a red dot sight at fifty yards. I'm not seeing any signs of gas leakage on the brass.

[shooter steve]

You guys must not know Philip... One heck of a three gunner. I can't understand how an old man can shoot like that. If he is asking about how SLOW you can get an AR to shoot, I'd bet he's not worried about PF or making the comp work. He's up to something...