Bore Leading Problem Caused By?

[Lead Head]

Bore Leading Problem Caused By?

Like many reloader shooters, I have had my share of bore leading. The problem as most of us that deal with leading problems know, there can be a number of causes and at times more than one cause at a time making the solution to the problem difficult to resolve.

There is a list of the common causes of bore leading that we tend to follow in an attempt to eliminate the leading. I will not get into the established list of causes that most of us are well aware of. What I want to do is introduce the readers to a cause that is most often overlooked and the calibers most affected by this least known cause of leading and poor accuracy.

My worst experience with bore leading has been with the 9mm Luger. The next has been with my 38 Super. I see on many of the forums dealing with bore leading, the 9mm is one of the worst and many replies come back saying, “I shoot the 45 ACP with thousands of rounds of lead and have no problems.” The 45 ACP is actually very different from the 9mm.

Now for the cause of the problem. Cast or swaged lead bullets are being swaged down to a diameter that is less than the bullet diameter was before seating. We work hard to choose a bullet diameter that is properly fitted to the gun, cylinder throats, groove diameter of the bore, only to have that diameter reduced by the shell casing it is seated in. Please read on because this is a very real problem with some cartridges. You can perform your own test to see just how much of a problem it is for you with your loading process and components. You sort out the different brands of brass you load. Then process the brass as you normally do and without primer or powder seat and crimp your bullets as you normally do. Now pull those bullets and measure them, base and upper portion. I am sure with some brands of brass you will be very surprised.

There are a couple of reasons for that. The 9mm operates at about twice the pressure of the 45 ACP and the 38 Super is even higher pressure. The cause of the problem? The 9mm and the 38 Super, because of the pressure levels they operate at require the wall thickness and or the hardness of the brass to be thicker or harder to withstand those pressures. These cartridges also have a taper inside, getting progressively thicker as you get nearer to the base. In my case when I seated a cast bullet cast from wheel weights and 2% tin, when the bullets were pulled, I found the diameters had been reduced by .001” to as much as .003”. Often this reduction in diameter was greater at the base of the bullet than the portion at the case mouth. The longer the bullet or the deeper they are seated into the shell casing the greater the problem. A secondary cause of bullets being reduced in diameter during the loading process is the use of the Lee Carbide Crimping Die. If when using this die, there is any real sizing done, the bullet will be reduced in diameter and this can lead to bullet set back during the auto loading cycle because the bullet does not spring back as much as the harder brass causing less bullet retention in addition to leading the bore. I do like the Lee die, but not as a final resizing of the loaded round  If there is a problem with chambering, I fix it so use of the Lee die is not necessary.

The 45 ACP is not immune to the problem, but is not near so bad as the other short cased pistol rounds. I would guess the 40 S&W and a few other calibers would experience this problem also.

I took three different brands of 9mm brass, Winchester, R-P an FC and processed it as I always do, seated a .355” diameter jacketed bullet and taper crimped to remove any bell. Then I measured the outside diameter of the rounds where the bullet is inside the shell casing. I found with the brass I have, the diameter varied from the smallest to largest, .003”. That means is my case, the R-P brass is .0015” thicker per side that the FC brass which is the thinnest.

Without boring the readers to death, I found the FC brass being thinner worked best for my cast bullets sized at .3565” to .357” diameter. With my 9mm and 38 Super I played with the different sizing dies I have and expanders to come up with the combination that provides good bullet retention without reducing cast bullet diameter. Not all sizing dies or expanders are equal. For jacketed bullets in the 9mm, I prefer the R-P brass and .355” bullets for good bullet retention.

Long pistol cartridges like the 38 Special, 357 Magnum or the 45 Colt have enough give in the case that seating a cast or swaged bullet rarely causes a reduction in bullet diameter. Too much taper crimping or use of the Lee Carbide Factory Crimp Die can mess things up. Being aware this can be a problem will help the reloader avoid being the cause of a leading or poor accuracy problem.

[Nobade]

Sir, you are quite perceptive. Often a larger than normal expander ball is called for to get this to work properly, and generally you want that case to be about as big as possible and still chamber. This way there's as much room as possible for the bullet inside. You see the same thing with 38 spl wadcutter ammo. If you load them with the normal die set, the accuracy is not too great since the bullet is being sized by the case. If you either use a large expander ball or just don't resize the cases and taper crimp to hold the bullet in place, accuracy is often much better. 9MM presents a unique challenge as you explained, plus it has to survive the trip from the magazine to the chamber without having the bullet telescope into the case. It can be done to work very well, but you have to pay attention to what is going on and not just slap ammo together.

[Siskiyou]

Lead Head a very educational post. 

I have just returned to reloading the 9MM after a long absence. 

One of the first goals to was to utilize the remains of past bullets, and powder on hand.  I do not cast and I do not recall the origin of 124-grain bullets that I recently loaded.  I do recall they provide good accuracy from Federal cases using PB and 700X.

On this go around I used PB and WIN cases.  My original loads were with standard 9MM dies, this time around I used the Lee 4-die carbide set.  I am now forewarned that if accuracy has dropped off the problem maybe in the crimping.  I finished off the cast bullets.

If I understand your post I should avoid the 4th die, the taper die.   I did measure the loads on the brass because of head spacing concerns and they were at spec.

I also loaded the 123-grain plated bullets I had following the same process. I noted a slight line around the plated bullets after I pulled a couple to test bullet tension and examined what was happening.  It did not enter my mind to see if the process had resized the bullet.

If I correctly understand the information with the Lee Carbide Crimp Die is that it does not contact all rounds, only those that have need correcting.    I state that with a few question marks in my mind.

I have a very good supply of cases with the WIN headstamp, a few R-P, and a fair supply of Federal.  I am currently looking at a fair supply of Remington 124-grain FMJ.  Any advice regarding the taper die and FMJ?

I have not encountered any problems with the Hornady carbide die for the 38/357 which I have been using for many years.  But life is simpler in a cylinder than a double stack magazine.

[Lead Head]

I found my 9mm brass, R-P thickest, Win., in the middle and the FC the thinest.

Using .355" diameter jacketed bullets, the R-P and Win. provided good bullet retention. The FC brass didn't work well using the .355" jacketed bullets. Bullet retention was not very good and loading cycle bullet set back was a problem. I used a RCBS carbide and steel sizing dies with a undersized expander but wasn't happy with the results. The R-P and Win. brass was fine. I tried my Lee Carbide 9mm sizing die and it sized so large the brass wouldn't hold any bullet size well. I should send it back for replacement.

I use only the FC brass with my cast bullets and get good bullet retention without having the bullets undersized by the brass. Attention has to be paid to the size of expander used. Too large and you lose the bullet retention.

Cast bullet diameter for my Dan Wesson PM 9 is best at .3565". The match chamber is tight enough that .357" diameter bullets and the thin FC brass can cause failures to chamber fully. The outside diameter at the case mouth is a little too large to chamber well. I have problems with leading in my PM 9 when using the faster powders like Win. 231 and 700X. As others have found out, when I went to AA 7 powder the leading went away. There is something about the slower pressure curve that  reduces or eliminates the leading. Jacketed and plated bullets are very different and the two can not be treated as equals. My PM 9 likes the 124gr. and 130gr. jacketed bullets best. The exception is a factory Winchester 147 grain HP Personal Protection loading that is a real tack driver.

I do use the taper crimp die. I crimp to remove the bell of the case mouth and no more than .001" actual crimp at the case mouth. Over crimping with a taper crimp die is a problem and should be avoided. The taper crimp die is what a person should use with cartridges like the 9mm, 38 Super, 10mm, 40 S&W and 45 ACP. Over crimping with the taper crimp die will undersize the bullet, cause a lose of bullet retention and in really heavy crimping, cause a lose of proper head space of the cartridge. Contrary to popular belief, more crimp with a taper crimp die has the opposite affect of what is expected. Less grip not more.

I do not used the Lee Carbide Factory Crimp Die with loaded rounds. There are too many variations in the outside diameters of loaded rounds due to different bullet diameters and brass thickness. The die can cause bullets to be undersized and a lose of bullet retention, because the bullet doesn't spring back like the shell case does. If the reloading of ammunition is done properly, there is no need for the Lee Carbide Factory Crimp Die. Any bulges that can cause rounds to not chamber are either created during the reloading process or not removed during the resizing of the brass. A bulge near the base is usually removed with the resizing die. If partial sizing is desired this bulge may not be removed. A bulge at the seated bullet or the base of the bullet is often caused by improper adjustment of the roll crimp die. Properly adjusted crimping dies and brass that is the correct length will not cause a bulge. I do use partial resizing with many of my pistol cartridges and in that case I use the Lee Carbide Factory Crimp Die without the crimper in the die, and full length size the brass first with the Lee carbide ring. This will remove any base bulges. Then I partial resize with the standard die to the depth I desire for bullet seating.

I haven't used the plated bullets in my 9mm or 38 Super yet, but I do intend to. I have 130 grain, .356" diameter and 158 grain plated bullets sized .357" diameter. I plan to use the 130 grainers in the 9mm and 38 Super. I use the 158 grain HP, .357" diameter plated bullet in one of my 357 magnums and they are a tack driver as long as the velocities are held down to avoid the bore fouling.

[Siskiyou]

Bullet tension was/is a concern so after setting up the Lee Carbide Die set, I loaded some dummy lead, plated, and FMJ rounds short the powder and the primer.  The concern is related to functioning and integrity of the load.  I tested them for function in my firearm and then used my RCBS Impact bullet puller as a bullet retention tester.  It took approximately three whacks on the end of a 4x6X3” what I have next to my bench to dump the bullet.  This is consistent with other ammunition I have pulled the bullets with in this manner.

I am glad you mentioned using a slower burning powder to prevent or reduce leading.  I was looking at the old IMR data for 800X for 9MM loads.  The data shows high velocity and lower pressure than 700X.  With the firearm designed to work with the higher pressure loads will ejection issue crop up?  I have a couple of cans of 800X in my inventory and looking for an avenue to make use of it.

Another slower powder option that I have is Alcan AL-8.  I have data for AL-8 in the 38 Special and 357 Magnum but none for the 9MM.  Are you aware of any old publishing data with this powder in the 9MM?  It would appear to fall in the slower burning rate for the 9.

Your post helps me on another case, that being case selection.  After such good results with the Federal (FC) cases using the 124-grain bullet I processed and set aside a few hundred of them for future loading.  I had not considered that changing to FMJ bullets would generate a bullet retention problem.  The problem is easily dealt with by using WIN brass which I have a good supply. 

Normally when I visit the indoor range during the winter I do not shoot the 9mm because they get any brass that crosses the firing line, which is a good safety measure.  I need to make an exception and try my recent 9MM loads to see if I am on the right track.

Finding 9MM bullets in stock is a little bit of a hit or miss affair.  I have recently purchased Remington FMJ, and came across 9MM plated bullets.  The dollar says between them was only a couple of dollars or less than a half a cent per bullet. 

Thanks for the helpful information.