Why different powder charges for lead vs jacketed bullets???

[Bigboreshooter]

Why do reloading manuals list different max powder charges for lead vs jacketed bullets of the same weight? (Example: 124gr FMJ 9mm vs. 124/125gr LRN)

I'm sure it's related to pressures, but what is the general rule regarding lead vs. jacketed?

Is is safe to use jacketed data for lead bullets and vice versa?

 

[the fatman]

What I have been told is that I can use jacketed data for cast bullets. But not lead or cast data for jacketed. I think friction plays a part. Jacketed bullets have more friction then cast or lead.

 

[slippingaway]

What I have been told is that I can use jacketed data for cast bullets. But not lead or cast data for jacketed. I think friction plays a part. Jacketed bullets have more friction then cast or lead.

That's what I've been taught as well. Lead is a lot easier to squeeze through the rifling than copper. Using lead load data with jacketed bullets can give you higher pressures than is recommended.

 

[Sugar River]

One reason is that lead offers less resistance to the rifling and doesn't need as much powder to achieve the same velocity.

Another reason would be to avoid leading with soft swaged slugs.

Pete

 

[I_Like_Pie]

another reason is that partial-lead bullets are less dense than a all lead bullet and have to be a bit longer for the weight to be the same...Thus many non lead bullets seat deeper in the cartridge with a same O.A.L.

Less case capacity = greater initial pressure = less powder that can safely be used to fall under limits


/or so I have been told

 

[Jimbo357mag]

What I have been told is that I can use jacketed data for cast bullets. But not lead or cast data for jacketed. I think friction plays a part. Jacketed bullets have more friction then cast or lead.

I think that is backwards. Generally lead max load data is less than jacketed bullet max load data. I know because I load a lot of Rainier copper plated bullets and they say to use the cast lead data rather than the jacketed data. There are exceptions.

Jacketed bullets can take very high pressures, lead, not so much usually.

Data for one bullet can not be exchanged for another bullet, even of the same type. Each load is a work-up for safety.

...Jimbo

 

[the fatman]

COFFEE POT
Hunter


Joined: 16 Mar 2003
Posts: 2219
Location: Prescott, Arizona
Posted: Fri Apr 17, 2009 3:49 pm Post subject:

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5 gr isn't all that much when you are using jacketed data for loading cast bullets. Just be careful as you approach max and watch for pressure signs. Also, though you can often use jacketed data for cast bullets, you CANNOT use cast data for jacketed bullets. Your pressures will skyrocket. If you are going to shoot a lot of cast bullets rather than jacketed, I suggest you get either Lyman's 49th edition manual that covers both or their cast bullet only manual.

This is where I got my original info.

 

[Bearlaker]

Wow this is confusing all of a sudden.
I've never used a cast load for a jacketed bullet, but Lee manual #13 lists a lower charge for the cast vs. jacketed.
.357 mag starting load for cast 158 gr 5.5 Unique//Jacketed 6.9
COL 1.57 for both.
edit
OK friction and pressure OK I need more coffee.

 

[Bucks Owin]

Weights being equal, generally it takes less powder to achieve the same velocity with a lead bullet vs jacketed, due to less friction and initial resistance to engraving I'd suppose.... I'm gonna try an experiment with coating jacketed bullets with alox or moly just for grins, we'll see if there's much difference in velocity using the same charge...

 

[Yosemite Sam]

Just to make it even more confusing, my Speer #13 lists considerably different loads for swaged lead vs. cast lead bullets, too.

-- Sam

 

[WESHOOT2]

Different bullets offer numerous differences, like malleability, bearing surface, jacket thickness (if jacketed), material, shape, and some other stuff.

So why (oh why) would someone assume that an appropriate charge for one would be appropriate, or even safe, for another, different bullet?

Manuals, and data, are intended as guides only.
Guides.....

 

[Charlie Two Tracks]

Now this is not fact but how I understand it. Lead will seal the chamber better than jacketed bullets. Swaged will seal better than cast. I am fairly new at reloading but I would have to look at the pressure of each round. 5 grains of "whatever" will have different pressures on each of the three bullets.
I'm pretty sure this is my first post here also. edit: my bad. Looks like it is #11 greaat memory so whatchout when you see my posts if it is from memory. I like my manuals.

 

[Jimbo357mag]

This will make it clear as MUD.

.44 Magnum From the Hodgdon online data.

240 GR. LSWC CAST Hodgdon Universal -- .430" 1.620" 10.2 1276 37,500 CUP
240 GR. LSWC CAST Winchester 231 ----- .430" 1.620" 11.0 1334 38,100 CUP


240 GR. NOS JHP Hodgdon Universal ----- .429" 1.600" 10.2 1246 38,200 CUP
240 GR. NOS JHP Winchester 231 -------- .429" 1.600" 11.0 1272 37,800 CUP

...Jimbo

 

[hutchman]

I too am a firm believer that you should never use a cast load for a jacketed bullet. However, this assumes that bullet construction is similar and the seating depth is the same. My guess is a cast bullet seated deeper in the case will produce more pressure than a similar cast bullet not seated as deep.

I guess this is the real reason for reloading manuals!

 

[Pal Val]

A couple years ago, I tried out some 240 gr .44 mag lead SWC bullets with my favorie load for jacketed 240 grainers - 24.5 gr H-110. The result was 50 bullets that made a pattern not even good enough for a shotgun, and a whole afternoon scraping lead shards off the barrel of my gun. Nevermore!

Another similar experiment with Berry's bullets ended up with the copper separating from the lead in flight and ripping up the paper targets.

A fool learns from his own mistakes. A wise man reads the manuals.