Bullet hardness and obturation

[dave roelle]

Has anyone investigated "obturation" relative to bullet hardness ? ----how hard is "too hard to fully seal things up" ?

Certainly powder charge figures in the discussion so i'm thinking about the more common 45 caliber loadings from say 65 to 75 grains

Thanks in advance

Dave

[country gent]

I use 20-1 in my paper patched loads and get good accuracy many things affect this lead hardness and size of profectile. wieght, A lighter bullet starts moving faster and easier than one that is heavier. Bullet fit to bore is also a factor a few thousandths under bore dia and you have that much ore to obtrate, a finger snug fir only has rifling depth to obtrate up.

[Don McDowell]

Kurt has looked into that quite a bit. Dan Theodore and Kenny Wasserburger have also done quite a bit of investigating along those lines.
I've found in my 44's that some bullets respond quite well to 16-1 alloy, and some don't seem to matter whether 16-1 or 20-1. I do have a small supply of #2 certified, but am hesitant to try that mostly due to the limited supply and being plumb happy with the 16 and 20. In Perry's book he dives into bullet hardness , and along with Winchester catalogs, we can see that in the late days of the Creedmoor era, 14-1 and 11-1 were highly thought of alloy.
I do believe that how hard an alloy can be also depends quite a bit on the bore to bullet diameter relationship, and I suspect that shooting hardball alloy with bullets patched to groove would probably turn out just fine..

[dave roelle]

Thanks Guy's----------------certainly alloys to 11/1 can work then------------i'm going to test some harder, but the only results will be grouping and leading--------------it just doesn't snow enough here to use that method of bullet recovery

PP to bore in this case

Keep well stay safe

Dave

[Don McDowell]

There has been some bullet capture study done with patched bullets using boxes filled with oil soaked sawdust. But in the end it's what the target tells that matters more than what a recovered bullet looks like.. If an exceptable target can't be produced, that's when capturing bullets to investigate blowby and all the happy stuff that goes with that comes in handy.
Keep us posted Dave.

[Kenny Wasserburger]

Don is laying it square. Perry's book is a great resource, the results of a special match at Creedmoor listed all the shooter's Data even Bullet alloy! And also their method of Patching! This was 1879. I can not stress the importance, of this book to the modern shooter wishing to try or use PP in competition. He even stresses the importance of increasing powder charges to hold the vertical at long range. This mirrors my own findings of shooting 1000 yards and further, these past 20 odd years with my 21 year old Shiloh.

KW

[Deadpool]

http://www.lasc.us/FryxellCommentsCBAlloys.htm

Fryxell's formula for matching hardness to the chamber pressure is:

The chamber pressure (PSI) needed for decent obturation = the maximum bullet hardness (BHN, Brinnel Hardness Number) X 1422.

[Don McDowell]

Old catalogs are invaluable for the information they contain. The 1875 Remington Catalog, page 30 at the bottom of the page begins to make reference to bullet alloy. It states in part that it is now know to be a mistake to use the purest of lead, the bullets even when made quite hard would upset with the powder charges now in use. Then goes on to say that it is a decided advantage to harden the lead using 3/4 oz of tin to the pound of lead. Again this was 140 years ago,, smokeless was not quite yet on the horizon..
We have a long ways to go to overcome some of the stuff we thought to be actual fact 40 years ago.. Somehow this information now being brought back from the dead was totally over looked when this bpcr craze got started back in the 1970's.

[Kenny Wasserburger]

These old catalogs have been a wealth of information. Metals are weighed in troy ounces, so that's quite a bit of tin. They also lay to rest many misconceptions once thought true.
KW

[Don McDowell]

Kenny that's sort of like I said the other day when we visited. How in the world did stuff like contained in that Remington catalog and Sharpes book escape folks?

[Kenny Wasserburger]

Don, I don't think other than Brother Garbe knew. He long ago was the guy that said 1-20 alloy. And so few of use are actually shooting PP bullets. Fact is some have purposely over looked the data available, to further the pure lead patched Creedmoor bullet concept or rumor.

My own patches are .900 wide about 110 is over the base one bullet is .120 over, so .790 to .780 up the side of the bullet, of course depends on the bullet length, my other patch template is just over an inch.
KW

[BrentD]

The 16:1 alloy of Sharps LR bullets has been known by current shooters for decades. But few if any, went there. The bullet designs that they shot in the 1980 and 1990s and even into the early 2000 were generally quite blunt and really didn't require the stronger alloys. So, even though 16:1 was well known to be the alloy of the old guys, not many felt the need to go there.

[Don McDowell]

I know back in the late 70's early 80's were were shooting the blunt sharps style bullets cast from the same pure lead we used in the round ball guns. I'm wondering also where did those long freebored throats come from? None of the folks like Kurt and Dan T etc that have done chamber casts on original guns seem to have seen anything like that...
But be all that as it may, we do have the good information to go from now.

[BrentD]

The long throats came from the influence of smokeless philosophy and add to that the strange, unexplainable hopeful monster of a chamber that Wolfgang Droege created in some wild nightmare one night. That one is truly a mystery and why he stuck with it for so long is another mystery.

[dave roelle]

Folks -------thanks again for the information !!!! What has been reported is certainly helpful, but doesn't give us the "upper limits" of the obturation/hardness question.

Thanks to Don and Kenny (get well soon sir) for the historical data !!!!! their reference materials are extremely valuable and not readily available.

The Fryxell equation helps, but i'm betting its theoretical not empirical.

I hope to do some limited testing soon and see if i can find the upper limit of hardness, at least in my Shiloh 45-70----------seems that a hardness just below that limit would support the best accuracy----fully sealed bore with lowest distortion of the bullets shape.

Please keep the information stream alive

Dave

[Don McDowell]

Dave I'm looking forward to seeing your results. I am betting that where you end up on the hardness will be quite surprising to a good many.

[dave roelle]

Perhaps Don-----i just finished my Brinell tester so i'll have some reasonably accurate data---at least from a relative hardness perspective-----------i'll harden things up until i some lead show up and see what acurracy results.

Heading to the ranch hog chasing

Dave

[Lead pot]

The alloy is not the only thing that regulates bullet obturation from what I'm seeing.
Bullet weight, diameter, ogive shape, powder charge, and wad stack/material, flat based, cup based, dish based hollow based, as well as the relation of hardness and diameter of the bullet. All of these variables effect the setback and obturation.
Using 1/11, 1/14, tin/lead alloys for a PP bullet you better make sure that it is patched slightly over bore diameter or even groove diameter would be better. Some of the bullets used by the ODG's where more then a cup based bullet that where more like a thicker skirt hollow based bullet. I have looked at old Remington bullets that where thick walled hollow based and some had GG with a shallow hollow base, not cup base. If any of you have shot front stuffers with a pure lead mini ball and looked at some recovered bullets you would find that when you approach 75 + grains of powder you will see the skirts blown out and I'm sure the ODG's knew this and used a harder alloy for the cartridge rifles to prevent the skirt blowout, I cant say that for sure.
I see a lot of gas cuts with PP bullets that where cast with alloy harder then 1/16 T/L patched slightly under bore especially with a improper wad stack. Also a hard bullet patched to bore that did not get upset enough to make solid land engraving that stripped and most likely did not get the proper rotation to stay stable at long range.
Nose setback is also very evident using a alloy not balanced with the ogive design. A creedmoor type of ogive will set back more then a long elliptical. A .45-70 will not get setback as much as a .45-90 or .45-120, I don't have a .45-110 so I have never seen what bullets do with that caliber.

You can get by using a alloy mix 1/20 T/L in a .45-70 with minimal nose setback and it will fill the grooves very well, but shot with 110 gr of 1F from a .45-120/3-1/4 a money bullet will look like a postell if the nose gets set back straight.
A alloy using a mix 50/50 WW lead will hold a nose as well as 1/17 tin/lead. The antimony does wonders for holding the nose profile.
A 1/16 tin lead alloy will let you get by pretty well. I have never seen any evidence that I need any alloy harder for a PP bullet then 1/16.
I use 1/19 that is a mix of 19#lead 1# 95/5 solder that has 5% antimony in the one pound roll. This holds all of my bullets with a very slight shortening the over all length. If you want to get the most from your bullet, it helps if you do a little work to see what your rifle and load does to it. If the bullet looks just as good shot as it did before it was shot then it's up to you what the down range looks like.
Kurt

[Don McDowell]

Kurt what are the details of that bullet you have pictured there. It's fascinating to see the paper grain embedded in the base, the case mouth bite, and then the definet end of the patch and the obtruration of the bullet.. Neat stuff.

[dave roelle]

Thanks Kurt-------------your input is always valuable----------and certainly their are many variables !!!!!------------do you have any idea the hardness of the 19/1 + antimony bullet ?

I'll move ahead and see what happens to harder than 1/16 air cooled--with my current wad column---worse case will be a lead mine to clean up-----best case will be finding the upper limit of hardness and hopefully a touch better bullet flight.

Again Thanks Kurt

Dave