Thoughts on the Defensive Edge +P throat design

[odoylerules]

From my understanding it's essentially a "bore rider" type throat...??

I don't know what a bore rider is, but probably yes.
The +P design is proprietary, but my understanding is it's a graduated throat. Instead of the bullet hitting the lands all at once, this design starts the bullet spinning slowly and gradually gets to full contact. Thus drastically reducing pressure. If used in conjunction with a slow burning powder, it allows you to load more powder, and hopefully, significantly increases velocity.

 

[Pdvdh]

I know of one chambered in .338 that lasted less than 500 shots. Closer to 400. But do I absolutely know it was the throat design? Nope. Not even the owner knows for sure. It was one specimen. One barrel. But one is enough to make me cautious. This barrel should have been good for at least 1000 shots. More like 1300 shots.

One barrel doesn't prove anything, but it raised my eyebrows.

 

[cjl2010]

I believe Sam Millard is on his 2nd 260T barrel. First one lasted 1300ish I believe.

 

[adam32]

We've messed with the bore rider throats before...velocity did go up a little but accuracy went to crap. They are designed for drive band bullets like the GS Customs I'm pretty sure...

Standard throats for us from now on.

 

[bigngreen]

It's not a bore rider throat it just has shallow rifling for a section before going full depth, this has been done of and on over the years dating back to the 80's for at least one reamer maker I've talked to. You can gain speed but you have to have the capacity to take advantage of it, it can bump you to a powder you don't want to use. It without question lowers barrel life, half the land is gone, no way around it.
I've played with the throating on a number of them and the rifles never changed in accuracy but did allow using a powder to run the speed I wanted. There are numerous benchrest shooters shooting some version of hybrid throating be it the dual land or bore rider, most I know don't find it really worth it.

 

[Pdvdh]

It without question lowers barrel life, half the land is gone, no way around it.

Hard to argue with the obvious, after it's been pointed out.

Nitriding the +P throat should be a worthy investment. And would be a great test on the throat protecting affect of nitride / melonite treatment.

If the +P throat has 1/2 - 2/3 the life of a normal throat, it wouldn't require as many shots to assess the value of nitride treatment.

Bad part with nitride is inability to set the barrel back after the throat is toast. Not sure if that's a great option anyhow... Always seemed like a compromise to me, for anyone looking to maximize accuracy.

 

[odoylerules]

I spoke to Shawn at Defensive Edge. He said they've been getting around 1300 rounds on their barrels. Sometimes more, sometimes less depending on how it was treated

 

[Shawn Carlock]

The barrel you speak of that dies at 400 rounds had a steady diet of N570 run through it. 570 has been the death sentence to more than one good barrel. Chambered in 33 8Terminatro the 570 will cut barrel life in half! There have been enough barrels run their course with N570 and RL 33 to compare and support this. I though reducing the throat rifling depth might decrease barrel life that is why we didn't release the +P design until we ran a longevity test on it. The original barrel chambered in 338 Edge +P was fed a steady diet of H1000 96-96.5 gr and drove the 300 SMK's at 2935-2950. We took the barrel off at 1000 rounds, the accuracy was still under 1/2 moa and the throat was burn forward only .027". For the performance we were getting I though this was great so we started building rifles on it.

 

[Idaho Trecker]

The barrel you speak of that dies at 400 rounds had a steady diet of N570 run through it. 570 has been the death sentence to more than one good barrel. Chambered in 33 8Terminatro the 570 will cut barrel life in half! There have been enough barrels run their course with N570 and RL 33 to compare and support this. I though reducing the throat rifling depth might decrease barrel life that is why we didn't release the +P design until we ran a longevity test on it. The original barrel chambered in 338 Edge +P was fed a steady diet of H1000 96-96.5 gr and drove the 300 SMK's at 2935-2950. We took the barrel off at 1000 rounds, the accuracy was still under 1/2 moa and the throat was burn forward only .027". For the performance we were getting I though this was great so we started building rifles on it.

Are you also saying that 33 is almost as bad as 570 in regards to barrel life in the 338 edge or edge +p?

 

[tim_w]

The only issue you have with longer throats even the gradual ones is having the ability to chase the lands. You are already starting out with a long throat that either gives you more of a jump or setting the bullet out further. As the lands erode you need to set the bullet out farther if you want to keep the same jump. With some cartridges and bullets the amount of jump is very forgiving......IF the chamber has been cut dead nuts straight with the bore. Others can be a bit finicky with changes in jump.

The other issue would be if it was a mag fed cartridge. You will need the mag COAL to be able to set those bullets out further to keep the same jump.

I am a firm believer in a high quality nitriding job and without any doubt what so ever I know in all my barrels it has increased throat life. I would say by double.

 

[Shawn Carlock]

Are you also saying that 33 is almost as bad as 570 in regards to barrel life in the 338 edge or edge +p?

I am saying the 33 is twice as good as 570 in terms of barrel life. you will see double the round count form 33 as compared to 570.

 

[Idaho Trecker]

I am saying the 33 is twice as good as 570 in terms of barrel life. you will see double the round count form 33 as compared to 570.

Thanks Shawn! I just started running 570 in my edge because of the better temp stability but may go back. I keep hoping alliant will come out with something between the 26 and 33 in burn rate with better temp stability.

 

[Shawn Carlock]

You and everyone else buddy.

 

[BClrh]

Shawn how would R33 compare to h1000 for barrel life? Have you ever had any luck with retumbo?

I was about to start loading a 28 nosler with n570 and the 180 eld m's. I will be doing a little more research before getting that ball rolling.