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Author Topic: Deepening Chambers  (Read 933 times)

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Offline Omnivore

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Re: Deepening Chambers
« Reply #15 on: October 10, 2018, 04:25:06 PM »
rodwha; You start playing around with this bullet design stuff and I think you'll soon find out why I like having two short lube grooves.  I also like a tapered heel, and for paper cartridges in a Pietta 44, about .440" at the base to about .444".  So with that 225L, the base band is tapered.  That bullet slips in past the rear lube groove, right up to the back of the middle drive band.  It loads very easily, in paper cartridges, in my Piettas (which have the smallest chambers of the 44s I own) without having a radiused base.  Also with the two grooves the bearing surface doesn't get extreme.

Another thing about a radiused or beveled base is that if you load it directly onto the powder in a paper cart it will encourge the incidence of powder granules getting between bulet and case, making loading just a bit fussy.  Add a thin card wad over the powder though, and that all goes away.  Just some stuff to think on.

If I ever decide that I need a 140 grain bullet (which yields excellent kinetic energy in the Army model guns), I'll take the tapered base and drive bands of the 225L and stick a heavier nose on top of it.  That could make a more compact (shorter) bullet than any of the others in that weight range, I think, or very close to it, depending on the meplat and ogive you chose.

With higher capacity chambers I'd be tempted to take that longish 46-250P, or something very much like it, and have it converted to a core mold for a hollowpoint of around 140 grains.  A bullet like that in a Walker, or "Buffalo" Remington, or 12" Colt Army would be a good big game load.  I have a 12" Colt I've yet to play around with...  Too many projects, too little time.
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Offline rodwha

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Re: Deepening Chambers
« Reply #16 on: October 10, 2018, 05:11:47 PM »
Why is it that you like the two lube grooves?
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Offline Omnivore

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Re: Deepening Chambers
« Reply #17 on: October 17, 2018, 03:03:50 PM »
Quote
Why is it that you like the two lube grooves?

Well that is a good question.  You made me sit and think about it before I could reply.

First, I like a relatively long heel, or tapered base, or to put it another way; I like having the bullet sit down into the chamber some ways before ramming.  That makes the loading of cartridges easier because, with a very short heel, the bullet may become misaligned with the chamber prior to ramming.  A bullet that slips down in there some ways, and has a heel or tapered base that sits in there somewhat firmly, will stay put as if it really means to be there, and not fiddle around as you're rotating the cylinder and such prior to ramming.  And in field carry that means something because you might be walking, or you might not have the muzzle pointed straight up while loading.  So there are reason for this, that matter to me, and the little 0.050" length or shorter heel that we often see in the catalogs just isn't amenable to this kind of loading.

Now that THAT has been said, a long heel leaves little room for a single lube groove unless the bullet is very long, and I like a lot of lube in the load, AND I like short-for-weight bullets.

SO, to my current way of thinking, the best bullet has two short lube grooves; the front one with full diameter drive bands both in front and in back of it, and the other, rear lube groove just in front of a tapered base band.  When initially inserted into the chamber, the bullet's tapered base band slips all the way in, and then up past the rear lube groove to the rear of the middle drive band.  At that point it’s tenth inch or more into the chamber, and it isn’t going anywhere.

The drive band and lube groove arrangement of the 45-225L is my concept of the ideal bullet foundation (drive bands, lube grooves and base) for a conical in a 44 percussion revolver.  Use it to build on the nose profile and weight you want, size it to no more than one thousandth over chamber diameter, and you'll have a good bullet that loads easily, carries at least some significant amount of lube, doesn't have too much bearing surface, and is still quite compact, thus leaving more room for powder (depending on the nose you put on top of it).

Sure; you could simply make a long heel (tapered or otherwise) with just the one lube groove (i.e. deleting the rear groove), but upon obturation you're increasing the bearing surface and depositing less lube.  That doesn't appeal to me, but I can't say it would be wrong.

I may very well change my mind on that at some point down the road--  Less groove volume of course, all else being equal, will result in a shorter bullet, and in the Army revolvers which have very limited chamber volume that means more room for powder.

The caveat here is that I'm talking about hunting bullets.  For match shooting this conversation is mostly meaningless.  I say "mostly", because I could see using cartridges for match shooting, and the ease-of-loading, and lube, factors are therefore still relevant unless you're talking all round ball all the time (and why would you if you had a good conical such as a SWC or WC that cut cleaner holes in your targets?).
But whoso looketh into the perfect law of liberty, and continueth therein, he being not a forgetful hearer, but a doer of the work, this man shall be blessed in his deed.   James 1:25 (KJV)

So speak ye, and so do, as they that shall be judged by the law of liberty.   James 2:12. (KJV)

Offline rodwha

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Re: Deepening Chambers
« Reply #18 on: October 18, 2018, 09:32:59 AM »
Quote
First, I like a relatively long heel, or tapered base, or to put it another way; I like having the bullet sit down into the chamber some ways before ramming.  That makes the loading of cartridges easier because, with a very short heel, the bullet may become misaligned with the chamber prior to ramming.  A bullet that slips down in there some ways, and has a heel or tapered base that sits in there somewhat firmly, will stay put as if it really means to be there, and not fiddle around as you're rotating the cylinder and such prior to ramming.  And in field carry that means something because you might be walking, or you might not have the muzzle pointed straight up while loading.  So there are reason for this, that matter to me, and the little 0.050" length or shorter heel that we often see in the catalogs just isn't amenable to this kind of loading.

I have learned this myself. The 0.05” heel allows it to easily be tilted while loading. This is one modification I want to make to my bullet(s).


I attempted to insert an additional quote but jacked it all up so I’ll go at it from another angle...

“Sure; you could simply make a long heel (tapered or otherwise) with just the one lube groove (i.e. deleting the rear groove), but upon obturation you're increasing the bearing surface and depositing less lube.”

I’m at a loss for why the heel of your design wouldn’t obturate just the same and create the wide driving band. Many feel that an undersized (~.446”) ball from a Pietta obturates enough to fill in the .452” grooves of the barrel.

It also seems to me that one could easily make it shorter with one lube grooves and make it a little wider if one felt they needed/wanted more lube and omitting the second driving band.

I did like that your lower band was virtually chamber diameter to hold it solidly in place, but then it seems on a two band bullet this can still be done, but I’d need both revolvers to have pretty much the same chamber diameter. I had to pull 3 bullets from my ROA and measured them. Surprised they weren’t 0.453” as I assumed, but were 0.452”. I could bring my NMA chambers to 0.451” and call it good I think (I’m afraid to go much further than the 0.449” they are as those chambers walls look so thin as is).
« Last Edit: October 18, 2018, 09:57:26 AM by rodwha »
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Offline rodwha

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Re: Deepening Chambers
« Reply #19 on: October 18, 2018, 10:33:03 AM »
Did you get away from using a lube cookie?
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Offline Omnivore

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Re: Deepening Chambers
« Reply #20 on: October 18, 2018, 12:04:37 PM »
Quote
I’m at a loss for why the heel of your design wouldn’t obturate just the same and create the wide driving band.

Simple; it will obturate very well, of course, but it won't create a long (don't confuse "long" with "wide") bearing surface because, essentially, it has a lube groove in it.  To wit, the 225L inserts freely to a depth of .125", but only .075" of that can obturate and become a drive band;
http://accuratemolds.com/bullet_detail.php?bullet=45-225L-D.png

Note that Tom's given band diameters are arbitrary.  You order as what you want.

Also notice the tapered base band.  If its widest point, at the front of the band, is right at, or one thousandth less than, the chamber dia you'll be just fine, but I like the smallest part of it, right at the base, to be at least several thousandths less (like four or five).  Order your base band dimensions carefully, for the smallest chamber you intend to use.  For a straight heel you want it several thousandths less than chamber.  For use in paper cartridges make sure the base band or heel is at least two, to three thousandths smaller besides, to account for at double, to 2.5 x, the thickness of the paper.  As opposed to the major diameter tolerance, base band or heel tolerance should be specified negative.

One or two thousandths difference between different guns' chambers can be dealt with just fine.  For both a .452" and a .450" chamber, a conical bullet of major diameter ordered as .452" or .453" (positive tolerance) will do you just fine.  I would then lube size it to .452" and use it interchangeably in both guns.  If you wanted to eliminate the sizing process, then I'd say order it at .452" pos tol, and leave it at that.  It may shave some lead on loading in one or both guns, but without sizing it I think that's going to be unavoidable.  Plenty of shooters use bullets far larger than two thousandths over chamber-- they're just not getting ideal loading convenience is all.

Quote
Did you get away from using a lube cookie?

For some of the hunting loads I'm experimenting with, yes.  With the longer 225L bullet, the cookie takes up more powder space that I'd like-- It won't take 30 grains of O.E. plus a lube cookie in an Army chamber (neither my Piettas nor the Uberti Carbine).  The 45-200S will leave room for 30 grains plus a cookie in an Army chamber however.

Though I killed a nice white tail buck with the 200S, a couple seasons ago, from the Walker with 45 or 50 grains of O.E., I would like to try the Uberti Remington Carbine and the 45-225L HP conversion this coming season.  That means no cookie.  We'll see.

Still and all, for now, even with lube cookies I like having the lube grooves for reasons stated above.  Cookies in most shooting, and especially in all plinking or other high round count shooting, are absolutely the way to go IMO, but in deer hunting where typically one, or at most two shots would be fired, the cookie is not required.
« Last Edit: October 18, 2018, 04:37:00 PM by Omnivore »
But whoso looketh into the perfect law of liberty, and continueth therein, he being not a forgetful hearer, but a doer of the work, this man shall be blessed in his deed.   James 1:25 (KJV)

So speak ye, and so do, as they that shall be judged by the law of liberty.   James 2:12. (KJV)

Offline rodwha

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Re: Deepening Chambers
« Reply #21 on: October 24, 2018, 07:29:05 PM »
Rodwah, let me know what Mr. Clements says, as I was thinking of asking him the same question.

I’ve waited a little over two weeks with no response.

Anyone know of anyone who might deepen the chambers on a NMA and ROA?
"Were I to leave where else would I go? Your words of life and of truth You hold." - Third Day