Trying to duplicate a factory load

[lancem]

I'm trying to duplicate a factory load, they say their MV is 1500 Fps, of course they don't mention barrel length or distance from muzzle the measurement was made. Today I ran a batch of my loads through my chronograph and averaged 1465 fps at about 14' from the muzzle. I'm not seeing excess pressure signs and accuracy is good, am I there?

[elmacgyver0]

I would be happy with it.

[JonB_in_Glencoe]

I'm trying to duplicate a factory load, they say their MV is 1500 Fps, of course they don't mention barrel length or distance from muzzle the measurement was made. Today I ran a batch of my loads through my chronograph and averaged 1465 fps at about 14' from the muzzle. I'm not seeing excess pressure signs and accuracy is good, am I there?

Good enough as far as I'm concerned, but I could care less about factory loads.
IF...the definition of your goal is to "duplicate a factory load," then you should probably shoot some factory loads in your gun with your chrono, then you'll have something to compare.
That's my 2¢

[Winger Ed.]

Sounds like you're there.
Some, maybe most loads fired from laboratory type test barrels turn in slightly different speeds that a regular gun.

If the speed is from the ammo maker- some of them are a little on the 'optimistic' side too.

[Good Cheer]

Well, wouldn't want to encourage unsafe behavior but the American public is the greatest small arms research laboratory the world has or probably will ever know. Keep at it, keep up the correspondence and who knows where it can go.

[stubshaft]

Close enough.

[lancem]

Good enough as far as I'm concerned, but I could care less about factory loads.
IF...the definition of your goal is to "duplicate a factory load," then you should probably shoot some factory loads in your gun with your chrono, then you'll have something to compare.
That's my 2¢
That for sure would tell the tale but I'm cheep and spending $35 for 20 rounds just to see isn't going to happen :)

[JonB_in_Glencoe]

That for sure would tell the tale but I'm cheep and spending $35 for 20 rounds just to see isn't going to happen :)

Oh, I figured you had a reason to "duplicate a factory load" as opposed to just wanting the best load for the gun to achieve a desired speed.

[contender1]

One thing many do not understand,, ammo manufacturers often use a "proprietary" powder in their ammo. Not available to the general public.

Next,, velocity. It's not the only key to shooting. Accuracy is the desired outcome. Velocity is but ONE part of the equation.

[bimus]

I would have to shoot and chronograph that factory ammo for my self a number on the box is just a number .

[deces]

I'm trying to duplicate a factory load, they say their MV is 1500 Fps, of course they don't mention barrel length or distance from muzzle the measurement was made. Today I ran a batch of my loads through my chronograph and averaged 1465 fps at about 14' from the muzzle. I'm not seeing excess pressure signs and accuracy is good, am I there?

Pull some boolits and compare the components. Figure out the primer, bullet type and then the fun part, the powder. Good luck...
I guess you could narrow down the powder selection fairly well if you use the Lee powder CC to grain conversion ruler, by weighing the charge and measuring the volume.

[Milky Duck]

if you are shooting the same projectile at same velocity...you have pretty much duplicated the load...beg/borrow/buy a factory round to get the correct overall length and then make up a dummy round so you can set up dies.... but agree with above,if you really want to get it super close in velocity you will need to use a chronicgraph on a factory round to give you correct baseline.

[45DUDE]

The Lyman book will get you close. They list factory load info.

[Screwbolts]

If is so self evident that even a blind squirrel should see it!! The box has nothing but marketing propaganda on it!! If you personally have not chronoed said factory rounds threw your firearm then the Propaganda on the box is just that!

MV propaganda isn't measured 14' from the muzzle.

Your there and beyond.

[William Yanda]

.98 x 1500=1470. You are (only) a couple of points off. Would another tenth grain be closer? What is the deviation?

[farmbif]

you dont mention the caliber or firearm. but one question I have is, what is the effect you desire to achieve ? are you just after velocity with a certain weight projectile?
as a reloader for a long time I wanted to work up loads to maximum velocity while at the same time getting the best accuracy possible for particular guns and tried different projectiles to compare each as far as velocity and accuracy without getting into loads of powder that do not go beyond what published data calls for or getting excessive pressure signs in the cartridge.
I really dont care what "factory" ammo can do. I care about what the ammo I can put together can do. just like you I guess. I'm not going to pay for factory ammo when ive got plenty of brass, many different powders, primers, several different molds and even boxes of jacketed projectiles.

[dverna]

There is enough variation shot to shot that testing 5 rounds of factory ammunition is about as few as you can use. Then there is the added issue that one lot of factory ammunition may differ from another lot.

You may be chasing your tail.

I have never tried to match factory velocity and cannot envision why I would. If you would share why this is important for your needs, it may be helpful.

[higgins]

SAAMI spec. for velocity measuring rifle loads is 15 feet from the muzzle. If factory ammo is measuring higher velocity than expected then it may come down to length of the test barrel, the difference in chronographs used, use of non-canister powders, or something else buried in the specs. I only wish I had learned of the 15-foot standardization years ago, but for my use my older measurements taken a few feet closer to the muzzle are probably close enough.

https://saami.org/wp-content/uploads/2019/02/ANSI-SAAMI-Z299.4-CFR-Approved-2015-12-14-Posting-Copy.pdf

[BrassMagnet]

I'm trying to duplicate a factory load, they say their MV is 1500 Fps, of course they don't mention barrel length or distance from muzzle the measurement was made. Today I ran a batch of my loads through my chronograph and averaged 1465 fps at about 14' from the muzzle. I'm not seeing excess pressure signs and accuracy is good, am I there?

I would like to suggest another way to look at this "factory duplication load" issue.
First off, there is no reason to complain about any of the comments previously posted in this thread.

If, for some reason, you are required to shoot your ammo sometimes and not your ammo other times through the same gun and it is important to you to get the same performance every time then a factory duplication load is important to you.

I used to compete in military matches and NRA matches. I had to provide my ammo for NRA matches and I had to shoot the ammo issued by the military for their matches. So I needed "factory duplication/military duplication loads" for my rifle. The ammo they issued even varied from match to match as sometimes it was M852 match with 168 HPBT, sometimes M118 Match with 173 FMJBT, sometimes M118 Special Ball with 173 FMJBT, and sometimes LR with 175 FMJBT.

Maybe you just want the different bullets available to you to impact the same place at the same known range.

I used a "Military Duplication Load data chart" posted in an old issue of the American Rifleman to know where in the load data to load a duplicate load. It was a reasonable method, but not precise as lot-to-lot variations in powder cause velocity variations in velocity. The juniors in our club wanted precise precision and fired test loads where they varied the standard load for their AR by a few tenths of a grain until their chronograph reported the exact velocity they wanted to make a perfect match for their previous load.

If you are not trying to match a specific velocity, but are instead just trying to make the "best" ammo for your rifle with "available" components while conserving on "wear and tear" on your rifle you might try this idea instead:

Minimum or suggested starting loads and maximum loads are near where the load developer saw pressure problems developing. Pressure problems would likely cause velocity variations. Velocity variations will cause the load to string vertically. When you see these limits to the recommended load in different load manuals, you will notice they are different. Powders react differently to different temperatures, barometric pressures, etc. I would not want to be close to either extreme end and of the two limits I would suggest the upper end of the load data is less likely to become dangerous than the lower end of the load data. Too little powder can change from "burn rate" to "detonation." Not good!
So here is the method: Use the highest suggested starting/minimum load and the lowest maximum load in the reloading manuals available to you. Now you have better minimum and maximum suggested loads. Now calculate the one quarter, one half, and three quarter points. Since these calculated values likely won't be easy to remember, round them to memorable numbers such as 26.57 to 26.5. The one half point of the powder load range will have you at the most linear portion of the load data so a one tenth grain variation in your powder charge will likely give a very insignificant velocity change. The one quarter and three quarter points will likely be nearly as insignificant in velocity changes if your charge varies by a tenth.
Now consider the middle of the road load as your load, or maybe the three quarter load as your load if you want a "little more performance" out of your load or even the one quarter load if you are just plinking and you want your barrel to last forever! Any of these three loads should be safe in any modern rifle in your caliber.