Does muzzle flash imply suboptimal load?

D

dbooksta

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Feb 22, 2009
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#1
I assume that the only way you get muzzle flash is if the powder hasn't fully burned before the bullet leaves the barrel. So if my loads produce a muzzle flash does that mean that they are suboptimal, in that either the powder is too slow or the primer isn't sufficient?

Or are there good reasons an ideal load might still produce a muzzle flash?
 
#2
Re: Does muzzle flash imply suboptimal load?

Actually, whatever powder is going to burn will burn within a few inches of the cartridge. There can be up to 15% of the powder that does not burn and is part of the ejecta.

Muzzle flash is the result of the hot presurized gases that are hitting the much cooler atmosphere. To me, a large muzzle blast is an indication of too short a barrel as all these hot pressurized gases should have been pushing the bullet faster in a longer barrel.

In my long-barreled match rifles (26-32 inches,) the muzzle blast is negligeable. The shorter the barrel, the greater the muzzle blast, usually.
 
#4
Re: Does muzzle flash imply suboptimal load?

Look for unburned powder left in the bore. A heavier crimp may improve your burn a little, trying a different primer may help, maybe a winchester primer as they are said to be a little hotter. I don't think this will make a big difference in muzzle flash, but if you are finding unburnt powder it may minimize it.

You may also want to look at the powders suitable for your cartridge and see where they fall on a burn rate chart.
 
#5
Re: Does muzzle flash imply suboptimal load?

I'm not seeing unburned powder granules in the bore or cases.

Following Sig685's post: Maybe I'm thinking of this the wrong way. Is muzzle flash an unavoidable consequence of using suboptimal barrel lengths? I.e., unless you have enough bbl for the gas pressure to drop below some critical level you're going to get a muzzle flash no matter how well everything has burned?

Recently I've been working with 16" .223 and 24" .308. Of course if size and weight were no object my .223 bbls would be 24" and my .308's would be at least 32". But if I want good velocities then my chamber pressure has to be around 56kpsi (or whatever the spec is) so of course pressure and temperature will be higher at 16" than at 24" or 32". I just didn't know if burn rate was part of this equation. According to Sig685 it sounds like it isn't (unless you're doing something very wrong).
 
#7
Re: Does muzzle flash imply suboptimal load?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: former naval person</div><div class="ubbcode-body">Various powders will give different muzzle flash or "bloom".</div></div>

Right, but what is the cause of the bloom (and the variations with powder)? Is it powder not fully combusting before the bullet leaves the bbl -- i.e., is it the result of propellant continuing to burn outside the bbl? Or is it an effect produced by fully combusted but still high-temp/pressure propellant gases interacting with ambient air?

And more to my original point, if you're getting all of this energy released after the bullet has left the bbl, doesn't that mean you're wasting energy, and that therefore you could get higher velocities by getting the propellant to burn more efficiently?
 
#8
Re: Does muzzle flash imply suboptimal load?

Let me rephrase my earlier post.

Muzzle flash has just about nothing to do with just about any other thing. Its presence or absence means..., wait for it..., nothing.

Next question.
 
#10
Re: Does muzzle flash imply suboptimal load?

First you need to define optimal.

In terms of accuracy, range, recoil, damage on target; muzzle flash is not on the list.
In terms of visibility to the target, muzzle flash is to be minimized.

So suboptimal has to do with whether the targets can shoot back, or not.
 
#13
Re: Does muzzle flash imply suboptimal load?

RSI, which seems authoritative, suggests that (excessive) muzzle flash is related to the load, and can negatively affect accuracy:

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">
[F]or most good loads the powder is burned a few inches beyond the point of peak pressure, but if the firearm has a short barrel and low load density, the peak pressure may move further toward the muzzle resulting in excessive "muzzle flash". Excessive muzzle flash happens when unburned powder ignites at the muzzle, causing turbulence behind the bullet with a detrimental effect on accuracy.

There is often a direct relationship between the burn rate (quickness of the powder) and the space a safe powder charge will fill. Powders can be made to burn quicker by reducing the granule size, which increases its density so a given charge weight takes up less space. Switching to a quicker powder may not resolve a muzzle flash problem if the powder has a high density and doesn't fill the case. Instead, filling the case completely with a lower density, but slower powder (as listed in a load table), may hold the point of peak pressure nearer the chamber for a complete burn, less muzzle flash and better accuracy.
</div></div>
 
#14
Re: Does muzzle flash imply suboptimal load?

My theory is that muzzle flash has to do with flammable gasses being exposed to oxygen. In other words the powder has burned within the barrel to convert it mostly to gas, but the oxygen in the bore is deplted before 100% combustion occured. When those gasses leave the bore they are exposed again to oxygen, and retain enough heat to reignite.

Kinda like a house fire that erupts when a door is opened, exposing oxygen to heated flammable gasses/smoke.
 
#15
Re: Does muzzle flash imply suboptimal load?

Rifle propellents are composed mostly of Nitrocellulose, which does not require additional oxygen to deflagrate.

The amount of oxygen present in the bore never reaches the propellent because it's blocked by the bullet. Rifle propellent would burn perfectly well in a vacuum, all that's required is to get it started at its kindling temperature. If there were any leakage at all around the bullet, it would be from the high pressure side behind the bullet toward the low pressure side ahead of it.

As for unburnt propellent and gasses flashing when they reach the atmosphere beyond the muzzle, I'd be guessing that's completely possible, but again, I don't think the muzzle flash would be absent in a vacuum.

Greg
 
#17
Re: Does muzzle flash imply suboptimal load?

My thinking is nothing more than the basic requirements for fire to exist (fuel, heat, and oxygen).

I think that the oxygen is fully consumed in the bore. Fuel (though the fuel has transitioned from powder to gas) and heat still exist in sufficient amount to reignite when expelled from the barrel back into an oxygen rich environment.

Without some form of fuel, it would be impossible to have a muzzle flash, as the flash is essentially fire.
 
#18
Re: Does muzzle flash imply suboptimal load?

During the hottest part of the summer I shoot late in the evening when its a little cooler. I had 2 different loads that I was shooting out of a 6.5-284. One was with IMR 4831 and the other was with RL22. The velocities with the same bullet were very close but the load with the IMR was almost blinding late in the evening. Everything else being the same, the muzzle flash made me go with RL22.

David
 
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