Chamber dimensions to allow not cleaning

[HighUintas]

I'd like to know if there are some generally accepted clearances that allow a person to not clean their rifles barrel for a very long time and not encounter pressure issues from carbon buildup.

@Formidilosus , @Ryan Avery you're both advocates of not cleaning and you also like the hot 6UM, so would obviously know something about chamber design. Form, with your time around Tikkas, I'd think you would know something about chamber tolerances.

I have a 30-284 variant reamer that I designed. I'm considering having it reground to change a couple dimensions to allow not an cleaning and no pressure issues.

My loaded neck diameter is 0.3375-0.338 chamber reamer spec is 0.342, but would of course be cut slightly larger due to the reamer mfg tolerances. I have read that hotdog in a hallway clearance is fine for the neck.

Freebore diameter on reamer spec is 0.3085. Same thing applies to actual chamber cut dimension.

What clearances are needed in the neck and freebore without sacrificing much/any accuracy to allow very little or no cleaning?

 

[khuber84]

I'd suggest a 0.309 freebore diameter for starters, spec your chamber neck 0.005 over loaded case diameter. Get your reamer from jgs, as they hold dimensional tolerance extremely tight to your desired print specs. Beings that you're necking up brass, some shoulder material is now becoming neck material at the base the neck. Shoulder brass is generally thicker than neck, so now you have the potential for donuts, these will either need turned off(outside and/or inside as well) the other option is adding appropriate freebore to keep the base of the bullets bearing surface up above this "donut zone".

 

[HighUintas]

Good comments above,

But done anyone actually know what clearances are needed in the neck and throat to allow no cleaning?

I would think you 6UM guys would know since you designed it and like to not clean your guns.

 

[khuber84]

No cleaning isn't a thing in overbore magnums with dirty powder. That's like having an 800hp gasoline engine that is zero maintenance. My 24" 6saum is running N570 for similar velocities as the short barrel 6um. I had been shooting 63.6 N570 at 3330-3350fps, for bout 70 rounds. Last session that charge was running near 3400fps. Scoped it, and ugly carbon ring layering up in the freebore. Cleaned with clr/thoroclean, and within 4 rounds was back at 3340fps and all is good again.

I've ran N570 and RL33 in big 338s, 30s, 7s, 65s and now a 6mm. The one that tolerated it best was the 338 rum, which is the least overbore of all them so it makes sense.

 

[Formidilosus]

That's like having an 800hp gasoline engine that is zero maintenance. My 24" 6saum is running N570 for similar velocities as the short barrel 6um. I had been shooting 63.6 N570 at 3330-3350fps, for bout 70 rounds. Last session that charge was running near 3400fps. Scoped it, and ugly carbon ring layering up in the freebore. Cleaned with clr/thoroclean, and within 4 rounds was back at 3340fps and all is good again.

I’m at between 100 and 150 rounds of 6UM in this barrel, it sped up about 30fps at round 50’ish, and Ryan shot 700’ish through his first without ever touching the barrel. Not sure what he’s at on his new one, bet he hasn’t cleaned it.

Are you sure your MV increase (pressure) issue isn’t because of how you’re loading it?

 

[HighUintas]

I 100% agree. It doesn't seem like it should be a thing.

Apparently, it's a thing for Ryan and Form which is why I tagged them in the first post.

Form was saying that cleaning isn't needed for the 22cm. I can't see that working except for having certain tolerances.

I want to know. Because I don't want to clean.

 

[khuber84]

I’m at between 100 and 150 rounds of 6UM in this barrel, it sped up about 30fps at round 50’ish, and Ryan shot 700’ish through his first without ever touching the barrel. Not sure what he’s at on his new one, bet he hasn’t cleaned it.

Are you sure your MV increase (pressure) issue isn’t because of how you’re loading it?

I'm at 240 rounds on the barrel. After the 100 round break in, I played with H1000/Rl23 to the tune of 160 rounds total. I ran a pressure test with N570, rounds 160-176, had a good shooting load by round count 200ish, shot bout 40 of those and now it sped up. Same 8# lot of N570, same 115 nr dtac, same primers, same 25-40° temps. Stripped carbon ring out, ran 5 foulers and repeated 63.0 and 63.5 gr from the psi test and it was within 10fps of original test performed 75 rounds back.

It's a hawkhill, my 9th one? Only 3 have been magnum, other 6 match barrels of small case, but those were all stabilized by 200 rounds, the magnums have been around 120-150. My 65 Saum was stabilized with H1000 156s by count 120 and has been shooting that load very well. Cleaned at 200 and 275. No velocity creep, but I do it anyways.

The higher psi you run, the cleaner a powder typically burns, but your burning more powder/heat/psi. Carbon forms from the latter two even tho the rest the barrel appears to be cleaner.

 

[HighUintas]

That is pretty good evidence that cleaning makes a difference, at least for the chamber and cartridge you're shooting .

However, I wonder if you quit cleaning it long enough if it would stabilize or just continue to build pressure.

 

[khuber84]

As in a certain amount of build up happens, then it "self regulates" if you will? Some people believe supressor function that way, they don't ever clean them, and they just start blowing loose fouling out the end. I need to try it with my 22gt. It's been cleaned once at like 60 rounds, now I'm at 140 and it's speed up from 3130-3200 in this time frame, it shoots best 3150-3180, so I'll prep the next batch of brass and drop charge to 32.5gr and load up 200 more rounds and see how long it stays with a stable velocity. N1508 is pretty clean/cool burning so well see!

 

[Article 4]

Never having to clean a barrel is NOT a thing. Ever...period dot. (well I guess you can opt not to but its not good) Can you do things to limit cleaning yes, can you use materials that cause less friction and wear, yes. Those things also sacrifice accuracy over time and you will will have to clean it at some point.
The best shooters in the world clean after a certain number of shots. Personally, I clean after every session or at max 200 rounds, unless I am shooting a match where it is not possible to do so for a time, which is very rare.

Cleaning and fouling also helps me to ensure I am taking into account erosion, seating, and true barrel life by being able to see what is happening in all 3 areas from time to time.

 

[TaperPin]

Good post topic - I’m very curious about it all - look forward to seeing what everyone is doing.

Here’s a great borescope image of what happened in a Shilen 6.5 creed barrel with less than 100 rounds when bullets began hanging up on the fouling in a tight throat. The top photo is looking at the neck and throat - it’s a cool picture because it shows the end of the neck and smoothish throat before the rifling so well. The other photos are throat fouling that is scraping on bullets as they are chambered.

If I remember the guy’s story correctly, the rifle is shooting 5 shot groups .33 moa.

 

[Article 4]

As in a certain amount of build up happens, then it "self regulates" if you will? Some people believe supressor function that way, they don't ever clean them, and they just start blowing loose fouling out the end. I need to try it with my 22gt. It's been cleaned once at like 60 rounds, now I'm at 140 and it's speed up from 3130-3200 in this time frame, it shoots best 3150-3180, so I'll prep the next batch of brass and drop charge to 32.5gr and load up 200 more rounds and see how long it stays with a stable velocity. N1508 is pretty clean/cool burning so well see!

Question, do you feel like the increased FPS at 140 is a function of bbl break in or fouling?

 

[khuber84]

Question, do you feel like the increased FPS at 140 is a function of bbl break in or fouling?

I have found most barrels speed up 50-100fps within the first 150 rounds. Small case capacity to bore ratio chambers (223/6br/308) can/will take a bit longer, like 200. The recent Proof barrels I've had in last 4-5 years, were heavily lapped and usually take a bit longer, but should be all stabilized by 250-300. My older proofs were pretty normal. I feel this is attributed to a change in the bores condition, from smooth factory lapping, to that finish losing its smooth slick surface to a bit of resistance building more psi and creating more velocity. I have traditionally shot Hawkhill barrels the most, but have had a few Kreiger, Bartlein, Proof and Mullerworks in the mix.

 

[Formidilosus]

Never having to clean a barrel is NOT a thing. Ever...period dot. (well I guess you can opt not to but it’s not good) Can you do things to limit cleaning yes, can you use materials that cause less friction and wear, yes. Those things also sacrifice accuracy over time and you will will have to clean it at some point.

And you know this because you personally have shot out multiple barrels not cleaning ever, and multiple of the same barrels cleaning regularly side by side?

 

[Article 4]

I have found most barrels speed up 50-100fps within the first 150 rounds. Small case capacity to bore ratio chambers(223/6br/308) can/will take a bit longer, like 200. The recent Proof barrels I've had in last 4-5 years, were heavily lapped and usually take a bit longer, but should be all stabilized by 250-300. My older proofs were pretty normal.

Agree. I know PROOF bbls well. Probably too well. Agree that all well made bbls gain fps once breaking in is complete....cut rifle bbls usually take less break in than button - but metals can mean as much as process.

Cleaning helps the process and ensures that the consistency in velocity and accuracy continue - why many manufacturers have bbl break in procedures and as I say that, I HOPE I AM NOT opening a break in discussion at all....not really for this post

 

[khuber84]

Agree. I know PROOF bbls well. Probably too well. Agree that all well made bbls gain fps once breaking in is complete....cut rifle bbls usually take less break in than button - but metals can mean as much as process.

Cleaning helps the process and ensures that the consistency in velocity and accuracy continue - why many manufacturers have bbl break in procedures and as I say that, I HOPE I AM NOT opening a break in discussion at all....not really for this post

My normal method with a new barrel is clean at 50, 100, 200(load development is done by this time) then clean when accuracy/precision changes, which is usually accompanied with velocity changes.

One thing that may impact barrel fouling accumulated, is bore temps and rate of fire. My match rifles see 10-12 rounds in 120-90 seconds, 120-150 rounds in the day, and if it's summer I doubt the barrel temp gets below 100° after the second stage. My H4350 6gt load typically can make it through a 2 day match and sight-in, 250 rounds and not have velocity creep. 250 rounds from a hunting rifle, especially if the hunter has a practice rifle, may last them 5 years of shooting without cleaning.

 

[Article 4]

And you know this because you personally have shot out multiple barrels not cleaning ever, and multiple of the same barrels cleaning regularly side by side?

I have never run that test and not sure anyone has, happy to if you wanna supply the bbls and components. If you know of someone who has and has empirical data driven results, please send me a link. I always wanna learn

What I do know through my own experience of building rifles and having input on barrel making at the highest levels is:

• Fouling by definition is defined as "pollute" or "obstruct" or "become entangled or jammed"
• In high round count activities, rifles lose accuracy over time due to fouling - due to a multitude of reasons
• Fouling can change pressures and seating depths if allowed to become extreme

The question I always put out for people to judge on their own is - if cleaning a bbl does not harm and helps with long term bbl life and accuracy, why leave a bbl with fouling that could even possibly and potentially cause harm, effect accuracy, and affect bbl life?

 

[khuber84]

I will always perform maintenance cleaning, especially as using 3 clr patches and 1 thoroclean patch, followrd by 1 alcohol patch and a few eliminator patches, finally some dry patches to do all I need, takes 10-15 mins, and I can do 2-3, rifles at once in 30 mins or less.

However I'm gonna try not cleaning my 22gt and see how it behaves.

 

[Formidilosus]

I have never run that test and not sure anyone has, happy to if you wanna supply the bbls and components. If you know of someone who has and has empirical data driven results, please send me a link. I always wanna learn

So why state something as “fact”, that you e never even tried?

I and those I’m around have been shooting multiple barrels out a year for a decade without a single patch being run through them.

This rifle has never had anything but bullets in the bore-



Two 10 round groups back to back a couple months ago-


A zero check a couple of months before the two above; read the target carefully-


Here’s a Rokslider shooting it this past summer-





This rifle is also over 15,000 rounds without a single thing going through the barrel except bullets-



Here’s a Rokslider shooting it this past summer, he alone shot 450’ish rounds through it that week, I shot another 150’ish, and multiple other forum members shot another 100-150 rounds- that’s 700 to 750 rounds in a single week that 9-10 people, including one of the owners of this forum can account for-




10 round RTZ after dropping-




Another 10 round group-


If you prefer 3 shot groups-





Cont…

 

[Formidilosus]

Maybe 223 and 308’s are too forgiving…


6XC, sitting at near 900 rounds without ever being cleaned, and the largest 10 shot group it has fired is .92 MOA.



At 400’ish rounds-



Different load, but two back to back 10 round groups at 650 to 700 rounds-



Here’s a 5 round “group”, but each round having a different seating depth that varied from shortest to longest by .1 inch-






How about a 300rum improved. Not many rounds on it, a bit more than 500. Again- never cleaned


The last 3 and 5 round groups-





Gas gun- 3,000+/- rounds, not cleaning-











On, and on, and on. Lots of things that are “known”, are complete BS when actually tested. Are there some barrels that just need to be cleaned at intervals to maintain precision? I’m sure there are. However, I don’t even own a cleaning rod because it has been several dozen barrels since I cleaned one. Average barrel life is the same, or even slightly better than when I did clean.