question on velocity?

N8Will

What is the effect of temp on FPS? I just got a chronograph and I cant come close to book speeds. Im shooting in 30 degree weather not sure on humidity but it prety dry here, elevation is about 4200 feet. Im shooting a 280 AI with a 24 inch barrel, berger 168 VLD and Im getting an average of 2650 with H4831sc, and 2750 with IMR 4350. Is it just the temp or what?

FrancF

Not the expert. But what I do know some powders are more temp sensitive than others. Your Elevation can also play a small roll. In short, little things and effects can add up.

oneoldsap

Also remember that most reloading manual velocities are obtained with a 24" test barrel and 0 wind . My reloads are developed for accuracy first , bullet selection second and velocity third . Cronos are fun to play with and satisifying curiosity !

Okie743

quote:Originally posted by oneoldsap
Also remember that most reloading manual velocities are obtained with a 24" test barrel and 0 wind . My reloads are developed for accuracy first , bullet selection second and velocity third . Cronos are fun to play with and satisifying curiosity !


oneoldsap says: My reloads are developed for accuracy first , bullet selection second and velocity third . Cronos are fun to play with and satisifying curiosity !

Took the words right out of my mouth! I've had guys ask why reload and test a bullet you are not going to use for hunting when FIRST testing a gun and reload! I'm not testing the wound channels on the paper targets with high dollar HUNTING bullets when first testing the gun and reloads, I'm testing for accuracy. (and usually the high dollar HUNTING type bullets will not AVERAGE as good a group as a selected lower priced target type bullet)
What you found out about velocities published in manuals and actual chrograph readings for your gun is a good reason for buying a chrony.

Rocky Raab

Ditto to the above.

I note that a 168-gr bullet is quite heavy for the 280, and the Berger is intended as a target bullet. So I assume this is not a hunting load, and therefore velocity isn't a paramount concern - or shouldn't be.

Lastly, it isn't air temperature that has an influence, but gun temperature. The gun heats or cools the cartridge and powder within moments of the round being chambered. It's the temp of the powder at ignition that affects the burn.

N8Will

This is a hunting load. I shoot the berger 168 VLD hunting bullet. It does a great job on game. I don't want to start a fight on different bullets just trying to figure out why I can't get close to the book velocity. I know that I can't duplicate test conditions but I would think that a person should be able to get close.

Okie743

I've noticed the same as you when testing reloads and even factory ammo about velocities! Try running a factory load through your gun and see what ya get as compared to the published velocity!
Usually the velocity is less when read on a chrony for a reload indicated in most reload manuals for a given bullet, powder and barrel length as indicated in the manual! I've also seen longer barrel guns not shooting the velocity indicated for a shorter barrel gun per the manuals! (also write (log) your powder lot number on the reloads, the velocity and keep a heads up when you buy new powder lot for a re-checking! I can read the code lot dates on powders types and I buy the latest dated powder! Powder manu's will tell you how to ref their lot numbers to manu dates.

Another Jaw dropper: Also you will find that bullet drop tables are also just a reference guide to get in the ballpark!
Best to shoot the actual gun at known distances and see the ACTUAL bullet drop especially if you intend shooting at game 250 or more yards!

Rocky Raab

Are the "book" velocity numbers for that exact bullet or for a bullet that's only of a similar weight? Because substituting a different bullet can have as much effect as indiscriminately swapping powders.

More or less bearing surface, different actual diameters, harder or softer cores, more or less ductile jackets, presence or absence of cannelure or boattail and several other factors can all change the way a bullet reacts with the bore.

I'm aware of the current fad for using Berger target bullets on game. I think it's a bad idea, but won't belabor it.

Ambrose

The Hodgdon web site indicates that, for the .280 AI, 53 gr. of IMR4350 with a 168 gr. Sierra bullet yields 2760 fps. 57.7 gr. of H4831 and same bullet=2780 fps. Sounds like you are close, at least with IMR4350. What were you hoping for?

N8Will

Yes Im right on with the 4350 but the 4831sc is a 100 plus lower and it seems that it should be closer. Ive also been testing different Nosler loads to match the book to a tee and still the same Im at least 100 Fps lower. Im not a speed junky by know means Im just wondering if this is common? The only rifle I can seem to get on the money is my 250 savage, of the four other cals that I have shoot through my chrono the velocity's have been much lower.I don't care about how fast they fly but it just has me curious if this is normal, I still believe that accrately is the most important, getting this chrono has just opened my eyes to real world velocity.

Rocky I have a question for you, Have you ever used Berger VLD hunting bullets on game? or is that just an opinion?

Justjump

I load first for accuracy also and the chrono can help, If you have a known MV and the BC you can easily get an idea on trajectory. It's not absolute but it usually is very close. Saves on having to set up 6' tall targets at the 500+yd mark. It's a tool and in my opinion a very good tool.
I'm curious about the bergers myself, have never used them but I hear strong opinions from both sides. So far I'm lovin my accubonds

N8Will

Justjump, I love accubonds, but after seeing the effect on game with the Berger it wasnt had to try them. I understand that if you shoot a super mag of some sort they dont preform as well as they do in a mid range type of velocity. I killed a nice 200 plus pound whitetale this year and it dropped in its trac. My friend took his 280 AI on a pig hunt and killed five hogs between 150 and 300 pounds and all kills were very quick.I love the way they preform and the groups are awsome.

Willys 1948

I've found if your within 100-200 fps from published data your in the ballpark. Too many variables to expect closer. Shoot several and see what the high/low and Std. Dev. is and then base your trajectory off the average if std dev is tight. Unless your shooting the really long range stuff, you'll be really close.

I shoot a 300 win mag with calculated trajectory from BC and MV and drop a lot of whitetails at 300-450 yards which is about all my talent, breathing and optics can muster. After you start experimenting and watch an animal (or target) drop at these ranges, the 100 yard shots are not much fun any more.

Have fun with the Crony. I love mine.

jaegermister

I often run a series of .22mag rounds thru the chrono to verify operation. Manufacturers publish velocity on the box. I always get lower than published, about 5% ,maybe my barrel or such but I factor it in.
Much has been said here about the worth of a chrono, and I value all opinions. It was during my test firing of .22mag rounds that I noticed consistent groups coincided with consistent fps. But there are a lot of other things as important if not more.

Mobuck

A new or rough barrel will give lower velocities with equal pressures than a slick bore.