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View Full Version : leading and keyholing 9mm TL boolits--cause?



9mm4545
02-12-2010, 08:23 PM
I have been loading some 9mm loads using Lee 124gr. TL boolits, lubed with LLA/JPW mix and unsized. Load is WW231 4.4 gr. and these are seated to the first microband. My problem is while they function fine in the gun (SA XDm 5") before I shoot a hundred rounds the barrel is leading like crazy (mostly toward the muzzle end) and the accuracy goes away. Looking at the target shows some seriously unstable rounds with keyholes and a pattern rather than a group. I have tried seating the bullets out to a OAL of 1.165" but that didn't help. Less powder, different powder, different lube, longer/shorter OAL, other suggestions? Thanks for any input!

versifier
02-12-2010, 11:02 PM
The location of the worst leading explains what is happening, but there are several possible causes of it.

The bullet is stripping in the barrel because its rotational energy exceeded the strength of its alloy and the bullet rode up over the lands, leaving part of its mass beind as lead fouling in the grooves. It was either simply pushed too hard for cast alloy, or more likely it was too small and didn't have enough obturation into the grooves to hold it securely and spin it as pressures built up.

First, I would be looking at your load. At 4.4 gr W231, Lee says it is .4 gr over their max for that powder with a jacketed bullet. However, Sierra feels one can safely go to 5.1 with one of their bullets, which are also jacketed. I would call that load fairly warm for a jacketed bullet, probably too hot for the alloy. I would reduce the charge to a starting load and work it up properly to see when you begin to get leading and then back off a tad.

If that doesn't help, next I might consider that of what specific cast 9mm data is available, neither source - Lyman or Lee - suggests W231 for any loads. Personally, I have had good luck with Unique and Bullseye and never tried 231 in the cartridge.

About the bullets: What alloy was used and what was their as cast diameter mic'd at? I don't think it's the lube, but I have never used that mix, just LLA with 10%mineral spirits. I suspect that even though they are unsized, they are probably too small. TL bullets require a really good grip on the lands and it is critical that they be large enough. When properly sized, they work well in my rifles with LLA, so it's not the TL design itself. Lee dies are not always of sufficient diameter and it is entirely possible you got a small mould. More likely to happen with a 2cav than a 6cav, but it happens. If that's what's wrong, you have to call first, then send the mould to them for replacement at their convenience. I've been through it with them before. They will send you another new one off the shelf and you roll the dice again. A man has to be patient to deal with them, but it can be done successfully. [smilie=1:

If you haven't slugged the bore by this point, you ought to do it. Mic'ing the slug compared to the actual mic'd size of the bullet should tell you everything you need to pin down the cause exactly.

9mm4545
02-13-2010, 01:21 AM
Wow! Thanks for the fast reply and great information. I've got lots of experimenting to do. I think you may well be right that this load is too hot for the alloy used. I did mike the bullets and they come in at .357 very consistently. When I applied the Lee bullet hardness tester however, the hardness was not nearly as hard as I thought it would be. These were mostly WW but of a mixed batch and I suspect there were more stick-on weights in there than previously realized. I'll throw in some linotype next time and harden up the mix a bit. Slugging the barrel is something I have been meaning to get around to; now I have incentive. I ran out of Bullseye and had some 231 on hand. Maybe I should go back--and not so hot! Thanks again.

versifier
02-13-2010, 02:20 AM
You don't need to harden the mix unless you have feeding issues, and you shouldn't with that bullet.

The problem is the size of the bullet.

.357" is too small for proper obturation in most 9mm barrels and a harder alloy would make it worse, not better. You need bullets of .358 or .359". Slugging the bore will tell you what size they need to be (cast bullets need to be .002" over groove diameter). Barrels vary so much dimensionally and you can expect to see a groove diameter anywhere between .354 - .359", but it has little or no effect on jacketed bullets. With cast however, size is critical to accuracy and performance. You should be able to shoot pure lead without leading up your barrel if the bullets are properly sized. When the round was invented, it was loaded with a pure lead conical bullet. I have a mould very similar to those that I used for a P38 and I have shot very hot loads, but the bullets fit that bore properly. At the normal pressures and velocities of a 9mm pistol, you are not going to outstress TL bands or tumble lubes if they are correctly sized, and a softer alloy obturates (fills the grooves) better than a harder one giving you more bearing surface and deeper contact with the barrel's lands. My normal alloy for a nonGC pistol bullet is 1/4WW 3/4pure with a few ounces of tin added to a 20lb melt for better fill out and I shoot thousands of them in pistols and revolvers.

kg42
02-13-2010, 02:54 AM
Few handloaders are aware of how hot the 9mm is naturally... : tiny case, fast powders, high working pressure.... it takes very little to go wild and often shows no signs of overpressure at all.
But many shooters want their guns to kick... (don't 45 and 44 kick eh?!); 9mm4545 is showing more reason than many I have met in the past.

A good example is given by Versifier when comparing data from LEE and Sierra: 4.4 versus 5.1.
I have an article at home to that effect. The author shot several hundred reloads in each of his handguns, before finding out that other sources were more conservative; by then one of the guns was showing signs of wear....

There's not much to gain by pushing such bullets anyways (useless for defense); in such a tiny case you can safely reduce fast powders loads by 20% and get very good target loads.

kg

kg42
02-13-2010, 11:59 AM
I corrected the post above. My starting loads with fast powders are 20% below max.

For example, Hornady gives a starting load of 3.3 gr for Bullseye (max: 4.4) and 3.9 gr for 231 (max:5.2) with a 124 FMJ.
I use 3.3 of Titegroup with the LEE 125 RN, and that's because my Auto-Disk doesn't allow 3.0.

I don't know about JPW and mixing it, but if you follow LEE's instructions too closely with LLA (very little is enough...), you might run out of lube at the end of the barrel.
About keyholing, some TL molds are prone to it as the bullets body is not cut properly and ends up conical (undersized a the front).

runfiverun
02-14-2010, 02:39 AM
the jpw adds some carnuba wax and some paraffin to the lla mix [and is a very good lube].
the one other thing i would look at is your cases.some are thicker than others and can be sizing down your boolits for you.
the lee boolit in 9mm is one of [probably #1] the most asked about combinations on all the sights i visit.
the main question? why do i have leading.
lead at the end of the bbl indicates running out of lube or it fails from pressure then leading starts.
the other issue could easily be a tight spot there.
or your pressure is dropping off enough to let the alloy relax about that spot and it is causing obturation loss.

9mm4545
02-15-2010, 02:46 AM
Is there any advantage to lubing the boolits twice?

kg42
02-15-2010, 04:27 AM
Before I forget... I don't know the JPW so do you think a mix with LLA clings to the bullet as well as pure LLA, or can it be wiped easily; this might matter with the TL grooves.

About double lubing... I think LLA varies a lot after you have used a bottle for a while; the thinner evaporates and gives a thicker goo.
Now, I just found out after 20 years of using it that it can work in revolvers... I made that discovery by applying more (doh!) of the content of an almost empty bottle... not still sure I could get a fresh mix to work in a single layer.

Try pure LLA, single and double layer, and compare the results.

versifier
02-15-2010, 06:51 AM
I don't think that there is any advantage to double lubing, but I don't think it will hurt, either. It really doesn't take much of it to work effectively, even diluted like I use it. I either tumble or dip lube, depending on if I can grip the nose of the bullet or not. I have experimented with thick coats, double coats, regular coats, and very light coats on both handgun and rifle bullets and still never had a lube failure (or any leading when the bullets fit the bore). The most extreme tests i did were with .30cal Lee C309-113F "soupcans" cast of 1/2 lino fired in a .30-30 at just less than 2800fps. No leading at all, but best accuracy with them was at around 2500fps. They had what I would today consider to be a thick coat of LLA. I shoot .30cal 150-190gr GC hunting bullets with one light coat at 1800-2000fps. There is no difference in accuracy when I use heavier coats of LLA on them, but it takes a week or more for them to dry hard to the touch with thicker coats. In extreme tests, the alloy has always failed before the lube.

I prefer the diluted LLA (10% mineral spirits) because it dries hard enough to size overnight and completely within two days and isn't sticky, with no picking up of dust and dirt. One thin coat of it before sizing is really all the bullets need.

I have used just JPW for handgun bullets with good accuracy and no leading in revolvers and pistols, but prefer LLA because it dries hard. I have never mixed them, though I have heard nothing but positive results from those who have.