Odd Velocity Variance

AllenOne1

Major Hide Member
Full Member
Minuteman
Mar 8, 2020
1,876
3,139
Middle Tennessee
I have a new 6.5 barrel, 300 plus rounds on it now. The velocity follows an odd pattern that I've not seen before. The first shot is very slow due to a cleaned and oiled barrel, this is expected. The next shot velocity is 40 fps faster than the expected average velocity, speed then begins to slowly walk down until it gets into a "normal" range. Takes about 10 rounds to stabilize and even then I'm getting higher ES than I would like to see.

Brass is annealed after each firing (AMP), chamfered & deburred, neck brushed, sized, mandrel, powder (Autotrickler), bullet seated. Case sizing and bullet BTO are very consistent.

Anyone seen this before?

I'm going to stop oiling the bore after cleaning and see if that makes any difference but I've done that for several years. Not sure what else to look at.
 
Sometimes there is a quick fix and sometimes this takes time to sort out. Keep an eye on the velocity and note how it responds to the shot count and cleaning over several sessions.

If you have a borescope, check the condition and type of fouling. Since you are troubleshooting, you will want to do a normal cleaning and at some point go nuclear if necessary, and that requires a borescope.

Keep in mind you may have several issues in play all at the same time or combining in the duration of the cleaning cycle.

Some velocity issues can also come from reloading issues, ignition issues, as well as fouling, but you have to keep an open mind and watch for all of them till you know for certain which ones are to blame.
 
No, I wouldn't call it cleaning to bare metal. Chemical cleaners and nylon brushes. There is always color along with a little carbon and copper that doesn't come out. No abrasives on this barrel at this point.
Your experience doesn’t seem to indicate a carbon ring. I would take the rifle home after a range visit and not touch the bore or chamber. Go shoot it another day while tracking the velocity of each shot to see if the pattern is still there.
 
  • Like
Reactions: R_A_W
Your experience doesn’t seem to indicate a carbon ring. I would take the rifle home after a range visit and not touch the bore or chamber. Go shoot it another day while tracking the velocity of each shot to see if the pattern is still there.
That's a good idea. I normally clean after every shooting session so 30-50 shots then clean. Carbon ring doesn't seem to exist so don't think that is coming into play.

This barrel shoots small so am not ready to go nuclear as a fix at this point. I'll be double checking each step of my reloading process this week just to be sure nothing is flakey there as well.
 
I concur with the suggestion to NOT clean after the next trip. And I NEVER use oil in a cleaned bore unless I'm removing the barrel from the action for storage. After cleaning, my rifles usually take 3 rounds to "settle."

I primarily use Bore Tech C4 for cleaning; according to Bore Tech a final wet patch will leave a protective coating that lasts a couple of weeks. Fwiw, I clean my centerfire rifles about every 200 rounds. Any one of them may sit uncleaned in the safe for weeks; I've never had an issue with corrosion on any part of any firearm (the safe is in an air-conditioned part of the house).
 
Last edited:
Occasionally too much information is a bad thing. I can’t decide if getting a chronograph was best thing I’ve ever done or the dumbest.
Brux, Kreiger, Brian Lutz, and Speedy Gonzales all have very different philosophies about when and how to “clean” a barrel. I am not sponsored nor do I have a large bank account so barrel longevity is important to me. I clean only when the rifle performance is unacceptable. I will occasionally run an oil soaked patch and a few dry patches after a range session. The nicer and gentler (bore guide and chemicals) I can be with the barrel the longer it will last (in theory). Shooting 20-100 rounds, cleaning to remove all of the copper, then fouling the barrel by shooting xx(x) rounds to get acceptable results isn’t acceptable to me.
 
I clean only when the rifle performance is unacceptable.
Agree.
The main takeaway for the beginners... is how do it know?!?

I am waiting for some visitors to get ready to roll, so I will kill a few words for the sake of the beginners.

TLDR: Rookies must shoot well enough and long enough to learn when and how to clean. Using an "inexpensive" varmint/target rifle in something like 223 is a good and affordable way to learn.

At some point in life, a rookie needs to make a decision about how much resource they will burn shooting and what their goals will be for that shooting.

Lets face facts, most of you are not trust fund babies, and have day jobs, a wife, kids, family, households, vehicles, homes to maintain, taxes to pay, etc... and only so many hobbies and opportunities. It is different for everyone, but similar in many ways too.

There is nothing wrong with starting with airgun and/or rimfire in your shooting journey.

Anything that helps with fundamentals and trigger time that is inexpensive and doesn't take too much time is a good thing. But at some point, these don't teach us everything that centerfire does, and it doesn't teach you about centerfire cleaning intervals.

Even folks who don't or can't reload, may want to get to their goals but might not have a good mentor or club nearby.

Don't let that stop you, but don't fall for the internet hype and try to reach the stars before you learn to crawl.

Try to balance between having fun and staying organized. If you skip one or the other, you will likely quit.

That means keeping yourself honest with a journal and shooting a standard recorded target often.

Parts of shooting can be a lot of fun, but let's face it, taking notes is one thing, and cleaning is yet another. Nobody I know likes cleaning rifles.

Nothing wrong with getting started with factory ammo in a medium or higher energy cartridge like a 6.5 CM, but I am taking up space for a moment for the sake of those who are trying to learn this on their own.

Nothing wrong with getting a higher energy gun, but don't skip the fundamentals because it will just take you longer and cost more to get up the learning curve, especially if you are on your own.

To develop a rifleman in a MIL/LEO world, we expect to burn at least 5000 to 10000 rounds to get them to proficiency level. Sure there have been prodigies that ramp up quick, but most kids will fall in the middle of that range to call them proficient.

In that world, there is an organization with resources and mentoring behind their training. Most of the program is out of their hands and the homework has been done for them. They shoot what we tell them, when we tell them, so they clean when we tell them to start out. Later on, we let them explore the boundaries and challenge the concepts on their own.... however they can shoot by then.

But what about you, who doesn't have that and just want to get shooting? How do you know when and how to clean?

As you get rolling in life and want to run a higher performance cartridge, don't forget to start with those fundamentals and find room in your life for a decent heavy bbl 223 and plan to shoot it a lot. Even folks who have family backgrounds or lots of resources and friends can benefit from running more trigger time with a good training centerfire rifle that gives honest feedback for a fraction of the cost of shooting bigger guns.

You can start with something like a factory Sendero, Savage, or inexpensive varmint or target rig. You just need to have a decent rig/ammo so that you can even tell when fouling is an issue.

Be patient if you are on your own. It takes a while to shoot well enough to establish a baseline, and that is the only way detect that you went past the shot count and need cleaning. At some point you need to allow yourself to shoot into this performance drop-off more than a few times to be able to understand your cleaning interval.

You need a journal and record of your DOPE. You will benefit from a borescope and chronograph, but you can certainly postpone those and get started with just a journal.

Even loaded with the cheapest target rounds and shooting rapid strings, this barrel will run at least 2500 rounds or more before it starts to fail you during rapid strings and eventually won't group in slow fire. To know for certain you are either fouled or eventually worn out, you test a rapid string and you will see the group open up or the zero shift, or both.

I am recommending this type of pattern so that you can run for 15 to 20 shots without taking a break. You will be able to focus on driving the gun and reading the wind, then take your break and let the gun cool off.

A 223 heavy bbl rig can handle that, a skinny higher energy gun cannot. Shooting enough rounds to become proficient in 223 can be done for a fraction of what it costs to shoot the bigger guns.

Plan to burn through about two or more of these bbls on average before you think you know anything about shooting, wind reading, reloading, cleaning, etc..

Any decent inexpensive varmint or target 223 can be the platform for learning how much and when to clean, and what you can or cannot get away with. You can blast, plink and have fun with this, but always keep a journal and include standard targets at intervals that will tell you when/if performance falls off.

Shoot this year round in different conditions and especially when conditions are "bad". This will keep you honest and teach you without breaking your fun money account.

A 223 that throws 69 to 77 grain bullets uses about 24 grains of powder per shot. When you shoot the higher energy cartridges, you will be burning much more powder and throwing more bullet per shot, and the cleaning interval may look a little different as a result.

The benefit of using that 223 so much, is that you will have learned that powder and copper fouling act different for different bullets and powders, as well as how a higher quality barrel responds. Starting with a inexpensive factory hammer forged barrel, and then replacing it with a high quality cut-rifle barrel, will make you appreciate those differences.

This pattern of rifle and shooting will teach you about more than cleaning intervals, and it will keep you honest without breaking the bank. Good Luck , YMMV