Revisiting the Half Patch

[303Guy]

Several folks have tried the half patch and now I'm thinking of going the same route. My reasons being the shape of my rifle's throat. It needs a bore-ride nose to get the snug fit and boolit weight I want in it. That being 200+grs. So, I've made my prototype patch and it is now drying. Questions now arise; must the bore-ride nose be lubed? How fat can I patch the boolit base? How far into the throat should the patch go? And others I haven't thought of yet?

[geargnasher]

I think Goodsteel my have more answers than anyone on this, with his dandy patch trimmer and all.....

Gear

[CJR]

303Guy,

I use a half patch on my Lyman 311291 bullet, a nose bore rider, that weighs 175 gr. The Vellum PP goes over the leading edge of the main body but leaves the nose bore riding section unpatched and unlubed. My OAL puts the PP into the barrel lands. This is similar to what the NRA did. I'm getting about an inch or less at 100 yds. at about 2800 fps (with 50-51 gr. W760). I now tumble lube the PPCB with liquid Alox (it's faster) before final sizing and there is no barrel leading whatsoever.

On my 150 gr. LBT bullet( non-bore-rider), I full-length PP up to where the ogive starts. Likewise, accuracy at 3034 fps is identical to the 311291 with no leading whatsoever.

Best regards,

CJR

[geargnasher]

I'm having difficulty "wrapping" my head around the concept of half-patching a one-diameter boolit. 303guy, I know some of your moulds are tapered, but having a bore-riding portion with no step other than the patch makes me worry about the patch peeling off in the throat.

Patching a two-diameter boolit that has a bore-riding section that's patched also (using a high-shrink wet patch, of course) would seem a bit better way to go about it for smooth-sided boolits, but I don't really know. You could also have a two-diameter boolit with just two or three thousandths-over-bore body and patch just over the "step", but that might not work either. I'm interested in what you fellers come up with.

Gear

[303Guy]

Yes, I thought about the half patch slipping. My prototype got a knurling for that reason. I'm also thinking of using 100% cotton tracing paper the really shrinks tight. Initially, I think I'll try soft alloy which theoretically grips the paper as it enters the tapered throat. Nothing stops me from trying a two-diameter mold with a sharp transition for the purpose of gripping the patch.


The Vellum PP goes over the leading edge of the main body but leaves the nose bore riding section unpatched and unlubed.I can't achieve those velocities and pressures in my Brit. Would vellum work OK at Brit pressures? What boolit hardness do you use and what is the twist rate? Is that a 30-06?

[longbow]

Not quite the same thing but I tried turning the base bands of a 316299 to 0.304" leaving the front band intact then patching the reduced portion back up to groove diameter.

The idea being to have the patch inside the neck and the front band leading the way to protect the leading edge of the patch.

Not only were they a pain to roll patched on but they gave poor accuracy. I was actually a little surprised because the 316299 shoots very well from my gun and the nose and front band were still there to guide.

Anyway, that one flopped big time!

I think you might be better off to use a two diameter boolit with base diameter about 0.001" over bore then patch to groove and the nose diameter such that when patched it is a thou or two over bore diameter.

That should allow you to run the nose into the bore, or at least patch touching the rifling, and would ease the patch into the leade where the boolit diameters transition.

Just a thought.

Longbow

[geargnasher]

+1 Longbow, that's what I was thinking. I've had good success with a patched bore-rider if the nose portion is the right size to be .001" or so over bore diameter when patched. The only issue I can forsee is using a weak enough paper to shred right at muzzle exit, since the rifling won't be cutting the patch on the nose portion of the boolit. Here's a pic of recovered patches to show what I mean:

http://castboolits.gunloads.com/imagehosting/thum_89094e013fb0b7377.jpg (http://castboolits.gunloads.com/vbimghost.php?do=displayimg&imgid=1265)

Note the large triangles that were wrapped around the nose, compared to the cut pieces that were in the driving band area. This was 100% cotton vellum, very tough paper at way over .303 British velocities.

Gear

[303Guy]

Thanks. Well, I do have a two-diameter sizer which produces a bore-ride patched boolit. It did give some signs of promise but I am unsure of the subsequent poor results it produced. That's why I took up the idea of a half patch. Well, the only thing to do is run full patch two-diameter and half-patch bore-ride tests simultaneously. I'll eliminate the loose seating as a first step. I do actually have a neck sizer that gives a little grip on the PPCB's. (I think? If I don't I'll make one).

It does occur to me that the less than tight seating might be the culprit.

[pdawg_shooter]

Never had any luck with half patches. I lap my bore riding molds to .3015 in the front part, size the back part the same and patch full length. Works for me anyway. My problem with any bore riders is if the nose isnt supported fully it will distort under acceleration. If it doesen't distort uniformly, no accuracy. If you patch full length the entire bullet is supported and leaves the barrel concentric.

[CJR]

303Guy,

I don't see why Vellum wouldn't work on your 303 Brti. It's very tough paper. My PPCB are used in a standard 308Win that came with a factory free-bored chamber. My measured CB hardness is 15BHN. Though my 311291 CB is a two-diameter bore-riding design, there are a number of photos in the NRA's Cast Bullet manual where a half PP was used on the one-diameter NRA designed PPCB. If you don't have a copy of the NRA manual, go to Castpics and download their scanned copy for your usage. It contains a wealth of info!

Best regards,

CJR

[barrabruce]

CJR.

Could you please post a link to the NRA's manual

I have tried several times and can't seem to find the forest for the trees.

It appears my male domestic blindness has started to effect my vision in other areas as well.

:(

Barra

[CJR]

Barra,

Go to Cast Pics/Articles/Classic Works. At the bottom of the list, download TWO(2) references; i.e. "NRA Cast Bullets by Harrison" and "NRA Cast Bullets Supplement 1". These are both outstanding works!

Best regards,

CJR

[barrabruce]

Got'em thanks CJR

Cheers

[CJR]

Barra,

Study that manual and supplement. I'm going to give you a pop-quiz in a couple of days!

Best regards,

CJR

[jhalcott]

HMMM! I went to castpics and tried to down load those two references. It LOOKED like it was working. Then I got Could not render the page! ? Neither of these will open on MY computer.

[geargnasher]

I was having trouble with that the other day too, but with a different article. The NRA manual loaded fine with Foxit Reader.

Gear

[303Guy]

I found and successfully downloaded the files - thanks. At a first glance I saw some interesting stuff! Pressure graphs with different powders and charges - interesting!

I also saw listed scans of Howe's two volumes of "The Modern Gunsmith" - I have those volumes! :-D

[barrabruce]

Well after reading the Downloaded files i have come to the realisation that I have just about copied the NRA approach to paper patching with out the knowledge of there efforts and virtually come up with the same hypothesis and results. Being it adjusted accordingly for not having match barrells and fancy gear to play with.
I feel that I have done well so far.
If I can get my gun to shoot again as good as before then I will be happy with it.
Maybe I can play some more and see once I get it back shooting again.
( I had to make a new firing pin and the barrell fit in the action adjusted in me H&R single shotgun type thingo and its shooting differently now. I have just rebedded the fore-end in a different way and hope this gun likes it like that now.)

The only major difference from the NRA's that I do different is I don't use teflon or good paper and my neck tension is just finger seatable.

I think that I get issues with 4x wraps of cig papers in the fact that the Alox can grip the neck or chamber and tear the thin paper off as a little chunk here or there creating problems.

I shall see. If I ever get to 1 moa at 100 yrds I'll lets you's know but with the inbuilt variables in my castings/dies and such even with full indexing I may be at best get reach the my best as before about 1 1/4 moa at 100 yrds spreading with distance!!!
I will have to re equip myself if I want to try anything at long range say 3-500 yrds.

Barra

[grullaguy]

I'm having difficulty "wrapping" my head around the concept of half-patching a one-diameter boolit. 303guy, I know some of your moulds are tapered, but having a bore-riding portion with no step other than the patch makes me worry about the patch peeling off in the throat.

Patching a two-diameter boolit that has a bore-riding section that's patched also (using a high-shrink wet patch, of course) would seem a bit better way to go about it for smooth-sided boolits, but I don't really know. You could also have a two-diameter boolit with just two or three thousandths-over-bore body and patch just over the "step", but that might not work either. I'm interested in what you fellers come up with.

Gear

Geargnasher's post got me thinking about my tribulations trying to get my Lee C309-180-R cast bullets to print on target when patched. At a gunshow last week, I had the opportunity to pick up a used Lee C309-200-R mould. I looked at the cast 200 grain bullet and it became obvious to me what a bore rider bullet is.
You see, when I started patching some 4 months ago, I was new to casting and had no idea what a bore rider was. I should have asked someone.

It had never occurred to me that my patching to the ogive with too thick of a paper that my bullets were being pushed down into the cases on loading. True my paper was touching the lands, but my bullet was all askew in the casing.

I got some onion skin paper from the stationery store and did some half wraps. They chambered fine with the bore rider section easily seating into the barrel lands. However, I am shooting bullets intended for .308 diameter guns, I measured the bore rider section and it was .300. Hmm not very good bore riding in a .303 barrel.

Enter the bore three quarter patch:

http://i1115.photobucket.com/albums/k554/boolitcaster/PA210358.jpg

Some trial and error and range time, got me a patch that supported the nose section and provided a good seat at the back of the bullet. Suddenly, I am shooting 2 and 3 inch groups at 100 yards. (about as good as I can shoot with factory ammo).
Now with this unusual patch, I am wrapping the .309 bullets and only doing a final sizing to .314 before loading. Pretty easy compared to all the other steps I had tried in the past.

[303Guy]

I like it!:idea: Thanks for posting.

I have a bore-ride boolit that fits on the nose but is undersize on the base shank with two wraps. You can see what I'm thinking.;)

[303Guy]

I've had a half patch boolit lying around for a while now so I decided to shoot it out my trumpet bore. It was a light load so I could recover the boolit. What surprised me was that the boolit had bumped up to fill the grooves. Also, there was no rifling skid or patch cut through. This was a nose ride boolit with the un-patched nose section riding snugly.

http://i388.photobucket.com/albums/oo327/303Guy/FIRE-POLISHING001.jpg

There was a little lead in the muzzle section.

This shows how the paper grips the core, by its rough texture.