Slip on vintage Lyman gas checks vs modern copper crimp on gas check accuracy?

[Tripplebeards]

I just got a box of Lyman gas checks on pay it forward here. Looks like they (I’m guessing) are the old style slip on style and not made out of copper? They are golden color and have a little bit of spotting, her oxidation, rust, or something on the inside which tells me they are something other than copper.. I’m just wondering if there’s gonna be a change in accuracy using these versus the modern style crimp on copper checks?



Pretty looking vintage box. Doesn’t look like there’s a crimp ring on the inside of the checks where they would grab onto the bullet. I use a lee sizer when seating the hornady GCs. I assume I could seat these the same way?

[TomAM]

I was using those extensively, 50 years ago.

Saw no change of impact and certainly no accuracy difference when switching to crimp ons.

The only "problem" with the non-crimp type is they can fall off during handling if your shank is a bit undersized. That just requires slipping it back on while loading into the case.

Many folks believe they'll fall off in flight, but I've recovered dozens of my bullets, fired into a deep snowbank (once thawed) with all GCs still attached. They are swaged on much tighter by the lands when fired.

[Tripplebeards]

I size and seat my GC. Then I tumble PC. Maybe I’ll change up a few steps in the process. I size and seat the GC. The. Tumble PC and size again to squeeze down the extra 2,000th of PC coverage. At least that way the GC will be sealed over and kind of “glued” in place?

Good to hear they don’t change groups. Don’t want to mess with the pet load in my avatar. lol

Any idea what the alloy used in these are?

[Tripplebeards]

The more I look at the color I wonder if they’re made out of brass???

[mehavey]

FWIW:

I Seat/Size/PC-shake/Bake/Size-final
(All Lee push-through)


And once fired, the bullet rather dramatically swages
itself together w/ the GC in the 1st millisecond ...no
matter what

[ascast]

I think bullet design may factor in here as well. A couple of old Ideal designs had a pronounced taper too the shank,not a boat tail, not a bevel base but a taper. I recall two: One was a 45 ACP bullet ( ? ) and the other was a the 228467 made for he Savage HP. I can report back on this about August. Finally got that mold and can test it. I think a regular square shank will hold these fine. I know the talk for a century or so is they fall off in flight. Check archives. IIRC there was a detailed discussions a couple years back.

[Tripplebeards]

I read that too, and supposedly makes it less accurate in the process. That’s why I figured I would try and figure out how to keep them from coming off. I’ve got a good plan as already mentioned by others. I’ll just make sure that my Lee push through sizing dye is super clean so PC will stick to my bullets when I tumble them afterwards. Then I’ll size a second time. I’m sure they won’t come off after that. I’ll also clear PC so I can see the “bond” between the PC and GC.

[turtlezx]

I put a drop of super glue in them then seat boolit .Dont size or crimp them just load
rather have hornady fit tight but got these as you did PIF so i use them

[Tripplebeards]

Think I’m gonna stick with the original plan and install them while running through my lee sizer, then powder coat, then resize through the lee again. I’m sure they’ll probably work great.

[dtknowles]

I use Lyman gas checks on my bullets cast from a Lyman mold for my 30-30 for decades without any issues. Yes, I think they are brass. I bought a box of 1000 when I first started casting back in the 70's and the box is not empty. Who shoots more than 1000 rounds of 30-30? We I guess if it was my only rifle I would have used them up but not only is it not my only rifle, I have, gasp, shot almost as many jacketed bullets in it and more than a few plain base cast bullets, oh and a few of those accelerator thinges with cast 22 bullets and j-words.

I am not fussy about Gas Checks, I use whatever I can pickup. In a pinch if I have to mail order I would go with Hornady.

Tim

[JonB_in_Glencoe]

they are brass and they are thinner than Hornady.
Also, they work great with the older Lyman and Ideal molds...that's what they were made for.
They will probably work OK, with other molds, but if you end up with some issues, that could be why.

I have an old Ideal 358156 mold, and it only likes the old Lyman (or Ideal) GCs.

[gloob]

Brass has much lower thermal conductivity compared to copper. It's only about 1/3 of pure copper, IIRC. Particularly in calibers with thinner gas checks, that may make some difference in the max speed/pressures you can get with a given bullet.

Aluminum has much higher thermal conductivity than brass. Almost as good as pure copper... but that's by weight. Since aluminum has much lower density than brass and copper, aluminum checks should also fall short of the performance of pure copper checks, if you care to push to max velocity for a given bullet/alloy.

[Tripplebeards]

I’ll be using them in my buy MP .358 200 grain HP mold. It’s the group and load data in my avatar that I use with 40 grains of Varget. I’m sure if my groups open up a hair because of a different style gas check at the groups I’m currenty getting, that you can see in my avatar, it’s probably not gonna make much of a difference.

[magusina]

I just got a box of Lyman gas checks on pay it forward here. Looks like they (I’m guessing) are the old style slip on style and not made out of copper?
Pretty looking vintage box.

I don’t suppose the box looks like the one in the attached pic?
Mate, I’d love to purchase these gas checks from you. I’ve been looking for .35” brass gas checks for a long, long time!