Rifling Depth.

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smoothshooter

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Why are the rifling grooves so deep in modern traditional rifles?
Aren’t the deeper grooves less likely to be wiped clean after a shot when he next patched ball is loaded?
And isn’t it harder to get any kind of a gas seal with really deep grooves?
I know that it is not possible to ever get a perfect gas seal.
 
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Why are the rifling grooves so deep in modern traditional rifles?
It is the current fad of customer demand.

Aren’t the deeper grooves less likely to be wiped clean after a shot when he next patched ball is loaded?
Yes- maybe

And isn’t it harder to get any kind of a gas seal with really deep grooves?
Definitely.

In a hypothetical barrel, say 45 cal, anything over 0.010" is deeper than provides best result, IMHO. I have used 45 cal cartridge barrels for MLs. The depth of groove is only 0.004" and they shoot great. They are easier to get to shoot well than deep grooves. TC used button rifle barrels and they are loved by most. They are about 0.006" deep. An advantage of shallow rifling is the ability to shoot Maxi and REAL bullets.

The optimum depth of riffling is caliber dependent.

I bought a deep groove round bottom 45 barrel for my club shoot rifle to see for myself. It was really awful. It never shot well enough to suit me despite dozens of load combinations. It appeared to be leaking gas in the middle of the grooves with any loadable combination. I scrapped it, and replaced it with a regular GM barrel, that barrel is very accurate. IMHO round bottom barrels have no advantage at all.

Another consideration is wide vs narrow grooves. IF the grooves are narrow and deep you will probably have a lemon of a barrel. I look for a 40/60 or better a 30/70 ratio. Narrow lands and wide grooves are better up to a point. IF the lands are super narrow then they are subject to early loading wear.

These days you are lucky to find any barrels in stock. Being picky about these details means having a custom barrel made and that takes time.
 

EC121

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What Scot said!!
Deep rifling is what people have been told they need by the makers. Especially new shooters trying to buy the "best" of everything. Best lube. best barrel, best lock, best screws etc. I have found that the best fix for deep rifling is to use a smaller ball and thicker patch to seal the grooves..
Here is a 50yd. seven shot group using .023 patching and a .526 ball in a .54. One got away to the right. Top hole is another rifle.
Harn rifle group 7shots.jpg
 

ohio ramrod

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I have found .006 to.010 deep groves to be best for prb. I always use a leather over powder wad to improve the gas seal and to prevent patch burning. But that is my personal opinion and worth just what you paid for it.
 

William O.

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Depth of rifling has as much to do with stabilizing a lead conical as does the twist rate. For lead conicals which are heavier and therefore need more powder to get them going, shallow rifling works best. Depending on a the caliber, rate of twist needs to get faster, between 1/32 -1/24. A patched round ball is better stabilized using deeper rifling with slower twitch as the caliber increases. The 1/48 is not a so called "compromise" twist rate and does not allow the use of both prb and lead conicals with equal accuracy.
Also, the depth of rifling and twist rate may limit the length of conical it is able to shoot accurately. I had a Lyman fast twist Hunter barrel (shallow grooves & 1/32 twist) mounted to.a Cabellas stock that needed a 220 grain, 50 caliber conical and 95 grains of 3F to make a holes touching holes group at 75 yards. The groups would open up as the weight of the bullet increased. The addition of a lined fiber wad under the bullet.alwas.improved grouping.
 

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