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Smooth Chambers

25 Feb 2017
@ 08:30 pm (GMT)

Mike Neeson

Hi, hopefully I'm not turning over old ground here, but I was lead to believe - schooled in fact - by my gunsmith, that the case needs to be totally free of all traces of lube so that it grips the wall of the chamber on firing. He explained that if the case did not grip, the bolt face could experience more thrust than desirable. Now I know that lube in the chamber is bad - particularly in the regard of causing bulges, but the below modelling by an engineer(?) seems to demonstrate that the smoother the case and chamber, the better. Leading to reduced thrust on the bolt and better case life. Have a read and see what you think. I'd be interested to hear everyone's thoughts.
http://www.varmintal.com/a243zold.htm

Replies

26 Feb 2017
@ 05:53 am (GMT)

Bryan Webster

Re: Smooth Chambers
Clean, smooth chamber (no oil or cleaning solvent in there)

Proper care to getting the correct headspace of resized brass which is the biggest issue with case head bulges and separation.

Clean brass

The above should do it for you.
27 Feb 2017
@ 10:50 pm (GMT)

mark whiteley

Re: Smooth Chambers
I think there has to be a balance there some where but I'm not exactly sure what it is
I do know a bloke who lubed his cases to fire form them better and blew his blaser up nearly taking his head off, blaser's dont blow up well
I also know of a bloke who used windex window cleaner to clean his barrel without using something to protect the steel afterward, the cases would not eject and had to be forced out with a cleaning rod
also the savage 22 rimfire rifles had a bad habit of not extracting cases until the chamber's were polished
I think the above comment is right "a clean smooth chamber and clean cases"
regards Mark
28 Feb 2017
@ 03:07 am (GMT)

Bryan Webster

Re: Smooth Chambers
For sure Mark. I always have used a single paatch to oil the barrel before putting it away, and a dry one not too tight before shooting. I know Nathan uses a bit of CRC LongLife and shoots over that, but we have no access to that here locally in Canada that I have seen, and I do not take chances.

When out for a stone's sheep or elk hunt in the mountains for a week to ten days or so, I run a a pull-through with a lightly oiled patch of a light oil like Remoil through the bore and have shot over that. It gives some comfort if the barrel is stainless too.
28 Feb 2017
@ 09:23 am (GMT)

Martin Taylor

Re: Smooth Chambers
Hahaaaa, Blazers do make expensive hand grenades, very, very over rated........

That's a lot of reading Mike.
Have always been told smooth, clean chambers are the go, though l am guilty of not cleaning %100 of the sizing wax of my cases when F/L sizing.......food for thought!

I also shoot over a lightly oiled bore (lightly oiled patch) and haven't found any PIO changes. Testing this extensively with the 300wm & 308w, first round, cold bore hits at extended range. These are the field conditions they are set up for in our High Country, though admittedly at gongs/targets due to other factors at the moment, gggrrrrrr!

01 Mar 2017
@ 01:22 am (GMT)

Paul Leverman

Re: Smooth Chambers
Good read, nice graphics. The individual certainly has time to kill as I am sure this has been researched and experimented with since maybe day two of the history of brass case cartridges. This is good information, and very usable and everyone should know it. Just looking through a couple of owner's manuals and reloading manuals, I don't see it. While this may not be a dangerous situation for a new rifle owner with factory ammo, it will definitely be harmful to the rifle. Lug set back is the primary concern, where any deformation in squareness along the axial line will affect your accuracy. Basically, you bend your bolt.

In the beginning of the article the author tells of how a shooter had to knock the cases out of the chamber. Been there done that. While the chamber looked fine, it was in fact not fine at all. A rough chamber is exactly like bedding your action. If you put lots of relief holes and angles and ridges in your stock, the bedding stays where it is. If your chamber is rough and the brass is forced into the scratches and voids, it stays there.

Thanks for posting this Mike.

Bryan - you can get the CRC at Lordco. You have to special order it and they will bring it in overnight from Vancouver. You have to give them their number: 73262. Get two cans at a time, it's easier.
01 Mar 2017
@ 01:39 am (GMT)

Paul Leverman

Re: Smooth Chambers
Sorry, I got confused as usual. Had three articles up on the same subject and mixed them up in the void above my neck. It was Mark that related the knocking out of the cases.
01 Mar 2017
@ 08:39 am (GMT)

Nathan Foster

Re: Smooth Chambers
The timing of this is of interest to me. Of late I have been involved in a handful of technical discussions. In each instance, the person asking questions has gone too far, losing sight of basic physics and becoming totally confused by their own data.

Yes, there is a balance to be had. For example, if you do not have some form of light lube in a blued chamber and bore, the rifle will likely rust in coastal conditions over a period of hours. Fortunately, a rifle chamber is not generally finished with grit. It is cut with for want of a better term, a fine tooth file. Many of you will know that one of my core areas of expertize is surface finishing. If you read my accurizing book, you will see that I researched the effects of bore finish very heavily. I was able to use this time to help True-Flite develop their barrels while also increasing my own learning so that I could then pass it on to you. As I wrote in the book, a high finish in the bore could prove disastrous. Yet this was not the same as using a small amount of light lube. I am actually just in the process of editing a video showing how a light lube can be put to very good use on a test rifle.

I would urge you all to exercise some common sense with this. I see far too many people fall down holes and go off for tea with mad hatters. The PDF does not take into account the military chrome lined bore. In this instance, the chamber and bore must be resistant to corrosion, fouling and severe heat. The PDF does not take case body taper or case to bore ratio into account. The PDF uses a computer model as opposed to a rifle that has its chamber polished progressively until the case or action blows apart. The author instead puts forth possibilities which may be useful. But for the end user, I fear this only creates confusion.

And again this ties back to my recent discussions on a range of matters. Somehow there exists a dimension at the upper levels of learning that I can only describe as stupid. The PDF may offer useful information but we need to exercise common sense.

So how do we end up here. In Mikes case, he is trying to find out why the chamber on one of his rifles has been giving sticky extraction of late. I would hazard a guess that your smith ran fairly low RPM to make the cut, so the finish is not too smooth unless he pulled a trick after reaming. It may be a chamber problem but it might not be.

The bore could have become extra smooth over time (bore finish problem as I wrote about in Accurizing). This could effect the coefficient of friction. If the bore is producing zero fouling, the key factor may be to avoid cleaning for some time. Note also that the finish is not directly the problem but instead, the finish in relationship to the internal dimensions (specifically first 3 to 6"). The bore could theoretically be lapped a touch more to correct this- even though lapping would at this stage appear to be the enemy.

This is a very tricky problem to diagnose and not something that can be done via these forums. I know we have been over many factors via email and have exhausted this method (i.e me taking wild guesses) of diagnosis. The above comment may however offer further insight. I can see why you avoided mentioning your specific problem here as it can open a can of "it could be" worms. Best to not (ed) open this up for for further discussion.
01 Mar 2017
@ 03:35 pm (GMT)

Mike Neeson

Re: Smooth Chambers
Thanks for all the replies, and as usual Nathan, very sage advice. I happened over this article on the Aus Reloading and trade group on facebook quite by accident. I wasn't looking for remedies. My sticky extraction is due to high pressure caused by a tight neck - very little clearance and in a word "finnicky". It appears any small amount of carbon or crap stops a clean release of the bullet, spiking pressure. Relations have broken down with the smith so I am left with the chamber as is and now have to deal with it. I will neck turn the brass a little for more clearance and NOT use factory ADI ammo as their brass is thick and dangerous in my rifle. This article for me showed how having good, really clean and smooth brass is of benefit and may help in my situation - NO LUBE FOR ME, my problem is pressure and a "competition" cut chamber. My friend and I are building a cheap rotary tumbler and I will give the steel pins a go in brass cleanup. It's not what I wanted, but life is about learning and I shall press on. Next new barrel I'm buying a Manson reamer myself, so that I know what I'm getting.
01 Mar 2017
@ 04:31 pm (GMT)

Grant Lovelock

Re: Smooth Chambers
Mike does your fired brass show any circumferencial marks on the body? This is most likely cause of sticky extraction.... as a matter of course when we chamber barrels we use "wet n dry" on a stick to polish the chamber and remove any machining marks... finished with 800 grit wet n dry. As one could imagine with the pressures exerted on the soft brass when fired this will inevitably force the brass against the wall of the chamber.... if any circumferencial marks are left in the chamber these are transferred onto the brass.... This in turn make the job of popping the brass out of the chamber much harder. If this is the case, pulling the barrel and having the chamber "polished" is advantageous.
FYI when I clean barrels after firing I finish with a light coating of KG Gun oil in the bore and chamber..... then I shoot over this....
01 Mar 2017
@ 11:32 pm (GMT)

Mike Neeson

Re: Smooth Chambers
Remington 700 SPS Tactical 308W
21" True Flite Barrel 1/11" twist
3mm freebore when loaded to COAL of 71mm

Hi Grant, thanks for your input. I might as well share my story. I have checked the chamber with a cheap endoscope and it looks to me to be smooth. at least nothing to cause major extraction issues. You can see the primer has flowed so much as to leave an impression of the extractor at 6 oclock. (Bore photos best viewed in small window as only 640x480 pixels)






This problem as built up over time... approx 200 rnds. I tried backing off the loads a couple of grains with no effect on pressure. I am guessing that this is due to 1. Tight "competition" chamber, 2. using a bore guide religiously when cleaning (chamber neck would not have got enough attention) and carbon buildup 3. And well... I don't know
Fired brass is hardly changed by running through a Redding body die and the shoulder doesn't even get set back with the die wound down onto the shell holder.
When I pass a projectile through the neck of fired brass, brass fired early in the piece lets the bullet pass though reasonably easy but with very little play. As you go through more recent fired brass, the necks get more restrictive and pressure signs increase dramatically. Which leads me to believe a tiny amount of carbon is enough to make a huge change with such tight tolerances. The photos of the chamber are post cleaning the neck but still had pressure signs.
I bought some ADI factory ammunition and almost had to have it removed by a gunsmith post firing. Turns out the ADI brass is somewhat thicker than Lap and Fed and bullet would not enter the fired neck. I have measured the OD of the fired brass and they measure at about .340 - I measured quite a few times and got readings of between .338 and .340
Soo, I have to have this sorted out by beginning of May for a planned hunt and am short on both time and money. My plan consists of neck turning my brass down a dash... maybe 1 or 2 thou, making sure my brass is immaculate and neck sizing with Lee collet and finishing with Redding body die. Nathan recommended getting the chamber recut, but the smith hasn't replied to my email and to be honest, time isn't on my side. As I said before, later in the year I may buy a reamer and get it redone somewhere else.
I'm sharing this mainly to show how important it is to understand what you want when talking to a gunsmith and that communication is key so that you're both on the same page.
If anyone has anything helpful to add or point out my errors I'll gladly listen
02 Mar 2017
@ 08:03 am (GMT)

Bob Mavin

Re: Smooth Chambers
Hi Mike
Doese the bolt close easily on a loaded round?
Bob
02 Mar 2017
@ 08:37 am (GMT)

Thomas Kitchen

Re: Smooth Chambers
HI Mike first of thank you for sharing we can all learn a lot from issues rather then success.

Sounds like getting it re reamed with a standard 308 reamer is simple solution as you know, most smith's should have one.

I did wonder if one of the small base sizing dies might help, as someone I know found one helpful when sizing military brass for a 223 tikka.

Have you tried any winchester brass? I find its about the thinnest
02 Mar 2017
@ 10:06 am (GMT)

Martin Taylor

Re: Smooth Chambers
You have a lot going on there Mike but as you say if the chamber is cut with a tight tolerance "match" reamer then yes a tight neck may be the culprit. Giving you your over pressure issues that you have experienced.
The smith who cut it should have advised you that this reamer has X sized neck. Then you could decide to use it and turn or go for more of a sammi spec.

The Redding body die not bumping the shoulder is of concern, they are good with their tolerances! Not sure what to make of that.

And yes that ADI 308 brass is bloody heavy, seems to be averaging around 1 grain less than our Lapua brass loads though we have only just started testing it.
02 Mar 2017
@ 12:02 pm (GMT)

Mike Neeson

Re: Smooth Chambers
Hi Bob, full length sized and factory rounds chamber fine, once fired neck sized rounds not so much. The body of the chamber is such that fired brass requires very little sizing and in other words, very little wiggle room. Thanks Thomas, yes I think that's the way I'll have to go later in the year when time and funds allow. Getting a new chamber reamed now, getting a load worked up and sorted before May would be tough, the range I have access to is problematic in trying to match shift work and designated practice days. Martin I don't think the Redding die is at fault, Nathan seems to think the chamber may have been "short cut". On further investigation, the die does contact the shoulder but there is not enough travel to reset it... I guess is matches it perfectly... a little too perfect.
Can I ask one more question in regards to getting the chamber reamed again, Is this easily done? Are there any problems associated with this kind of procedure due to it already being reamed? Will the barrel have to be set back at all? Sorry that's more than one question but I'd like to go into this eyes wide open. Thanks again guys
02 Mar 2017
@ 01:49 pm (GMT)

Martin Taylor

Re: Smooth Chambers
Yes sounds like a fair assumption Nathan has made Mike!

Recutting a chamber is something to discuss with the individual Smith, some wont use their reamers in a fired barrel others will. Most would want to set back the barrel a little, good question for Grant!

On the upside, you should be able to sort a load quickly given the cal choice, stick with your 71mm, lap brass, 210 primer & 06h.



On a side note,
I'm looking at possibly going with 6.5X47 lap for my TF barrel sitting in the safe, Trentech in Brisy has 3 reamers to choose from so discussing your needs it is a must!
Even my original cal the 260 he also has 2 to choose from.
02 Mar 2017
@ 02:07 pm (GMT)

mark whiteley

Re: Smooth Chambers
Mike a few things

firstly you need to try a small base body die or file the bottom of the redding die to reduce the case shoulder when used, if this is the problem

measure the fired case bodies against a reamer print for your chamber to get rid of any assumptions

try win brass

check for donuts

when ordering a reamer make a dummy to your specs and get the reamer maker (your choice) to copy to your specifications,
"live pilot" "no neck turn" "tighter than sloppy unknown sammi spec" ect
if you are going to use sammi specs just buy a factory rifle

match reamers are very good for accuracy and does not mean trouble,

going by your fired case neck measurement a 14-15 thou neck would probably be what you would want, but try win brass first

to re-chamber with your existing chamber is not hard to get done at all
you may loose around an inch of barrel but do it before you get to many rounds down the barrel

good luck with it
regards Mark




03 Mar 2017
@ 03:10 pm (GMT)

Mike Neeson

Re: Smooth Chambers
Thanks Martin and Mark, gave Lee from Trentech a call and had a good conversion with him. He says the neck sounds like a "minimum spec no turn" neck and should be about .341" - that's the maximum neck diameter he uses for 30 cal. He's gave me similar advice to Nathan, get a 338 cal brush to clean the neck of the chamber and also advised to have loaded rounds no greater than .337, slightly less would be better. My loaded rounds, Lap brass and 168 AMAX come out at .338 so a light skim will probably do it. If that doesn't help, he's happy to have a look at it for me so that's reassuring. I don't have a gunshop nearby so Winchester brass may have to wait a little. I'll keep you guys posted on how it all goes.
03 Mar 2017
@ 04:46 pm (GMT)

Martin Taylor

Re: Smooth Chambers
Great to hear Mike, with the Lap brass I've found very little run out in 3 separate batches of std 308 so a light skim should be quick & easy.

Another side note, I did turn some just out of interest but had no effect on accuracy in our 2 factory 308's, Tikka or Rem, both are inside .5 moa consistently.

Lee has chambered & fitted some very nice rigs for guys down here both LR comp/hunting and is well respected. l will be sending up my action & TF barrel when the time is right for trueing and fit.

03 Mar 2017
@ 07:30 pm (GMT)

Bob Mavin

Re: Smooth Chambers
I've had primers a lot flater than that. I looks like your firing pin might have a weak spring or worn hole, getting blow back around the pin. I had to get the pin hole sleaved to take away the slop in one of my falling block rifles
03 Mar 2017
@ 11:24 pm (GMT)

Mike Neeson

Re: Smooth Chambers
Yeah? well I had primers so flat once the Missus now serves her scones on them! Hahaha I'm not really looking at the firing pin flow, the flow at about 5:30 to 6 o'clock has the edge of the ejector imprinted in it. It's a little hard to see in the photo. This amount of flow was unusual and different to the first 100 rounds or so. I'll clean the chamber neck properly, not use the bore guide so religiously, turn the brass, make sure it's real clean and see how it goes.
24 Mar 2017
@ 06:01 pm (GMT)

Mike Neeson

Re: Smooth Chambers
Update and findings. I'll try to keep it short.

1. Built rotary wet tumbler, bought stainless pins and got all the brass very clean.


2. Resized necks with lee collet die and FL sized with Redding body die.
3. Trimmed to length and chamfered
4. Ran them all through the sizing mandrel for the K&M neck turning tool.
5. Turned necks to 14 thousands. - Noted quite a variation in neck thickness, necks had very little runout on the outside but quite wobbly from the internal.

6. Tumbled again to get rid of all the sizing wax, inside and out.
7. Neck sized again on collet die and then checked them all in a Lyman case gauge. Noted some passed and some failed - shoulder not reset, also noted these case were difficult to chamber.
8. Broke out the DMT sharpner (320 mesh) and honed the face of the body die - only managed to polish out the tooling marks, no great change in length. Honed the shell holder down - much easier - about 2 thou - just until it showed enough shoulder bump to pass in the Lyman gauge

All cases now chamber easily and this reflects by the "pass" in the Lyman gauge. Now to fireform...
Looks like a number of different things were contributing to my problem. will see how things go at the range.
24 Mar 2017
@ 06:03 pm (GMT)

Mike Neeson

Re: Smooth Chambers
Sorry there were pics but the google links don't seem to work.
24 Mar 2017
@ 07:21 pm (GMT)

Mike Neeson

Re: Smooth Chambers


24 Mar 2017
@ 11:01 pm (GMT)

mark whiteley

Re: Smooth Chambers
well done

regards Mark
25 Mar 2017
@ 09:18 am (GMT)

Martin Taylor

Re: Smooth Chambers
Here's to perseverance Mike, sounds like multiple culprits as you suggest!

You wouldn't be using a Lee shell holder by any chance?

 

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