Does keeping the ball subsonic help with accuracy?

[Bo T]

I was thinking of a 28 but I am finding that a 24 or 20 might be the one that I stumble on. A little recoil sensitive in my inclining age and keeping things subsonic will reduce the recoil.

 

[Artificer]

Keeping a ball subsonic may be best for an accuracy load, but I am not sure about that as I have never actually chronographed accuracy loads.

I do know that with both PRB's and Minie' Balls, in rifles made with barrels respectively rifled for either ball type; that there is always a light target load that shoots best for short to moderate range accuracy and then another load with a heavier powder charge for accuracy when hunting.

A couple of examples. In my .45 Cal., douglas barreled, flintlock rifle; my accuracy load is 42 1/2 grains of FFFg to punch paper out through 50 yards, while my hunting load is 70 grains of FFFg. Many NSSA shooters I knew used between 28 to 32 grains of powder in their Civil War period or repro rifle muskets for target/paper shooting, while the original "Service" load was 60 grains.

Gus

 

[necchi]

I don't know what your 28-24-20 means,,?
Like CF there can be several "Nodes" of accuracy found in any rifle where things all come together and provide good accuracy.
That said, Will sub-sonic help? No.
Champion match shooters (where accuracy is the utmost goal) almost to a man use some pretty stout loads.
Even without a chrono to prove it, you can hear the sonic "crack" of a fast load vrs a "boom" of sub-sonic at discharge

 

[Artificer]

I'm fairly sure he is talking about Gauges of a smoothbore gun, but he could be referring to bore size in a rifle by the older way of measuring bore size.

Gus

 

[fleener]

there are folks that think as a bullet goes to subsonic while in flight that it causes the bullet to become more unstable.

If you need to shoot a lighter load for recoil reasons you might want to consider getting a smaller cal. Say something like a .40 cal. You can shoot it all day and recoil most likely will not be an issue.

Fleener

 

[Pete G]

When a bullet becomes unstable it begins to yaw about its centerline. A round ball does not do this. I agree that if you want less recoil you go with a smaller caliber. Less powder weight, less ball weight and in most cases more rifle weight will all contribute to less recoil.

 

[jethro224]

The theory is that when a fast ball eventually slows down to sub-sonic speed the sound wave will catch up to it and slap it around as it passes causing it to lose stability.

If recoil is your main concern go with the smaller bore. A 28 loaded to the same velocity will recoil less than a 24 or 20 just due to the weight of the ball and the fact that it takes less powder to get it to the same speed. It will also shoot flatter so should have the potential for better accuracy, all other things being equal.

 

[mooman76]

If you already have the guns, try them with low charges and see if the accuracy is good enough for what you want.

 

[Bo T]

Yes, the reference is to gauges, but I suppose I could have used the 54, 58, and 62 calibers instead.
Somewhere up stream a large dose of Scottish blood was bequeathed to me, causing a certain amount of frugality. So I would like to go with the 28 gauge smoothbore coupled with a .54 pistol. But, if the opportunity to pick up a 20 or 24 gauge at a good price presents itself before then, I'll be hard pressed to resist.

 

[jethro224]

So I would like to go with the 28 gauge smoothbore coupled with a .54 pistol.

It's a good plan. I have a 28bore (.550) long gun, a .54 rifle, and a 28 smooth pistol that can all be loaded with the same .530 ball and ticking patch. It works out great. :thumbsup: One bag for 3 guns.
By happy coincidence the rifle and smoothbore even like the same powder charge.

 

[M. De Land]

That is absolutely true of bullets but I know of no data of the effect of transonic flight of a ball.
That is one of the main reasons folks who shoot mid and long range matches (600 to 1000 yards) try to keep the bullet supper sonic as far down range as they can.
The bullet is most effected by drift in it's flight down through about 950 fps as the shock wave moves off the nose and down the body.
Wind not only reacts to the physical bullet but to the pressure wave enveloping it as well.

 

[RAEDWALD]

Download Dr David Miller's doctoral thesis on the 17th century matchlock's internal and external ballistics (public document) via https://www.google.fr/url?sa=t&rct=j&q=&esrc=s&a... worth it just for the read.

His findings on spherical ball obturation is something I have never seen found before; though OT and probably shows up my ignorance.

In particular he looks at just this question (and many other valuable ballistic things for smooth bores etc) and clearly shows that the transonic area is where great instability occurs and you either want to be well below it or well above it for consistent flight. One of the reasons why smooth bores run out of accuracy well before they run out of range. My 10 bore musket will do well at 100 metres with 124 grains but develops a mind of it's own before 200 metres. The addition of a string/ribbon tail to the ball helps the ball transit the transonic zone (as does the Nessler ball) at the cost of extra drag. It is drag stabilised after all. But it does keep up the comparative accuracy to 200 metres and even 300 metres in ideal conditions.

 

[Vaino]

I "read" somewhere of a conversation that Daniel Boone had w/ his buddies on whether super or sub sonic velocities were more accurate....and they concluded by taking a vote and all said "yes"......Fred

 

[Tom Compton]

Ive used sub sonic ammo in target .22s w good results at 25 and 50 yards and expect The same would be true w a round ball. But I don't shoot subsonic loads in my MLers. I just shoot loads that stay supersonic past the target if I see acceptable accuracy from that load. If the RB transitions from super to Sub sonic at say 40 yards the effect at 50 yards may be negligible but by at 100 yards likely will be substantial IMO.
TC

 

[Loyalist Dave]

I was taught that one school of thought was the powder load was adjusted when a new rifle was tried, until a person standing off to the side heard it "crack" as it went down range. We know today the ball was breaking the sound barrier, but they stopped as soon as that point was reached. So if it was just over super sonic, it would probably drop subsonic very shortly after exiting the muzzle..., no? If that was the common practice, then would not most rifles fire at supersonic, and the projectiles drop below that in a very short distance?

LD

 

[George]

If that was the common practice, then would not most rifles fire at supersonic, and the projectiles drop below that in a very short distance?

Unless they were dimpled or had been roughed up between two rasps, then they would stay supersonic all the way to the target, regardless of the distance...within reason, of course. This is one of the generally unknown benefits of rasping. :wink:

Spence

 

[M. De Land]

It's the transonic zone from about 1300 fps down through roughly 950 fps with bullets that causes so much disruption of the projectile path as the pressure waves move down and finally off.
With a ball being a sphere this probably manifests differently than on a bullet.
One can avoid it by shooting subsonically or by keeping the projectile over the speed of sound as long as possible so that the instability and thus wind drift effect, has less geometric influence by occurring farther down range.
With bullets the transonic effect is from about 1300fps down to about 950 fps. The sound barrier is about 1140 fps at sea level if memory serves correctly but the pressure wave movement, once it has passed through the sound barrier, influences it through a much longer range of velocity reduction.
That is the reason for sub-sonic .22 RF match ammo.

 

[Tom Compton]

I was taught that one school of thought was the powder load was adjusted when a new rifle was tried, until a person standing off to the side heard it "crack" as it went down range. We know today the ball was breaking the sound barrier, but they stopped as soon as that point was reached. So if it was just over super sonic, it would probably drop subsonic very shortly after exiting the muzzle..., no? If that was the common practice, then would not most rifles fire at supersonic, and the projectiles drop below that in a very short distance? "

Yep, if they stopped Right at SS speed. Then going subsonic right away may be 40 yards Down range as in the above scenario

Then if the load that created the just barely SS velocity were not as accurate as desired I'd suspect further tinkering was in order and if 100 yd accuracy was desired it would be quite a bit faster than the barely SS load

TC

 

[M. De Land]

This months Muzzle Blast magazine has and article about this very subject from the bevel brothers who have a better grasp and explanation of transonic ball flight than I do.

 

[BrownBear]

Nothing to base this upon, but I've always wondered if the "sweet spot" in loads we hear about has something to do with getting up past any sound effects.

Only reason I ask, I shoot a lot of subsonic loads in rifles ranging from 50 cal on up, and have taking my small calibers down subsonic, too. For me it's mostly an attempt to limit loss of eating meat, but I see some things in the accuracy department too.

Once my loads get real slow, they get real accurate. As I start nudging the velocity up, they go through a range of velocities where accuracy falls off. Then I go a little higher and suddenly find a "sweet spot" where accuracy jumps sharply- often as good as my subsonics. I'm wondering if it might have to do with the sound barrier issues because as loads are increased above the sweet spot, accuracy often stays in the same realm.

Imponderable, but I don't know how else to look at sweet spots along with the high degree of accuracy with subsonic loads.