.223 Load Data Question (Pressure in relation to OAL).

[zippygaloo]

For .223 Remington 55gr FMJBT, the Sierra Manual says at an OAL of 2.250 it will take 25.7 grains of Hodgdon H335 to produce 3000 fps.

The Hornady Manual says at an OAL of 2.200 it will take 22.4 grains of Hodgdon H335 to produce 3000 fps.

Does the difference of .050 really increase the pressure that much to achieve the same 3000 fps with less powder? If so, why wouldn't everyone use the shorter OAL and save on powder?

Also, at what grain increments do I work up my loads? Do I go by what the manual says and increase according to fps (load data is usually shown in 100 fps increments)? Or do I just increase my loads by a certain amount of powder?

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[deadshot2]

If I recall correctly, the bullets used in each manual have two different profiles which would yield different pressures due to the bearing surface diffferences.

Their data was also derived from different test barrels. The length is only one component of the pressure. Bore diameter can also be a cause of the difference. Who's bore was more worn out than the others? Barrel length? Case? Primers?

One question, are you shooting these in a bolt gun or AR?

For my AR's, when I use H335, I load 25.5 with a Montana Gold (they claim it's the same as Hornady) bullet. It gives me 3015 fps from a 16: Heavy barreled AR. I load at max magazine length of 2.260 inches.

You point out the primary reason I have my own chronograph. Am even considering a Pressure Trace system to get my own pressure readings. Instead of a new rifle I might buy one of these.

 

[ma96782]

Yes Zippygaloo.....Deadshot2 has read the "fine print" in his manual. You should too and that goes for everyone else who hasn't taken the time to do so. You'll find out some verrrry interesting things about reloading in the "fine print." Reloading isn't just about picking load data out of the book and expecting to have "excellent results."

Books will usually have a warning about using particular components and platforms to get thier results. And, they'll warn that your results may vary. Not to mention that, subsitution of components will change results and could even be dangerous.

Example of a Warning:

IMPORTANT NOTE: Reloading data published by SPEER are for SPEER bullets. Many of our bullets are of unique construction; there is no such thing as "generic loading data" any more. Other bullet makes may produce significantly different pressures and velocities. We make no warranty that our published loads are safe with another make of bullet. You, the reloader, bear the ultimate responsibility for knowing your firearm, loading equipment, and techniques.

And, more reading............

Miscellaneous Questions 4

Aloha, Mark

 

[AMProducts]

I don't think I've ever gotten (one way or the other) the exact velocity quoted in any loading manual, and this is a horrible basis for making adjustments to your load. You really need more information, typically in the form of a chronograph to really make educated decisions as to what the outcome will be for a particular component combination.

As far as playing with charge volume, I typically make adjustments to rifle loads at .3grs unless I am very near the max. I use bulk powders, typically 25.0grs of a H335 like powder (very similar characteristics and charge weights), under a 55gr FMJ-BT loaded to 2.25" velocity is typically avg 3020FPS from a 16" AR with a Pmax of about 52,000PSI, so it's a fairly mild load by military standards (62,000PSI), but all of my guns eat it up. I typically load this with either Berry's 55gr FMJ-BT, or X-treme 55gr FMJ-BT which are both copies of the M193 bullet.

 

[speedtriple]

Zippy, you are assuming that pressure rises because the bullet is loaded shorter, but that may or may not be the reason. From my somewhat limited experience, setting the bullet out further so that it is almost in the lands of the rifling is when the pressure will really spike. At least in my AR, I can't set any 55 grain bullet anywhere close to the lands and still get it in the magazine.

You are just NOT going to find any magic load for your gun from the loading book, unless you are just dang lucky. Even then, without testing you won't know if it really is the best load. Since you are running a shorter barrel, the load data published will not result in velocity even close to what they state in your gun.

From my experience, a bullet from different manufactures will need different powders loads. The amount of bullet in contact with the barrel changes with the profile of the bullet. Less of a factor with the smaller bullets, but it is there just the same. Weather will have a HUGE difference in performance and that is where some of the differences you see in the published data might be.

Pick a safe starting point and go out and test and practice. Beg, borrow, a chronograph if possible. Not sure where you shoot, but maybe you can go out with me sometime and use my chrony. Just don't shoot it! I shoot at Tri County.

 

[zippygaloo]

I'm shooting out of a 14.5" chrome lined barrel on my AR. It's accurate, but obviously it's not exactly a precision rifle. With this in mind, do I really need to focus on exact (and same) OAL for all of my cartridges? Right now I'm basically trimming my cases to 1.751 and seating my bullets (Hornady 55gr FMJBT W/C) somewhere between 2.220-2.250 more often than not at or closer to 2.220 and a few times slightly shorter than that, but not shorter than 2.200. With my trim length and this particular bullet 2.220 seems to put the cannelure at the right spot. Sometimes I just eyeball seat to the cannelure.

Are either of these methods a right and safe way to do it for my type of shooting/gun?

 

[deadshot2]

under a 55gr FMJ-BT loaded to 2.25" velocity is typically avg 3020FPS from a 16" AR with a Pmax of about 52,000PSI, so it's a fairly mild load by military standards (62,000PSI), but all of my guns eat it up. I typically load this with either Berry's 55gr FMJ-BT, or X-treme 55gr FMJ-BT which are both copies of the M193 bullet.

Careful there, the Mil-Spec for the M-193 round is 52,000 PSI. Max pressure spec for the M855 is 55,000 PSI. Even the Mil-Spec for the popular M118, 7.62x51 cartridge is only 50,000 PSI.

This is all data from the Army Small Arms Ammunition Manual TM 43-0001-27.

SAAMI max for .223 is 55,000 PSI.

The SAAMI spec for .308 is 62,000 PSI.

For those that want a copy of the TM, go here Biggerhammer.net - Miscellaneous Firearms Technical and Training Manuals

Just follow the instructions for login and you can download the PDF.