Meloniting barrel/throat erosion thread

[steve123]

What kind of throat erosion are you getting and how is the accuracy of your rifle at what round count?

Please include barrel brand, whether stainless or chrome moly, twist rate, whether button rifled or cut rifling, length, cartridge and "load specifics", velocity, etc. Also include what company did the meloniting.

Share any comments about the subject you wish.

The run down on mine.

I shoot a stainless 26" Schneider 5P in 6x47L with a 7.5 twist. It is a button rifled barrel. MMI trutec did the Meloniting. The load I use with H-4831SC is sending 115DTACS at 2990 fps currently. The load has slowed down some. It was going 3015 fps or so when I first worked it up.

How I measure. I'm using a dummy cartridge with the neck turned enough so the case will grip the bullet with sufficient force so as to hold the bullet but not let it stick in the lands. I also use the same bullet every time. It's not a perfect system but when repeated a half dozen times I can get pretty good measurements.

Rounds down the barrel.

300 rounds =.0005"-.001"

600 ###### =.001"-.002"

950 ###### =.004"-.005"

1350 ###### =.006"-.007"

1750 ###### =.016"-.017" The last 100Y group I shot was .4".

 

[turbo54]

Re: Meloniting barrel/throat erosion thread

http://www.snipershide.com/forum/ubbthreads.php?ubb=showflat&Number=3466558#Post3466558

Copy/paste of that post:

So my 284 just wasn't shooting. Sent the barrel in for inspection and I'm told the throat is fire-cracked and hurt bad.

284 win Short action .088" Freebore = 162amax on lands at 2.955" COAL

I put 45 rounds through, cleaning every couple shots for the first 5-10 rounds, then cleaned at 25, then at 45, then sent it off for nitride.

Never did group so well.

Ignorantly, I sent 500 rounds downrange chasing loads. Occasionally it would group. Never fired more than 5-6 rounds in a row without letting the barrel cool. I was using mainly H4350, but tried a bit of H4831 and RE17. Mainly ran 162amax between 2800-2900, 175smk between 2700-2800 and 180smk between 2650-2750. I ran ladders to establish max loads, and got pressure signs a few times including ejector marks, and a soot ring around the primer once or twice.

Anyway, nitrided barrel is "throat-fucked" in 550 rounds with a non barrel burning cartridge.

 

[steve123]

Re: Meloniting barrel/throat erosion thread

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: turbo54</div><div class="ubbcode-body">http://www.snipershide.com/forum/ubbthreads.php?ubb=showflat&Number=3466558#Post3466558

Copy/paste of that post:

So my 284 just wasn't shooting. Sent the barrel in for inspection and I'm told the throat is fire-cracked and hurt bad.

284 win Short action .088" Freebore = 162amax on lands at 2.955" COAL

I put 45 rounds through, cleaning every couple shots for the first 5-10 rounds, then cleaned at 25, then at 45, then sent it off for nitride.

Never did group so well.

Ignorantly, I sent 500 rounds downrange chasing loads. Occasionally it would group. Never fired more than 5-6 rounds in a row without letting the barrel cool. I was using mainly H4350, but tried a bit of H4831 and RE17. Mainly ran 162amax between 2800-2900, 175smk between 2700-2800 and 180smk between 2650-2750. I ran ladders to establish max loads, and got pressure signs a few times including ejector marks, and a soot ring around the primer once or twice.

Anyway, nitrided barrel is "throat-fucked" in 550 rounds with a non barrel burning cartridge. </div></div>

Geez, sorry to see you having such a bad experience.

I went through a equally frustrating experience like that one time. Turned out the barrel had gradually come loose. I actually read a thread here on the Hide which gave a clue about the problem, went out to the safe grabbed the barrel and cracked it loose with my bare hands, LOL. I shot 500 rounds, bought a new scope and new rings during the whole process.

It does seem like you got a bad barrel to begin with or possibly ruined in the heat treat???

 

[turbo54]

Re: Meloniting barrel/throat erosion thread

In hindsight, I never should have sent the barrel off for nitride. In my 45 rounds of pre-melonite shooting, I had 4 different "middle of the road" loadings. All would put several shots together, but drop other shots out of the group. I attributed this to not having developed a real load yet, and because of the fairly frequent cleaning.

Other high end barrels I've had experience with simply shoot ANY consistent load pretty well. Sure, they'll hammer with "the" load, but they don't suck with anything. Mine did.

Bad barrel out of the gate? Seems likely to me.

Why is it shot out with 550 (549 actually)? No idea.

You've piqued my curiosity though about the hand-tight barrel causing troubles. Care to elaborate? Maybe post it in my thread so as not to derail this one.

 

[steve123]

Re: Meloniting barrel/throat erosion thread

Will do

 

[steve123]

Re: Meloniting barrel/throat erosion thread

Post your meloniting experience here please guys.

 

[Bill Larson]

Re: Meloniting barrel/throat erosion thread

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: turbo54</div><div class="ubbcode-body">In hindsight, I never should have sent the barrel off for nitride. In my 45 rounds of pre-melonite shooting, I had 4 different "middle of the road" loadings. All would put several shots together, but drop other shots out of the group. I attributed this to not having developed a real load yet, and because of the fairly frequent cleaning.

Other high end barrels I've had experience with simply shoot ANY consistent load pretty well. Sure, they'll hammer with "the" load, but they don't suck with anything. Mine did.

Bad barrel out of the gate? Seems likely to me.

Why is it shot out with 550 (549 actually)? No idea.

You've piqued my curiosity though about the hand-tight barrel causing troubles. Care to elaborate? Maybe post it in my thread so as not to derail this one. </div></div>
I`ve never nitrided.... but have had throats go in 400 rnds.I say bad steel...2 of my buddies have had loose barrels.I torque mine at 150ft/lbs. and never had that problem.
bill larson

 

[Oddball Six]

Re: Meloniting barrel/throat erosion thread

If you look at doing this to your action along with your barrel, be careful that you check with your action manufacturer for the impact on warranty.

Surgeon, for example, shared an explicit no-go when I was going to do this on my RSR, because of the potential to weaken the receiver if the salt bath meloniting method were executed incorrectly.

As a result, some manufacturers may say "no, that voids the warranty all of the time".

Some may say "you can only do it through X provider who we have verified their process".

Its worth asking the question or looking for that Manufacturer's position - no matter what component you are considering putting through the process.

 

[leadbullet]

Re: Meloniting barrel/throat erosion thread

30 inch Benchmark barrel, SS 1-7.5 twist 3 groove in 243 AI
Load was
115 berger at 3150 with H4831 SC
95 SMK at 3320 with lots of H4831 SC

after 440 rds it had 3.5 inches of fire cracked throat, barrel and was seriously fouling and after 17 rds accuracy went from .3 MOA to 3+MOA. It now needs constant cleaning, On a non melonited barrel I could have set it back but not this one. $800 in the trash after less than 500 rds, this was my F open class rifles and it wont finish one relay in a match.
Fuck meloniting, never again.
PLZ do not ask me how I really feel.

 

[RedGoat]

Re: Meloniting barrel/throat erosion thread

So is meloniting hit or miss. I've heard some great reports and I've heard some horror stories.

What is the culprit?
- bad barrel???
- bad break-in/prep???
- bad nitriding process???

I was planning on nitriding my up coming 243 barrel, but now I'm not sure. My current nitrided .308 has shot great and never needs cleaning - around 700 rounds since last cleaning and put 5 shots into a 1.8" group @ 600y few weekends ago.

 

[turbo54]

Re: Meloniting barrel/throat erosion thread

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: RedGoat</div><div class="ubbcode-body">So is meloniting hit or miss. I've heard some great reports and I've heard some horror stories.

What is the culprit?
- bad barrel???
- bad break-in/prep???
- bad nitriding process???

I was planning on nitriding my up coming 243 barrel, but now I'm not sure. My current nitrided .308 has shot great and never needs cleaning - around 700 rounds since last cleaning and put 5 shots into a 1.8" group @ 600y few weekends ago. </div></div>

In the case of my ruined CBI 308 barrel, it was due to either:

1. Nitride processing error
2. Nitriding fucks button rifled barrels

My CBI barrel was an absolute hammer. It would stack shots at 200 yards. Any sierra or Hornady on top of any consistent charge of Varget. I ran 200-250 rounds through, cleaned meticulously and sent it out. I cleaned meticulously when it came back, and is now a 2moa barrel. FML

 

[steve123]

Re: Meloniting barrel/throat erosion thread

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: attherange</div><div class="ubbcode-body">30 inch Benchmark barrel, SS 1-7.5 twist 3 groove in 243 AI
Load was
115 berger at 3150 with H4831 SC
95 SMK at 3320 with lots of H4831 SC

after 440 rds it had 3.5 inches of fire cracked throat, barrel and was seriously fouling and after 17 rds accuracy went from .3 MOA to 3+MOA. It now needs constant cleaning, On a non melonited barrel I could have set it back but not this one. $800 in the trash after less than 500 rds, this was my F open class rifles and it wont finish one relay in a match.
Fuck meloniting, never again.
PLZ do not ask me how I really feel. </div></div>

Who did your Meloniting?

 

[leadbullet]

Re: Meloniting barrel/throat erosion thread

don't remember, Benchmark barrel sent it out to their guy.

 

[A10XRIFLE]

Re: Meloniting barrel/throat erosion thread

The Team has been messing with the 6.5 SAUM. were pushing the 140's at 3080 with H1000. Mild load about 56,000 PSI. Currently my rifle has 1400 rounds on it and the throat has moved .030" Im jumping the 140 hybrids .050 now and still shooting in the .3's

My team mate wanted to try Salt Bath Nitriding from MMI and so I sent his barrel to them after shooting 5 break in rounds. He has 1800 rounds on his and he reports no degrading accuracy and good velocity. In fact he just shot the 24 hr challenge and made 100% first round hits out to 1200. I need to get the throat distance from the lands at max length and that will let me compare to the rifle I have.

I also have a second barrel for mine that is also salt Nitrided and will compare it directly to the one ive got now when it pukes.

Barrels are both Bartlien Cut Rifled Gain Twists with a 1-9.5 to 1-8.5 twist over 28"

 

[Rockfish Dave]

Re: Meloniting barrel/throat erosion thread

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: turbo54</div><div class="ubbcode-body">
IMy CBI barrel was an absolute hammer. It would stack shots at 200 yards. Any sierra or Hornady on top of any consistent charge of Varget. I ran 200-250 rounds through, cleaned meticulously and sent it out. I cleaned meticulously when it came back, and is now a 2moa barrel. FML
</div></div>

I'm too tired to look up the sources so I'm going from memory, which can be wrong, so take the following with a grain of salt.

In your example I have to wonder why such a high round count before sending it in. The companies I contacted (MMI, Burlington Engineering and H&M) all have said send barrels with a low round count.

By the time yours was sent in there most likely was fire cracking. My understanding of throat erosion is that it is a combination of fire cracking and the resulting carbon infusion from the burnt powder with the metal creating a more brittle section at the throat. I have read that it turns it into a metal with similar properties to cast iron. The brittle, tree bark like, surface easily erodes. Add to that the nitride case hardening treatment and it seems like a recipe for disaster.

Since the Melonite process creates a case hardened surface by a thermochemical diffusion process whereby nitrogen-bearing salts generate a controlled release of nitrogen at the interface of a ferrous part, the slightly differnt composition of your barrel due to the relatively high round count (200) vs what is recommended 15-30(ish, and a maximum of no more than 60) may be the cause of your frustration.

All this said, I'm not a metallurgist so it is just my thoughts.

 

[turbo54]

Re: Meloniting barrel/throat erosion thread

Dave, when I performed my due diligence research, I was told to nitride PRIOR to throat erosion.

It was mutually agreed that ~200 rounds in a 308 was no problem, as 308 throats last so long.

 

[Rockfish Dave]

Re: Meloniting barrel/throat erosion thread

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: turbo54</div><div class="ubbcode-body">
It was mutually agreed that ~200 rounds in a 308 was no problem, as 308 throats last so long. </div></div>

Well, then I'm at a loss. That was my best guess. I wonder why the discrepancy? I'll follow up with them the next time I'm in contact with the previously mentioned companies just for my own piece of mind.

 

[RedGoat]

Re: Meloniting barrel/throat erosion thread

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Turbo54</div><div class="ubbcode-body">
2. Nitriding fucks button rifled barrels</div></div>

This

I have been told by Mark @ SAC that nitiriding on button rifled barrels is not recommended.

 

[steve123]

Re: Meloniting barrel/throat erosion thread

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: steve123</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: attherange</div><div class="ubbcode-body">30 inch Benchmark barrel, SS 1-7.5 twist 3 groove in 243 AI
Load was
115 berger at 3150 with H4831 SC
95 SMK at 3320 with lots of H4831 SC

after 440 rds it had 3.5 inches of fire cracked throat, barrel and was seriously fouling and after 17 rds accuracy went from .3 MOA to 3+MOA. It now needs constant cleaning, On a non melonited barrel I could have set it back but not this one. $800 in the trash after less than 500 rds, this was my F open class rifles and it wont finish one relay in a match.
Fuck meloniting, never again.
PLZ do not ask me how I really feel. </div></div>

Who did your Meloniting? </div></div>

Button rifled or cut rifling?

 

[turbo54]

Re: Meloniting barrel/throat erosion thread

Benchmark =cut rifling

My other fucked barrel was cut rifled though, plus, I had way fewer rounds through it...as in 45.

I can't say FOR SURE the nitriding was the cause though, as it wasn't grouping so great during the "breakin".

 

[steve123]

Re: Meloniting barrel/throat erosion thread

I wonder if a tool similar to the one in the link below would solve some problems associated with pre break in by fire lapping prior to meloniting. It polishes out the burrs at the end of the throat caused by the reamer cut as well as the interior surface of the barrel and eliminates the need to fire any rounds.

http://www.brownells.com/.aspx/pid=647/Product/SHOTGUN-BARREL-POLISHING-FLEX-HONE-reg-

I had the opportunity to watch my gunsmith throat my 30-375 for 240 SMK's. Throating was a separate operation from chambering in this case. After he was done throating he used the fine grit honing tool to polish out the burrs. It looked like the one in the link except appropriately sized for the job. He attached it to a cleaning rod and ran it from breach to bore only. He used a bore scope periodically during the process to check progress. The polishing lasted for 15 minutes or there abouts. This particular barrel later prooved capable of incredible accuracy so I was always impressed with the gunsmiths job.

I tried googling a smaller caliber version like my gunsmith used but I couldn't find one. Maybe someone with more internet skills can find it or knows about it.

A different gunsmith polished the throat on my 6x47 barrel then sent it for Melonite so a shot was never fired before hand.

 

[A10XRIFLE]

Re: Meloniting barrel/throat erosion thread

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: turbo54</div><div class="ubbcode-body">Benchmark =cut rifling</div></div>


Actually most of their barrels are buttoned. I have heard that they can cut rifle but generally speaking they are a button rifle company. Their Rimfire barrels are stellar

 

[leadbullet]

Re: Meloniting barrel/throat erosion thread

I have 4 Benchmark barrels and they all shoot lights out, my problem is with meloniting, if something goes wrong with the barrel, there is absolutely nothing you can do to fix it. In my case, I would have cut it down and rechambered in 6MM BR or 6XC but nooo instead I am stuck with this fouling Mother f*#$*^.

 

[Ring]

Re: Meloniting barrel/throat erosion thread

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: RedGoat</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Turbo54</div><div class="ubbcode-body">
2. Nitriding fucks button rifled barrels</div></div>

This

I have been told by Mark @ SAC that nitiriding on button rifled barrels is not recommended. </div></div>

BS....

DS Arms (most ZM4 models and ZM4 uppers)
Barrett
SIG
FN
LWRC
POF-USA
S&W M&P15
CMMG - LE Series with WASP treatment
AAC
Adams Arms (uppers)
Huldra Arms (rifles and uppers with chrome-moly barrels {not stainless})
Bushmaster ACR
Spikes Tactical
Beretta
KRISS
Robinson arms
Sig - 550-556
Superior Barrels with "hard blue" (uppers and barrels) {http://www.superiorbarrels.com/}
and many more...

OEM's nitride there button barrels, no issues...

i have done 5 savage's, 3 shillens, 2 CBI, and i few others... only barrel i ever F'ed was a BCM chrome lined that killed the chrome...

 

[steve123]

Well guys my melonited 6x47L barrel is done. 3200 rounds through it. Bullets started smoking about 20-30Y out from the muzzle a few months ago, nursed it along with a different bullet and thought I was okay till today. So it looks like I got about double the round count compared to my last regular barrel which bit the dust at 1500 rounds.

I'll measure the throat erosion and post here later in the week.