Minimum Pressure for obturation

[Silverseas]

I have been reading: Cast Bullet Alloys and Obturation By: Glen E. Fryxell and Heat Treating Lead/Antimony/Arsenic Alloys
By: Rick Kelter. I would like to create an alloy better suited to the bench rest shooting I have been doing with my 357 mag, Ruger Blackhawk, 6 1/2". Shooting at 50 yards for now..

The Formula 1440 X BHN is given to determine the minimum pressure that will cause obturation of the bullet. What I don't know how to find is what pressure my loads will produce at less then the maximum load given in the printed literature I have. Start loads in the Western Powders guide show the velocity but not the pressure. I have been shooting a Lee 358-150 RN using a variety of powders and loads, and now I want to standardize on Accurate #7 at about 9.5gr. So I would like to know the pressure curve in a bit more detail, and shown in PSI rather than CUP which is used in the Lyman Cast bullet handbook. Then I can tailor an alloy mix to get the BNH needed for obturation to occur.

Then I wonder how much higher then the obturation pressure can I go before the bullet cant take it. Testing and checking, right?
Does this make sense? or am I making it too complicated. My casting has gotten better in the last couple of years so I no longer have to scrape lead out of the barrel, but my groups are at best 3", and thats with a Burris 3-12x pistol scope. I am hoping to tighten those groups and get out to 100 yards.

thanks now for your help.
Steven

[Larry Gibson]

If your bullets fit the cylinder throats (tight push through fit) and the cylinder throats are as larger or larger than the groove diameter of the barrel them "obturation" is a non issue because your bullets will be swaged down.

"making it too complicated"

Yes.

If you want to shoot small groups at 100 yards with your revolver then cast harder bullets, cast the best bullets you can, use a good alloy, size to fit the throats, use a good known lube and use a uniform, consistent loading technique.

[vzerone]

.....but, but, but Elmer Keith didn't shoot a hard alloy. His favorite was 16 to 1 lead/tin. I'd say he shot pretty dang good.

[bullseye67]

Good evening,
I second what Larry said.
Shooting at steel silhouettes a hard'ish boolit, 2-3 thousands larger than the cylinder, was always more accurate with my S&W 44 mag. Didn't have a lot of success with "any" and I had/have quite a few 357 revolvers at 100 yards. One of those "bigger is better" things? (Just to qualify, what I expected as success and what others expect are quite often two very different results) One member used a 357 Maximum with J-words and could duplicate what the rest of us were doing with 44 magnums and cast boolits.
I would start with J-word bullets and when you have your version of success. Duplicate as much as possible with cast boolits. I suggest a RCBS 200gr or the LEE version with a gas check.
Good Luck with your adventure.....

[Silverseas]

I have a Lyman 358530 mold that casts a 190 gr RN at .360 which is just a tad larger then the cylinder throats. I will give that a try.

[runfiverun]

you know that 1440 whatever number?
forget it.
you could follow the rule or even shoot stuff at 75% of that number, and you'll get the same results your gonna get with some ww alloy or some 3/3 type alloy.
I will say a somewhat harder alloy will generally shoot a bit better.... depending on the shape of your boolit.

[Silverseas]

Thank, that helps simplify things for me. (A retirement goal of mine). I have some Lyman #2 from Rotometals, is that a good place to start?

[vzerone]

I'll have to agree with runfiverun. If you can't shoot accurately with softer alloys then you don't know what you are doing. Aside from shooint silhouette and big danger game like elephant and cape buffalo hard alloy doesn't have a wide range of application. I've knocked down silhouette with soft alloy and I certainly don't prefer hard alloy for my deer hunting. Again look back at what Elmer Keith did.

[quail4jake]

In most of what I load using a softer alloy has produced better results (except peppy rifle loads). I'm to the point of 40:1 (2.5% Sn) in low velocity handgun loads: .32 S&W, .38 S&W, .38 spl. wadcutter. Oh yes, you can take it too far...I warmed the .38 wadcutter load up to a little over 900 fps and obliterated the lube grooves and distorted the flat little nose, leaded my finely tuned K-38 nicely. Changing the alloy to 1% Sb and 2% Sn remedied all of it and it grouped like a super star!
Less is more until less is not enough.

[marek313]

I just read some article or post of someone doing pretty extensive testing on lead hardness specific to 357 magnum and basically BHN of 16-18 was as hard as you would ever want to go. Anything harder or shooting pure lino would degrade accuracy. My alloy for 357s is about 12BHN and i water drop after powder coat so maybe I gain another 1-2 points there but still not super hard. I've been trying out many different powders in 357 Magnum too and I think finding correct powder and load to match your bullet will be very important too.
I just go by trial and error and try not to overthink it. All guns are different anyway. You'll have to find what works for you.

[vzerone]

Larry Gibson you said this in 2010:

08-15-2010, 01:42 PM
The Arsenals (Frankford Arsenal specifically) did considerable testing (far beyond what we might consider "testing" today) with different alloys for the 45-70 cartridge. They found a 1-16 alloy worked the best. Not a lot of difference between a 1-16 and 1-20 alloy but I have also found the 1-16 alloy to shoot better than the 1-20 alloy when velcoity of a 400/500 gr .45 bullet approch 1350 fps or hinger. Thus I use that alloy in my 45-70 trapdoor loads with sevice rifle loads and my heavy 500 gr match load (BP or smokeless) all of which run 1300+ fps. I also use the 1-16 alloy for the medium power lion and leopard loads in my 450-400-70 Siamese Mauser using the Lee C457-500-FN or Lymans 457483 Gc with a slight HP. The 1-16 alloy is also very good in my baboon and chizzle tooth loads using the RCBS 45-300-FN GC bullets at 1850 fps. In my TC Black Mtn Magnum .50 cal ML the TC 350 gr MaxiBall cast of 1-16 alloy at 1570 fps is also excellent. I most often use 1-16 alloyed GC revolver bullets in .357, .41, 44. and .45 Colt loads where the velocity is over 1400 fps in revolvers, Contenders or rifles. Accuracy with all loads is as good as it gets and expansion with negligeable weight loss is excellent.

I do recommend 1-16 alloy for the loads that push above 1300 fps to 1800 - 1900 fps, especially for hunting loads. It also might work well above that velocity but I've not tried it as I mostly use a 50/50 WW/lead alloy in that range.

Larry Gibson

Which is it now, hard cast or 16-1? I'm confused.

[Silverseas]

Thank you all very much for your help on my quest for smaller groups at 50 to 100 yds.
For the last two years I have been using pistol range scrap that varies in hardness from 8 to 10 that I have mixed with various amounts of other lead from a local recycler. Weight was always variable as was fill out, wrinkles, base cavities and hardness. It did not matter much at 50ft, but now equipped with a Burris 3 to 12x pistol scope (the model with a front focus ring to minimize parallax), a good pistol rest and custom grips I am dreaming of shooting one MOA with the Blackhawk.

I now have a supply of Lyman #2 and pure lead from Rotometals with which I am mixing an alloy 95% Pb/ 2.5% Sn / 2.5% Sb. (call it "Lyman #2÷ 2"?). It tests BHN 9.2 plain and 10.5 with 2oz of magnum shot to 4lbs alloy.

If the weather is ok this weekend I will get out to the range and try a few rounds.

[quail4jake]

Thank you all very much for your help on my quest for smaller groups at 50 to 100 yds.
For the last two years I have been using pistol range scrap that varies in hardness from 8 to 10 that I have mixed with various amounts of other lead from a local recycler. Weight was always variable as was fill out, wrinkles, base cavities and hardness. It did not matter much at 50ft, but now equipped with a Burris 3 to 12x pistol scope (the model with a front focus ring to minimize parallax), a good pistol rest and custom grips I am dreaming of shooting one MOA with the Blackhawk.

I now have a supply of Lyman #2 and pure lead from Rotometals with which I am mixing an alloy 95% Pb/ 2.5% Sn / 2.5% Sb. (call it "Lyman #2÷ 2"?). It tests BHN 9.2 plain and 10.5 with 2oz of magnum shot to 4lbs alloy.

If the weather is ok this weekend I will get out to the range and try a few rounds.

Sounds like a great alloy and should heat treat well with that amount of magnum shot for As, good luck!

[Larry Gibson]

Larry Gibson you said this in 2010:

08-15-2010, 01:42 PM
The Arsenals (Frankford Arsenal specifically) did considerable testing (far beyond what we might consider "testing" today) with different alloys for the 45-70 cartridge. They found a 1-16 alloy worked the best. Not a lot of difference between a 1-16 and 1-20 alloy but I have also found the 1-16 alloy to shoot better than the 1-20 alloy when velcoity of a 400/500 gr .45 bullet approch 1350 fps or hinger. Thus I use that alloy in my 45-70 trapdoor loads with sevice rifle loads and my heavy 500 gr match load (BP or smokeless) all of which run 1300+ fps. I also use the 1-16 alloy for the medium power lion and leopard loads in my 450-400-70 Siamese Mauser using the Lee C457-500-FN or Lymans 457483 Gc with a slight HP. The 1-16 alloy is also very good in my baboon and chizzle tooth loads using the RCBS 45-300-FN GC bullets at 1850 fps. In my TC Black Mtn Magnum .50 cal ML the TC 350 gr MaxiBall cast of 1-16 alloy at 1570 fps is also excellent. I most often use 1-16 alloyed GC revolver bullets in .357, .41, 44. and .45 Colt loads where the velocity is over 1400 fps in revolvers, Contenders or rifles. Accuracy with all loads is as good as it gets and expansion with negligeable weight loss is excellent.

I do recommend 1-16 alloy for the loads that push above 1300 fps to 1800 - 1900 fps, especially for hunting loads. It also might work well above that velocity but I've not tried it as I mostly use a 50/50 WW/lead alloy in that range.

Larry Gibson

Which is it now, hard cast or 16-1? I'm confused.

You must just follow me from thread to thread just aching to show me up or prove me wrong about something, anything don't you? But know what? You hit the nail on the head.....you are "confused".......

That post was in regards to the 45-70 (all you have to do is read what it says) tested in the 1870s and 1880s with BLACK POWDER LOADS. The additional bullets I mentioned with use of 16-1 alloy with smokeless powders are gas checked bullets. Note also they are shot out of a rifle.

The OP is using a 158 gr RN in a 357 magnum revolver. Soft cast PB'd bullets can be very accurate at lower pressures/velocities out of revolvers. The OP also is now shooting 3" groups at 50 yards and wants to "tighten that up and get out to 100 yards". Now just where in the OPs 1st post which I responded to does he state what alloy he is using.....he doesn't.

Here is what I previously posted;

"If your bullets fit the cylinder throats (tight push through fit) and the cylinder throats are as larger or larger than the groove diameter of the barrel them "obturation" is a non issue because your bullets will be swaged down.

"making it too complicated"

Yes.

If you want to shoot small groups at 100 yards with your revolver then cast harder bullets, cast the best bullets you can, use a good alloy, size to fit the throats, use a good known lube and use a uniform, consistent loading technique."

Where in that post did I say 16-1 was not a good alloy.....I didn't. where in that post did I tell the OP to use "hard cast"......I didn't. Where in that post did I tell the OP what alloy to use......I didn't.

You know some people think you are really your uncle under another URL and name because you always break down and begin posting just like he does. Personally I don't care who you are, him or not. But to quote you from another thread; "get with the program". You might want to quit attempting to show me up all the time by making erroneous assumption of what I said because you know what they say about "assume". Besides, it's just making you look silly.

[vzerone]

You must just follow me from thread to thread just aching to show me up or prove me wrong about something don't you. But know what? You hit the nail on the head.....you are "confused".......

That post was in regards to the 45-70 (all you have to do is read what it says) tested in the 1870s and 1880s with BLACK POWDER LOADS. The additional bullets I mentioned with use of 16-1 alloy with smokeless powders are gas checked bullets. Note also they are shot out of a rifle.

The OP is using a 158 gr RN in a 357 magnum revolver. Soft cast PB'd bullets can be very accurate at lower pressures/velocities out of revolvers. The OP also is now shooting 3" groups at 50 yards and wants to "tighten that up and get out to 100 yards". Where in the OPs 1st post which I responded to does he state what alloy he is using.....he doesn't.

Here is what I previously posted;

"If your bullets fit the cylinder throats (tight push through fit) and the cylinder throats are as larger or larger than the groove diameter of the barrel them "obturation" is a non issue because your bullets will be swaged down.

"making it too complicated"

Yes.

If you want to shoot small groups at 100 yards with your revolver then cast harder bullets, cast the best bullets you can, use a good alloy, size to fit the throats, use a good known lube and use a uniform, consistent loading technique."

Where in that post did I say 16-1 was not a good alloy.....I didn't. Where in that post did I tell the OP what alloy to use......I didn't.

You know some people think you are your uncle because you always break down and begin posting just like he does. Personally I don't care who you are, him or not. But to quote you from another thread; "get with the program". You might want to quit attempting to show me up all the time because it's just making you look silly.

Well actually you are wrong Larry. I was accidentally researching something about brinell hardness on the internet and lo and behold there that came up.

You're also wrong about saying it was strictly for the 45-70 blah blah blab when you wrote this sentence: "I most often use 1-16 alloyed GC revolver bullets in .357, .41, 44. and .45 Colt loads where the velocity is over 1400 fps in revolvers, Contenders or rifles. Accuracy with all loads is as good as it gets and expansion with negligeable weight loss is excellent."

Hmmm, me thinks you are the one that is confused!!!

Beside this there are others on this thread that agree with runfiverun and myself.

[Larry Gibson]

Silverseas

The #2 alloy or your 95/2.5/2.5 alloy should work very well, especially if either are WQ'd out of the mould. What powders are you using? I do pressure test and while I don't have the Lee 158 RN bullet I do have the Lee 158 SWC TL bullet. Perhaps down the road when you settle on a load we can test it?

Also if you stretch beyond 50 yards you may want to consider a GC'd bullet. You can use a softer alloy with the GC'd bullet for excellent accuracy at 1400+ fps if that's where you're going with it. It's what I "most often do" when pushing the 357, 41 and 44 Magnums that hard. However, with the PB'd bullet you are using harder will be better if you push to magnum level velocities in the 1200 - 1300 fps range. A BHN of around 10 is about the lowest I've found to work well up through 1200 +/- fps with PB's cast bullets in revolvers.

[Silverseas]

Larry, I plan on starting with my 'diluted' Lyman #2, the 95/2.5/2.5 alloy which in my first melt this afternoon tested BHN 10.5. I then casted about 50 each of the Lee 150s and Lyman 200. Here is a photo of the results:.
The powder I am using is Accurate #7 and with the 150 I will start at 9.5 gr. For the 200 7.0 grains to start. Sound safe to you?

When you test a load what is your process? This sounds interesting and is something I never expected to be a part of. Thanks for offering

[MaryB]

I personally have used #2 in 380acp, 9MM, .223 both reduced and full power loads and in 7.62x54r full power deer hunting loads. I have also bartered some 45acp and .308 boolits to my LGS in exchange for 100 pounds of soft lead. All worked well because they were sized to fit the particular gun they were being fired from. Rifle rounds were all gas checked of course.

[RPRNY]

Hard cast is for ease of commercial casters and lazy self-casters. With the possible exception of those trying to push rifle lead at 2400+ fps, for whom quite hard lead is a legitimate necessity, hard lead alloy is for the lazy. At the velocities you reference, BHN 12 is as hard as you require. As has been stated above, consistently well cast bullets, sized about .002" larger than groove depth, sufficient lube matched to velocity, and well matched gas checks, are more important. Do those things, and you will get good gas seal, no appreciable leading (when starting with a legitimately clean barrel), and fine accuracy.

[vzerone]

Well sure that hard cast stuff will shoot, it's like shooting jacketed. Myself I'd never use something as hard as #2 for full load hunting loads. I've see too many hard cast act like FMJ's on deer. I want some expansion and if you concoct the right alloy, or even use hollow points, you can get that expansion. I like a cast bullet to enter the deer's body, expand, do a long of damage to internal organs, then shear those pedals off, and the core traveling on out of the deer's body so it will leave a good blood trail if it doesn't go down immediately. Sort of like a Nosler Partition. Probably the worst alloy for hunting (except varmints if you have enough high velocity) is Linotype.