front barrel leading

[chriske]

Up to now, any leading I encountered from firing reloads in revolvers occured in the forcing cone and the first inch or so of rifling grooves closest to it

Last week I tried some new .45 Colt reloads in my Ruger Blackhawk :
200 Gr cast LSWC (sized .452) & 8.5 Gr VihtaVuori N 320.
All seemed well : report, recoil, fired case extraction, fired primer appearance OK, nice accuracy.
Although accuracy deteriorated after 24-30 rounds or so, I didn't think anything of it, as I blamed fatigue (I had already been shooting for more than an hour before that)
When cleaning the Ruger; I noticed something I never saw beforfe : in the LAST two inches of the bore, nearest the muzzle, the rifling LANDS were covered with thick leading.
(No doubt this affected accuracy after 4 or 5 cylinderfuls.)

But here's my question :

I seem to recall reading somewhere that this particular phenomenon (leading nearest the muzzle) indicates a specific problem with handloads, but I can't find what it was, exactly (neither in my memory nor in my library):
Bullet too hard ? too soft ? undersized ? Load too hot ? Powder too fast ?
Anyone here knows ?

 

[Walkalong]

Running out of lube/wrong lube, or perhaps slightly exceeding the velocity limit of the bullet. It is obturating and sealing the chamber/slash bore fine, as indicated by no leading at the forcing cone and the first part of the barrel.

 

[GP100man]

i`ll agree with Walkalong , what kind of loobe is being used on the boolit????
it sounds like my exp. with liquid mule snot!!!

GP100man

 

[chriske]

As I didn't cast those bullets myself, I have no idea about the lube.
It's translucent blue, slightly sticky, wax-like, not really soft.

If, like you say, the lube "fails", am I driving those bullets too fast ?

Using cast bullets is a hit-&-miss thing over here : If & When they can be found, it's often impossible to know anything about them except size & weight. Things like alloy composition, BHN hardness or lube remain a mystery.

 

[rcmodel]

Vihtavouri website data 8.7 is suggested load @ 1,070 FPS.
Guessing, your 8.5 might be giving you around 1,000 FPS.

http://www.vihtavuori-lapua.com/pdfs/Handgun-Reloading-Data-2006.pdf

I would imagine your bullets are pretty soft, and as Walkalong noted, slugging up for a good tight bore fit, until running out of lube before running out of barrel. It's possible the soft base band is collapsing in on the rear grease groove and squeezing all the lube out.
A premature ejection so to speak!

These are probably intended to be used in light Cowboy Action loads at 850 FPS or so, and might do well with a reduction in velocity.

However, you are already below the recommended load for N-320, so a change to a slightly faster powder might be in order to get the velocity down in the 900 FPS range.

I don't know what you have available to you, so I guess I would drop the N-320 charge some more (8.3? - 8.0?) and see if you can get a clean burn with no leading.

That should cure the leading problem related to soft bullets & too high velocity.

rc

 

[243winxb]

Obturation is Not Wanted Or Needed

Lee wants the pressure below where Obturation would happen. http://www.realguns.com/archives/118.htm Compare the pressure listed here for Obturation to take place. http://en.wikipedia.org/wiki/Obturate If a cast lead alloy bullet Obturates, it will deform and break down, leading the barrel. The structure of the bullet will be changed when jumping for the cylinder to the forcing come. Not so much change will take place in a auto fixed chamber firearm. Bullet's BHN x 1422 = Pounds per square inch.

According to the chart, a very popular #2 alloy carries a 16 BHN, has a strength indictor of 22,703 PSI and should be limited to 20,000 PSI as maximum pressure. Wheel weight alloy with a BHN of 9 carries a strength of 12,748 PSI and a MAX pressure rating of 11,473 PSI.

 

[243winxb]

It's possible the soft base band is collapsing in on the rear grease groove and squeezing all the lube out

When the bullet is pushed by to much pressure Obturation happens. The base of the bullet is deformed/distorted .

 

[Walkalong]

Obturation is Not Wanted Or Needed

Pretty much everyone who shoots cast bullets would disagree I believe. It has to bump up (obturate) to seal chambers/bores or severe leading from gas cutting is the result. Of course, like anything else, too much is not a good thing either.

The lube is not being "sqeezed out". It just is not up to the task or the velocity limit of the alloy is being exceeded.

 

[Bula]

This is exactly the problem I'd have with most commercially cast stuff. My money goes to the lube being too hard, and maybe even the alloy too hard as well. I hate the stuff myself, but try that "liquid mule snot" as mentioned above and tumble lube them in some Lee liquid alox (with lube ring in place) and see if that helps. That would be the cheapest way to get your money's worth out of the rest of your cast bullets. Good luck and please share your results.

Just curious, what's your barrel length?

 

[ReloaderFred]

As noted, obturation is the desired result when the powder gases hit the base of the bullet. Without it, you get severe leading. It's addressed in every cast bullet manual I've ever read, and that's a lot of them.

It's the lube causing the problem.

Hope this helps.

Fred

 

[dwhite]

I put Lee Liquid Alox (Mule Snot ) on all the commercial cast bullets I use. It's cheap, easy to use, and while it may not really help all of them, it certainly doesn't hurt either.

I had some real soft 40 cal bullets that basically turned my weapon into a smooth bore after 10 rounds. The LLA fixed this easily. After that event, they all get it.

All the Best,
D. White