9mm skidding.....Harder lead?

[flybyjohn]

Something I came up with that works for lower velocity bullets. Wouldnt try it on high vel rounds though. I have a 6" pvc pipe that is stuffed full of plastic Walmart bags. I bag a bunch of bags in one bag and then load all the full bags into the pipe. Most bullets make it 3' but some a little more. After the shot, I start pulling bags out of the end. Each bag will tell you if the bullet made it through by leaving a pulled out tit on each bag. The one that doesn't have a hole is the bag it is in. The bullet is almost perfect being caught this way.

[Forrest r]

Never had any issues with small/thin lands in bbl's. I have a couple of custom 1 in 10 twist bbl's that have extremely small, thin lands for 357's (4" & 6"). They easily handle anything from mild to wild.

Some recovered bullets shot from different firearms/calibers with loads from mild to full house mag & 9mm loads. This is with pc'd bullets.
[IMG][/IMG]

I've recovered 100's of bullets and they always have something to say. What that picture above showed me is the difference between air cooled range scrap (+/- 9bhn) vs water dropped (+/- 13bhn). Some bullets shattered while others had excellent expansion/retention with hp's. The non hp bullets noses either compress/deform or stay unaltered. It's always the same theme again and again.

Playing around with a 308w testing alloys for hunting. Was looking for an alloy that would have the bullet deform & stay intact. As I changed alloys I increased to pressures/velocities, a bullet shattering is no good.
[IMG][/IMG]

When I got to the 2300fps bullet I found a alloy worth testing with several different bullet designs. That 2300fps bullet is a lee 230gr bullet that had a 50,000+psi load pushing it. That softer 230gr bullet also showed signs of the coating becoming easier to scrape off.

What all those bullets pictured above have in common is compression & more importantly compression where it counts, in the lube grooves. Lube grooves are designed to compress and push the lube outward and forward. While coated bullets don't need lube their bases still compress. With coated bullets you want to match the alloy with the bullet's diameter to allow the bullet to expand/compress/seal the bbl.

Will a bullet 3/1000th's over the bbl diameter seal a bbl??? Absolutely!!! The issue becomes how will that oversized bullet react to any imperfections, rotational torque, pressures at different points of the bullets body, etc.

Several years ago I had an excellent conversation with a member on this website. We discussed lube grooves (square vs round) and he was kind enough to send me this photo. If you look closely you can see the lube grooves are compressed on the recovered bullets compared to the as cast bullets pictured above them.
[IMG][/IMG]

You need to compare the lube groove of your recovered bullets to the un-fired cast/coated bullets. No compression ='s no worky. Something else to keep in mind when choosing loads for a bullet. A bullet that has a long/large area of it's body like a wc has a lot more resistance/bbl contact then your bullet. More contact ='s less pressure needed for obturation bullet/bbl fit. The bullet you're using has 1/2 of the bullets body at best in contact with the bbl. Less contact ='s soft alloy + high pressure.

When you get your new bbl back I'd bump your load up to get in the +/- 25,000psi range. I use a bullets in the +/- 9bhn range for 3 different 9mm's. The green bullet in the picture is a lot like the bullet you're using body/design wise. Both bullets are loaded for the same 9mm.
[IMG][/IMG]

Not a hand picked/cherry picked target by any means. It's nothing more than a test target used to test those 9bhn/125gr greeen bullets pictured above using a 25,000+psi load. That load/powder is also a powder a fast burning that has a high quick start pressure that's excellent for getting the bullet to seal the bbl in a hurry. You can have 25,000psi loads with wst and AA#7. The wst smacks the bullet while the AA#7 pushes the bullet. The wst will seal quicker/faster.
[IMG][/IMG]

Anyway, you have a lot going on with your firearm and reloads. When you get your bbl back I'd go back to a softer alloy and bump the load up.

[dubber123]

I wasn't going to respond as I don't have a ton of 9mm cast experience. Forrest certainly seems to, but what I have found in my testing hasn't indicated any particular need for an overly hard boolit, and I'm not powder coating. My normal alloy is air cooled WW's, about 14 Bhn per an LBT tester. I did shoot a few groups with boolits made from shotgun shot pilfered from cheap trap loads to prove a point. Now the common thought is that shot is hard, well not the cheap stuff.. My regular 9mm boolit is a 150 grain RF, but out of shot, they weighed 155. 5 grains is a lot to gain, and that tells me there was a LOT more pure lead in that cheap trap load shot. I never tested them, but I'm betting SOFT.

I'm not as good a shot as Forrest, but the gun, an inexpensive Zastava M-88A with a 3.7" barrel shot under 1.5" at 20 yards using the car roof for a rest, and I did it several times. The load used produced well over 900 fps, which is not low pressure using the fast powder I was loading. This matches Forrests findings of bumping up a boolit to seal the bore. I'm not generally a fan of super soft boolits, but it worked in this instance, the bore was clean, and accuracy was as good as my regular load. If you have boolits skidding, my first thought would be undersized boolits, I hope you get it figured out.

[Lloyd Smale]

have to agree with larry. As a matter of fact ive had linotype buys that only tested 18bhn. 5050 ww/lino usually goes 16-18bhn and that's with good lyno. Never had a batch of ww test any harder then 12bhn. Most of it tests closer to 10. How are you testing it? Ive got both a cabin tree tester and a saeco. Now if your water dropping your ww you should be about right on the number at 18. If your bullet is testing 18 (water dropped as you said) its hard enough for about any handgun application and is hard enough where I doubt that's your problem at 9mm velocitys. One thing to watch in loading 9mm is to make sure you start the bullet in the case straight. With small bullets in my club fingers I have to allways keep that in mind because the 9 is about the worse offender when it comes to having bullets seat crooked. The way they enter the rifling a little off center can make marks that look just like stripping. Actually I too don't see enough evidence of stripping to think that is causing you any trouble. Keep in mind too that its a ruger not a les baer and the rifling might be cut with one land a tad wider then another. Again it shouldn't cause any real problem at handgun range. What are you calling bad leading. Is it actually building up more and more as you shoot to the point it effects accuracy. Or is it just a lead wash that gets no worse. About any gun shooting lead will have a light wash in it and I don't even concern myself with removing it. How many rounds before it effects accuracy. My guideline is if I can shoot the amount of bullets I usually shoot in two range sessions without groups opening up again I don't worry about it. If it is you can still use your alloy as long as your getting accuracy. Just buy a box of jacked bullets and load them up and shoot one about every 50 rounds and it usually will push any lead build up out. Same can be done with a gas checked bullet or even a very hard plain based bullet. Also being a ruger id consider right from the git go shooting maybe a 100 jacketed bullets through it, clean it thoroughly and then shoot cast. That usually smooths up the barrel a bit and make a slightly rough barrel a little more cast friendly.

I've never found any COWWs that measured 18 BHN either unless they were WQ'd(?).

Also can you explain to me what you perceive as "skidding" on either bullet?

Also, your alloy of straight COWW has little tin if any in it. What you see as "leading" may be antimonal wash. Mixing 2% tin with the COWWs will fix that and give you a better alloy.

[ioon44]

The COWW I have used has always run 10 to 12 BHN , and work grate in .45 APC with the Hi-Tek coating. For 9 mm and .40 S&W I have better results with 6-2-92 alloy.

As far as barrels I have a SR 9 that I had to sent the barrel back 3 times to get a barrel that didn't have a huge amount of machine marks in the barrel. Ruger customer service was really good to work with, but the rough barrels should never have left the factory.

[Forrest r]

Thank you dubber123 for the kind words but I'm not that good of a shot anymore, gotta use a rest now to shoot bugholes.

I quit buying lino-type years ago, just to much difference it it. I still do use mono-type and will mix mono/pure for any specific needs. Mono-type tends to be more consistent. I do also still use lead/tin alloys for some of the hp's I cast. Just got given another #60 of 50/50 so I'm pretty much set for life.

IMHO
I think there's to much made out of alloys/bhn's/pressures. Since the 80's I've used nothing but range scrap for 90%+ of my casting needs. Pretty complicated, make #100 batches and then the real hard part. Either air coll or water drop??? Yup 8/9bhn or +/- 13bhn. Shot countless 1000's of bullets in several caliber in a bunch of different firearms over the decades. Plain old nra 50/50 lube. Heck now it's to darn easy to find accurate loads with the modern coatings. Makes all the finding the right combo of the bhn/lube/load (pressure) so much easier.

I'm sure to op will get everything dialed in when his bbl comes back. For some odd reason I thought the rp9 was a remington pistol? O-well, getting old

[flybyjohn]

It is Remington. You are not that old yet.

[wimms]

As far as overpressure signs, the primers don't look any different than the factory Federal ammo I fired. The brass is not oversized after shooting and the recoil with the lighter loads is much softer. The powder fouling gets dirtier the lighter the load, which I think would be the opposite if it was extremely high pressure. Here is a bullet that was shot at a very low velocity, too low for the gun to cycle. It did not skid or loose any coating. No sure of the velocity as I was just trying to find the lowest load that would cycle. I am pretty sure it was the harder lead though.

flybyjohn,

In my understanding such full length radial shear can happen only from radial torque and that can occur only by means of excessive acceleration. Acceleration is directly proportional to pressure, so some kind of pressure spike must occur. It may be so short-lived that it does not show up on primers taking literally microseconds, but it could be sufficient to cause a skid, perhaps over only just 1/2 inch of boolit travel at some point within the barrel. Where is the leading in the barrel?

Take a look at these Pressure Trace graphs:


You can see delayed ignition there. RSI talks about low density charge being the cause for this.

My understanding is that when free space below boolit is critically under-filled with powder, during horizontal firing position it lays at the lower half of that space and primer ignites the powder only partially, mostly on the surface as opposed to through the whole bulk of it, gas produced with partial ignition is not sufficient to push the boolit and it gets stuck in the rifling. Now the powder pellets are in different stages of burn, are burning at different rates, the volume of space behind the boolit is rather large and the powder behaves quite differently from what it is supposed to do when all pellets ignite simultaneously behind continuously accelerating boolit.

I don't know if sudden pressure spikes can develop because of this, but I suspect it's possible. There is some evidence that large air/powder ratio can actually cause detonations.

One reason why heavy boolits can use faster powder (counter-intuitive isn't it) is because of their size, they take up more of the case volume and load density with less powder remains sufficient for reliable ignition. Smaller boolits need to load more powder by volume, and to remain within safe acceleration limits need to use slower powder.

Boolit weight with its resistence to acceleration is what creates the limited volume for expanding gases and is the cause for both pressure and temperature, and rate of burn. Lighter boolits simply move away with higher acceleration thus limiting the pressure, but may cause excessive radial torque. Heavier boolits limit acceleration and also radial torque. Too much fast powder behind a heavy boolit causes excessive pressure simply because it does not accelerate away fast enough to make room for the gases expanding at accelerating rate.

Some people add wads to keep the powder in the rear of the case so that primer blast goes through all the powder. This helps to blast as many pellets as possible at the same time so that ignition happens simultaneously. That is what makes powder work as designed and documented. Fouling could also be just a sign of delayed ignition.

Notice that despite delayed ignition boolit exit velocity was said to be very similar in above graphs, so chrono cannot be really used to get an idea of what happens inside the barrel. Same result can be reached through rather different sequence of events.

But, your soft boolits are sheared, and this means that at some point they faced excessive radial torque/acceleration. Larger charge may help by simply filling the case better and avoid boolit stoppage by means of better ignition, bringing the whole process of burn closer to designed sequence. Harder boolit simply withstands more torque, but it may also change the sequence of events and ignition delay.

Have you experienced a squib? Primer alone is capable of driving the boolit into the barrel. You can make a deliberate squibs without any powder with either of your alloys and test them. You'd need to hammer them out. Look for how far into the barrel soft vs hard alloy gets and feel how hard it is to get either back out. Also take a look at the engraving marks.

Most probably you'd notice that soft boolit gets stuffed deeper into the barrel, simply because it has lower friction. This means that there is more volume behind it that partially ignited powder gases have to fill, aggravating the delay and the shape of the pressure curve. Even neck tension holding the boolit has effect on initial sequence of events.

There is a minimum charge for a boolit weight of any powder. It is given because below it the ignition becomes unreliable and the behaviour of the powder unpredictable.

From pictures your barrel has very short leade so I don't think your boolits gain enough velocity to ram into the rifling and shear at that point. Pressure spike most probably occurs when they are fully engraved already.

[OS OK]

Thanks for your effort in posting this wimms...that was an excellent read.

"Now I can 'mull onit' for a while . . . c h a r l i e

[vzerone]

have to agree with larry. As a matter of fact ive had linotype buys that only tested 18bhn. 5050 ww/lino usually goes 16-18bhn and that's with good lyno. Never had a batch of ww test any harder then 12bhn. Most of it tests closer to 10. How are you testing it? Ive got both a cabin tree tester and a saeco. Now if your water dropping your ww you should be about right on the number at 18. If your bullet is testing 18 (water dropped as you said) its hard enough for about any handgun application and is hard enough where I doubt that's your problem at 9mm velocitys. One thing to watch in loading 9mm is to make sure you start the bullet in the case straight. With small bullets in my club fingers I have to allways keep that in mind because the 9 is about the worse offender when it comes to having bullets seat crooked. The way they enter the rifling a little off center can make marks that look just like stripping. Actually I too don't see enough evidence of stripping to think that is causing you any trouble. Keep in mind too that its a ruger not a les baer and the rifling might be cut with one land a tad wider then another. Again it shouldn't cause any real problem at handgun range. What are you calling bad leading. Is it actually building up more and more as you shoot to the point it effects accuracy. Or is it just a lead wash that gets no worse. About any gun shooting lead will have a light wash in it and I don't even concern myself with removing it. How many rounds before it effects accuracy. My guideline is if I can shoot the amount of bullets I usually shoot in two range sessions without groups opening up again I don't worry about it. If it is you can still use your alloy as long as your getting accuracy. Just buy a box of jacked bullets and load them up and shoot one about every 50 rounds and it usually will push any lead build up out. Same can be done with a gas checked bullet or even a very hard plain based bullet. Also being a ruger id consider right from the git go shooting maybe a 100 jacketed bullets through it, clean it thoroughly and then shoot cast. That usually smooths up the barrel a bit and make a slightly rough barrel a little more cast friendly.

Lloyd, I've alway felt that the 380 is much worse then a 9mm to be able to get the bullet seated straight.