Chrony's - What true purpose do they serve?

GrBear

GrBear

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So I'm trying to figure out what the true purpose of a chrony is, and how it fits in to a reloader's arsenal.

I know that a chrony provides the shooter with a FPS reading of their load, and the fancier ones provide historical tracking, drop tables, etc. That's all great data to have.

My question is though, how does that information truely help a reloader? Say you found the sweet spot load for your rifle, you now have all the information of that load.. bullet, bullet weight, powder, powder charge, fps, drop tables, etc.

How does that information help if you want to find out if your going faster than your bullet should go, or slower. What if you want to try another powder, is the information from the previous load an asset or useless?

Sorry for the n00b questions, I'm just trying to wrap my mind around what all this information gathered from a chrony is beneficial for.

Thanks!
 
It can show you consistancy of a load.
It can reveal how annemic some factory loads can be at times :rolleyes:
Since most hunters are looking for close to max load it gives you another avenue beside pressure to indicate how your doing with load development. Some load manuals are not terribly accurate as to velocity claimed for a specific load, accuracy is great but if your 400fps low in vel it can seriously affect bullet drop on any game animal that may present itself at a distance.

I'm sure some will pop in with more but it's early yet!
 
I lived peacefully without a chrony for several years. For my 30-06 I developped loads for 110, 150, 180, 190 and 220 bullets, all this without any fps measuring. But when it came to develop a reduced load, I had to buy one - just to estimate how far was it reduced.
 
Since handloading began, folks have had to rely on warning signs from their brass to tell them when they were getting into dangerous pressure territory. With a chronograph this is no longer the case. There are two ways in which a chronograph can be used to judge pressure:

The simple way is to work up your loads in regular increments until you reach the maximum velocity listed in the loading manual. Regardless of what the load is, when you hit that velocity, STOP! The maximum pressure has been reached.

The second way to determine your maximum pressure is to record the velocity as you increase the powder charge by regular increments. It doesn't matter if you increase by 1 gr or a half grain, but the size of each increment should be based on the case volume of your cartridge. Most rifle cartridges can increase by a full grain, but a pistol cartridge (9mm, .45 auto etc) should increase by a half grain. Each increment must be the same as the increment before, and it is better if you can start several grains below maximum so you can watch the trend. You will observe that the velocity begins to rise in a consistent fashion. At some point you will observe a velocity plateau, where the velocity increase is suddenly half or less of the previous increase. This velocity plateau indicates you have reached the maximum pressure. I often reduce my working load a half gr below this point. If you continue to increase the powder charge after the velocity plateau has been reached you will experience a sticky bolt within the next increase or two.

Another benefit of the chronograph is to measure the consistency of your handloads. The tighter the velocity spread, the greater the accuracy potential of your loads.

If you can measure the velocity at the muzzle and the velocity of the bullet at the target, you can develop a better idea of the long range trajectory of your load than you could from using the advertised BC of the bullet.
 
Chronographing loads can tell you something about the consistency of your loads as others say. The one situation where I think this data might be important is when I am going to shoot long range and only have grouping data for 100 meters. I think variation in velocity and choosing the most consistent load becomes more important as one shoots farther and farther out. Besides, I bought one of the gd things and it grieves me to not use something I have paid for...:D
 
What purpose? They are fun!

If everything required a "purpose" we would still be driving 4 HP carriages, airplanes would still be doing 25 MPH, we would all be computing on Commadore 64's, and we would still be loading all our rifles from the muzzle with black powder, wad and ball...

I use mine to do just what they were intended to do ... measure the "muzzle" (for me it is 15' from the muzzle) velocity.
 
Boomer said:
At some point you will observe a velocity plateau, where the velocity increase is suddenly half or less of the previous increase. This velocity plateau indicates you have reached the maximum pressure. I often reduce my working load a half gr below this point. If you continue to increase the powder charge after the velocity plateau has been reached you will experience a sticky bolt within the next increase or two.

Another benefit of the chronograph is to measure the consistency of your handloads. The tighter the velocity spread, the greater the accuracy potential of your loads.
Click to expand...

This is exactly what I was looking for, that missing piece of information.. a sort of what does it all mean.

You hear people talk about their load's FPS, and how they chrony'd it.. but I've never heard anyone talk about why specifically they did.

So lets take this a bit further..

- We know that a chrony provides FPS, and from that we can tell when we've it maximum pressure.
- We can also tell at what FPS our choice of bullet performs best in that specific barrel
- We can calculate drop rates based on BC, weight and FPS.

My question is, what information from this can we carry over to working up another load on the same barrel with say a different powder.. or are we really starting over from scratch?

Just as a side note, I'm not against chrony's.. infact I just recently bought a Pact Pro model but havent had a chance to use it yet.
 
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What use is a chroney....?

Well.... It's something else besides targets to put bullet holes through



Twice :redface:
 
GrBear said:
This is exactly what I was looking for, that missing piece of information.. a sort of what does it all mean.

.
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I fear the information you are so glad to see is false. The maximum pressure and the corresponding load is in you reload manual and that is the only reliable source. Last Sunday I was developping loads for 190Hon bullet with IMR4350. I've got TWO plateaus when rising from 50.8 to 51.0 and from 53.0 to 53.2 - in both cases bullet speed REDUCED (5 shots statistics for each case). And both loads were far away from the maximum - according to Hodgdon reloading center it's 54.5.
 
I like a chronograph for the following reasons:a) check SD and see how it equates with group size.
b) see what my loads and factory control loads are really putting out.
c)to help calculate bullet drop at long range.
d) vel. is critical to findings when loading in the "subsonic zone"
 
mihasic said:
I fear the information you are so glad to see is false.
Click to expand...

Dooh!

In all honesty, my trust in reloading books is kinda on the low side.. I've got 3 different reloading manuals.. and I can pick one type/weight bullet, one specific powder, and get a different max load that can vary by as much as 3-4 grains of powder in each book. Hell, I had one load for my .243 that one book's max load was one of the other book's starting load.

Who the hell do you believe anymore?
 
GrBear said:
Dooh!

In all honesty, my trust in reloading books is kinda on the low side.. I've got 3 different reloading manuals.. and I can pick one type/weight bullet, one specific powder, and get a different max load that can vary by as much as 3-4 grains of powder in each book. Hell, I had one load for my .243 that one book's max load was one of the other book's starting load.

Who the hell do you believe anymore?
Click to expand...

I agree that there are many contradictions between different books. Unfortunately, that's all we've got. My belief is if ANY book cites some load as safe, it is safe - otherwise the company could have BIG problems in the US.
 
GrBear said:
Who the hell do you believe anymore?
Click to expand...

You believe your rifle and your chronograph...

Loading is a learning process. One of the reasons you don't START at max powder charge.:)


A safe handloader picks a minimum powder charge form a manual, then gradually works up to get the speed and accuracy he wants, keeping an eye out for obvious pressure signs, such as sticky bolt or a chronograph reading out of the world for what you are doing.

Once you get to the maximum of a manual, it's up to you how to proceed. Luckily, most manuals today are pretty good guidelines.

As for extrapolating one load to another- You can only compare speed and accuracy when you have changed powder. There may be othe rrelationships (such as similar burning powders should perform similarly) but they aren't absolutes.:)
 
mihasic said:
I agree that there are many contradictions between different books. Unfortunately, that's all we've got. My belief is if ANY book cites some load as safe, it is safe - otherwise the company could have BIG problems in the US.
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I don't know about that.

For instance - I tried some 180 grain 308 Winchester loads using Win 760 powder. I hit book max velocity and primers that were starting to get about as flat as I feel comfortable with - 7 grains BELOW what the book said I should. Furthermore, I was loading 7 grains below book max, because it would be impossible to fit the amount of powder listed as the max 308 load in any of the 308 case's I have available to me (all the major brass makers); in fact, at 7 grains under book max I had 100% fill density.

I say that it pays to use your head and never blindly trust the book.
 
What I end up doing as far as loads go, is take the absolutely lowest load listed in all three of my books, and build 10 rnds of each load in 0.2 gr increments so I can shoot 2 5 rnd groups of each charge. Once there I make 0.1gr increment loads (+/-0.3 gr from the best grouping shots) and see if I can fine tune it. Obviously I watch for pressure signs as I increase load charges.

I bought the chrony to see what was happening with each load and try to make a correlation in my mind as to why that load was more accurate.

I thought I read somewhere that there's a correlation to barrel length, rate of twist, BC and FPS that determined best accuracy, but I can't find that information anymore.. or even if it was just someone proclaiming to be an expert. It's alot of variables, but hopefully it means building a accurate load more quickly when switching powders and bullet type/weights.
 
mihasic said:
I fear the information you are so glad to see is false. The maximum pressure and the corresponding load is in you reload manual and that is the only reliable source. Last Sunday I was developping loads for 190Hon bullet with IMR4350. I've got TWO plateaus when rising from 50.8 to 51.0 and from 53.0 to 53.2 - in both cases bullet speed REDUCED (5 shots statistics for each case). And both loads were far away from the maximum - according to Hodgdon reloading center it's 54.5.
Click to expand...

As I explained, you increase the powder charge a full grain per round for rifle cartridges. The plateau you observed by increasing a quarter of a grain could of been caused by the difference in case capacity of each cartridge. Done properly, using a velocity plateau as a means of determining the maximum load is safe and repeatable. If it wasn't I wouldn't use it, and I've used it in both handgun and and a broad range of rifle cartridges for quite some time.
 
GrBear said:
This is exactly what I was looking for, that missing piece of information.. a sort of what does it all mean.

You hear people talk about their load's FPS, and how they chrony'd it.. but I've never heard anyone talk about why specifically they did.

So lets take this a bit further..

- We know that a chrony provides FPS, and from that we can tell when we've it maximum pressure.
- We can also tell at what FPS our choice of bullet performs best in that specific barrel
- We can calculate drop rates based on BC, weight and FPS.

My question is, what information from this can we carry over to working up another load on the same barrel with say a different powder.. or are we really starting over from scratch?

Just as a side note, I'm not against chrony's.. infact I just recently bought a Pact Pro model but havent had a chance to use it yet.
Click to expand...

The data you collect from one group of components is only pertinent for those components. I'm not adverse to changing primers or bullet styles within a specific bullet weight without working the load up again, but I don't make any assumptions beyond that. Work up the maximum load for your group of components, then once that maximum load is determined, tweak it down wards to determine the best accuracy.
 
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