Any ideas as to what is causing this?

[Ole]

Regarding some of my 7.62x39 cast loads. I'm using the 2R155 Lee bullet and 15 grains of 2400. Bullet is run through a 314" sizer to install the gas check.

http://i258.photobucket.com/albums/hh280/Ole1830/IMG_5949_zps90dce141.jpg (http://s258.photobucket.com/user/Ole1830/media/IMG_5949_zps90dce141.jpg.html)

I pulled one of the bullets that dropped inside the case and the bullet came out but the gas check stayed in the neck.

http://i258.photobucket.com/albums/hh280/Ole1830/IMG_5950_zps5da05c5b.jpg (http://s258.photobucket.com/user/Ole1830/media/IMG_5950_zps5da05c5b.jpg.html)

They measure .313" after pulling them.

Gas check inside the neck:

http://i258.photobucket.com/albums/hh280/Ole1830/IMG_5951_zpsc51837b3.jpg (http://s258.photobucket.com/user/Ole1830/media/IMG_5951_zpsc51837b3.jpg.html)

Load is 15 grains of 2400. I have several boxes of H4198 loads and this does not happen. Assuming it's because the case contains more powder.

So how do I fix this?

[Sgtonory]

To little neck tention caused by undersized boolits or to big of expander.

[Ole]

To little neck tention caused by undersized boolits or to big of expander.

I don't have this issue with .311" jacketed bullets with the same die setup.

[JSnover]

It just fell in all by itself? The neck was expanded too much and/or you didn't crimp. Like Sgt Ornery said: neck tension.

[Ole]

It just fell in all by itself? The neck was expanded too much and/or you didn't crimp. Like Sgt Ornery said: neck tension.

It just fell in by itself.

It's almost as if the gas check is expanding the necks when I seat the bullets.

I don't have this issue when using .311" jacketed bullets.

[Ole]

Was the case run through the sizer before loading?

Yes I resized the brass cases.

[JSnover]

Could be. What is the check diameter before and after sizing?

[JSnover]

I dunno. The only time it has ever happened to me was when I was experimenting with zero neck tension; just thumb-seated the boolits a little bit long so they would have positive contact with the rifling.

[Ole]

It looks like the gas check measures .315", but the bullet measures .314".

Picture of virgin bullet from that same batch that was never seated:

http://i258.photobucket.com/albums/hh280/Ole1830/IMG_5953_zps26dae348.jpg (http://s258.photobucket.com/user/Ole1830/media/IMG_5953_zps26dae348.jpg.html)

http://i258.photobucket.com/albums/hh280/Ole1830/IMG_5958_zps3fc77f3e.jpg (http://s258.photobucket.com/user/Ole1830/media/IMG_5958_zps3fc77f3e.jpg.html)

[mikeym1a]

Not a solution to your 'problem', but, after seating, you might try a collet sizing die with the primer pin removed. That should hold the boolit . Maybe....

[HeavyMetal]

So here's what I think, and I do own that mold by the way, gas check is bigger than boolit and harder to boot.

As you seat the boolit the case neck is expanded by the check itself resulting in no case neck tension on the lead part of your boolit.

To check this load a few with no check and see if this repeats itself, I don't think it will. By they way thats why your check is still "locked" in the case: it fits!

Next are you loading mixed cases' or sorting by headstamp? Mixed case's can suffer from different case thickness, brass hardness and pretty much anything else that can throw a monkey wrench into a nice looking load.

Then next question is are you sizing the boolits with checks on them or adding checks later? Should not be that much spring back on a check to chage .002 of an inch but it depends on the check alloy.

Whatever the issue: the bottom line is every projectile you load in a case must be the same diameter from base to start of radius other wise you mess with neck size and boolit tension at the neck resulting in the exact problem you got.

It doesn't happen with jacketed because they will be the same diameter from base to start of radius...hopefully, LOL!

Loading the 7.62x39 can be a bit of a challange and a die set can make or break your efforts: what dies set are you using?

[Ole]

what dies set are you using?

RCBS with the .311 expander ball.

Thank you for the suggestions I will try them. I think the gas checks are the biggest part of the bullet which is causing my problem.

[HeavyMetal]

If your not using range pick up brass, meaning your loading what you shoot in your gun, go buy the Lee Colet die st for the 7.62x39.

It has both a full length sizer die and a collet type neck sizing die which size to a steel "mandrel" of specific diameter. In the 7.62x39 die set you actually get two seperate mandrels, .309 and .312 if I remember right, so you can switch as bullets, .308 and .311 become available.

Add in the collet crimp die and this issue will go away! but you still need to address the issue with the checks being bigger than the boolit you loading.

Never did see the answer to my first question: are you sizing these with the check on or adding it later after sizing?

[Ole]

If your not using range pick up brass, meaning your loading what you shoot in your gun, go buy the Lee Colet die st for the 7.62x39.

It has both a full length sizer die and a collet type neck sizing die which size to a steel "mandrel" of specific diameter. In the 7.62x39 die set you actually get two seperate mandrels, .309 and .312 if I remember right, so you can switch as bullets, .308 and .311 become available.

Add in the collet crimp die and this issue will go away! but you still need to address the issue with the checks being bigger than the boolit you loading.

Never did see the answer to my first question: are you sizing these with the check on or adding it later after sizing?

I'm using the Lee push through 314" sizer to seat my gas checks. I don't think the bullets are ever sized because they are normally smaller than 314" as cast from my mold.

[HeavyMetal]

I do believe we've found your problem!

Just to make sure I get it: check added to .313/.314 diameter boolit and then run through a Lee push through .314 sizer die.

If this is a correct statement it is time to "slug" your sizing die!

A slight "beagling" of your 2R155 mold should yeild you several nice .315 or larger boolits run these through your Lee push through with no check on them and then Mic'm for Diameter.

You'll get one of three reading:
.313

.314

.315

Because the checks are coming out .315 on a lubed and sized boolit my money is on the last horse!

If this is the case you now need to make a decision on how you wish to cast in the future:

Do you need a .313 a .314 or .315 diameter boolit? once you decide you'll need Lee to fix your mold or you sizer as needed pending your decision.

Bottomline is what you have isn't going to work until you make some diamensional changes in your equipment.

Sorry about, that I hate giving bad news but the up side is this is easily fixed.

[blackthorn]

One other thing you may want to try is anealing your gas checks, put them in place and then run the checked bullet through the sizer. Just a thought.

[grouch]

I think it's simpler than all that. It looks to me like you're sizing a .312 bullet .314 leaving a +/- .314 gas check on a smaller bullet. The first thing I'd try would be sizing to .311. Maybe the gas check step is a little loose. As a matter of interest, I've had that problem with several molds over the years. Some good advise given above by other posters.
Grouch

[leadman]

I agree that you need to size the boolit and gc to the same size. If the boolit is smaller than what you are sizing the gc to then when the gc is seated at the base of the neck or below the boolit can fall in the case.
A gc will usually have about .0005" to .001" springback after going thru a sizer. Annealing can change this by making the checks softer.

[runfiverun]

post 11 on down holds the answer.
measuring like you did really starts to tell the story you just need to follow through on what you have seen so far.

the other thing that can cause issues like this is the neck anneal, if the case has lost it's softness it will hold itself open even after being sized.

[leftiye]

Anneal the gas checks so they size properly. Boolit that fell into case was .313, had probly been sized by case tension. Had fer shore bin sized by sumpthin'. Gas check was below neck, and neck had been sized (opened up) by check. What was gas check size of boolit pulled? Oops it stayed in the neck (while boolit fell out). That gas check was probly .315 also. How that boolit got to be .313 is a/the real good question.

[Wayne Smith]

One thing we don't know is what size boolit your rifle needs. You know you need the boolit to be the same size it's bearing length. If you have a .314 sizer because your rifle needs that size you need a bigger boolit. If your bore can shoot a .312 boolit you may be good to go, just run the boolits through that sizer.

[GabbyM]

I can do that neck expansion with gas check trick in a 30-30. Have a bullet that likes to drop .3095" some days and I like to size .3100". That little half thousandth is all it takes. Thin wall of a 30-30 case expands easily. Bullets will actually wobble in necks to where you can feel it. Only answer to that is to size .3090". Bore on both our 30-30's is .308" so it's just fine.

On your 7.62x39mm I'd expect your gas check was seating below the case neck so nothing was left tight. Solution is to lap out the bullet mold or use a smaller size die.