Cast vs Jacketed Load Data?

[billmc2]

320962

I've attached a printout from Hodgdon's Reloading data. This shows loads for 45 ACP 230 gr bullets using CFE Pistol. One is a cast bullet, the other is FMJ. These two listings have the same COL.

I know load data for cast bullets are different from jacketed bullets but I don't know why. Could someone explain to me why there are differences in the loads between the two for the same weight and length?

[Winger Ed.]

The jacketed bullet is harder to push down the barrel
and takes more powder to do it at the same speed as a cast one.

There are considerations for the powders burning rate that has to be factored in too.
That's why some are suitable for one thing, but not another.

Some can do sort of a balancing act and work (within limitations) for both cast & jacketed.

[M-Tecs]

Lead bullets having a lower pressure for the same load jacketed is not always true as shown in the OP link.

Cast --- 6.2 942 20,100 PSI
FMJ----- 6.8 934 19,800 PSI

more discussion here https://castboolits.gunloads.com/showthread.php?397658-Cast-vs-jacketed-pressure

[mehavey]

Lead bullets having a lower pressure for the same load jacketed is not always true...Theory du jour being that the cast/softer lead seals the bore faster/better/reducing blow-by -- thereby increasing pressure.

AT THE SAME TIME . . . I gotta wonder about the Hodgdon Data.
I'm getting "FMJ" velocities with Cast Lyman 452374/225gr (#2) loads
(6.2gr CFE-Pistol gives only 820fps out of a standard 5" gov' 1911 . . . nowhere near 942 that Hodgdon indicates
(kinda makes you wonder if they've got the loads (FMJ/Cast) reversed.

( YMMV comes to mind :roll: )

[castmiester]

Lee has 1 grain factor reduction for cast loads in with jacketed loads

[hermans]

Some good exlpantions here! I shoot 230gr RN cast as well as 230gr CMJ from time to time in IPSC style matches.
To achieve the same power factor I need to increase the powder charge on the CMJ's by 0.5 gr, using a fast burning powder.
The gliding properties of copper is different to that of a lead based alloy, the copper coated boolit takes more energy to be pushed down the barrel compared to a lead boolit.

[Bird]

Bullet diameters are different. Cast bullet has larger diameter= more pressure= more velocity.

[dverna]

Even for the same weight, cast vs jacketed bullets may have, different bearing areas, diameters and case volumes (seating depths). Those factors will affect pressure.

I do not need my loads to be at maximum so I do not worry about it. Another 50 fps in a pistol load is irrelevant. In fact, I do not have any pistol loads at "maximum" published data.

I do not shoot cast in rifles but still load under maximum published loads with jacketed as that is where I am getting the best accuracy.

[charlie b]

I have found that there is more difference between different published loads than there is between cast and jacketed. And what I get out of my guns is different between brands. I used to shoot three Colt mfg 1911's. One had a Barsto barrel, one a Colt NM, and one a Colt std (had a LOT of rounds through it). They were between 50 and 100fps different with the same loads. The NM barrel shot jacketed at a higher vel than cast while he other two the cast was faster (for the same powder loads, and bullet weight/shape).

[redhawk0]

I did some testing with Sierra 170gr FN and Lee 170gr FN Cast (172gr GC and Powder Coated) with my Winchester 94, 30-30.

The same load of Win748 produced an identical POI at 50 yards for me....YMMV I regularly switch between bullets and boolits with that gun.

redhawk

[Larry Gibson]

In pistol cartridges, after pressure testing attempting to prove this one way or another without success, I've come to believe the differences in measured pressures are more a function of difference seating depths. A very small difference in seating depth [not to be confused with OAL] can change the volume of small pistol cartridges enough to cause the discrepancies of measured pressures. Also keep in mind, as observed in the example M-Tecs' post, the less seating depth give greater case volume requiring more powder to achieve the same velocity and/or pressure.

[schutzen-jager]

FWIW - the original #1 Lee loading manual made no distinction between cast + jacketed in the loading tables -

[castmiester]

FWIW - the original #1 Lee loading manual made no distinction between cast + jacketed in the loading tables -

sorry, not in all calibers. I have the most recent manual

https://exhaustnotes.us/blog/wp-content/uploads/2022/12/20221221_0497-600-1.jpg

[schutzen-jager]

sorry, not in all calibers. I have the most recent manual

https://exhaustnotes.us/blog/wp-content/uploads/2022/12/20221221_0497-600-1.jpg

i clearly stated that it was in the #1 Lee manual + there is no differentation between bullets in all rifle + pistol calibers listed - i have used some of that data for over 1/2 a century in .32acp, .32 s&w, .32 s&w long , .38 s&w, .38 spec. .38 super, .357, 9mm, .308, .30/06 , 30/30/ + others with never 1 hint of any problems - not the hottest loads but they all performed perfectly ! -

[castmiester]

i clearly stated that it was in the #1 Lee manual + there is no differentation between bullets in all rifle + pistol calibers listed - i have used some of that data for over 1/2 a century in .32acp, .32 s&w, .32 s&w long , .38 s&w, .38 spec. .38 super, .357, 9mm, .308, .30/06 , 30/30/ + others with never 1 hint of any problems - not the hottest loads but they all performed perfectly ! -

understood, but I just wanted to show about the recent manual.

[Milky Duck]

this is the sort of thing I was asking some time back for 44 magnum as have lots of data for that but not much for shotgun powder and jacketed projectiles lol sort of the shoe on other foot. but as I always like to run load middle of road,it seems its not going to be an issue.

[JonB_in_Glencoe]

I know load data for cast bullets are different from jacketed bullets but I don't know why. Could someone explain to me why there are differences in the loads between the two for the same weight and length?

Accuracy.

[justindad]

Comparing load data across various bullets & various load manuals leads me to believe that we just don’t know everything there is to know about loading ammo and predicting pressures.

[billmc2]

Comparing load data across various bullets & various load manuals leads me to believe that we just don’t know everything there is to know about loading ammo and predicting pressures.

I appreciate all of the info and responses, but as you point out, I'm beginning to suspect there might be a good bit of Vodou involved as well. Its a wonder how any of us are still around with all our parts and pieces.

[Winger Ed.]

Its a wonder how any of us are still around with all our parts and pieces.

Yeah. Just don't shoot your eye out kid.:bigsmyl2:

[Kosh75287]

Except for the explanations already offered, I don't know how to explain the difference between load data for jacketed vs. cast projectiles. However, there are a few assumptions I make, when comparing data for one bullet type, to arrive at data for the other:

1.) All other factors being equal, bullets cast from homogenous lead:tin:antimony alloy will tend to create less friction against the barrel than projectiles that are jacketed in gilding metal.
2.) Cast bullets that are polymer coated will tend to exhibit still less friction against the barrel than uncoated conventionally lubed cast bullets. Depending on the cartridge and pressures involved, I usually observe a 2% - 5% increase in velocity, all other load characteristics being equal.
3.) Given equal bullet weights/diameters/lengths, a given charge weight of propellant will tend to produce lowest velocities with the jacketed bullets, followed by the conventionally lubed cast bullets, followed by the PC'd bullets. Pressures tend to run in the opposite direction.
4.) Given identical bullet weights and configuration, jacketed bullets will tend to be longer than cast bullets, because the gilding metal jacket has lower density than the lead alloy. Longer bullets mean greater seating depth, which means less unoccupied space in the cartridge. This can translate to higher pressures. In larger capacity cases, this difference may turn out to be negligible. In smaller-capacity cases, a slightly greater seating depth can mean a radical increase in chamber pressure with attendant unfortunate results.

[hermans]

Except for the explanations already offered, I don't know how to explain the difference between load data for jacketed vs. cast projectiles. However, there are a few assumptions I make, when comparing data for one bullet type, to arrive at data for the other:

1.) All other factors being equal, bullets cast from homogenous lead:tin:antimony alloy will tend to create less friction against the barrel than projectiles that are jacketed in gilding metal.
2.) Cast bullets that are polymer coated will tend to exhibit still less friction against the barrel than uncoated conventionally lubed cast bullets.
3.) Given equal bullet weights/diameters/lengths, a given charge weight of propellant will tend to produce lowest velocities with the jacketed bullets, followed by the conventionally lubed cast bullets, followed by the PC'd bullets. Pressures should run in the opposite direction.
4.) Given identical bullet weights and configuration, jacketed bullets will tend to be longer than cast bullets, because the gilding metal jacket has lower density than the lead alloy. Longer bullets mean greater seating depth, which means less unoccupied space in the cartridge. This can translate to higher pressures. In larger capacity cases, this difference may turn out to be negligible. In smaller-capacity cases, a slightly greater seating depth can mean a radical increase in chamber pressure with attendant unfortunate results.

Excellent explantion:)

[Larry Gibson]

Except for the explanations already offered, I don't know how to explain the difference between load data for jacketed vs. cast projectiles. However, there are a few assumptions I make, when comparing data for one bullet type, to arrive at data for the other:

1.) All other factors being equal, bullets cast from homogenous lead:tin:antimony alloy will tend to create less friction against the barrel than projectiles that are jacketed in gilding metal.
2.) Cast bullets that are polymer coated will tend to exhibit still less friction against the barrel than uncoated conventionally lubed cast bullets.
3.) Given equal bullet weights/diameters/lengths, a given charge weight of propellant will tend to produce lowest velocities with the jacketed bullets, followed by the conventionally lubed cast bullets, followed by the PC'd bullets. Pressures should run in the opposite direction.
4.) Given identical bullet weights and configuration, jacketed bullets will tend to be longer than cast bullets, because the gilding metal jacket has lower density than the lead alloy. Longer bullets mean greater seating depth, which means less unoccupied space in the cartridge. This can translate to higher pressures. In larger capacity cases, this difference may turn out to be negligible. In smaller-capacity cases, a slightly greater seating depth can mean a radical increase in chamber pressure with attendant unfortunate results.

Yes, they "should". However, after many attempts to prove this assumption through actual pressure testing, I have been unable to prove that assumption correct one way or the other.

Sometimes, with all else equal as close as we can make it, the pressure and velocity are higher with the jacketed bullet and sometimes the pressure and velocity are higher with the cast bullet. Thus far in testing, I've not been able to determine any hard or fast "rule". As I've stated numerous times before on this topic; "it just depends" which will give higher velocity and pressure with no indication which way it will be.

[dondiego]

Yeah. Just don't shoot your eye out kid.:bigsmyl2:

Very Christmas appropriate!

[Kosh75287]

Yes, they "should". However, after many attempts to prove this assumption through actual pressure testing, I have been unable to prove that assumption correct one way or the other.

Oh, I agree that the trends I describe are not "everytime things". But I see them more often than not.

Since you have access to equipment that can measure chamber pressures, I'll defer to your considerable experience in the matter, and your greater capability to quantify it. I nonetheless see the effect I describe when reloading rounds having an operating pressure north of about 28,000 p.s.i. MY "pressure indicators" are primer deformation compared to factory ammunition and (with auto pistols) slide velocity as measured indirectly by case ejection compared to factory rounds.

In 9mmP, .38 Super, and .357 Magnum, I can all but bet the rent that the effect I described in my previous post will show up. I SOMETIMES see it in .40 S&W, but not always. I NEVER use loads that give primer deformation signs in .45 ACP (perhaps .460 Rowland?), but case ejection distance vs. factory is still a fairly robust indicator.
I have seen SUGGESTIONS that the effect I describe was happening in Ruger/TC only loads in my .45 Colt Redhawk. The last time I saw significant primer flattening, observed velocities had such high SDs that the results were equivocal. In truth, I can usually obtain the upper performance level I desire from my .45 Colt RedHawk (250-260 gr. @ 1250 f/s) without deforming primers. With Alliant 2400 or one of the 4227s in a 7.5" barrel, it's not difficult.

I guess that if you and I were to run my loads for the cartridges mentioned through your pressure measuring equipment, we just MIGHT find that the pressure trend I describe is more apparent than real. I can only relate what I'M seeing, and how I interpret it. But I don't think that the way I am interpreting primer deformation and slide velocity (ejection distance) is without foundation.

Before posting my message previous to this one, I meant to add that one of the older SPEER manuals related an incident in which a 9mmP handload that developed ~29,000 p.s.i. at one o.a.l., but chamber pressures either approached or exceeded 60,000 p.s.i., when the o.a.l. was shortened by a small amount (0.015" or 0.020", if memory serves). I think this was part of the precautionary articles in SPEER #9, #10, or maybe #11.