• Friends, our 2nd Amendment rights are always under attack and the NRA has been a constant for decades in helping fight that fight.

    We have partnered with the NRA to offer you a discount on membership and Muzzleloading Forum gets a small percentage too of each membership, so you are supporting both the NRA and us.

    Use this link to sign up please; https://membership.nra.org/recruiters/join/XR045103

Another Barrel Question

Muzzleloading Forum

Help Support Muzzleloading Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.


36 Cl.
Dec 2, 2022
Reaction score
Good Morning,
As I said in previous posts, I’m in the process of picking up a new rifle, and I’m trying to get a good understanding of the basics before I make a purchase. I’m curious if barrels on custom rifles usually have a standard size for certain calibers. I’m thinking the sizes are measured by the width of the flats. Most of my experience has been with production rifles; 36, 45, and 50 calibers. One thing I noticed in many cases was that it seemed one size barrel blank was being used for different calibers. Example, I had three Kentucky Juker style rifles. One in 36, one in 45, and one in 50 calibers. They all appeared to have the same barrel. So, the lightest was the 50 followed by the 45, with the heaviest being the 36. Now I can understand them doing this to lower costs, but I bought the 36 to have something light to shoot and due to the weight, I didn’t like it. (I’ve also experienced this in cap and ball revolvers. I had an 1861 signature series Navy, and the barrel was smaller in diameter than an 1860 Army. My friend had a regular 1861 Navy and it looked like it had been equipped with an 1860 sized 36 caliber barrel, probably to save manufacturing costs.) So, in the non-production muzzleloading world do you see the same thing or do smaller calibers have slimmer barrels? I ask this question because I am seriously considering a smaller caliber rifle. I guess some folks like a heavier barrel for target work, but I want something light in weight and caliber. I did some searches in previous threads but really could not come up with any answers, although I did learn some of the flat sizes. I think an obvious answer here would be to call the custom builder I plan on using and ask him. The problem is I do not see myself having a custom built. I would probably buy a custom already built at one of the muzzleloading shows. I’d like to know what my options are before I make a purchase.

Any advice would be appreciated,

Resolve, many newcomers to the ml game, like yourself, have difficulty separating what they see in factory made rifles and modern guns with what was used in centuries previous or current made custom reproductions. In this game, there is no "standard" of almost anything. If you choose a custom made repro from a reputable builder be sure you are willing to accept what he recreates. Or, you can tell a builder to make what you want without regard for historical correctness.
You are right, straight sided barrels are measured across the flats. Most common sizes are 15/16, 7/8, and 13/16. In terms of weight the smaller bores are better in the 13/16. A .32 bore in a 15/16 barrel would be HEAVY. All rifles with straight sided barrels are going to be front heavy with the balance point well in front of the rear sight. Many shooters like this as they feel it helps stabilize them on target.

The only way to get around this is to go with a taper and flared, or "swamped" barrel which is thick at the breech, tapers down to about 2/3 the way down the barrel, and then has a slight flare at the muzzle. This type of barrel in a rifle will have a balance point at or behind the front sight and although it may not be any lighter than a straight sided barrel, it sure feels lighter in the hand.

The down side is that a swamped barrel is much more expensive, and are not used by any modern factory rifle. You have to build yourself from scratch or a kit, or get a custom builder to make you a rifle.
Most custom rifles have a "swamped" barrel that are tapered and flared, wider at the breech, narrow at the waist and flared at the muzzle. These come in different profiles we call weights. An "A" weight barrel is very slim and used for rifles from .32 to .40 cal, a "B" weight barrel will go up to a .50, a "C" weight will go up to a .58 and a "D" weight will go up to a .72 or 12 ga.

Within the weights there are differences in the degree of taper and flare for different styles of rifles.

Straight sided barrels start at 3/4" and go up to 1 3/8" depending on what caliber you want.

Get a rifle with a swamped barrel, they balance so much better.

Look at the Rice barrel page to get an idea of what I am talking about.

Great explanations have already been given. I'll just add that for hunting or an all around rifle absolutely get a swamped barrel. A straight barrel generally belongs on the target range. I have 4 swamped barrels and 2 straight barrels. The straight barrels are on rifles that are very light and handle wonderfully.

There's a good bit of uniformity in barrels made in the past 50 years, but this was not always so. The old time builder made the barrel and made a mold for that particular barrel. Even today you can have a .50 with the next one off the line being a "tight" .50. Many .45 barrels are actually .44s and other caliber barrels that are suppose to be .54 but are actually .53. This isn't the problem one might think. If a particular bore is oversize a thicker patch is used or a thinner patch with a tight bore.

It's actually not as complicated as it seems. Just get a swamped barrel and a mold for the putative caliber and you'll do fine.
Thanks folks, good info that cleared up any questions I had. Now I know what options I have when I get down to buying.
Have a good night,