Barrel Profile vs. Acuracy

[Tmas]

I am new at this but really enjoy the comments expressed on this form.

I am working up a squirrel rifle to be used for target shooting.  A 42 inch barrel in 40 cal. 40 cal. because it is the heaviest ball allowed in a squirrel rifle and 42 inches seems to be a reasonable compromise between accuracy and building/handling issues.

Is there any correlation between barrel profile and accuracy?  My form search did not show any comment on this issue. I was thinking that a thicker breach with a moderate swamp would be a good compromise between barrel mass and handling,and a way to have a rifle that would be competitive off hand or from the bench,  Rice Barrels just offers too many interesting choices.

Any comments are welcome, and thanks in advanced

[JCKelly]

I also am interested in this. More specifically, in how uniform is the bore diameter along the length of a swamped barrel?

Suppose I should mess with it myself, with my swamped .40 cal 36" Green Mountain blank.
 
Reason I ask is that the bar stock used has commonly been finished to round in the mill by cold drawing. When that bar is bored to a barrel blank this leaves residual tensile stress on the outside diameter and residual compressive stress in the bore.

OK for shooting, but if you remove material from the surface those compressive stresses in the bore will relieve themselves by an increase in bore diameter.

I have no idea if it is enough change in bore diameter to matter.
Some mechanical engineer better with his math than I could make a good stab at it

So could someone with an accurate way of measuring bore diameter along the length.

I would guess the bore in a swamped barrel to be tightest at the breech, and loosest under the greatest swamp, that is, minimum barrel size across the flats.

Just some thoughts, from one who has been embarrassed by residual stress in steel he filed to shape. . . don't ask

[Mike Brooks]

For off hand shooting it doesn't make any difference, you'll never hold well enough to tell the difference. I'd go with something smaller than a .40 for squirrels.

[Dennis Glazener]

Reason I ask is that the bar stock used has commonly been finished to round in the mill by cold drawing. When that bar is bored to a barrel blank this leaves residual tensile stress on the outside diameter and residual compressive stress in the bore.

For what its worth. LC Rice gave me the nickle tour of his shop several years ago. At the time Rice barrels were made by LC and his brother Liston. One of the things that I saw was a large unit that looked like a large hot water heater. He stood the barrels on end and heat/cool them. Not sure of the exact process but it was to relieve stress from machining.
Dennis

[rsells]

I agree with Mike that you won't notice the difference when shooting free hand.  I also agree that you should go smaller like an A weight in a .32 for squirrel hunting, but I would go with the .40 if my emphasis is on target competition.  I don't have hard test data, but I have been down the road from .29 to .58 and I ended up liking the two cal I mentioned.  When it comes to deer size animals  and larger I go for .54.  Good luck and have fun.
                                                                                    Roger

[Tmas]

Rice Barrels, on their website, makes a point of saying that they heat treat the bored barrels to relieve stress.  This is after they carefully select straight bar stock.

Maybe Jason can chime in and tell us the story.

I sense that swamp profile, both in the 1780s and currently was kept modest enough to not have had an affect on bore dimensions. First, most swamp profiles from the flintlock period are modest, second there does not seem to be any written complaints from either the original period or the modern one.  If there were any problematic profiles, they were discarded long ago.

The safe bet is to use a straight fat octagon barrel.  This is also the heaviest.  I would hate to have a finished rifle and learn that I had made a mistake in barrel selection.

Mike and Rodger:

I agree with both comments.  However I was looking to make a competitive paper puncher.



 

[smylee grouch]

For an off hand gun, I like a 40 in a straight 7/8 atf barrel. For me it seems to be about right with a 36-38 inch length.

[Mike Brooks]

Rice Barrels, on their website, makes a point of saying that they heat treat the bored barrels to relieve stress.  This is after they carefully select straight bar stock.

Maybe Jason can chime in and tell us the story.

I sense that swamp profile, both in the 1780s and currently was kept modest enough to not have had an affect on bore dimensions. First, most swamp profiles from the flintlock period are modest, second there does not seem to be any written complaints from either the original period or the modern one.  If there were any problematic profiles, they were discarded long ago.

The safe bet is to use a straight fat octagon barrel.  This is also the heaviest.  I would hate to have a finished rifle and learn that I had made a mistake in barrel selection.

Mike and Rodger:

I agree with both comments.  However I was looking to make a competitive paper puncher.



 

Having spent many days on the firing line at Friendship I noticed that most of the top shooters were using straight barrels. (And ugly guns  ) I believe that is due to those fellas being tight asses, some never even finish the wood on their guns.
 .40 is about ideal for punching paper IMO. It really isn't ideal for any thing else. You'll suffer some on windy days with a .40, but generally I found holding the gun still on windy days more of a problem then the ball's flight.

[bama]

I aggree with Mike in that the wind will give you more trouble than the barrel profile in a 40 cal out beyond 50 yards. With that being said if you are going to seriously compete then I think you will find that the stiffer the profile the tighter the group. That is why there are so many bull barrels on a full blown target gun. If your going for an all around rifle to hunt with and target shoot then I think I would go with the "B" weight barrel over the "A". You will not gain a lot of weight but it will be stiffer than the "A".

I have found that when I am test firing my rifles that all the barrels today are very capable of excellant accuracy, better than I can hold so I try to build to fit the shooter. I have used everything from an "A" to a "D" and some custom profiles and have not had a bad shooter yet. So build it to suit yourself and then shoot it a bunch and I think you will find that what ever you use it will do well.

[Gaeckle]

One year when we was actively demonstrating rifling at The Ohio Deer & Turkey Expo, one of the vendors happened to be Thompson center Arms, tey had a display of their latest bolt action rifles. As luck would have it, they found our demo very interesting and none of the guys had seen a real hand pulled rifling bench before.....they had heard of them, but had never seen one in use.

In making chit chat and small talk with them, the natural question came to: how does the hole get in the barrel and how does TC rifle theirs? As we were told, the barrels are drilled with a deep hole drill that is specially made to use hydrualic oil to push the chips back out of the hole as it is being drilled, then the barrel is button rifled with a button of the exact caliber selected. The hole is smaller than the button, and when the button is forced through the hole and swedging an imprint onto the barrel's wall it undergoes tremendous force. This causes the barrel to become super brittle.

To solve the brittleness, the barrels are stacked in a special cage in a very specific pattern and then placed in a large oven to bring them up to a specific temperature then slowly allowed to cool. That de-stresses the barrel.

That's what was revealed to us.

I would suppose that the same process is used for muzzleloader barrels. I know the barrels are under certain amounts of stress, but as to what I cannot say. I once watched a fellow at Friendship ream out a Rice barrel and when he was done, the thing had a neat bend in it. The bend was straightened and later on the barrel was hand rifled.

[Daryl]

A 42" x 7/8" straight sided octagonal barrel was a really nice offhand barrel weight for me - in .40 cal.

I did a test some time ago, using an inaccurate load and an accurate load in that Goodoien barrel, shooting both loads benched and then offhand.

The inaccurate load printed about 2 1/2" at 50yards bench and the accurate load, just over 1/2", both 5-shot groups.  My offhand group with the inaccurate load was over 4", while the accurate load printed a 1 1/2" offhand group for me.   I found the results interesting. Yes- it was only one test, but it certainly makes sense.  The difference in groups from bench to offhand, about duplicated themselves when shot offhand - logic, it seems, is proven again.

Thus, I do not believe the premise that there is no difference in offhand groups between inaccurate or good loads.

I quite enjoy however, shooting against people who believe a load's actual accuracy makes no difference in their offhand scores.

If a gun cannot shoot a decent group off the bench, it won't get any better or even the same when shot without a rest. On a graph, the visual difference between bench and offhand, is usually trumpet shaped.

[Tmas]

Great comments and all very good information.  Thanks

Please let me ask a different question, or may be the same question from a different aspect.  How important is overall length?


Darryl, what do you think would be the result of your experiments if you had used a 46 in barrel, with an accurate load, instead of the 42 in.  Rice Barrels offers profiles in lengths up to 48 in.  BTW what caliber was the gun?

I like your comment that improved precision results in improved accuracy both from the bench and off hand even if there is a big difference between the two positions.

I just love this form!

[Scota4570]

"More specifically, in how uniform is the bore diameter along the length of a swamped barrel?"

If it were a button barrel it might make a difference.  I have no clue how significant.  If you want it perfect, or with a choke you will have to lap it. 

If the barrel were finish reamed, polished and cut rifled after profiling it would be more uniform all else being equal. 

[Daryl]

Good questions and complications.

If I was to build an accurate barrel for serous use, it would not be swamped. It would have square-ish bottomed rifling about .010" to .012" deep, not the extra-deep .016 or deeper round bottomed rifling some guys really like.

In thinking of pure accuracy of a round ball barrel, my .69 comes to light - it is absolutely the MOST accurate ML barrel I have ever seen. It is only 31.5" long, and 1 1/8" across the flats - straight octagonal & made by GRRW - having a very slight, not really felt, choke as a short starter puts the ball down 5".

I know of no barrel that comes close. Since I don't see well these days, I have thought of mounting a gizmo aperture sight on the tang - perhaps anchored with with a long tang screw, then see if I can make some more 1" to 1 1/2", 5 shot groups at 100 meters, just because. I know form shooting my Sharps, I still have this capability with apertures.

I would not trust too long a barrel to be consistent enough. That said, my primary rendezvous rifle has a swamped .50cal. 48" Getz barrel with rounded, deep rifling - LOL - for fun shooting and STRUTTIN' only.  For serious accuracy shooting, I still have my short barreled (31.5") .69.

Larger bores are easier to make shoot better AND have better range than the small bores. Sounds logical to me.

[Pete G.]

Thus, I do not believe the premise that there is no difference in offhand groups between inaccurate or good loads.


If a gun cannot shoot a decent group off the bench, it won't get any better or even the same when shot without a rest. On a graph, the visual difference between bench and offhand, is usually trumpet shaped.

Except that every now and then when the planets align and the moon is in the proper phase the barrel will flip one to the right while the shooter wobbles left and vice versa. This results in a 3-1/2" gun shooting a 1/2" group, thus transforming forever that gun into a 1/2" gun. I also once saw a shooter cover a 100 yd. target with shots, but three were within 1/2" of each other and he proudly proclaimed that he had the most accurate rifle on the line because it would shoot a 1/2" group. Strange that these types never enter a match though; they should clean up every time.

[Scota4570]

"- having a very slight, not really felt, choke as a short starter puts the ball down 5"."

I've lapped barrels to be like that, but more choke.  When the short starter gets you past the choke it becomes super easy to load and very accurate at the same time. 

I once use a Numrich 45-70 blank to make a ML.  I lapped the heck out of it leaving a significant choke.  I removed a piece of the muzzle end to make a bullet sizing die.  That left plenty of choke in the barrel.  I then sized plain based bullets.  The lubed and sized bullets loaded as easy as any minie  ball but being mechanically fitted shot extremely well.   

[Daryl]

"- having a very slight, not really felt, choke as a short starter puts the ball down 5"."

I've lapped barrels to be like that, but more choke.  When the short starter gets you past the choke it becomes super easy to load and very accurate at the same time. 

I once use a Numrich 45-70 blank to make a ML.  I lapped the heck out of it leaving a significant choke.  I removed a piece of the muzzle end to make a bullet sizing die.  That left plenty of choke in the barrel.  I then sized plain based bullets.  The lubed and sized bullets loaded as easy as any minie  ball but being mechanically fitted shot extremely well.   

I did much the same to a .50 x 38" twist Bauska barrel back around 1976.  It was exceptionally accurate with TC Maxiballs or 400gr. to 450gr. HB from an old obsolete adjustable Lyman mould.  This barrel/rifle won the 3rd and 4th turkeys 3 years in a row at the Barnet Turkey shoot. The competitors were position shooters using their match rifles. The match was all offhand. There was a 2 turkey limit, and the Olympic "Standing" shooter at our range always won the first 2.


As far as the accuracy is concerned, Pete, G. - my little .69 is not a 1/2 minute rifle for me, any more. I can't see the sights well enough, but - it is still capable of laying down a decent 8-shot bench group with a couple offhand shots thrown in for good measure.

The year I shot noting else on our trail, every week, going through 25 pounds of powder in the process, I placed 1st in every muzzleloading event I entered at Hefley Creek (BC Rendezvous)- so it's ACTUAL accuracy is not in question.



In testing weird loads, double patching and grossly undersized balls, it also shot reasonably well, at 50 yards.

[jerrywh]

 When I was young I had a 40 caliber "squirrel" rifle. The only way I could shoot a squirrel was to bark them. If I hit them it just blew them to fuzz. I would never hunt squirrels with a 40 unless it was a smooth gun full of shot. It was extremely accurate though and had a straight barrel.

[frogwalking]

I had a .32 rifle with a slow twist Douglas barrel.  It needed more powder than one would normally want to use in a squirrel rifle in order to get really good accuracy.  A squirrel hit by it appeared to have had an encounter with a .22 mag (or .22 Hornet) hollow point.  It was a head shot only rifle.

[JCKelly]

Built my first rifle, a truly ugly affair, about 1960 using a round .44 mag bbl from Numrich
Being inclined to use light loads I recall one squirrel dropping like a stone from that ~.42 cal ball. Imagine had I used more powder I coulda got a puff of fur &c also.

[galamb]

Tmas, I'm just an "average Joe shooter", I use my guns primarily for hunting and punching some paper for fun.

If you are looking at something to pop squirrels and shoot a bit of paper, I don't think you will find one profile or rifling style or even a barrel maker significantly (measurably) more accurate then another.

My "current line-up" of black powder rifles includes:

A 50 cal, 7/8" straight (Green Mountain), 36" long, 1:70 square rifled
A 45 cal, Southern Classic swamped (Rice), 42" long, 1:66 radius (round) rifled
A 40 cal, 13/16" straight (Colerain), 42" long, 1:48 radius (round) rifled
A 38 cal, 7/8"-3/4" tapered (FCI), 31" long, 1:48 radius (round) rifled.

So different twists, different profiles, and lengths varying from 31 to 42" long and I am NO Better or NO Worse a shot with any of them out to my (maximum) 75 yard "hunting range".

They will always be capable of shooting "better than I will". I will never shoot enough or spend enough time "getting good enough" that I would be able to answer your question - many of us are in the same boat

PS - I use the 38 cal for hunting Whitetails. Many would cringe at the thought (and I'm not advocating the use of - but in my style of hunting it's both ethical and lethal). Don't sell the 40 cal short - it worked just fine for Bambi, until Charles built me that fine 38 caliber barrel.

[David R. Pennington]

I always only took head shots on squirrels with rifles. Took several with .50 and .45. Take off the head and just leave a flap of hide with ears. No rifles if I were getting them for my grandmother. I had to use shot then because she liked squirrel brains.
Daryl, what do you mean about an accurate and inaccurate load?
I have a 44" swamped Green Mtn. barrel that shoots better than I can hold. Wish it had a better lock on it though.

[Daryl]

In thinking this over some more - I am convinced that for an accuracy gun, one needs to use as short and as stiff a barrel as can be used for the application - but long enough to efficiently burn the powder charge one has to use for the range desired & light enough to shoot, load and carry.

The longer and whippier the barrel is, the more loss in POTENTIAL accuracy. I would think my super thin, 48" A.Verner magnifies the problem of whippyiness.

[Dphariss]

Shooting 30-40 grains of FFF a 32-36-40 will all blow the $#*! out of small game. With 15 grains a 32 just pokes a hole. But is not going to be accurate for top of a tall tree shots. A 50 cal with 20-25 grains will just poke holes in Grouse at 10 yards or so. A 6" 50 cal pistol will just poke holes in Grouse with 40 grains (800 fps).  But a rifle generally needs to make enough velocity to make accuracy. Thus rifles in 32-36-40 are all head shot propositions if loaded to shoot accurately.

Dan

[Pete G.]

In thinking this over some more - I am convinced that for an accuracy gun, one needs to use as short and as stiff a barrel as can be used for the application - but long enough to efficiently burn the powder charge one has to use for the range desired & light enough to shoot, load and carry.

The longer and whippier the barrel is, the more loss in POTENTIAL accuracy. I would think my super thin, 48" A.Verner magnifies the problem of whippyiness.

Also the more dwell time when the ball is still in the barrel, which affects PRACTICAL accuracy, or how the gun can actually be shot. Still, I love those long slender barrels.