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Tracking Velocity Changes in a New Barrel

jaychris- You have an excellent chart showing how that the velocity increased during your first couple hundred rounds. This is very good information and it shows good diligence on your part for tracking such information.

It has been well documented by many that "somewhere" in the first couple hundred rounds of a new stainless barrel's life it will change. Thus one must be ready to change bullets, primers, powders, etc in order to keep it within your desired accuracy limits. And to stay vigilant and ready to change loads to keep the rifle shooting at it's (and the shooter's) best.

Having been at this a while now, I've noticed on a lot of new barrels that there will be a "rough" spot or a section of the barrel that is not as smooth as the rest of the barrel. After shooting it a while then running a borescope down through it all of a sudden that rough spot or hook on the lands is now smooth and the rifle is shooting at higher FPS or lower ES than it did the first 50 or so rounds. These rough spots and "bad" spots in the barrel many times can be felt when cleaning if you don't have a borescope to see them.

Again, hats off to ya for your diligence in this. That is very good information for newcomers to the sport too. WD
 
WyleWD said:
queen_stick said:
Jay,

There has to be a pressure increase to jump velocity up that much... is it caused by 'build up' in the bore (carbon, copper, etc..)? I'm thinking that something is causing a restriction on the bullet passing through the bore, causing the pressure increase. If that's what's happening (and I could be very wrong here) then I would think you would run into overcharge issues LATER in the barrel's life, not in the beginning.
Walt

If this is true, it contradicts what I was told by a barrel maker & a trustworthy gunsmith regarding custom made stainless barrels. Was told that as the rifle was shot it would "smooth out" the small imperfections, rough spots, etc in the barrel from the rifling & drilling processes and speed would increase and there might be some DROP or leveling out in the pressure curve. Thus a reduced load used in break in may be able to be bumped up or a change in powder burn rate after break in.

I know it is debateable without data, but.... there is merit to either side of the debate IMHO. WD
I am leaning toward what WyleWD has posted. From my past experience. plus what my records show and from what 3 top Fclass shooters have told me and one Awesome gunsmith has told me as well. I guess I'm saying 2+2=4 so all adds up to this. Don't hold me too this but I'm very intrested in just finding out for myself and if I can I will share my results.

I think this thread has turn the light bulb on to what my gunsmith was trying to tell me in the beginning. My gunsmith has a Cam adapter for the Hawkeye bore scope. This magnifies things and you can see the microscopic flaws in a barrel and when you see this on a LCD screen it really shows up. I will admit I was a little worried from what I was seeing in a barrel that had not had a single round fired. Believe me this barrel and rifle is simply just a hammering machine. My barrel shot a 1/4" group at 200yds at 38rnds. I stopped and loaded up for a practice match my club was having. Upon reaching 168rnds This barrel went crazy on me! I was using plot sheets and could see just where things happen. As I got stressed in the moment things just got worse so I quit and came back home. Shot some of the same ammo that was left over from the match. Groups at 200 were now at 1"+. Velocities were 75fps faster than from the start. I'm starting to believe now that at this point those microscopic flaws are smoothing out and even tho it's a handlapped custom barrel one still has to test every 300 or so rounds and stay on top of your load as the barrel changes conditions thoughout the life of the barrel. I have made notes and filed those notes with my records for this rifle and barrel. I'm hoping I can stay on top of this and scope the barrel thoughout the life of it with the cam that my smith has. My Hawkeye just will not show what the Cam on the Hawkeye will. I'll ask even if my gunsmith is busy if I can bring my rifle to the shop and scope it myself. I'd just like to see how things do change and if nothing else gain some knowledge for future reference. Like I said don't hold me to it but if I can I will try to keep track of this and I'll post my results. I'm not as good with graphs as JAY is but I will try!

Very intersting Thread!!! Thanks for bringing this up Jay!! Great Topic!!
 
Dang it, I used to have a nice RSI Pressure Trace II system that could probably have answered the question about relative change in pressure. I've only been tracking velocity, but I guess I'm curious now as to what the pressure is doing. Although the Dasher is so dang short it would be tough to instrument it.

I will say though that my direct experience has been that pressure is increasing along with velocity. On my first barrel, before I was aware of this increase-in-velocity phenomenon, I built up my load in early development to what looked like a safe load. No overt pressure signs and velocities was where I thought it should be, right around 3050fps. I had built up to this fairly slowly, but like I said, no pressure signs. I developed the load over a chrono and then shot it a few times in practice without using the chrono. I saw a few flattened primers here and there (velocity/pressure increasing), but I wasn't too concerned.

Then I started blowing primers. Like, a ridiculous # of primers. Shot after shot. And yes, I was new enough (and dumb enough) to keep shooting cause I wasn't sure what was going on. Luckily I'm shooting a Barnard which could take that kind of abuse, but I seriously DO NOT RECOMMEND that course of action to others. Me being stupid gives others the chance to avoid it. You start blowing primers, you've got a serious issue to deal with. Granted, at that point, my brass had been pretty stressed from the load I was putting on it. I ended up dumping nearly 80 pieces of brass with shot out primer pockets. After only 4 firings.

I took that load back to the range with a chrono and holy crap! I was well over 3100fps. All other variables were the same- it was the same load I'd been shooting for the past 100 rounds. But it had jumped from 3050fps to 3150fps. From slight (non-troubling) pressure signs, to serious pressure signs. That's when I started wondering about my barrel and started tracking my new barrels from shot 0 and shooting every practice round over a chrono.

So, while what WyleWD is saying makes sense conceptually, I have personally witnessed that pressure *does* increase over those first 150 shots or so of a barrel's life, along with the velocity. It would be cool to have actual measurements to back that up though.

deadlyswift said:
WyleWD said:
queen_stick said:
Jay,

There has to be a pressure increase to jump velocity up that much... is it caused by 'build up' in the bore (carbon, copper, etc..)? I'm thinking that something is causing a restriction on the bullet passing through the bore, causing the pressure increase. If that's what's happening (and I could be very wrong here) then I would think you would run into overcharge issues LATER in the barrel's life, not in the beginning.
Walt

If this is true, it contradicts what I was told by a barrel maker & a trustworthy gunsmith regarding custom made stainless barrels. Was told that as the rifle was shot it would "smooth out" the small imperfections, rough spots, etc in the barrel from the rifling & drilling processes and speed would increase and there might be some DROP or leveling out in the pressure curve. Thus a reduced load used in break in may be able to be bumped up or a change in powder burn rate after break in.

I know it is debateable without data, but.... there is merit to either side of the debate IMHO. WD
I am leaning toward what WyleWD has posted. From my past experience. plus what my records show and from what 3 top Fclass shooters have told me and one Awesome gunsmith has told me as well. I guess I'm saying 2+2=4 so all adds up to this. Don't hold me too this but I'm very intrested in just finding out for myself and if I can I will share my results.

I think this thread has turn the light bulb on to what my gunsmith was trying to tell me in the beginning. My gunsmith has a Cam adapter for the Hawkeye bore scope. This magnifies things and you can see the microscopic flaws in a barrel and when you see this on a LCD screen it really shows up. I will admit I was a little worried from what I was seeing in a barrel that had not had a single round fired. Believe me this barrel and rifle is simply just a hammering machine. My barrel shot a 1/4" group at 200yds at 38rnds. I stopped and loaded up for a practice match my club was having. Upon reaching 168rnds This barrel went crazy on me! I was using plot sheets and could see just where things happen. As I got stressed in the moment things just got worse so I quit and came back home. Shot some of the same ammo that was left over from the match. Groups at 200 were now at 1"+. Velocities were 75fps faster than from the start. I'm starting to believe now that at this point those microscopic flaws are smoothing out and even tho it's a handlapped custom barrel one still has to test every 300 or so rounds and stay on top of your load as the barrel changes conditions thoughout the life of the barrel. I have made notes and filed those notes with my records for this rifle and barrel. I'm hoping I can stay on top of this and scope the barrel thoughout the life of it with the cam that my smith has. My Hawkeye just will not show what the Cam on the Hawkeye will. I'll ask even if my gunsmith is busy if I can bring my rifle to the shop and scope it myself. I'd just like to see how things do change and if nothing else gain some knowledge for future reference. Like I said don't hold me to it but if I can I will try to keep track of this and I'll post my results. I'm not as good with graphs as JAY is but I will try!

Very intersting Thread!!! Thanks for bringing this up Jay!! Great Topic!!
 
Great thread Jay.
Your results mimic what has been observed in the development and building of over 100 Match grade AR 15 rifles broke in and load development performed on an actual Machine rest. All shot over a chronograph to track the speed and accuracy of each barrel with the same load, only changing the bullet depth to fine tune the rifles.
One observation that is not mentioned is that chrome moly barrels seemed to break in much faster than the Stainless barrels no matter the manufacture. All rifles where shot with the same ammo for the life of the barrel so it was intresting to see the Data on round count and how it related to the life of the barrel. I think alot of times a Crome moly barrel is overlooked dispite its ability to provide early stability of what your seeing and about the same life expectancy of the tube vs Stainless barrels. Typicaly we saw a barrel break in or settle down with its increase in velocity at around 50 rounds with a crome moly barrel. And almost everyone of the stainless barrels where right at what your seeing with the 150 to 200 rounds before it leveled out.
It made it easier to do a tune on the rifle with less rounds before it was handed to the shooter with a chrome moly barrel so in the last couple of years that has been the direction we have gone. The problem: the shooter does not take care of the barrel and it gets rust pits. ( Stainless advantage) Enter the Melonite process. Now you have a barrel that is broke in early then nitrided and it last as long as a stanless barrel and can handle the abuse of hot humid weather and rain storms. This last part right now is all theoreticle as We have not wornout a Nitrided barrel yet.
Im going to have to break down and buy a pressure trace system to see how it relates to the increase in bullet speed after ( what I call ) the barrel breaks in.
Again great thread and your experiencing the exact same thing as we have over the course of 100+ barrels.

Shoot good
RussT
 
jaychris said:
Dang it, I used to have a nice RSI Pressure Trace II system that could probably have answered the question about relative change in pressure. I've only been tracking velocity, but I guess I'm curious now as to what the pressure is doing. Although the Dasher is so dang short it would be tough to instrument it.

I will say though that my direct experience has been that pressure is increasing along with velocity. On my first barrel, before I was aware of this increase-in-velocity phenomenon, I built up my load in early development to what looked like a safe load. No overt pressure signs and velocities was where I thought it should be, right around 3050fps. I had built up to this fairly slowly, but like I said, no pressure signs. I developed the load over a chrono and then shot it a few times in practice without using the chrono. I saw a few flattened primers here and there (velocity/pressure increasing), but I wasn't too concerned.

Then I started blowing primers. Like, a ridiculous # of primers. Shot after shot. And yes, I was new enough (and dumb enough) to keep shooting cause I wasn't sure what was going on. Luckily I'm shooting a Barnard which could take that kind of abuse, but I seriously DO NOT RECOMMEND that course of action to others. Me being stupid gives others the chance to avoid it. You start blowing primers, you've got a serious issue to deal with. Granted, at that point, my brass had been pretty stressed from the load I was putting on it. I ended up dumping nearly 80 pieces of brass with shot out primer pockets. After only 4 firings.

I took that load back to the range with a chrono and holy crap! I was well over 3100fps. All other variables were the same- it was the same load I'd been shooting for the past 100 rounds. But it had jumped from 3050fps to 3150fps. From slight (non-troubling) pressure signs, to serious pressure signs. That's when I started wondering about my barrel and started tracking my new barrels from shot 0 and shooting every practice round over a chrono.

So, while what WyleWD is saying makes sense conceptually, I have personally witnessed that pressure *does* increase over those first 150 shots or so of a barrel's life, along with the velocity. It would be cool to have actual measurements to back that up though.

deadlyswift said:
WyleWD said:
queen_stick said:
Jay,

There has to be a pressure increase to jump velocity up that much... is it caused by 'build up' in the bore (carbon, copper, etc..)? I'm thinking that something is causing a restriction on the bullet passing through the bore, causing the pressure increase. If that's what's happening (and I could be very wrong here) then I would think you would run into overcharge issues LATER in the barrel's life, not in the beginning.
Walt

If this is true, it contradicts what I was told by a barrel maker & a trustworthy gunsmith regarding custom made stainless barrels. Was told that as the rifle was shot it would "smooth out" the small imperfections, rough spots, etc in the barrel from the rifling & drilling processes and speed would increase and there might be some DROP or leveling out in the pressure curve. Thus a reduced load used in break in may be able to be bumped up or a change in powder burn rate after break in.

I know it is debateable without data, but.... there is merit to either side of the debate IMHO. WD
I am leaning toward what WyleWD has posted. From my past experience. plus what my records show and from what 3 top Fclass shooters have told me and one Awesome gunsmith has told me as well. I guess I'm saying 2+2=4 so all adds up to this. Don't hold me too this but I'm very intrested in just finding out for myself and if I can I will share my results.

I think this thread has turn the light bulb on to what my gunsmith was trying to tell me in the beginning. My gunsmith has a Cam adapter for the Hawkeye bore scope. This magnifies things and you can see the microscopic flaws in a barrel and when you see this on a LCD screen it really shows up. I will admit I was a little worried from what I was seeing in a barrel that had not had a single round fired. Believe me this barrel and rifle is simply just a hammering machine. My barrel shot a 1/4" group at 200yds at 38rnds. I stopped and loaded up for a practice match my club was having. Upon reaching 168rnds This barrel went crazy on me! I was using plot sheets and could see just where things happen. As I got stressed in the moment things just got worse so I quit and came back home. Shot some of the same ammo that was left over from the match. Groups at 200 were now at 1"+. Velocities were 75fps faster than from the start. I'm starting to believe now that at this point those microscopic flaws are smoothing out and even tho it's a handlapped custom barrel one still has to test every 300 or so rounds and stay on top of your load as the barrel changes conditions thoughout the life of the barrel. I have made notes and filed those notes with my records for this rifle and barrel. I'm hoping I can stay on top of this and scope the barrel thoughout the life of it with the cam that my smith has. My Hawkeye just will not show what the Cam on the Hawkeye will. I'll ask even if my gunsmith is busy if I can bring my rifle to the shop and scope it myself. I'd just like to see how things do change and if nothing else gain some knowledge for future reference. Like I said don't hold me to it but if I can I will try to keep track of this and I'll post my results. I'm not as good with graphs as JAY is but I will try!

Very intersting Thread!!! Thanks for bringing this up Jay!! Great Topic!!

Jay I experienced the same thing in my first 30 cal barrel last year! Again my load was hammering! I put the rifle up and was thinking well I got this one ready to go! Now I will say I did load development with temps in the mid 40s and then during a match with temps in the mid 70s I started kicking primers out! Matter Of fact it was 6 primers during one relay! Returning home again Vel were over 100fps and 3 out of 7 shots kicked primers out so I stopped and started over with powder charge. I ended up dropping .4gr to calm things down and get things shooting again. This is what my notes read as I did jot down in my own words what I was seeing. I was shooting Varget and it's suppose to not be temp Sentive but a 30* jump in temps may be pushing it for any powder! However It could be a combination of all that caused me to actually kick multi primers completely out!

I will add that the experience and leg work that was done with the first 30 cal barrel did raise caution on my 2nd so I haven't seen any pressure signs but a increase in Vel and what I would call a barrel jumping tune seems to be the case at this point with my current barrel.
 
I,m thinking it is all about the gas seal, that the bullet down the bore is the same as a close fitting engine piston without rings, but much much higher pressure.
A new car doesnt have quite as much compression as it will have when it has done 1000 ks or so. The bullet has to seal without the aid of expanding rings, so I,m thinking the increase in velocity and pressure is that it is getting a better seal. Any high spots (or microscopicly wider spots on lands) will get burnished out, with more wear at the chamber end, so the barrel ends up with a very slight taper to the bore to keep it sealing.
 
This is why I always tell new customers to quickly find a load that shoots near 1/2moa and is a grain or two off of max for the bullet/load combo. Load 100 pcs of brass and run that thru before doing serious load work ups.
I normally see the plateau at 70-100 rounds with the cut rifles barrels I use and the shoot clean method I use in the first half dozen rounds. On a couple button barrels it took a few more rounds.

This also has to do with "brake-in" many people claim they do no "brake-in" and that it is a myth. That's all fine and good, Because your barrel will "brake-in" weather you do anything special or not. Doing a shoot and clean procedure just speeds it up a bit. Brake-in relates to the elimination of serious copper fouling and the stabalized velocity readings that we are discussing here.

This discussion really applies to what is happening in the rifles bore, not the throat or lead. I recently cut back and rechambered a 6.5x284 to 260 rem. Losing 4" of barrel with about 800 rounds thru the 6.5x284. Now with 180 rounds thru the 260 shooting the same load, zero velocity change. What happened to the bore occurred when it was a 6.5x284 and rechambering/ new throat had zero effect.

This was an article I wrote a couple years ago about barrel care the discussion that follows the article in the forum is actually worth more than the article as far as explaining what is going on. The article lacked in depth info on the subject because it was more or less written for the neophyte on barrel care.

http://www.longrangehunting.com/articles/rifle-barrel-break-in-1.php

I am still amazed at the number of guys who completely discredit this phenomenon when I tell them about it. Less than a month ago a group of guys traveled from cold to warm to shoot a match with fresh barrels and cold weather load development. In 5 days of shooting, pulling bullets from preloaded ammo, buying out the reloading equipment at the local store, and dropping charges 1.5-2 grains, I hope it finally sunk in.
 
I agree 100% Jim. Ive had quite a few barrels rechambered and they never had any wierd velocity jumps, only the new barrels. Freshly rechambered barrels copper fouled for 10 rounds or so as the throat ran in, but after that was right for 1000 rounds.
I makes me wonder when I read benchresters say they wont take a barrel to a big compretition once if it has more than a few hundred rounds through it. While a lot of good F class shooters say they wont take a barrel to a big comp UNTIL it has a few hundred rounds through it?????
 
Hello, I'm Spanish from Europe. I will tell my experience with an Italian rifle (Sabatti, polygonal barrel) and Swiss gunpowder RS.

The start was book, shooting, cleaning ... etc.

The next transit make a ladder until you find the hard opening and flat pistons. I use to measure indistinctly Magneto or Labradar.

All apparently well ... but I notice, that in the project search sessions of the projectile, there are many inconsistencies. And already with 100 shots, there is discontinuity of speeds with the charges. I shoot up to 200 and it seems I find a node at 880 ms. And I participate in the national. First day of competition everything in order. And I get V Bull's record at 600 yards and a good wind reading at 900. Second day of competition, at 600 yards the V Bull is elusive and the bolt is getting harder and harder. At 900 there is a very vertical behavior.

I do not give more importance to the difficult wind of the field or the stress of the competition. After the summer and high temperatures, I return to the test field to schedule a new competition. Start a study of a smoother, more accurate load for a 300-yard event. And the surprise jumps, with 2 grains less I'm almost 870 ms. (Note.- until now the preconditions of the QL had been fulfilled).

I return to program the same low load and I carry two rounds of the load of 880 ms of the national and my surprise is capital. Now I have 915 ms and a super hard pin and an inconsistency of EXT and SD. While the programmed low load (-2 grays), it remains fast 870 ms.

My case has been surprising for me, I never noticed a jump like that in a new barrel. It is chromobylene and comes lapping at the factory. They are 30 fps of inconsistency. And the temperature change maintained. And the gunpowder lot maintained.
 

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