Barrel speed up patterns an experiences.

[jasmay]

I was wondering what people's experiences are with barrel speed ups, what sort of pattern did you notice how long did it take to settle, what sort fps jump did you experience.

Currently running in a new barrel and starting to see the average velocity sneak up throwing shots out the top (using a Chrono while shooting) and is tending to throw shots 20fps faster with the odd 30fps.

Hoping this will settle at some point then I'll tweak my load back down to where she is a hummer.

So I am interested to learn more about what patterns in this process others have seen/had!

Thanks

[scott/r]

There's been a few of us at North Arm having the same thing happening. Mine is a new barrel, so I was expecting a bit, but not 100 fps from between the first 150 rounds. Another member had the same with a barrel about half way through it's life. He changed to br2 primers from federal gold and problem solved. Both of us were using federal primers and both of us were also seeing a constant rise in speeds during a string of shots. I will be trying the br2 this weekend coming as well to see if it helps me to.

[ShaneG]

Hey Jason
Give my impressions generally.
First experience was a Krieger on my first F class .223.
Upon checking after 300+ rounds it had sped up about 100 fps.
After 2000+ rounds it had slowed back down due to ? Erosion of throat? And general wear on length of barrel.
Having used quite a few Krieger and Bartlein now as well as a couple of Brux over the last 7 years I would say all barrels speed up a little initially.
Guess it has to with lapping in further as they are shot?
The Kriegers seem to take more shots to settle for me and may speed up more?
As many as 300 rounds? I have made it a personal rule to not shoot a new barrel in a big comp.
Bartleins seem to stabilize earlier with less increase?
Last couple increased approx 30 fps
Maybe they are lapped more at the factory compared with Krieger?

Finally I think we need to maintain a log of velocities as I mentioned at the beginning - after a fair amount of use the V will decay?
See if others agree?
Shane

[David B]

Shane could be a lot of factors including fouling, temperature of the day and location. The throat smoohng out, batch change in powder. I wouldn't agree with your finding on Kriegers . I have had a barrel give a great performance with 40 rounds. (Non of mentioned manufacturers)
David

[DenisA]

I had a 300WSM that wouldn't stop speeding up, sorted that out and then found that my .284W kept slowing down. Probably best not to take any advice off me.

I think it depends on cartridge, bullet, powder, etc. They all seem to behave differently. But I'm pretty certain that the question is .308W specific.

[DenisA]

In my most recent 155gn bullet, .308W load development, I persisted with a hot node of above 47gn of ar2208 because I wanted the speed. It was very accurate but sometimes threw some .5 MOA flyers. The node length was short being the hot node and I think the flyers were rounds tending to the extremities of the node. I've been redeveloping at around 46gn and the node is longer and group pattern more uniform. Different thread, but, This is another reason why I think SAUMs are a better option for 180's than a .284W.
In my experience to date, all cartridges have always been more consistent with a little air gap.

[plumbs7]

New Bart , which I'm very happy with , started out at 2860 fps and now 70 rounds as I mentioned before has run away with 2910 fps 51.4 gr ! It still held its tune all the way through its speeding up! I'm only backing off load from learning with the 7-08 Ai not to push things too hard ! It seems to have stabilised . My Brux at 2855 ish is 52 gr and now stable but has had 200 or so !

Lilja .308 3 grove I've had a number of them ! Always speed up around 30-40 fps after 80 odd rounds !
Might also add that I've been very happy with that brand too for a Button barrel !

Denis , With 80% case capacity with faster powders . B Litz did some testing that supports your claim .

But every barrel is different and from every barrel manufacturers you get hummers and then some that need a little extra work in tuning !

[jasmay]

Thanks for the replies so far, all handy info guys!!

[Chopper]

i think all barrels change with wear and fouling or whatever , heat , altitude throat wear,thats why you have elevation knobs, they dont stop changing, Be great to have a barrel to hold zero for 2,3000 rounds ,with an easy cleaning system, but they dont, homework before shoots and cleaning is the trick, Know your barrel, your Not the boss, one projy, one powder, and chase that seating depth that you loose through wear ,worked for me in one barrel I had that won a lot, Chop

[ShaneG]

Jason , either PM me or best normal email or call if I can help at all?
I am pulling back from offering public opinions / advice.
Cheers
Shane

[Longranger]

I wonder sometimes if the chronograph used gives different results on different occasions sometimes. We use an Oehler 35P but I don't trust it for use to use consistency. Small temperature and light changes on these devices show up there deficiencies. This makes it hard to validate changes in velocity with increases in round counts.
I think the LabRadar or Magneto speed devices have the edge here.

[Julian D]

Unscrewed a new barrel yesterday because it is playing up a bit. Bit like yours Denis, did initial load testing & found a nice load, seemed to stay fairly consistent , took it away for a prize shoot & it was all over the place like a mad woman's shit ! Came home & tested the ammo & it was about 50fps slower than intended, but would throw 2 or 3 out of 10 at it's normal speed........ originally thought it was an ignition inconsistency, but ran another barrel yesterday with the same powder, primers & cases & do not have the same issue. So on the whole it is slower, it has now 220 rounds through it, maybe it will come good, hopefully when I eventually go back to it, it will start to behave itself.
but I am still fairly new at this game, and most days I have WTF head scratching episodes..... half the fun I say.

[ajvanwyk]

I had the same experience that Shane described in my single Bartlein (certainly not a sample size). I am in some way either pedantic or fortunate to have noted something about each firing I have ever made in the barrel.

For testing this is usually a group size, POI for a given load or velocity measurement. I have now fired roughly 700 rounds through my SAUM and what I can glean from the data is that for a given amount of powder (this is consistent across 7 powder variations) the barrel increased in speed with 20-30fps from 50 rounds to about 300. After that the barrel came back and the last chrony work I performed gave me the exact same velocities as those measured when the barrel was new.

Albert

[RDavies]

I would say at least 80% of my barrels went through a speed up of some kind, usually 30-50 fps or so, with some increasing much more. Talking to others, and from my experiences, it is not barrel brand specific, but a case of luck whether your particular barrel gets a perfect gas seal straight away. (the bullet is just a piston with no rings, trying to seal 65000 psi so some might need a little running in). I have had some which never got the velocity jump and velocity stayed the same for another 4-500 rounds or so.
Most got relatively sudden speed jumps at around 100=150 rounds and kept increasing for 80 shots or so.
I have only had a few which kept increasing for a lot more shots, or just got very erratic in their juvenile stages but luckily these problem childs settled down very well by 350 rounds and are now some of my best ever barrels.
As I mentioned before, it doesn't seem brand specific. Out of 3 indentical barrels from the same maker recently, 2 got no speed up at all and were hummers from the first few rounds, while the 3rd had the worst teenage stage from any barrel I have ever had. Other barrel brands before this were the same.
One thing which was common with all was that by shot 500-600 or so (with F open calibers) the velocity starts to slowly go down again.

[Frank Green]

It does happen but not all the time. As has been mentioned I think the caliber, chamber, bullet and type of powder being used are all contributing factors. As an example my .284win. F Class gun has never shown a change/increase in velocity at all. Still running the same lot of powder and up until the last F-class champs I shot in it has been the same lot of bullets and for the most part the same lot of primers. Also it didn't matter if the barrel is clean and or dirty.

I also feel how nice the reamer cut the throat etc...has something to do with it as well as bore finish.

My last 6x47 Lapua barrel after I cleaned the barrel the first two shots where always 30-40fps slower then the rest but after that always on call. I feel in this case the barrel wanted some fouling both carbon and copper in it.

I know some ammunition makers will not use a test barrel for data until they have a min. of 100 rounds on them. They will still record the data etc...but will not use the barrel for hard testing till it has the 100 rounds on it. They want to know the barrel has settled down and is repeating/being consistent.

As has been mentioned the barrel will change over the course of it's life. The throat is wearing etc...and the barrel will typically lose velocity after x amount of rounds but usually you retune your load and you can get it back.

Later, Frank
Bartlein Barrels