What am I doing wrong? Slugging barrel.

[Flatlander15]

Hello all, new to any and everything involved with making ammunition. I purchased a 30-40 Krag and want to load the lightest recoiling rounds possible to shoot 50-100 yards, just plinking no serious target work or hunting. The start of my journey begins with slugging the bore. I have yet to get a furnace and whatnot, but have a set of dies on the way, plus 50 unprimed cases from Grafs so it's a start.

I watched tons of videos and read countless tutorials. I lubed up a pure lead fishing sinker, drove it from muzzle to chamber with 7" sections of wooden dowels. I did this twice. Then, I measured with calipers all around the slug. It ranged from .303 to .307 on both. What am I doing incorrectly? The rifling looks fantastic, bright and shiny. Everybody else who has slugged Krags seem to range from 309 to 314. Would a .309 bullet cause too much pressure and present a safety issue?

I'm confused now as to what size bullet mold to purchase. Thanks in advance. If this is in the wrong place I apologize. Feel free to move or delete it.

[ShooterAZ]

I recommend that you not use a wooden dowel. You could get it stuck. You really should use a micrometer, calipers are not generally accurate enough.

[Walstr]

Sorry 'Shooter AZ', but IMHO:
--dowels, smowels, he got the slug thru, no problem
--"digital" calipers are not the best, I would prefer analog dial calipers for any accuracy

Flatlander15: If your barrel has an odd number of grooves, you cannot simply measure the diameter. Your probably having a 'groove' touching one jaw & a non-groove touching opposite jaw. I'm sure there are formulae to correct for this, but a specialized micrometer is typically required. Call some gunsmiths to ask if they can measure your slug. Good question & good luck in your new adventure.

[Flatlander15]

Thank you both. I'll call my most local (1 hr drive) smith on Monday and see if he can check the headspace (Hope he has 30-40 gauges) and bore diameter. Safety is my priority so i'll hand over the reigns.

[wmitty]

Flatlander15

Welcome to the site! To answer your questions:

1. "What am I doing incorrectly?" - the caliper will get you close to groove dia., but you really need a 0-1" micrometer to get an accurate reading.

2. "Would a .309" bullet cause too much pressure and present a safety issue?" - no, you can safely use cast bullets larger than groove diameter.

Since you have been doing your homework, I'd suggest the Lee TL 314-90-SWC as the mould to start with. It should drop as cast boolits large enough to fit the throat of your Krag, and you can tumble lube them and get get started shooting. Three to four grains of Bullseye, 700 X, RedDot or Titegroup will be enough to launch these, and they are accurate enough to be interesting/ fun to shoot.

[Scharfschuetze]

Remember that you are looking to get two measurements from your slug.

1. Bore diameter which is the distance from land to land

2. Groove diameter which is the distance from opposing groove to groove.

I place more importance to the groove diameter than the bore diameter. Use the knife edges of your calipers to get this measurement.

While some are worried about measuring to the closest .0001," I'm fine with measuring to .001" on the groove diameter and then sizing (depending on the sizing dies that I have on hand) at least .001" over that. Generally though, +.002" or slightly more will work out best. With my good industrial grade calipers from the early 80s, I can usually get close to plus or minus .0005" accuracy. Believe me, that is plenty accurate enough for what we do with cast bullets.

Another useful measurement is the neck diameter of the throat. This, after subtracting your brass dimensions in the neck, will usually give you the maximum bullet diameter that your rifle will accept. You can do a search for "pound cast" for the details on this. An easier option, if slightly less accurate, is to measure a fired case neck's diameter and then do the math. Allow a thousandths or two for the brass case's spring back after firing.

Unfortunately, Krag bore measurements can be all over the map so a good slug measurement is a great place to start. My Krag shoots best with a .312" or .313" diameter cast bullet. My favorite cast bullet for the Krag is the Lyman (or NOE) .314299 which goes right at 210 grains depending on alloy or your mould.

As an aside, it looks like your Krag has a VERY good barrel.

[Victor N TN]

You might check area machine shops. Offer them $10 to use a 3 anvil "V" micrometer. It's what's used to measure 3, 5 or 7 flute endmills. Most machine or tool & die shops will have at least one. I don't remember, right now, if I sold mine. I'll check if you want me to. If I do still have it, you can send your slug to me and I'll measure it for you.

[JonB_in_Glencoe]

Flatlander15,
welcome to the forum.

Measuring Lead accurately with a calipers is a tricky endeavor, you need a calibrated thumb that doesn't give more pressure when you've had a couple cups of coffee or less pressure when it's been a long day and you're tired. Using a 1" inside micrometer with a 'slip-clutch' takes all the thumb variability out of the equation, giving you repeatable accurate readings.

Also, if there is an odd number of grooves to the rifling, there is a 'redneck machinist' trick to measuring a odd numbered slug without a V-block. Wrap a strip of aluminum (from a pop can), one layer only, gently around the slug, measure, then subtract two times the aluminum thickness from your measurement.

[runfiverun]

meh your making too much out of barrel diameter.

it's a bolt gun.
get a 30 caliber boolit mold like the LEE 160 2R or the Ed Harris mold from NOE or a copy of the 311284 or 311299 from NOE.
sumthin like that.

make some boolits with some lead like range scrap with a little tin or some old ww's size/lube to .310 and put a check on them.
you'll want to put some powder [red-dot/2400/unique/4895 what have you] and a primer in the case before seating them.
then go shoot them.

if you don't hit the paper then maybe worry about your rifle.

[GhostHawk]

IMO Wmitty nailed it. I happen to have one of those .314 90 grain molds. I have used it in everything from 7.62x25 pistol ammo, .300 BO, 7.62x39, 7.62x54r, .30-30.

In all cases over a moderate load of Red Dot or similar powder it preformed flawlessly tumble lubed with BLL.

In the .30-30 it hit to the same POA at 25 yards as full house 150 grain loads did for 100 making it a no brainer for a quiet small game load in the deer woods.

In the 7.62x25 it solved my small chamber problems of the Cz-52. Rounds plunk as they should.

In the Mosin this is one of my most accurate loads period. Being a honest .314 it fills things nicely.

In the 7.62x39 it is a clear and obvious difference from my other loads. Namely the .312 185 gr gas checked over 20 grains of IMR 4895 intended for the SKS. Making the nice light low noise 4.6 grains of Red Dot plinking ammo easy to spot and shoot in my Handi rifle with the 7.62x39 barrel.

I will be honest, to get the full use out of this boolit you might have to invest in 2 or 3 lee push through sizing die kits. I have a .309 which is seldom used. A .311 that dropped .310 which I honed out to .312 which is great for the SKS, and not bad for the .30-30. And a .314 which you could probably do without.

Slugging is good, fit is king so you do need to master it.
But to a guy stuck on the horns of a dilemma debating the merits of digital calipers vs micrometer is in my opinion really not that helpful.

When all else fails, try it, shoot 5 and see what happens. Heck it is only a 20$ lee mold.

Your mileage may of course vary. Good luck.

[Gewehr-Guy]

Hello Flatlander15, I just yesterday loaded some 30-40 with a type of load that you are looking for. Hornady makes a .314 dia 90 gr.SWC lead bullet, comes in a box of 500, for cheap. I loaded some with 4.5 gr IMR 700x and some 4.5 Unique. these bullets I just hand seated into unsized case necks and they fit quite nicely. Your chamber might be different. Maybe I'll get to shoot them soon.Good choice on your Krag, they are a great cast bullet rifle.

[krallstar]

If you have already fired some rounds thru this you can use your calipers and measure the inside of the neck. That would give you a rough idea as to how large a boo lit you need. But then the freebore might squeeze it down bit. On my moisten, a fired case. Inside neck reads .317 to .318. But the freebore will only except a .316