Max recommended size over bore diameter?

[rhadamanthos12]

Hello everyone,

I have read the stickies and quite a few other threads here and seen that most people recommend being at 0.001 to 0.0015 over the bore diameter. However I have read a few users that are using 0.002 over the bore diameter. My question as a person looking to get into smokeless paper patching what is the max recommended size over bore diameter? and why?

Thanks!

[Sensai]

I've got nothing to add, but I'm in the same position. I'd really like to get into smokeless paper patching, but it's a little intimidating. I'm presently reading all the stickies, but haven't seen this question answered yet.

[wmitty]

Can't remember where I saw it, but someone had sized up to roughly halfway between bore and groove diameters and was still obtaining good accuracy. I held off for a while trying to take in what I could learn here before jumping in. My suggestion is to get started where you are at with what you have and then work on improving your technique. Paper patching, to me at least, is more forgiving of minute details like sizing to the last .0005" and having the absolute correct patch diameter... it is just not that difficult to have success in your early efforts. Just my .02

[Green Lizzard]

i have tried from .300 to .304 in the 30 cals, i think .301 shades the others by a little (still testing)

[pdawg_shooter]

All but one of my 30cals. like a bullet at .301/.3015. The lone exception is a Marlin 30/30 with micro-groove barrel. It wants .303/.3035 to perform well.

[Dan Cash]

I am patching for one Marlin Microgroove, one Marlin Ballard type rifling and a Winchester 1895 in .30-40 with Ballard type riflling. For all three guns, I size the bullet to .3035 and patch with 2 wraps of tracing paper bringing the assembly to .310 to .314 depending on the paper used and how much it is stretched during wrapping. The result is slightly over groove diameter. These guns will consistantly produce 1.25-1.5 inch groups at 100 yards.

I patch to fill the throat more than the groove diameter. That business of a thousandth over bore works for black powder cartridges with soft bullets. With smokeless, not so much.

[geargnasher]

Dan, I think the OP was referring to core diameter, not final diameter.

The reason I end up doing the same as Pdawg is because I've had consistent failures doing otherwise. Cores at or below bore diameter don't group well at all. Cores in-between bore and groove diameter tend to cut the patch too deeply and lead the bore or just plain don't shoot well. In all cases these were patched to throat diameter and the patch engraved upon chambering. Not snugging the patch into the bore before firing has its own set of issues.

Somewhere around 1-2 thousandths larger than bore for cores, wet-patched to fit the throats, is what works best for me from 6.5mm up to .45 caliber with smokeless powder loads.

Gear

[rhadamanthos12]

Dan, I think the OP was referring to core diameter, not final diameter.

The reason I end up doing the same as Pdawg is because I've had consistent failures doing otherwise. Cores at or below bore diameter don't group well at all. Cores in-between bore and groove diameter tend to cut the patch too deeply and lead the bore or just plain don't shoot well. In all cases these were patched to throat diameter and the patch engraved upon chambering. Not snugging the patch into the bore before firing has its own set of issues.

Somewhere around 1-2 thousandths larger than bore for cores, wet-patched to fit the throats, is what works best for me from 6.5mm up to .45 caliber with smokeless powder loads.

Gear

That is exactly what I'm asking geargnasher, thank you. I just wanted to check on this before I ordered custom sizing dies, so far my slugs turned out as following

• 223 - .218 Bore, .223 groove
• 308 - .3035 bore, .3075 groove
• 30/30 (marlin 336 mircogroove) - .302 bore, .3075 groove
• 45/70 - .450 bore, .458 groove
• 458 win mag - .451 bore, .459 groove

So I was thinking for sizers I need a .219, .303, .305

[barrabruce]

I postulate that a too small core will rattle.
A large one will go where it wants or aligned too.
But a bore rider will centre itself.

[geargnasher]

The paper compresses. If the core is smaller than the tops of the lands, it can't get a good, clean grip on the rifling and isn't supported well enough to stay perfectly straight with the barrel when fired. If the core is too large and there isn't enough thickness to the paper jacket, the lands cut not only the paper but deeply into the boolit itself. Too much lead to steel contact and the effectiveness of the jacket is defeated. There must be a balance.

If the grooves are deeper than .004" or so, the core may need to be larger than what Pdawg and I recommend as a "general" guideline. If they're shallower, the same applies, but the jacket will of course need to be made from really thin paper, like 9 pound or so.

My MG Marlin 336 has .303x309 barrel dimensions. I size cores to .3035" because that's what I have, and patch to .312" because that's what fits the chamber. It works just fine at 21-2200 fps. My .30-'06 had a .301x.309 barrel and a .3108" throat entrance, .3015" as-cast cores didn't shoot well but .3023"cores after lapping the mould did just fine up to 2700 fps, that last half-thousandth made a big difference in accuracy.

For the rifle .45s I just use a Lee .452" or .454" push-through sizer die to take .457-9" as-cast boolits down to a patchable diameter.

I don't patch .22s so I'm not help on that one!

One more thing, for smokeless, use either standard grease-groove boolits or tumble-lube-style boolits and WET patch them so the patch dries and shrinks tightly into the grooves, or what's left of them after sizing the cores down. Patching soft lead and firing with black powder requires a totally different approach, so don't get the two methods confused.

Gear

[pdawg_shooter]

I postulate that a too small core will rattle.
A large one will go where it wants or aligned too.
But a bore rider will centre itself.

A bore rider will work OK...IF the nose section is .001/.0015 over bore diameter. Then you can patch to the start of the ogive. For patching the Lovern design is just about perfect.

[geargnasher]

I had a custom .30-caliber mould made with a .292" bore-riding nose and .302" driving bands and a taper between them to match the throat angle. The patch was stretched when wrapped to be tight on both portions and go over the break in the ogive. They shoot very well and allow a longer boolit to be used without seating below the neck. I had to cut the patch angles differently on each end to keep from getting a pie-wedge gap.



Gear

[barrabruce]

How does such a big section of paper come off the nose of gears pp core when its a few thou undersize.
does it get blasted and ripped off with the rest????

Just curious.
I know it works but.

[geargnasher]

Well, it doesn't work so well with 100% cotton Vellum paper (recovered bore-ride sections have to unwind since they don't get sliced like the full-body sections do, and it affects groups), but Meade "sketch" paper works fine. At 2700 FPS it doesn't stand a chance, all I get is a cloud of powdered fibers out of the muzzle and occasionally I recover an intact disc of paper from the base. If the sun isn't at the right angle you can't even see the fibers in the muzzle blast, "POW!--no patch!"

Gear

[Digital Dan]

An opinion based on patching for a .44 mag and .45-70 for a lever gun and smokeless. Match bullet and bore diameter, patch to groove diameter. I don't size patched bullets or patch GG bullets. They all shoot as well or better than copper jacketed bullets at comparable velocity. The .44 requires a card wad and flat base bullet. The .45-70 don't care, it just likes to shoot.

[Harter66]

My turn I have a 7mm. The cores are at .278 while the finished patch is 286. the bore is .277x.284 . It shoots good groups w/that arangement. I have a high milage 30 cal that shoots fair groups at .310x.3165 in its .315x.305 bbl but will take .320 in the throat and .323 in the case. I've 4 other 30 cals that seem to be happy patched at .301x.309 . Only 1 prefers wet wrapping and for the hunting field it doesn't make enough difference w/in my skillsrange to sweat.

[mikeym1a]

Question for Geargnasher; I have a GEW88, with a .318groove/.311bore. It has the 'S' modification, meaning that it has had the chamber recut for the 'S' bullet in .323, and the throat was enlarged to .326. I have been sizing my boolits to .314, as I don't have anything smaller, and wrapping it with 16lb paper for a finished diameter of .324-.326. I've read that you need to seal the throat to stop gas cutting. I use a collet die to crimp the neck so an not to swage the boolit. However, my boolits are tumbling and striking the target sideways. Is my core too thick? I don't notice any leading in the bore. Any suggestions? Thanks. mike