Deep rifling for rbs. Really???

[Skychief]

Want to share my thoughts of the day after shooting all day with a shallow grooved rifle.

My thought is that the common idea of needing deep rifling for shooting round balls accurately, May not be entirely true.

I shoot the rifle in question as accurately as any of my others that have much deeper grooves. It hit a pie plate at 150 measured yards with great regularity from the bench. Ended the session with 8 hits in succession at that range.

An added bonus of the shallow grooved bore is that cleanup is quicker and easier.

Just my thought of the day after shooting a hundred rounds with a friend.

What say you?

Best regards, Skychief.

 

[galamb]

If I'm remembering correctly, my Lyman Trade Rifle had rifling about .008" deep with it's 1:48, 28" barrel - It hit what I aimed it at.

My 31" 54 cal Oregon barrel was custom ordered at 1:48 with .010 rifling - it hit what I aimed at.

My 36" Colerain and 42" Rice barrels are round bottom rifled at .012 and .016 respectively in twists of 1:48 and 1:66 - and guess what, they shoot just fine too.

Ooops, almost forgot my 36" 1:70 Green Mountain, .010" square rifling that I only shoot conicals with also hits the target.

Now, I have never tried a round ball out of say a .004" groove depth fast twist barrel, but suspect you could hit a target with that too if you horsed around a bit.

So maybe lot's of combo's will work, but perhaps if maybe your life depended on it, after enough trial and error, you might find that the deeper groves just may tend to extend your "life expectancy" ?? :idunno:

 

[zimmerstutzen]

A pie plate at 150 is good
But wouldn't get noticed in a bench match.
In addition there is so very much more than just rifling depth. Round bottom square bottom, groove width, twist gain twist, progressive rifling, Pope style, Alex Henry style, forsyth,
Just saying shallow means relatively little.
Even in round bottom, what arc cut? Most makers use a radius less than bore diameter. Some use a radius two or three times the bore radius, which cuts rifling grooves that are deeper along the lands than in the middle of the groove

 

[zimmerstutzen]

So what is the twist?
Square bottom or round?
What is the depth?
What is the ratio for the width of the lands vs the grooves?
How many grooves?
What is the bore diameter groove to groove?
What is the bore diameter land to land
When you supply these we will be getting somewhere.

 

[Skychief]

Thanks for your replies Zimmer'.

1:48".
Square.
.009 (deeper than I supposed).
1:1.
8 grooves.
.472.
.454.


More measurements....

3/4" across the flats.
27" in length.
Blade front sight.
Square notch rear sight.


The rifle bears little resemblance to a dedicated bench rifle. Thanks for pointing out that it's shooting today wouldn't bear mentioning at a bench match as some here might not have realized this.

Best regards, Skychief.

 

[galamb]

Hmmm, sounds like a fairly "typical" round ball barrel.

Not super deep rifling but certainly not what you could call "shallow" rifling - at least .004 or so is what comes to my mind when someone says "shallow".

 

[tenngun]

I had one of those navy arms zouaves back in the 70s. Shot minnies ok but shot .562 ball in .15 patchs real well on lower powder charges. I dont think I ever shot more then 100 yards however.

 

[Zonie]

Mention was made of shallow grooves and fast twists.

I know it's a stretch but the barrel on my Schuetzen which is made for elongated slugs has a 1:18 twist and the rifling grooves are .0015 deep.
The bore is .4000 diameter.

It has no problem drilling multiple shots into quarter size groups at 100 yards shooting paper patched bullets (if the shooter does his part).

My problem is those paper patched slugs are expensive and I've only found one supplier for them.

With this in mind I thought, "Why not try some .390 diameter roundballs with some tight patching? That would be cheap and make the nipple last longer too!"

With roundballs and patches in hand I tried it at the range at 100 yards. Shots were all over the place.
At 50 yards I was doing good to hold a 8 inch group and this is shooting with a peep sight!

I messed with powder loads and lubes and even tried some looser patches. Nothing I did made it shoot much better than I would expect from a smoothbore with good sights.

Just thought I would give my experience for you folks to think about.

 

[S.Kenton]

My opinion is a pie plate at 150 yards off a bench is GOOD! I shoot a colrain round bottom groove barrel..never tried a pie plate at 150. My guess is it's not that easy, when ya figure in the windage and other variables.
Just my 2 cents..

 

[Wes/Tex]

I had one of those navy arms zouaves back in the 70s. Shot minnies ok but shot .562 ball in .15 patchs real well on lower powder charges. I dont think I ever shot more then 100 yards however.

The Zouaves from Zoli is where the knock came about shallow rifling and 1-48" twist. Even these rifles can be made to shoot as Tenngun states. It took awhile back in the 60's for us to realize what was happening. Minie ball barrels are only .003" deep with the rifling...even worse than that is each land or groove is 1/6th of the total bore surface. These guns have only 3 lands and 3 grooves...total. Outstanding for Minie balls but the patches have difficulty gripping a bore like that at high velocity. When we started using tight ball/patch combos and lowered charges closer to the 60 grain Minie ball load, things got happy around the range! Depth, to my mind is less important than numbers of lands and grooves to give the patch something to grip. Unfortunately, the story got out about 1-48" twist but it was the wrong story and is still repeated to this day. The most obvious proof to the contrary are the, yes, I'll say it, Hawken boys in St.Louis. Same twist rate but .010" or deeper cut multi-groove rifling, en voila...instant success. Somebody help me off the soap-box! :wink:

 

[zimmerstutzen]

Exactly shallow rifling can shoot prb with some accuracy, generally it requires a tight combination and mild powder charge.

Years ago a fellow here built a rifle out of a modern 38-55 barrel. However he shot very low charges, 10 or 15 grains even for 100 yds. He won a great many matches. Unless it was windy

 

[Skychief]

Did you see the specs of my barrel Zimmer'?

I will add that the rifle was loaded with 45 grains of 3f Scheutzen and a .020 spit lubed ticking patch cut at the muzzle.

 

[Rifleman1776]

As others have indicated the number of variable rises considerably with shallow groove barrels. I shot one at one time and found ball/patch combo was far more difficult to work out than with a deep groove barrel. And, finding a good thin cloth for patching was near impossible. Several of us were on this quest and we ended up using airplane cloth. Great stuff, very-very thin and incredible strong pure cotton. Worked great. Problem is, I don't believe it is available anymore thanks to the FAA as it burns and they don't like airplanes burning up, even antique ones.
OTOH, I'm happy yer happy. :grin:

 

[roundball]

What say you?
Best regards, Skychief.

Couldn't agree more.
My T/C factory 28" shallow groove Flint barrels in .45/.50/.54cals all shot 1+7/8" to 2+3/4" groups at 100yds benched.
90grns Goex 3F, .018" pillow ticking, Hornady .440"/.490"/.530" balls.

But before these tests, after reading all the hype on forums like this one, that deep groove barrels are much more accurate, I upgraded all 3 shallow groove barrels to T/C's longer "deep groove round ball barrels"...didn't notice squat of a difference.

And as an aside, during this testing I also proved to myself that the oft repeated comment that stout loads in shallow groove barrels will cause the PRBs to skip / strip the rifling to be an old wives tale.

 

[zimmerstutzen]

As sky chief found, his "shallow" was not so shallow. In order to put you testimonial in perspective, give us the answers to my above questions. Otherwise your post means little in substance. As I recall the first Tc barrels "shallow" was in fact .006 meant as a compromise rifling to shoot both prb and conical projectiles.

Whether there is a measurable difference in accuracy can be measured over a series of targets but to truly measure requires sights far better than the hunting sights Tc supplied.

My experience going from my Tc with peep sights to an H & H target barrel with open sights, the groups shrank to half at 100 yards. There was an additional 6 inch sight radius.

 

[TFoley]

I know it's a stretch but the barrel on my Schuetzen which is made for elongated slugs has a 1:18 twist and the rifling grooves are .0015 deep. The bore is .4000 diameter.

It has no problem drilling multiple shots into quarter size groups at 100 yards shooting paper patched bullets (if the shooter does his part).

My problem is those paper patched slugs are expensive and I've only found one supplier for them.

With this in mind I thought, "Why not try some .390 diameter roundballs with some tight patching? That would be cheap and make the nipple last longer too!"

With roundballs and patches in hand I tried it at the range at 100 yards. Shots were all over the place.

At 50 yards I was doing good to hold a 8 inch group and this is shooting with a peep sight!

I messed with powder loads and lubes and even tried some looser patches. Nothing I did made it shoot much better than I would expect from a smoothbore with good sights.

Just thought I would give my experience for you folks to think about.

That's why RB rifles usually have long, lazy twists, as you yourself have often pointed out.

tac

 

[hanshi]

A good example of a "long, lazy twist" would be my US M1841 Ms rifle. The twist is 1-66" and the rifle was designed to shoot prb, not mini ball. The grooves are, if I'm not mistaken, .006" which is shallow but not overly so. Even with heavy loads (it's a .54) it will shoot around an inch at 60 yards. It likes a thin patch but .015" patches will seat without undue effort. Ball size is .530" and loads of up to 110 grains of 3F pretty much go along with what rb said about shallow grooves and high velocity; they can be made to shoot and shoot very well.

 

[Vaino]

I agree that .016 deep rifling isn't necessary and in fact can be detrimental to load efficiency.

If one calculates the patch thickness to just fill the grooves and then increases patch thickness by .006 {.003 per side} to ensure groove obturation, the patch thickness is to the point of hard loading....especially w/ a fouled bbl.

To me, a rifling depth of .010-.012 would work a lot better asre load efficiency. Good accuracy is another requirement and on that I'd have to take an educated guess asre .010-.012 groove depth....although w/ my .50 TC Hawken, which has shallower rifling, the accuracy is excellent.

Don't know why RB bbls from most manufacturers have .016 deep rifling......Fred

 

[Skychief]

Not to get off subject, but, does anyone know groove depth of a T/C Hawken?

 

[roundball]

I understood my standard T/C factory barrels were .006"...never slugged them but that looked right...anything less becomes almost non-existent.