Velocity. Theory V reality?

[SKULLANDCROSSBONES65]

G'day
How reliable are printed velocities in practice?
Do many of you check actual velocity for factory and/or home brewed loads?
What is the typical variations one could expect from factory and home brew?

I chronographed some .223 Rem in a 20" bbl. My average Velocity was 3215 F/S +-30. (Sierra #1365, 55gr SBT. 26.0gr of AR 2206H{H4895})
Is this a reasonable velocity spread or should I look at trying to improve my reloading procedures?

PS. Hi its been a while since my last post. life gets busy, I am getting lots of opportunity to get out in the paddock and trow lead around. Also get to introduce lots of first time shooters to the sport. Small groups/couples and familys etc. I am lucky to have access to 300,000 acres at my back door and a selection of rifles.

 

[griz]

The listed velocities are very accurate for their components in the rifle they used. The thing is rifles vary a lot. If they used a brand new 24 inch tight chambered barrel, and you used a worn out 18 inch barrel with a long throated sloppy chamber, you might be a couple hundred FPS under their velocity. That said, your results seem to be pretty consistent and the velocity is good. Is your's higher than what they got?

 

[MTT TL]

Depending upon the company the numbers might be considered optimistic. For safety reasons a manufacturer will almost never list numbers that are lower than what is the maximum expected velocity.

Velocity can also vary a bit based upon all kind of environmental factors such as elevation, pressure, temperature.

As noted by griz the weapon is the most important part of the equation.

 

[SKULLANDCROSSBONES65]

G'day.
My rifle is a brand new "HOWA 1500 Mini action, 1 in 8" twist, SS with laminated R/H Thumb hole stock.
Got it home last night and put the first 50 rounds through it today. (No work today as the machine I operate would not start. Waiting for an auto sparky to work his "White men Magic").
Sierra stats use a 24"BBL and 26.1gr of AR2206H {H4895} produced 3300 F/S.
I'll see how these projectiles perform. I may need to go heavier with the tight twit rate of the rifle. Initial observations are good. It may become my go to rifle as it is softer on me than my .270.

 

[jmr40]

I find the data listed for MOST factory loads to be optimistic. Some can be pretty close, others significantly slower. For the most part my hand loads are pretty close to book numbers when shorter barrel lengths are factored in. Most load data is for 24-26" barrels. I may be 20-50 fps slower than that with my 18-22" barrels, but that is to be expected.

The individual rifle can make a huge difference too. I have 2 rifles in 30-06. Rifle #1, even with a 22" barrel, is always very close to published data for a 24" barrel, less than 50 fps slower. Rifle #2 is ALWAYS 90-100 fps slower than rifle #1 with any load I've ever tried in it. Both have 22" barrels.

I also have several 308 rifles, two with 22" barrels. One of them is ALWAYS a little faster than the other, but not enough to be a concern. Usually only about 20-25 fps. But the difference is consistent with any ammo tried.

 

[buck460XVR]

I find the data listed for MOST factory loads to be optimistic.

Same here. Not that they embellish, but they use test equipment to get peak performance. Revolver ammo is a good example. Many times they use a long test barrel without a cylinder gap to test ammo and get significantly higher velocities than one could get from any revolver.

That said....as a reloader I do not seek ammo that gives me the highest velocity, but ammo that gives me the best consistent accuracy. Consistent velocities generally give the most consistent accuracy, especially at longer ranges. Your standard deviation(velocity spread) for factory ammo seems to be about average, so accuracy is probably more dependent on you and your firearm than the ammo velocity.

 

[Don Fischer]

Chronographs, the best and worst idea going. Most of them pretty much tell the truth, doesn't really matter if we want to know the truth. ES is really searched for by some guy's in fact I was one of them. What I found was better than a close ES is a tight group! Normally knowing the velocity of a bullet has it greatest vale to me in being able to plot bullet path. Without knowing velocity it can still be worked out but it's a lot of shooting to get there! Years ago before the chronograph became so easy to come by we were blissfully ignorant! My loads were doing what the manual told me, no sweat. And factory loads were the same way, fast as the manufacturer said! Blissful ignorance. Then the only thing that mattered was if we could hit what we aimed at!

 

[44 AMP]

I find the data listed for MOST factory loads to be optimistic.

I think the data is accurate and your optimism is misplaced. The factory data isn't optimistic. Its actual. WE are optimistic, thinking we should get exactly what they got.

Besides the fact that listed velocities are averages, we aren't using the exact same components. Something close is reasonable. Exact matches to published velocity speeds is serendipity.

Every gun and ammo combination is slightly different. I've seen 100fps spread firing the same ammo through 3 different guns with the same barrel length. Usually that much spread isn't common, but some difference between individual guns is virtually a given.
Treat the published numbers as guidelines, not goals or required performance.

 

[Bart B.]

SAAMI spec test barrels for both 308 Win and 223 Rem are 24 inches long. Few commercial barrel groove diameters are as small as those test barrels. No wonder our handloads and commercial ammo easily shoots bullets slower in commercial barrels.

What load data or commercial ammo is developed with SAAMI spec test barrels, pressure systems and chronographs?

Two people shooting the same shouldered rifle and ammo from a bench can have a 50 fps average velocity spread difference.

 

[Jim Watson]

I load to chronograph readings with my ammo in my gun.
Published velocity is usually from a long tight test barrel, probably faster than a real gun.
In particular, factory data on the nice clean Finnish powder is pure fantasy.

 

[rock185]

I have little doubt that printed velocities are accurate for the test guns and components used. I chronograph about everything I shoot though, because my guns are not the test guns. It is not at all unusual for me to use a different manufactuer's case, primer, or bullet. So obviously, my data most always varies from manufactuer's data. Also, within my humble experience, and as previously mentioned, velocities from similar guns with the same barrel length can vary considerably. Though it may not matter much in the real world, I do prefer my hand loaded ammunition to be consistent as possible as to extreme spread, SD, etc.............YMMV

 

[44 AMP]

Getting a chronograph was an educational experience for me. After testing a lot of different loads in different calibers and different guns, what I learned was that individual guns differed from published data about the same amount as they differed from each other.

And that a handful of fps didn't make any difference to me.

So, I stopped bothering to use a chronograph. Instead, I look at how the bullets perform downrange.

IF your thing is 10 shots in one bullet diameter hole, or as close as you can get, then fine, use every tool in the box to get there.

For me, I'm in the "good enough to work for what I need" group, and so, my standards are a bit more ...flexible.

 

[T. O'Heir]

"...printed velocities in practice..." Assuming you mean those in manuals, they're averages just like the loads. Read the whole manual.
"...in a 20" bbl..." That'll be different from any manual. All manuals reflect averages using the exact components, hardware and weather conditions on the day of the tests only.
"...For safety reasons a manufacturer will..." Nope. If they get anything that is not within SAAMI spec, that load is scrapped.

 

[Bart B.]

"...printed velocities in practice..." Assuming you mean those in manuals, they're averages just like the loads. Read the whole manual.
"...in a 20" bbl..." That'll be different from any manual. All manuals reflect averages using the exact components, hardware and weather conditions on the day of the tests only.
"...For safety reasons a manufacturer will..." Nope. If they get anything that is not within SAAMI spec, that load is scrapped.

SAAMI lists three average muzzle velocities for 150-grain bullets in a 24" barrel for the 308 Win cartridge; 2800, 2900 and 2980 fps. Which ones are listed in commercial ammo specs?