Gas Checks - Copper vs Aluminium

[LubeckTech]

Are Copper gas checks better than aluminium?
I mainly load .30 caliber boolits in various cartridges for velocities between 1,500 and 2,000 fps. At this point I am buying them but hope to eventually make my own. Copper checks are 3.6 - 4.0 cents ea and aluminium 2.5 - 2.8 cents ea.

[colt1960]

I only use hornady copper gas checks myself. I prefer there crimp on design. Less likely to come off. Rick!

[sthwestvictoria]

I have trialled the aluminum .30 calibre checks from sagebushoutdoors that were gifted to me. The certainly stay on all the way to the target - I've pulled them out of my rubber boolit trap media.

[357shooter]

Aluminium work just as well, in my opinion. I rarely exceed 2,000FPS, things may change north of that velocity.

[44man]

Keep velocity low and aluminum should be OK. They will not stop skid as good as copper.

[Larry Gibson]

Yes the copper GCs are better at higher velocities. However, if the aluminum GCs stay on the bullets then they do quite well at the velocities you are using them at. Some find aluminum ones do well at HV when annealed but if making your own are the extra steps really saving you anything?

If you don't really shoot a lot 1000 commercial Hornady GCs are really that expensive for a quality product.

Larry Gibson

[williamwaco]

I have shot thousands of copper checks over many years.

I have shot maybe 100 aluminum over the past couple of years.

I was perfectly happy with the aluminum but I did not use them above 1900fps.

I could see no difference in accuracy and they did not come off.

Mine were all .30 cal.

[JeffinNZ]

Alum. works fine providing you use a grade that is hard enough. I favour lithography plate that, in my neck of the woods, is 3XXX series. Any alum. softer than 3XXX I have found to be too soft.

[rhadamanthos12]

I tried digging through old post for this answer, but it would seem to fit here. I use aluminum checks and haven't had an issue yet. However, I have only pushed the velocity to bout 1800fps. I want to get into the 2400ish range, from what I found in older threads people are saying that after 2000fps that aluminum checks start to slip and groups open up. I'm curious what is the highest velocity someone has gotten with Al checks without leading and keeping a decent group (not the same as jacketed, but slightly larger)

[gvanzeggelaar]

Larry,

I epoxy my aluminum gas checks on. What is your opinion on using these at higher velocities?

[44man]

Larry,

I epoxy my aluminum gas checks on. What is your opinion on using these at higher velocities?

That is not the problem. Engaging rifling actually tightens the check. Jeff made a good observation about aluminum hardness. Most is too soft to halt base skid so there is a point where a PB works the same and aluminum only lets you go a tad faster.
Beer can aluminum is too thin.
When you shoot fast, you need a tough check to seal the rifling and help the boolit spin quick. Go too fast and the check will still skid. Then you need a harder boolit but there is still a limit.
A check is NOT needed to protect a boolit base from powder, a check is to grab the rifling with no gas passage.

[Screwbolts]

I have shoot over 500 alumunim at of 2300 FPS out of 2 Armalite Rifles, AltHeating gave me a bunch from Litho plate and they worked as good as Gators. The rode all the way to the steel plate and when we had a thaw the ground was littered with tiny aluminum discs.

A fellow on Weapons Guild sent me several thousand and they shoot well also on 5.56 Nato boolitz and Noe 55- 225.

Ken

[HARRYMPOPE]

a check does protect and strengthen the bullet base.i have experimented quite a bit with it in 30 cal rifles and recovered bullets of well fitting PB had gas cutting where GC of the same had none.Mold was a std GC mold with 1 cav's GC shank removed.Load was going 1600-1900 fps with 2400 powder(too fast for best PB shooting really)With 4895 just powder impact marks were on the base(no cutting) but no accuracy with PB.

[44man]

a check does protect and strengthen the bullet base.i have experimented quite a bit with it in 30 cal rifles and recovered bullets of well fitting PB had gas cutting where GC of the same had none.Mold was a std GC mold with 1 cav's GC shank removed.Load was going 1600-1900 fps with 2400 powder(too fast for best PB shooting really)With 4895 just powder impact marks were on the base(no cutting) but no accuracy with PB.

Cutting is when the base band skids and opens channels for gas to go. Once the rifling marks at the base get wider then the rifling, gas will cut. A PB will be the first to fail so harder is needed but soon it is also shot. Aluminum then will help until it fails and copper is best but soon it will skid too.
You do not make a base stronger just for powder dents, you try to make the boolit take the rifling with no gaps.
A few think lube will seal the extreme gas pressure if it leaks past the base. It IS a funny thought!
If you collect enough fired boolits and study them you will see skidding at the front and that is common with lead. As the marks get near the base they get smaller as the boolit starts to spin. All is good as long as the base band does not have enlarged marks over the actual measurement of the barrel grooves and lands.
NO, soft boolits that "OBTURATE" do not halt spin skid.
The entire solution for max velocities will always be a jacketed.

[felix]

Jacketed means about anything other than naked lead alloy, and also properly checked when the "jacket" material is something like a paper product. Boat tails require solid jackets. ... felix

[longbow]

Good observation 44man!

I always try to recover boolits because they tell me lots about what is happening.

Lately I am shooting mostly Lee Enfields in .303 and started out having issues with leading and poor accuracy with both GC and PB boolits.

Recovered boolits showed wide grooves in the boolits so channels for gas. This is with ACWW and boolits sized to throat diameter.

Every time I started to push velocities from beyond mild loads, I got leading and poor accuracy where this had not been a problem in a .308 with 1:12" twist. I figured the faster 1:10" twist and heavy boolits with short groove diameter bearing length (Lyman 314299) were the problem so tried oven heat treating and that solved it.

My PB boolits were from a home made mould but modeled on the 314299 so relatively shot bearing length and lots of nose/bore rider.

In both cases, the harder boolits showed nice even engraving with no wide grooves in boolits.

Longbow