Barrel Break in Procedure

[Frank Green]

You should be fine.

The biggest problem with the bullet failure is in the smaller calibers. Say 6.5mm and down. I've seen it in 7mm's but more rare.

I'm running my 6.5CM at 268,800 rpm. 7.5 twist barrels.

My 6BRA is a 7 twist but velocity is only 2800ish. Those are at 290k rpm give or take some and no issues to report. I've shot the 110 Hornady ATips and 107SMK and 105 Lapua's all with no issues. I built the gun primarily to test the 110gr class of bullets. That's why I went with the 7 twist. I've tried the 110SMK but for the accuracy I'm trying for...I cannot get them to shoot. Always throwing one or two fliers in every group. The 107's are frickin laser beams just like the 110 Hornadys!

 

[B23]

Hey Frank what about small cal bullets like say the Berger 55gr 20 cal leaving the barrel at 328500 RPM? I'm hoping for 600 rnds but now I'm wondering if that's being optimistic. Will more frequent cleanings help it live longer or is there anything else I can do to extend the life of the throat? They're both Krieger 20 cal 8tw barrels.

 

[slowelk]

On what caliber?

There are a lot of guys running 22 Creedmoor....try around 40gr of powder and more depending on what the actual load is.

6CM your in the low 40gr of powder.

If your running a 6GT then I'll say 34ish grains of powder.

If your running a 6BRA then I'll agree and say your in the upper 20's to a low 30gr powder charge.

Seen several guys at a match last summer....running 22CM. Didn't clean the barrel after the first day of shooting (put 120 rounds thru the guns)....they started getting random bullets blowing up etc...so here they are pulling bore snakes thru the barrels before the next stage to do a quick cleaning job on it. Next stage runs like a watch. They go to the next stage after that....and bam...a bullet blows up. So back to pulling a bore snake thru the barrel (I hate bore snakes as well).

They now have backed off the twist and that has helped bullet failure some but they've come to realize they need to clean the barrels more often with rounds like that. Too me...no different then the 6.5PRC and similar rounds.

Bullet failure can be caused not just by having a bullet problem....but from not cleaning, too much velocity and too much bullet RPM.

My hard line in the sand is 300k bullet rpm...bullet failure is a guarantee to start showing it's ugly face. I'll even say upper 200k rpms and it will start to happen. Especially when the throat starts to get rough in the bore. The bullet is going to take more of a beating.

Simple forumla..... velocity x 720 divide by twist = bullet RPM

So say 3100fps. x 720 / 7 twist = 318,857 rpm. Your on borrowed time!

Again we all want to go fast and at times I'm no exception but it's gonna cost us some where!

Later, Frank

When you're more or less recommending that these match shooters clean their barrels at the end of a day of competition, how thorough of a cleaning are you suggesting? Stripping down to bare metal, i.e. removing all carbon and copper? Or what? Stripping down to bare metal doesn't make sense to me as it would have to impact zero and or initial consistency.

 

[Frank Green]

Hey Frank what about small cal bullets like say the Berger 55gr 20 cal leaving the barrel at 328500 RPM? I'm hoping for 600 rnds but now I'm wondering if that's being optimistic. Will more frequent cleanings help it live longer or is there anything else I can do to extend the life of the throat? They're both Krieger 20 cal 8tw barrels.

328k.....that's screaming.

Rate of fire and how hot you get it and the number of rounds between cleanings will be be your friend.

What are you chambering it in?

 

[B23]

328k.....that's screaming.

Rate of fire and how hot you get it and the number of rounds between cleanings will be be your friend.

What are you chambering it in?

It's a 20-250 shooting the 55gr Berger's. I ordered a spare 8tw 26in Krieger barrel when I had it built knowing this wasn't going to be much for barrel life. It's a coyote/varmint gun and never gets much rate of fire which should help the throat survive a little longer but I'm still thinking 600-ish at best and it'll be toast.

 

[Frank Green]

When you're more or less recommending that these match shooters clean their barrels at the end of a day of competition, how thorough of a cleaning are you suggesting? Stripping down to bare metal, i.e. removing all carbon and copper? Or what? Stripping down to bare metal doesn't make sense to me as it would have to impact zero and or initial consistency.

When I shoot a big F class match....say I'm shooting 4 days in a row. On the low end about 60 rounds to as many as 80 or so in a day.

Yes I clean the gun every night. I get all the copper out per say. Carbon....even when a guy thinks he got all the carbon out....I'll tell ya most don't. Takes a shit ton of work to get all the carbon out. It's worse then the copper. So I don't truly believe that the vast majority of us get a barrel truly down to bare metal.

I don't believe it effects your impact/call it your cold bore zero as much as some think it does.

Figure in the variables.....environment, number of rounds on the barrel, what the shooter is using for cleaners and how he's cleaning etc....

I've been in plenty of matches where you shoot several times thru out the day. Let's for example say 3 relays at a 1k yards. No cleaning the gun etc...as you basically have no time. You shoot the first relay at 9am and your second relay at 12pm. Temp and environment conditions change and even though it's the same ammo and same dope on your scope from 3 hours ago....and the bullet impacts differently!

Watch the attached video link below. Classic example at the range at Lodi. The spotting scope was set up solid/permanently so the wind etc...wouldn't cause it to move and it was covered so no sunlight wouldn't directly hit/effect anything on the scope. Target didn't move of course. Range is 1k yards. The target if I recall correctly is a standard hi power target. Watch how the heat/mirage/moisture in the air and the terrain effects what you see. I say there is about a 3moa shift. Video started recording about 8am till about 5pm in the course of one day. Slow the video down to the slowest speed settings. The white marker is 3" in diameter.

Now you're getting into cold bore theory etc....and that's another whole topic. For the most part....I don't believe in it.

 

[Frank Green]

I can honestly say....good barrel/good gun....I've had only one. If I cleaned the barrel....and shot it at short range...I couldn't tell a difference but if I started at a 1k yards the first two rounds would be low. First round would be a mid ring 9 out the bottom and the 2nd round would be in the 10 ring out the bottom. After that the gun would hold 1/3moa for vertical at a 1k yards. This was a 6x47 Lapua. Chronographing that gun from a clean barrel the first two rounds would be 30-40fps slower than the rest. Till this day...it's the only one I've seen like that (excluding factory type rifles).

Again though at a 100 yards the first 5 shot group out of that gun would be a 1/2moa. You couldn't tell which where the first two rounds unless you where plotting them.

I say the biggest factor is the shooter. Conditions, ammo and not to mention how many rounds are on the barrel. As the barrel wears...it will/can change over the course of it's life.

Also like I've said before. Pay attention to the gun. It will tell you what is going on....just learn how to read it.

Watch the gun when you start shooting it. If the impacts start at the point of aim....and as you shoot it and the gun heats up...and you are not making any sight adjustments and you see the rounds/groups walking on the target...that could be a mechanical issue...or it could be a barrel issue. If it's a barrel issue...I say either the barrel is bowed (our way of saying bent) or the steel has a lot of residual stress in it. As the barrel heats up it's going to change (walk the rounds on paper)....when it cools the barrel goes back to where it started. The steel has a memory.

To me that is more common with button made or hammer forged barrels due to the amount of stress that is put into the barrel blank during manufacturing. If this is the case...your not going to get it out in my opinion.

Ammo....if your ammo has a big SD extreme velocity spreads that will make your vertical worse at longer ranges. In this case possibly nothing to do with the barrel but a ammo issue. I've seen ammo (even good match grade box ammo) have spreads of 60-70fps or more in 10 rounds fired.

Like I said...there are a lot of things going on.

 

[Lawnboi]

Appreciate the input on here frank. Iv read a lot of what you have to say over on the hide and I’m glad to see you on here as well.

Getting my second bartlein chambered as we speak!

 

[rayporter]

i like the vid of the target moving around in the light. it is something most can not grasp, even after being told. you can go to the line an hour later and your zero will not be what it was an hour ago, let alone the next morning.

 

[Frank Green]

My F Open class gun in 300PRC. Cold clean barrel. The target on the right was one round fired...then went to the ATIP's. It was the first time I shot the ATIP's thru the gun.

I say no cold bore stuff here.

This gun shooting 230SMK and 225ELDM's on the same relay at a 1k yards held right about 1/4moa for vertical. The ELDM's actually shot a 1/4moa flatter. First two rounds of the SMK went thru the same hole. Dialed a 1/4 min up on the scope and shot the next 12 rounds of the SMK that I had left and cleaned the target.

On that day I shot the gun at 800, 900 and a 1k yards. Wish I had the Atips with me that day but they where not out yet. Only prototypes/pre production ones had been made. Got the ATIPs a few months later.

 

[wind gypsy]

I've been in plenty of matches where you shoot several times thru out the day. Let's for example say 3 relays at a 1k yards. No cleaning the gun etc...as you basically have no time. You shoot the first relay at 9am and your second relay at 12pm. Temp and environment conditions change and even though it's the same ammo and same dope on your scope from 3 hours ago....and the bullet impacts differently!

Watch the attached video link below. Classic example at the range at Lodi. The spotting scope was set up solid/permanently so the wind etc...wouldn't cause it to move and it was covered so no sunlight wouldn't directly hit/effect anything on the scope. Target didn't move of course. Range is 1k yards. The target if I recall correctly is a standard hi power target. Watch how the heat/mirage/moisture in the air and the terrain effects what you see. I say there is about a 3moa shift. Video started recording about 8am till about 5pm in the course of one day. Slow the video down to the slowest speed settings. The white marker is 3" in diameter.

Now you're getting into cold bore theory etc....and that's another whole topic. For the most part....I don't believe in it.

So where can I buy a lightweight out of the box 1000 yard hunting rifle that compensates for this effect? (sarcasm)

 

[Lawnboi]

i like the vid of the target moving around in the light. it is something most can not grasp, even after being told. you can go to the line an hour later and your zero will not be what it was an hour ago, let alone the next morning.

Iv seen a number of people including myself tune a ballistic calculator in heavy mirage. Dosnt end well the next morning.

 

[Frank Green]

Iv seen a number of people including myself tune a ballistic calculator in heavy mirage. Dosnt end well the next morning.

Yep just told a guy that last week....

The calculators are good....but you still have to shoot and verify what your getting on target. It could be right on the money, very close or you say WTF just happened!

 

[rayporter]

a Friday afternoon rifle [that is a rifle shooting very well] is a wreck waiting to happen Saturday morning.

 

[Frank Green]

It's a 20-250 shooting the 55gr Berger's. I ordered a spare 8tw 26in Krieger barrel when I had it built knowing this wasn't going to be much for barrel life. It's a coyote/varmint gun and never gets much rate of fire which should help the throat survive a little longer but I'm still thinking 600-ish at best and it'll be toast.

Either way you cut it....that's gonna be a barrel burner. You where smart in buying two sticks right away.

Yes if your not running it like a PD gun and your not getting it smoking hot....that will help barrel life. Might be able to squeeze a 1k rounds or a little more out of it then would be my guess.

 

[B23]

Frank, not to get off track but since you mentioned bullet RPM earlier I gotta ask you something I've read about few times now and since Bartlein is one of the barrel companies that makes a 6 twist .224 barrel you're a good one to ask. I see claims of people shooting the 95gr SMK from 28-30 inch 6tw .224 barrels at 3100-3300 FPS. Depending on the velocity that's between 375K and nearly 400K bullet RPM. How the hell are they able to make these things survive those kinds of RPM's not to mention doesn't a long barrel like that cause even more problems under those circumstances?

When the 95gr SMK's first came out I talked to Sierra about what twist I'd need to shoot them if I did a 22-284 build. The tech at Sierra told me to save my money because they weren't designed for anything like that and even though the SMK's are a pretty tough bullet the RPM's would be excessive to say the least and those 95's were designed to be shot at 223 speeds.

 

[Frank Green]

It's a disaster waiting to happen. Time will not be on your side in my opinion.

According to Sierra the 95's need a min. of 1-6.5 twist. Probably based on NORMAL 223 velocities. The bullets are 1.300" long. Based on my twist calc at 2600fps. you need a 6.38 twist min. This is per my calculation but a lot of these new bullets are pushing my old graph to the limits of what I can come up with.

At 2800fps. I get 6.6 twist which gives me a bullet rpm of 305,454.

At 3200fps and 6.5 twist....I come up with a rpm of 354,461.

Your playing with fire and at some point your going to get burned by the match per say!

So according to the loading manuals at 223 velocities your looking at a normal velocity of 2400fps. This is what I will call a normal MAX pressure. So that gives us 265,846rpm. I'll say your golden at 2600fps and under. At 2600fps your at 288k rpm.

I do have a 6.5CM with a 1-6.75 twist barrel on the gun. I've shot the 140 Hornady ELDM box ammo (2700fps), 135ATIP, 150SMK and 153ATIPs. The 135's are running at 2800fps and the 150's at 2700fps.

So the 135's at 2800fps gives me 298,666rpm. I've had zero failures to date. The 150's are spinning at 288,000. Again no failures to date. I do feel though I'm on borrowed time. Once that throat starts getting rough...the bullet is going to take more of a beating and that's when the failures are going to start. Barrel most likely won't be shot out.

So why did I do the 6.75 twist? It was a guess. We we're making the test barrels for Sierra when they where developing the 150SMK. The design wasn't finalized. So the assumption was a 7 or a 6.75 twist was going to be needed. I jumped the gun and did the 6.75.

 

[Frank Green]

Back to you and the 3300fps and the 22-284 thing your talking about. It might work but the real question is....for how long? Like my fast twist 6.5mm. It's working for now but if I start having problems....it's not the barrel or bullets fault. I'm just over driving them.

We get blamed that the barrel is bad at times and then the bullet/ammo maker gets blamed for the other times. When in fact it is either shooter induced and or it's a combination of things that are going on to cause the issue and it's not one direct thing.

A couple of times last year I've had to beat guys up with 223 guns. Either they think it's premature barrel wear or they have an accuracy issue. These two different shooters are pushing 90gr bullets out of a 223 gun at 2800 to 3100fps. I've told them the load you are running is knocking on 80k psi. You have to back off the load and they won't do it. All I get it...well I don't have hard bolt lift or flat primers! Just because you don't see the sign's....doesn't mean it's not there!

 

[tdhanses]

That’s interesting on the rpm, never really considered it but ran the calcs and I’m good with my 6.5cm at 243k and 300wsm at 266k.

 

[bigmike23]

There's no such thing as barrel break in. It's bore conditioning. You are filling in the microscopic grooves in the metal with the copper coming off the bullet. A soft bullet could never ever change the much harder barrel without blowing up the gun on the first shot. Just like you can rub your nail against your phone screen for eternity, you're never going to scratch it. Just shoot your gun, have fun, and clean occasionally when groups open up. I find mineral spirits or hoppes works best. Makes the gun smell beautiful too