HUGE velocity increase going from 338LM to Improved

[mpepin07]

Hey guys I just got back from my first trip to the range with the new barrel installed on my Ruger Precision. It is a 30" McGowan chambered in 338 Ackley Improved with 40° shoulder. Originally, my hope for this barrel was to be able to throw 300gr projectiles at 3000fps. After this first range trip, it seems like I got lucky and received one of those "fast" barrels that I hear people talk about from time to time. Using new Lapua brass, RL33 and 300gr Nosler RDF's for fire forming, I was seeing ~2920fps with 94.0gr and no signs of pressure. For reference, the stock 26" barrel gave me around 2650fps using the same load. I find it hard to believe that an additional 4" of barrel length is giving me a 270fps increase.

Now here's the really crazy part. I borrowed some already fire formed brass from my buddy who also has a 338 Ackley. Using RL33 and the Nosler RDF's again, I worked my way up to 103gr before seeing pressure signs, at which point my velocity averaged 3178fps!

I will be honest, I am partially posting this to brag... but in seriousness, I have never heard of someone getting velocities this high from this chambering. Do I have anything to worry about here, or should I just shut up and be happy that I won the barrel lottery?

 

[diverdon]

Accuracy?

 

[mpepin07]

I was typically seeing .75 MOA with a few groups in the .5 range. Very pleased

 

[diverdon]

Wow!

 

[Mordamer]

There's no such thing as a fast barrel. Just people who are fooled about how hot their loads really are. There are lots of factors that make a load run at higher pressure in one barrel than another. You can't cheat physics. Acceleration=Force/Mass. In this case the force is the pressure in your barrel. The only way to get a lot higher velocities than everyone else is to run at a lot higher pressure than everyone else.

In my experience normal velocity variation from barrel to barrel is in the realm of 30 FPS if all other factors are kept constant. I have had multiple barrels from different manufacturers that had different rifling, different twist rates, etc. All these barrels were chambered with the same reamer and the same ammo was shot in them and the norm was to have them within 20 FPS of each other. I'm convinced that for the most part when people have a "slow" barrel they are running at a lower pressure and when people have a "fast" barrel they are really just running at a higher pressure.

Be careful. Sometimes pressure signs are harder to notice and sometimes they don't show up for several firings until you all of a sudden get heavy bolt lift etc. I'd recommend backing your load off and not chasing velocity. A slow consistent load beats a less consistent fast load all day at any distance.

 

[Mordamer]

Or....... your velocity measuring equipment is suspect?

 

[mpepin07]

Or....... your velocity measuring equipment is suspect?

I considered this, but known loads were shot from another rifle today and chrono showed velocities within the normal range.

 

[DTF370]

Hey guys I just got back from my first trip to the range with the new barrel installed on my Ruger Precision. It is a 30" McGowan chambered in 338 Ackley Improved with 40° shoulder. Originally, my hope for this barrel was to be able to throw 300gr projectiles at 3000fps. After this first range trip, it seems like I got lucky and received one of those "fast" barrels that I hear people talk about from time to time. Using new Lapua brass, RL33 and 300gr Nosler RDF's for fire forming, I was seeing ~2920fps with 94.0gr and no signs of pressure. For reference, the stock 26" barrel gave me around 2650fps using the same load. I find it hard to believe that an additional 4" of barrel length is giving me a 270fps increase.

Now here's the really crazy part. I borrowed some already fire formed brass from my buddy who also has a 338 Ackley. Using RL33 and the Nosler RDF's again, I worked my way up to 103gr before seeing pressure signs, at which point my velocity averaged 3178fps!

I will be honest, I am partially posting this to brag... but in seriousness, I have never heard of someone getting velocities this high from this chambering. Do I have anything to worry about here, or should I just shut up and be happy that I won the barrel lottery?

Not trying to hijack... but did you run into any feeding issues after going to 338LMAI in your RPR?

 

[mpepin07]

Not trying to hijack... but did you run into any feeding issues after going to 338LMAI in your RPR?

No worries. I was only single feeding on that range trip. I will try using the mag next time and report back.