Relation between ploygonal barrel fouling Vs Brinell Hardness

[energizer]

Is there any relationship between polygonal barrel fouling vs Brinnell hardness scale?

I understand that a Glock poly barrel is different than a CZ82 poly barrel. I understand that the Glock barrel captures more lead than others. Anything I need to know more? Please elaborate. I would be primarily be more interested in using lead bullets in a CZ82 barrel rather than a Glock barrel.

Is there any recommended Brinnell hardness of the bullet recommended for any one of them to cause minimal fouling?

Thanks.

[ar15barrels]

The FIT of the bullet is more important than the hardness.
If you have a properly fitting bullet with enough hardness to stay together at the velocity you are using, they generally won't foul.
It's when they are too soft for the velocity (regardless of rifling type) or when they are too small for the barrel that they will foul the barrel.

[energizer]

Thanks ar15barrles, so does it mean that bullet manufacturer should provide that data?

For example I'm using 93gn 9x18 MAK bullets with BHN 18. What velocity I should choose in order to minimize fouling in a cz82 barrel?

Are there any other variables that come into play?

Thanks.

[ar15barrels]

Thanks ar15barrles, so does it mean that bullet manufacturer should provide that data?

For example I'm using 93gn 9x18 MAK bullets with BHN 18. What velocity I should choose in order to minimize fouling in a cz82 barrel?

Are there any other variables that come into play?

Thanks.

Experience will teach you how hard you need to be to not foul, but bullet diameter should be 0.001" oversized of the effectice groove diameter first before you worry about hardness.
Get/make a hardness tester so you can take your own measurements.

[Carcassonne]

Is there any relationship between polygonal barrel fouling vs Brinnell hardness scale?

I understand that a Glock poly barrel is different than a CZ82 poly barrel. I understand that the Glock barrel captures more lead than others. Anything I need to know more? Please elaborate. I would be primarily be more interested in using lead bullets in a CZ82 barrel rather than a Glock barrel.

Is there any recommended Brinnell hardness of the bullet recommended for any one of them to cause minimal fouling?

Thanks.

.

1) Bullet hardness makes a difference in fouling in all types of barrels and rifling.

2) Generally the softer the lead, the more fouling.

3) Handgun test conducted many years ago (1950s?) show that accuracy isn't necessarily effected by fouling. Some lead bullets that fouled the barrel were more accurate than lead bullets that didn't foul the barrel.

4) Fouling is caused be two things: Shear and friction. (1) When a bullet is accelerated (forced) against the grooves faster than the shear strength the lead can withstand, the lands of the bullet strip off and cause fouling (accuracy goes down). Heavier bullets need to be accelerated slower than lighter bullets because the moment of inertia is greater with heavier bullets. (2a) If the chamber pressure is too high, the bullet is squashed against the side walls of the bore increasing friction causing leading. (2b) If the bullet is traveling too fast (near the muzzle of the barrel) it could create more friction and fouling. I think heat caused be the friction weakens/softens the lead or copper coating, which gets deposited on the bore.

(Polygonal rifling or semi-polygonal (Glock) rifling may change the shear vector, and thus cause more leading/fouling, but it seams to me that moving the shear vector towards the bullets axis would increase the shear strength. - I didn't get that far in engineering )

5) My opinion is that harder is better. When in doubt, go harder. I water quench all my bullets. Most are straight wheel weights with a little tin or Hardball 92-8-2 which gives my 18+ BHN. If I am loading light 38 special or 45ACP, I will cut those two with 30-40% pure lead which brings it down to 10-12 BHN.

Look at page 2 of this Lee PDF: http://leeprecision.com/cgi-data/instruct/90924.pdf
It shows the relationship between lead hardness and psi strength. Supposedly the optimum accuracy is achieved when the max chamber pressure is 10% under the maximum psi strength of the bullet.


Also read this site: http://www.lasc.us/CastBulletNotes.htm

... and visit www.castboolits.com



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[energizer]

Carcassonne, thanks for sharing this information. This is indeed helpful.

[23's Dad]

Find your happy place

.

1) Bullet hardness makes a difference in fouling in all types of barrels and rifling.

5) My opinion is that harder is better. When in doubt, go harder. I water quench all my bullets. Most are straight wheel weights with a little tin or Hardball 92-8-2 which gives my 18+ BHN. If I am loading light 38 special or 45ACP, I will cut those two with 30-40% pure lead which brings it down to 10-12 BHN.


Also read this site: http://www.lasc.us/CastBulletNotes.htm

.

Interestingly enough, the cited reference has a free e-book on this topic. Take a read. Specifically chapter 3. You'll see the author's opinion on hardness is a bit different.

I shoot lead bullets (BHN in the 12-16) in my Glocks. I keep my loads at reasonable lead velocities, and I don't shoot more that a couple of hundred without cleaning. Personally, I haven't had any leading problems. Your loads, barrels, and velocities will be different.

Shoot 10-20, inspect your bore, shoot some more, re-inspect, shoot some more, clean & observe what comes out. You'll find out if your barrel/load is compatible or not.

[Carcassonne]

Interestingly enough, the cited reference has a free e-book on this topic. Take a read. Specifically chapter 3. You'll see the author's opinion on hardness is a bit different.

I use to monkey around with bullet hardness, different alloys, and lubes, but I finally gave up and decided to just cast harder bullets after noticing that the harder bullets leaded less than the softer bullets in almost everything I shot. It became too much of a pain to keep track of the performance of all my different molds, guns, and powders. I am not that obsessive compulsive. The only reason why I cut my 38 special and 45ACP lead alloy is to save money. Lead wheel weights, which use to be free, are illegal in California. Now I have to buy lead alloy somewhere else.




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[justMike]

Okay, but how many sides on these polygonal barrels, and what is the proper way to slug them for size if they are an odd number sided polygon? Anyone have info on these aspects of the barrels mentioned?

[energizer]

justMike, you can easily find the number of groves by researching about your firearm.

I don't know how odd sided polygons play role in this math. Maybe another senior and experienced guys can help us out.

For my barrel I found this http://www.cz82.com/wp/?page_id=36

It says "CZ-USA has stated to us that it is OK to use lead bullets in the barrel of the CZ-82’s polygonal rifling. They recommend that the barrel be cleaned and de-leaded prior to the use of copper plated ammunition, as residual lead in the barrel may decrease the bore diameter slightly and cause increased pressures."

[RUM]

I did a LOT of testing to come up with the load that I shoot in a Glock 23 and ended up with 5 parts lead -1 part monotype ratio at 975 fps.
I can soot about 200 rounds until it starts getting leading at the muzzle.
A few stroke with a stainless brush and it is gone.