Why do grooves have square corners for fouling?

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  • Last Post 30 July 2019
John Alexander posted this 28 July 2019

It would be a lot easier to get all the fouling out, especially lead slivers, if rifling grooves didn't have square corners at the bottom.

I understand why they are easier to make square for both cut rifling and button rifling but with manufacturers going to hammer forged it would seem at least as easy to make the mandrel with rounded or beveled edges and should not affect the effectiveness of the rifling.

Is this just what is expected to sell rifles or is there a good reason?

John

 

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Ross Smith posted this 28 July 2019

You can get round bottom groove black powder barrels.

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RicinYakima posted this 28 July 2019

I have both a Newton .30 Model 1906 and a Pope barrel with different bottom configurations. The answer is: What is the cheapest way can we make cutters? Now it is traditional, but no good reason. FWIW

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JeffinNZ posted this 28 July 2019

My Colerain MLer round ball barrels are round bottom rifling.  Sweet for cleaning and loading.

Cheers from New Zealand

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Chickenthief posted this 28 July 2019

The first Danish Krag-Jørgensen rifles had an almost hexagonal rifling. It was designed for black powder and jacketed bullets.

It's downfall was that it got worn out way to fast.

Top half is the 8x58RD with compressed black powder charge (72grains with a 8 grain booster charge of lose bp).

Bottom is the modified Metford rifling.

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Lee Wiggins posted this 28 July 2019

   In the original question , I am wandering if the lube grooves in the bullet is what is being asked. Actual square grooves would make it a bear to get the mold to drop bullets but a little angle on the groove fixes that. I think grooves forward of the rear groove which is lubed act as scrapers to try to maintain bore condition. This is just an idea and I don't know if it has merit. Also I might be misreading the question.

   Lee Wiggins 

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Brodie posted this 28 July 2019

The Whitworth rifle and cannon (and the Pedesoleri repoductions of same were all made to shoot black powder and, have/had hexagonal rifling to reduce fouling from black powder.  I could shoot my rifle all afternoon and never have to clean the bore while on the range.

B.E.Brickey

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Brodie posted this 28 July 2019

All the original "Keith" designs had square cornered lube grooves.  I think that it is a hold over from the black powder days.  The grooves were designed like that to hold more lube to prevent fouling and keep the BP fouling soft.There was also the belief that square corned grooves helped to scrape the fouling from the barrel with each shot.

B.E.Brickey

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45 2.1 posted this 28 July 2019

^^^^^^^^^^^ Those grooves aren't quite square, they have a slight draft to them...... at least the "Ideal" molds I have that do have those square lube grooves in them that I've measured and duplicated in some molds.

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RicinYakima posted this 28 July 2019

Truer would be "flat bottom" grooves.

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Ken Campbell Iowa posted this 29 July 2019

... just a comment that sharp cornered cutting or swaging tools wear/break faster, so there must be reasons other than manfacturing cost that results in square grooves in both barrels and molds.

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Hornet posted this 29 July 2019

   Assuming that we're still talking about the actual rifling grooves that John started with, back about 60 years or more ago a barrel maker named Boots Obermeyer made some fame with his 5-R rifling that had very small radii on the inner and outer corners of each rifling land. The claim was that it made fouling much prone to accumulate and easier to remove and many of the shooters using them substantiated this claim. I'm fairly sure that he did not actually create the concept (there's been LOTS of different rifling types) but he did popularize it at the time. I recall seeing a recent ad from a current manufacturer claiming to use 5-R rifling so it may be making a comeback.

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TRKakaCatWhisperer posted this 30 July 2019

Interesting (5R).  When I worked for a machine-gun manufacturer, I talked with a number of barrel manufacturers.  There is a wide variety of forms of rifling.  Sometimes the inside radius would be created by worn cutters - FWIW.

 

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John Alexander posted this 30 July 2019

Seems like a radius caused by a worn cutter, or anything else, would help the shooter trying to get fouling out of the bore.  Maybe the almost universal practice of making hard to clean rifling, even it might be easier not to, is "just the way we do it" which is the explanation for a lot of stupid practices.  

It's OK, us old guys are allowed to be grouchy about minor irritations.

John

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