Printed Velosity vs. Real Velosity

[MattStevens]

Am I the only one. I have been reloading rifle rounds now for three years. I load 338 Win Mag for Mod 70 Classic Stainless w/ Boss, 7mm Rem Mag for Vanguard VGX Deluxe and 243 Win for my 1957, Pre 64 Model 70.

I have followed both Nosler Data and Speer Data. I never get the velositys listed with the load, on any of my rifles. It is usually 150-300 fps slower than the load data indicates. I place my chrono about eight to ten feet from my muzzle????? Anybody else experience this? Any explanations??

 

[2ndtimer]

Where to start? Each and every rifle is unique in and unto itself. It would be shocking if you were to record velocities that were very close to what Nosler or Speer came up with. Also different lots of the same powder can sometimes vary by a bunch. Temperature plays a role, as does elevation (seriously, the thinner the air, the faster the bullet travels). There are an infinite number of variables that can and do affect the ballistic performance of a given load.
Now to the more obvious. Nosler usually uses custom barrels to test their loads and they are frequently made with minimum chamber dimensions and sometimes are longer than standard length barrels as well. How much have you shot your rifles? If you are an avid reloader/shooter you can wear out a barrel to the point where you will lose 200 to 300 fps from a load that previously reached those higher velocities. As the throat erodes, it reduces the pressure the load generates, ergo, lower velocity. These would be some of the reasons for the disparity between your loads on your chronograph and the published loading manuals. Even identical model rifles with identical loads can vary by over 100 fps from the factory. I guess that is why we should chronograph our loads. (Then cross our fingers that our chronographs are accurately measuring the velocity! :roll: )

 

[MattStevens]

Thanks for the insight. I have probably shot the 338 Win the most. I would guess I have put between 600 and 800 rounds through this gun. Much less for the other two. I always clean my barrels very well with both powder solvent then copper solvent. JB bore scrub about every third or forth cleaning. All three rifles shoot well, but I read about the velosities others get and wonder. I have never however, exceeded the recommended max loads. Hummm.

Thanks,

 

[2ndtimer]

Based on your number of rounds fired, you should be okay barrel wear wise. (Unless you were rapid firing during a prairie dog charge, or something :wink: ) Oh and welcome to the forums, sponsored by the best dang bullets made. Hope to see you sharing with the rest of us.

 

[MattStevens]

Thank you. I am very gald to have stumbled onto the sight and happy to be a member. I have read through much of the posting and it seems there is a ton of experience and information here.

Matt

 

[Anonymous]

Good post 2ndtimer. Yup there are alot of variables that can give you different results.

 

[skb2706]

Printed velocity = ellusions, dreams, smoke and mirrors, absolute ideal indoor labratory conditions, tight chambers, select barrels, all things not available to the average Joe shooting at the range.

Real velocity = real velocity, exactly what you get

Lets assume that the group assembling the data for print does not use a low end factory rifle, low end loading equip, low end chronograph while shooting at the local outdoor, crowded rifle range.

 

[Guest]

My sons and I load everything from 30-30 to .470 N.E.. I have a Oehler Chronograph and the only 2 firearms I can equal the published data with are a couple of .308s. Both are custom built with Shilen Match Grade barrels. Both of these guns shoot 100 to 150 FPS faster than published specs. All my other guns are factory guns that shoot 100 to 200 FPS slower than the published data. Bottom Line: It's all in the barrel & YOU'RE NOT ALONE.

308XP

 

[brianm]

your not the only one i get about 150-300 fps slower in my rifels
but in my ruger 45 colt bisley 5.5" i get about 150-250 fps faster
whats up with that :? :?