Aluminum gas checks

[fg-machine]

I am firmly in the not worried about wear crowd .

What I have noticed with aluminum checks is they don't seem to stay on the shank quite as well as copper does if your using a harder alloy . I had this same issue back when you could still brass checks .

What it boils down to is i get a "flyer" a little more often then I used to when using copper and on occasion I'll find a shiny gas check in the lane between bench and berm .

Don't take any of that as me bashing aluminum checks , I haven't bought copper since sage started selling aluminum.

[parkerhale1200]

I am making my own alu gs.
I did not see any difference in the barrel and end result regarding copper or brass.
Alu is cheaper, easier on my tools and preforms the same.

I also shoot 308 without gs full jacket loads...with no need to clean.
Brings us to the purpose of the gs itself.
I believe that is a other tread and much debated on this forum.

Go with alu and dont lose a second of sleep, what is the worst that could happen?????a extra cleaning session.

[parkerhale1200]

I am firmly in the not worried about wear crowd .

What I have noticed with aluminum checks is they don't seem to stay on the shank quite as well as copper

Yes the problem with alu checks.
You need to do it twice thru the lubasizer.

First a "dry run" to make what ever amount you want, then lube.
The problem is that alu is to soft to let the grease stay out. so it will let the grease in, thus a lose gs and possible a hole extra on the target(-:
Sorry you have to size twice, one dry and one with pressure on the lube.
Works for me perfect.
I also dont think alu gs will hold in a star sizer.
Most sizers are pressing on the bottom, thus creating extra to let the gs stay on.
Sorry for my bad English, i really hope this was helpful for you.

[2TM101]

I will use gas checks if I can make them myself, and there is an advantage to it. I can even make them out of Copper as I am now doing percussion caps that way. For that matter if a gas check, powder coat, and lube used together gets me up to jacketed bullet performance I will do all three.

[gloob]

If the check is made to fit properly to the shank and it's the right material thickness to swage the shank 2-3 thous as it crimps, it will seat and stay on tight. Some of the aluminum checks are made with slightly different thickness and dimensions.

Also works if the shank is made to fit to the check. I swage a gas check shank onto my PB bullets so that the checks go on consistently.

I've found 2 ways a gas check easily pulls off the boolit and will fall off in flight. One is if the check material is thinner than the difference between shank diameter and bullet diameter. The other is if the ID of the check is too small for the shank. Then the sizer squeezes the mouth of the check to the boolit while there's a large pocket of air between the bullet and check, so it's barely hanging on.

[Dan Cash]

I think some aluminum gas checks are too hard which increases their spring back and makes them prone to fall off the bullet shank. I have anealed my check material and fine the resulting gas checks seem to griip the bullet better.

[parkerhale1200]

I will use gas checks if I can make them myself, and there is an advantage to it. I can even make them out of Copper as I am now doing percussion caps that way. For that matter if a gas check, powder coat, and lube used together gets me up to jacketed bullet performance I will do all three.

i dont powder coat, and still i shoot pb's at full jacket speeds with alu checks.
44mag even without gaschecks at full jacket speed.
It is all in the hardness and tight fit of the boolit.
I shoot 308 with gaschecks, not for fouling but for accuracy.
For my ar15 the same, ps still no fouling in my gas pipe after almost 10.000 shots.

Get over your cold-water fear and dive in(freely translated Dutch saying, positive meaning btw), if you lived close by i would invite you.

[parkerhale1200]

I think some aluminum gas checks are too hard which increases their spring back and makes them prone to fall off the bullet shank. I have anealed my check material and fine the resulting gas checks seem to griip the bullet better.

Its not about the hardness(alu is softer than copper btw) i think you are referring more to the memory of the material.
i think also you need a slighter thicker aluminium sheet.
Soda cans are to thin.

Anealing is to "reset" the materials memory and to softening the material up before the next stage.

[405grain]

"For that matter if a gas check, powder coat, and lube used together gets me up to jacketed bullet performance I will do all three."

It's not realistic (or desirable) to expect jacketed bullet performance (velocity) from cast bullets. From a hunting aspect, cast bullets do not have a copper jacket that needs to be overcome for the bullet to expand. Cast bullets expand normally at much lower velocities, and would probably come apart violently with little penetration if fired at jacketed velocities. If cast from a hard enough alloy to get good penetration at high velocity they would probably lack good expansion.

From a target shooting aspect, fired at jacketed velocities cast bullets would be spinning at an rpm that exceeds their tolerance for good accuracy. Generally cast bullets begin to loose accuracy once velocities start going above 2000 fps. There are some specific target cartridges, load combinations, and barrel twist rates that can allow for higher velocities, but these are in specialized target rifles build for competition. As a general rule, for best results with most rifles (both for hunting and target shooting) velocities should be at around 1950 fps or less. There are always examples where people can load a little higher, but these are usually the exceptions, not the rules. Cast bullets work great when used in their best range of velocity.

[2TM101]

"For that matter if a gas check, powder coat, and lube used together gets me up to jacketed bullet performance I will do all three."

It's not realistic (or desirable) to expect jacketed bullet performance (velocity) from cast bullets. From a hunting aspect, cast bullets do not have a copper jacket that needs to be overcome for the bullet to expand. Cast bullets expand normally at much lower velocities, and would probably come apart violently with little penetration if fired at jacketed velocities. If cast from a hard enough alloy to get good penetration at high velocity they would probably lack good expansion.

From a target shooting aspect, fired at jacketed velocities cast bullets would be spinning at an rpm that exceeds their tolerance for good accuracy. Generally cast bullets begin to loose accuracy once velocities start going above 2000 fps. There are some specific target cartridges, load combinations, and barrel twist rates that can allow for higher velocities, but these are in specialized target rifles build for competition. As a general rule, for best results with most rifles (both for hunting and target shooting) velocities should be at around 1950 fps or less. There are always examples where people can load a little higher, but these are usually the exceptions, not the rules. Cast bullets work great when used in their best range of velocity.

Makes sense. I don't need max performance, its more my wanting to see how good a bullet I can actually make. I do not have any bullet molds for gas check bullet and at present could only do the plain base aluminum ones, which I would do mainly because its something new I have not tried yet. I do not *need* the better performance. In truth I powdercoat so I do not have to handle exposed lead, the fact it makes the bullets better is a plus.

What got me started on this is I have a lot of military surplus ammunition that is steel core and the ranges do not want me using it out here. I want to be able to pull the bullet and replace it with something I can make that will still work OK, and I figure I need every tool I can use to do that.

[2TM101]

I've found 2 ways a gas check easily pulls off the boolit and will fall off in flight

I thought a gas check was like a shotgun wad or a sabot. Does it really matter if it comes off once its out of the gun?

[gloob]

I thought a gas check was like a shotgun wad or a sabot. Does it really matter if it comes off once its out of the gun?

Depends on why it fell off.

If it was barely clinging by the mouth, then that's bad. When you fire the gun, the check doesn't get pushed onto the bullet. It just gets mashed in, inside out. So there's no bullet in there to press the sides of the check into the grooves. The check doesn't help to seal the gases and it falls off after the bullet exits. But it still cools jets of gas that are blowing past the first leaks in the boolit.

[gloob]

Here's a picture of some of these inside-out checks I recovered. I knew the checks weren't seated consistently and the OAL's after seating the checks was all over the place. I had already come up with a better way to seat the checks. I just wanted to see what would happen.

There are no rifling marks on these fallen-off checks.

[405grain]

Gas checks need to crimp on the base or heel of the bullet. They become part of the bullet. Their main job is to prevent hot high pressure gas from leaking past the bullet. If that happens, the gas will vaporize lead off of the surface of the bullet. Once the bullet exits the barrel and the gas cools that vaporized lead will condense and begin plating on the inside of the barrel. Once this thin layer of lead plating builds up enough it will start galling against bullets as they pass down the barrel, smearing lead inside the bore. Before very long you'll have barrel leading. Gas checks help prevent the gas blow-by that starts this process.

The gas check also strengthens the base of the bullet so that it is less likely to deform under high pressure. Uniformity of the bullets base is more important to accuracy than the nose is, so gas checks help bullets retain accuracy at higher pressures and velocities. Generally, non-gas checked bullets preform well up to around 1400 fps, and sometimes can get to 1500 fps before they start getting into trouble. Moderate velocities with plain based bullets can be quite accurate.

If a gas check comes off the base of a bullet in flight, unless it just plain falls off, it is unlikely that it will come off uniformly. If the gas check gets torn off like prying the lid off of some container the bullet will become unstable and will wobble in flight. This won't be doing accuracy any favors. Around 120 years ago, when gas checks were first being experimented with, they were designed to fall off in flight. This didn't always work so well because sometimes they didn't. It was soon decided that it was better if the gas check was designed so that it would stay with the bullet during it's flight. Fun fact: the first cast bullet to be designed to use a crimped on gas check was the Lyman #311284 for use with the 30-40 Krag.

[Gunslinger1911]

I ran plain base pop can alum gas checks (Pat Marlins) ever since he came out with them. Nary a problem.
Solved a few issues over the years.
Thousands of rounds down range with alum GC.
I would guess the military issues with alum come from the high rate of fire, ie heat (like 4000 rounds per min)
For me, powder coating has replaced GC's. Think 125g .357 at ~2000 fps - no leading !!!! (but, WHAT a ball of fire !!!)