**WARNING** for those tweaking their loads!

[AP2020]

Ok fellas,

I did an Excel spreadsheet several years ago when I first started using Quickloads. As an Electrical Engineer, I plan on purchasing a strain gauge and pressure monitoring system to compile REAL WORLD PRESSURES.

But, until then, I will rely on Quickloads' Theoretical Data.


Okay, so here's the typical scenario. You get a new rifle and you are starting load development. So you start low, increment powder charges by say, 0.2 or 0.3 grains.

Load up 3 or 4 rounds per powder charge increment. Shoot for groups, see where your NODES are, etc..etc.


So, let's say that you find a NODE and the charge is near you theoretical maximum pressure, or even say 2,000 psi less.


Now, I have been reading and hearing guys say, your next step is to VARY YOUR BULLET SEATING DEPTHS. Here is where things can get sticky, literally [sticky bolt] and figuratively.



Back to my Excel spreadsheet, I cannot find it now, but I will do a "quickie" Quickload right now for you.


My next build is a 22-250AI, 75 gr. Hornady VMAX, H4831SC Powder.


QL is showing I can hit NODE 3 at 1.191 msec. with the following load

28" Barrel
42.1 gr. H4831SC
75 gr. Hornady VMAX
3,395 fps
2.700" COL
57,101 psi

57,986 psi MAX Pressure


So, let's say this happens to be my true magical load.


Now, let's see what happens when I start varying the seating depth.

Going 0.020" less in COL to 2.680"

57,707 psi

Going 0.040" less in COL to 2.660"

58,328 psi

57,986 psi MAX Pressure

or 342 psi OVER MAX Pressure


When I did the spreadsheet, seating depth versus chamber pressure was a linear function

Increasing the seating depth by 0.010" equated to 306.75 psi pressure increase.


Food for thought.

 

[fredhorace77]

nice info. not trying to rain on your parade of findings but this is or should be common knowledge for a reloader or should i say a somewhat experienced reloader. thats why i have always stressed for beginner reloaders to purchase a chronograph before any other item when they are considering " getting into reloading".

 

[Acme7]

As an inexperienced re loader, how would a chronograph relate to pressure? How would i know there is a problem other than the obvious signs? Thanks Jeff

 

[Terry]

I was taught a long time ago to do my load testing with the bullets jammed so that any change in seating depth would result in a drop in pressure. Once I found my max for that rifle. I could safely load below it.

 

[CatShooter]

As an inexperienced re loader, how would a chronograph relate to pressure? How would i know there is a problem other than the obvious signs? Thanks Jeff

It does not... start low, and work up, while looking for the usual suspects.

Chrono's do not reveal pressure.

 

[broncman]

I was taught a long time ago to do my load testing with the bullets jammed so that any change in seating depth would result in a drop in pressure. Once I found my max for that rifle. I could safely load below it.

This IS NOT necessarily true! Jammed would be max length or longest seating depth. To DECREASE seating depth DECREASES case volume and this CAN INCREASE pressure as well.

 

[fredhorace77]

A chronograph is a very important tool needed when working "up" loads. notice the word "up" when starting at the low end and looking for your maximum, velocity will give you another means of determining how close you are to max. ie one is shooting a .243 with a 55gr. bullet. lets say according to your loading manual and all the homework you've done, says you should be around 4050fps. lets say the fastest speed listed in your manual states 4075 fps. you go to the range and start loading and shooting. next thing you know youve reached 4050 fps and absolutely no major pressure signs and your still 1.0gr. away from the max load listed. you tell yourself maybe 0.5gr. more might get me a better accuracy. you load up 0.5gr. more and the velocity jumps to 4095 fps..you best back down cause youve pushed the limits. sometimes reading pressure signs off of the case only,,, can be deceiving ...esp if your shooting ackley improved carts.

 

[CatShooter]

A chronograph is a very important tool needed when working "up" loads. notice the word "up" when starting at the low end and looking for your maximum, velocity will give you another means of determining how close you are to max. ie one is shooting a .243 with a 55gr. bullet. lets say according to your loading manual and all the homework you've done, says you should be around 4050fps. lets say the fastest speed listed in your manual states 4075 fps. you go to the range and start loading and shooting. next thing you know youve reached 4050 fps and absolutely no major pressure signs and your still 1.0gr. away from the max load listed. you tell yourself maybe 0.5gr. more might get me a better accuracy. you load up 0.5gr. more and the velocity jumps to 4095 fps..you best back down cause youve pushed the limits. sometimes reading pressure signs off of the case only,,, can be deceiving ...esp if your shooting ackley improved carts.

Except that if you have 4 or 5 manuals, then they tell you 4 or 5 different velocities for the same amount of powder, so which do you believe??...

... and in the end, your rifle will determine the max load, regardless of the velocity. You can have a tight or loose throat, long leade... and all of these will cahnge the pressure and velocity for the same amount of powder.

I run loads over chronographs twice a month, and I would never consider velocity as a max load or pressure indicator... never!!... because I have never seen any consistency between the two.



.

 

[trailrider121]

I was taught a long time ago to do my load testing with the bullets jammed so that any change in seating depth would result in a drop in pressure. Once I found my max for that rifle. I could safely load below it.

This IS NOT necessarily true! Jammed would be max length or longest seating depth. To DECREASE seating depth DECREASES case volume and this CAN INCREASE pressure as well.

I agree with Broncman.

 

[BoydAllen]

My pressure indicator is bolt lift, and I get to that point in careful, small steps. If I were to gain in pressure with a small change in seating depth I would immediately note the problem, after one shot, and adjust my powder charge. I generally shoot short bullets, and have never run into the situation that was described, BUT the next time that I have the opportunity I will do some experimenting. While one cannot use velocity as a gauge for pressure when changing components, if the bullet primer powder and rifle are held constant, I think that it can generally be said that there is a correlation.

 

[racesnake]

Been reloading for about 50yrs and have shot a lot of stuff down the pipe. The best pressure indicator I've found is primer read. Start out with a reasonable load and work up in small increments keeping an eye on the primers. Look for flattening and cratering. Once I see a slight crater and if I feel I need to go higher I start miking cases, before and after at the web, looking for an increase in diameter. When you detect a diameter increase you have gone too far! BACK OFF! This method has served me well over the years. The above is predicated on using the same primer throughout the test.

 

[Hombre0321]

Just Listen to this guy ^^^...seems to be God's gift to reloading....

A fine example why some people in life never become any more than what they already are today...There are some people out there that you just can't teach anything to them...If they haven't ever seen it or if they didn't think of it..then its wrong.... : : :

Didn't realize we had you as our assigned Teacher, Hummmmmm

A chronograph is a fine tool for some purposes. I use mine so that I have an accurate Velocity reading for my come ups, and in load work-up to a small degree. I could actually care less what velocity numbers I have, it's the results on paper that count

I have looked and looked on that critter ( my chronograph) today ever since I read this post, danged if I can find a single place to attach a pressure gauge. Maybe mine is a defect or something I'll give Oehler a call tomorrow and have them ship me one real quick before I blow something up.

Who would have thought that, I have only been reloading for 50 years or so, must have been just pure luck that I didn't over pressure something all those years I loaded without a Chronograph. Wheeeew man o man it must be my lucky day, maybe I should check those numbers on that lottery ticket just ONE MORE TIME.

The last thing I would like to add is " Bad Catshooter, Bad Catshooter. You are not supposed to argue with the Teacher Man. Just shows you don't have no lernen...

Roland

Roland

 

[BoydAllen]

One little note about pressure signs and the AI cartridges. In my experience they do not show pressure signs like more conventionally designed cartridges do. Some years back, a friend who was a real " if he can get that velocity, so can I" chronograph idiot, had a couple of custom varmint rifles (slow twist), one in .220 Swift AI and the other in .22-250 AI, he had worked up loads based on velocities that he had seen reported i magazines, and although they seemed warm, the primers and other pressure indicators did not look dangerous. Then he ran out of Federal primers, and without dropping back and reworking the load, switched to Winchester primers. The difference in pressure blew the primers out of both rifles. The triggers required repair. Nothing else was hurt, and then he promptly went out and did it again. I advised the gunsmith to refuse to fix the rifles. When I asked my friend why he hadn't dropped the powder charge and reworked the load, he said that he didn't have time. I saw the primers of the Federal loads. If you change anycomponent in a load, drop back and rework. Don't take a chance. another thing, make small moves, and pay attention to the first time you fire the new loads. How many fellows do you know that upon seeing something that should have stopped them right there shot a couple more to see if that would repeat? If it doesn't look or feel right, stop and pull bullets.

 

[fredhorace77]

i never once said that a chronograpgh is to be relied upon soley. if you take a given starting powder charge and watch the velocity as it rises as you increase powder and document the progress and all the other pressure indicators, you will notice the velocity peak then start to fall off again. once this peak is reached any further powder added just becomes dangerous. id have to go back thru several hundreds of issues to find the article written in Percision Shooting magazine to find the lengthy study done on this topic. im sorry but i cant remember what issue it was featured in.

 

[Hombre0321]

Damn there is a bunch of folks up late tonight. Don't know but I would just bet that all three of "US" are about six years older than dirt, Young folks when they stay up late have much better things on there minds than some web-sits, I keep saying it youth is wasted on the young.

Fred, I am poking a little fun at your comment but it was meant not to hurt and make little of your opinions. I simply disagree that a Chrony is as an important part of a reloading system as you do. That's cool a difference of opinion, that's a good thing...

Roland

 

[CatShooter]

i never once said that a chronograpgh is to be relied upon soley. if you take a given starting powder charge and watch the velocity as it rises as you increase powder and document the progress and all the other pressure indicators, you will notice the velocity peak then start to fall off again. once this peak is reached any further powder added just becomes dangerous. id have to go back thru several hundreds of issues to find the article written in Percision Shooting magazine to find the lengthy study done on this topic. im sorry but i cant remember what issue it was featured in.

I have never noticed that.... when I add more powder, I keep getting faster bullets - even when the bolt handle gets hard to open.

 

[Milo 2.0]

i never once said that a chronograpgh is to be relied upon soley. if you take a given starting powder charge and watch the velocity as it rises as you increase powder and document the progress and all the other pressure indicators, you will notice the velocity peak then start to fall off again. once this peak is reached any further powder added just becomes dangerous. id have to go back thru several hundreds of issues to find the article written in Percision Shooting magazine to find the lengthy study done on this topic. im sorry but i cant remember what issue it was featured in.

I have never noticed that.... when I add more powder, I keep getting faster bullets - even when the bolt handle gets hard to open.

I'm with Fred on this. I never develop a load without chrono. Way more times than not I've seen the velocities quit gaining with increased powder, and in some instances decline. Long before a stiff bolt, or any other of the noticeable pressure signs.

This is a gun forum, anyone who follows one persons advice is well........ Let someone use his advice if they may, separating the good from the not so good will teach a person more efficiently.

 

[broncman]

Primers are not a reliable pressure indicator!

I know we have been told that for years, but with the different cup thickness, it just aint so...unless you are using a thinner cup primer. Then it is the weak link. I can get ejector marks before my Tula primers show signs....at all!

It is best to look at the three signs as a whole and not overlook one .
As Boyd stated earlier, a primer change can make things another animal!

Primers, ejector marks, case head web diameter....

 

[AP2020]

So far this looks to be one of the Pressure Systems available:


http://www.shootingsoftware.com/pressure.htm

http://www.shootingsoftware.com/ftp/Instrumenting%20your%20rifle.pdf

If your handloads are “too hot”, it is unlikely that you’ll immediately scatter parts of your
rifle across the range. Your rifle will just age far faster than it would with a more
conservative load. My theory is that it’s best to shoot loads that are a little conservative.
If your gun won’t deliver the speed and power that you want, it’s better to get a bigger
gun than to prematurely age the one you have.
Conclusions:
1. The strain gauge system offers the careful user a highly repeatable measurement
system for developing loads, without disfiguring your firearms.
2. The absolute accuracy of the system is probably pretty good, but nobody can say
how good. In that case, it is wise to use it as though it gave only relative answers.
3. Installation is a breeze. The hardest part is waiting for the adhesive to cure. Even
the “crazy glue” requires a day.
4. Results from the system are indicative of pressure in your own rifle, not a
minimum dimension lab barrel.
5. Simple linear regression, or the LINEST function in Excel, or even just manually
fitting a line to your data, will give you a useful estimate of how much pressure
increases for each added grain of powder. That makes load work-up very easy.
With 6-10 rounds, I usually know how much powder is safe, and how the load
performs over a range of safe values.
6. The system is attractive to handloaders who want their gun to last. The strain
gauge gives you a pressure indicator that is informative over the full range of
pressures your rifle will “see”. You don’t have to exceed your gun’s limit, and
then back down in order to test a load, and you don’t have to rely on pressure
signs that may not appear until you’re far past a prudent limit.
7. The price of a complete system is about on par with a moderately priced scope,
and, once you have the basic system, adding more strain gauges isn’t a budget
buster.

 

[AP2020]

OR

I have worked with National Instruments years ago for a customer who made Clutches [LUK]:

also a viable option, just need to get some pricing


http://www.ni.com/compactdaq/whatis/


well, cost for this system is way too prohibitive!