Slugging a .303 bore

Knottybuoy

Knottybuoy

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OK So I get the general gist of how to slug a bore, but I have a couple questions

What size of lead ball to use for a Lee Enfield No.4?

Where to buy them if you only need it for a one-off time?

And do I fit the bullet using the land or groove diameter?


Thanks
 
00 Buckshot will work fine - cut a 12 Gauge shotshell open and you will have plenty for a few barrels.
Drive the lead ball into the muzzle with a rubber mallet and then drive it down the bore using lengths of 1/4" wood dowel.
Place a rag etc. in the chamber to catch the emerging slug so it doesn't get damaged.
 
If you have an undersize slug you can squish it lengthwise in a vice to swell its O.D. I like a short slug over a round ball, it just gives a bigger area to measure.
 
If your barrel happens to be a 5 - groove barrel, once you have your slug through the bore,
it becomes a bit more of a problem to actually measure it, since a groove will be directly opposite a land.
a V-block will help you out [plus some math, lol]

Most 303 barrels will be between .311" and .3135", but I have seen them as large as .317" [these do not shoot well, obviously]

I have 4 - 303 rifles at present, 2 are P14's, and 2 are M1910 Ross. Both the Ross rifles slug at just over .311", but the P14's are from .3132" - .3135" All shoot jacketed bullets from .3105" to .313" well.

Regards, Dave.
 
I cast 00 buckshot for reloading and use those but cutting open a shotshell would work for around $1. Just make sure it's a cheap buckshot shell; the premium ones are often hardened lead alloy and/or nickle or copper plated which would all be less than ideal.

I had a No.1 Mk.3 that I thought was bad at nearly .315" but my current Martini-Enfield is .316".

A micrometer is your friend with barrel slugs. A caliper is great for case length or OAL but not something requiring the precision of a barrel slug.
 
How about a cerrosafe casting instead?

I went the cerrosafe route about 30 years ago when I got dragged into the Cast Bullet Association kool-aid and the military rifle matches. You can reuse it over and over again, but all the rifles I have done chamber/throat/bore casts on I have kept those castings because occasionally I go back later for a "before and after" look at any changes. That might have helped once in awhile, but usually comparisons mostly satisfy curiosity.

http://www.canadiangunnutz.com/forum/showthread.php/707934-Cerrosafe-alloy-now-in-stock

What is your plan of attack for measurement if that No. 4 of yours happens to have a five groove barrel? I can't help you on that, because the guy who had the jigs and tooling to do odd number land/groove measurements on a casting is now out of the picture.

As far as how to the fit the bullet to the barrel, there's a couple of different views on that.

My belief is that you concentrate on matching the sized bullet to the dimensions you get for the ball seat and leade/throat -the first part of the barrel the bullet enters from the case. I'm among those who think this is where trying to get the best bullet/bore obduration is most important, and if you get it right there it will be good to go for the rest of the barrel. Others believe in groove diameter plus .002", or something similar along the lines of groove diameter plus something; I'm not sure how they determine the largest land/groove measurement over the length of the barrel, however.

If you choose to go the route of measurement by driving a ball down the bore, you won't get the dimensions of the ball seat and leade (and the probably larger dimensions of the lands/grooves at that point if your rifle has some erosion in the first inch or so of the throat) - what you'll get is the measurement of the tightest point in the barrel, not the largest point. If you do a casting, you can get measurements from the chamber, through the ball seat and leade/throat, up into the first part of the rifling, which is where the largest land/groove dimensions will probably be found. You can also do a small casting at the muzzle to see what the measurements are there as well, if you want to compare the dimensions at the start of the rifling to the end. Another reason I like the cerrosafe option.

I'm also one of those who hand lap barrels on rifles that are going to be cast bullet shooters. On rougher barrels like military surplus and old rifles, it can really make a difference. It is pretty simple to do; you just have to be patient and take your time. It really improved the accuracy in my Long Branch, and it turned my grandfather's old 1895 Winchester back into a rifle that would actually shoot a reasonable group (although now it is a .303 instead of a .30 bore once cleaned up). The result is a barrel that is both very smooth and very uniform in dimension from one end to the other - cast bullets in general like that. The first time you do it, you will probably be surprised at the tight/loose spots you find up the length of barrel on the first passes with the lap.

Then, when you get really crazy about it... you start heat treating your bullets to match the pressures of the loads you're using... Lots of giggles to be had shooting really good groups at the range with an old Lee Enfield or Ross with cast bullets, however. Particularly when you're shooting next to some guy with a rifle made of unobtanium and unicorn dust who can't shoot very well...

For what it's worth...
 
Slugging barrels isn't what Cerrosafe is for.
A .30 calibre sized ball(anywhere close to .308") will do. The lead is soft and will expand. Then you measure the lands part on the result. You're looking for the groove diameter.
DO NOT USE A WOODEN DOWEL. Wood breaks too easily leaving a horrendous mess in the barrel. Use a 1/4" brass rod.
 
sunray said:
Slugging barrels isn't what Cerrosafe is for.
Click to expand...
I just checked the directions that came with my last bit of Cerrosafe. Perhaps your directions say that Cerrosafe is not to be used for measuring barrels, but my directions say nothing like that.

Of course, I'm not the guy that first started using Cerrosafe for measuring bores and throats. Lots of cast bullet shooters use this method; it gets written about over on the cast bullet forums often enough. I know there are people who say it doesn't work for them, but there are just as many people who say it certainly does - at least, for those who follow the directions that come with it.

A .30 calibre sized ball(anywhere close to .308") will do. The lead is soft and will expand. Then you measure the lands part on the result. You're looking for the groove diameter.
DO NOT USE A WOODEN DOWEL. Wood breaks too easily leaving a horrendous mess in the barrel. Use a 1/4" brass rod.
Click to expand...
That does an excellent job of giving you the measurements of the tightest point in your barrel. And those measurements can vary considerably - particularly in something like a surplus military rifle with throat erosion.

However, it really doesn't give you the measurements for the largest dimensions in your barrel, which is generally at the throat. I'm of the school of bullet casters that believes you should be paying attention to what the largest dimensions are, not the smallest. Undersized bullets as the bullet exits the case and starts to obdurate increases the chances for gas blow by, gas cutting, leading, and so on.

If I was going to do it with lead, I would use the method of an undersized pure lead slug being swaged up to size in an almost filled case of lead, using a brass rod and dead blow hammer. That will also give you a very accurate measurement of the throat and rifling at the throat, but it is a bit more work.
 
I have all sizes of lead wire, under weight bullet cores, etc. Pure lead slugging bullets can easily be swaged to .311". For the cost of shipping I will send the OP a few 6S ogive flat base Slugging bullets. Slugging a barrel will reveal an open section of rifling inside bore that a borescope might miss.
 
Chinbullco said:
I have all sizes of lead wire, under weight bullet cores, etc. Pure lead slugging bullets can easily be swaged to .311". For the cost of shipping I will send the OP a few 6S ogive flat base Slugging bullets. Slugging a barrel will reveal an open section of rifling inside bore that a borescope might miss.
Click to expand...
That's a pretty generous offer. When you're already casting bullets, there's a pretty good chance you have a sizer, and a .30 caliber sizing dies. You can also partially fill one of your moulds with pure lead and then run that through one of your smaller sizes to prepare it as a slug.

Good point that running a slug down the barrel will show you any loose spots in diameter as the slug moves down the barrel. Forgot all about that.

Knottybuoy said:
Interesting reading, thanks for the replies. I'll probably go with the lead 00Buck to start, will read more into the Cerrosafe method
Click to expand...

cut 'n pasted; pretty much the same as I and most others do it:
The first method involves the use of a metal called Cerrosafe. This metal can be purchased from Brownells, Midway, and other online sources. It melts well below the boiling temperature of water and has near perfect expansion characteristics. To use this method you first must form a plug in the barrel of your firearm. This can be done at the muzzle end by pushing a tight patch from the action end until it is within a couple of inches of the muzzle. Position your barrel vertically in the soft jaws of a vice - leaves you with both hands free while pouring.

Cerrosafe melts easily at 158°-195° F. While the casting metal is still liquid, stir very well, skim off the dross and pour your chamber. The real trick with Cerrosafe is not to overheat it. If you heat the solid slowly, and keep it within the required temperature range, you shouldn’t get any dross. I use a good cooking thermometer so I know, but I doubt many people bother. After melting the Cerrosafe it is carefully poured into the barrel and allowed to cool. With both methods, you lengthen the time you have to pour the alloy and get a good fill by heating the area being cast with a heat gun until almost too hot to hold with the bare hand. Note the time the casting was poured. The casting will take only a very short time to solidify, usually within a minute. Wait 30 minutes and then remove the plug from the bore. Turn the muzzle upward and the casting will fall from the chamber. At 30 minutes after initial solidification, Cerrosafe shrinks slightly, so removal is very easy. Allow the new casting to cool thoroughly then measure the casting exactly one hour from the time it was cast.

The other method of using Cerrosafe is to form the plug an inch or so ahead of the throat of your firearm. This will result in a casting of most of the chamber along with the throat and the first part of the rifling. To get placement of your tight patch right, load a dummy cartridge, chamber it, then push the tight patch down the barrel until it stops against the point of the chambered cartridge. Once again, position the action vertically so you have both hands free. Then pour the Cerrosafe into the barrel from the breech end. Take care and don't overfill the chamber; having good lighting in your work area so you can see the rising level of the Cerrosafe as you pour helps. Again allow the Cerrosafe to cool and set up. This second method will give you the dimensions of your chamber, the chamber throat, and the barrel ahead of the throat. The risk of the second method is if you pour too much Cerrosafe into the breech end of the firearm and it fills in the area of the bolt lugs or extractor, the Cerrosafe isn’t coming out unless heat the action sufficiently with a heat gun or propane torch to soften it up. Another good way to remove a stuck Cerrosafe casting is to use a pot that is large enough to fit the action and chamber into (e.g. turkey fryer), fill the pan with water, heat the water up to boiling and dunk the action into the water for a short time. The cerro safe will melt out and fall to the bottom of the pan. When the water cools you can retrieve the cerro safe from the pan. Boiling hot water and guns... something a lot of the corrosive ammunition and black powder guys deal with every time they go shooting. As the Cerrosafe melts at such a low temperature it isn’t all that bad to have to melt it out of the breech, but it is a pain in the butt. Follow the instructions and you won't have to.

Note here that if you are trying to determine the dimensions a firearm for which you cannot access the breech (pumps and auto rifles for example) then Cerrosafe is not for you. You won’t be able to push the plug out of the barrel end, or pour the Cerrosafe into the breech end of the barrel. For these rifles go to plan B which is described below.

Remember, after the Cerrosafe sets up, BUT BEFORE AN HOUR HAS PASSED you must push the casting out of your barrel. If you used the muzzle cast, push using a cleaning rod from the breech, and vice versa. The reason you must remove the Cerrosafe before an hour has passed is its expansion characteristics. After it is cast, the metal will shrink about .001”, which makes it easy to remove from the firearm. After about an hour, it expands back to the dimensions of the original cavity. Thus, remove it soon, and measure the dimensions after an hour or so and you will have the dimensions of your barrel or all the dimensions for the chamber, throat, and barrel.
 
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