Load formulas - starting in the middle?

[mpmo]

Hey y'all. New to relaoding. Got my first batch of rounds loaded and tested. Had a safety question. The Lyman manual states to always start at the minimum load value and work your way up. However, some (if not all, I haven't looked at all, just the powder combos I'm interested in) will produce a power factor that is below the recommended minimum for at least one of my pistols. (Recommends a minimum PF of 125.) What is the recommendation? Still start at the beginning and work up? Or start at the amount that meets the min PF for my handgun?

Thanks!

 

[ghbucky]

Start at the beginning and work up. I follow that rule to the letter.

Especially if you are new, start where the manual says and follow all the steps.

 

[Hammerhead]

How do you know what the minimum is for your gun if you don't start at the bottom
?

 

[ammo.crafter]

reloading is fun

Bucky is right on point. ALWAYS abide by the book. That is why it is there.

Not following rules can end up ruining a gun, yourself, or a fellow shooter.

Reloading is a slow process of component combinations, specific firearm, weights, measures, etc. Your starting point is whatever the manual tells you. Have patience and take your time.

Keep detailed performance records and endeavor to have your shooting sessions exactly the same; windage, temperature, distance, etc.

Stay within the safety boundaries and enjoy the process of shooting for perfection!

 

[Old_School]

Hey y'all. New to relaoding. Got my first batch of rounds loaded and tested. Had a safety question. The Lyman manual states to always start at the minimum load value and work your way up. However, some (if not all, I haven't looked at all, just the powder combos I'm interested in) will produce a power factor that is below the recommended minimum for at least one of my pistols. (Recommends a minimum PF of 125.) What is the recommendation? Still start at the beginning and work up? Or start at the amount that meets the min PF for my handgun?



Thanks!

Begin at starting loads if new to reloading. As you gain experience, you'll begin to understand what is safe and what is not.

Sent from my moto z4 using Tapatalk

 

[mpmo]

How do you know what the minimum is for your gun if you don't start at the bottom
?

Minimum PF listed in the instructions on a CZ TSO is 125. Using the recipes out of Lymans for RN 115 FMJ with Acc #7 and Power Pistol, the expected fps would put it under that power factor.

My fear is that I could get squib loads if there is not enough PF.

 

[ghbucky]

Minimum PF listed in the instructions on a CZ TSO is 125. Using the recipes out of Lymans for RN 115 FMJ with Acc #7 and Power Pistol, the expected fps would put it under that power factor.

My fear is that I could get squib loads if there is not enough PF.

The starting load may not be able to cycle the gun, but it won't squib.

 

[44 AMP]

Welcome to tfl!

will produce a power factor that is below the recommended minimum for at least one of my pistols.

Recommended, by whom, for what??

The gun maker?? Lyman?? (never heard of them doing so..)

Or the rules committee for playing a certain game? (have heard of that)

Every gun is slightly different. Every ammo combination is slightly different. Everything made by man has tolerances. These factors react with each other and "line up" or "stack" creating the result we get. Most of the time, the result is very similar, creating a bell curve of results. However sometimes the results are drastically different from what is expected, either on the high or low end of the curve.

NO ONE knows, or can know just where YOUR exact combination of gun and components is going to be on that curve, until it is tested.

It is possible your gun and the ammo you made could produce unacceptably high pressures WITH the starting load. Its not common but it IS possible.

Lyman and the others choose a starting load that they expect to be SAFE, in any gun in safe operating condition. But, they cannot KNOW what is safe in your gun.

So, you start at the starting load (or below), load some rounds and fire them, to test, and prove that load is safe in your gun. Once you've done that, you work up in steps, until you get to your desired level, or reach the listed max loads, testing each step along the way, looking for anything indicating you're approaching or at your gun's max safe level.

Your gun and ammo might start showing pressure signs (like sticky extraction, etc) BEFORE reaching the listed max in the data. OR it might not. Their test gun is not your gun.

Extremes are always possible, so you start low until you KNOW your gun is ok at that level. Doesn't matter what somebody else says you need, what matter is what your gun does.

I've seen those differences first hand. Gun A with load XYZ, every thing fine. Gun B, same load, cases had to be driven out of the chamber with a rod.

It's rare, but it can happen, so until you know your gun isn't "gun B" you start at the bottom end of the data.

 

[ghbucky]

Let me put your squib concerns to rest.

I looked at your other post for your bullet/powder combos, and my Lyman manual states that for a starting 9mm load with your bullet over power pistol, the starting load out of a 4" barrel was measured with 1102fps muzzle velocity.

It won't squib.

In order to determine what PF you are at, you will have to chrono your shots. Feeding the published data, which was gathered using a universal receiver, into the formula won't tell you your PF.

 

[DaleA]

I agree with the others that you probably (almost certainly) will not have a squib but know that a squib is not the end of the world.

When it has happened to me it has been VERY obvious. The sound was off and all the gases came out of the breech (because they couldn't get out the muzzle) and like I said this was very evident.

Note do not use a wooden dowel to drive the bullet out of the barrel. The wood can splinter and jam and make things worse. Use a soft metal (like brass) rod close to the inside diameter of the barrel to do the job.

 

[rg1]

When working up new loads I only make 1 or 2 rounds of start charges all the way to midrange. Then at midrange I load more rounds to test. All the start charges I've chronographed even up to midrange have been weak and very slow velocity for caliber. Good idea to start at recommended start loads but don't waste many rounds or components as you'll find a good load at midrange or higher.

 

[Aguila Blanca]

Minimum PF listed in the instructions on a CZ TSO is 125. Using the recipes out of Lymans for RN 115 FMJ with Acc #7 and Power Pistol, the expected fps would put it under that power factor.

My fear is that I could get squib loads if there is not enough PF.

As 44_AMP wrote, I have never seen a loading manual that included "recommended" (or any other) power factors. Power factor is a creature of the shooting sport games. They aren't "recommended," they are "required" -- in order to keep the playing field somewhat level. 125 is the minimum power factor allowed to play in IDPA, IPSC, and USPSA. (165 is the minimum for the "major" classes or divisions). A load that "only" makes a power factor of, say, 115 or 120 is hardly a squib.

There was an article in Shooting Times while ago about loads to make a 125 power factor in .45 ACP. The author was discussing whether a heavier bullet and slower velocity or a lighter bullet and higher velocity produces more recoil when both are loaded to the same power factor.

I don't want to drag this discussion off into arguing that point. I mention it because he listed a load that made a power factor of 127 -- just about enough cushion for someone who shoots in a division requiring a power factor of 125. It was a .45 ACP load, using a 185-grain bullet. The velocity was 687 fps.

That's nowhere close to being a squib. An empty case, with just a primer, will push a bullet halfway down the barrel of most handguns. It doesn't require a lot of powder to push it the rest of the way.

 

[Unclenick]

Mpmo,

The exact answer depends on your data source. Lyman is referring to their data. The same applies to Hodgdon data. But some data, like some Hornady data or Sierra data can start lower than than you need to go for safety. That data is just showing it is possible to get pretty low with it. The general rule of thumb is if you multiply the maximum load by 0.9, you are as low as you need to go. If the published data is higher than that at the start, use the published data because there are a few magnum powders that cannot be safely loaded down by very much (296/H110, for example) or it will squib out.

Western Powders likes to use multiplying the maximum by 0.9 (10% below maximum) for rifle cartridges and 0.85 (15% below maximum) for pistol cartridges for an extra safety margin, and I typically do that. the reason for the extra wiggle room in handgun rounds is the charges are often small enough to suffer a bigger percent variation from powder measure variation in delivered charge. Also, handgun cartridges are more significantly affected by primer and brass and bullet seating depth variation that the bigger volume rifle cases are.

As already mentioned, you cannot tell what power factor you will actually get from a load recipe. Some guns are tighter than others. It is not uncommon for the actual velocity you get to be lower than a published load velocity, but occasionally it can also be higher. For load data that has pressure readings associated with it and for commercial ammunition, the published velocities are usually for a SAAMI pressure and velocity barrel which has a minimum chamber (to tend to create maximum pressure) and a particular barrel length that you have to look up in the SAAMI standard. If your barrel is a different length, obviously you won't get the same velocity because the gasses will be accelerating your bullet for more or less time, depending on whether your barrel is longer or shorter than the SAAMI test barrel. However, the SAAMI P&V barrels use nominal bore and groove diameters, not minimum ones. As a result, even if your chamber isn't quite as tight as they have, if your bore dimensions are tighter than theirs are, you can still get higher pressure and velocity than they did. This is the main reason you start with at the bottom or the 0.85×max load. Your gun may get higher pressures with each listed load than the test barrel did, and you can tell by using a chronograph to see if you are getting more velocity at the same barrel length (if you have that).

An example" we had a member a couple of years ago loading for a handy rifle who had the action popping open on firing and who was getting 200 fps more velocity than the published load when he was still more than a grain of powder below the published data maximum. That isn't common, but you don't know if your gun is one of the tight ones that will produce those higher pressures and velocities until you try it.

Also, it doesn't take much shooting to find out if your gun is happy with the full published load range. You work up in steps that are 2% of the published maximum load, and you really only need one shot at each level to look for pressure signs. Only if you get a questionable pressure sign do you need to think about running a few more identical rounds to confirm it.

 

[mpmo]

Awesome y'all. Thanks for the guidance!

I will double check tonight, but I am pretty positive my CZ TSO lists a min/max powerfactor in the manual.

 

[Unclenick]

They are just trying to ensure a minimum amount of momentum, which is what the power factor is, though a physicist would find the units odd. It's not a very precise specification as the same power factor can be produced by different amounts of different burn rate powders. The powder gases contribute to total recoil via the rocket effect of muzzle blast, and a specification not considering that is only approximate. And given the different velocities that are produced by different weapons firing the same load, it can really only be a "thereabouts" specification anyway.

 

[Aguila Blanca]

And given the different velocities that are produced by different weapons firing the same load, it can really only be a "thereabouts" specification anyway.

^^^ Sad, but true.

That light load from the Shooting Times article made a power factor of 127 ... fired through the author's 5-inch, full-size 1911. I used to compete with a Para-Ordnance P13.45, which has a Commander-size 4-1/4-inch barrel. Even if that load made 127 through one of my 5-inch pistols, it probably won't through a 4-1.4-inch barrel. My early experiments showed a velocity drop of 8% to 10% going from a 5" 1911 to a 4-1/4" 1911. That would reduce the power factor for the exact same ammunition to 114 to 117.

It's a shortcoming in the rules, but I can't think of any easy way to overcome it, other than having all ammo of a specific caliber fired through a "standard" gun provided by the club hosting the event.

 

[reynolds357]

You should follow the instructions in the reloading manual.
Having said that, for a bolt rifle 99% of the time, I jump in at max. I find it odd that for reloading we must assume that all rifles behave differently. There is some truth to that, but Its odd that the factory loads are now run up at max pressures and we dont see all these rifles that behave differently blowing up. There is some super hot factory ammo out there now. I have not heard of anything getting blown up.

 

[Bart B.]

You should follow the instructions in the reloading manual.
Having said that, for a bolt rifle 99% of the time, I jump in at max. I find it odd that for reloading we must assume that all rifles behave differently. There is some truth to that, but Its odd that the factory loads are now run up at max pressures and we dont see all these rifles that behave differently blowing up. There is some super hot factory ammo out there now. I have not heard of anything getting blown up.

How do consumers verify factory ammo has exactly SAAMI spec XX,XXX psi in any firearm?

All firearm bullet, bore and groove diameters for a given cartridge are not equal. There's tolerances just like those for powder and primer lots.

SAAMI pressure specs are established to not weaken firearms nor cases. They're not 1 psi below barrel nor action shattering into several hundred ragged parts harming humans. Even proof loads several thousand psi over standard pressure must not physically damage firearms.

 

[Unclenick]

Having said that, for a bolt rifle 99% of the time, I jump in at max.

Just understand that this is a statistical gamble. Three times in my life I've run into guns for which a published starting load was about maximum for that gun, and in the case of a Charter Bulldog revolver, its chambers would likely not have been left original size by the amount of 2400 one manual said it should be OK with. Short of potential damage, I've also seen maximum rifle loads pierce primers, pock-marking my bolt face with gas cutting, and leaving the primer pockets in the case too loose to seat another primer in. The example of the Handi Rifle I cited is one another board member experienced (and yes, the owner knew about the Handi Rifle dirty latch hook issue and made sure it wasn't present) and this was working up from load data in a current Speer manual for 243 Winchester.

I doubt you'll ever blow up a modern action jumping in at maximum except possibly a revolver cylinder, as I mentioned. Still, you can put a lot of throat wear on a barrel fast with loads that run peak pressures somewhere between SAAMI maximum and the proof load range.

I find it odd that for reloading we must assume that all rifles behave differently.

We don't. We just don't assume the copy we have behaves like the average does until it proves it. That's because of manufacturing tolerances. For example, military 30 caliber barrels are specified with ±0.0015" diameter for both bore and groove. If you get one of the tight ones with a 0.3065" grooves and a 0.2985" bore, you get higher velocities and pressures from a given load than ones with wider dimensions do, and, in particular, if you rely on loads developed to SAAMI standards, you know they were tested in a wider bore.

The SAAMI standard says rifle bores should be nominal diameter plus up to 0.002" wider values, but not all commercial barrels actually conform to that. Some tighter ones are out there and some are produced intentionally tighter in the custom match barrel market and they will get pressures higher than the SAAMI pressure and velocity test barrels do. Some will have the same diameters but more of the cross-sectional area occupied by the lands of the rifling, reducing that area, and that area is what matters to pressure and velocity.

There is some truth to that, but Its odd that the factory loads are now run up at max pressures and we dont see all these rifles that behave differently blowing up. There is some super hot factory ammo out there now. I have not heard of anything getting blown up.

If you buy a Pressure Trace, you'll see lots of factory ammo running 5 to 10% below SAAMI Max. It all depends what powder they have on hand. They aim to produce a particular claimed velocity, not a particular pressure.

Normally, pressure peaks when a bullet is an inch or so into the barrel. That's why copper fouling tends to be heaviest just in front of the throat. The peak pressure subjects the bullet to the greatest number of g's of acceleration and the force squeezes the bullet toward shorter, which tends to expand the sides outward against the bore, increasing the friction it has with the bore. Once the bullet passes the peak position, at which point it has about half its velocity in a typical load, the question becomes how much additional velocity it will pick up from the pressure behind it as it continues down the bore. The powders that produce the highest muzzle velocities are chosen to have burn characteristics that make more gas after the peak so the bullet keeps accelerating. They produce higher muzzle pressures and recoil as a result, but lots of velocity. It is this and not raising peak pressure that is primarily responsible for the high-velocity in some modern ammunition.

Finally, for a typical rifle load, it only takes six rounds to double-check that the published range of loads is good in your gun. One round at 10% below max. One 8% below max. One 6% below max. One 4% below max. One 2% below max. And one at max. Fired in that order after manipulating the gun to have the powder back over the flash hole (this produces your worst-case highest pressure for the conditions you are shooting in), and you can see if you are going to have to worry about pressure signs or not.

 

[Bart B.]

Unclenick comments....

For example, military 30 caliber barrels are specified with ±0.0015" diameter for both bore and groove. If you get one of the tight ones with a 0.3065" grooves and a 0.2985" bore, you get higher velocities and pressures from a given load than ones with wider dimensions do, and, in particular, if you rely on loads developed to SAAMI standards, you know they were tested in a wider bore.

The SAAMI standard says rifle bores should be nominal diameter plus up to 0.002" wider values, but not all commercial barrels actually conform to that. Some tighter ones are out there and some are produced intentionally tighter in the custom match barrel market and they will get pressures higher than the SAAMI pressure and velocity test barrels do. Some will have the same diameters but more of the cross-sectional area occupied by the lands of the rifling, reducing that area, and that area is what matters to pressure and velocity.

British Commonwealth fullbore rifle competitors are often required to use arsenal 7.62 NATO M80 ball ammo whose bullet diameter is typically .3070" and match grade barrels made for them by Border and Kreiger have .3065" groove diameters. Best accuracy in center fire barrels has always mandated barrel groove diameters be a few ten-thousandths smaller than bullet diameter. Or the reverse for bullets.

Olin Mathison companies Winchester and Western knew this as their 180, 197 and 200 grain 30 caliber match bullets were .3088" to .3089" for use in Winchester 70 match barrels having groove diameters .3084" to .3086." I've slugged several of both pre-'64 broach rifled and post-'64 hammer forged 30 caliber match barrels with those diameters