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So if I seat the check via a top punch (inverted) checks seat fine but I just noticed a slight “dome” it was creating. Right side up naturally check is more “concave”. Would this really affect blow by?
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Left is check going in first, right is pill going first.
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Your top punch keeps the bullet aligned with the die. Doing it inverted won't do anything good for the overall straightness of the bullet nor the squareness of the seated check.
Do it the way the sizer was designed to work.
I have an NOE sizing kit (.265) and they included a top punch holder specifically to size bullets base first. This is supposed to crimp the check a little better to bullet. My question was about it creating a slight dome at the base of check.Quote:
Originally Posted by uscra112
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If the GC is seated square, I don't think the dome will make any difference.
The old Ideal handbooks told you to use a flat-face bottom punch for plain lead, a slightly concave one for gas checks. Purpose being to keep lube from getting between the bottom punch and the bullet. Lyman dies at least come with a concave bottom punch. The other end is flat, though. Try flipping yours over to see what happens. The chamfer won't be any problem since you're sizing a powder-coated bullet.
Will do. I usually “pre-seat” all checks by using the flat side of the nose sizer and the push rod. This is the only way I can get them square.Quote:
Originally Posted by uscra112
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I've never powder-coated a bullet. (only motorcycle frames). Is there plastic on the base that might interfere with getting the GC seated square?
No but there's a minute pesky miniscule ridge around the base that I have to ever so slightly chamfer to get the check on without shaving off lead. I always cull my bullets making sure each and every one was evenly cut with sprue. I'm beginning to think that when the manufacture the checks, the walls are not straight but rather turn inwards ever so slightly.Quote:
Originally Posted by uscra112
I you're using Hornady checks, you're right, sorta-kinda. They have a slight burr at the mouth of the cup that helps them grip tighter. The checks that Sage's sell do not have this, and I have had them pull loose as I remove the bullet from the lubrisizer.
Depends on bullet design and gas check. I found that with some bullets like RCBS and Lee (30 cal) and my homemade GCs Lubrisizer does a better job of seating (grip better) and no need to pre-seat them. With NOE I get perfect results with Lee push trough die, bases are square and never concave. If you powder coat first than yes you need to seat them first to make sure they'll seat even and square. If you have NOE punch shell holder, you can get a piece of 7/8 - 14 rod or bolt with flat face and screw that at the top with ram extended all the way up you screw it in until it touches the bullet top and than just a little more that way you have always consistent seating for all your gas checks. Be careful though because if you screw in too much you can end up with bullets becoming "thick" and ending up being .312+ in diameter which might or might not be desired effect.
PS. I made my own bullet holder out of delrin, its very simple.https://uploads.tapatalk-cdn.com/202...a20ba49b5b.jpghttps://uploads.tapatalk-cdn.com/202...3c38e4b4a5.jpg
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I wish they made molds where you could pre-install checks and then pour "nose first". Of course this would only work with FN bullets.
I'll get a slight dome on bullets from specific molds and not on others. An example would be, never on my MP 314-640 115gr and always on my MP 314 Sledgehammer. My Sledgehammer has a fat GC shank that won't allow a GC on without using a NOE edpander, and the -640 will allow the GC to click on. Both of these bullet molds drop very accurate bullets. I don't see the slight dome as a detriment to accuracy as it's consistent as the sunrise. All of my bullets are PC'd and sized with Lee dies.
I'm gonna leave em as is. If a boat tail can go sailing straight then these will. Never could quite figure out that analogy with boat tails and bullet getting a seal without gas cutting.
I would think that they would seal better. Pressure would be against the dome pushing it so it would be trying to flatten, causing the sides to push against the bore more tightly as pressure increased.
I’ve never shot any like this, but we are about to, out of my buddies Winchester 94 in 32ws. The die I have had a concave I piece and the gas checks are a bit larger in diameter than ideal. The results are perfectly convex bullet bases.
The only thing that matters is whether the check is exactly square to the axis of the bore as it emerges from the muzzle. If so, the escaping gas acts uniformly all round. If not it gives the base a little sideways kick. The bullet departs with some yaw. and in air it flies a spiral path. which may or may not coincide with the point of aim when it gets to the target. A bad crown does the same thing, which is why the crown is so important.
Last 2 posts make a lot of sense. I kinda had that in the back of my mind but I'm no physics major.
This is paramount to accuracy. The base must be perfectly square and flat. Any convex or concave would have to be the exact same for each bullet, which is a whole separate issue. Dead flat and square works.Quote:
Originally Posted by uscra112
I've heard this repeated many times until I slugged the bore and noted how initially flat base comes out deformed from the rifling cut in to it! There are ridges formed. Too bad I don't have a picture handy, so much for perfectly square base nonsense! In reality its very different!Quote:
Originally Posted by B R Shooter
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Squareness of the base and the furrows cut by the rifling are two entirely different matters, although the furrows must all be uniform or you'll get the same results as an out-of-square base. The matter of base squareness was proven conclusively over 100 years ago by Dr. Franklin W. Mann, with assistance from such geniuses as Harry Pope. Over the unsung generations it's been confirmed time and again by later experimenters.
Tried something today, I cast 300 200 gr. 358 boolits & gas checks were not going on easily. I put the last 50 boolits in the freezer for 1/2 hour, while keeping checks warm.checks went on much easier & squared. Checks should be tighter when temp is equalized. Warmed everything up & powder coated.
I wish I had seen this earlier today. I seated my first gas checks today and of course had my share of not square checks, but full steam ahead and all that. I'll try it next time.Quote:
Originally Posted by Yooper003
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To eliminate that, put the check on the bench, push the base onto the check, and leave the boolit standing up on the bench.Quote:
Originally Posted by Gibbs44
You can see it its off of being seated flat. Ones that are- I push 'em down a little harder.
If they're still 'difficult', I lay that flat wrench for the sizer on top of the die, and push it down square with the press.
There's a little tool for doing that, but I never felt the need for it.
Also, you can't find a picture of it--- that probably means it would be real simple to make.
Thanks for the info, I'll give that a try too. I figured it was probably procedural error on my part. I was pretty much chucking the check in the 4500 and sticking the base to it. Most were ok ish for playing around, but it'll be better next round.Quote:
Originally Posted by Winger Ed.
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This is correct ... my old Lyman 450 H & I dies have concave bottom punchs .Quote:
Originally Posted by uscra112
I always assumed the slight dome was correct . I've been seating gas checks with the concave surface for about 50 years now and don't see a problem ... in fact I thought it was "domed" to help the gas checks seat square on the shank .
If it feels better flat , flip the punch over and use the flat end .
Gary
OP question - the 'dome' is due to die pulling the sides of the GC down. Only problem is the GC MUST enter the die correctly. If bullet first, the bullet tends to align the GC better. The dome itself won't decrease accuracy but the is AIR under it. It will get flat on firing.
That only works for me if the check doesn't sort of make a snap when I put it on.Quote:
Originally Posted by Gibbs44
If I pick up a boolit, and the check falls off-- then it'll do OK by putting it in the sizer, then run the boolit down.
Outstanding! This is a great idea! I'm gonna try it tonight, and report my findings. See ya,Quote:
Originally Posted by Yooper003
Scotty
Squarely seated checks are my preference. I confess to manipulating them into "square" position before they go thru die. In my case , everything is through sized so I like to get them on squarely.