paper behavior

[wacometalman]

a question that has been rattling around in my head for a while...when a bore size PP bullet expands to fill groves does the paper patch slip or does it tear or stretch to the expanded size of the bullet? not that it matters, just wondering what the consensus is. thanks

[Don McDowell]

The paper expands with the bullet, and then is/should be cut as it travels down the bore. Exiting the muzzle as confetti.
Recovered patched bullets often show the "gap" in the paper as a diagonal ridge the length of the patch, mirroring the ends of the patch as the bullet expanded into the chamber/throat.

[Don McDowell]

When the bullet is wrapped the ends should just meet.
Patch line impression is probably the best description.

[powderburner]

if the patch meets perfectly you should not get a line , the line shows up when you have a gap, from what I can find , but then my catch media is a dirt bank not snow , so it is a little rougher to get it sorted out.

[Kurt]

I would not worry if your paper is short slightly 1/32" under or over lapped. I have found no difference in accuracy as long as you don't get the lap excessive then you will see a little gain in vertical.
I would worry more about how far above the shank into the ogive or below the ogive you patch that bullet. Get it to far above the shank and you will get uneven release or poor release that will effect the accuracy. To low you will smear the bore with the alloy and that will destroy the accuracy.
The bullet profile, alloy and wads are the biggest factor for what goes on down range.
For a PP bullet you can get the alloy to hard as well as to soft. Alloy to hard is worse than getting it to soft. The soft alloy will mostly get nose setback more than a slump. When the nose gets set back you can still get accuracy but the BC will suffer. When the alloy is to hard the bullet will not obdurate enough to seal the bore and you get gas cuts if the wad stack is not sufficient to hold the gas back, but that is not all. The bullet will not obdurate enough to get a good rotation to keep it stable.
Here is a bullet to hard. It did not expand enough to grip the lands.

The next two are the same bullet turned 180 degrees that slumped.

This bullet you can see the patch lap and it also was wrapped to high above the shank.


This prolate bullet has the proper alloy temper to hold the nose setback and it is patched the proper height. You can see the expansion into the grooves and the patch is the proper height to keep the dry lead off the bore wall. One alloy temper will not be the same for all bullet nose profiles. All ogives will react differently.

A GG bullet is much more tolerant to alloys because they most generally start at groove diameter and this helps support the ogive (nose) setback.

Kurt

[powderburner]

Good post Kurt, lots of info and well layed out, easy to follow.

[Frank Savage]

Well, I still consider my experience with 45 cal a limited one (still have to finish my target ML...), but it seems to me that with lesser caliber the importance of avoiding overlap rises dramaticaly. On 32 cal bullet (at 235-255 grs range, 1600-1800 fps) small gap (about up to that 1/32) gives me some less predictable vertical. Just inconvenience about accuracy when you´re not sure if it was fault of your ignoring severe flinchitis or fault of the ammo. An overlap on the other hand, while any bigger than about three thicknesses of the paper opens up the group into wild pattern. I tried it purposely-and the resulting pattern was sure about 3,5 and maybe 5 feet at 65 yds with overlap of 1/32". I had paper too smal for this test...
Edit-sure this can be very different for other rifle

[Kurt]

Frank.

I really didn't see much difference in accuracy when I sent under and over lapped bullets down range.
Here are some I used .44 patches on .45 bullets and the gap is almost 1/8" from left to right---#3 and #7 are underlapped almost 1/8" and you can see it makes it very hard to see the under lap. the over lapp #4 and #5 are hard to see even as large as the photo has amplified the bullets. Even the soft bullets like #2,3 and 5you have to look very hard to see the patch laps.
I don't shoot anything less than .40 patched and even the .390" to .494" I see no difference.

[wacometalman]

thanks for posting pics Kurt, worth a 1000 words. what is your recovery medium?..snow. if it is, how much? living in Texas all we have is dirt!!! but we have plenty of that.