At a loss--help

[lastborn]

posted this on the GC page but there's nobody viewing over there. So here goes.
I have two 45/70 molds. One is 460425 FNGC and the other is a 460350 FNGC. Boolits drop .460 from both molds using 97pb-2sb-1sn alloy.I have a Lee .460 push through sizer as well as a Lee .4585 push through sizer.Using Hornady 7140 gas checks. Here is my problem / question: after running through either sizer I can pop the check right off with my thumbnail. I would think they would grip much better than that? Are they supposed to? If they don't stay on all the way to the target won't they be less accurate?
Please help! I want to load some rounds to get the gun sighted in, but don't want to waste primers,powder and lead in the process.
thanks

[45nut]

try annealing the gas checks ,, that will soften them a bit and not spring back when sized.

you can anneal them in a skillet on the stove,, get them red hot, then air cool.

[HeavyMetal]

And that sums up my beef with Gas Checks!

On those molds that I do have that are GC'd I use a touch of Super Glue to hold the check on.

Then size as needed.

So far it has proven to work with no issue

[rockrat]

You might get some 458 Rifle gas checks from "Blammer", over on the group buy site. I only use the Hornady check for my pistol bullets.

[Bullshop]

The Hornady 45 cal checks are for both rifle .458" and pistol .451". They must fit the check shanks of both size boolits. Sometimes they just do not crimp on hard enough to stay put especially if sizing on the high side of .458" and coupled with a mold that is a bit undersized at the GC shank.
Oft time I have set the checks to the boolit in a smaller die, say .457" but have the check seater installed in the press to limit the amount of entry of the boolit into the die. Then in a second operation size/lube the rest of the boolit in the size die you want the boolit to be. This can work but can also result in the set check being slightly smaller diameter than the rest of the boolit. As long as the alloy is not too hard these will still work normally especially if the checks have been annealed.
Another option is with the Gator Checks. Larry makes two different size 45 cal checks, one for rifle and one for pistol. They can solve the problem in some cases but are not always a cure all either. Some molds just plain have too small a shank for any of these things to help and will need to have the shank portion opened to remedy the frustration.

[Rangefinder]

Were I you, I'd get a wooden dowel, a piece of 1500 grit wet-dry polishing paper, and polish out the mold a little in the shank area. if the check pops off so easily, it isn't gripping enough lead. enlarge the shank a couple thousandths and you'll get a tighter crimp. from there on, you should run trouble-free.

[excess650]

I received my NOE 460-350 last week. After casting I tired both Lyman and Hornady GCs, and both were pretty tight going on. Visually, I couldn't tell the difference between them.

You might just try loading and shooting some of those projectiles and see what the targets look like. Even though you're sizing .459", the bore is tighter, so the lands will further crimp the GC.

Your anitimony content is pretty low, so will cast a smaller diameter. Adding antimony will increase diameter as well as making the bullet harder. If you're intention was soft bullets, and the loose GC fit is a problem, enlarge the GC shanks in the mold.