Is lubing gas checked bullets necessary?

[Heckler]

It's my understanding that the purpose of bullet lube is to help prevent or minimize leading. Given that gas checks are extremely effective at prevent leading (at least in my experience), I wonder if lubing checked bullets is necessary at all. Is it a redundant step?

Have any of you experimented with this?

[Maven]

"...I wonder if lubing checked bullets is necessary at all. Is it a redundant step? Have any of you experimented with this?"

Heckler, Gas checks apparently strength the CB's base, which allows them to resist rotational forces imparted by [the] rifling and a given amount of pressure. They aren't necessary at ~1,600 fps or less in rifles. I don't think they scrape away leading created by previous shots. If that were the case, why would leading appear in the first place? When I get bore leading in my rifles when using gas checked CB's, I immediately suspect velocity/powder charge, alloy strength, and/or the amount of lubrication each CB carries. Generally, using more lube and adjusting the powder charge is all I need to do to prevent it.

Have I experimented with this? Yes, but not intentionally. To wit, using WW's + 1% Sn and Felix Lube, I used a .30cal. gas checked, bore riding CB, Saeco RG-4, over 34 grs. IMR 4895 in my .30-06 (a load recommended by E.H. Harrison, btw). Bore leading was horrendous, recoil was stout, and accuracy not worthy of note. However, using the same alloy and bullet and a lesser charge of a different powder, WC 820, gave pinpoint accuracy and no leading whatsoever. Example 2 involved the Lee 195 gr. bore riding, gas checked CB for the 8 x 57mm Mau. Using WW + 1% Sn and WC 820 (the same charge as in the '06), I got bore leading. When I wiped Lee Liquid Alox on the noses and repeated the test, there was no bore leading at all. Accuracy was impressive with the unleaded bore.

You can duplicate this yourself, but use 25 CB's with GC's only v. 25 with CB's, GC's and lube, and compare the results for accuracy and bore leading using a load that -> at least 1,700 - 1,800 fps in your rifle. Lastly, Ken Mollohan (Molly on this site), a founding member of the CBA, successfully used Cream of Wheat (COW) with unlubed, gas checked (?) CB's to get no bore leading and acceptable accuracy. You may want to search the CBA archives for "COW Loads."

[Heckler]

Thanks, Maven. Those are some good things to consider.

I wonder what the powder type could have to do with leading. Certainly velocity is a critical factor; however, it seems that two powders producing identical velocities would produce the same degree of leading. I've always followed the belief that the barrel of the gun was mostly to blame for a gun's propensity to lead, as some guns lead like crazy with a particular load, while others show no signs of leading at all with the same load.

I plan on doing some experiments with this. I'm mostly a handgun shooter myself, and I have never had to give much thought to leading with checks since I have never seen leading occur in my barrels except with plain-base bullets.

I'll have to see if my particular loads allow me to forego the lubing step. I use the Lee push-through sizer sets, so lubing is a fairly messy process for me.

[Shiloh]

I don't think I would want to try it without lube. Worked for successfully for Maven though.

Shiloh

[Maven]

Shiloh, I never tried to shoot unlubed CB's, but Ken Mollohan did with Cream of Wheat filler. He got no leading, higher pressure, and just OK accuracy though.

Heckler, You're correct about barrel (bore) quality being a variable which contributes to leading. Thanks for reminding me!

[Heckler]

Before we theorize much more, I'm going to get out and do the experiment. It might be a couple of days, but I'll do some fresh casting and sizing without lube and see what results I get out of three different pistols in the same caliber that I know lead with plain base bullets and don't lead with lubed gas checked bullets.

[old turtle]

My understanding of gas checks is to prevent flame cutting of the base of the bullet and or deformation of the base. I do not know, but Sharps "Complete Guide to Handloading" has a very scary description of the results of shooting unlubed cast boolits. Not a pretty sight. He contends that without lube the boolits leave whats amonts a soldering of the bore because of the tin and lead in conjuction with bright steel. This can be very difficult to clean out. It will make an interesting experment.

[Freightman]

Might be but I think I will leave that up to the more brave of heart.

[onondaga]

Heckler:

Many believe velocity is a critical factor in leading. It is not. Pressure, alloy hardness and bullet fit determine leading. Lube is important in any case. Powder selection has a factor in leading because it effects pressure regardless of velocity. A loose bullet without enough pressure behind it to punch it and expand it and seal gasses will lead the bore excessively at any velocity. Brinell hardness translates into specific PSI deformation strength of the alloy. A load pressure about 5 - 10 percent below the alloy strength in PSI is where the accuracy sweet spot for cast bullets lies and also the spot where the deformation of the bullet seals the pressure behind the bullet effectively and eliminates gas cutting that is the major cause of leading a barrel.

Under size bullets can be punched hard enough to make them seal with the right pressure behind them but a better result comes from a good fit. bullets .001 to .002 larger than the bore is a good starting place when your load is in the pressure sweet spot for the alloy using plain based lead alloy bullets . Gas checked bullets will extend the sweet spot and allow higher pressure, higher velocity loads approaching jacketed bullet velocity performance. Selecting a powder that has the lowest pressure for the velocities you desire is an important choice for cast bullet load development if you are concerned about greater velocities and accuracy.

This is an interesting subject to read up on and I recommend the Lee Second Edition reloading manual that covers this subject very well. If you also get the Lee Hardness tester it will fill in the data blanks for the method and get you in the sweet spot for your cast bullet loads and eliminate a very big pile of trial and error.

[leadloader]

ive been told that leading in handguns isnt because of the alloy being to soft but to hard for the psi not allowing the bullet to seal the bore nicely..the lube works more as a lubricant ... heres a mind bender would no lube increase the surface resistance and cause heat to build up from friction?

[dicko]

Heckler:

Many believe velocity is a critical factor in leading. It is not. Pressure, alloy hardness and bullet fit determine leading. Lube is important in any case.

There are six factors in leading: alloy hardness, bullet fit, lube quality, bore smoothness, velocity, and whether or not the bullet is gas checked.

But some of these should not be a factor because they should be a given. The obvious one is bullet fit. Where does the notion come from that bullets obturate to seal the bore ? Cast bullets should be sized to fit groove or bigger. Generally one to three thou bigger works better than exact groove dia though not always. Bullets are therefore squeezed down in the bore, they do not obturate, so the notion that they need pressure to obturate is false.

Lube is probably the least important as any decent lube will do the job. I have had 2400FPS from a 308 Win with 50/50 Alox/beeswax with no leading.

Most bores are smooth enough not to be an issue these days, but I encountered a revolver (won't say what make) that leaded up so badly with my bullets that it had to be cleaned with mercury. The same bullets had never been a problem in dozens of other guns.

Relatively soft bullets, like WW, can sometimes be fired at quite high velocities without significant leading. But the general rule, and a correct one, is that the harder the alloy, the higher the velocity. Anyone who wants to argue is invited to try pure lead at 2400FPS. I have found that 6% antimony leads very little at 1600FPS with plain base bullets, but at 8% leading is barely detectable after 100 rounds. 1600FPS has long been the accepted max for plain base. I found that to be true, as leading became seriously heavy at 1800FPS with all alloys including 4/12 linotype. That proves beyond all doubt that velocity is a major factor.

The effect of gas checks is simple and equally beyond doubt. Rule of thumb max is 2400FPS. I have chronographed 2500 with no leading. Gas checks also increase max MV with softer alloys. 6% Antimony leads like hell at 2000FPS plain base but not at all with gas check. Softer alloys can deform (compress) slightly at high pressures, kissing goodbye to decent accuracy. That's another reason to use hard enough alloy at high MV.

The notion that velocity is not a critical factor in leading is therefore false, and against a century's worth of accumulated experience. As a commercial caster I have tested this extensively, so it is not armchair theory.

[felix]

Obturation is a requirement. Otherwise, how would you put an expanded projectile into a case, a case into chamber, and finally eject it without any pressure blowback/washout? ... felix

[Bullshop]

" Where does the notion come from that bullets obturate to seal the bore ? "

example #1
Muzzle loader shooting bore diameter (not groove) conicals.
example #2
BPCR shooting PP patched to bore diameter(not groove) with either BP or smokeless.

Since you asked here are two good examples that come to mind. If you would like more that wont be hard.

[onondaga]

The notion you disagree with comes from the research of Richard Lee.

You disagree with Richard Lee second edition very clearly about pressure, alloy strength and obturation having a predictable relationship. I have repeated his experiments and re-proven his theory on the pressure sweet spot and accuracy for every caliber I load with lead boolits. So, I continue to disagree with you respectfully. I am convinced by my results that I could use your guns and boolits and get them to shoot more accurately with the Lee method, and I don't believe you could reciprocate with my stuff. Of course, I am a stubborn blockhead and have been casting boolits and shooting them since 1957 with a lot of wasted trial and error until Lee gave me a prescribed method that has performed 100% since I began following Lee.
You are correct for some of what you say about obturation, but it goes beyond that. Boolits can be in a gray zone of diameter, hardness and load pressure, where a bullet at nominal bore fit can have gas blow-by if the alloy is not strong enough . It appears, you believe, that from that point, higher pressure will not push the back of the bullet toward the front and cause diameter change of the bullet to seal gas. You are disagreeing with proven physical theory. I believed Lee's theory was logical and reasonable, but I tested it. Perhaps you might consider testing Lee's well documented theory. Accurate hardness testing of the alloy with an assumed good bullet fit is where Lee starts but I slug bores and measure boolits to check the assumption of fit. Then continue with the Lee method to the sweet spot of accuracy with 2 or more alloys and select powder based on pressure matching powder load to alloy strength and play them out to get the best accuracy I can for my rifles. Plain based lead alloy bullets follow Lee's theory right on for me. I have found that gas checked bullets can have multiple sweet spots of accuracy beyond the alloy strength/load pressure matching sweet spot of the Lee theory. That I do not understand and cannot predict, But, I take advantage of it for higher velocity.

Leading has never been an issue in any of my rifles, my slickly polished bores combined with never shooting jacketed ammo likely helps that along with the other stuff you mention.

[357shooter]

onondaga: Was your testing rifles only or did you also test pistols? My testing has been with pistols only and did not jive with the Lee theory of matching alloy and pressure to achieve accuracy. If this is a rifle only discussion, sorry for the rabbit hole. If my test results are in error for some reason I'd like to know.

Thanks

[onondaga]

My testing has been with rifles only.

[357shooter]

My testing has been with rifles only.
Thanks.

[Ridgerunner665]

Diggin up an old thread, but I have a question along these lines...sorta.

My boolits are Ranch Dog 350's (gas checked) in a Marlin 45-70 (22" barrel)...I shot a few at a time (5-10) for a while and didn't notice any problems but the other day I shot 50 and after about 15 rounds my accuracy went from one ragged hole at 50 yards to 6" groups...

The bullets are cast from Rotometals Hardball alloy (2% tin - 6% antimony - 92% lead), water quenched, 30 BHN...they are .460" diameter (the gun slugs .457").

The load is a warm one (2,050 fps) with 52 grains of H322.

After that session I noticed some mild leading, but nothing major...I suspect not enough lube (Alox) but I don't know for sure.

Any idea how accuracy can go from great to terrible that fast?

[7of7]

Interesting thought, since Onondaga's experience with rifles differs from results with pistols.
Let me throw out a thought..
With a revolver, the bullet accelerates as it departs from the cylinder under gas pressure, then it hits a restriction, the forcing cone and rifling in the bore.
Something has to move as the front of the boolit meets resistance, so the base, would squash a bit, or obturate, as a result of the change in resistance at the front end of the boolit.
Rifles, don't have that same distance to travel, so the effect is not as extreme as it would be with a revolver.
Does that make sense? (just thinking outloud... ok, in type)

[lastborn]

bump---cause I want to learn more !

[Pirate69]

Me too!! This is good stuff.