Why is there no coatings used in rifle throats to slow erosion?

[theflyonthewall]

This is being posted in the 'smith section because I feel that there is definitely a more technical knowledge base in this section than in other places on LRH.

The question is:

Why are there no coatings being used in rifle throats to slow throat erosion? Ceramic coatings (to name just ONE) are used with success in many different applications from automotive engine parts like pistons, piston rings, combustion chambers, etc... as well as in the aerospace industries, foundry applications, etc..

Anyway, my point is that the technology and materials have been long proven in other industries and it would seem like a natural fit for barrel-burning calibers. But there has to be SOME reason that it's not used in barrel throats.

I first thought that maybe the exacting tolerances of a throat was the issue, but film thickness seems to be a very controllable aspect so one would be able to measure film thickness, then simply factor it in when cutting a throat------right?

Does anyone know why?

 

[Coyboy]

aplication would be near impossible, remember the reamer is only cutting out a small portion in the throat, coating just that portion to satisfy the film thickness issues would do very little to prevent erosion in the groove and lands just ahead of the reamer cut. so You may prevent erosion right where the bullet sits but what about .020" in front of it?

Afraid the best we have to date in Nitride treatment. And that has not been a popular option to date, I think popularity lacks a bit just do to the fact that many switch calibers or cartriges before they have worn there barrel out.

 

[theflyonthewall]

Please don't misunderstand my curiosity as I post this. I'm NOT arguing with you, just tossing out ideas for a healthy discussion...lol.....but:

I certainly would think that an application could be precisely controlled throughout the barrel, if that would be of benefit to eliminating the issue you described above.

There are some very precise instruments in use in the coating industries and it makes me wonder---if one can set the propellent pressure and control it precisely (which is routinely done), as well as control the feed rate of the material, which is also already done, then why couldn't one design a ball bearing apparatus that would allow a spray tip to move at a constant velocity THROUGH the bore from end to end thus giving an even and predictable film thickness throughout?

The way that I'm proposing to do this theoretical coating job wouldn't be such a far departure from how borescopes are used in industries now. One would just have to use a micro-spray tip and a precise setup to center it in the bore. Then, wouldn't it be akin to other highly precise operations that you amazing gunsmiths routinely do?


If you have some time to kill, would you mind explaining some of the nuances of Nitride treatment?

 

[lazylabs]

I have read quite a few threads on this with most of the applicaitons being vapor deposit methods as well as surface treatments. It seems that the coatings that work well for high temp tend to be fracture prone and then you have a rough barrel. The other side is you don't only have high temp/pressure gasses you have a very abrasive media blasting action with the powder. The vapor deposit method is also very expensive. They have been chrome lining barrels for quite a while but you just don't get the best accuracy out of them.

If you have to spend $500 to coat a $300 barrel is it really worth it?
You would have to do the coating before you even know if the gun will shoot.
The coating process will probably make any future problems yours and not the barrel maker. \

I do think that something could probably be found to significantly extend barrel life but even at double the round count it probably would not be cost effective. It would always be a niche market for the high volume shooters. The average guy(not LRH guy) might shoot out 1 or 2 barrels in a lifetime. It's one of those things where the manufactures could build themselves out of business.

COULD detroit build a car that last 15 years...... will they?

 

[Coyboy]

Well if your trying to coat the entire bore and chamber after cutting, than yes the operation could be much more feasable. Similar to the chrome linning in many military barrels. And I do prefer my AR barrels crome lined over a SS barrel. way less to no fouling and way less cleaning required.

I recall in the last 12 months a video report on a coating /treatment that was being tested in full auto ARs that was working really well. But I don't remember if that was an applied coating or the Nitriding process.

Which in easy terms is a type of salt bath applied with heat ( in the 900 degree range) That hardens the surface of the steel to somthing like 60+ Rockwell.

 

[shortgrass]

I recently built a rifle from components I had in stock for awhile in the shop. A 6mmXC. I "broke-in" the barrel, bore scoping throughout the process, until fouling subsided. Took 55 rds. I throughly cleaned it and scoped it again. Seemed like the "corners" at the throat/lead had 'rounded over' , a bit. I set the barrel back 1/2 a turn and re-set the head space, then fired two more rounds, cleaned and inspected. Looked good, so I sent it to Tru-Tech for Meonite/Nitride processing. Took about 5 weeks, no big deal. Now, for the test of time and round count. I haven't had time to shoot it, yet! I decided to try the Melonite/Nitride because several bench shooters I know have used the process and say "there's no effect on accuracy and I get at least 1/2 again as many rounds down the tube before accuracy begins to fall off as I usually do with a barrel that hasn't been Nitride treated". If it effected accuracy, these guys (bench rest shooters) wouldn't even think about using the process and they do shoot barrels to "high round count" (every round fired is recorded in their note book). It looks promising, to me. And, the rifle will make a good display model along with my others, this next Feruary, at the OKC Backwoods Expo.

 

[Coyboy]

I recently built a rifle from components I had in stock for awhile in the shop. A 6mmXC. I "broke-in" the barrel, bore scoping throughout the process, until fouling subsided. Took 55 rds. I throughly cleaned it and scoped it again. Seemed like the "corners" at the throat/lead had 'rounded over' , a bit. I set the barrel back 1/2 a turn and re-set the head space, then fired two more rounds, cleaned and inspected. Looked good, so I sent it to Tru-Tech for Meonite/Nitride processing. Took about 5 weeks, no big deal. Now, for the test of time and round count. I haven't had time to shoot it, yet! I decided to try the Melonite/Nitride because several bench shooters I know have used the process and say "there's no effect on accuracy and I get at least 1/2 again as many rounds down the tube before accuracy begins to fall off as I usually do with a barrel that hasn't been Nitride treated". If it effected accuracy, these guys (bench rest shooters) wouldn't even think about using the process and they do shoot barrels to "high round count" (every round fired is recorded in their note book). It looks promising, to me. And, the rifle will make a good display model along with my others, this next Feruary, at the OKC Backwoods Expo.

Let us know how this works out for you.

 

[theflyonthewall]

Some very good points guys!

It would seem that some coatings can be successfully applied, but is the bigger question possibly in finding the RIGHT coating?

I know it has to be a pretty brutal environment with not only tremendous heat and pressure, but also the friction from burning and unburnt powder blasting away at the surfaces.

Kinda makes me wonder if anyone out there is trying to coat a throat or barrel with diamond dust? Sounds crazy at first, but they're using it in sharpening "stones", for coating certain tooling etc. So maybe that could be an option worth looking into?

'guess I need to research how they apply diamond dust to things......

 

[hatfield954]

aplication would be near impossible, remember the reamer is only cutting out a small portion in the throat, coating just that portion to satisfy the film thickness issues would do very little to prevent erosion in the groove and lands just ahead of the reamer cut. so You may prevent erosion right where the bullet sits but what about .020" in front of it?

Afraid the best we have to date in Nitride treatment. And that has not been a popular option to date, I think popularity lacks a bit just do to the fact that many switch calibers or cartriges before they have worn there barrel out.

Cowboy, I know nothing about barrel prep procedures but. What if they were to cut the throat deeper (on purpose) and then build it back up to tolerance with a coating that is being talked about. The same step for the groove and lands. That would seem feasable wouldn't it? Cost would probably be through the roof but that could be part of a custom build instead of a factory app.

 

[royinidaho]

This is a good thread.

My explanation of the OP's question is that when it is wanted bad enough someone will make it happen.

Desire will have to be big enough to overcome the blood, sweat and tear tuition.

 

[theflyonthewall]

Exactly roy!

I'm the type of guy that I think a lot of the membership here is--see a problem, find a way to fix it.

This seems like a feat that is so full of difficulty that isn't worth pursuing at first, but the same can be said for the distances that we now shoot game animals too. Once upon a time, you were considered a great shot if you could routinely hit what you were aiming at out to 300 yards. Now 300 is a total chip shot to most under normal conditions.

I just hate the idea of investing so much time and money into the most amazing cartridges that we now have access to, only to know going in that the barrel is going to be "shot out" with less than 1000 rounds in some cases. No one is going to "stop" throat erosion entirely with the technology that we now have. But if we could slow it down considerably, we could all play with our expensive rifles a little longer before having to reinvest all over again in the form of a new barrel.

Here's some light reading for anyone interested:

http://www.riflebarrels.com/articles/barrel_life1.pdf



and a video on salt-bath nitriding featuring Joel Kendrick:



As was stated before, the salt-bath nitriding seems to be the best solution at the present time and fortunately for us end-users, it's in no way a new procedure. Apparently the idea struck defense departments sometime shortly after WWII. So there has been a lot of time to perfect it as a barrel treatment.

 

[elkaholic]

I asked this question in another thread and was directed over here. I talked to Joel Kendrick today, who supposedly is the best known melonite applicator, and he says he can turn a barrel around in a week. He has been using the melonite process for about 6 years in his own barrels for competition. I also talked to Krieger barrels, and Mike told me that he thought it was a good idea providing the guy doing the work really knew his stuff. He said the temp is very critical and very near the point of taking the temper out of a barrel. When done correctly, he says there are no down sides........Rich

 

[theflyonthewall]

Thanks for stopping by here and giving us your input, elkoholic!

 

[BountyHunter]

Joel has done two barrels for me and so far they are working very well. One is my 338 Lapua AI and the other is a 300 WSM 1k BR gun.

I worked the loads out again for the 338 with the new Hornady 285 from the old 300 SMKs and it is just as accurate if not more.

The WSM has not worked the loads down to be consistent .3 or better at 500 plus where it needs to be. That will be done this winter and spring.

BH