velocity improvement

[Hog head]

I've been reloading for my .223 rem and it seems I con only get about 2500 fps out of it.The expected velocity for the max load is 3600.The barrel is 20 inches long.The groups are good but I'd like to be able to reach out a little further.i'm using imr4320 powder is there one that can do a bit better?I read a post earlier that confused me,wouldn't a faster powder do the trick having the short barrel?Or is it the other way around.

[butta9999]

Powder has nothing to do with it. What bullet weight are you using and what primer. I will check with all data i have to compare. Slower burning powders are generally used with heavier bullets but also can produce great verlocities with lighter bullets.

Most gun guru's say you loose between 100-150fps for every inch of barrel lost.

Even if you had a 24inch barrel you would only loose about 400fps.

But in saying that you have posted a very vague thread, what is the exact receipe you used.

[Hog head]

The recipe is: bullet 40 gr speer tnt
powder 26gr=3267 fps-27.7gr=3456fps
primer cci #450 magnum
I ran the recipe with four shot groups min.charge to max charge in .5 gr. increments.The average velocity never went above 2500.the accuracy was excelent in two groups and ranging from bad to miserable in the others.I picked up this load on the hogdon website and substituted nosler bullets with speers.I can't rember the c.o.l. because I'm at work and my log is at home.

[Sport45]

What rifle and twist rate? And how far is the chrony from the muzzle?

I don't have an answer, but hope to help you find one. I use a lot of IMR4320 in my .223rem and would like to see the answers you get.

[Bart B.]

butta9999 says:

Most gun guru's say you loose between 100-150fps for every inch of barrel lost.

That's 4 to 6 times what I've seen in print; anywhere. But then we may be looking at data from diffferent "guru's." My own .308 Win. rifles with barrel lengths from 21 to 32 inches show about 20 to 25 fps change per inch of length. One barrel was originally 28 inches long that, when its throat wore out, was set back 2 inches, rechambered with the same reamer then shortened to 22 inches. The same load with 180 grain bullets dropped from 2625 to 2490 fps; 22.5 fps per inch.

The only thing I've witnessed that causes that much difference is the bullets are way undersized or the bore is way over sized. One example folks have seen is Argentine M1909 Mausers rechambered for .30-06 that went on the market some 30 years ago. Their 24-inch barrels had .303 bores and .311 grooves that reduced resistance to .308 diameter bullet entry from the '06 and muzzle velocity was 200 to 300 fps lower than normal.

Something's amiss in Hog head's situation. Could be his chronograph's mismatched to the screen spacing or has errors in its computing. I've seen this happen before. He needs to verify each element is exactly what it should be.

[Hog head]

The chrono was about six inches from the muzzle,I'm not sure of the twist rate.I've checked it with a bore swab several times and can't get the same twist rate each time.This isn't the first time I've had this velocity problem,it seems to be more pronounced in the smaller bullets.
My chrono reads 500fps avg.for my .22 buckmark pistol with a 5 inch barrel.That dosen't sound right to me,seems slow.Is that the problem mabey?

[xsquidgator]

The chrono was about six inches from the muzzle,I'm not sure of the twist rate.I've checked it with a bore swab several times and can't get the same twist rate each time.This isn't the first time I've had this velocity problem,it seems to be more pronounced in the smaller bullets.
My chrono reads 500fps avg.for my .22 buckmark pistol with a 5 inch barrel.That dosen't sound right to me,seems slow.Is that the problem mabey?

Yeah, your chrony sounds like the problem. 22LR out of a rifle ought to be doing about 1250 fps and something close to that out of a pistol. When I suspect chrony errors I use my 10/22 and some of my ammo that I've chrony'd before.

Even with "well behaved" loads I've found that I need to be careful with mine (PACT) if I'm working up a load over multiple range sessions. A load that clocks at 1900 fps one day may read as much as 100 fps different another day. Maybe your screens are too far apart or some other problem with the chrony. What kind of chronograph are you using?

[RidgwayCO]

IMHO, at 6" distance your chronograph is too close to the muzzle of your rifle. It's picking up the shockwave instead of the bullet. All the chronographs I've ever used state that the device must be at least 10 feet from the muzzle, and more distance may be better. With a 40gr bullet, your velocities should be much greater.

[kraigwy]

At 6 inchs from the barrel I believe the muzzle blast is interferring with your readings.

I check my rifles at 15 ft, (sometime farther for magnums) and about 6 ft for pistols.

Back up and try it again.

20 inchs isnt considerd a SHORT barrel for a 223, but still, I think loosing 100-150 fps is a bit off. Though I will admit I haven't started cutting down a 223 barrel to check.

But, if you are getting good accuracy, and the ammo works the action, who cares how fast it is.

[Unclenick]

Note: I see Ridgway and Kraig beat me while I was composing, so the first paragraph is repetition.


6" is way, way too close. Gases leaving the muzzle cast shadows that can trigger a sky screen. The small gas bypass blast that usually preceeds the bullet out of the muzzle is probably triggering the first screen early in your near setup. I've read a number of reports of false triggering by muzzle blast, and readings that don't reflect expected bullet velocity and that don't change much with powder charge are a common symptom. You have to get the chronograph far away from the muzzle blast to prevents false triggering the screens. There is a reason you see velocity data published in the Rifleman or other magazines listed as being taken at 15 feet from the muzzle (15 feet to middle distance between sky screens). 10 feet minimum to guarantee avoiding this effect, IME.

4320 is too slow for the bullet weight. A full case barely gets pressure to the bottom of the start load range. Your maximums from the recipe are significantly compressed. Moreover, slow powders with light bullets have a tendency to cause secondary pressure spikes in the muzzle. I would not use it. You want Reloader 10X (which was developed specifically for light bullets) or IMR 4198. A fast powder raises peak pressure sooner, but sustains pressure less well further down the barrel. Slow powders do the reverse, but they also require something close to maximum cartridge pressure to burn efficiently and consistently, so you have to pick one that isn't so slow that a case full fails to reach adequate pressure.

In this instance, with a COL of 2.05", you should be able to work up to from 22 grains (start) toward 25 grains of Reloader 10X to get about 3500 fps. Working up from about 21 grains (start) toward 24 grains of H4198 should be almost as fast (3480 fps).

FYI, four more inches of barrel would add about 35 fps per inch (about 140 fps total) barrel with the H4198 load, while it would add about 38 fps per inch (about 150 fps total) with the Reloader 10X load. The 10x gets a little more because it is a little slower and keeps the pressure up a little more toward the end of the barrel. That's what the extra grain of powder is doing for you.

[Hog head]

I just checked the chrony(pro chrony) again from 10 feet away,you guys were right on.velocity came up to 1050ish.Rechecked from 1 foot 500ish.It's a borrowed tool and I don't have the instructions or this could all have been avoided.No telling how mach of my data is wrong.Too bad I have to do all that shooting all over
To answer KRAIGWY accuracy iis most important,but speed is a close second.If I understand correctly speed=flat flat=far.
UNCLENIC I also have some h322 would it be any better, worse ,or same?I have a pound of it just lying around waiting for it's day in the sun.Just trying to be cheap.Any other powder sugestions, maby I could bum from my pal before I go out and buy another dud.Thanks for the help people.

[wncchester]

"No telling how mach of my data is wrong."

Actually, there is. All data you got at less than 10-12 FEET from the start screen is bad.

[kraigwy]

To answer KRAIGWY accuracy iis most important,but speed is a close second.If I understand correctly speed=flat flat=far.

We have little knobs on our sights to adjust for Flat, We dont have knobs to adjust for accuracy.

[Unclenick]

Speak for yourself, Kraig. I have several of them located at different points on my head. They're adjusted after calling a bad shot, and after verifying it through the spotting scope, banging my head against the head knobs on a wall or bench or shooting mat.

Hog head,

H322 is still too slow for your bullet weight. 100% fill, uncompressed, won't quite make starting load pressure.

[Shoney]

Noone has yet talked about primer effects. Hog head is using CCI 450 Magnum primers. Data I have seen recently indicates there is actually a reduction in velocity using mag primers tested against identically loaded rounds with Standard primers.

My data shows Standard primers being used in most loads with a recommendation for using mag primers only with ball powders, especially in gas guns. Hog head has not mentioned which weapon he is using.

Hornady data with 40gr bullet, bolt weapon, 26" barrel, 1 IN 12" Twist, Rem 7 1/2 SR primer, Rem cases
AA 2460 yieids 3800fps
IMR 4198 yieids 3700fps
Viht-N-130 yieids 3700fps
H 335 yieids 3700fps

Hodgdon online shows 40gr bullet, bolt weapon, 24" barrel, 1 IN 12" Twist, Win SR primer, Win cases
none of their velocities exceed 3700