Gas check leaving bullet at muzzle

[JDNC]

Veral,  I found a 30 cal gas check embedded in my stop skyscreen flush with the surface of the plastic.  Have you experienced anything like this?  I don't know what might have caused it to come off and it may have been a one time fluke.  I think I may put up some cardboard near the screens and see if I can find anymore.  I use Hornady gc's.

JD

[Veral]

  I've definately heard of it, and in fact the worst incident was from a customer report.  He had an old style lyman check frisbe in a semi circle and hit another shooter in the shoulder.  It stung like fire but didn't penetrate.

  The old lymn checks were note worthy for this problem.  Hornady (Lyman & RCBS are Hornady manufacture now.) and Gator checks are all designed to crimp on, and IF THEY CRIMP SOLIDLY they stay on all the way to the target.  The cast bullets which have tapered check shanks, or undersize one, are vulnerable though, as neither supplies enough metal for a good crimp.  I make all LBT molds with straight check shanks, and large enough to insure a sure grip. I've done it this way for 30 years, starting with the first molds I made. If I ship a mold which doesn't give good tight gc grip, I fix them free.  That's how important I consider gc fit.

[ND Sharpshooter]

After a gas check took a gouge out of the start screen of my Chrony, I built a frame that holds a sheet of 1/2 inch plexi-glass in front of the screens.  The sheet extends abut an inch above and to each side of the Chrony.  It's been notched a couple times and is also speckled with bullet lube.  I also had a gc cut one of the wires on an older chronograph that wasn't self contained like Chronys are. 

[Steve P]

I shoot 1000s of cast bullets a year.  I have never personally had a check come off, to my knowledge.  I have mostly Hornady check, and with the exception of my 41 bullet, they all fit snuggly on the shank of the bullet.  For my 41, I have to get a .416 check from Hornady.  They are a little big and loose, until run thru my sizer die. 

Sounds like undersized shanks on the bullet base.  Send mold in to have .001" or .002 taken out of shank area so you have more lead to size and grip the check in place.

Steve

[JDNC]

Nope, not a small shank..I have to carefully place each gc on the shank to prevent shaving because it's such a perfect fit.  I do remember at one time after sizing in a push through Lee sizing die my gc's were loose (same gc and bullet).  Never could figure out why, but if I seated the gc using my RCBS lube sizer then push it through the lee die I didn't have the problem.  I bet during this time I probably lost some gc's..I sure hope so anyway.

[Veral]

   Interesting.  This is the first I've heard of gc's coming off when the shanks are large eough to get a good crimp.  Keep in mind that they get crimped another .008 (average rifling depth) when they go through the rifling and it gives one something to wonder about.

  Gas check hardness varies from lot to lot, and those with high hardenss often are  slightly loose after crimping one, due to springback of the hard metal.  The looseness is very small, but it will be there after bullets leave the muzzle also.  Annealing the checks will soften the metal enough that they stay crimped tight, and since this totally stops the minute rattle, it often tightens accuracy measurably.  Enough to be real important to benchrest shooters.

[JDNC]

Veral, I think the problem may have been when I was sizing through a Lee push through sizer because some of the gc's appeared as if the sizer was pushing the bulle foward and leaving the gc behind in a sense.  I can't explain it other than after the bullet left the sizer the gc was loose and not completely pushed on.  Now.. if I shot some of these before finding this, this was probably when I lost some gc's.

I generally size using using my rcbs lube-sizer and was just testing a diameter that I did not have a die for when using the Lee.  I'm not saying that there is anything wrong with the Lee die but to this day I cant figure why when you push the bullet through it appears to leave the gc.  I mean when it comes out it's not only loose it's not all the way on!  I did crimp some on prior to sizing with the lee with my rcbs zizer and it appeared this corrected the problem. Oh well I'm not using the Lee now anyway.  I've not experienced this since using the rcbs dies.

JD

[Veral]

  Thank you for this information.  Would you please inform us all whether you were pushing the bullets through nose first or gas check first?

  The lee sizer is an excellent money saving way to size bullets for those trying to get started on a tight budget, or not concerned about the fairly slow production speed.  In my experiance with dies I made, which work the same way, pushing bullets through nose first always resulted in tightly clamped, well crimped gas checks, as long as the sizer has a little sizing to do.  Some pressure is needed for the punch to be able to clamp the checks tightly.  The punch must be fairly close to sizer diameter, ideally not more than .010 smaller, to prevent the checks from inverting a little, or being cupped in the base.

[JDNC]

I was pushing from the base (nose first) up through the die.  I can't remember how much I was sizing down, but probably only .002-.003".  I was trying to size in the Lee die then lubing in my rcbs lube-sizer with a larger die.  I can tell you this much..I know the bullets were oven heat treated and were hard (in the 30 bhn range). 

[JDNC]

I know this appears I'm nuts..but I also was confused as what was causing the problem.  I just gave up and went back to the rcbs dies. I wish I had taken some notes but water over the dam!  I guess now maybe the gc was being turned inside out a little in the die(small punch?)..pushing the bullet a few thousandth's foward in the die and as the gc was trailing behind somewhat leaving the gc loose. Beats me. By the way, Veral I received the #8 mould 311-150-LFN gc/pb, thanks.

[jhalcott]

  I had this happen with a Lyman .22 caliber bullet. The check wold drag a bit on entering the sizer die and the pusher pin would indent the base a tiny amount. I used those bullets for fire forming. As it is a flat nosed design, I just flipped them over and ran them thru base up.

[JDNC]

Thanks jhalcott,  I thought maybe I was losing my mind