The .455 Webley has a maximum operating pressure (sample average) of 12,700 psi, whereas .45 ACP may run up to 19,900 psi. This means that when firing your imported surplus Webley, commonly modified to fire .45 ACP for the US market, every time you pull the trigger, you're re-proofing the gun! Marks I through III of earlier Webley service revolvers were proofed only for black powder. While many converted Mk IV and later .455 Webley revolvers have survived repeated firing of .45 ACP ammunition, such treatment is equivalent to an accelerated endurance test, feeding the revolver a steady diet of proof loads.
Cylinder throats of all original Webley revolvers I have measured were tighter than barrel groove diameter. Colts and S&Ws, often have very large cylinder throats of .457-.459” with barrel groove diameters being .455-.457”. Forcing oversized bullets into tight cylinder throats increases chamber pressure dangerously, PARTICULARLY when bullets are full metal jacketed or cast hard! Safe results in Webley revolvers require SOFT lead bullets not exceeding 10 BHN, sized to fit the cylinder throats. Bullet weights from 230-270 grains are recommended to shoot to point of aim with fixed sights. Ammunition destined for “shaved” .45 ACP revolvers be assembled into .45 Auto-Rim cases for positive identification. Loads developed in stronger Colt and S&W .455 revolvers using larger bullet diameters and producing velocities over 700 fps should NEVER be fired in any Webley top-break revolvers!
Limit revolver velocity of 270-grain bullets to 600 fps and 230 grain ones to 700 fps by using 3.0-3.5 grains of Bullseye or 4.5-5.0 grains of Unique. You can determine safe charges with other powders in “shaved” .45 ACP Webleys or unaltered .455 revolvers using the 0.88” length .455 Colt cases by adhering to the “start” load charges listed for .45 ACP using #452374 in the Lyman Cast Bullet Handbook, 4th Edition (2010) on p.278, which do not exceed 13,000 cup. Reduce these charges by 10% either for heavier bullets or for use in shorter 0.76” Mk II cases, unless you are able to measure velocity of your revolver over a chronograph. Careful charge adjustment may be cautiously used to obtain uniform ballistics within the stated limits to compensate for a very large cylinder gap over 0.010”, which is very common in these revolvers.
I encountered a .004” range of diameters among the various chambers of my 1914-era Mk VI. Several chambers were smaller than barrel groove diameter. With soft hollow-based lead bullets using black powder, this allows the bullet to swage down passing through the chamber throat, getting the most energy from a small powder charge, and the hollow base expands up again as the bullet passes through the barrel forcing cone to engage the rifling. But, I repeat my warning that firing hard-cast or jacketed bullets larger than cylinder throat diameter, such as the M1911 .45 ACP service bullet, combined with fast-burning powders such as Bullseye, spike chamber pressure dangerously and should be avoided!
My Mk VI Webley revolver was a satisfying gunsmith’s adventure. While function and accuracy were very good for its type, it was plagued by occasional fliers and leading of its too-tight cylinder throats. Thorough cleaning and close examination revealed residual circumferential tool marks from its original manufacture, as well as deep pitting which had hidden for years under accumulated lead and encrusted carbon fouling. I sent the cylinder to DougGuy for honing. He first trued the throats to .4525” with an NM95 Borazon stone in his Sunnen hone to remove tight spots and enable close inspection, before cleaning up the worst damage in 0.001 increments, photographing the progress in stages. He explained:
“Uneven throats cause differences in pressure which make the gun recoil differently in the hands from shot to shot, and groups open accordingly… It is more important that throats are even than what size they are. You can always size bullets to fit the throats. Pitting makes the throat diameter larger, which will both vent off pressure before the bullet leaves the cylinder, and it will lead the cylinder any place where gas escapes… Honed to .4555" with the 500grit borazon stone, the throats…show a HUGE improvement… I can see a seal down low in the worst throats, and I stopped here because I do not want to polish out the pitting to the point where it is too shallow to hold lube, powder residue…better to leave it where the residue from firing will have a good chance at sealing…
“Here are the .4555" throats, and chambers, all polished up with an 800grit ball hone. A .4555” pin gage goes smoothly and evenly in all the throats, a .456" won't go in any of them. I am quite satisfied with this endeavor, and for sure want to know how well it shoots… At the very worst, if you have 2 chambers that are not shooting to the same point of impact as the others, two things can happen. You could mark them with empty 45 ACP brass that would remain in the chambers, or you could send the cylinder back and see what taking the throats to .4565" does for it. My thoughts for the best scenario are that you fire the gun enough times to fill in the remaining pits, and determine that it shoots pretty good and just roll with it… You should see a tremendous improvement right away. For once, the caliber REALLY IS what the bullets are, and you now truly have a 455 Webley!”
Soft Bullets and Mild Loads Are Best for Old Revolvers. I use a mixture of 50/50 plumber’s lead and backstop scrap with 2% tin added, approximating 30:1, about 9 BHN. Harder alloy is not needed, because velocities should not appreciably exceed 700 fps with 230-grain bullets or 600 fps with 265-270-grain ones.
Fiocchi brass uses small pistol primers while Hornady uses large pistol primers. Now you can buy new .455 MkII brass from Starline. If you want to load black powder in the pre-Boer War models, Reed's Custom Ammo sells Starline .45 Schofield cases modified to .455 Mk I Eley/Colt (0.88”) for $60 per 100. The rim diameter of Starline Schofield brass, while smaller than original .455 cases, is enough smaller in diameter to avoid rim interference which occurs when Hornady or Fiocchi Mk.II cases are used in adjacent chambers of the .45 ACP/.455 Kirst conversion in the Ruger Old Army and Pietta New Model Army Remington type revolvers. The worst case when using modified .45 Colt brass in a Webley is having to manually poke a case or two out of the chamber every once in a while.
After honing groups were about half those produced by the Webley in its original condition. It was easy to hit the 12” gong standing two-handed most of the time holding center-of-mass at 100 yards!
Proper bullet “fit” is essential for safety as well as accuracy. Because it is common to encounter .455 Webleys having “tight” cylinder throats as small as .450”, those inclined to hand load based only upon what they read, without MEASAURING their revolver, may assemble ammunition with hard, oversized bullets which dangerously spike pressure. Original MkII design soft, 10 BHN hollow-based bullets tolerate being squeezed through tight throats and will slug up again to take the rifling of a larger barrel.
A charge of 3.5 grains of Bullseye loaded with soft bullets cast from with Accurate molds 45-240H1 and 45-262H provide a useful approximation of original service velocity, with superior accuracy. While the Mk VI is not a target revolver, it easily meets or exceeds the traditional British service revolver accuracy criteria of One Inch Per Ten [yards], which defines practical handgun accuracy.
Table 1 - .455 Velocity Test Data
________________________Velocity (fps), Sd ________Kirst Ctg. Conversion
_____________________Webley Mk VI 6” Bbl._____Ruger ROA 7-1/2”
____________________Cylinder gap 0.018”_______Cylinder gap 0.004”
Kynoch K42 MkVI 265gr FMJ___537 fps, 29 Sd___________580 fps, 32 Sd
Handloads in Hornady .455 Mk II cases (0.77”) with Winchester LP primers
#452374 225-gr.RN 5.0 Unique____648 fps, 24 Sd____________716 fps, 11 Sd
MiHec 265-gr. Mk I 4.5 Unique_____538 fps, 24 Sd___________679 fps, 32 Sd
Accurate 45-262H 3.5 Bullseye_____622 fps, 6 Sd____________720 fps. 16 Sd
Handload in Starline Case modified to .455 Mk I (0.87”) by Reed’s Custom Ammo
Accurate 45-262H 3.5 Bullseye______546 fps, 16 Sd___________641 fps, 9 Sd
Column Means By Gun____________Webley 0.018” gap_______Ruger 0.004” gape
Pooled Avg. All Samples:___________578 fps________________667 fps
Velocity Gain from Webley__________0____________________+89 fps
Table -2 .455 Pressure Test Data
Submitted by Larry Gibson, Lake Havasu, AZ
T/C Contender .45 Colt 10” with strain gage interface to Oehler M43 Ballistic Test System
All test loads assembled in Starline .45 Schofield brass shortened to 0.87” length and rims turned, Winchester LP primer, weighed charges of 3.5 grains Alliant Bullseye throughout.
Acc. 45-240H (252 grs., 10 BHN) .452”, OAL 1.29” – 639 fps, 11,400 psi max.*
Only one shot recorded a high enough pressure to measure on the strain gage
Acc. 45-260H (269 grs., 10 BHN) .452”, OAL 1.30” – 648 fps, 14 Sd, ES 42, 11,800 psi, ES 900 psi
Acc. 45-290H (295 grs., 10 BHN) .452”, OAL 1.298” – 672 fps, 11 Sd, 32 ES, 12,600 psi, ES 1100 psi
Expected velocity drop in 6” barrel revolver estimated -100 to 150 fps, depending upon cylinder gap.
Cylinder throats of all original Webley revolvers I have measured were tighter than barrel groove diameter. Colts and S&Ws, often have very large cylinder throats of .457-.459” with barrel groove diameters being .455-.457”. Forcing oversized bullets into tight cylinder throats increases chamber pressure dangerously, PARTICULARLY when bullets are full metal jacketed or cast hard! Safe results in Webley revolvers require SOFT lead bullets not exceeding 10 BHN, sized to fit the cylinder throats. Bullet weights from 230-270 grains are recommended to shoot to point of aim with fixed sights. Ammunition destined for “shaved” .45 ACP revolvers be assembled into .45 Auto-Rim cases for positive identification. Loads developed in stronger Colt and S&W .455 revolvers using larger bullet diameters and producing velocities over 700 fps should NEVER be fired in any Webley top-break revolvers!
Limit revolver velocity of 270-grain bullets to 600 fps and 230 grain ones to 700 fps by using 3.0-3.5 grains of Bullseye or 4.5-5.0 grains of Unique. You can determine safe charges with other powders in “shaved” .45 ACP Webleys or unaltered .455 revolvers using the 0.88” length .455 Colt cases by adhering to the “start” load charges listed for .45 ACP using #452374 in the Lyman Cast Bullet Handbook, 4th Edition (2010) on p.278, which do not exceed 13,000 cup. Reduce these charges by 10% either for heavier bullets or for use in shorter 0.76” Mk II cases, unless you are able to measure velocity of your revolver over a chronograph. Careful charge adjustment may be cautiously used to obtain uniform ballistics within the stated limits to compensate for a very large cylinder gap over 0.010”, which is very common in these revolvers.
I encountered a .004” range of diameters among the various chambers of my 1914-era Mk VI. Several chambers were smaller than barrel groove diameter. With soft hollow-based lead bullets using black powder, this allows the bullet to swage down passing through the chamber throat, getting the most energy from a small powder charge, and the hollow base expands up again as the bullet passes through the barrel forcing cone to engage the rifling. But, I repeat my warning that firing hard-cast or jacketed bullets larger than cylinder throat diameter, such as the M1911 .45 ACP service bullet, combined with fast-burning powders such as Bullseye, spike chamber pressure dangerously and should be avoided!
My Mk VI Webley revolver was a satisfying gunsmith’s adventure. While function and accuracy were very good for its type, it was plagued by occasional fliers and leading of its too-tight cylinder throats. Thorough cleaning and close examination revealed residual circumferential tool marks from its original manufacture, as well as deep pitting which had hidden for years under accumulated lead and encrusted carbon fouling. I sent the cylinder to DougGuy for honing. He first trued the throats to .4525” with an NM95 Borazon stone in his Sunnen hone to remove tight spots and enable close inspection, before cleaning up the worst damage in 0.001 increments, photographing the progress in stages. He explained:
“Uneven throats cause differences in pressure which make the gun recoil differently in the hands from shot to shot, and groups open accordingly… It is more important that throats are even than what size they are. You can always size bullets to fit the throats. Pitting makes the throat diameter larger, which will both vent off pressure before the bullet leaves the cylinder, and it will lead the cylinder any place where gas escapes… Honed to .4555" with the 500grit borazon stone, the throats…show a HUGE improvement… I can see a seal down low in the worst throats, and I stopped here because I do not want to polish out the pitting to the point where it is too shallow to hold lube, powder residue…better to leave it where the residue from firing will have a good chance at sealing…
“Here are the .4555" throats, and chambers, all polished up with an 800grit ball hone. A .4555” pin gage goes smoothly and evenly in all the throats, a .456" won't go in any of them. I am quite satisfied with this endeavor, and for sure want to know how well it shoots… At the very worst, if you have 2 chambers that are not shooting to the same point of impact as the others, two things can happen. You could mark them with empty 45 ACP brass that would remain in the chambers, or you could send the cylinder back and see what taking the throats to .4565" does for it. My thoughts for the best scenario are that you fire the gun enough times to fill in the remaining pits, and determine that it shoots pretty good and just roll with it… You should see a tremendous improvement right away. For once, the caliber REALLY IS what the bullets are, and you now truly have a 455 Webley!”
Soft Bullets and Mild Loads Are Best for Old Revolvers. I use a mixture of 50/50 plumber’s lead and backstop scrap with 2% tin added, approximating 30:1, about 9 BHN. Harder alloy is not needed, because velocities should not appreciably exceed 700 fps with 230-grain bullets or 600 fps with 265-270-grain ones.
Fiocchi brass uses small pistol primers while Hornady uses large pistol primers. Now you can buy new .455 MkII brass from Starline. If you want to load black powder in the pre-Boer War models, Reed's Custom Ammo sells Starline .45 Schofield cases modified to .455 Mk I Eley/Colt (0.88”) for $60 per 100. The rim diameter of Starline Schofield brass, while smaller than original .455 cases, is enough smaller in diameter to avoid rim interference which occurs when Hornady or Fiocchi Mk.II cases are used in adjacent chambers of the .45 ACP/.455 Kirst conversion in the Ruger Old Army and Pietta New Model Army Remington type revolvers. The worst case when using modified .45 Colt brass in a Webley is having to manually poke a case or two out of the chamber every once in a while.
After honing groups were about half those produced by the Webley in its original condition. It was easy to hit the 12” gong standing two-handed most of the time holding center-of-mass at 100 yards!
Proper bullet “fit” is essential for safety as well as accuracy. Because it is common to encounter .455 Webleys having “tight” cylinder throats as small as .450”, those inclined to hand load based only upon what they read, without MEASAURING their revolver, may assemble ammunition with hard, oversized bullets which dangerously spike pressure. Original MkII design soft, 10 BHN hollow-based bullets tolerate being squeezed through tight throats and will slug up again to take the rifling of a larger barrel.
A charge of 3.5 grains of Bullseye loaded with soft bullets cast from with Accurate molds 45-240H1 and 45-262H provide a useful approximation of original service velocity, with superior accuracy. While the Mk VI is not a target revolver, it easily meets or exceeds the traditional British service revolver accuracy criteria of One Inch Per Ten [yards], which defines practical handgun accuracy.
Table 1 - .455 Velocity Test Data
________________________Velocity (fps), Sd ________Kirst Ctg. Conversion
_____________________Webley Mk VI 6” Bbl._____Ruger ROA 7-1/2”
____________________Cylinder gap 0.018”_______Cylinder gap 0.004”
Kynoch K42 MkVI 265gr FMJ___537 fps, 29 Sd___________580 fps, 32 Sd
Handloads in Hornady .455 Mk II cases (0.77”) with Winchester LP primers
#452374 225-gr.RN 5.0 Unique____648 fps, 24 Sd____________716 fps, 11 Sd
MiHec 265-gr. Mk I 4.5 Unique_____538 fps, 24 Sd___________679 fps, 32 Sd
Accurate 45-262H 3.5 Bullseye_____622 fps, 6 Sd____________720 fps. 16 Sd
Handload in Starline Case modified to .455 Mk I (0.87”) by Reed’s Custom Ammo
Accurate 45-262H 3.5 Bullseye______546 fps, 16 Sd___________641 fps, 9 Sd
Column Means By Gun____________Webley 0.018” gap_______Ruger 0.004” gape
Pooled Avg. All Samples:___________578 fps________________667 fps
Velocity Gain from Webley__________0____________________+89 fps
Table -2 .455 Pressure Test Data
Submitted by Larry Gibson, Lake Havasu, AZ
T/C Contender .45 Colt 10” with strain gage interface to Oehler M43 Ballistic Test System
All test loads assembled in Starline .45 Schofield brass shortened to 0.87” length and rims turned, Winchester LP primer, weighed charges of 3.5 grains Alliant Bullseye throughout.
Acc. 45-240H (252 grs., 10 BHN) .452”, OAL 1.29” – 639 fps, 11,400 psi max.*
Only one shot recorded a high enough pressure to measure on the strain gage
Acc. 45-260H (269 grs., 10 BHN) .452”, OAL 1.30” – 648 fps, 14 Sd, ES 42, 11,800 psi, ES 900 psi
Acc. 45-290H (295 grs., 10 BHN) .452”, OAL 1.298” – 672 fps, 11 Sd, 32 ES, 12,600 psi, ES 1100 psi
Expected velocity drop in 6” barrel revolver estimated -100 to 150 fps, depending upon cylinder gap.
