When do I need gas checks?

[k Squared]

I have been loading 357 and 44 mag using lead bullets with gas checks. Obviously the loading tables specify gas checks for certain loads, but is there a rule of thumb for then gas checks are required/desired?

Also, is there anything to be gained by using gas checks with some of the lighter loads?

[Sevens]

USED to be back in the day that your guideline was around 1000 fps or under, you didn't need jacketed or gas checks. That's likely been upped a bit, but the only way to really know is to see what happens with your barrel and the particular lead bullets you are using when you push them too fast.

When your barrel leads, it loses accuracy quickly and you'll find out what a job it can be to clean, and how much lead comes out of it as you scrub and scrub some more. I've done it.

There is nothing to be gained by using gas checks with low velocity loads. If anything, it's a little harder on your barrel (like jacketed bullets) than simply sending lead bullets down the bore. But it's also not something that I'd worry about. Modern firearms are pretty darn tough.

[LHB1]

First thing is you can ONLY use gas checks on cast bullets with rebated heels made to fit gas checks. They can NOT be fitted onto standard cast bullets. There is no benefit to be gained from using them with light loads. Read many years ago that using gas checks with a given cast bullet load typically increased the pressure by approx 5000 psi. For what it's worth, I use bullets cast of old wheel weights in H&G molds and lubed with ALOX (50% Alox and 50% beeswax). Firing these rounds thru S&W M629 .44 Mag pistols with 6.5" barrels yields 1400-1425 fps thru Oehler chrono with no visible leading after 50 rounds. YMMV.

Good shooting and be safe.
LB

[Dogjaw]

I'll only add that gas checks act like a heat shield on the base of the bullet, preventing the base of the bullet from melting in the barrel from heavy loads. I've considered using them, but unless you make your own the cost is right there with jacketed ammo.

[fatherofsmith]

flechets, legal or not, loading data available anywhere for 12 ga.?

[Crankylove]

How did this thread go from gas checks to flechet rounds?

[fatherofsmith]

oops, my bad, not used to the forum yet, getting there though. please forgive me

[NuJudge]

A lot of revolvers have a tight spot in the area just ahead of the forcing cone, caused by the threading of the barrel. This can cause bullets to be sized down at that point, and then be undersize the rest of the barrel length, with attendant gas blow-by and resultant Leading. A gas check will dramatically reduce this.

Some firearms just have rough bores, and will Lead, but less so with gas checked bullets.

[bluetopper]

With all the talk of leading........I'm surprised but I've been pushing 44 Mag 240gr plain cast lead SWC bullets at 1,300fps without any leading in my 6 inch 629-6.
Shot at least a thousand of them using 2400 powder.

[Unclenick]

Keep in mind that Elmer Keith developed the .44 magnum using 20:1 lead:tin alloy (and maybe even 30:1; I've forgotten) and no gas checks. You really just need a gun in good condition. Get your cylinder chambers reamed to SAAMI maximum and if you have the constrictions mentioned by NuJudge, lap them out or firelap them out (do any firelapping before having the cylinder reamed so it doesn't open the chamber throats up too much). A lapped barrel will lead very little all the way up to surprising velocities.

In manufacturing, .22 rimfire bores are often rather smoother than some larger calibers. I don't know what process differences may be involved, but they will shoot those little waxed soft lead pills to the speed of sound and a little beyond without leading becoming a big issue. It follows that the same is true for bigger bullets if you don't overheat the bases.

Dogjaw is correct about the heat shield effect. Some years back Merrill Martin published some experiments he did with polywads (or P-wads). These were just discs cut from 1/16" low-density polyethylene (LDPE) sheet using a fired case that had been sharpened with a chamfering tool. This was so the wads came out slightly tight. The wads were placed in the case mouth after charging with powder, then the bullet seated over them. He shot up to fairly high velocities (2200 fps or so, IIRC) and his borescope revealed no leading whatsoever. The LDPE would melt and lightly coat the bore, making a good lube (nothing much sticks to it).

It seems to me someone was making even thinner wads by cutting up milk cartons, but I don't recall how effective that was? I recall they had to be stuck to the bullet base with lube to keep from turning or falling off the bullet in the case. Cardboard wads would make a perfectly good heat shield, too, though they won't absorb heat by melting as the plastic will. Nonetheless, they are good enough insulators that heat won't get very far through them in the time a bullet has in the barrel. The limitation will be that cardboard won't expand to obturate behind the bullet as easily as the LDPE wads do, but its all food for experimentation. Cardboard can be soaked in liquid Alox lube.

Two warnings:

If you start messing with wads, be aware they are subtracting powder burning volume from your case and will raise pressure, especially in pistol cases. You need to work your loads up over again when using them.

Don't shoot loads with loose wads behind the bullet over a chronograph. The wad normally separates from the bullet at some point and its aerodynamics are not conducive to straight flight. The old non-crimped gas checks were known for separating and doing a number on sky screens, too.

[WESHOOT2]

You need them when serious leading occurs, or to enhance accuracy.