Slugging a bore

[IditarodJoe]

I'm thinking about slugging the bore on my No4 Mk1 rifle (keyholing badly). I've never slugged a bore before. Would the .315 diameter pure lead round balls sold by Brownell's be an appropriate size for this? Thanks. -IJ

[Hecklerusp45]

You want to start with something close to .311 and I don't know of anything sold that is closer than that, so I would give it a try.

[Sunray]

Those will do nicely. Lead being soft stuff the ball will squeeze readily to size. A .308" cast bullet or suitable diameter lead fishing sinker works as well. The thing doesn't have to be close or above nominal diameter. Obviously doesn't need to be an actual bullet either.
Bash it through, preferable from the chamber end, with a 1/4" brass rod and a plastic mallet. Rifle in padded vise.
Montana Bullets sells gas checked 180 and 200 grainers that are .311" to .315" diameter. If you need to go that way. Not stupid expensive either. Roughly $25 per 100.

[Parashooter]

303barrelDims.jpg

Since groove diameter on some No.4's can easily reach .318+", you'll probably want a bigger slug. Size 00 or 000 buckshot do the job nicely and are easily found in 5-packs of loaded shells at reasonable cost. Be sure to use a sturdy steel rod for all but the first few inches. A wooden rod fractured deep in the barrel can be very hard to remove.



If yours is a 5-groove barrel, measuring the slug with a conventional micrometer can be a challenge.

[John Sukey]

Keyholing can be traced to muzzlewear caused by the "pullthrough" causing cord wear at that point.

[IditarodJoe]

Thanks for all the tips! For the price, the idea of using "0" (0.32 in) or "00" (0.33 in.) buckshot is tempting, but I've read that most of it is made of a lead alloy that makes it harder than pure lead. I suspect pure lead would be easier on the barrel. I have to place an order with Brownell's soon anyway so I think I'll start with the .315 lead balls and see what happens. If they don't fill the grooves, I suspect I can try deforming (flattening) one a bit before putting it into the bore. I hadn't thought about it being a five-groove barrel . . . this could be interesting.

John, I'll pull the rifle out take a really hard look at the muzzle and bore tomorrow. It was shooting fine when I last shot it a few years back. Then a few months ago I took it to the range again and it was keyholing every shot using three different types of ammo. Probably could be a number of things.

[Parashooter]

Some buckshot aren't quite pure lead, but they're close enough that it doesn't take more than a couple-three whacks of my light plastic mallet to drive a .360" 000 into a .30 caliber muzzle. Considering that we often fire jacketed steel-core bullets through military rifle barrels with no harm done, it seems a bit over-cautious to fret about tapping in a buckshot. After you've slugged a few, you'll understand.

Using an undersized ball isn't ideal since the impression taken is pretty narrow and tricky to measure.

[IditarodJoe]

Well, I pulled the old girl out and gave her a good look. The bore is fairly dark, and with my aging eyes it's hard to see the lands and grooves clearly but there is a little fine pitting visible. The muzzle crown still looks pretty good and I can't detect any nicks or burrs. In the "bullet test", the bullet of a Hornady Match .303 cartridge leaves about 1/16 inch of the jacket showing. The cartridge wobbles roughly 1/4 inch in one direction at the case head, so I'd say John is right about cleaning wear.

This is a 1943 (Fazakerly) No.4 Mk.I with all the wartime expedients - flip sight, pot metal buttplate, etc. It's still a handsome rifle but it certainly saw its share of use. It probably isn't worth sinking a lot of money into but I'll slug the barrel and see what that looks like. Worst case, I'll either sell it off or just keep it as-is.

At least I'll have learned how to slug a bore! Thanks to all of you for all of your help!

[Nate]

I have had two #4s keyholing because of boat tail bullets . They shoot flat tails just fine. Don't know if may be your problem.

[Johnny P]

As parashooter noted, 00 buckshot works great for slugging bores near the diameter mentioned. 00 is .330 in diameter and is no problem at all to run through a bore.

The Germans used the same method to quick check bore uniformity on military rifles. The bore was oiled, and a led pellet was seated in the bore. The technician then pushed the lead pellet though in one push and this gave him a feel for tight or loose spots in the bore.

[IditarodJoe]

I have had two #4s keyholing because of boat tail bullets . They shoot flat tails just fine. Don't know if may be your problem.

I don't load my own so I'm stuck with what is available in the marketplace. Is there a commercial .303 British cartridge that's loaded with a flat tail bullet?

Both the Hornady Match and the Prvi Partizan that I've shot have boat tail bullets (says so on the box) and they both keyhole consistently. I also have some Remington High Velocity that says it has 180 gr soft point Core-Lokt bullets, and some Federal Classic that says they "feature Federal Hi-Shok and Speer Hot-Cor bullets". Does anyone here know whether either of those would be of the flat tail variety?

[Liam]

I used to shoot the Hot-Core, but thought they were discontinued. They are flat-based and, apparently, still available: http://www.speer-bullets.com/product...g/hot_cor.aspx

[PhillipM]

I'm not sure what slugging your barrel will tell you that your target full of keyholes didn't. Since you say it used to shoot fine I'd try recrowning the muzzle and if that didn't work, another barrel or get rid of it.

[IditarodJoe]

Hehe, well Phillip, I'm not sure either. Before I do anything else, I'll take my old box of Federal Classic cartridges to the range and see how it likes them (thanks Liam!).

Having never slugged a barrel myself or even seen anyone else do it (except in videos), slugging the Enfield would be a learning experience. I'm thinking (always a questionable event) that it might give me some idea of the condition of the rifling. If it looks like it's pretty well shot out, then that would likely the end of it. If slugging indicates that there's still some rifling left, I'll probably take it to a smith to see if counterboring the muzzle might return it to "round hole" status for a reasonable cost.

If I have to slug the barrel, my two primary objectives will be (1) to know a little more than I know now about the condition of the bore and (2) to learn to how to slug a barrel. At least, for the cost of a box of shotgun shells, the price is right.

[Sunray]

Biggest issue with commercial hunting ammo is the bullet comes .311" or .312" diameter, depending on who made it. And Lee-Enfield rifling isn't cut square like U.S. rifling is. More like ( ) and not [ ]. Makes the barrels look less rifled or more worn than they might be.
A No. 4 Rifle was used with a 174 grain BT bullet at 2440 FPS from 1938 onwards. This was the Mk VIII(best .303 I've ever fired was 1944 vintage DA. Stuff was 40 plus years old when we got it. Way better than the IVI crap we got later.) used by our lot during W.W. II and Korea. Any commercial ammo trying to emulate it will be a BT.
A OO pellet will do nicely as well. Just not as easy to measure as a cast .30 cal bullet.
Hornady, Prvi, Speer and Sierra all use a .311" bullet. Hornady does make that .3105 174 grain FMJ as well.
Slugging a barrel is easy. Take out the bolt. Put the rifle muzzle down in a padded vise. Drop the cast bullet/shot/sinker into the chamber followed by the 1/4" brass rod(that's longer than the rifle and barrel) and bash on it with the plastic mallet until the cast bullet/shot/sinker drop out the muzzle. Measure with a micrometer. .311 to .315 is ok. Anything bigger means the barrel is shot out and needs replacing. Mind you, if it's .313 to .315 there are always those Montana cast bullets.