paper rings left in chamber?

[Black Jaque Janaviac]

I tried some 195 grain roundnose bullets in my .35 Whelen. With 58 grains of RL-15 I did not get great accuracy. Bullets were all over an 8 1/2 x 11 inch paper at 75 yards. This was a grease-groove bullet (Lyman's current 358430) sized to .358 after patching.

I noticed occasional paper rings left in the chamber. What causes this and does it affect accuracy?

[Red River Rick]

Your cases are to short for the chamber in your rifle.

RRR

[Black Jaque Janaviac]

OK. So perhaps I shouldn't be trimming them.

But how do I know what length they should be?

Can excessively long cases cause pressure spikes?

Will a case that is too long even chamber?

I'm thinking I could run a .270 case through my .35 Whelen die then try chambering it. The .270s come out to something like 2.550" as opposed to the standard 2.494" .35 Whelens. My trim-to length is 2.484"

I hope I don't have to do something like make a chamber casting. I've got the cerrosafe, but I didn't like using it before. It's a pain getting it into the chamber, and out again. Plus the castings came out all wrinkly. (this I did with my .357 magnum)

[redneckdan]

http://www.sinclairintl.com/cgi-bin/category.cgi?category=RESDTCL&type=store


something like that....except you would have to make one since they don't sell .358 diameter gauges

[Black Jaque Janaviac]

Since I don't have a lathe... How about this idea?

Expand a .270 case by running it through my .35 Whelen sizer. Load case with black powder and a paper wad. Fire it.

I'm thinking that if the .270 case is too long it will imprint on the ridge that separates the chamber from the throat. Using a paper wad & black powder would keep pressures within safe limits.

If I don't see any imprint of the ridge (or whatever is causing these paper rings) I'll run same case through FL sizing die and repeat - assuming I'm getting enough pressure to cause the case length to increase.

Good idea? Or hair-brained?

Oh, by the way, is this known to be an accuracy destroyer?

[leftiye]

Do a chamber cast? Cut your .270 cases where the chamber neck line is, and see if they chamber, Or do as you've said above, neck a case (.270) up to .35 and trim a little off at a time until it will chamber. The case mouth should prevent closing the action if it is too long, and you don't push too hard.

[405]

http://www.sinclairintl.com/cgi-bin/category.cgi?category=RESDTCL&type=store


something like that....except you would have to make one since they don't sell .358 diameter gauges

This is a good method and soooo handy! I have no idea why gauges larger than .338 aren't made. They're almost stupidly simple:mrgreen::mrgreen:

BJJ,
Lathe is not needed. Just a drill press or a handheld drill and a file will work. The basic material is nothing more than a short length of mild steel or brass rod, etc. about full OD of a fired cartridge neck or a little larger. Turn down about 1/2" of the rod using the drill to exactly the OD of the fired case neck. Re-chuck and turn down to .358" about 3/8" of the rod from next to the chuck jaws out to within about .1" of the end. The .1" end will still be neck OD. Cut rod at the beginning of the .358" section. Total length of gauge is about 3/8" + .1".
Then dedicate a case to use with this gauge. Cut about .2" off of neck.

Final fit of gauge into the shortened case neck should be barely snug slip fit. Start gauge into neck, leaving OAL on the long side. Carefully insert into chamber and close action. Carefully open and retrieve cartridge/gauge. Measure length. Presto

Method works for all calibers. Just need the gauge, either bought or made and a dedicated shortened case.

The problem with firing something like a 270 in the 35 Wh. to get the end of chamber imprint is that chances are very good that it will give false reading of length. I'd bet the primer thrust would force the case forward when fired thereby imprinting the ring at an excess headspace gap. The dedicated gauge as described above and shown below will give a very precise chamber length at zero headspace.

Pic of gauge inserted into shortened case and ready to insert into chamber.

[405]

Aside from the case length theory?? I have gotten paper rings a few times. I'm just not convinced about the case-shorter-than-chamber theory. I've shot a lot!!!! of paper patched bullets ranging from swaged, smooth, pure and alloyed lead wrapped in paper to alloyed, cast, grease groove bullets wrapped in paper.

The pure lead, tapered, smooth swaged PP bullets have all been shot in modern chambers where there is a distinct step down at the end of the chamber which enters the throat and on into the bore. I know that some of these have been shot with cases shorter than the chamber. I have never gotten a paper ring from shooting this combination.

Conversely, the combinations that have produced the paper rings are those loadings in very old original guns that have NO distinct end to the chamber. They are chambered to take the case dimension then taper transition directly into the bore. I've gotten paper rings from shooting paper patched grease groove bullets in this type chamber. This suggests a connection between the PP grease groove and/or the old chamber design and the paper ring.

Absolute, exclusive evidence... no. Anecdotal suggestion... yes.

[montana_charlie]

This is a good method and soooo handy! I have no idea why gauges larger than .338 aren't made. They're almost stupidly simple:
I really like that gauge!
Here is an alternate idea for making the fitted slug...

Cast your bullet in pure tin, or Cerrosafe, to get a hard one.
Epoxy a washer to the base, and file the washer to the right diameter while the 'bullet' spins in a drill.

CM

[Black Jaque Janaviac]

405,

Thanks for the responses. Unfortunately, as you mentioned that your evidence is anecdotal not scientific, I have found the paper rings in a modern gun (distinct chamber-throat transition) with both grease-groove & smooth-sided boolits.

So just between the two of us, we've encountered paper rings in abrupt chamber-to-throat guns, longer cases, and both types of bullets (GG & smooth). I guess we are back to square one - we don't really know what causes the paper rings.

I'm not even sure if I would say that the presence of paper rings necessarily correlates to inaccurate ammo.

[montana_charlie]

I have become conditioned to blurt out "cases too short" every time someone complains of ring-shaped pieces of reloading components being left in the chamber.
But, that knee-jerk reaction is subdued when the discussion centers on ammunition that is not intended for BPCR.

Small calibers, hard alloys, high velocities, and smokeless powder all combine to make me wonder if 'the simple truth' is more complicated when those factors are present.

I still think short brass is the problem, but I held back on blurting because you are shooting a bottlenecked case. It's not that a bottleneck cannot cause the problem.
It's simply that if I said it is too short, I would feel obligated to have a suggestion for making it longer...and I don't.

But, if you can switch to cases that do match chamber depth, and cease finding the paper rings, your anecdotal evidence will have taken on a validity approaching that of the scientific kind.

So, while you may be back at square one, square two is visible in the distance...

CM

[405]

BJJ and MtC,
Can't disagree with either post. Interesting stuff that needs more thinking and what ifs and sharing of ideas.

Getting back to the 35 Whelen which has the modern, distinct "end-of-chamber" step. If the case is near full length for the chamber, the chamber neck dimension isn't too large and if throat diameter approximates groove diameter of the bore then the most likely thing that could cause or leave a ring of paper or lube or lead or whatever would be the partial constriction beveled leading edge of the rifling.

If the thoat dimension is larger than bullet diameter then obturation, as the bullet passes thru the throat, could cause the paper to be "scraped/bunched" as the bullet is swaged back down as it enters the bore.... leaving the ring behind.

A normal chamber neck diameter dimension and a case that is close to the actual length of chamber (modern type).... would eliminate at least that one possible cause for the ring whether paper, lube or whatever. That is why the above mentioned gauge tools in addition to taking a chamber casting would be very handy.... to get to a precise chamber length and diameter dimensions. Then seems like the focus should shift to bullet diameter vs throat diameter or throat length or some other possibility.

I know that some don't like to hear this but the 35 Whelen does exhibit a tendancy to lose headspace control. Another possibility I can see for leaving a paper ring could be.... a round is fired that has a case of correct (full) length of rifle chamber. As the firing pin falls and the primer ignites the case is forced forward leaving the case mouth slightly swaged into the leading edge of the end-of-chamber step. At this moment the bullet is partially out of the case and the swaged mouth "nips" a part of the bullet or paper from the bullet. Far fetched I know but just another thing to munch on.

Incidentally, I know that the grease groove PP bullet rings I get out of certain old BP guns with the old style chamber are exactly the dimension of the bullet base drive band. The leading edge of the bullet base drive band obviously is cutting the paper ring from the bullet as the bullet is moving forward between the case mouth and the entry into the bore. Each ring recovered is this same dimension and always present in certain loads. These facts seem more than anecdotal. The cause-effect as it relates in all situations may vary.

So, no big answers or reasons just some more food for thought. Prodding the brain a little is usually a good thing. Interesing thread!

[Baron von Trollwhack]

Why fuss? Make a couple of longer necked cases, follow the advice and make a tool so you can be on the money, case neck/chamber neck length wise and give it an honest try. You will have your answer. BvT

[windrider919]

I shoot .458 Win Mag. I have been shooting PP for several years and have 'suffered' from this prob;em. In face, I stopped loading multiple cartridges into the magazine because of it. In reply to the Baron Tw, leaving a ring in the chamber can act as a bore obstruction and raise pressures. Of course PP shoot at lower pressures because the patched bullet slides down the bore easily. Sometimes I think even easier than GG cast.

I do think that the brass length has something to do with the problem BUT it is also related to throat size vs true bullet diameter.

When I first started shooting PP I used store bought .450 500gr straight swaged bullets. My brass was under max length but untrimmed. I got a ring aproximatly 1 in 10 shots. I think the first time it happened I was not checking my bore each time. One of the round I fired Kicked the S**t out of me and the whole shooting line stopped to see what the heavier blast had been. The case extracted harder and showed all the clasic signes of EX pressure. It was not any kind of overcharge, thats guarenteed by my loading proceedure. The rifle was undammaged so I continued shooting, checking bore each time. A few shots later I saw a ring in the chamber, removed it and determined it was paper. What I found is that the next bullet can push the ring from the front of the chamber area into the throat and bunch up the forward edge of the PP. So I am very causiou to 'feel' the cartridge going home and the force required to cam the bolt.

Later I trimmed all my cases to a standard length (.010 under max) and started gitting a ring practically every shot. Accuracy was non-existant too. That brings up the next part of the problem. Checking around back then was when I found out the diff between BP and smokeless. I was also advised to do a chamber cast and see what the throat really was. Mine turned out to be .463.

So I tried using chamber filling length brass (minus .001 or so) and either using thicker paper, wrapping 3 times or what I do today which is use a .453 bullet and wrap twice to .461 / .462. When I now shoot bench rest I get 1" groups, however, I still get a extremely thin ring once every 75 or 80 rounds. I almost eliminated the problem but not totally.

This is just my experience, what has anyone else done to trouble shoot and solve the problem?

[looseprojectile]

not nesessary if you make a "pound cast" of the chamber.
I have done this for more than fifty years. Use a fired case and trim it down in length some, twenty or thirty thousandths.
Fill the case to an eighth of an inch of the mouth with something non compressable, such as lead. Epoxy will work. Stick a soft lead boolit in the case and chamber it. You may have to tap it into the chamber. Close the action on this assembly.
Use a wood dowell, I sometimes use a brass rod, near the bore diameter and POUND it to upset the soft lead and when you eject this assembly you will have the dimensions of your chamber length, bore, groove and leed to measure.
I never could see the need to buy cerrosafe.
Handle it gently.

Life is good

[Lead pot]

Mt. Charlie is right with the short case, but it goes a little further than that shooting PP or GG bullets in a modern chamber.
A case cut to the exact length of the chamber will still leave a paper ring using a pp bullet or a lead ring when you use a GG bullet. You can check this very easy by running a patch from the muzzle end very slowly and you will find the ring or part of it on the patch.
What happens is when the bullet obtrudes between the end of the case and the 45 degree chamber end it will shave lead or cut the paper and a ring is left behind.
With a lead ring it might take more then one shot to build up enough to form a ring but it is there. You can see it looking through a bore scope.
Even when the case is right up against the start of the 45 degree the small gap is still there is enough to cut the paper.

[docone31]

I had read about this. Paul Matthews wrote about it in his book, The Paper Jacket.
I have not run into this patching smokeless in the variety of rifles I have that I fire paper with.
Is this a something peculiar to BPCR, or is it a component of caliber?
I had worried about it when I first started patching my .303 British, however, I have not seen any evidence of it in my .30s, or .303.

[405]

Good question and may be caused by several things or conditions. It's even possible that rings get left sometimes and the shooter doesn't know it... just continues to shoot, so shoots out the rings. BP shooters may notice it more because they tend to wipe or clean between shots. While smokeless shooters shoot strings of several to many shots.

I think BJJ's original worry was that if the case mouth wasn't close enough to end-of-chamber the gap could cause a problem. I've never had it happen with that type chamber (modern throat) when the case was a little short. But, that is with BP, smooth-sided PP bullets. The only time I get consistent paper rings is with BP, grease groove PP bullets in an old type chamber where the chamber tapers down to entry into bore. That by design leaves a fairly large tapering throat diameter immediately in front of the case mouth. I guess my theory is... the open area allows the bullet to obturate to fill it then a paper ring is nipped off at the bullet base band as it moves forward and is swaged down to enter the bore. What the difference is between BP and smokeless in tendancy to cause rings- dunno?

Others have reported that they get rings in the modern chamber types (stepped, parallel throat) if the case is some too short for the chamber. Seems logical that way also. If the case is too much too short then there would be a void to fill as the bullet is obturated into it thus shaving or nipping off a ring.

Lastly, some think that if the chamber neck diameter is too large.... then as pressure builds the neck expands, the bullet begins to obturate outward before it leaves the case neck then shaves a ring off as it enters the step into the throat on its way to the bore. That theory makes sense also.

If leaving a paper ring happens inconsistently it could account for a dreaded flier most experience now and then..... along with about a jillion other possibilities. :mrgreen:

[stocker]

Older moulds designed for paper patch bullets in black powder cartridges typically had non parallel sides to the boolit. In other words narrower at the front of the main body than at the heel. I don't shoot them so I'm guessing this allowed the paper to slightly extend into the lands with no contact or snagging at the end of the chamber or on the leade. Perhaps the combination of short cases, relatively abrupt leade angles and boolits with parallel body sides combines to cause these paper rings. I wonder if a boolit designed with a taper to the sides would still do this? What if the leade angle was eased?

[docone31]

My wondernment,
With a paper patch, the base of the patched boolitt obturates. The paper will experience massive pressure. This will in most cases force the corner to expand, leaving the base of the boolitt reasonably intact.
I wonder if this stretching of the bottom of the patch is not a factor. Essentially, if my thoughts are on target, the bottom of the patch will expand untill it hits resistance.
Kinda like creasing paper, then tearing it on the crease except it develops a ridge that gets more abraded off, hence the consistant ring. I have heard these are hard, solid rings.
If it was caused by the leade, the paper would be lead coated from the patched boolitt passing by it.
It would also be drawn out of the bore by friction.
I am guessing it is the base of the patch getting distorted by pressure and being cut by compression.

[leftiye]

Sounds like the paper rings may be the result of Black Powder obturating the boolit into the gap in front of the case mouth. Might not happen with really hard boolits like Doc uses and smokeless powder.

Of course, it might happen at the base of the boolit like Doc said too.

I wonder if Montana Charlie's method of seating a boolit deeply in the case, sized to groove diameter, and using black powder doesn't cause a lot of obturation before the boolit leaves the case. This then would be sized down as the boolit entered the leade, and then again when the boolit engraved in the rifling. Maybe a really long leade (freebore) would help in that scenario (with the boolit seated into the rifling).

[windrider919]

I am shooting a 20-1 alloy(ww + tin) which is hard but not as hard as some are shooting. I shoot smokeless only so the bump up does not happen. I have a bullet trap at 100 yards that is a water filled open ended channel. Bullets retrieved are perfect except for rifling marks, unless they hit the side. I have miked lots of these bullets and the amount of bump up is greatly exaggerated. Most show only .001! Few will even show .002 up from the original size. Even with pure soft lead fired with BP the most I have ever seen was .003 expansion of the base ring. There is no expansion miked with GC bullets so the theory that the bullet base 'slumps' and expands out the GC doesn't fly either. My 458 Win Mag has the standard SAAMI chamber with the sharp transition between case end and bullet throat which is unfortunately oversize at .463. The long throat (ment for long 500gr FMJ solids) has a slight taper then the ramps of the rifling start. I have a frequent problem with rings which lessened with full chamber brass. I am still looking for a solution.

FYI here is a picture of what I am shooting

[leftiye]

Windrider,
Your info is interesting, just what the doctor ordered, and which we need more of here. I am a little confused though. Your info concerns boolits which have gone clear through the bore. I'd have expected them to all be the same size after transversing the barrel, the different sizes surprise me. Maybe bumped upwith impact into the water? Going through the barrel isn't much enlightening about how big they might have gotten at the moment of ignition, and engraving into the rifling if not supported by the chamber or the freebore.

[montana_charlie]

leftiye is right, windrider.
Any bump up that is occurring should be taking place in your .463 'throat'. After that bullet passes through the bore, it should match bore dimension...which I presume is somewhat smaller than .463".

What is the actual measurement of a 'trapped' bullet...what was it's patched diameter before firing...and what are the bore/groove diameters of your barrel?
CM

[montana_charlie]

Until someone produces a video which shows us all what actually happens inside the chamber, I guess we must all remain 'trapped in our own ignorance'.
But, just to trade theories, logical assumptions, and wild-assed guesses...

Sounds like the paper rings may be the result of Black Powder obturating the boolit into the gap in front of the case mouth. Might not happen with really hard boolits like Doc uses and smokeless powder.
I think those two things are important 'variables' and that they do change the odds of finding paper rings left in the chamber area...if there is a gap big enough to collect paper.

When the case mouth touches the chamber step, the resulting 'void' is a groove around the chamber that has the profile of a right triangle. One of it's 'sides' is formed by the edge of the case mouth, and is the same as the mouth wall thickness, about .010". The adjacent 'side' is open unless a bullet (or something) is bridging the gap, but it is also about .010". The angle of the chamber step would then form the 'hypotenuse' of the triangle, and it will be slightly longer than .010".

My point here is that the volume of the gap is so microscopic I doubt that it could collect enough paper to even be noticed by the average shooter...unless he was equipped with a lighted optical instrument that helped with looking down inside that hole.

As case length becomes shorter in relation to actual chamber length, the volume of the gap triples if the shortfall is only .010". Then there might be enough trapped paper to see...

Of course, it might happen at the base of the boolit like Doc said too.
I tend to doubt docone31's theory (assuming I understand it as he intended).
Yes, I can see how a sudden 'swelling' of the bullet could tear the patch at the corner where it turns over the base...
And, yes, I can see how that could separate the base covering from the rest of the patch...

But, in the case of docone31, his 'paper ring' (if there was one) would have a tail attached to the middle...and I doubt it would remain inside the chamber.

In the case of the BP shooter who complains of paper rings, his over-powder wad would surely sweep the 'base cover' right out of the bore along with everything else.

Nope...I believe the 'paper ring' problem is caused when paper is packed into a void that allows it to be 'off to the side' when the train goes through the tunnel.

I think the lead tries to obturate into a gap caused by short brass, but only succeeds in leaving paper packed in there.
And...because the paper IS tucked away in that gap, the over-powder wad can pass by without collecting it -- on some shots, many shots, or all shots -- depending on the severity of the problem.

I wonder if Montana Charlie's method of seating a boolit deeply in the case, sized to groove diameter, and using black powder doesn't (a) cause a lot of obturation before the boolit leaves the case. This then would be sized down as the boolit (b) entered the leade, and then again when the boolit engraved in the rifling. Maybe a really long (c) leade (freebore) would help in that scenario (with the boolit seated into the rifling).
I have not encountered any 'paper rings' myself, so I don't understand why you mentioned my loading practice in this particular thread.
But, I'll comment individually on each of the elements in your 'diagnosis'...

(a) My case is fireformed, so the neck is already expanded to fill the chamber cut. The patched bullet is a snug fit in that expanded case mouth, so there is no room for obturation of the bullet's rear section...while still in the case.

(b) You envision the bullet being sized twice...once in the leade, and again when being engraved. The 'leade' IS where engraving occurs. The area immediately in front of the chamber (and case mouth) is the 'freebore', so that would be the 'first opportunity' after exiting the case for the bullet to obturate.
My freebore has the same diameter as the inside of the case mouth...and the same diameter as the patched diameter of the bullet. There is no room for obturation in either the case or freebore, and groove diameter is the same size.

You can rest assured I have no 'gap' caused by a short case, so the only change allowed in the bullet is when the rifling engraves it in the leade.

(c) I don't have a 'really long' freebore, but I do have some. That is why I chose a patched-to-groove bullet dimension, and my bullet (including the leading edge of the patch) does lay well up into the leade angle when chambered.

At least, that's how I imagine things, since we don't have that video to dispell our ignorance...
CM

[docone31]

Charlie, you are right on, except, the ram effect of the pressure curve. This pressure is a solid. All voids will be filled by the pressure however.
If there is a pressure ram, and, the base is flattened, there will be a small ridge outside the exact edge of the boolitt. Kinda like when you squeeze a toothpaste tube. Sooner or later it has to go somewhere.
Rather than an actual ring of paper being shoved in the gap, it is more like powder. The pressure ram forces the material to compress into more dense matter. There would be no tail, as the base of the wrapping goes past the point where the ring forms.
I don't really know how to explain this. I have seen it however in plastic extrusion machines.
The material is rammed forward, there is parasitic forming, not neccessarily in a void. I suspect, the material is extruded into a ring from the pressure, not mis fit. Even rifleing that is tapered into the bore, there can still be rings.
I suspect it might also be size oriented also. The wider the object to be moved, the less pressure is in specific points.
If there was a jump in the rifleing, say .50" then the rifleing begins, with the diameter of the freebore identical to the patched diameter, I believe there will still be a ring at the rifleing junction.
I have absolutely no way to test this, nor am I inclined to make a barrel just to find out why a ring appears. It is fascinating though.
If it was cartridge spaceing, and there was roughness involved as tearing, or shearing, the ring would show feathers, even with the pressure involved.

[leftiye]

CM, I was just throwing out an idea that I had. Many, if not most .45-70 chambers not only have no freebore (yes this is what I meant to say when I typoed in leade - also known as a brain fart), but they also have way oversized case neck areas of their chambers. This was the possibility I was trying to illustrate. If your chamber is minimum, then little obturation is probable. And the best possible scenario that I can visualize for paper patched with either black of smokeless is the long freebore to keep the boolit straight and prevent deformation.

[montana_charlie]

And the best possible scenario that I can visualize for paper patched with either black of smokeless is the long freebore to keep the boolit straight and prevent deformation.
I am not going to disagree with that. As a matter of fact, I hope you are right...because it means the method I am using is more likely to work out well.

But, there is a 'school' of BP shooters that would disagree...and Kenny Wasserberger could be the head master.

If I understand correctly, those guys have chambers that are 'narrow' enough that fireformed cases come out with the ID of the neck at (or only slightly over) bore diameter.

They patch their bullet to bore diameter (which is a snug fit in the case mouth) and place most of the bullet up in the rifling. Only an eighth of an inch (or so) is held in the case.

Besides being 'narrow', those chambers have no freebore at all. The leade angle starts right at the mouth of the case...and it's not a long, gentle 1.5 degree taper.
The butt-end of the bullet comes out of the case mouth, and is up into the fully formed rifling in very short order.

They say (again, if I understand correctly) that this is the way the original Sharps paper patched ammunition was supposed to work. It is what Dan Theodore. and others in that 'school' call a 'P/P chamber'.

I read a more recent post by Theodore where he is starting to work out the kinks of using a chamber WITH a long-ish freebore. Haven't seen any follow-up on that, yet...but it seems he is patching to groove diameter.
CM

[leftiye]

CM I was aware of that, I just don't like bumping boolits up into the rifling. It obviously works though.... If you patch to groove diameter, then obviously the boolit will either be inside the case, or inside of a freebore. With smokeless this is the only way to get the grooves of the rifling filled. With black you'll have to contain the boolit or it will obturate into areas and sizes that may even be dangerous.

[Kenny Wasserburger]

Head Master?

Kinda has a strange ring to it.

Oh my loads btw the bullet is about .420 into the case, and has 3 wads under it. .053 Veg Fiber, used to compress the powder and prevent bulged cases as poly with do with annealed brass, then .060 poly wad, and finally a .091 thick cork wad.
AS MC pointed out my bullets are .446 and then patched to .451 wet patch and dried on a candle warming plate.
All wads are cut on a Cornell wad punch and press setup. All wads are indexed also.

The Lunger

[windrider919]

Leftiye, you asked about sizes. The reamer used was a standard for .458 Win Mag which leaves the fire formed brass with an inside opening of .461. I just bell slightly so as to not snag the patch and insert bullet .250 deep. Then 'crimp' till the brass is straight again, bell removed. No roll crimp because it cuts the patch. My custom bullet for testing smokeless casts .453 with 20-1 ww-tin. I then wrap to .461 because the freebore / throat of my chamber , like most .458 Win Mags is .463. The barrel is a Sheelen match barrel I bought 16 years ago which has 6 small rifling ridges and 6 twice width grooves, 18" twist and is mirror polished. Bore is .450 and groove is (measured) .458.

Bullets have been recovered in a water trough which uses heavy plastic bag to cap the end. Assuming the bullet does not strike the sides at any velocity seemingly perfect bullets have been recovered. The distance is at least 100 yards although if I am shooting a hot load I have backed up to 260 yards [fence line to fence line of the property] to allow the velocity to drop off. Obviously, when testing for bump up a reduced load does not work. So the bullet is fired a full velocity and distance used to slow down the bullet for recovery undamaged. If too hot/fast even water will upset the nose of a bullet. In fact, I feel that this gives the closest check to ballistic gelatin because meat is largely water. Sometimes I have placed loosely bundled newspaper into the front foot of the tank to become saturated and offer more resistance to the bullet. Mostly do this with handgun defense rounds. I get good examples of mushrooms this way and can compare differences. I explained all this to show you that the measurements I get have some reality.

When I shot .446 lead PP to .454 with BP the bullet bumped up to .451 or .452 shank and tail. With perhaps the slight taper towards the nose. The same bullet did not bump up as much with smokeless, it miked .448 and accuracy was not good. I'm talking missed the tank at 100yds bad. Ten shots with only two recoverable. I tried .450 dia swaged bullets PP to .458 and got better accuracy but lots of flyers. Bullets miked out a bump up of .001 or so. Except at the cup base where they expanded out to .455 Note: Jacketed bullets do not bump up at all or just .0005 if that. As per advice from several of you I tried some bullets resized to .454 and patched to fit my throat at .462. Accuracy is excellent at 1" or less, few flyers and only an occasional ring. The bullets do show a shallow rifling where the paper presses down but are untouched in the groove area. When fired at 1800 FPS and recovered the base will mike .455 for the first eight inch or so but the rest of the bullet shank measures .454, unchanged from pre-firing. I have tried to get pictures of the engraved bullet but my camera will not focus down so much.

I have shot other rifles and cartridges into the trap and I think that there is practically NO bump up from firing SP vs BP where you get sizable bump up. I qualify this with this being applied only to flat based bullets. I found that generally cup bases bump up even with SP. Like a hollow based wadcutter or an old Mini ball skirt expands.

By the way, in testing in the tank, backwards 148 gr wadcutters do terrible. Usually the giant opening collapses down one side forming a half arc, like a smile. And punch straight through the wet newspaper like a FMJ, little to no expansion cavity. Or sometimes the skirt separates and leaves a ring of lead a couple inches in and the solid base (really nose) keeps going like a solid .22 does for about 2 more feet. Another old shooters campfire myth busted.

[RMulhern]

You won't get that nasty 'lil paper ring' with a chamber cut like this:

http://i17.photobucket.com/albums/b67/Sharps110/BPCR%20SHOOTING%20RELOADING/Picture_150.jpg

[yarro]

Could some also been related to the thickness of the brass at the case mouth as well? The couple of fired old BP rounds that I have laying around are much thinner at the case mouth than their modern reproductions.

-yarro

[RMulhern]

Could some also been related to the thickness of the brass at the case mouth as well? The couple of fired old BP rounds that I have laying around are much thinner at the case mouth than their modern reproductions.

-yarro

No sir! If anything....the modern thicker brass would be an assist to help prevent the rings because it would prevent the brass from expanding moreso than the thin brass!

The problem comes from having LARGER CUT CHAMBERS than what the 'Old Timers' had and their rifles DID NOT HAVE a 45 degree transition area that exist in modern chambers from the end of the case leading to bore entry!:drinks: