I'm new to shooting cast bullets. I bought some 405 grn RNFP bullets for my .45/70 & noticed that not all the grooves around the bullet were completely filled with sizing wax. What exactly is the purpose of sizing wax ? And does it matter if not all the grooves are filled completely all the way around ? Will it affect my accuracy ? :confused:

What you see is bullet lubricant. Its purpose is to lubricate the bullet and help its passage through the bore, prevent leading, and hopefully keep black powder fouling soft so it can be easily removed (if you're shooting Holy Black).
I'm not sure how important minor gaps in the lube make... I try to fill all the grooves except the crimping groove. This is usually the top groove on bullets that have crimping grooves. Some only have a lube grrove.
My revolver bullets typically have one or two grooves. Your rifle bullet may have more.
There are different lubes for different purposes. For Black Powder or relatively low velocity revolver, I use my home made lube tah is a dead ringer for the BP SPG. It works great to 850-900 FPS, which is as high as I've tried it.
Other lubes might be very hard, and soften at higher temperatures.
Hope this helps you,

Happy Shootin'! -Tom

IMO, while I like to see the lube grooves full, small gaps in the lube grooves will not hamper the accuracy of the bullet. The weight of the lube compared to the weight of the bullet is an extremely small percentage of the total weight.

As the others said, bullet lube is what's on your bullets.

Sizing wax is a lube that's applied to brass cases before resizing them for reloading. It allows the brass to slide in/out of the case sizing die without sticking. It's applied in a very thin film that's just enuf to lube the die.

Bullet lube is applied in grooves so there's enuf to last the entire length of the barrel.
If there's more than 1 groove, the groove farthest to the front is usually shallower, and shaped to allow the case mouth to be crimped into it. It generally should not have lube in it.

Commercial bullet casters usually use a hard lube that doesn't stick to adjacent bullets and get smeared off in shipping. But, it can crack and fall off. I've found I can pick up the bits of loose lube, and press them back into the grooves while reloading, assuming it's just a few out of the whole box.

I don't worry about it as long as > about ¾ of the lube grooves' circumference is filled. Each shot will leave a little lube behind, and it's unlikely that the same spot of the barrel will go unlubed for enuf shots in a row to rub off all the prior lube. More likely, the next bullet's unlubed section will not align with the prior bullet's unlubed section. So, the lubed sections all even out in the barrel.

.

I did a little more research after my initial post, & realised my error in regards to sizing wax versus bullet lube. My ignorance. Thanks to everyone with there replies. Great info. Exactly what the Doctor ordered.

The bullets I bought, are, as everyone has replied, only missing minor gaps in lube. I have used bullets from this caster before in my .45 ACP handgun, & they worked very well. I'm hoping that the same will be ture for these rifle bullets. I really wanted a bullet with a little larger meplate & gas checked but in Canada we have great difficulty getting variety in specialty reloading components & sometimes have to live with what we can find. I plan or stoking up some trial rounds this weekend, & seeing how accurate they are. My goal is to come up with one round I can hunt & target shoot with for my .45/70 Guide Gun, but until I make a trip to the U.S. I think I'm going to have to live with what I have. There are lots of excellent bullets out there, just not here !!!

Thanks again to everyone for the education in your replies !!:)

A lot of stuff is hard to come by here South of the border nowadays as well...
You might want to consider casting your own bullets. Once you have the mold and master casting, you won't have to worry about bullets again.

Happy Shootin'! -Tom

That, and, you can apply your own gas checks when you need them. If your guide gun has muzzle brake vents, you probably do.

I never thought of trying to apply my own gas checks. What exactly would that entail ?? Oh & my Guide Gun isn't ported, straight 18 1/2" barrel no ports.:)

You can tumble lube bullets, meaning you use a liquid lube, dribble it on the bullets, and roll them around in a pan to get them coated. The solvent dries out of the lube, leaving a thin coating of lube on them. Personally, I don't like this method.

You can get a lubricator-sizer from Lyman, RCBS, or Saeco. This is a kind of press that squeezes bullets thru a sizing die, and applies the lube like you're used to into the lube grooves.

If your bullets are a little smaller diameter at the heel, you buy gas checks and press them over the back of bullet. Then, the lubricator squeezes the sides of the check down on the bullet while you size & lube them, locking the checks in place.

You can buy gas checks by the 1000's at places like Midway, Midsouth, etc., that sell reloading components.

If you want to use gas checks, you buy a bullet mould that moulds the check groove into the heel of the bullet.

:)

It should be noted that the smaller heel Gmd3006 mentioned has to be intentionally included in the mold for the purpose accommodating a gas check. It can't be done to just any cast bullet. The mold will usually have the letters GC as part of the part number or description.

I don't know whose bullets you are buying, or in what weight, but you might want to try Bullet Barn in B.C. They make a variety of .45-70 bullets and you might see one that you like. The ones that I tried gave me good accuracy.
If you are loading for a Guide Gun, I don't believe you will see any problems with some of the lube missing (perhaps in a 1000 yard rifle).