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When working up a new load, is it possible to use a chronograph in order to stay within safe pressure limits? I have seen reference to this in several articles but have not seen an explanation of how this is done. I am thinking in particular of a situation where a max load of powder from a manual does not reach the velocity reported in the manual and another grain of powder needs to be added to reach this velocity on the chronograph. What do you guys say?
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short answer is sometimes....
It depends on what you are comparing. If the book says that a max load for a rifle will get 3000fps and they tested using a 26" barrel and your rifle only has a 22 then going up to 3000fps might be over max in your rifle.
I have found at times that I have worked up loads and did not see any of the classic pressure signs and thought that I was under max, then ran the load over the chorny and thought wow I better back this off a bit. I know some people use them religiously in there load work up but I do not find it all that usefull for pressure but it can work givin the right circumstance.
Edited to add
ussually one will get sings of pressure in there rifle like flat primer pockets and sticky bolt before you can tell on a chorny but a chorny can certainly save you if those signs are not present. YMMV
Last edited by heavywalker; 02/11/10.
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John Barsness (Mule Deer on this site) has covered this in articles and on posts on this website, as I'm sure others have, as well. From everything I've read, a chronograph is THE best pressure indicator available for reloading at home, with the exception of a strain gauge system used correctly (and the "used correctly" part is an important qualifier).
You might do some searches for posts by Mule Deer (double check his name on the Ask the Gunwriters forum for whether there is a space or not) with the keyword "chronograph" or "chrono" to see what he has said.
A couple things your chronograph can alert you to:
1. smaller velocity increases for a given powder increase increment
2. when your velocity decreases (rather than increases) with more powder (goes over the top)
I'm sure others will be along with more info, but that will get you started.
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Heavywalker,
Velocity seems good, bolt lift is good and primer pockets do not loosen before at least 7 or 8 loads but I do get the little round ejector marks on the head of the case. Any thoughts?
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first off what brass are you useing.
If you are using Rem, Win, Fed, you are good to go if you are getting 8 loads. For that matter pretty much any brass with 8 loads is going to start getting loose primer pockets.
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Yes, you can.
My two cents and my opinion.
Do not exceed the maximum listed powder charge regardless of velocity. Some barrels are "slow" as in not being able to reach max velocity at max pressure. Shorter barrel lengths than used in testing can also produce lower velocities at max pressure. Some folks are willing to exceed max listed powder charge to reach max velocity or beyond - opinions vary - I don't and I prefer to stay on the safe side.
Also, sometimes max pressure is reached before max recommended powder charges or reaching published velocities with a "slow" or "tight" barrel. This not usually the case, but it can happen. Always look for other signs of pressure when working loads up.
Once you reach the listed velocity be very, very careful about going beyond that even if you have not reached max recommended powder charges. Velocity is related to pressure and exceeding listed velocity (might/could be/probably is) be an indication of exceeding max pressure.
I don't have as much experience that some here have, but these are the guidelines I follow.
fish head
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I am using Nosler Brass in a 338WM and 210 ttsx. Rifle is rem 700. After 7 firings they are not as tight as when new but are not at the point of falling out either.
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7loads before loose primer pocket is good IMO. The ejector marks might raise some concern if they are deep in the brass and or leave a ridge on the case head if they are just little round marks with on indentation or they are not causing any burrs then it may be that your rifle just does that.
Just for piece of mind you might back your load off a couple of grains with new brass and see if the ejector mark is still there if it is then your load is probably fine and your rifle is just one of those that makes ejector marks on brass. i have a couple rifle that do the same thing.
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Yes, you can.
My two cents and my opinion.
Do not exceed the maximum listed powder charge regardless of velocity. Some barrels are "slow" as in not being able to reach max velocity at max pressure. Shorter barrel lengths than used in testing can also produce lower velocities at max pressure. Some folks are willing to exceed max listed powder charge to reach max velocity or beyond - opinions vary - I don't and I prefer to stay on the safe side.
Also, sometimes max pressure is reached before max recommended powder charges or reaching published velocities with a "slow" or "tight" barrel. This not usually the case, but it can happen. Always look for other signs of pressure when working loads up.
Once you reach the listed velocity be very, very careful about going beyond that even if you have not reached max recommended powder charges. Velocity is related to pressure and exceeding listed velocity (might/could be/probably is) be an indication of exceeding max pressure.
I don't have as much experience that some here have, but these are the guidelines I follow.
fish head Does it follow then that if chronographed velocity is below listed velocity that pressure is also lower?
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Does it follow then that if chronographed velocity is below listed velocity that pressure is also lower?
NO which is why the answer is sometimes.
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Gunnery, gunnery, gunnery.
Hit the target, all else is twaddle!
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THis is great info. I appreciate it very much.
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