I'll second that, my Tikka TAC A1 in 6.5 Creedmoor will shoot one hole groups all day if I can do my part. I had it out last Sunday first time since spring verifying a load of 143gr ELD-X with/without can. All 1/2 moa or better, simply a joy to shoot.

Last couple times I've had my TAC A1 out it wasn't shooting one ragged hole groups and I just figured it was me. Well last weekend I captured crono data with two different loads I had data from when it was new and I noticed my rifle sped up. I've read about that but never experienced it that I was aware of because I didn't have a crono until more recently.

I have yet to test my theory but I'm guessing it sped up just enough to put it out of tune.

Mostly just happy to see data showing it might not be me. Still enjoying this rifle every time I take it out.

Bryan Litz and the Applied Ballistics group discuss in various places the effects of the changes that occur in barrels with use that affect velocities.

One thing that I admittedly haven't explored much myself but which struck me as very unconventional when I first read it was his recommendation to scrub the bore with J-B (abrasive) compound at a certain point in the barrel's life. I don't recall all the details of the recommendation, but it might be something to look into.

Yeah I'll likely skip the abrasives.

Hornady podcast has a two or three part series on barrel cleaning, part two I found really interesting and I'm sure part three will be too. I didn't listen to part one, I think it was pretty basic stuff but part two gets into what they do in the lab vs their own cleaning and all sorts of findings and they do get into what to use and some abrasives that might be used under certain situations and which to avoid and why.

I see where the competition shooters that go through lots of barrels each year talk about speedup like at 200-300 rounds but I never really knew if that was a thing or what. Well I have the data, it certainly happened on my TAC A1 6.5 Creed. I still need to go back and see exactly how much and of course I'm not sure it's done but I think it was in the 30-40fps range which based on my ladder testing of powders would likely change my groups.

quote:

Originally posted by jxb:
Well last weekend I captured crono data with two different loads I had data from when it was new and I noticed my rifle sped up. I've read about that but never experienced it that I was aware of because I didn't have a crono until more recently.

I have yet to test my theory but I'm guessing it sped up just enough to put it out of tune.

Across multiple rifles and calibers, all my barrels have sped up early in the barrels' useful lives. Understand that a quality chrono is required to see this. The chrono must produce repeatable results -- regardless of lighting conditions, temperature, or phase of the moon. I've used Magnetospeed with great results for many years. I've seen inconsistent data from other brands.

IMO the first step of barrel break in is removing the tooling marks in the throat. This might take 5 or 10 rounds for a quality barrel. The second step is smoothing out the full length of the bore, so the bullet accelerates the most efficiently. This might occur in as little as 40 rounds, or maybe as much as 100 rounds. I generally find that around 70-80 rounds the muzzle velocities stop increasing, then stabilize. My barrels include Bartlein, Krieger, Wilson Combat, and Proof. MV increases from first shots to stable have ranged from 40-ish fps to 100-ish fps.

My second 6.5CM Bartlein was a little different in its break in. MV appeared to stabilize after some 75 rounds, so I figured it was ready for PRS-type competition. During the 2nd day of a weekend's match, POI was a little high on long targets -- those in the 700-1000 yard ballpark. Throwing rounds high has been my primary error issue for years, so I figured technique was the problem. I chrono'd the following weekend, and determined that my MV did increase some 30-ish fps IIRC -- somewhere in the 175 round ballpark. I discussed the secondary MV plateau with my gunsmith, who has plumbed untold hundreds of barrels. He said that it's quite rare for a barrel to have an initial MV plateau, then speed up a second time. He's heard of it occurring maybe 2 or 3 times.

Once a barrel's MV stabilizes, it's all down hill from there. Throat erosion and bore wear will slowly cause MV to decrease. With many stainless barrels, the MV decrease will be occur suddenly. Accuracy at distance will decrease noticeably, and POI at distance will drop. With many chromoly barrels, as they become badly eroded, the deterioration in accuracy & MV is more subtle. With chromoly, the deterioration likely starts earlier and stretches out over a longer period.

Fortunately for most shooters, the round counts which affect barrel accuracy are pretty high. For 6.5CM used in PRS-type competition, around 3000 rounds the barrel is becoming compromised. For those who never let the barrel get warm, maybe 4000 rounds before accuracy potential goes south.

quote:

Originally posted by sigfreund:
One thing that I admittedly haven't explored much myself but which struck me as very unconventional when I first read it was his recommendation to scrub the bore with J-B (abrasive) compound at a certain point in the barrel's life. I don't recall all the details of the recommendation, but it might be something to look into.

I know a few steel match competitors who do this as their barrels age. Throat erosion results in an alligator skin pattern on the barrel. This is a great place to build up copper and carbon. J-B paste can remove this buildup.

I have experienced carbon buildup in the throat of most of my barrels as they age. I prefer more gentle methods to remove these carbon rings -- patches and cleaning fluid. Sometimes requiring a fair amount of elbow grease.

Gunk buildup in the throat of older barrels is nothing to be sneezed at. Carbon rings have hosed my accuracy in a couple of matches, and I've seen it occur to a few other competitors.

quote:

Magnetospeed

I started off with a Magnetospeed, but now using a Garmin Xero. So there could be some differences between my then/now data due to that but I would think <10-fps. I'll pull data via the Garmin going forward so will be able to see if it's settled or not and tune it once it has.

The groups went from as you saw before to all holes just not touching, so it's not like it's a huge change, but certainly noticeable.

BTW Fritz thanks for sharing that info, it's always interesting to see data like that.

On carbon, yeah I learned early on as a varmint shooter that you must stay ahead of it. I actually have an old shot out M77 Swift that is so bad it's a wonder it still shot, let alone not too bad. There's a huge pile of carbon in the throat and heat cracking over the first 5-7" is like canyon land or more correctly Bryce.

It's one of the main reasons I picked up a not so costly borescope some time back, so I could see what's really going on and also so I could track each barrel from new through its life.

Being able to see exactly how much carbon there is in the throat is great and especially looking for a carbon ring getting started in front of the case. Same goes for the balance of the barrel, it just makes it super easy to clean enough where it needs it more than other places and not overdo. No more depending on reading patches, I can verify and go back and hit those places needing more attention.

Between cleaning and bore scope viewing now I see the direct correlation between a nice double lapped match grade barrel (Benchmark in my case) and my Tikka TAC A1, and then my factory barrels. The Tikka is worlds better than the factory barrels which I think they just roughed out and called it good, but the Benchmark is soooo nice. I actually have two of those, No. 1 in 6GT and M700 in 22-250, they both are super nice and clean like a dream. Later this year I'll get my first Bartlien which will be another 6GT but on a BAT TR and I'm sure it will be super nice too.

Cleaning is where this correlation really shows. The match barrels need very little cleaning, I'm done in 6-10 patches total. Even after using my can, only one wet patch and most black is gone whereas on the Tikka after the can it's more like 5-6 to get the soot out and lots more patches to get it clean, maybe some brushing too.

My factory barrels I don't run a can on and they still need a lot of care. They are so rough inside I generally only partially clean them so they stay somewhat fouled. Like getting most of the copper and carbon out. Again staying on top of the throat area for sure.

I can also tell the differences between them all in the number of fouling shots. My match barrels are usually only one cold/clean shot needed and then the group settles, so that first one looks like a flier. The Tikka usually 2-3 after cleaning. The factory barrels, lol well they are all over the map but all take several shots from cold/clean to foul in.

quote:

Originally posted by jxb:
I have yet to test my theory but I'm guessing it sped up just enough to put it out of tune.

I still need to go back and see exactly how much and of course I'm not sure it's done but I think it was in the 30-40fps range which based on my ladder testing of powders would likely change my groups.

A few years ago I experienced unexpected MV variations among lot numbers of Hornady 6.5CM 140 ELDM factory ammo. It came to a head when I attended an ELR match (800 to 2100 yard targets) with a new batch of ammo. Ammo that I briefly tested for accuracy out to about 400 yards, but didn't test MV. This ammo was accurate, but was slower than expected, requiring that I develop elevation dope on the fly for the first day of the match. Not my best scoring that first day, but I was fine for the second day.

After the ELR match, I spent a bunch of phone and email time with SGammo and Hornady. The Hornady rep questioned my MV results across multiple lots, as their test barrel MV data supposedly showed little variation among lot numbers. So...I sent them a few rounds from various lots. And they found MV variations from my ammo that were larger then expected or documented. I received a big round of apologies, and a fair amount of new ammo in the mail. I suspect some testing engineers weren't quite right with the original MV test data reported up the chain of command. But I can't confirm my suspicions.

Regardless, I now segregate my match ammo by lot number and I have MV data for each lot. On matches where targets are out to maybe 800 yards, it's not a big deal. ELR -- that's whole 'nuther ballgame. My slowest batches are around 2790 fps, with the fastest ones are around 2880. All lots produce great groups at 100 yards. And 500 yards. And beyond 1000 yards. It's all about drop at distance, and to a lesser extent drift.

From all the guys around me who handload, I get there are nodes for barrels & loads that perform best. IMO such variations are challenging to see at 100 yards, but they become more clear cut at say 500+ yards. The vast majority of the time, we shooters cause more variations than our equipment.

Yeah I started out with Norma 143 match and I still have most of two cases of that. I do intend to chrono boxes from each so I know the numbers for exactly the reason you indicate. It will also allow me to compare to first case which I have chrono data on and my original results were from that first case but I created handloads with 143 ELD-X that matched for MV in addition to another load that's about 100fps faster and appears to produce similar results.

That said I still have yet to test at distance and you're not even the fifth person to say I need to test at 600 and 1000 to really know how my loads will perform. One of these days I'll have the time to do just that.

Years ago before HSM and some of the others got so busy and we could actually get deals on ammo and rather than reload for a long outing I'd just buy cases of what I needed. I experienced just what you were talking about here, except I had no chrono or data to back it up. Basically poi would change lot to lot so I'd simply re-zero and keep making red mist. Of course that's nothing like competition where it actually matters but I remembered that all these years later as I started buying cases for the TAC A1.

I'm guessing my largest challenge at distance will be learning to read the wind and mirage. Can't really get that from an app or a dope chart, but I have several books on the subject. I just need to actually read them. lol

Of possible continuing interest in view of another recent thread.