why such a difference in load data between lead and jacketed bullets


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357reloading
October 15, 2010, 11:07 AM
why such a difference in load data between lead and jacketed bullets?

Only thing i can figure out is lead must have more friction on the barrel and the faster speeds would cause leading, leading to other problems.

While I am on my toot, why do I almost never see load data for gas checked bullets?

Thanks

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ants
October 15, 2010, 11:38 AM
Lead generally conforms to the bore better and can be sized more exactly to fit the bore, thus it is inherently more efficient. It often takes less powder to get the same pressure (and velocity).

You mentioned leading. The hardness of the bullet, lubricant type, and powder charge are combined factors. There isn't just one factor that contributes to lead deposits.

Get books (like Lyman) especially published for cast lead bullets. Tons of info, including Gas Check loads.

CraigC
October 15, 2010, 11:39 AM
Jacketed bullets produce more friction and thus, more pressure. Cast bullets are lubricated and will typically produce 50-100fps higher velocity than a comparable jacketed load.

What are you loading for, be specific?

357reloading
October 15, 2010, 11:51 AM
was just a general question. Only kill paper targets, so i shoot mostly lead. load 100 grain 380,158 grain 38 spec 357,124 grain 9 mm, 175 grain 40 s&w and 10 MM.

All my loads now are lee tumble lube, and load data for 16 pounds of ramshot true blue. Had to write to Ramshot to get most of the load.

ReloaderEd
October 15, 2010, 11:56 AM
gas checks don't make a difference as far as pressure is concerned. They protect the base of the bullet however cast bullets made out of lynotype metal or wheel weights which I use for pistol bullets don't really need gas checks. Rifle bullets on the other hand need gas checks if over around 1500 fps. I use valve grinding compound in the lube grooves of about 5 bullets that clean up any leading problems in pistols and improve accuracey. Rough barrels can also hurt jacketed bullets and you can see the copper in the lands and grooves of the barrel. be safe

qajaq59
October 15, 2010, 12:01 PM
ReloaderEd, is there just one type of valve grinding compound? If not, which one is best for smoothing out a barrel?

Robert Palermo /Penn Bullets
October 15, 2010, 12:03 PM
Most of the load data originally developed for lead bullets was for the soft swaged bullets being offered by the major bullet makers. Over the years as hard cast bullets became available addtional load data became available and as such you see such data on the Hodgdon and Vit web sites as well as with other powder mfgs such as Accurate and Alliant.

Soft swaged bullets would lead severly if pushed beyond very moderate velocities.
Harder cast bullets would take much more velocites up to the magnum speed range if the alloy was up to the task and proper magnum speed powders are used.
Lead bullets offer less resitance in the bore than copper clad or jacketed so with all other factors being equal with regard to a given load the lead bullet will achieve higher velocities. In some cases that velocity gain can be as much as 150 fps.

357reloading
October 15, 2010, 12:05 PM
Lapping compound, I have a Kel Tec 380 . was terrible for failures, misfires etc. Put in table spoon of fine lapping compound, fired 200 rounds . Decent gun, still testing to see if i can trust. Really like the gun, hope i can get my reloads to function .

Tried commerial ammo, had same problems as my reloads. I did find .after two clips had to clean the chamber. Was using Unique powder. Changed to Ramshot true blue. much cleaner

357reloading
October 15, 2010, 12:29 PM
seveal types of grinding compound .as for smoothing out a barrel . have no clue.

CraigC
October 15, 2010, 12:58 PM
I wouldn't be in a hurry to force an abrasive down my bore. For the abrasive-laden bullet knows not the difference between high "rough" spots and the sharp corners of your rifling. Rounding off those corners, not a good idea.

rfwobbly
October 15, 2010, 01:08 PM
Valve lapping compound is wonderful stuff, but is generally made from aluminum oxide, known in the trade as "Carborundum", suspended in a grease. (This is the same abrasive grinding wheels are made from.) Aluminum oxide rates on hardness with diamonds and as such is one of the hardest substances known. If it gets loose in your gun it will wear any part it contacts. Hardened steel is no match for aluminum oxide.

Adding the stuff is easy. Getting rid of the stuff is where the problem enters. You cannot reliably wash it off with thinners, trichlor, alcohol or other common strippers and solvents. It will take a scrub brush, and a strong detergent in hot (soapy) water to lift the abrasive out of anywhere it may wander into.

Many people don't understand the difference. A "solvent" simply dissolves grease and oil. It takes a "detergent" to properly lift particles out of/ off of a metal part. Even an ultra-sonic cleaner may not lift an abrasive off if the vat is not filled with detergent.

;)

bds
October 15, 2010, 01:09 PM
was just a general question. Only kill paper targets, so i shoot mostly lead. load 100 grain 380,158 grain 38 spec 357,124 grain 9 mm, 175 grain 40 s&w and 10 MM.
357reloading, the primary difference in load data between lead and jacketed bullets has to do with the bullet diameter and the material the bullets are made of which translates to bullet-to-barrel fit that directly affects chamber pressure. And yes, jacketed bullets generate more friction with the rifling than softer lead lead bullets (although most lead bullets are harder lead alloy).

Jacketed bullets are smaller in diameter than lead bullets of the same caliber (typically 0.001" smaller):
9mm: 0.355" jacketed vs 0.356" lead
45 ACP: 0.451" jacketed vs 0.452" lead

Most factory barrels are cut to match the smaller diameter jacketed bullets and when fired, there are gaps that exist between the bullet and rifling land/grooves where hot gases escape around the bullet which decreases some chamber pressure. With the larger diameter lead bullets (typically 0.001" over the barrel diameter), the softer lead alloy "digs" into the rifling when fired to seal the bullet against the bore of the barrel and you have less hot gas escaping which increases the chamber pressure. This is the reason why lead load data is often lower than jacketed load data.

As to leading, when a lead round is fired, you will have hot gasses escaping around the base of the bullet and the heat from the gases will soften the base of the bullet causing leading near the chamber end of the barrel bore. So check the barrel bore size or slug the barrel to determine the barrel size and order the lead bullet that is 0.001" over. Gas check prevents the base of the bullet from melting from this heat and reduce leading (think of it as jacketed bullet wanna be lead bullet).

However, even shooting properly sized bullet (0.001" over) will cause leading in the barrel if pushed too slow. Why? When the primer ignites the powder, the expanding gas pushes hard on the base of the lead bullet like a hammer. This pressure shot wave expands the base of the lead bullet a bit and help seal the bullet to the barrel - this is called obturation. If you shoot light "paper punching" target loads, the base of the bullet may not obturate and still allow some hot gases to escape around the base of the bullet, and this causes melting of the bullet base and leading - also called "gas cutting".

So, you have two options if you want to minimize leading:

1) Increase the powder charge until you get proper obturation of the bullet base without exceeding the max load.
2) Shoot softer lead bullets that will obturate with lower powder charge. Most commercial lead bullets are available at 12-24 BHN range. If you push your bullets to max load data, 24 BHN will do well. 18 BHN will do well at mid-high range load data and 12 BHN will do well at low-mid-high range load data. If you are looking for lighter target loads, Missouri Bullets (http://www.missouribullet.com/) carries lead bullets at 12 and 18 BHN.

357reloading
October 15, 2010, 01:10 PM
when i put lapping compound in my kel teck . i put on the moving parts. slide etc. not in the barrel. slicked up the feed ramp with lapping compound and dremal tool with ploshing wheel.

ReloaderFred
October 15, 2010, 01:17 PM
Robert Palermo pretty much nailed it. Prior to the mid to late 1960's, most handgun data was for lead bullets, since jacketed bullets hadn't come into common usage until about then, with the exception of military applications. Now the pendulum has swung the other way, with newer shooters believing that shooting lead bullets is a new phenomenon.

If you want good cast bullet data, then buy at least one of the cast bullet manuals. Lyman prints an excellent one and the old RCBS manual was also good, but they only had one printing. Oregon Trail also has a good cast bullet manual.

These are actual manuals, printed on real paper, where you turn the pages and read words. It may be an old concept, but it actually works, and has for many, many years..............

Hope this helps.

Fred

snuffy
October 15, 2010, 01:18 PM
If you want to do bore lapping, use the right stuff!

http://www.midwayusa.com/viewProduct/?productNumber=486249

http://media.midwayusa.com/ProductImages/Medium/486249.jpg

A rough bore can cause leading, OR copper fouling. The Wheeler system has 3 grades of abrasives. A real rough bore should use all three. But a bore with minor roughness may only require the finer grit,(600).

Read the reviews on the midway site. They say there's no instructions, but mine came with them. You spread the grit on the smooth steel plates and apply down pressure while rolling the bullet into the grit. It works by embedding the grit into the surface of the bullet.

A lot of people are VERY hesitant to try it, but are happy with the results.

Oops, the first one is without the steel plates.

http://www.midwayusa.com/viewProduct/?productNumber=646612

jcwit
October 15, 2010, 01:20 PM
I use valve grinding compound in the lube grooves of about 5 bullets that clean up any leading problems in pistols and improve accuracey.

My God, I now believe I've heard just about everything.

And I got into a HUGE discussion over on Cast Bollits regarding using paste auto wax in my lube receipe. Some thought the polishing comp in most auto waxes would wear out the barrel, possible maybe, but not in my lifetime. Furthermore I stated in the discussion I did not use a cleaner wax. Go Figer.

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