Why the bigger flash?

[Charlie-AKA]

I've noticed that when I load with jacketed rounds I get a much bigger muzzle flash than when I shoot my hard cast lead reloads. For example, I frequently shoot 14 grains of 2400 or 8 grains of Power Pistol behind a 158 grain LSWC from Missouri Bullet Co. Either load makes a flash but nothing spectacular as .357 loads go. But if I switch bullets to a jacketed round, even if I use a lower powder charge, the flash is drastically amplified. 14 grains of 2400 turns my 586 6" into a fire breathing dragon if I use a jacketed bullet. Recoil and amount of noise seem about the same, as does accuracy, although the recoil might be a little less.

Why is there a bigger muzzle flash? What causes muzzle flash anyway?

[BLUEDOT37]

Jacketed bullets, verses lead bullets, are harder & give higher pressure, for similar styles & weight bullet, due to the material & bearing surface (cast bullets have grooves that reduce their bearing surface), for a given powder weight. Cast bullets typically have more blow-by too. The higher pressure & better sealing gives the, typically slower, powder a better chance to burn more thoroughly & violently.

Of course Power Pistol is very flashy anyway, & 2400 to a lesser degree, but there's a point where they burn more optimally, which you can see if you work up to a max. load by incrementing it by a small amount, say 0.2gr., of powder. You'll be able to tell when you hit the "sweet spot" for that powder by the report & flash. That's my take on it anyway.

[scooter123]

It's pure speculation on my part but slow powders such as 2400 are somewhat dependent on pressure for ignition efficiency. Because jacketed bullets do tend to produce higher pressures for a given velocity produced I'm thinking you're getting a better powder burn going.

[gray wolf]

It's pure speculation on my part but slow powders such as 2400 are somewhat dependent on pressure for ignition efficiency. Because jacketed bullets do tend to produce higher pressures for a given velocity produced I'm thinking you're getting a better powder burn going.

Agreed, and a better burn in the barrel means less powder burning outside the barrel = less muzzle flash.
Powders with less flash most times acquire that benefit from the coatings put on the powder at the factory.

[stu1ritter]

Just curious where you got your load data for Power Pistol at 8 gr. behind a 158 gr. LSWC. There are no Power Pistol lead loads in the Alliant manual for .357 Mag., only 38 Spc and 38 Spc +P. They do list 6 gr. for 158 LSWC for .38 Spc +P loading. I've been loading 5.8 gr. behind a 158 gr. LSWC and it is stout.

Stu

[BLUEDOT37]

Originally Posted by stu1ritter

Just curious where you got your load data for Power Pistol at 8 gr. behind a 158 gr. LSWC.

I don't know where Charlie saw it but Speer #13 has P-P @ 8.5gr max for 357Mag with 158 JHP data.

[Steve C]

When you shoot lead the lube on the bullets burn and sends out quite a bit of smoke. Likely this smoke is masking the flash you notice with jacketed bullets that produce smoke only from the powder combustion. As you only see flash under low light conditions it may also depend upon if you are shooting both types of ammo at the same range session under identical conditions. The same amount of powder should produce the same amount of flash, whether you see it or notice it is the only difference.

[stu1ritter]

bluedot37, yes, there are lots of loads for Power Pistol for jacketed bullets in .357 but none for lead.

Stu

[FloridaFlier]

My read on the material is a bit different. As the powder burns, the bullet obturates(sp), which is to say, it expands slightly. The softer bullet expands more easily, and picks up the rifling which causes the spin and inherent accuracy. My reading suggests that the most accurate .38spl load is lead. If flame is able to bypass the bullet, leading occurs, which mucks up the barrel for subsequent shots. Of course, you shouldn't see leading with jacketed bullets.

Optimal bullet hardness is a function of the pressure behind it as the powder burns, which is why the higher pressure .357 mag requires a harder bullet than the .38spl. Usually, lead has a lesser recommended charge than jacketed bullets. That is also why lead bullets, when pushed to a higher velocity, require a gas cap to prevent the higher pressure from bypassing the bullet.

Any flame that is in front of the bullet is wasted energy.

Anyway, that is my take on it. I don't experiment a lot; just read the manuals and follow the recipes. If I've missed the boat on this one, please educate me.

As always, YMMV.

[fredj338]

^^AGREE^^ I feel a softer/larger lead bullet seals the bore better. You get better powder combustion, less flash, higher vel for the same powder charge as jacketed.

[colt_saa]

The residual combustion that you see as flash once it comes in contact with oxygen after the projectile clears the muzzle, is smaller with a lead projectile than with a jacketed.

Prior to the lead projectile leaving the barrel, part of that combustion energy is used to burn the lube, this is what creates the smoke. This also cools the remaining combustion slightly

This is kind of the same effect as a sound suppressor being quieter wet than dry.