Paper Rings etc

[Don McDowell]

Sam it's just not worth it, wish I had left that rifle as is, it has not shot either patched or grooved bullets as well as it did prior. The one I had built with the 7 degree lead shoots circles around the other one.

[bruce m]

without wanting to denigrate the results of others.
both of my rifles, a 45/2.4 and a 40 72, started life with 45 degree transitions.
they are both chambered with no freebore, and for groove diameter bullets.
when shooting greasers and wiping, patches showed sparkly stuff, and lead rings about the thickness of a hair were often present.
usual alloy was 16/1.
bore diameter pp bullets often had paper rings appearing on wiping patches, and had the odd dirt digger at longer ranges.
the 45 remains at 45 degrees, and is not shot as much now due to recoil.
the 40/72 was converted to a 7 degree transition, and rings and sparkly stuff disappeared.
with the 45 degree transition, the core groups were a little tighter than with 7 degrees, but the fliers had gone away.
this is either due to the 7 degree being inherently less accurate, or something might be less than perfect due to using a throating reamer instead of the throat being on the chambering reamer.
of course the very best accuracy in both rifles comes when breech seating with the optimum airgap, and that happens because the bullet totally avoids any transition.
a custom bullet mould for the 40/72 produces a bullet that patches to bore diameter in the front for most of its length, and to the diameter of the fired case for 0.200", in an attempt to support the base of the bullet on obturation in a similar manner to the odg chambers but with a greaser chamber.
more than 50 lb of lead has proven this bullet to work out to 1000 yds, but I still believe that the bullets bump into the 7 degree transition, even as hard as 12:1 alloy which I have been using for some months now.
sometimes I harbout the desire to rechamber this rifle to 40/85 ballard to hold more powder and grease wads as well.
if this happens the transition on the reamer will most likely be 7 degrees.
incidentally, saami 45/70 chambers should have about a 12 degree transition, so those using saami chambers already have a lower than 45 degree transition.
each person needs to do their homework on what they already have before changing anything.
this because whatever you have can probably be made to work to your satisfaction.
there are no free lunches.

[Don McDowell]

Brian, also don't mess with those Browning chambers. They work just fine as is, go with a .448 diameter bullet, and keep the weight to 525 or less in that 45-70.

[MICHAEL HERTH]

Brent and Distant Thunder, What are the diameters of you 45 caliber chambers that work so well with PP bullets patched to bore?

[Orville]

BFD how can my bullets upset larger then yours when the diameter of my chamber is .472. What is the diameter of you chamber?

[COBPTR]

Not often do you see a "mine's smaller than yours" argument on a forum.


Robert G.

[Don McDowell]

[Lumpy Grits]

Semtav-Let me suggest that you do a chamber cast, to confirm that the chamber length vs your case length are compatible.

Gary

[BFD]

Not often do you see a "mine's smaller than yours" argument on a forum.
Robert G.

But it is no surprise there are so many titillated onlookers without an skin in the game...

[BFD]

BFD how can my bullets upset larger then yours when the diameter of my chamber is .472. What is the diameter of you chamber?

Because you have removed more metal in front of your case mouth than I have. That's all that counts really. My chambers are plenty tight so far as the brass is concerned. Like yours, groove diameter bullet has no chance of chambering in my rifles, even if seated deep in the case.

[Orville]

BFD you have a problem telling me your chamber diameter? If your a math wizard or you can find one tell me how far up that 7 degree slope (lead) before it is back to groove diameter and the distance that point would be from the case mouth?

Paper or lead rings ar no mystery. The bullet upsets in the case, if the chamber is large enough so the bullet upsets larger then the groove diameter of the barrel and you have a 45 degree lead or wall at the end of he chamber. The bullet as it passes over it leaving something there, paper rings, lead rings flakes and or fins on the bullet. It is easy to figure take your chamber diameter subtract your brass case wall thickness twice that will give you the diameter of you bullet as it enters the barrel passing over the sharp lead.

Chamber diameter .482
Brass Minus .020. (Case wall thickness .010)
Equals. .462 this is the diameter of you bullet as it enter the barrel.

The .004 of your bullet has to go some where, be it paper or lead. Stack of wads, alloys, amount of bullet in the barrel, and breech seating can help alleviate this.

[BFD]

Orville, the chamber is about 1.5 thousands per side larger than the diameter of the case mouth with bullet. You figure out what that is. My chamber reamer drawings have been posted many times. I'm sure you have seen them and taken notes. You will need to revise your math - as you know., of course.

I'll repeat one more time - I have a .45 degree transition and I do NOT get paper rings. This is not magic. Pretty simple really.

I also get accuracy. Much better accuracy. So does everyone else that uses a similar chamber. Your chamber is great for those that want a traditional to the last detail. Or a decent hunting rifle. it is not a target rifle chamber for the 21st century in my opinion. The results guys like Jm and myself are having make it pretty clear that our chambers work.

[montana charlie]

Okay, I just spent an hour 'making pictures', and here they are ... with the information typed below.




Everything is drawn very close to exact scale. The chamber diameter (at the neck) is .482", and the bullet is patched to .460".
If the chamber was .472" and the bullet was patched to bore, you would see the the same differences at the chamber step.
The only difference that would be present is that the bullet would be much further out of the case.

The top of the top drawing shows a case long enough to fit the chamber, and it is against a 45° chamber step.
Note how small the area is that lead or paper could obturate into.

The lower half of that picture has the same chamber, but the case has been shortened by (only) ten thousandths.
Note the dramatic increase in volume for catching lead or paper.

The top portion of the lower picture shows the full length case against a 7° chamber transition.
Note the amount of 'emptiness'. Paper will not be left in this transition as it will be 'funnelled out'.
But the area available for distortion of the original bullet shape is obvious.

I didn't redraw the lowest step because you can imagine a 7° transition in conjunction with a short case length.
Again, stuff won't be 'trapped', but deformation of the bullet will be considerable.

I fully agree with Brent that the 45° transition leaves the smallest 'distortion zone' for the bullet to pass through, but I also insist that full length cases are just as critical to pushing a bullet out of the muzzle that looks like the one that fell out of the mould.

[Jim Kidwell]

Just consulted all of our rifle record books for our BPCR armory going back 20 years.
There is no mention of paper rings.

Maybe they were not so anal. ...............

[Distant Thunder]

mc,

Well done! Case length is obviously very important in either chamber.

Just to be absolutely clear, I do not get and have never had paper rings with Brent's chamber in my .45-70 Hepburn. That rifle has a .451" bore diameter, my bullets are sized to .4505" after patching. The fired cases will accept a .4518" gauge pin, but not a .4528" pin. There is very little room for the .100" of the bullet that is seated in the case to expand before the entire bullet is in the bore. The area that it could expand into would be considerably more with at 7 degree angle than it is with the 45 degree angle it now has. I can see that if my cases were too short, and they are not, the 45 degree could cause problems.

montana charlie's drawings make the difference very clear. Both designs will work, it's just that for long range target shooting the 45 degree design seems to work better. Brass length is important in either.

The only rifle I have seen paper rings in is my .40-65 when using patched to groove diameter bullets, and that is only occasionally. I may have some brass that are just short enough to cause the problem. I will be watching for this as I do my load/bullet development.

Jim