Rnd count improving accuracy??

[ericf]

I have two rifles that seemed to have improved with round count. One is a AR, custom built years ago for NRA match. The accuracy (grouping) sucked, but improved over time and count. at around 150, it began to show promise, then around 200 it really shined. Another bolt gun in .308, was very disappointing till about 150 rounds down the barrel. Now it's becoming quite impressive.A definite "keeper".
Have others seen this happen?
I discussed this with my Father and he equated it to the shooter. I don't think so,
Any opinions? is it just a fluke.

 

[bohem]

Re: Rnd count improving accuracy??

Some would attribute it to "break in"

I attribute it (depending on the actual size of the inital "bad" groups) to being that you're simply becoming more comfortable with the rifle and accustomed to it's idiosyncracies such as the scope, cheek weld and trigger.

 

[gugubica]

Re: Rnd count improving accuracy??

It could be both, but the "break in" idea has merrit.

When a projectile travels through a barrel, it has an effect on it. This is particularly true with factory tubes. There will be minute imperfections on the rifleing (burs, etc.). When enough bullets are fired, these imperfections smooth out. In my experience, that majic number is right around 200.

This is why hand lapping exists, to smooth out these imperfections. What you are doing is essentially lapping the barrel a very small amount each time you send a round though it.

 

[Rob01]

Re: Rnd count improving accuracy??

I don't chrono for data or shoot a rifle in a match until it has 200 rounds down the tube for this very reason.

 

[ericf]

Re: Rnd count improving accuracy??

I first thought it was me. As you stated, "getting used to the rifle". But the grouping both these rifles would produce were multiple inches at 200 yards (2-3). I could use the GAP and produce .5 at 200. Then pick up another and shoot a 2.5" group with the same ammo. but now, 150 rounds later it's at less than 1" and seems to be rapidly improving the more it fires. I tend to believe that it's a function of the barrel continually "breaking In" (being polished out)
I just wanted to discover if I'm alone in this observation.

 

[Rob01]

Re: Rnd count improving accuracy??

You're not alone. It's been known for years. The smith who built my first custom rifle years ago told me that accuracy will increase after about 200 rounds. It's not getting used to the rifle but the process of sending bullets down the barrel. Might be different in all barrels but 150-200 rounds is a good ballpark.

 

[NukeMMC]

Re: Rnd count improving accuracy??

I have an article from an old NRA Handloaders Guide that discusses barrel life. They were discussing test barrels at Frankford Arsenal and showed how, using M72 match ammo, the mean radius of groups at 300yds would rapidly decrease during the first 500-1000 rounds, then continue to decrease group size out to about 2500-3000rds! Accuracy would then essentially level out until 8000-10000 rounds.
Here's the first page of that article:

 

[BLAWTON]

Re: Rnd count improving accuracy??

I would think this has more to do with the throat then anything. You will notice the velocitys increase as the barrels smooths out. Most barrel will copper up quite a bit untill you have 50-100 rounds out of them which has do do with the throat breaking in. As it moves it will affect how well it shoots untill the velocitys stabilize. When it moves it will change alot of things but usually just get better untill the barrel is burned out and start to chip and crack.

 

[jrob300]

Re: Rnd count improving accuracy??

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Rob01</div><div class="ubbcode-body">You're not alone. It's been known for years. The smith who built my first custom rifle years ago told me that accuracy will increase after about 200 rounds. It's not getting used to the rifle but the process of sending bullets down the barrel. Might be different in all barrels but 150-200 rounds is a good ballpark. </div></div>

I expect to get laughed out of here for this, but here goes...

I ordered a new hand lapped match barrel for my 300. Get the gun back and the first 15 shots I fired through it were the 3 finest grits of Tubb's Final Finish. Start shooting my handloads for development and the first 3 shot group was a cloverleaf. Next 3 shot group was horizontal 3 shots in less than 1/2". Next group, 3 shots big ragged hole. WOW! Happened to look carefully at my cases and noticed that they looked a little fat above the belt. Long story short, dull reamer buggered my chamber.

Barrel #2 from same guys (w/new reamer

). Ran out of FF bullets and REALLY was itching to shoot. So all it saw for the beginning of it's life were 200g smk's. Long story short, this barrel with same loads started shooting small groups at about 200 rounds (I log every shot in my notebook). The barrelsmith said this was not unusual at all. FWIW, the 2nd barrel has yet to equal 100 yard performance of the 1st.

Coincidence, or does David Tubbs know a thing or two?

John

 

[Michael]

Re: Rnd count improving accuracy??

Just did a break in on pair of rifles for a friend. Neither would shoot at all well until about 80 rounds, and by 100 rounds they were acceptable and improving.

Any Shilen I've ever owned ( lots ) took 200 rounds before it would really produce consistant accuracy on an acceptable level.

 

[-=boone=-]

Re: Rnd count improving accuracy??

That is rather interesting to say the least.

 

[Rob01]

Re: Rnd count improving accuracy??

Jrob, actually David does a break in with his TMS rounds which is 3 TMS, clean and then 3 more TMS. The TMS are basically the finest grit in the FF kit. Also they don't recommend the FF on custom barrels but it would seem to not have hurt anything in your case.

 

[jrob300]

Re: Rnd count improving accuracy??

Interesting...

I called them, told them I had some FF bullets left over from running them thru the stock barrel. Told them I had a handlapped barrel and wanted to get the reamer marks out. What I did is what they told me..

Will get some TMS for this barrel. It's probably about that time (400 rds)

Thanks Rob


btw FF did nothing notable to my stock barrel other than lower velocity by about 50-75 fps. Still copper fouled like a b****


John

 

[Seekers]

Re: Rnd count improving accuracy??

OK, so taking this 150-200 round period (and continued benefit) into consideration, wouldn't a break-in of cleaning after every round for 10, then 3 etc... let you reach that point sooner?

Or are you sacrificing too much barrel for too little benefit?

Thanks,

Seekers

 

[Keith Johns]

Re: Rnd count improving accuracy??

Cleaning every round for 20 or so keeps copper from getting trapped and allows the barrel to smoothen out properly.

For break in you must use a good copper remover. Deep clean it and get all the copper out but dont go nuts and damage your barrel.

I've noticed barrels getting more accurate at about the 200 round mark too.

 

[jrob300]

Re: Rnd count improving accuracy??

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Rob01</div><div class="ubbcode-body">Jrob, actually David does a break in with his TMS rounds which is 3 TMS, clean and then 3 more TMS. The TMS are basically the finest grit in the FF kit. </div></div>

I got some TMS and actually, they compare very closely to the coarsest or next coarsest of the FF bullets. Lots coarser than the finest.

Anyway... Follow up. My shooting partner got his new 300WM barrel back and we went to the range yesterday. Shot 3 TMS cleaned to bare metal (45 mins.) Shoot 3 more TMS, cleaned to bare metal (40 mins.) Fire 3 200g smk's. Shoot's about 1" Clean. 10 patches, 10 minutes. Fire 3 more SMK's. Clean. 6 patches 5 minutes. Fire next 6 in a row (letting cool). Shoot into .5". No copper fouling.

It now puts shot after shot into the same spot. After 12 rds. This is the way I broke in my first hand lapped barrel and experienced the same thing. My second only saw a steady diet of SMK's and took 200 rds. to really group and stop fouling.

I really do think there is something to the TMS cleaning up the chamber. I'm a believer.

John