Forums
New posts
Search forums
What's new
Articles
Latest reviews
Author list
Classifieds
Log in
Register
What's new
Search
Search
Search titles and first posts only
Search titles only
By:
New posts
Search forums
Menu
Log in
Register
Install the app
Install
Forums
Hunting
Long Range Hunting & Shooting
Velocity Jump on new barrels
JavaScript is disabled. For a better experience, please enable JavaScript in your browser before proceeding.
You are using an out of date browser. It may not display this or other websites correctly.
You should upgrade or use an
alternative browser
.
Reply to thread
Message
<blockquote data-quote="NZ Longranger" data-source="post: 1537902" data-attributes="member: 14"><p>There are such widely expressed views on forums about cleaning, break-in and barrel life etc, and I can't help but wonder how many are actually based on fact rather than widely ranging unsubstantiated beliefs. </p><p></p><p>A few simple facts for you to ponder over.</p><p>1. Velocity increase <em><strong>always</strong></em> comes with a commensurate pressure increase. The pressure comes first, and the velocity is just a byproduct of it.</p><p>2. Pressure increase without a change in your load or powder/rifle temperature is always due to either increased friction, or/or decreased bore size due to changing surface structure or fouling buildup.</p><p>3. Unless you use a quality bore scope, you have no real idea of what is going on in your bore, cleaning or throat wise.</p><p></p><p>To give some cred to what I'm saying, we have an Oehler Ballistic Laboratory and measure pressure and velocity all the time, and we use a Hawkeye borescope with superb resolution - always. We also regularly slug our barrels to get an idea of bore dimensional changes that you can't see with a borescope. We build custom rifles in a range of cartridges including some very large wildcats that would be considered seriously overbore. We specialise in getting both good performance and relatively good barrel life out of these chamberings.</p><p></p><p>Velocity increase after about the 50 rounds onwards point in a new barrel well cleaned with solvent is always due to the throat getting rougher increasing friction, and also due to a dimensional change caused by the metal structure changing - surface platelets standing up and leaning down barrel if you can picture what I'm getting at here - and also depending on powder used, a hard carbon build up. No amount of solvent cleaners will change this, but it is easily kept on top of with sensible use of abrasive cleaners in the first 6 inches of the bore. Anyone who says you should not use abrasive cleaners in barrel break-in has never looked at the throat after even the most careful chambering job with the sharpest reamer and best lube - let alone the average factory barrel chambering job. The throat always has a lot of burrs on the downwind side of each land - sometimes even melted metal swaged into the downwind groove from a blunt and badly lubed reamer, and often some very deep annular grooving. Again, the quickest and often the only way to sort out these throats is with an abrasive or something like David Tubb's system.</p><p>We always break-in firstly by abrasive cleaning the throat to remove as many of these burrs and polish it as much as possible, and then with carbon solvents <em><strong>and</strong></em> abrasive cleaners, and keep on top of carbon and dimensional changes with regular abrasive cleaning of the throat. Since we started doing this, we no longer see the 50 to 100 round count pressure/velocity increase, and keep constant velocities right through the life of the barrel, and also hardly have to chase the throat at all. Contrary to what you may think, abrasive throat cleaning <em><strong>prolongs</strong></em> accurate throat life extensively. </p><p>So, so much more I can say on this subject, and proper cleaning/break-in techniques, but this should be enough to start some discussion!</p></blockquote><p></p>
[QUOTE="NZ Longranger, post: 1537902, member: 14"] There are such widely expressed views on forums about cleaning, break-in and barrel life etc, and I can't help but wonder how many are actually based on fact rather than widely ranging unsubstantiated beliefs. A few simple facts for you to ponder over. 1. Velocity increase [I][B]always[/B][/I] comes with a commensurate pressure increase. The pressure comes first, and the velocity is just a byproduct of it. 2. Pressure increase without a change in your load or powder/rifle temperature is always due to either increased friction, or/or decreased bore size due to changing surface structure or fouling buildup. 3. Unless you use a quality bore scope, you have no real idea of what is going on in your bore, cleaning or throat wise. To give some cred to what I'm saying, we have an Oehler Ballistic Laboratory and measure pressure and velocity all the time, and we use a Hawkeye borescope with superb resolution - always. We also regularly slug our barrels to get an idea of bore dimensional changes that you can't see with a borescope. We build custom rifles in a range of cartridges including some very large wildcats that would be considered seriously overbore. We specialise in getting both good performance and relatively good barrel life out of these chamberings. Velocity increase after about the 50 rounds onwards point in a new barrel well cleaned with solvent is always due to the throat getting rougher increasing friction, and also due to a dimensional change caused by the metal structure changing - surface platelets standing up and leaning down barrel if you can picture what I'm getting at here - and also depending on powder used, a hard carbon build up. No amount of solvent cleaners will change this, but it is easily kept on top of with sensible use of abrasive cleaners in the first 6 inches of the bore. Anyone who says you should not use abrasive cleaners in barrel break-in has never looked at the throat after even the most careful chambering job with the sharpest reamer and best lube - let alone the average factory barrel chambering job. The throat always has a lot of burrs on the downwind side of each land - sometimes even melted metal swaged into the downwind groove from a blunt and badly lubed reamer, and often some very deep annular grooving. Again, the quickest and often the only way to sort out these throats is with an abrasive or something like David Tubb's system. We always break-in firstly by abrasive cleaning the throat to remove as many of these burrs and polish it as much as possible, and then with carbon solvents [I][B]and[/B][/I] abrasive cleaners, and keep on top of carbon and dimensional changes with regular abrasive cleaning of the throat. Since we started doing this, we no longer see the 50 to 100 round count pressure/velocity increase, and keep constant velocities right through the life of the barrel, and also hardly have to chase the throat at all. Contrary to what you may think, abrasive throat cleaning [I][B]prolongs[/B][/I] accurate throat life extensively. So, so much more I can say on this subject, and proper cleaning/break-in techniques, but this should be enough to start some discussion! [/QUOTE]
Insert quotes…
Verification
Post reply
Forums
Hunting
Long Range Hunting & Shooting
Velocity Jump on new barrels
Top