Barrel to Barrel Velocity Variation

[chkunz]

When you replace a worn barrel with a new barrel, how much variation in muzzle velocity do you measure?

 

[TAJ45]

Barrel to barrel variation will pretty much negate any meaningful comparison. Jmho.

 

[David Christian]

I don’t understand the question. Each barrel is its own. However, if they are from the same manufacturer, same length and profile, chambered with the same reamer, with similar head spacing, using the same lots of components………..you should be in the ballpark after break in….

Lots of what ifs here.

DC

 

[Carl S]

I don’t understand the question. Each barrel is its own. However, if they are from the same manufacturer, same length and profile, chambered with the same reamer, with similar head spacing, using the same lots of components………..you should be in the ballpark after break in….

Lots of what ifs here.

DC

May be Frank G could shed some light on this.

 

[chkunz]

I don’t understand the question. Each barrel is its own. However, if they are from the same manufacturer, same length and profile, chambered with the same reamer, with similar head spacing, using the same lots of components………..you should be in the ballpark after break in….

Lots of what ifs here.

DC

Yes but how big is the ball park, and sometimes things are not what we think they should be, we have to measure to know. I am looking for someone who has measured this and will share the data.

 

[Liven The Dream]

Well My Ball Park is Very Very Small on two .284 F/Class Rifles.
They Both have Brux Barrels same everything else . ( Stock Different Color).
I can shoot the Same Load in Both Rifles . I do for my own keep the Brass separated by Rifle.
I may just be Lucky or missing something ?

Working on a Second 6 dasher with the same Stuff / will see and report back when Finished.

 

[David Christian]

Yes but how big is the ball park, and sometimes things are not what we think they should be, we have to measure to know. I am looking for someone who has measured this and will share the data.

I have 2 identical barrels that I am tuning right now on the same action. Same exact load, yet over the past 4 shooting sessions totaling 100 rounds per barrel they are shooting on average 9 fps apart. 2,800 and 2,809.

 

[chkunz]

I have 2 identical barrels that I am tuning right now on the same action. Same exact load, yet over the past 4 shooting sessions totaling 100 rounds per barrel they are shooting on average 9 fps apart. 2,800 and 2,809.

Thanks, that is the kind of data that I am looking for!

Here is the basis for my question. If I develop a load with a new barrel and the velocity changes due to barrel ware, does this effect my load. I now have data that says the velocity does not change over the life of the barrel for my application (223 26 inch WOA barrel) so that is favorable.

My next question was what happens to velocity when I change barrels and for your case it is 9 fps which sounds reasonable and should not be a big factor in the load tune. I know I will need to check my pet load when I change barrels and adjust as needed but it would be good if velocity does not vary significantly barrel to barrel.

Thanks again for your reply.

 

[David Milisock]

When you replace a worn barrel with a new barrel, how much variation in muzzle velocity do you measure?

Fifteen years ago I replaced a 6MM Remington 26", 1 in 9 twist factory barrel after about 2,500 rounds with another Remington factory barrel of the same specs. I started reworking my load and got back to the same place with the same powder and bullett. Plus or minus the difference from the widest spread in velocity in a 10 shot clocked group. From what I hear now days I wouldn't expect that from new Remington barrels.

Ten-year ago I replaced a 30-06 Shilen 26" air guage 1 in 10 twist with another by Shilen of the same specs and I got back to the same velocity but with a different powder.

Standard military bolt rifles for me become different rifles when barrels are changed out with military barrels. Once my military bolt rifles are dressed up by a decent smith barrel changes are about like my non military actions.

Military auto loaders that have been tuned from my experiance have been easy changes, my Garands I've worked with went from one National Maath barrel to the next with unnoticeable changes, same for HBAR AR 15 A2's. Accuracy of these rifles is not competition quality.

My AR15 M4E IN 6MM ARC is new so no concept, it had a bolt and barrel that were matched. Serious AR shooters at my ranges, tell me that barrel changes have been start over situations for them in terms of load development.

 

[DaveTooley]

Thanks, that is the kind of data that I am looking for!

Here is the basis for my question. If I develop a load with a new barrel and the velocity changes due to barrel ware, does this effect my load. I now have data that says the velocity does not change over the life of the barrel for my application (223 26 inch WOA barrel) so that is favorable.

My next question was what happens to velocity when I change barrels and for your case it is 9 fps which sounds reasonable and should not be a big factor in the load tune. I know I will need to check my pet load when I change barrels and adjust as needed but it would be good if velocity does not vary significantly barrel to barrel.

Thanks again for your reply.

Yes barrel wear can, but not always have an effect on accuracy.
Changing barrels covers a lot of variables. A previous pet load is nothing more than a starting point.
You can take two barrels made at the same time, same steel, same tooling by a reputable barrel maker and they can and most likely be slightly different.
There are no absolute rules.

 

[jelenko]

Thanks, that is the kind of data that I am looking for!

Here is the basis for my question. If I develop a load with a new barrel and the velocity changes due to barrel ware, does this effect my load. I now have data that says the velocity does not change over the life of the barrel for my application (223 26 inch WOA barrel) so that is favorable.

My next question was what happens to velocity when I change barrels and for your case it is 9 fps which sounds reasonable and should not be a big factor in the load tune. I know I will need to check my pet load when I change barrels and adjust as needed but it would be good if velocity does not vary significantly barrel to barrel.

Thanks again for your reply.

For the targets in XTC, I think the consensus is you can use the same load across replacement barrels. The guys with a lot of experience with load development say that doing a seating depth test for the new barrel could help.

 

[JSH]

I didn’t do a direct caliber replacement. Went from 223 to a 17 Remington. I had played with the 17 Remington on a couple of other setups prior to this. I went with a Shilen select against the advice of a few, didn’t want the wait.
I have velocities with a start load that the others struggled to do with an upper midrange load. Several have told me it is just a “fast” barrel. I try and stay under 4000 FPS with a case full of powder, that turned into S much of a project of trying to get to 3950ish with no issues.

 

[Fuj]

Brand "B" 30" barrel shot a 180gr bullet to 2787 topped out.
Other make brand "B" barrel took the same load to 2804, and
is now at 2827 kissing the next node, that the first brand "B"
never reached. Some speed up and some don't.

 

[Bob3700]

Have chambered two same make bbls with identical lengths n profiles for my Tubb rifle. Both chambered in6 XC and brass will interchange between them. With the same loads one bbl is 100 fps faster than the other Over the same chrono and it also shows up on the Shotmarker target. Each bbl. Is an individual.

 

[chkunz]

Have chambered two same make bbls with identical lengths n profiles for my Tubb rifle. Both chambered in6 XC and brass will interchange between them. With the same loads one bbl is 100 fps faster than the other Over the same chrono and it also shows up on the Shotmarker target. Each bbl. Is an individual.

Now that is an interesting data point.
Thanks for the reply.

 

[Acyr]

I rifle and chamber barrels for a small barrel manufacturer. Keeping chamber and headspace dimensions consistent is the easy part. Keeping rifle groove dimensions and depth consistent is an art. There is way more to making cut rifled barrels than most shooters know.

 

[Bob3700]

I rifle and chamber barrels for a small barrel manufacturer. Keeping chamber and headspace dimensions consistent is the easy part. Keeping rifle groove dimensions and depth consistent is an art. There is way more to making cut rifled barrels than most shooters know.

Agree about the ability to consistently chamber n maintain headspace. With the reamer micro-stops, maintaining the same headspace is not hard at all.

 

[chkunz]

I have now measured three "identical" 26 inch WOA 223 match barrels for velocity. I was surprised to find a velocity spread of 100 feet per second between them but even more surprised to find that my pet load for accuracy for my XTC short range (200/300 yards) did not change. I did not have to adjust powder charge to compensate for velocity change as I expected. I have not yet tested my Mid range pet load for accuracy in the new barrel.

Many times I find that opinions and guesses do not agree with the data. This is a good example. Thanks to all of you who replied to my questions and maybe my findings will be of interest to you.