busted by my new chrono

[bamaranger]

So I got a chronograph as a Christmas gift, ..... KC ProChrono Digital and was really pleased about it. Bamaboy and I set it up in the house Christmas Day and tried to Chrono his airsoft guns.....yuck yuck....no good.

Today, I set the chrono up outdoors and brought the Rem 700/.270 out with my "pet" load, a 110 Sierra and 55.3 grs of IMR4350. The Sierra Manual listed it a 3200 +, I expected 3100+, and felt CERTAIN I would break 3000 easily, which was the object of the light bullet load. Did not feel I could get 3000 fps from the 22" tube with a 130 gr slug. So.......

Arrgh..........2850!!!!!!!!! Heart break, disapppointment....that's probably about what a .243/100 gets.

Obviously, I have some load development to do!!!!!

[sourdough44]

I agree, chrony speeds can differ a lot from book numbers. At 1st I thought you shot the chronograph with your title.

[Sport45]

Obviously, I have some load development to do!!!!!

Nah, if the load has been working for you leave it alone. Take the chrono back and forget it.

No critter or target you shoot will know the difference.

[solocam72]

I agree with sport45, I let my 7mm rem mag velocities kinda get to me, 3000 fps with a 140, was figuring closer to 3200 with my 26" barrel but not gonna happen, the load works and works really good so it is what it is

[Sarge]

busted by my new chrono

Welcome to reality, LOL. The first thing my Beta Master did was prove that a couple of .44 Mag loads were about 150 fps south of where various written works estimated them. Really bothered me until I realized I'd already made several hundred pounds of venison, courtesy of those wimp loads.

My primary use of a chronograph is for exactly what you did- to insure my reloads are producing the velocity--and consequently pressure--I am trying to achieve. I also use it to measure consistency; but I have arrived at the conclusion that Standard Deviation is irrelevant compared to what the target is telling me.

Just FWIW, H4895 has consistently produced velocities at or near published velocities for me in a number of cartridges- and excellent accuracy as well. I always liked the stuff, but the both Beta Master and the Target confirmed it was going to be my 'go to' rifle powder.

[Bart B.]

Bamaranger, I doubt your using a barrel with the same bore, groove and chamber dimensions used to base any printed data on; if your bore and groove diameters are larger, it'll shoot the same load slower. And you're not using the same lot of powder or primers either. And probably not the same neck tension on the bullets. To say nothing about how hard you hold the rifle to your shoulder when firing it as that alone can cause over 70 fps difference than someone else. Most noticable is the velocity spread between a given barrel and ammo fired with it hard fixed in a test fixture (as SAAMI does with a universal receiver; see my post below) compared to it in a rifle held by someone against their shoulder; that's gonna cause 100 fps difference; or more.

Therefore, a few hundred fps difference between a quoted velocity and what someone gets is as normal as sunrise every morning.

[old roper]

bamaranger, I know the feeling hard to shake off.

[jaguarxk120]

The Lyman 49th Handbook lists a 26 inch barrel that was used for testing the published loads. I would say that extra four inches of barrel accounts for something.

The chronograph has given you the velocity of thay bullet in your rifle, now is the time to use the ballistics calculator, it will show you where the bullet drops at distance. Also the energies developed.

[Dan Newberry]

I missed the word "by" in the thread title at first...

I thought I was reading a juicy story about how you shot your chronograph with your .270.

By the way... if the chrony is too close to the muzzle, sometimes powder blow through can throw off your numbers. Make sure it's at least 10 feet from the muzzle...

[kimbers rule]

My chrony's made me a lier a few times but 55 grns IMR4350 behind a 110 is kind of cold. 3000 fps should be easily doable.

[Bart B.]

A few examples of what the pro's use to measure velocity and pressure for load development.

http://www.newlenoxordnance.com/univ...--barrels.html

http://www.youtube.com/watch?v=VmwkZKVDLzE

http://wisemanballistics.com/product/

http://www.drello.de/english/ballistic/receiver.html

http://www.ketmer.com/hsp/testing/index.htm

http://www.bsn.it/prodotti/modReir.php

Test barrels are made to strict SAAMI specs for chamber, bore and groove dimensions.

[buck460XVR]

I got a chrony after reloading for quite a few years. I too was surprised when my "pet" loads were shy of published book values. Since I had been reloading for years for acuracy and not velocity, I decided not to worry about it. As others have stated, most animlas shot in the boiler room never notice the difference.

[Slamfire]

I think the easy availability of chronographs really busted the bubble on wildcatters.

The golden age of wildcats was in the 50’s/60’s. If you read vintage publications shooters were making velocity estimates based on things like bullet drop over 200/300 yards. Wildcatters could make outrageous velocity claims on shoulder angles, (Weatherby anyone?) straight cases, case capacity because no one had chronographs to check their claims.

If they did get high velocities, it was due to extremely high pressures. P. O Ackley comes to mind with his claims of velocity increases with his blown out cases. He just did not get a little more velocity, he got a lot more, and it was due to extremely high pressures.

Below are comparisons of Ackley's published data compared to pressure tested data.

49th edition of Lyman Handbook, the max load of a standard 30-30 with a 150 grain bullet and using 28 grs IMR 3031, the velocity is 2145 with a pressure of 38,000 cup.

In Ackley’s own handbook, the maximum load for a 30-30 AI for a 150 grain bullet using IMR 3031 is 38 grains for a velocity of 2700 fps.

From web data, the case capacity of the 30-30 Ackley vs the unImproved Winchester parent differ by 5% http://www.gmdr.com/lever/3030atext.htm yet here you have Ackley stuffing in 10 additional grains of powder and claiming a velocity increase of 125% over the standard 30-30.

The only way to get those sort of velocities through incredibly high pressures.


If you go to your 1957 Gun Digest, factory ballistics for the Winchester 180 grain Super Speed 30-06 is 2700 fps. Modern reloading data shows you can push a 180 Barnes with 55.7 grs IMR 4350 to 2685 fps, in close agreement with older factory data.

Ackley’s handbook gives reloading data of 61 grains IMR 4350 with a 180 grain bullet for a velocity of 3053 fps.

Noslers shows a max load for the 30-06AI of 56.5 grs IMR 4350 with a 180 gr bullet at 2835.

For the 30-06AI Ackley is putting 5.3 additional grains of powder in the case and claiming a velocity increase of 113% over the parent cartridge. His data is pushing bullets 218 fps faster than modern pressure tested ammunition of the same case.

The only way to do this is through incredibly high pressures.

One of these days we will have cheap pressure testing equipment (or I hope we will have cheap pressure testing equipment) and even more of the outrageous claims that have carried down from the wildcatting 50’s/60’s can be tested, by enough people, and found false.

[showmebob]

My new chrono taught me that my medium test loads exceeded the "book" max fps. I didn't even test the max load, just pulled them.
I found one other guy that was having the same problem. His powder was from the same year as mine. I believe there was a problem with the powder
I was using all the same componets exactly and weighed the charges on 2 different scales.
I feel safer now using the chrony for load development.

[mehavey]

The chrono is only half of what you need to take max advantage of the flex in handloading. The other instrument is an internal ballistics program like QuickLoad. Together they make for a very adult rocket chemistry set.

BTW: QuickLoad would have told you that you'd not break into the 3's column w/ that 22" barrel. But it also would tell you that you've got a long ways to go before you have anything close to pressure limits -- approaching 3,200fps

[Goatwhiskers]

A chrono can give you a lot of comparative data if you keep good records. When are people gonna learn that it's bullet placement, the animal ain't gonna know whether the bullet traveled at 2800 or 3200, and as far as shooting "flatter" the average shooter can't tell the difference. GW

[reynolds357]

The only thing I have ever chronoed that did what was advertised is WBY factory ammo.

[Mike / Tx]

I use mine to compare what few factory loads I shoot do in comparrison to my handloads. In most cases I try to stay within the velocities I get from the factory but for a few rifles there isn't any factory loads. For those I am simply on my own but I DO stick to within reason, and don't try and get overly rambunctious with things.

I've been at it long enough to know when a velocity for a certain load is pushing things, and that is another good thing about having the chrony out in front while working up loads.

[hoffbill]

Like several others have said, I like the chrony to verify the actual velocity. That info is useful for keeping safe pressure, building a trajectory card for longer range shooting where a few hundred fps in muzzle velocity can make a significant difference in amount of bullet drop especially past 350 yds.

I was loading some 9mm practice ammo a couple years ago and was having misfeeds in my semi auto pistols. I shot through the chrony and found the powder I was using was producing 950 fps instead of 1100+ predicted by the charts. I switched powder, it ran 1150 fps and have had no more misfeeds.

I enjoy shooting groups from the bench so I entertain myself by tweaking various loads and bullets for my rifles trying to find the magic recipe that is better than the rest, but so far it seems my rifles can only shoot as good a group as they can shoot and that is as good as it gets. Chrony is fun for measuring consistency and velocity difference I get by changing a load by half grain or 1 grain, and using different primers, or cases with the same bullet or load. I find all that interesting, but mostly it is also an excuse to shoot alot and keep loading more.

[chris in va]

My ProChrono pointed out three things.

Using dippers gives me a terrible extreme spread.

My x39 loads through my carbine were 400fps less than expected.

The countless 223's I made for my Sport were only 2700fps. Considering I was shooting for 3100, pretty embarassing.

At least my Garand loads were dead on.

[Mobuck]

That's why I load by book, case expansion, AND velocity over the chrono. In some loads it goes the other way and I find I've hit the velocity goal under the book load.

[Wyoredman]

The countless 223's I made for my Sport were only 2700fps. Considering I was shooting for 3100, pretty embarassing.

My Chrony pointed this same thing out to me, but with LC military surplus ammo! Shooting the LC stuff through a 16" barrel didn't even come close to the magic 3200 fps that is held out to be the standard velocity of the M4 rifle. I giggle when when I see it printed now!

I did get the LC ammo to come close through my 22" DPMS varmint barrel, though!

[jimbob86]

What my Chrony told me was pretty much what my reloading manual told me: that rifles were individuals, and different loads would perform differently (velocity, pressure, POI, all of it) in different rifles. The same make and model of gun, same caliber and twist rate, produced only 6 years a apart, in the same shop (by the same people, in all likelyhood- 1950's production) had distincly different results with the same bullet and powder. There are so many variables in internal ballistics ..... this is why we start at the START LOADS, and work up ..... and restart anytime one component is changed.

One load might work as advertised and others might not ..... you won't know till you try.

[Brian Pfleuger]

It's a good idea to verify the chrony by using some 22LR Match ammo. It tends to be very close to published velocities.

Some cartridges seem to run closer to published numbers than others... I have found factory 17HMR and 7mm-08 to both run very close to box numbers. .204Ruger and 22-250, not so much.

[GeauxTide]

When I bought my Oehler 33 in the 80's, I neglected to read the manual. There is a setting in the chrony for the distance from barrel to first screen. Mine was set for 5 feet and I placed the screen at 10. After I set for 10, correct velocities.