Aluminium Gas Checks

pantannojack · Dec 14, 2023

I like shooting cast bullets in my 30-06's. My hard bullets with copper gas checks have been leaving no lead behind at up to 1850 fps possibly much more. I get near MOA accy out to 100 yds I don't even know what factory jacketed bullets cost anymore, but my home poured come to around .08$; factor in I use half the powder, it is a fun savings.

Question: Has anyone used aluminium gas checks? If so does the metal build up? and if so is there any solvent which can remove aluminium fouling?

505Gibbs · Dec 14, 2023

OK - I'll bite! Never heard of gas checks in aluminum! Very soft material for this type of usage - IMO.

colt_saa · Dec 14, 2023

The 500 S&W Magnum was introduced at the 2003 SHOT show in Orlando FL.

I began developing loads and shooting the cartridge in the summer of 2002

Having been such an early adopter of the 500 S&W Magnum, jacketed projectile choices were difficult to come by and cast projectiles really did not exist.

These are the first molds that I had made. The projectile designs are from John Ross who also began his 500 journey early

As you can see all of my molds are plain base. I cast from #2 alloy and water quench the projectiles.

The big wad cutter on the right drops at 725 grains, while the little semi-pointed projectile on the left comes out at 450 grains.

Those water quenched 450s leave the 8 3/8 revolver at a chronographed speed in excess of 1750 FPS and have never been a leading problem.

Out of my 12" Encore they are faster, but I can not find my chrono notes on those

As the years went on I had some molds made for lighter projectiles going down to 350 grain on that semi pointed design (still plain base). Several loads topped 2000 FPS in the revolver but I was worried about the Encore

I had already been shooting a water quenched plain based cast projectile in my 300 Weatherby.

With these two cartridges easily able to exceed 2000 FPS I began looking for an option other than replacing all my molds with redesigned projectiles.

The answer came from a innovative gentleman named Pat Marlin. He came up with a die that would punch out discs from thin metal strips.

Now you can purchase copper and use that or . . . . You can cut strips of metal from soda and beer cans for use as your gas check made from his die (this makes gas checks very cheap).

The die creates disks that seat to the plain base projectile as you size, just like with a GC bullet design.

images courtesy of Pat Marlin

All of my plain base gas checks have been made from aluminium soft drink cans. In probably 15 years I have never experienced an issues with aluminium buildup

While I personally have not done this, he also makes a die designed for gas checks that are to be used on GC designed projectiles. You will notice in the last image above some packages have PB after the diameter and others do not

Forrest r · Dec 14, 2023

alunimum 30cal gas checks (gc's) that I made at home from annealed roof flashing.

Home made gc makers that I made to make my own gc's at home.

I made home made gc makers for the 22cal's/30cal's/35cal's/44cal's.

The al gc's stayed on these 30cal "ness" bullets. You can see them on what's left of the bullet's bases.

I made/tested a rounded edge gc for the 30cal's. Didn't make any difference in accuracy/consistency.

Never had any issues with aluminum build-up in any bbl.

I did run into accuracy issues with them when pushing cast bullets over 2400fps with 35,000+psi loads. Unexplained fliers started showing up & I traced it back to the al gc's.

What a 308win bbl looked like after 30 rounds using a cast bullet/al gc combo.

That bbl cleaned right up with hoppe's #9 and several strokes with a bronze bore brush.

Alk8944 · Dec 14, 2023

The efficacy and utility of gas checks are greatly over-rated. I have been shooting and casting lead bullets for over 60 years for both rifles and handguns, and have long ago discovered that the two most important factors are bullet fit and lubricant. So far as fit is concerned sizing .001" to .002" over groove diameter works better than sizing to groove diameter as usually recommended. For lubrication the best lubricant I have ever used is Saeco Green. This Saeco lube worked better than any other I have ever used including LBT or any of the other "boutique" lubes that cost much more. Many years ago I was given the formula for the Saeco lube by a former Saeco factory rep. I make my own for about 1/5 the cost, or less, than the cost of the commercial version.

If you insist on using gas checks the Aluminum (U.S. spelling

) ones will work just as well as Copper, and at a lot better price!

mtgianni · Dec 14, 2023

Forrest r said:
alunimum 30cal gas checks (gc's) that I made at home from annealed roof flashing.
.

I did run into accuracy issues with them when pushing cast bullets over 2400fps with 35,000+psi loads. Unexplained fliers started showing up & I traced it back to the al gc's.

What a 308win bbl looked like after 30 rounds using a cast bullet/al gc combo.

Forest, have you tried powder coating and al checks? I never found the top end but found I could push pc'd 7-30 bullets with al checks to 2550 fps which was probably the top end of my alloy.

Green Frog · Dec 14, 2023

One of my first moulds was an old Ideal 358156 which of course is cut for a gas check. I must admit though that very few of the bullets I cast from it actually got gas checks. They always shot well enough for me “naked”.

Flash forward about 40 years and I met a well known caster who goes by the screen name “beagle”. We share a liking for the various 32 revolvers and he showed me a more recent Lyman mould, the beautiful 313631. He had gotten it modified to remove the gas check shoulders in both cavities and had one cut for a hollow point… the dream mould for hot 32s.

I mention this because beagle also had some aluminum gas checks he punched out of aluminum drink cans. At the time he told me who had made the tool he used to make them, but it’s now been several years, so I’ve forgotten who made it. The point of all of this is to report that those gas checks were made to be squeezed onto the rear surface of the bullet during sizing - no cast groove required. I was given a supply of them so that I could gas check whichever 32 pistol bullets I felt needed them. That’s what makes aluminum gas checks interesting… you can use them on any bullet you wish, not just those from moulds cut for gas checked bullets. I’ve used them in some bullets in 32 H&R and 327 FM loaded pretty heart without cause for complaint.

Froggie

Forrest r · Dec 15, 2023

mtgianni said:
Forrest r said:

Forest, have you tried powder coating and al checks? I never found the top end but found I could push pc'd 7-30 bullets with al checks to 2550 fps which was probably the top end of my alloy.

Click to expand...

Absolutely, when I started pushing the cast bullet with high pressure loads. A bunch of different issues kept popping up. The use of al gc's happened to be 1 of them.

Bullets cast from a 2-cavity cramer mold. A sp bullet design with e cavity having a hp pin.

Typical groups no matter what powder I tried. The nose of the sp bullet would slump causing the groups to open up (left). The group on the right has fliers from the al gc's.

A strong nose design is highly recommended when pushing cast bullets hard. The lee tl-160gr bullet is an excellent design for pushing cast bullets hard.

Did head to head testing with that bullet traditionally cast & lubed vs pc'd.

The traditionally lubed bullets didn't have enough lube. Used the same cast bullets with the lbt lube and gave them 2x coats of tumble lube and re-tested.

While 2" groups are considered terrible with jacketed bullets. They're average when pushing a cast bullet hard. Anything 1 1/2" or less is considered good.

Same bullet slowed down to 1800fps. 10-shot 1" group top left target.

I been tied up with other things the last 2 years. Need to get out and start doing more testing.

Patrick L · Dec 15, 2023

I've played with them. I too bought a Pat Marlin checkmaker. They worked. Since there are reasonable cost suppliers of conventional copper checks (Sage, Gator) I sort of packed the Checkmaker away for a "what if" doomsday/zombie apocalypse scenario. But it was gratifying to know I could make my own if I had to.

The one thing I don't know is if there are any longterm fouling effects. I didn't shoot enough of them or shoot them for long enough to test that.

Pig Hunter · Dec 15, 2023

It has been reported when pushing cast boolets at high velocity the rpm of the projectile can result in the boolet coming apart. Larger, deeper grease grooves can be a point of failure.

rwsmith · Dec 15, 2023

Never heard of them either....

505Gibbs said:
OK - I'll bite! Never heard of gas checks in aluminum! Very soft material for this type of usage - IMO.

...but I suppose that if the right alloy is used they won't be so soft.

.

Skeet 028 · Dec 16, 2023

I have one of the Par Marlin Checkmakers. I've never used it ro make a bigbatch. Yea it works. well in fact I tried putting the on non gas check bllets and found about 1/2 awparate from the bullets. They work well on gas check bullets. If I remember there was some concern with the coating put on some aluminum being very hard on bores. I have seemed to pick up more gas checks than I need for little cost at gun shows etc. I even got 41 cal and SIERRA 30 cal checks at an estate sale not long ago. I only load one rifle bullet with checks the 311-410 I think...for my 30-30s

Aluminium Gas Checks

pantannojack

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505Gibbs

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colt_saa

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Forrest r

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Alk8944

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mtgianni

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Green Frog

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Forrest r

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Patrick L

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rwsmith

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