Is N150 a throat torcher??

[762 ULTRAMAGA]

So I recently had a 6.5 GT take a 50 fps nose dive in the middle of a hunter match with 1600 rounds through it, measured .075 erosion to the lands.
I adjusted seating depth, increased the charge .5 grains and put a few hundred rounds through it before things really started going to shit. I was running 34 grains N150 with 142 smks, shocked I didn't see at least 3000 rounds. It was a Benchmark Sendero.

I'm running a Criterion 223 wylde for PRS, it's been a picky bastard from the beginning but shoots 75 vlds real good toucking the lands, loaded with 24.5 grains N150.
I'm getting ready for the finale Aug 23rd and my accuracy is starting to drop! I'm at 2200 rounds and the lands have eroded to the point that I can't seat into them with the bullet still in the short 223 neck..
WTF is going on? Thought I'd for sure get 4000 rounds from a 223..

Is N150 super hard on barrels?

 

[oldrifleman]

What speeds are you shooting these rounds ? If you shoot either much over 3000 fps you are going to start wearing out barrels

 

[diggler1833]

Interesting.

At first I thought you might be running some high pressures, but 24.5gr N150 isn't even close (that is my load with the 75gr ELD-M in my .223 Wylde barrel). I'm at ~33.5 with my 6GT and 105 Hybrid... so depending on the length of your load you might be running fairly high there. There is no free lunch with pressure X speed unfortunately.

I've heard some guys claim it is much dirtier, but I clean every 100-150 rounds usually and never have a problem. That isn't part of your question anyway.

I do know that some guy created a QL comparison chart that showed N150 as being a relatively cool burning powder as far as flame temp... but that is computer generated and not real data, so it has to be taken with a grain of salt.

Mostly, I've found N150 to be a perfect middle-of-the-road powder between Varget and H4350... so I'm tagging here for future reference as other dudes chime in. If I torch a barrel earlier than expected on it, I'll be sure to come back and update as well.

As of right now, I've switched to only buying VV powders due to price and performance.

 

[Fig]

I run on the slow end, and anecdotally I find that a charge of H4350 causes less wear than a similar speed with Varget. I always thought Varget was faster and higher test than H4350? This surprises me.

 

[memilanuk]

Is N150 super hard on barrels?

Unless they've changed something in the formulation in the past few years, no. Been using it since 2008 when Obama was in office and Varget/H4895 became unobtanium (the first time). Performance has always been on par with Varget for me, over 8-10 barrels of 223 and 308. I used others powders along the way (primarily Varget and H4895, some N140) but never noticed anything out of the ordinary - besides less fouling, in my opinion, than Varget.

I'd look elsewhere for something to blame. I'd say that even premium barrel makers occasionally put out one that is 'soft' - I had a Krieger that kept eroding the throat a crazy amount (with Varget and 185 Juggernauts)... but it still (mostly) shot well. Finally pitched it when I couldn't reach the lands without the bullet falling out of the case.

But if you're having the same issue across two barrels, different calibers... I'd look in the mirror and reconsider your cleaning methods, etc.

 

[762 ULTRAMAGA]

What speeds are you shooting these rounds ? If you shoot either much over 3000 fps you are going to start wearing out barrels

Running the 75 vld at 2990, just under the tactical limit for prs.
I was running 142 smks at 2700 in a 28" barrel.
I clean every 200 rounds with a bronze brush and a C4 soaked patch wrapped around it, and some Butches Bore Shine every 500 or so.
Just wondering if I'm somehow messing it up during cleaning..

 

[762 ULTRAMAGA]

Unless they've changed something in the formulation in the past few years, no. Been using it since 2008 when Obama was in office and Varget/H4895 became unobtanium (the first time). Performance has always been on par with Varget for me, over 8-10 barrels of 223 and 308. I used others powders along the way (primarily Varget and H4895, some N140) but never noticed anything out of the ordinary - besides less fouling, in my opinion, than Varget.

I'd look elsewhere for something to blame. I'd say that even premium barrel makers occasionally put out one that is 'soft' - I had a Krieger that kept eroding the throat a crazy amount (with Varget and 185 Juggernauts)... but it still (mostly) shot well. Finally pitched it when I couldn't reach the lands without the bullet falling out of the case.

But if you're having the same issue across two barrels, different calibers... I'd look in the mirror and reconsider your cleaning methods, etc.

Thanks
See above for my cleaning regiment, I use a bore guide too.
How many rounds do you average from 223 barrels?
I've heard that Benchmark is using some soft steel from more than a few shooters lately.
I guess Criterion being a cheap button barrel probably doesn't source great steel either..

 

[memilanuk]

How many rounds do you average from 223 barrels?

I usually pull match barrels preemptively @ 3k rds; not going to milk them to the bitter end.

I'm probably the odd one out here; I'm used to seeing 80-82s @ 2700-2800 for mid-range FTR. Pretty much nobody uses 223 for long range FTR if they don't have to. I know a lot of people here run them up to the speeds you're at, but in my mind that's pushing the pressure pretty high. If the throat suffers as a result, I'm not surprised.

 

[lash]

I run on the slow end, and anecdotally I find that a charge of H4350 causes less wear than a similar speed with Varget. I always thought Varget was faster and higher test than H4350? This surprises me.

I’m not sure that I’m reading your response correctly but yes, H4350 is a slower burn rate powder than Varget and all else being equal should show less wear than Varget.

 

[DeathBeforeDismount]

I run on the slow end, and anecdotally I find that a charge of H4350 causes less wear than a similar speed with Varget. I always thought Varget was faster and higher test than H4350? This surprises me.

Varget is a faster powder but I think it also burns hotter. It is more temp stable ( slightly) than H4350 as well.

I find H4350 to be a better all around powder. You also don't get carbon ring issues like you do with varget. Can run from little 6mm all the way up to 300wm at respectable speeds and very consistent es.

 

[JerkyFreak]

Well, flame temperature does play a role in throat erosion, but friction and compression heating during engraving probably plays a larger role. This is why shooting longer bearing surface bullets usually show more wear than shorter ones.

 

[diggler1833]

Running the 75 vld at 2990, just under the tactical limit for prs.
I was running 142 smks at 2700 in a 28" barrel.
I clean every 200 rounds with a bronze brush and a C4 soaked patch wrapped around it, and some Butches Bore Shine every 500 or so.
Just wondering if I'm somehow messing it up during cleaning..

Woah, 2,990 in your .223? Damn! My 26" Krieger is pushing the 75 ELD-M about 160 FPS slower than you on the same charge weight. Now I have to go and check my velocity results again .

ETA, Nope, about 170 FPS slower. I'm at 1.883 CBTO / 2.425 OAL.

 

[Dogtown]

N100 series shouldn't be a barrel burner - it's single base vs the double-base N500 series. I shoot a lot of N140, N160, and N170 for that very reason and am happy to trade the velocity for extended barrel life in some rigs.

 

[diggler1833]

N100 series shouldn't be a barrel burner - it's single base vs the double-base N500 series. I shoot a lot of N140, N160, and N170 for that very reason and am happy to trade the velocity for extended barrel life in some rigs.

Agreed. N100 series aren't for chasing velocity. They sure do shoot well in just about everything that I've tried (N133, N135, N150, N160). I'm going to shut up now before everyone switches and my supply dries up.

 

[762 ULTRAMAGA]

Woah, 2,990 in your .223? Damn! My 26" Krieger is pushing the 75 ELD-M about 160 FPS slower than you on the same charge weight. Now I have to go and check my velocity results again .

ETA, Nope, about 170 FPS slower. I'm at 1.883 CBTO / 2.425 OAL.

It's a 223 wylde chamber so I'm seating way over saami length, no pressure with that load, I've tested starline cases over and over getting 15 +loads with that combo.
Maybe I'll back it down even more on the next barrel and run 2900

 

[diggler1833]

It's a 223 wylde chamber so I'm seating way over saami length, no pressure with that load, I've tested starline cases over and over getting 15 +loads with that combo.
Maybe I'll back it down even more on the next barrel and run 2900

Yep, .223 Wylde. I'm also using Starline brass.

Different barrels run different speeds.

*****

@Rob01 I think you were looking at the possibility of speed with the .223 Wylde and N150 a few months ago, weren't you? This may be the ticket, and I just have a slow barrel.

 

[Rob01]

Yep, .223 Wylde. I'm also using Starline brass.

Different barrels run different speeds.

*****

@Rob01 I think you were looking at the possibility of speed with the .223 Wylde and N150 a few months ago, weren't you? This may be the ticket, and I just have a slow barrel.

I have good 223 Wylde loads but I think I was asking about the 6 ARC and N150.

 

[6brshooter]

75eldm@2998 with h4895 in lapua brass and 24" proof, 223 wylde chamber and seating long.

 

[762 ULTRAMAGA]

Yep, .223 Wylde. I'm also using Starline brass.

Different barrels run

Gotcha
Are you running the same charge of 24. 5 grains?
Where are you seeing pressure, seems super slow

 

[diggler1833]

Gotcha
Are you running the same charge of 24. 5 grains?
Where are you seeing pressure, seems super slow

Didn't see pressure there, that's just where it shoots best. By 24.8 things were opening up again.

You can certainly get into pressure sooner with Starline brass vs Lapua or LC though.

 

[Supersubes]

Well, flame temperature does play a role in throat erosion, but friction and compression heating during engraving probably plays a larger role. This is why shooting longer bearing surface bullets usually show more wear than shorter ones.

I think you have this wrong. The first evidence of throat wear shows up at the end of the chamber/beginning of the freebore. Within just a few rounds that begins to fire crack, and the bullet never touches that edge. That trend continues to the next most fragile part of the bore, which are the lands. Also, the thermal conductivity of copper is about 20 times greater than 416 stainless. If you rub them together, you should end up with a hot bullet and a warm barrel. Lastly, when the bullet is at its fastest and hottest near the muzzle, we see virtually no wear.

 

[JerkyFreak]

I had a whole essay typed up and then realised nobody's interested...

I think you have this wrong. The first evidence of throat wear shows up at the end of the chamber/beginning of the freebore. Within just a few rounds that begins to fire crack, and the bullet never touches that edge. That trend continues to the next most fragile part of the bore, which are the lands. Also, the thermal conductivity of copper is about 20 times greater than 416 stainless. If you rub them together, you should end up with a hot bullet and a warm barrel. Lastly, when the bullet is at its fastest and hottest near the muzzle, we see virtually no wear.

Fire-cracking does not advance the lands.

After the leade, when the lands are constant height, friction is minimal and the barrel wears very slowly.

On my rifles, bullet size=bore size; i.e. the bore also touches the bullet, just not very firmly.

My post specifically deals with throat erosion; i.e. advancing leade. In that area the bullet is swaged by the lands to conform to the shape of the bore. Also, at that area, due to the force required for engraving, the friction heating is very elevated and concentrated on the lands. Hence the much increased heat and wear on the lands.

Now, we differ as to which is more responsible for wear, heat from combustion or engraving. As the wear just after the leade is as minimal as the rest of the bore and the groove size does not increase appreciably, I do not think combustion heat is the main driver.

 

[Fig]

That doesn’t make any sense. While correct that the bullet engraved on the lands the throat is larger than the bullet, so no engraving or friction to speak of, hence the term “Fire Cracking”, and not Friction Cracking. If what you said was true it would start at the lands, and it doesn’t. I’m pretty sure it’s burning powder that heats the steel enough to cause fire cracking. There is certainly friction, but I think if our guns were air powered, instead of a chemical explosion, no fire cracking.

 

[Supersubes]

That doesn’t make any sense. While correct that the bullet engraved on the lands the throat is larger than the bullet, so no engraving or friction to speak of, hence the term “Fire Cracking”, and not Friction Cracking. If what you said was true it would start at the lands, and it doesn’t. I’m pretty sure it’s burning powder that heats the steel enough to cause fire cracking. There is certainly friction, but I think if our guns were air powered, instead of a chemical explosion, no fire cracking.

You beat me to it, that was going to be my analogy. To me the throat behaves exactly as you’d expect it to given the flame temps and pressures. There’s no getting away from throat features burning away despite very little contact with the bullet. If friction heating erosion were a thing, barrel wear would progress more slowly as the barrel aged, since the lands are rounding out and shortening, reducing friction.

 

[ma smith]

I do not think combustion heat is the main driver.

The mathematical models of barrel wear are highly sensitive to the powder's burn characteristics. a good example is .223 rem using 24.0gr varget has less than 3k of "projected" accurate barrel life. that's because varget burns very hot. you can extend the barrel life a significant amount using cooler burning powders.

To directly answer the OP, the burn rate on n150 is rather low, it has much better projected barrel life than standard Varget. The n150 powder is not a barrel burner on paper (in contrast to n540, for example). Also, a ø 6.5mm bore has a lot more powder capactity than a 6.0mm bore, so running 6.5 x GT should last alot longer than a 6.0 x GT, all other things equal.

When you combine the two, a 6mmGT running varget is modeled to burn out the barrel significantly faster than OP's setup. Since the OP is running into issues <2k rounds fired, he should be looking at other factors than the powder selection to explain his throat erosion/fire cracking (or whatever else is causing his speeds to degrade and be in consistent).

Just my $0.02

 

[762 ULTRAMAGA]

The mathematical models of barrel wear are highly sensitive to the powder's burn characteristics. a good example is .223 rem using 24.0gr varget has less than 3k of "projected" accurate barrel life. that's because varget burns very hot. you can extend the barrel life a significant amount using cooler burning powders.

To directly answer the OP, the burn rate on n150 is rather low, it has much better projected barrel life than standard Varget. The n150 powder is not a barrel burner on paper (in contrast to n540, for example). Also, a ø 6.5mm bore has a lot more powder capactity than a 6.0mm bore, so running 6.5 x GT should last alot longer than a 6.0 x GT, all other things equal.

When you combine the two, a 6mmGT running varget is modeled to burn out the barrel significantly faster than OP's setup. Since the OP is running into issues <2k rounds fired, he should be looking at other factors than the powder selection to explain his throat erosion/fire cracking (or whatever else is causing his speeds to degrade and be in consistent).

Just my $0.02

Good discussion all around

If N150 essentially has nearly the exact burn rate and potential energy of Varget wouldn't the two powders burn about equally hot?

For example my N150 loads produce almost the exact same velocities in both cartridges as equal charges with varget.
How would that be possible if the two powders had different burn characteristics?

Now if comparing H1000 to RL26 its pretty obvious one powder is releasing considerably more energy and heat.

 

[diggler1833]

The generated figures that I've seen had N150 as a fairly cool-burning powder, while Varget was near the opposite (hot) end. The accuracy of that generation is something that I cannot attest to though.

Length of bullet, pressure, powder charge weight, rate of fire, etc... are other factors that will affect barrel life.

I'm not smart enough to be able to figure any of it out. I've never generated any objective research of my own. I just regurgitate stuff from the guys who have (Litz et al.). Obviously there is something there as a .243 and a .308 have significantly different barrel lives with the only real difference being bore diameter.