Ok; spring is here; gonna give this another go. Question:

[jonk]

I tried paper patching once last year for the first time. Nothing fancy just .004 inch thick typing paper to start. Double wrapped. Horrible results.

I think I did 2 things wrong. First, I don't think the patches came up high enough on my bullet and some shed off on combustion of the charge. Second though, the tail just wasn't very good looking on any of them, even after sizing through a Lee push through sizer. So that's question one- how long should the tail protrude beyond the base before fold over?

The second question is to save some trial and error. Let's try a little math. Suppose I want to wrap a .309" sized bullet with a double wrap of paper. In determining the patch dimensions, width will depend on the bullet, but length... well see what you think.

A .309 diameter bullet will have a circumference of about .97". Now let's doube that for a double wrap. That would be 1.94" if I'm not mistaken. Let's drop that down a few thousandths of an inch to account for stretch of the wet paper, and say 1.9" might be a good start point. This is for straight sided measurements. If I go for the 45 deg angles, each side would have this length but of course overall length would be a bit more.

Sound good so far?

[pdawg_shooter]

Step 1: slug your bore and throat. Step2: size your bullet to bore size (not grove size) + .001/.0015. Step 3: give the bullet 2 wraps of 16# printer paper. Step 4: let dry, lube, and run through a push through die that will leave the bullet a slight press fit in the throat. Step 5: load and shoot. You can estimate the length of your patch by diameter times 3.14159, times the number of wraps used. I run my patches up on the bullet so they engage the rifling when chambered. With the right alloy there is no upper limit to the velocity you can get with jacketed bullet accuracy.

[runfiverun]

the first mistake i made was in coming up with a 322 sized patch for my 323 sized bbl, seems close?
the 50 yd berm didn't with them.
if they don't come out to the right diameter when done don't even bother to shoot them.

[docone31]

Size your prime casting to .308, then two wraps of .004, length 1 3/16" cut at 45* give or take. Wrap tight, let dry.
Dab a tad of either JPW, or Auto wax on the patch. The lighter the better. Load like a conventional jacketed bullit sans crimp. I found, useing the OAL listed in the book works very well for me.
Start with minimum load data for the gn weight of identical jacketed bullet. The greatest mistake I made was useing too light a load.
The height of most of my patches is all of the nose that is still within bore diameter. If the patch is cut 1" wide, 1 3/16" long, the bottom of the prime casting is about half way on the width. I leave enough to twist the tail enough so it can be trimmed and the bottom still covered.
I played around with my .303 untill the cows came home and were embarassed. With what I learned from that, my .308 was like falling down.
With a casting that small, I use my infamous cigarette roller. I like them tight without tearing.
I dip them in water and soaking wet put them on the apron. I set the casting with the base about 1/2 way. I roll the water off, and the patch on.
Today, patching is all I do for my rifles.

[montana_charlie]

I tried paper patching once last year for the first time. Nothing fancy just .004 inch thick typing paper to start. Double wrapped. Horrible results.
Is your rifling deep enough to cut through two wraps of .004" paper?
CM

[docone31]

I am not about to measue it, but, I wonder if the paper prior to patching loses thickness during the patching process.
My paper is also .004. I use two wraps, and get quite the confetti shower on firing.
With my .308s for example, one is a custom heavy barrel. The other is an Ishapore 7.62. Both produce great groups with the same sizing, and lots of confetti.
I also wonder if there is not some shearing effect, even with paper thicker than the rifleing land. The compression between the compressed body, and uncompressed body on the casting, can intimate shearing merely by the upper layer being sheared.
When there is compression like that, there is compression by the movement of metal/paper.
I am fairly certain, if that effect is in place, it is limited to a very small displacement. If one were to use three wraps of .004, and I am not about to do that, might it not exceed the displacement shearing? Also, as the diameter of the caliber grows, the shearing effect might diminish also. I use smokeless powder. I am more than certain, displacement changes make the casting grow forward, rather than obturate. With black powder, obturation takes place, filling the bore, groove, with slight lengthening.
Again, I might be all wet here. Just some thoughts. I am reasonably certain, the paper thickness pretty much exceeds rifleing depth. Not a lot, but slightly.
The base with remaining twist would be creased to the point of seperation, with friction shearing the base free.
I am not sure it really matters. I have found a technique for me that works. I was always the kid who took everyting apart. I mean everything! I only got my Cox .049 airplane engine back together and ran it. The watches, machines, lawnmowers, etc., untill I hit my teens nothing worked after I "fixed" it. The little airplane engine made one flight however. I crashed it first flight directly into concrete. You get daggoned dizzy with control line flying.

[rhead]

Doc:
The paper does compress a small amount but a much smaller amount than the bullet. In the sizer the paper is acting as a shim to give a smaller effective size for the sizer. The amount the thickness decreases should be in proportion to the hardness 0f the bullet and the hardness of the paper. The paper used will probably vary some in hardness.

[leftiye]

Doc, One of my current theories is that sizing kinda forces the layers of paper into what someone else here called a cellulose sabot. This would start by the wet layers sticking together as they shrink. FWIW This might explain why sometimes thin (tracing) papers don't work as well as thicker, pulpier papers do even when the measurements call for a thinner paper. Kinda like making manila folder paper (though thinner) out of the patches maybe.

[jaydee1445]

circumference = Diameter x Pi (3.141592654) so .309 x 3.14 x 2 = 1.94