Max Velocity For Bare Lead Bullet
- Thread starter theDuck
- Start date
It's as much pressure as it is velocity that indicates the need for a gas check.
Which 45 cal? 45 Colt? 45-70? 458 Win Mag? 460 Wby Mag? What bullet weight?
In all likelihood if you kept pressure under 20 K psi, and MV under 1300 fps you'd be ok.
Which 45 cal? 45 Colt? 45-70? 458 Win Mag? 460 Wby Mag? What bullet weight?
In all likelihood if you kept pressure under 20 K psi, and MV under 1300 fps you'd be ok.
The bullet doesn't become molten but just galls like crazy. The lead will "stick" to the barrel but the momentum will cause the stuck section to tear off and remain on the inside of the barrel. When you clean leading out of a barrel it's usually flakes or chunks that have been ironed to the barrel, not melted looking bits. There might be a touch of actual melting, maybe a few molecules thick, but no observable melting without an electron microscope.
There is also a phenomenon called "gas cutting" which is not proven but has two theories I've read online. One is that the gas melts the back end of the bullet and leaves lead droplets in the barrel. This theory isn't easily possible based on physics and thermodynamics. The second and more widely supported is that the gas, if too high of a pressure, can shoot up the rifling grooves past the bullet and in doing so cuts into it and leaves pieces of lead in the bore as a result. A gas check is used to prevent this from happening and those who believe in the first theory say the higher melting point of copper/brass/aluminum prevents the lead from melting. Those who believe the second theory say the gas check seals the bore and because the copper/brass/aluminum is harder the gas cannot cut into it in the rifling grooves like it can with unprotected lead.
Different barrels will have different maximum velocities with the same bullets depending on twist rate and condition. This is assuming the bullets are sized to the bore (0.001" to 0.002" over groove diameter based on a bore slug, not measuring the muzzle with a caliper). If you have Marlin Micro-Groove rifling they are really picky with cast bullets. Some will shoot cast fine, some will require reduced velocity, and some will require greatly reduced velocity. My 44 mag Marlin for example leads and groups 24"+ at 50yds if I go above 1000fps with any hardness or any size of bullet. Other guys I've talked to with Micro-Groove barrels can shoot 1800fps with cast with no leading. Seems to be a barrel-by-barrel thing. Likewise rifles with really worn bores with shallow, worn down rifling and pits and rough spots will also run into problems at lower velocities than nice crisp bores. I have a number of surplus rifles with barrels ranging from spotless and new to barely shootable. As the bore gets worse the maximum velocity while being able to maintain any sort of accuracy and prevent leading drops. In my worst rifles I am around 1000fps if I want to shoot well at all. In good condition bores or new production civilian rifles I've pushed plain-base cast bullets up past 1400fps with no problems. With a gas check I've reached almost 1800fps (in a 308) but accuracy started to drop off so I stopped and went back.
One load I liked but I avoid because it uses so much lead and my supply is dwindling is a Lee 500gr .459" cast bullet, plain base, water quenched, pure WW, pan lubed, in a 45-70 pushed by H4895 to 1450fps. It's a spire-point design so I only use it in single-shots but I've punched through 14" poplar trees with it and it's quite accurate out to at least 50yds. I think it was around 2-3" which for me with my terrible eyes is pretty good.
There is also a phenomenon called "gas cutting" which is not proven but has two theories I've read online. One is that the gas melts the back end of the bullet and leaves lead droplets in the barrel. This theory isn't easily possible based on physics and thermodynamics. The second and more widely supported is that the gas, if too high of a pressure, can shoot up the rifling grooves past the bullet and in doing so cuts into it and leaves pieces of lead in the bore as a result. A gas check is used to prevent this from happening and those who believe in the first theory say the higher melting point of copper/brass/aluminum prevents the lead from melting. Those who believe the second theory say the gas check seals the bore and because the copper/brass/aluminum is harder the gas cannot cut into it in the rifling grooves like it can with unprotected lead.
Different barrels will have different maximum velocities with the same bullets depending on twist rate and condition. This is assuming the bullets are sized to the bore (0.001" to 0.002" over groove diameter based on a bore slug, not measuring the muzzle with a caliper). If you have Marlin Micro-Groove rifling they are really picky with cast bullets. Some will shoot cast fine, some will require reduced velocity, and some will require greatly reduced velocity. My 44 mag Marlin for example leads and groups 24"+ at 50yds if I go above 1000fps with any hardness or any size of bullet. Other guys I've talked to with Micro-Groove barrels can shoot 1800fps with cast with no leading. Seems to be a barrel-by-barrel thing. Likewise rifles with really worn bores with shallow, worn down rifling and pits and rough spots will also run into problems at lower velocities than nice crisp bores. I have a number of surplus rifles with barrels ranging from spotless and new to barely shootable. As the bore gets worse the maximum velocity while being able to maintain any sort of accuracy and prevent leading drops. In my worst rifles I am around 1000fps if I want to shoot well at all. In good condition bores or new production civilian rifles I've pushed plain-base cast bullets up past 1400fps with no problems. With a gas check I've reached almost 1800fps (in a 308) but accuracy started to drop off so I stopped and went back.
One load I liked but I avoid because it uses so much lead and my supply is dwindling is a Lee 500gr .459" cast bullet, plain base, water quenched, pure WW, pan lubed, in a 45-70 pushed by H4895 to 1450fps. It's a spire-point design so I only use it in single-shots but I've punched through 14" poplar trees with it and it's quite accurate out to at least 50yds. I think it was around 2-3" which for me with my terrible eyes is pretty good.
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A cast bullet loader can manipulate variuos aspects of his load combination. When a cAst bullet load fails to perform, it is usually one or a combination of component failures.
Over pressure/acceleration can deform the bullet base to the point of gas leakage between the bullet surface and the bore surface. This can cause the gasses to "wash" (so to speak) lead from the bullet bearing surface. This can cause a few issues. Such as erratic pressures that cause inaccuracies. A bullet that is damaged during the firing sequence can have gyroscopic instalilities due to moved/damaged material. Causing an imbalance, Yawing or tumbling.
The best cast bullet loads maintain a balance that allow a load to work. As you increase pressures, the weakest link will eventually surface.
If the expanding gasses leak past the bullet base, this can allow the lube to be sprayed ahead of the bullet as well. When the lube is not in the lube groove, it cannot offer the lubrication or bullet surface support.
I tend to doubt that combustion temperatures affect/cause much melting due to the extreamly short time frames of which these temps are imparted to the bullet base. You can pass your hand through a flame, and not get burnt if you keep it moving fast.(very low exposure time).
Pressure on the alloy, on the other hand, is a bit different story.
A full lube groove can offer allot of load enhancing benefits.
I shoot my 200 grain Lyman 311299 cast bullet at velocities as high as 2425fps. In my 308win cast rifle. At this speed and pressure, the components are just starting to yield. The accuracy is around 1-1/2 to 2" at 100 yards.
When I drop my pressures and velocity down to around 2350fps, my average group size improves noticably. I have had many groups well under an inch, and some around 1.25".
This load exhibits some great ballistic uniformity for cast! I have shot this load clear out to 900 yards. Only after 800 yards does the accuracy start to decay rapidly. I am not at home, so my records are not available at this time, but 1.5 to 2.5 MOA "ish" is the rule past 500 yards.
My alloy is 18 pounds wheel weight lead +8 feet of 50/50 lead/tin solder. Air cooled.
Bullet is sized to .310" and lubed with Lymans Super Moly.
Gas checks I have tested with my load combinations are brass,copper and aluminum.
As can be expected, my maximum velocities that can reached while maintaining decent accuracy, varies with the gas check material as well. Aluminum cant get me much past 1800fps before failing with this alloy.
Both Copper and Brass were able to reach the 2425fps level, but brass gas checked loads were more consistent on the chronygraph. But not by much.
Powder that is "PREFERRED" is IMR4831. This is not the typical powder associated with cast shooting, but more for jacketed bullets.
I dont feel most failures of a cast bullets base are caused by melting due to combustion temperature, but extrusion caused by the loads expanding gases surpassing the alloys physical elastic/compressible limit. (Surpassing the yield point of the alloy). The gasses will simply go to the point of least resistance, where ever on the bullet to bore surface that happens to be. Both the Pressure limits and the timing of the maximum pressures affect the bullets ability to accelerate without damaging the bullets alloy. A push rather than a kick, so to speak.
When I used the powders most commonly reccomended for cast bullets, as I approached near the maximum charges recomended for that powder, the accuracy would start to fall off. To be expected. The pressures were surpassing the bullet/lube/ and gas checks ability to seal the gases during the acceleration of the firing sequence.
Using another slower powder allowed me to achieve a higher velocity before the accuracy started to fail.
With IMR4831, I believe that the slower burning characteristics allowed the expanding gasses to apply the pressure over a longer burn period. Thus delaying the highest pressure point at a higher velocity. Less of an impact/g force imparted on the bullet base and the alloys yield point pressure. A softer-longer start/push.
To initiate an adquate pressure to get the IMR4831 to burn fully, I seated the bullets into the rifling firmly. With this technique, the rifle shoots great, and the bore stays suprisingly clean and free of powder residue.
In a nutshell, maximising your velocity with any lead based bullet will depend on your alloys yield point strength, and how fast and high the pressures are applied.
Fast burning powders will produce slower velocities at maximum pressures. A sharp kick so to speak.
Having the bullet sized .001-.002" larger than bore diameter will help seal the combustion gasses, and offer the accelerating bullet support to reduce any kind of bullet shape "slump".
Some bullet designs will shoot better in some barrels than others. The only way to know which one your rifle likes is to try them.
Shooting cast can be as easy or as challenging as you desire. Just have fun with it.
I hope this info was useful to someone.
Over pressure/acceleration can deform the bullet base to the point of gas leakage between the bullet surface and the bore surface. This can cause the gasses to "wash" (so to speak) lead from the bullet bearing surface. This can cause a few issues. Such as erratic pressures that cause inaccuracies. A bullet that is damaged during the firing sequence can have gyroscopic instalilities due to moved/damaged material. Causing an imbalance, Yawing or tumbling.
The best cast bullet loads maintain a balance that allow a load to work. As you increase pressures, the weakest link will eventually surface.
If the expanding gasses leak past the bullet base, this can allow the lube to be sprayed ahead of the bullet as well. When the lube is not in the lube groove, it cannot offer the lubrication or bullet surface support.
I tend to doubt that combustion temperatures affect/cause much melting due to the extreamly short time frames of which these temps are imparted to the bullet base. You can pass your hand through a flame, and not get burnt if you keep it moving fast.(very low exposure time).
Pressure on the alloy, on the other hand, is a bit different story.
A full lube groove can offer allot of load enhancing benefits.
I shoot my 200 grain Lyman 311299 cast bullet at velocities as high as 2425fps. In my 308win cast rifle. At this speed and pressure, the components are just starting to yield. The accuracy is around 1-1/2 to 2" at 100 yards.
When I drop my pressures and velocity down to around 2350fps, my average group size improves noticably. I have had many groups well under an inch, and some around 1.25".
This load exhibits some great ballistic uniformity for cast! I have shot this load clear out to 900 yards. Only after 800 yards does the accuracy start to decay rapidly. I am not at home, so my records are not available at this time, but 1.5 to 2.5 MOA "ish" is the rule past 500 yards.
My alloy is 18 pounds wheel weight lead +8 feet of 50/50 lead/tin solder. Air cooled.
Bullet is sized to .310" and lubed with Lymans Super Moly.
Gas checks I have tested with my load combinations are brass,copper and aluminum.
As can be expected, my maximum velocities that can reached while maintaining decent accuracy, varies with the gas check material as well. Aluminum cant get me much past 1800fps before failing with this alloy.
Both Copper and Brass were able to reach the 2425fps level, but brass gas checked loads were more consistent on the chronygraph. But not by much.
Powder that is "PREFERRED" is IMR4831. This is not the typical powder associated with cast shooting, but more for jacketed bullets.
I dont feel most failures of a cast bullets base are caused by melting due to combustion temperature, but extrusion caused by the loads expanding gases surpassing the alloys physical elastic/compressible limit. (Surpassing the yield point of the alloy). The gasses will simply go to the point of least resistance, where ever on the bullet to bore surface that happens to be. Both the Pressure limits and the timing of the maximum pressures affect the bullets ability to accelerate without damaging the bullets alloy. A push rather than a kick, so to speak.
When I used the powders most commonly reccomended for cast bullets, as I approached near the maximum charges recomended for that powder, the accuracy would start to fall off. To be expected. The pressures were surpassing the bullet/lube/ and gas checks ability to seal the gases during the acceleration of the firing sequence.
Using another slower powder allowed me to achieve a higher velocity before the accuracy started to fail.
With IMR4831, I believe that the slower burning characteristics allowed the expanding gasses to apply the pressure over a longer burn period. Thus delaying the highest pressure point at a higher velocity. Less of an impact/g force imparted on the bullet base and the alloys yield point pressure. A softer-longer start/push.
To initiate an adquate pressure to get the IMR4831 to burn fully, I seated the bullets into the rifling firmly. With this technique, the rifle shoots great, and the bore stays suprisingly clean and free of powder residue.
In a nutshell, maximising your velocity with any lead based bullet will depend on your alloys yield point strength, and how fast and high the pressures are applied.
Fast burning powders will produce slower velocities at maximum pressures. A sharp kick so to speak.
Having the bullet sized .001-.002" larger than bore diameter will help seal the combustion gasses, and offer the accelerating bullet support to reduce any kind of bullet shape "slump".
Some bullet designs will shoot better in some barrels than others. The only way to know which one your rifle likes is to try them.
Shooting cast can be as easy or as challenging as you desire. Just have fun with it.
I hope this info was useful to someone.
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- Location
- The Orion Arm
So jacketed bullets get around these considerations? How about copper plated ones (like Berry's)?
Copper is much harder than lead so can withstand higher pressures, velocities, and get abused more without any problems. Copper is also self lubricating under pressure; that's why copper plated or jacketed bullets don't need bullet lube but lead bullets do. That's also why you see a lot of copper and brass bushings in mechanical devices.
Plated bullets depend on the thickness of the plating. Berry's are fairly thinly plated and most sources say to use cast bullet data for them.
I've read reports of people getting jacketed velocities in 357 and 44 mag with Campro plated bullets because their plating is something like twice as thick as other brands like Berry's.
Copper "plated" bullets are designed to isolate the lead from the air during the fireing sequence. This reduces the chances of the shooter being exposed to lead inhalation/ingestion.
It stands to reason that the thicker the plating, the better the bullets resistance to pressures imposed on the base. Copper is a great material for bullets! Copper has dramtically changed what the potential of the bullet can achieve!
It stands to reason that the thicker the plating, the better the bullets resistance to pressures imposed on the base. Copper is a great material for bullets! Copper has dramtically changed what the potential of the bullet can achieve!
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Didn't read the long answers on this thread but my 2 coppers are that it depends on the hardness of the cast bullet and the size of the cast bullet... to shoot at higher velocity you want a medium hardness and a bullet that is oversized by at least 2 thou... you will have to slug your barrel to determine what that is.
- Location
- Ottawa origanally Muskoka
With no gas check the fastest you can shoot a cast lead bullet is arround the 1850fps mark. Gas checks allow you to surpass this and reach up to about 2400fps. These are practical acuracy limits not absolute limits.
For the 45-70gvt in question I would suggest you keep the velocity down arround 1500fps.
Size .001" to. .002" over bore and use lots of medium soft lube. SPG lube is a good starting place. Check the muzzle of your gun after a few shots. A greasy lube star should be pressent. If not then the lube is either too soft and is burning up, too hard and isn't melting out of the grooves of the bullet or there isn't enough of it. Of cource too much can lead to hydro shock with in the barrel and cause accuracy and barrel troubles. This is most offten incountered when the noses of the bullets have lube on them....so don't grease the noses.
For the 45-70gvt in question I would suggest you keep the velocity down arround 1500fps.
Size .001" to. .002" over bore and use lots of medium soft lube. SPG lube is a good starting place. Check the muzzle of your gun after a few shots. A greasy lube star should be pressent. If not then the lube is either too soft and is burning up, too hard and isn't melting out of the grooves of the bullet or there isn't enough of it. Of cource too much can lead to hydro shock with in the barrel and cause accuracy and barrel troubles. This is most offten incountered when the noses of the bullets have lube on them....so don't grease the noses.
Can you please explain to me what hydro shock is?
I lube the noses of my 311299's all the time, and they shoot tremendously out to distances described in this thread.
I am always willing to learn/concider other points of view.
I have experienced issues that is referred to as lube purging. This occurs on hotter days, where my lube is getting softer.
This tends to give me "fliers" occasionaly. By this the bullet will tend to hit outside the normal grouping by 3/4-1". For my shooting purposes, such as long range plate shooting, its no real big deal. It doesnt result in a significant miss.
If I were benchrest shooting for group, it may become an issue to control more.
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There is no good answer for that question. It depends on the alloy and the barrel, and the powder. Why Not got over 2000 fps in a flat base 9.3,mm bullet with no leading.
"hard" cast is not automatically better than softer bullets - it depends on the alloy. Antimony makes bullets stronger and harder, tin makes them harder but not necessarily stronger. A good alloy of lead/antimony/tin works best.
Bullets that are sized .001-.002" over groove diamter will be much less likely to lead. Barrels with less than perfect condition are also more likely to lead up.
Generally speaking I expect to get well over 1500 fps on a non-gas checked rifle bullet before i see leading but it depends on a lot of variables. If you start with a good fitting bullet your chances of success are much higher.
"hard" cast is not automatically better than softer bullets - it depends on the alloy. Antimony makes bullets stronger and harder, tin makes them harder but not necessarily stronger. A good alloy of lead/antimony/tin works best.
Bullets that are sized .001-.002" over groove diamter will be much less likely to lead. Barrels with less than perfect condition are also more likely to lead up.
Generally speaking I expect to get well over 1500 fps on a non-gas checked rifle bullet before i see leading but it depends on a lot of variables. If you start with a good fitting bullet your chances of success are much higher.
I've not heard of hydro shock from lubed bullet noses before - can you explain it please.
Bassmaster
CGN frequent flyer
- Location
- WMU 48 - Whitetail country
Lots of good info here......
hydro shock is also a new one on me....I usually wipe the residual lube from my cast stuff once the bullet is seated....inquiring minds
hydro shock is also a new one on me....I usually wipe the residual lube from my cast stuff once the bullet is seated....inquiring minds
