.223 reloads - chrono results

[MarinePride]

I loaded up some .223 for my Bushmaster with a 20" barrel and out of 10 chrongraphed shots I got an average velocity of 2883 fps. The high was 2947 fps and the low was 2810 fps. I'm wondering why my velocity is not close to what the reloading manual says it should be, or Hodgdons website for that matter. I'm using 25.5 grns. of Varget and mixed cases, mostly once fired mil spec brass. Some of the cases were completely filled using the charge I'm using and thats a starting charge, 25.5 grns that is. I was using 55 gr. Rem. FMJ bullets and CCI 400 primers with no crimp.

The Hodgdon website says that this loading should yield 3174 fps, so I'm a bit short. Granted these are only plinking rounds, but at longer ranges the velocity is important. So I'm just wondering how does one get the max charge of 27.5 grns. to fit in a .223 case? It just doesn't seem possible. Your experiences are appreciated and thanks.

 

[ocabj]

The chrono data in the reloading manuals is simply for reference. There are a lot of factors that come into play as far as true muzzle velocity.

First off, what test barel did the reloading manual say was used to get the data? Lots of times, the testers will use a 24" length barrel. This will account for the higher velocity. I'm pretty sure the Hodgdon data is based off a 24" test barrel. I know the Lyman has data based on a 24" length barrel as well as 20" barrel data for service rifle shooters.

Also, each and every barrel shoots differently. Some barrels may shoot a load faster than another, or slower than another. It's just the way it is.

Other times the lot of powder you have may be different than the lot used by the manufacturer.

Lots of varying conditions.

I'm betting the data you are looking at was gathered from a 24" length barrel.

As far as 25.5gr of Varget behind a 55gr bullet, that's pretty mild. If you want to pack 27gr of Varget in a .223 case, you'll want a long drop tube funnel. It works wonders. I use one when I load powder into a .223 case with 77gr and 80gr bullets. It definitely helps to pack in the powder to minimize powder crunch.

You may want to switch to a ball powder for the lighter bullets if you want to shoot light bullets very fast. Get military surplus virgin or pulldown WC844 of WC846. This powder is what is actually used in military 5.56 ammo. It is easy to meter and it takes no effort to pack in to the case since it is a very fine ball powder. You may need a magnum primer to get consistent ignition with this powder, though.

 

[nitesite]

Is your chamber .223 or 5.56?

If your throad/leade is long (5.56) and your bullets ogive is well off the lands, the pressure is lower and your velocity will be slightly lower. That's just one of may possibilities.

But I'm a student like you, not a teacher.

Here is a very good read:http://www.hornady.com/ballistics/internal.php

To illustrate the effects of variations in bullet travel before the bullet enters the rifling, we'll compare a standard load with adjustments made only in the bullet's seating depth.

In a "normal" load with the bullet seated to allow about one 32nd of an inch gap (A) between the bullet and the initial contact with the rifling, pressure builds very smoothly and steadily even as the bullet takes the rifling. Pressure remains safe throughout the powder burning period (B), and the velocity obtained - 3500 fps - is "normal" for this load in this rifle.

Seating the bullet deeper to allow more travel before it takes the rifling, as in these next two illustrations, permits the bullet to get a good running start (C). Powder gases quickly have more room in which to expand without resistance, and their pressure thus never reaches the "normal" level. Nor does the velocity; with the same powder charge it only comes to 3400 fps (D).

When the bullet is seated to touch the rifling, as in the accompanying illustrations, it does not move when the pressure is low (E); and not having a good run at the rifling as did the other bullets, it takes greatly increased pressure to force it into the rifling. As the rapidly expanding gases now find less room than they should have at this time in their burning, the pressure rise under these conditions is both rapid and excessive (F). Velocity is high at 3650 fps - but at the expense of rather dangerous pressure.
Many rifles deliver their best groups when bullets are seated just touching the rifling. Seating bullets thus can be done quite safely if the reloader will reduce his charge by a few grains. The lighter load will still produce the "normal" velocity without excessive pressure.

 

[tikkat3]

I get 27.5gr Varget in my brass. I use Lapua for everything. The Lapua Match Brass holds more than the factory loaded brass. The factory brass can sometimes hold 27.5gr, but it will be brimming-to-overflowing. The Match brass allows me to load 55gr V-MAX with only minimal compression, depending how the powder has settled in the case.

 

[MarinePride]

One thing for sure is that a chrono adds a whole new dimension to reloading. And to think, I've been without one for a long time. Very valuable tool for the informed reloader.

 

[CB900F]

Marine;

Speer #13 data, like Hornady, is derived from real guns, not test barrels. Speer shows 25 gr of Varget as a starting load for their 55 grain bullets. That charge yields 2969 fps, & max 27.0 gr gives 3216 fps. However, the test gun was a Ruger M77 with a 22" barrel.

Now here's another thing to think about. Both Hornady & Ruger used bolt guns to get their data. Hornady used a Remington 700 with a 26" barrel, so I thought Speer was a little closer to your 20". You have a gas-operated AR platform that bleeds off gas pressure to operate the gun. So, consider all the factors that have been mentioned: Shorter barrel, larger chamber, longer leade, powder lot differences, gas bleed, and for all I know yer D.I. still has it in for you & is sending bad vibes. So don't get married to the book velocities, there's too many things that can affect what your particular gun does.

However, do make a chrono log for your gun & keep good records of what you load & how those changes affect the velocity in your gun.

900F

 

[Clark]

Load books are good for beginners to keep them from blowing up guns.

But if you start taking them seriously, they will drive you crazy.
Ask me how I know

The standards we might expect from engineering resources are not there.
It is not source data.
It is a collection recipes massaged by a committee, that may have had access to the source data.
Take it with a grain of salt.
It is like weasel words.
It is like politically correct words.
It is like a prepared legal statement.

You want the truth?
Most handloaders can't handle the truth.

I can get 2782 fps 60 gr out of my 20" Bushmaster V-match with 15 gr Blue Dot, but that's not in a load book.
I made that load up.
It won't cycle the action.
Not enough powder.

 

[hagar]

If you want to shoot 55 grain bullets, use another powder like AA2230, 2460, RL12, BLC2. Varget really shines with bullets in the 69-80 grain range, there are better choices for light bullets.

 

[MarinePride]

Why did I select Varget in the first place?

Because it it the powder that lists the highest velocity using a 55 gr. bullet. It is now obvious that I'll never be able to fit enough powder into a 5.56 case to acheive that velocity. And to think that I loaded over a 1K of these, but have only fired a few hundred so far.

I also selected Varget because it's what I use for .30-06, .308 and .30-30 loads. Very good powder for .30 caliber 150 gr. bullet loadings.

Thanks to all who have replied. Maybe I need to get an indepth reloading book and not the Lees Modern Reloading.