Velocity Question

[HuntPA]

Start super and back down slowly in 0.3 or 0.5 grain increments. Bullets don't go much slower than 800 fps depending on barrel length before they stop in your barrel. Eventually the bullet will stop in the barrel. CHECK between EVERY round that the barrel is clear. Eye opening to me how much force it takes to move a bullet through rifling.

I have had luck with A1680 for a sub load in a 22 inch barrel.

 

[dellet]

Start super and back down slowly in 0.3 or 0.5 grain increments. Bullets don't go much slower than 800 fps depending on barrel length before they stop in your barrel. Eventually the bullet will stop in the barrel. CHECK between EVERY round that the barrel is clear. Eye opening to me how much force it takes to move a bullet through rifling.

I have had luck with A1680 for a sub load in a 22 inch barrel.

This really is important, with the gain on popularity of subs. There really still isn’t t reliable load data for the many combinations of cartridges, bullets and barrel lengths out there.

I was given a handful of 250 grain ATip when they first came out to try as subs in 300 Blackout. An interesting combination, with an interesting set of problems. Because of the length and weight of the bullet the window of suitable velocity and over pressure was pretty small. I was confident in the load I chose as being safe, and probably higher than needed in a 16” barrel, but chose to try it first in a 8” barrel. Less chance of a stick bullet.

First round measured 250 fps according to Lab Radar. Checked all the settings, second round 300 fps. Set up a second chronograph that confirmed the low velocity. Bumped the charge weight, no real change in velocity.

I was using data that had got 1400 fps safely for a 265 grain cast bullet. Pretty sure it was the bullet. After careful measuring I was stumped. Started reading reviews looking for excessively low velocity problems.

What I eventually stumbled on was people talking about the nice little gift that Hornady included with the individually separated bullets, everyone needs a Hornady logo rag. Turns out the bullets weren’t cleaned after manufacturing and still had on oil coating. The rag was to wipe off the oil. Velocity problem solved. A good example of friction, pressure, velocity relationship. It’s just really magnified with subs

 

[Bowhunter41]

Charlie b

Thanks for the responses I was also thinking of raising the muzzle up to ensure most if not all powder was near the primer.

More experiments to come. I found on sniperhidw forum guys using faster burning powder. When one looks at the hodgdon manual the one page has burn rates of powder froM fastest to slowest while a lot of people say Trailboss that burns relatively slower than say titegroup or tite wad.

 

[charlie b]

Just to add a caution. HuntPA mentioned bullets stopping in the barrel. Squib loads are common when trying to get the slowest bullet possible. When testing make sure you see a bullet hole in the target or a dust cloud of bullet impact on each shot. If not, pull the bolt and look through the bore to make sure there is not a bullet still in there. A bore obstruction may not cause an explosive event, but, it will bulge the barrel. I've had to 'tap out' more than a few bullets during testing.

Do not count on recoil to tell you the round fired properly. There just isn't much.

If you want more information than you can stand go to the CastBoolits forum and look up 'mouse fart' loads.

 

[Bowhunter41]

Charlie b. Totally agree with your statement. Better to be safe then sorry

 

[Bowhunter41]

Thank you all for your input

 

[Bowhunter41]

Ok so I was able to get some rounds out today.
1. I used the Hodgdon manual for H4895 and 175 sub-x. Every round was not subsonic when shooting. I have attached the chrono results.

2. I shot 5 rounds with Titegroup at 8.5 grains with 175 sub-x and chrono wasn’t working right but definitely not quite like I was hoping.

3. I then tried 8 grains of Clays with the 175 Sub-x and every round was nice and quiet with a nice group. Chrono data is also attached and you can see I was at roughly 1100fps.

Titegroup shots are also attached. This is the target with the extra dots for covering holes.

Clays group is next. I had one I pulled. Not a bad group. Again only 50 yards and will try farther later next week. Also going to try with 190g sub-x with 8 grains of Clays. No longer going to try the Titegroup or H4895

 

[Wild Bill IV]

I loaded it up in GRT just cause I was curious

Could not get to 13gn (pressures too low for GRT prediction model). 185gn bullet chosen.
24in bbl, 20gn H4895, 1560fps, 11350psi
16in bbl, 20gn H4895, 1356fps, 11350psi

FWIW, a bullet is accelerating at the muzzle. The pressure is not reduced to 'zero' force on the bullet unless you are using a very long barrel. Yes, people have tried that in order to get a no noise load without a suppressor.

I've shot a LOT of cast bullets from a .308. The mouse fart loads that work well are typically pistol powders. My favorite was 8gn of Blue Dot with 165gn bullets. I used this site to choose loads (their accuracy data was pretty consistent with my results as well):

Lever Gun Performance Studies

Reloading Data for cast bullets, result of lever gun accuracy studies on cartridges: 357 Magnum, 41 Rem Mag, 44 S&W, 44 Russian, 44 Magnum, 444 Marlin, 45-70 Goverment, Pistol Powders, Large Capacity Rifle Cases

www.gmdr.com

The .30-30 data was pretty close to what I got in my .308.

Another consideration is that rifle powders are position sensitive at low load densities, ie, if you tip the barrel up before shooting the primer ignites the load in a more consistent manner. If tipped down there is a lot of free space that 'uses up' the primer energy and the powder may not ignite causing a squib load (yes, it has happened to me, more than once ). This is the reason most mouse fart loads are pistol powder. They ignite quickly and all at once no matter what you do with it.

Mouse farts!!! FUNNY!!!!!
Reduced loads, sometimes using pistol powders, are called SQUIBB LOADS!!!
The old Lyman reloading manuals had the regular rifle loads, the lead gas checked loads, and the Squibb loads!!!!

 

[charlie b]

I usually refer to squib loads as the ones where the bullet fails to leave the barrel. We had a long discussion in the cast boolit forum on the proper names for reduced load of various levels.

There was also a sticky in one of the cast boolit forums on mouse fart loads for the .30-06. FWIW, some folks call them 'cat sneeze' loads, gallery loads or various other such names.

Mouse Fart" Loads Recipes in 30-06

Buddy of mine wants to play with low noise/velocity loads in a pre-64 M-70. The only boolits available to us right now are 311440s and (when it arrives) the Lee 311-93-RN. Anybody got proven suggestions for such things?

castboolits.gunloads.com

 

[Wild Bill IV]

I usually refer to squib loads as the ones where the bullet fails to leave the barrel. We had a long discussion in the cast boolit forum on the proper names for reduced load of various levels.

There was also a sticky in one of the cast boolit forums on mouse fart loads for the .30-06. FWIW, some folks call them 'cat sneeze' loads, gallery loads or various other such names.

Mouse Fart" Loads Recipes in 30-06

Buddy of mine wants to play with low noise/velocity loads in a pre-64 M-70. The only boolits available to us right now are 311440s and (when it arrives) the Lee 311-93-RN. Anybody got proven suggestions for such things?

castboolits.gunloads.com

Since I have the old Lyman Manual (the cast bullet mold makers), the velocity for the OPs question is 1057ft/s for the 24" barrel!!! That puts the velocity in the the 0-2000 range which is a reduction of 5ft/s per inch of barrel reduction!! 24-16=8in!!! The velocity of that load will be close to 1017ft/s for the 16" barrel!!!!

The bullet is under going an acceleration or increasing velocity rate!!! Shorten the distance traveled, reduces the final speed!!! Addition barrel length increases the muzzle velocity, Reducing the barrel length, reduces the muzzle velocity!!!

See the old, yellow picture of the chart from the old Lyman manual!!!!

 

[dellet]

Since I have the old Lyman Manual (the cast bullet mold makers), the velocity for the OPs question is 1057ft/s for the 24" barrel!!! That puts the velocity in the the 0-2000 range which is a reduction of 5ft/s per inch of barrel reduction!! 24-16=8in!!! The velocity of that load will be close to 1017ft/s for the 16" barrel!!!!

The bullet is under going an acceleration or increasing velocity rate!!! Shorten the distance traveled, reduces the final speed!!! Addition barrel length increases the muzzle velocity, Reducing the barrel length, reduces the muzzle velocity!!!

See the old, yellow picture of the chart from the old Lyman manual!!!

Only if your lucky.
Basically you interpreted the chart to fit your narrative.

The bullet is gaining velocity with barrel length, but the rate of gain is dropping. So a bullet with a muzzle velocity of 2000 fps at 20” will gain 5fps for the next 6”. But a 16” barrel will gain 15 fps from 16-20”(made up number it will actually be higher most often).

If you want to extrapolate data from that chart, for every 500 fps change in velocity, the rate of velocity gain per inch of barrel doubles, or halves depending on if you read the chart top to bottom, bottom to top. So a bullet with a muzzle velocity of 1500 fps in a 20” barrel would only gain 2.5 fps per inch, and 1000 fps would gain 1.5 fps per inch. This actually is pretty close to my live fire experience. They start losing velocity 22-26” when the load was developed for an 8” barrel.

So the shorter the barrel, the more velocity loss per inch and it’s not linear, more exponential. The drop from 24”-20” will be 20 fps. The drop from 20”-16” will be closer to 40-60 fps, possibly a total of 60-80 fps. More or less double what you predicted.

The problem is paper predictions and actual results with subs in a rule of thumb chart like above, is basically nonsense. The results of an 80 grain 22 caliber bullet vs a 350 grain 38 caliber bullet will be different. As will be a lubed lead vs a copper solid.

It’s very frustrating to talk subs with people who have not loaded them over many cartridges and barrel length. It’s just not like supers.

 

[dellet]

Ok so I was able to get some rounds out today.
1. I used the Hodgdon manual for H4895 and 175 sub-x. Every round was not subsonic when shooting. I have attached the chrono results.

2. I shot 5 rounds with Titegroup at 8.5 grains with 175 sub-x and chrono wasn’t working right but definitely not quite like I was hoping.

3. I then tried 8 grains of Clays with the 175 Sub-x and every round was nice and quiet with a nice group. Chrono data is also attached and you can see I was at roughly 1100fps.

Titegroup shots are also attached. This is the target with the extra dots for covering holes.

Clays group is next. I had one I pulled. Not a bad group. Again only 50 yards and will try farther later next week. Also going to try with 190g sub-x with 8 grains of Clays. No longer going to try the Titegroup or H4895

So if I understand this correctly, based on your original question, you used load data for a 24” barrel, loaded it into a 16” barrel and the velocity was 175- 200 fps faster than the 24” barrel prediction?

Or were you using a 24” barrel?

If that’s correct, welcome to sub life. Even if it’s not, still welcome.

 

[Wild Bill IV]

Only if your lucky.
Basically you interpreted the chart to fit your narrative.

The bullet is gaining velocity with barrel length, but the rate of gain is dropping. So a bullet with a muzzle velocity of 2000 fps at 20” will gain 5fps for the next 6”. But a 16” barrel will gain 15 fps from 16-20”(made up number it will actually be higher most often).

If you want to extrapolate data from that chart, for every 500 fps change in velocity, the rate of velocity gain per inch of barrel doubles, or halves depending on if you read the chart top to bottom, bottom to top. So a bullet with a muzzle velocity of 1500 fps in a 20” barrel would only gain 2.5 fps per inch, and 1000 fps would gain 1.5 fps per inch. This actually is pretty close to my live fire experience. They start losing velocity 22-26” when the load was developed for an 8” barrel.

So the shorter the barrel, the more velocity loss per inch and it’s not linear, more exponential. The drop from 24”-20” will be 20 fps. The drop from 20”-16” will be closer to 40-60 fps, possibly a total of 60-80 fps. More or less double what you predicted.

The problem is paper predictions and actual results with subs in a rule of thumb chart like above, is basically nonsense. The results of an 80 grain 22 caliber bullet vs a 350 grain 38 caliber bullet will be different. As will be a lubed lead vs a copper solid.

It’s very frustrating to talk subs with people who have not loaded them over many cartridges and barrel length. It’s just not like supers.

OK dellet, GAME ON!!! I ACCEPT YOUR CHALLENGE!!!!
I was using the KISS PRINCIPLE for a really rough estimate!!!
I'm looking at the 308 (26" test barrel) loads for the 180 grain cast bullet with gas check from the Lyman manual where they are using pistol and shotgun powders!!! Velocities run, with the minimum powder charges, from 1200 to 1457!!! I trust the Lyman rough estimate barrel length chart since they are the old timers dealing with squib and low velocity lead cast bullets w/wo gas checks!!!

So, the drop in muzzle velocity from 24" to 20" is 1057 - (4" * 5) = 1037f/s!!!

There is a reason for Lyman stopping at 20"!!!
I think is for the lead and squib loads using fast burn powder burning up at that average or mean distance!!

Now lets move on and find how much more drop in velocity with the last 4"!!!

Let's use Engineering Physics!!!
I'm going to make an assumption that the base of the bullet is at the shoulder/neck junction which is 2.015" from the base!!!
So, the base of the bullet will roughly be 2" (simplified for calculations) on the breach end of the barrel!!
The true length will not be that critical since we are rough estimating!!!
For the 20" barrel, the bullet will travel 18"!!!
For the 16" barrel the bullet will travel 14"!!!
The initial velocity (Vi) will be 0f/s.
The final velocity (Vf) for the 20" barrel is 1037f/s rough estimated.
The acceleration will include the deceleration due to friction since the MV=1037f/s.
Time to find the acceleration (a)!!!!!!!!!
For the 20" barrel x=18" at this time for finding acceleration!!!!
a = (Vf^2 - Vi^2) / (2x) = Vf^2/2x = 29,871f/s^2
Now that we know the acceleration, the new Vf will be for the 16" Muzzle velocity!!!
x will now be equal to 14"!!!!!!
Rearranging the formula will simplify the equalities!!

Vf = (2 * a * x)^(1/2) = 915f/s Muzzle velocity for the 16" barrel

SO, THE THEORETICAL DROP IN VELOCITY (20" to 16") IS 1037 - 915 = 122f/s!!!
Or, 122/4 = 30.5f/s for each inch of barrel change below 20"!!
The total drop in velocity is 142f/s for the full 8" change in barrel lengths!!!!!

Now, I know you are going to tear this apart, dellet!!!!
I'm trying to show the other members the Physics aspect of the problem that the OP gave us!!
Sometimes, Real life result can be much different than the theoretically calculated prediction!!!

I have never messed with squib loads or subsonic rounds other the subsonic 22 rims!!!!

BILL!!!!!!!!!!

 

[Bowhunter41]

Dellet

I was using a 16” barrel. My original question was….load data was based on a 24” barrel how much difference would I see out of a 16” barrel? Plus just trying to find more loads. Recently loaded 190gr, Sub x with clays. Will test that out in the near future

 

[dellet]

OK dellet, GAME ON!!! I ACCEPT YOUR CHALLENGE!!!!
I was using the KISS PRINCIPLE for a really rough estimate!!!
I'm looking at the 308 (26" test barrel) loads for the 180 grain cast bullet with gas check from the Lyman manual where they are using pistol and shotgun powders!!! Velocities run, with the minimum powder charges, from 1200 to 1457!!! I trust the Lyman rough estimate barrel length chart since they are the old timers dealing with squib and low velocity lead cast bullets w/so gas checks!!!

So, the drop in muzzle velocity from 24" to 20" is 1057 - (4" * 5) = 1037f/s!!!

There is a reason for Lyman stopping at 20"!!!
I think is for the lead and squib loads using fast burn powder burning up at that average or mean distance!!

Now lets move on and find how much more drop in velocity with the last 4"!!!

Let's use Engineering Physics!!!
I'm going to make an assumption that the base of the bullet is at the shoulder/neck junction which is 2.015" rhetorically!!!
So, the base of the bullet will roughly be 2" (simplified for calculations) on the breach end of the barrel!!
The true length will not be that critical since we are rough estimating!!!
For the 20" barrel, the bullet will travel 18"!!!
For the 16" barrel the bullet will travel 14"!!!
The initial velocity (Vi) will be 0f/s.
The final velocity (Vf) for the 20" barrel is 1037f/s rough estimated.
The acceleration will include the deceleration due to friction since the MV=1037f/s.
Time to find the acceleration (a)!!!!!!!!!
For the 20" barrel x=18" at this time for finding acceleration!!!!
a = (Vf^2 - Vi^2) / (2x) = Vf^2/2x = 29,871f/s^2
Now that we know the acceleration, the new Vf will be for the 16" Muzzle velocity!!!
x will now be equal to 14"!!!!!!
Rearranging the formula will simplify the equalities!!

Vf = (2 * a * x)^(1/2) = 915f/s Muzzle velocity for the 16" barrel

SO, THE THEORETICAL DROP IN VELOCITY IS 1037 - 915 = 122f/s!!!
Or, 122/4 = 30.5f/s for each inch of barrel change below 20"!!
The total drop in velocity is 142f/s for the full 8" change in barrel lengths!!!!!

Know I know you are going to tear this apart, dellet!!!!
I'm trying to show the other members the Physics aspect!!!
Sometimes, Real life result can be much different than the theoretically calculated prediction!!!

I have never messed with squib loads or subsonic rounds other the subsonic 22 rims!!!!

BILL!!!!!??

Too many letters identifying as numbers. I don’t do that woke crap.

Besides now you’ve changed the study and the parameters to prove I was right about what I said in the first place. To top it off you want to claim you were right all along.

How am I supposed to win when the game is rigged?

Wait. I can simply change powders, change the pressure curve, And therefore. manipulate the results. And you’ll need to lay out a whole bunch of trans letters and numbers again.

Challenge accepted.

Or we can just read @Bowhunter41 last post answering my question about his chrono data from the weekend.

His chosen load at 24” expected velocity 1050 netted 1250 in a 16”, and where have I been saying to start expecting a drop of in muzzle velocity, around 22 -24”. If he has a 24” rifle it would be nice to see how that load compares to the book.

Spoiler alert. I have 12” barrel that is faster than half my 16” barrels and very close to a couple 18”. So if I need to game the system to get the results I want. I certainly can.

Back to my original post, you really won’t know until you shoot the load.

I really hate to pile on but I think you said his load would loose about 120 fps in a 16”. That means you were off in your prediction by over 300 fps. Or about 35%. Subs are in a different ballistic world

 

[Wild Bill IV]

Too many letters identifying as numbers. I don’t do that woke crap.

Besides now you’ve changed the study and the parameters to prove I was right about what I said in the first place. To top it off you want to claim you were right all along.

How am I supposed to win when the game is rigged?

Wait. I can simply change powders, change the pressure curve, And therefore. manipulate the results. And you’ll need to lay out a whole bunch of trans letters and numbers again.

Challenge accepted.

Or we can just read @Bowhunter41 last post answering my question about his chrono data from the weekend.

His chosen load at 24” expected velocity 1050 netted 1250 in a 16”, and where have I been saying to start expecting a drop of in muzzle velocity, around 22 -24”. If he has a 24” rifle it would be nice to see how that load compares to the book.

Spoiler alert. I have 12” barrel that is faster than half my 16” barrels and very close to a couple 18”. So if I need to game the system to get the results I want. I certainly can.

Back to my original post, you really won’t know until you shoot the load.

That's why I made the comment of Real World vs Theoretic!!!!
There are too many unknown variable working backwards on the reloading data!!!

If you subsonic shooters want to SAFELY use the old Lyman data, for the 308, the cast/w GC bullets weights are:123, 150, 155, 173, 176, 180, 183, and 193 grains.
Powders: Hi-Skor 700X, PB, SR 7625, SR 4756, Red Dot, Unique, Green Dot, and Herco!!!!!!

The test barrel is 26" (1:12) unfortunately!!! Winchester 8-1/2 primer for all cast bullets using the powders listed above!!! The max extreme velocities of all cast bullets spread is 51f/s!!! Accuracy Loads for the cast spread is 5-18f/s!!!

After noting the spread, maybe there is something special about the Win 8-1/2 primers for the shotgun powder use in metallic large primer cases??????????

 

[Wild Bill IV]

Too many letters identifying as numbers. I don’t do that woke crap.

Besides now you’ve changed the study and the parameters to prove I was right about what I said in the first place. To top it off you want to claim you were right all along.

How am I supposed to win when the game is rigged?

Wait. I can simply change powders, change the pressure curve, And therefore. manipulate the results. And you’ll need to lay out a whole bunch of trans letters and numbers again.

Challenge accepted.

Or we can just read @Bowhunter41 last post answering my question about his chrono data from the weekend.

His chosen load at 24” expected velocity 1050 netted 1250 in a 16”, and where have I been saying to start expecting a drop of in muzzle velocity, around 22 -24”. If he has a 24” rifle it would be nice to see how that load compares to the book.

Spoiler alert. I have 12” barrel that is faster than half my 16” barrels and very close to a couple 18”. So if I need to game the system to get the results I want. I certainly can.

Back to my original post, you really won’t know until you shoot the load.

I really hate to pile on but I think you said his load would loose about 120 fps in a 16”. That means you were off in your prediction by over 300 fps. Or about 35%. Subs are in a different ballistic world

The light bulb just come on!!! I had to start thinking about how the shotgun works (Internally) and looking at the cast bullet reloading data for other cartridges (including the pistol data)!!!

These really fast burning powders have a much steeper upward pressure curve but low peak pressure for SUBSONIC muzzle velocity!! The bullet engraves during the upward spike of pressure and is accelerated for a short length (a few inches depending on the burn rate and charge weight of powder) at the point of peak pressure (complete burn of the powder)!!! After that, the pressure decreases as the bullet moves forward!!! The bullets momentum also keeps the bullet moving down the barrel!!! But, friction is causing a deceleration!!! As the barrel length increase beyond the peak pressure point in the barrel, the muzzle velocity decrease (indirectly or directly?)!!! If the charge is dropped too low, the peak pressure will be too low, and the frictional force could stop the bullet if the barrel is too long for that lighter charge!!! That is why you have the barrels at 16" or less and SAFELY work on decreasing the powder charge to achieve subsonic velocities!!!

In summary, when we as shooter are going for muzzle velocities that are greater than 2500f/s, the pressure, and the density of the hot gases is very high and friction is a much lower opposing force!!! However, in the Subsonic game, the pressure and the amount of hot gas is much lower and friction coming into play when looking at internal ballistics variables!!!

In post #33, I made the assumption that friction was included in the acceleration with MV at 1037f/s with 95% - 100% Burn at the muzzle!!!! MY PERSONAL MISTAKE IN NOT UNDERSTANDING THE SUBSONIC BALLISTICS VARIABLES!!!! Friction is included in the acceleration up to the 100% Burn point in the barrel!!! Past the 100% Burn point, fiction is a major opposing force variable in the the declining acceleration (deceleration)!!!

dellet, Is the light bulb burning bright or is it dim???????

 

[Wild Bill IV]

Bowhunter41 and dellet:
This fairly new concept of the Subsonic sport is very interesting!!! Your posts are raising more questions. I am now starting to understanding why my brother (recently deceased) had THOMPSON Contenders and Encores firearms! He really liked making and shooting some really wild Wildcats by simply swapping out Thompson custom made barrels with fixed sights or scopes mounted on the interchangeable barrels!!! One was the 7mmTCU. A 223 parent cartridge with a slightly shortened steeper shoulder, Ackley Improved designed for 7mm bullets!! I shot that Contender, and few JDJ series wildcats, a few times and was shocked by the low recoil!!! He also liked custom building Ruger revolvers! One of his pride and joys was a six shooter in 300GNR!!! This Wildcats parent cartridge was the rimmed 30-30 Winchester!!! It required setting the new, steeper shoulder way down further on the case body, trimming the really excessively long neck, and reaming out the really thick tapered neck (part of the shoulder and body are now the new neck)!!! A good hefty charge blows out the body for a straight walled bottleneck revolver case!!!

Now mind you, his Wildcats were supersonic!!! But, these wildcats can be tamed down to shoot subsonic!!! Another passion of his gun collection is Ruger Revolver themselves!!! He took my Custom 50AE (5 shot revolver, made on a Ruger Blackhawk frame) and reduced the muzzle velocity a couple hundred f/s!!! That round was design for the big and heavy Desert Eagle (semiautomatic pistol)! When shooting the factory ammo in the 5 shot revolver, you had to set it down after 7-10 shots!! It wasn't the heavy lift of the barrel, nor the heavy recoil, but added heavy twisting (325-350grain bullets leaving the barrel at around and over 1400f/s)) of the gun that hurt the wrists (HEAVY back, lifting, and twisting recoil)!! It was a real handful to keep some control of that revolver when shooting the factory ammo!!!