Powder coat and chamber pressure

I powder coat my cast projectiles and load them according to the cast lead loading data but find some differences in performance which makes me wonder what effect powder coating has on chamber pressures and whether a new set of loading data be developed. I find in my very light pistol loads (32 S&W Long) 1.5 grains I need to crimp harder or add a bit more powder (to up pressure.I think) other wise there is a loss of accuracy , similar with 38 in my revolver but at top end loads I get improved accuracy (9mm) .

Has any one done any testing on various rounds and compared them, for example 45acp fmj compared to 45acp .cast and traditionally lubed and 45acp powder coated. Same with 9mm .38 etc, with the same load of powder and weight bullet.

Does a bottle neck cartridge behave differently and does using them in rifle loads make a difference.

I think a new set of loading data could be required but unless non subjective tests are done it is only guess work. Has anyone done this type of testing with the correct equipment, would anyone else like to know?

I think Larry Gibson may have done some powder coated bullets for someone. If he doesn't check in here try sending a PM. I think he is the only person in this forum with pressure measuring gear.

The assumption is PC is slick and the bullet leaves the neck easier so more crimp is used to get powder to burn better. I don't shoot revolvers so no crimp groove needed, just set neck tension and remove the flare.

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Originally Posted by Driver man

I powder coat my cast projectiles and load them according to the cast lead loading data but find some differences in performance which makes me wonder what effect powder coating has on chamber pressures and whether a new set of loading data be developed.

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PC may be "slick" but it makes bullets fat. I have loaded a Lee 168-358 (discontinued) for subsonic 9mm since 2002 , a few years with Hi Tek coating now. All was good.

But now that I discovered PC and I like it, that same bullet doesn't work anymore because PC fattens the nose too much. It may chamber every now and then but not really. Pressure will be higher with the fat nose of course.

I'm using MP Hammer for 9mm subs now.

In my opinion, a separate PC data still wouldn't work for anyone elses particular barrel / bullet size combination so that's why we start low.

I've found the same thing that some of my firearms don't like the fatter nose due to PC-- so I resize those after PC and, for me, that solved the problem. In my rifle cartridges I have not noticed any accuracy change with PC-- except for my Enfield that got more accurate when I switched the same bullet from lube to PC. I think its worth taking the trouble to re-do some of the load ladders when switching, just because it makes the bullet a little different. I have not seen any indication of significant pressure changes (that is, no noticeable velocity or primer changes-- I don't have the equipment to check chamber pressure).

At the range yesterday i fired some loads I had loaded in my K frame 19-2 357 revolver. I had loaded a 148gw/c with 3grains of w231 .I loaded 20 with alox lubed and sized 358 and 20 pc with Smokes translucent copper and sized 358 both crimped in the crimp groove with the same die setting. I am using 38 starline brass.
At 25 yards the pc shot about a 3 inch group an inch higher and an inch to the right ,the alox shot a ragged hole thru the x ring . This is my target load and I have used it for years. The pc had unburnt powder. To achieve similar grouping with pc I have to load up to 3.3 grains of 231. I think there is quite a difference in chamber pressure between the pc and alox lubed wadcutters.

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Originally Posted by Driver man

At the range yesterday i fired some loads I had loaded in my K frame 19-2 357 revolver. I had loaded a 148gw/c with 3grains of w231 .I loaded 20 with alox lubed and sized 358 and 20 pc with Smokes translucent copper and sized 358 both crimped in the crimp groove with the same die setting. I am using 38 starline brass.
At 25 yards the pc shot about a 3 inch group an inch higher and an inch to the right ,the alox shot a ragged hole thru the x ring . This is my target load and I have used it for years. The pc had unburnt powder. To achieve similar grouping with pc I have to load up to 3.3 grains of 231. I think there is quite a difference in chamber pressure between the pc and alox lubed wadcutters.

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Did the accuracy improve?

Yes, accuracy improved to nearly the same as alox. I use a rest to test my loads and the pc at light loads is not quite as good. I sometimes dip the pc coated wad cutters in a carnauba /solvent solution and allow to dry for some of my full power loads .

Do you think the wax makes it “stickier” in the barrel and allow the lower powder charge fully burn?

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Originally Posted by Driver man

Yes, accuracy improved to nearly the same as alox. I use a rest to test my loads and the pc at light loads is not quite as good. I sometimes dip the pc coated wad cutters in a carnauba /solvent solution and allow to dry for some of my full power loads .

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Originally Posted by Driver man

Yes, accuracy improved to nearly the same as alox. I use a rest to test my loads and the pc at light loads is not quite as good. I sometimes dip the pc coated wad cutters in a carnauba /solvent solution and allow to dry for some of my full power loads .

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I see you're in NZ.I get my non TGIC PC from Resto supplies...

If I use a HBWC in my 32 and 38 that has been powder coated the skirt will clamp itself to the inside of the case when fired and split the boolit in two regardless of load levels and just the boolit head will leave the case.
By applying my wax it shoots very accurately and in one piece . I used to swage my 32 HBWC untill I got a dewc mould from Mihec which shoots just as good. I think powder coating alters the load dynamics in many and varied ways.

if you have to seat deeper because of the PC then yes there will be increased pressure

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Originally Posted by Driver man

If I use a HBWC in my 32 and 38 that has been powder coated the skirt will clamp itself to the inside of the case when fired and split the boolit in two regardless of load levels and just the boolit head will leave the case.
By applying my wax it shoots very accurately and in one piece . I used to swage my 32 HBWC untill I got a dewc mould from Mihec which shoots just as good. I think powder coating alters the load dynamics in many and varied ways.

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Thanks, that is very interesting. I just coated a bunch of 38 HBWCs guess I’ll try lubing them.

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Originally Posted by JimB..

Thanks, that is very interesting. I just coated a bunch of 38 HBWCs guess I’ll try lubing them.

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Wondering how your pc HBWC lubed shoot for you

Several years ago I had Donnie Miculek coat some of my boolits for an Area USPSA match. I had never shot coated boolits before but was trying to keep the gun clean for the duration of the match. Never gave a thought to the other consequences of coating the boolits. When I got to the chronograph station the first 5 rounds failed to make the required velocity for the power factor by half a point (power factor of 164.5). The rules allow for a second try and that attempt passed by less than one full point (power factor of 165.2). The reduced friction of the coating kept the ammunition from developing the pressure that I got using a conventional lube. The same load with a conventional lube made power by over 5 points; over 170.

Slicker boolits need a harder crimp, more powder or maybe a little of both to reach the same velocity.

I loaded some 150gr MP 9mm PCed and sized to .357 using 147 jacketed load data for a similar profile bullet, seated to the same depth. Predicted velocity was 975, Quickloads said the same and predicted a chamber pressure of 34kpsi. When I actually pressure tested these they shot 1008fps avg with an average pressure of 28kpsi. I have been using jacketed load data for several years and noticed that *almost* (thats a legal term, ymmv) always the velocity will be slightly higher and the pressure lower for a similar bullet weight, profile and powder charge.

*Edit. I have had one or two issues with bullet set back in autoloaders over the years so I use a decent Lee factory crimp on almost everything.

Coopaloop86 your figures "almost" the same as I stated 6 years ago in my testing. Pc'ed bullets will generally shoot 4 to 5% faster than lubed or jacketed at same powder charge. Also generally you will need to rework any old load your using as barrel harmonics changed with speed increase.

Are you suggesting that powder coated boolits could be loaded using FMJ data plus 5 or 10%extra powder.
Might be interesting to do a test

The only direct comparison I have with ammo loaded on the same day with the exact same powder and die settings is with 450 Bushmaster. These were light loads with a 304 grain bullet and 11 grains Unique. The mold has 2 cavities for gas checks and 2 cavities plain base. The Lubed bullets shot 10 to 20 FPS faster.

304 Lubed Lead Plain Base 1,149 FPS
304 Lubed Lead w/ GC 1,150
304 PC No GC 1,127
304 PC Plain Base 1,139

This is truly an interesting thread. Shot 2 batches of my 1st PC'd bullets--Noe 234 gr RF TL. 4.5 gr BE. The tumble lubed bullets (using lsstuff alox) was more accurate and recoil was milder.

The pc'd bullets were not as accurate and recoil was more noticeable. I shall try upping the charge by 0.3 grains.

Leaning something new every time.

I'm not so much suggesting, just telling you what works for me. I almost exclusively use jacketed data of a similar weight and profile for PCed boolits and find that I get slightly better velocities with slightly lower pressures. With the proper fit it also leaves my barrels squeaky clean.

How do you know you get lower pressures? And how much difference in velocity?

I used to think that copper plated bullets would work like jacketed, but, mfg loading data says otherwise. I wish someone with the proper gear would measure pressures for PC bullets. There is a lot of speculation on this topic but I have not seen anything measured.

I do find that PC bullets are very slightly less accurate than lubed. They do seem to be less 'tolerant' of load, ie, takes a bit more tweaking to get a good load than it does with lubed bullets.

Sent from my SM-P580 using Tapatalk

Im wondering if anyone has anything to add to this thread

I ran an extensive pressure and velocity test using the Lee 452-230-TC naked and lubed with BAC vs 4 different PCs. The test included identical loads except for the PC in the 45 ACP and 45 Colt in 5 handguns and two rifles.

The PC'd bullets neither raised pressures not increased velocities above the naked/lubed bullets. All variations of pressure and velocity were well within normal test to test variation.

Here is the data;

45 ACP/452-230-TC/5 gr Bullseye/WLP/R-P Case
Sherman Williams
Metallic Silver 1 Coat
Firearm…………… Grp @ 25 yd……..Velocity……SD……..ES……psiM43)…..SD……ES……..
TC Contender………3.9”..(8 in 2.8”)……1019 fps….11 fps…35 fps…..20,200…….900…...3,300……
S&W M1917/25…….4”…(8 in 3”)……….890 fps….15 fps…54 fps…....
Colt Gvm’t M1911….5.5”…………………919 fps…..12 fps…42 fps……
M98 Rifle..(50 yd).....3.2”..(7 in 1.1”)…….1046 fps….17 fps….58 fps…..

Sherman Williams
Metallic Silver 2 Coats
Firearm…………… Grp @ 25 yd…..Velocity…….SD…….ES………psiM43)…..SD……ES……..
TC Contender………4.6”……………..1006 fps……19 fps…58 fps……19,400…...1,200….3,400…
S&W M1917/25……5.4”..(9 in 4”)…….903 fps……14 fps…41 fps
Colt Gvm’t M1911…6.5”………………919 fps…….19 fps…54 fps
M98 Rifle…(50 yd)…5.25”……………1044 fps……10 fps…33 fps

Cardinal Pearlescent
Steel Gray 1 Coat
Firearm…………… Grp @ 25 yd…..Velocity….…SD…….ES………psiM43)…..SD……ES……..
TC Contender………4.4”……………..1002 fps……14 fps…53 fps……19,900……1,500…4,000
S&W M1917/25…….4.9”………………895 fps...…17 fps…54 fps
Colt Gvm’t M1911….5”………………...917 fps…...10 fps…35 fps
M98 Rifle..(50 yd)…5.2”………………1038 fps…...13 fps…48 fps

Cardinal Gloss
Black 1 Coat
Firearm…………… Grp @ 25 yd……Velocity……SD…….ES………psiM43)…..SD……ES……..
TC Contender………2.2”………………996 fps……16 fps…..61 fps……18,700……1,200….4,100
S&W M1917/25……2.2”………………886 fps……16 fps…..43 fps
Colt Gvm’t M1911…3”…………………917 fps……9 fps…...31 fps
M98 Rifle…(50 yd)..3.6”…(8 in 1.4”)…1035 fps…...14 fps….43 fps

Naked Cast
BAC Lube
Firearm…………… Grp @ 25 yd….Velocity…..…SD…….ES………psiM43)…..SD……ES……..
TC Contender………2.1”……………..1004 fps……12 fps….40 fps…..18,900…….900……2,900
S&W M1917/25……2.25”…………… 917 fps……..9 fps…..30 fps
Colt Gvm’t M1911…2.75”…………….922 fps…….12 fps….37 fps
M98 Rifle…(50 yd)…2.2”……………1060 fps…….15 fps….45 fps

45 Colt/452-230-TC/7 gr Bullseye/WLP/W-W case
Sherman Williams
Metallic Silver 1 Coat
Firearm………………. Grp @ 25 yd….Velocity………SD…….ES……psiM43)…..SD……ES
TC Contender………….2.8”……………..1080 fps……10 fps….34 fps…..14,800……800……2,900
Uberti Evil Roy SAA…..3.6”……………..896 fps……..12 fps….34 fps..
Uberti M73 Carbine..(50 yd)..3.6”………...1153 fps……12 fps…41 fps

Sherman Williams
Metallic Silver 2 Coats
Firearm………………. Grp @ 25 yd….Velocity……..SD…….ES………psiM43)…..SD……ES
TC Contender…………..3.1”……………1070 fps…….12 fps….39 fps…..15,700……500……1,700
Uberti Evil Roy SAA…..3.6”…………….900 fps……...8 fps…...24 fps
Uberti M73 Carbine..(50 yd)….2.8”..……1142 fps…….8 fps……27 fps

Cardinal Pearlescent
Steel Gray 1 Coat
Firearm………………. Grp @ 25 yd….Velocity………SD…….ES………psiM43)…..SD……ES
TC Contender………….3.9”…………….1070 fps……..7 fps….20 fps……16,000……600……1,700
Uberti Evil Roy SAA…..5”……………….899 fps……..18 fps…59 fps
Uberti M73 Carbine.;(50 yd)..4.2………...1135 fps………5 fps…17 fps

Cardinal Gloss
Black 1 Coat
Firearm………………. Grp @ 25 yd…..Velocity…..…SD…….ES………psiM43)…..SD……ES
TC Contender…………..1.8”……………1066 fps…….11 fps….31 fps……15,900…..500……1,700
Uberti Evil Roy SAA…...2”………………896 fps……..10 fps….31 fps
Uberti M73 Carbine..(50 yd)..2.5”………..1134 fps……13 fps…..49 fps

Naked Cast
BAC Lube
Firearm………………. Grp @ 25 yd…..Velocity……SD…….ES……..…psiM43)…..SD……ES
TC Contender…………..1.8”…………….1078 fps….9 fps…….35 fps……16,700……900……2,900
Uberti Evil Roy SAA…..2”………………..902 fps….12 fps……44 fps
Uberti M73 Carbine..(50 yd)..1.7”………..1135 fps…..5 fps…….15 fps

I thought Id read all your posts but I must have missed this one . Thanks for reposting . I will add this to my files.

Years ago I did a small test of plain lube and sized boolits versus pc'd and sized boolits in my S&W 67-1 revolter with a 4 inch barrel clamped in a ransom rest at 33 yards. The plain boolits were sized and lubed in my LAM 2 filled with BAC, sized .358. The pc'd boolits were coated with yellow/green from Smoke and sized to .358. All were loaded in WW Super 38 special brass, Winchester sp primers and charged with Titegroup powder. The chrono was 10 or 12 feet from the muzzle, I don't remember, been too many years. After I settled the pistol in the rest I shot a group with Magtech 38 special+p 158 gr sp factory ammo for grins, six shots grouped into 2.17" at 808 fps. I fired all the lubed/sized loads first, then fired 6 more of the factory loads to burn the lube out of the barrel, the group was 1.68". Then fired the pc'd loads.

3.2 gr. TG, lubed-2.37", 696 fps...pc'd-1.26", 729 fps
3.4 gr. TG, lubed-1.80", 734 fps...pc'd-1.67", 769 fps
3.6 gr. TG, lubed-2.89", 760 fps...pc'd-2.18", 788 fps
3.8 gr. TG, lubed-2.74", 801 fps...pc'd-1.68", 826 fps

Does this prove anything? Heck no, just a little more data. These all were only 6 shot groups also. The BAC lubed group using 3.6 gr. of TG is suspect because one shot opened the group from 1.14" to 2.89"!! Lube purge maybe?