Oregon Trail Laser-Cast bullets, Brinell Hardness and leading in barrel?

[MCMXI]

So a few months back I bought 2000 Oregon Trail Laser-Cast 200 grain RNFP bullets primarily to shoot in a pair of USFA Rodeos in .45 Colt at or below the SAAMI rated pressure of 15,000 CUP. After reading some information on the Missouri Bullet Company web page about Brinell Hardness (BHN) and case pressure, specifically ...

"Lead is a soft metal. Its hardness is expressed on a standard scale, called the Brinell Hardness Number (BHN.) The BHN of the bullet interacts with the pressure generated by the burning powder. The mechanism of this involves the effect of the generation of thousands of pounds per square inch of pressure which causes the base of the bullet to expand, or “obdurate”. Properly obdurated, the base will have expanded beyond its original diameter which has the effect of “sealing the bore” against the explosive pressure of the gases burning behind it. Properly sealed, and working in conjunction with the lubricant in the lube groove, the bullet will thus not allow gases to escape forward from around the base of the bullets, which prevents it from shaving lead from the bullet body and forcing it into the bore grooves (otherwise known as “leading”.)

This failure to obdurate (“seal the bore against onrushing gases”) causes leading which is a chore to clean and is a major obstacle to accuracy.

An optimally hard lead bullet is simply one which obdurates at a given pressure sufficiently to seal the bore against the gases which would otherwise “cut through” the soft lead (called “gas-cutting”, forcing molten lead into your rifling. A bullet which is too hard won't obdurate and seal the bore, because the gas pressure is insufficient to expand the base of the bullet. A bullet which is too soft at a given pressure will experience excessive base expansion and vaporization of the lead, causing leading.

There is a formula for optimal bullet hardness which is simple and it is worth knowing:

Optimum BHN = CUPS/(1422*.90)

The CUPS of your reloads is published in the reloading manuals. Take a typical .45 ACP load, using a 200-grain LSWC bullet – 5.0 grains of Bullseye. This load develops 900 FPS and is in common use among IPSC and IDPA gunners. The reloading manual shows that the pressure generated by this load is 20,000 CUPS. So, the formula for optimal bullet hardness is
20,000 / 1279.8 = 15.62

There it is! For this application – shooting a 200-grain LSWC at 900 FPS requires that you use a bullet with a BHN of 16 to 18 (round upwards a couple of BHN points for flexibility.)


... I called Oregon Trail to find out the BHN of their bullets. I was told that the OT bullets have a BHN of 24!! So if you put 24 into the equation above, the pressure rating for their bullets (to obdurate) is about 30,000 CUP!! If you consider a typical SAA .45 Colt loading from Lyman's 49th edition of 7.4 to 8.3 grains resulting in 928 to 1020 fps and 10,200 to 13,000 CUP respectively, the MBC's equation would indicate that Oregon Trail bullets wouldn't be suited to CAS type loads since at less than 15,000 CUP, they're not even half way to the "optimum" pressure.

So here's the dilemma, given that the OT bullets are on the hard side, I decided to load them for a Ruger Redhawk and Marlin 1894. I made up some hotter loads with 10.5* and 11.0* grains of W231 still under 25,000 CUP (easily safe for the Redhawk and safe for the Marlin) and went to the range. To my horror, the leading in the Ruger was SIGNIFICANT!! I didn't shoot them in the Marlin. So what's going on? Is it that they're still not moving fast enough (not enough pressure) or they're moving too fast at 1250 to 1300 fps. When I called and spoke to a non-technical person at OT today, she told me that their recommended load for W231 results in 787 to 913 fps.

So who's blowing smoke? If OT's bullets are BHN 24 AND MBC's equation is right, how can OT's bullets obdurate in a SAA and how can leading occur in the Ruger.

I'm really frustrated so ANY help would be much appreciated.

Thanks.


** CAUTION: These loads are NOT intended for original SAA revolvers or their clones.

 

[Old Fuff]

Get some .454 to .458 pure lead balls (as used in muzzle loaders) and drive them through your chamber throats and the bore with a close-fitting wood dowel. Then measure the diameters. The chamber throats should be .0005" to .0002" larger then the bore. If this is the case the bullet doesn't have to obdurate to seal in the bore. If the chamber throats are substantially smaller then the bore the bullets will be swaged down as they pass through the throats and enter the bore undersized. Most likely leading will occur, and you may get poor accuracy. Contrary to what some think, the bullets should be sized to match the chamber throats, not the bore – providing that the chamber throats are the correct size in relationship to the bore..

 

[Lone_Gunman]

I have loaded and shot hundreds of Oregon Trail bullets. I use them in cowboy style guns. I bought their reloading manual, and pretty much just load mid range cartridges. I have never experienced leading.

 

[MCMXI]

Old Fuff, now you're scaring me!! Do you really mean 0.0002 to 0.0005 inches? I have a Mitutoyo micrometer accurate to 0.00004 inches (0.001mm) but I'm used to 0.001 inch accuracy when it comes to firearms and ammuntion. Anyway, how much force is required to bash a .454 - .458 lead ball through a .45 Colt chamber and barrel? This will come to no good since I'll probably discover that my newly acquired revolver has six different sized chambers/throats, none of which match the barrel!! From what I can gather, I'm screwed IF the cylinder chamber throats are SMALLER than the barrel ... I suppose surgery would be the only option ... for the Ruger, not for me!!

Lone_Gunman, so how does your lack of leading tie into the BHN of the OT bullets (24) and MBC's equation above. Is is that your cylinder chamber throats are indeed as Old Fuff stated, 0.0005 to 0.0002 inches larger than the barrel or is the BHN of the OT bullets a lot less than the stated 24? Or is it due to something else?

Thanks.

 

[MMCSRET]

I experienced this "misfit" situation with a Ruger NMBH 45/45 convertible. 12 chambers, 8 different throat sizes ranging from .443 to .451. I called Brownells and ordered the cylinder reaming tooling and took them all out to .4515. Fantastic improvement in group size and elimination of leading from my cast bullets of air cooled WW's.

 

[Old Fuff]

1858:

Calm yourself...

Anyway, how much force is required to bash a .454 - .458 lead ball through a .45 Colt chamber and barrel?

Very little: I specified a round ball, made of soft lead, as used in muzzleloaders. Only a small surface of the circumference touches the throat or bore. Start with the smaller size, and if it’s too small go to the larger one. Say the throats run from .448” to .452”. The smaller ball will only be shaving .003” per side in a band about 3/16” wide at most. There is no way a soft (pure lead) ball is going to distort a chamber throat or barrel bore no matter how hard you pound.

However you are right. That should be .0015" to .002", and I stand corrected.

 

[Beagle-zebub]

1858, having the chamber throats opened up to perfect spec (.4525) is inexpensive, easy, and common--Ruger .45 cylinders are notorious for being both tight and even mis-shapen.

This guy charges $30 to do it, plus $9 shipping and handling. I'd google around, but my recollection was that he has a suitable reputation.

Just be glad you aren't fooling with a Colt SAA--their throats are often too big, which is why there are so many sizes of .45 caliber bullets.

 

[dardascastbullets]

Agree on the slugging of the barrel(s). To prevent leading one must have a properly fitting bullet. If it is on the small side then leading will become evident. The idea of the lead balls is a great one and easy to do. Be very careful when miking the ball - it has to be a true measurement or you will end up with an erroneous reading. Then specify your bullet diameter accordingly the next time you order your cast bullets. You will then realize success next time at the range!

Good luck!

 

[MCMXI]

There is no way a soft (pure lead) ball is going to distort a chamber throat or barrel bore no matter how hard you pound.

I wasn't worried about that ... I'm more worried about discovering that my Redhawk isn't the perfect little beast I thought it was. Something's seriously screwed up if I have to ream the cylinders on a brand new $650 Ruger Redhawk. However, I could understand if it's merely an optional "upgrade" in that it shoots fine (well within spec) from the factory but for the discerning user trying to eek out that extra little bit of accuracy or lead free performance it's worth ordering a cylinder reamer. I haven't shot at a paper target yet so I can't speak to the accuracy but the lead in the barrel sure is annoying.

So basically I need to order some lead balls but I'm still left wondering about the OT bullets and BHN.

MMCSRET, I found the reamer that you're referring to on Brownell's web site ...

http://www.brownells.com/aspx/ns/store/productdetail.aspx?p=7700#specs

Did you "slug" the bore as Old Fuff described before AND after to determine the dimensions?

 

[Old Fuff]

Ruger used to have a reputation for too-small throats, but of late they are said to be doing better. I have no idea what you might find in a USFA Rodeo, but a handfull of lead balls and a short length of wood dowel is a lot cheaper then buying a reamer set-up. If the throats are larger then the reamer you've wasted your money.

Unless you plan to go into the throat reaming business I would suggest that you slug the chambers and bore and see where you're at. If the throats were either too large or small I would send the cylinder (or whole gun if they insisted) back to the gunmaker for correction on their dime.

As a general rule, if you get excessive leading with moderate loads the cause is more likely to be a mismatch between the cylinder throats/bore diameters then the alloy/hardness of the bullets.

 

[MCMXI]

Beagle-zebub, thanks for the link ... I just checked it out and he seems like a knowledgeable individual. I was interested by the FAQ particularly ...

"Which Rugers are undersized?
Every gun is a law unto itself. I can say which guns I see the most of, and in what calibers. Far and away Ruger's make up most of my work. Of the Rugers, 90% of them would be .45's. Most new models, as well as some old models. Both blue and stainless.

Which S&W's are undersized?
As far as S&W goes, the stainless steel .44's seem to always be undersized. Some of the newer .45's as well.

Looks like I might be sending him a Ruger AND a S&W cylinder ... thank goodness he gives a discount on the second one!!

Now I'm wondering if my Colt Python cylinder needs to take a vacation too! It NEVER ends.

 

[MCMXI]

I have no idea what you might find in a USFA Rodeo, but a handfull of lead balls and a short length of wood dowel is a lot cheaper then buying a reamer set-up.

I don't know about the throats in the USFA Rodeos but the cylinder chambers look perfect and a lot better than the Ruger chambers. Since I don't plan on getting into the reaming business I doubt that I'd order a reamer. I'd most likely send one or more cylinders off to the cylindersmith or similar. He does say on his web page that he checks the cylinders and if they don't need reaming he only charges for shipping back so that's a cheap option too. At the end of the day, $40 per revolver isn't much to pay but it sure would be nice if companies such as Ruger got it right at the factory.

 

[MCMXI]

So doesn't anyone have any comments on the discrepancy between the BHN of 24 for Oregon Trail bullets (and their load data for W231) and the equation for "optimum" BHN from Missouri Bullet Company?

 

[Old Fuff]

If I understand correctly, you haven't yet shot some of the harder Oregon Trail bullets through the two USFA Rodeo revolvers yet. While I still recommend that you slug both cylinders and barrels, I would also suggest that you make up some modest loads and try them out. If the chamber throat and barrel dimensions are correct, and (something I failed to mention before) the bore and chambers are concentric when the cylinder is locked by the cylinder bolt, you may be in for a pleasant surprise. When the above is true, hard bullets are less likely to lead the bore then soft ones. They are also more accurate because torque is less likely to cause them to skid in the rifling.

Never forget… you can’t solve a problem until you can correctly define it.

 

[Old Fuff]

So doesn't anyone have any comments on the discrepancy between the BHN of 24 for Oregon Trail bullets (and their load data for W231) and the equation for "optimum" BHN from Missouri Bullet Company?

Sure, two different companies with different perspectives. Factory lead bullets are usually swaged out of soft lead wire. At low velocities they can be very accurate. If the dimensions we have discussed are right these bullets seldom cause a leading problem. Run up the loads and they well lead like crazy.

Hard (cast) lead bullets don't tend to lead either, either with modest or hot loads, if the cylinder throats, barrel bore and bullet diameter are all what they should be. If or when that's true I think that "Optimum BHN" is a solution looking for a problem.

 

[1858rem]

is the throat part of the actuall cylinder or is it the same as the forcing cone? i am still getting leading using lla and straight ww air cooled, 45 colt 1858 remington conversion loader anywhere between 650-940fps, i have tried pure lead 50/50 and straight ww,ww lead least, but at 6000-13000 cup that ought not matter much

 

[Canuck-IL]

An 89 cent oak dowel and a bag of #8 fishing sinkers will define a lot of your issues.

I regularly shoot Oregon Trail and other locally produced hardcast at Bullseye velocity and never have a leading problem (45acp).
/Bryan

 

[MCMXI]

If I understand correctly, you haven't yet shot some of the harder Oregon Trail bullets through the two USFA Rodeo revolvers yet.

Correct! I'll load up some of the OT bullets with 6.0 grains of Trail Boss powder and try them in the Rodeos this weekend. I did try that exact load in the Marlin '94 and don't remember any lead in the barrel during cleaning. However, I was already planning on sending the rifle back to Marlin to have the barrel replaced so I may not have been looking as hard as I could have.

I found some of the musket balls that you're referring to in .454 and .457 for about $12/100.

When I shot the Ruger a few weeks ago, I shot some 231 loads (10.5 and 11.0 grains) and some H110 loads that were quite a bit hotter but I didn't see any significant leading at that time. That's why I thought it might be the OT bullets. I wondered if the H110 loads removed any lead left by the OT loads since I shot the H110 loads last.

is the throat part of the actuall cylinder or is it the same as the forcing cone?

Each chamber in the cylinder has a throat and the barrel has a forcing cone.


Canuck, thanks for the tip ...

 

[nicholst55]

Commercial bullet casters cast their bullets hard - generally too hard - for probably 85% of handgun applications. They do that because most reloaders think that harder is better; and because hard bullets resist deformation while being handled by the UPS-trained apes better than softer alloys do. That's the same reason they use the hard crayon bullet lube - because it doesn't fall off during shipment.

That said, a lot of shooters use Oregon Trail bullets (and those from other commercial casters) in relatively mild loads with general satisfaction. When shooting cast bullets in a revolver, you want them to be throat diameter, or as close as possible. I've got an S&W M25-5 with throats that run .457", and it shoots .454" cast bullets reasonably well.

You also want your throats to be at least the same diameter as your bore, or just slightly larger. Most modern .45 Colt revolvers have bores that run right at .452"; throats should ideally run from .452-.453" for best cast bullet accuracy. With a setup like that, I shoot .452" cast bullets.

First thing I would do is to measure my chamber throats, and then my bore. If a cast .452" bullet will push through all of your throats with mild pressure, you're golden. If they fall through, you'll need to measure the throats and see just how large they are. If they're not uniform, same deal - and then have them reamed to a uniform size.

Several commercial bullet casters offer bullets in different diameters for a given caliber - most offer .45 Colt bullets in both .452" and .454" diameters. Buy the size that fits best, but be sure to measure a few to insure that they're the stated diameter.

Good luck!

 

[MMCSRET]

1858: yes, I slug just about everything I own. I shoot cast bullets in a lot of handguns and rifles.

 

[Mal H]

1858 - first of all a small spelling point should be made. MBC used the term "obdurate" which is usually applied only to humans (and most of my dogs). It means they are stubborn and unwilling to change. The proper word is "obturate" which means to seal. Just thought I'd throw that in for future reference.

So doesn't anyone have any comments on the discrepancy between the BHN of 24 for Oregon Trail bullets (and their load data for W231) and the equation for "optimum" BHN from Missouri Bullet Company?

I can't scientifically explain the discrepancy, but from experience, I am somewhat leery of any "formula" which uses an unexplained constant. What is the factor 1422, and why use only 90 percent of it? I have a feeling that formula, however it was contrived, might fall apart when the BHN of a bullet goes beyond a certain range. A BHN of 24, as you know, is very hard for lead bullets. The formula may not come close to predicting the proper obturation range for bullets that hard.

According to OT's own metallurgist, Dennis Marshall, scientific research has found that for lead alloys the yield strength is about 480 times the BHN. So for their bullets with a BHN of 24, the bullet base will start to obturate at about 12,000 PSI. (PSI is so much more precise than the old CUPS (copper units of pressure).)

Now, to your specific case using W231 and the 200 gr LRNFP's. Those loads are well over the recommended min/max of 6.5 gr / 7.9 gr. There may be something else that is causing the gross leading problem. Since the pressure would become rapidly excessive from a fast powder like W231 right at the forcing cone and the start of the rifling that you might be getting lead cutting before the bullet even has a chance to obturate. That's a SWAG.

If you want high pressure/high velocity loads, use a slower powder such as H110/W296, 2400, etc. IOW, don't push the lead envelope, so to speak, with a bunch of a fast powder, at least not in a revolver. I think the results might be different using heavy loads of fast powders in an integral chamber/barrel such as in a semiauto.

 

[MCMXI]

1858 - first of all a small spelling point should be made. MBC used the term "obdurate" which is usually applied only to humans (and most of my dogs). It means they are stubborn and unwilling to change. The proper word is "obturate" which means to seal. Just thought I'd throw that in for future reference.

I pointed that out a few months ago on a thread ... can't find it now but it didn't get a response so I was planning on leaving it alone.

You make some really good points and I think I need to do a bunch of different things before I have this "problem" solved.

If a cast .452" bullet will push through all of your throats with mild pressure, you're golden. If they fall through, you'll need to measure the throats and see just how large they are. If they're not uniform, same deal - and then have them reamed to a uniform size.

So I measured some of the 200 grain bullets from Oregon Trail and the OD is 0.4529" (I measured seven and they all were this size). None of them pushed easily through the cylinders ... in fact, the only one I "pushed" through by tapping with a mallet (using a plastic dowel) measured 0.4526" after exiting. I then "tapped" a bullet through the barrel and it measured 0.4511", 0.4513" and 0.4520" depending on where I measured it (six lands in the Ruger barrel). I'll tap a few more bullets through the barrel and remaining chambers this weekend.

Based solely on the one bullet I tapped through the cylinder and the one I tapped through the barrel, the barrel is 0.4515" (average of three measurements) and the cylinder throat is 0.4526" which is right where it should be. I realize that I need to do a lot more measuring but I'm encouraged by my first attempt.

Since the OT bullets measured 0.453" rather than the stated 0.452", combined with the hot 231 load with the fast powder burn rate as mentioned by Mal H, maybe that's the problem. The 231 loads are safe in the Ruger in terms of maximum pressure but perhaps not ideally suited to the size and type of bullet.

I want to thank everyone that posted since I've learned a lot from your comments. I had no idea about "slugging" the cylinder and bore, matching the bullet size to the throat etc. This has been and continues to be very enlightening.

Thanks.

 

[243winxb]

Obturate

http://en.wikipedia.org/wiki/Obturate The bullets must have tin in them or they lead. Could it be they are using less tin now because of the price? While antimony is used to harden the bullet, the mixture of tin is critical, for while antimony mixes with lead in its molten state, it will not remain mixed when it solidifies. If tin were not added, we would have pure antimony crystals surrounded by pure lead. A bullet of this type , while it feels hard , would certainly lead the bore and eliminate all potential for accuracy. In a lead-tin-antimony mixture, the antimony crystals will be present just the same, but they will be imbedded in a lead-tin mixutre. As the bullet cools the tin will form around the antimony-lead keeping your bullets from* leading the bore.

 

[MCMXI]

243winxb, I have no idea what Oregon Trail is doing with their bullets but I did manage to run 18 bullets through all six chambers (three each) and three bullets through the bore.

The first thing I noticed is how consistent (in diameter) the Oregon Trail bullets are. The average diameter (of 21 bullets measured) was 0.4530" with a standard deviation of 0.00008" ... impressive!

I used a Mitutoyo micrometer for all measurements (0 - 25mm model) with a resolution of 0.001mm (1 micron) = 0.00004". If you look at the data below, the average chamber throat diameters as determined by three bullets per chamber were ...

0.4525"
0.4525"
0.4525"
0.4526"
0.4526"
0.4526"

... and the average bore diameter of three bullets each of which was measured in three places 60 degrees apart (six grooves in barrel) was ...

0.4517"
0.4519"
0.4515"

So what do I know for sure? First off, the cylinder throats are LARGER than the bore and in fact, they're at the size that www.cylindersmith.com would ream them to if they were undersized. I'm not worried about the difference between chambers 1,2,3 and 4,5,6 unless someone convinces me otherwise. Second, the average of the average bores measurement is 0.4517" and I'll admit that measuring the bullet after it's been "rammed" through the bore is more difficult (and probably more prone to error by an amateur like myself). That said, 0.4525" is 0.0008" larger than the bore size and I'm not sure if this is a problem since Old Fuff mentioned 0.0002" to 0.0005" over the bore size is ideal. Anyway, I don't see any way to change that short of reaming the bore but that seems excessive to say the least.

At the end of the day, I'm now happy that my new Ruger Redhawk is "within spec" and won't have to go under the knife. That now brings me back to my original question about leading. It would seem that I have some experimenting to do with W231, H110 and Trail Boss. It's such a pity that 10.5 to 11.0 grains of powder causes leading with the OT 200 grain bullet since it's such a great load to shoot.

Thanks again to everyone.

 

[Old Fuff]

The Old Fuff goofed. Seldom happens of course, but does happen.

Got carried away on the keyboard and made too many zeros. 0 0 0 0.

What he met to say was .0015" to .002"

Your chamber throats v. bore diameter dimensions are dead on perfect.

Make up some moderate "cowboy" loads and I think you'll have excellent accuracy with little or no leading.

As a side note: Cap & ball revolvers are usually loaded with pure lead balls backed by low pressure black powder, which results in velocities below 1000FPS. (usually well below). You get a lot of fouling but seldom any leading. Somewhere there is a message there.