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Old 03-07-2018, 11:36 AM   #1
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Default Severe Barrel galling and chipped barrel on Polish CHF

Hi guys,

I pressed a new Polish CHF barrel and the barrel pin hole was slightly egged so with the barrel still in place, I drilled and reamed out to .303 for an over sized barrel pin. I pressed the barrel pin and then populated the barrel.

A month later, I came back pressed out the barrel pin and pressed out the barrel. The barrel did not press out smoothly and when it finally came out the barrel had some severe galling and it shipped the breach face of the barrel.

Is this salvageable?

Thanks

Mike













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Old 03-07-2018, 11:41 AM   #2
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The galling is fine, just smooth the rough edges over with a file or emery cloth.. how the hell did you manage to take that notch out of the end?

Next time be sure the interference fit is correct and use anti-sieze.
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Old 03-07-2018, 11:52 AM   #3
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Anti seize is your friend.... damn.
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Old 03-07-2018, 11:56 AM   #4
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Why remove the barrel a month later?
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Old 03-07-2018, 12:01 PM   #5
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Quote:
Originally Posted by def90 View Post
how the hell did you manage to take that notch out of the end?

Next time be sure the interference fit is correct and use anti-sieze.

That's exactly what I was wondering. It's looks like as I was pressing out the barrel, it bulldozed to the breach face and the pressure cleaved out that ship. I felt it pop at the end as it pressed out of the trunnion
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Old 03-07-2018, 12:02 PM   #6
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Originally Posted by Stickee8 View Post
Why remove the barrel a month later?
Because I got busy and left it sitting there until I had time to come back to it. I needed to remove the barrel from the trunnion so I could rivet the trunnion into the receiver.
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Old 03-07-2018, 12:49 PM   #7
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What did you use to push the barrel out? It appears you may have used something without a brass pad, such as the Rforbus barrel push out tool.

As the others said check your tolerances before installing. I believe you only need .001" interference. I quality caliper will let you get a fairly accurate reading of the inner and outer diameters without having to buy an ID and OT mic. Although for anyone who does any amount of AK building or ameteur machine, it is a good investment.

I like to use sandpaper and maybe a round file and knock off any rough edges and high spots down.

I also like to install the barrel after the trunnion is already in the receiver.....
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Old 03-07-2018, 01:10 PM   #8
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Quote:
Originally Posted by Mkupka View Post
Because I got busy and left it sitting there until I had time to come back to it. I needed to remove the barrel from the trunnion so I could rivet the trunnion into the receiver.
Why do people do this?
Because they sell populated kits that way and its somehow assumed that’s how one builds a rifle?

Last edited by Mr Nobody; 03-07-2018 at 01:34 PM.
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Old 03-07-2018, 01:20 PM   #9
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Oh the joy of backward engineering.
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Old 03-07-2018, 01:34 PM   #10
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I have a MAK-90 that has similar markings on top of the barrel hood like yours (no doubt from a lack of anti-seize at some point previous in its life, too), and it is has been a great shooter for years.
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Old 03-07-2018, 02:16 PM   #11
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Quote:
Originally Posted by adam6955 View Post
What did you use to push the barrel out? It appears you may have used something without a brass pad, such as the Rforbus barrel push out tool.
AKBuilder barrel push tool with brass pad.
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Old 03-07-2018, 02:53 PM   #12
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dammit man- i would've cried if a chunk sheared off an expensive bbl like that.


you didn't happen to get one of the *oversized* bbls by mistake did you ?

https://armsofamerica.com/polishfbra...achbarrel.aspx
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Old 03-07-2018, 04:28 PM   #13
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dammit man- i would've cried if a chunk sheared off an expensive bbl like that.

you didn't happen to get one of the *oversized* bbls by mistake did you ?

https://armsofamerica.com/polishfbra...achbarrel.aspx
No, just a standard CHF Radom barrel. I bought 2 of them on the black Friday sale for $139 each. Yeah I got a pit in my stomach when I saw it.
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Old 03-07-2018, 06:46 PM   #14
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in the future if you insist on populating a barrel before riveting in the trunnion...
you can press the barrel out about 3-4mm then get in there and take a needle file and take the leading edge off the barrel pin slot in the barrel and top front edge off the barrel pin hole in the trunnion.
then blow it out good or use a q-tip to get the filing dust out, a little lube.
should press out w/out galling.
if you dont think it deformed the chamber at all i think youre gtg.
IF you reinstall the barrel in the same loaction and your headspace seems tight maybe it pinched the top down a little? i doubt it but some of the REALLY bad yugos were a little deformed. but they were way worse than that.
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Old 03-07-2018, 06:58 PM   #15
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Quote:
Originally Posted by BR7.62 View Post
in the future if you insist on populating a barrel before riveting in the trunnion...
you can press the barrel out about 3-4mm then get in there and take a needle file and take the leading edge off the barrel pin slot in the barrel and top front edge off the barrel pin hole in the trunnion.
then blow it out good or use a q-tip to get the filing dust out, a little lube.
should press out w/out galling.
if you dont think it deformed the chamber at all i think youre gtg.
IF you reinstall the barrel in the same loaction and your headspace seems tight maybe it pinched the top down a little? i doubt it but some of the REALLY bad yugos were a little deformed. but they were way worse than that.
Yes, that or an end scraper.

The galling was not caused by surface slip - it was caused by a burr at the block forward edge of the original pin hole contacting a new burr at the rear edge of the new pin hole of the barrel. All the Never-Seez (poor choice, by the way) in the world would not have prevented that.
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Old 03-07-2018, 07:36 PM   #16
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Why is the "Never-Seez " a poor choice and what do you recommend?
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Old 03-07-2018, 07:53 PM   #17
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Great pictures by the way. Thanks for documenting your trials and tribulations for us to see and learn from.
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Old 03-07-2018, 08:12 PM   #18
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First Rivet trunnion in receiver,
Than press in barrel.

Doing it since 1975 with no issues
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Old 03-07-2018, 08:32 PM   #19
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SILLY OP!
everyone knows this why the superglue barrel method now is the standard in AK builds.
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Old 03-07-2018, 09:35 PM   #20
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The AK builder nut has a relief to fit the extractor doesn't it? I wonder if you had it mis-aligned which nosed the barrel down, making it drag the top across the barrel pin hole edge. I can't believe how deep that is. Useable? I dunno. How much material is necessary to withstand chamber pressure? Maybe it just looks worse in pics than in real life?
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Old 03-07-2018, 10:05 PM   #21
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Quote:
Originally Posted by 10acresandrocks View Post
Why is the "Never-Seez " a poor choice and what do you recommend?
Never-Seez and the like are colloidal formulations of petroleum vehicle with graphite flakes mixed with either copper and/or or zinc. These are designed to prevent metal-to-metal contact by the sliding of the suspended graphite flakes over each other, and the metallic particulate "plating" the harder parts under pressure.

Graphite may seem slippery, but the flakes are super-hard and quite abrasive to metals. Now, the flakes do slide very easily across each other (not across the metal) and often seem to be "lubrication".

In essence, Never-Seez, et al has a measurable "thickness" of application. It does slow the formation of rust (the petroleum) and stays in place for high heat applications. It is wonderful when used on steam system bolting, plastic extrusion bolting and other high-torque high-heat applications. It is a very poor lubricant since that is not its intended purpose.

What do I recommend? Correct sizing, deburring, and just a light coat of thin machine oil - such as 10-weight are all that is needed for press-fitted parts. I use just a drop of Sili Kroil since there is always a can on the workbench. I guess it helps a wee bit, and evaporates quickly. Really, simple light oil such as 3-in-One is fine or any 10W to 90W oil used for automotive or farm.

Like I said - Never-Seez is great when used appropriately and a real life-saver for certain types of joints. Like just about any other good thing though, it is not a fix for everything - kind of like duck tape.
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Old 03-07-2018, 11:00 PM   #22
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I do not drill for barrel pin until trunnion is riveted in receiver so things like this don't happen.
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Old 03-07-2018, 11:24 PM   #23
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There is never seize formulated for press fits.
It's not the same stuff you use on nuts and bolts.

As stated above correct fit and a debured edge will prevent this.

I have never used the never seize for press fits I just know it exists.

Never seize can be a PITA to get off and out of areas and can raise hell with your finish.
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Old 03-07-2018, 11:50 PM   #24
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Quote:
Originally Posted by adam6955 View Post
As the others said check your tolerances before installing. I believe you only need .001" interference. I quality caliper will let you get a fairly accurate reading of the inner and outer diameters without having to buy an ID and OT mic. Although for anyone who does any amount of AK building or ameteur machine, it is a good investment.

.....
A quality caliper will not be a high enough level of precision to measure a correct amount of press fit. A micrometer and telescoping gauges are much better tools for the job. I'm sure lots of guys do get by with calipers on their builds, but then again lots of guys like the OP post up their fubars from lack of experience or lack of proper tools.

Your barrel should be ok to use as is. Tons of pulled Yugo barrels are that bad or worse being used on modern builds.
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Old 03-08-2018, 12:20 AM   #25
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Quote:
Originally Posted by BR7.62 View Post
in the future if you insist on populating a barrel before riveting in the trunnion...
you can press the barrel out about 3-4mm then get in there and take a needle file and take the leading edge off the barrel pin slot in the barrel and top front edge off the barrel pin hole in the trunnion.
then blow it out good or use a q-tip to get the filing dust out, a little lube.
should press out w/out galling
.
This^^ This^^ This ^^
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Old 03-08-2018, 02:02 AM   #26
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Originally Posted by gvguns View Post
A quality caliper will not be a high enough level of precision to measure a correct amount of press fit. A micrometer and telescoping gauges are much better tools for the job. I'm sure lots of guys do get by with calipers on their builds, but then again lots of guys like the OP post up their fubars from lack of experience or lack of proper tools.

Your barrel should be ok to use as is. Tons of pulled Yugo barrels are that bad or worse being used on modern builds.
Well of course better will be better, but a good quality caliper is better than nothing. And as long as it is good enough to hold to .001" accuracy, it will be "close enough" to get the job done for installations where .001" one way or another is not a deal breaker.

I have engine building instruments that are accurate to the .0001", or even .00005" in the case of my ID bore gauge set. I have yet to bust it out, as it has not been needed to get where I need to be to ensure a build goes together as it should.

I am not advocating being "cheap" or an attitude of "plastiguage is as good as mics" mentality (PM me for the story behind that discussion ), but keep in mind that 90% of hobbyists are already spending a ton on tools. A tool that can reasonably suit multiple purposes (inner and outer diameter measuring with .001" accuracy) will get said 90% by in 99% of situations.
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Last edited by adam6955; 03-08-2018 at 02:14 AM.
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Old 03-08-2018, 03:01 PM   #27
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Quote:
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Quote:
Originally Posted by BR7.62 View Post
in the future if you insist on populating a barrel before riveting in the trunnion...
you can press the barrel out about 3-4mm then get in there and take a needle file and take the leading edge off the barrel pin slot in the barrel and top front edge off the barrel pin hole in the trunnion.
then blow it out good or use a q-tip to get the filing dust out, a little lube.
should press out w/out galling.


This^^ This^^ This ^^
This is clearly what I should have done. This was my 5th build and the first time I have had this occur. I may well switch to riveting the trunnions into the receiver before pressing the barrel.
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Old 03-13-2018, 05:52 AM   #28
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thats why they make the trunnion support tool. thats just cosmetic. it sucks though.
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Old 03-13-2018, 11:52 AM   #29
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This is clearly what I should have done. This was my 5th build and the first time I have had this occur. I may well switch to riveting the trunnions into the receiver before pressing the barrel.


For me, I find it much easier to start with installing the barrel into the trunnion, head space, drill pin hole then populate the barrel first rather than riveting the trunnion into the receiver then pressing the barrel. That has always been my method since I started building.

You just got to remember that when pressing the barrel out of the trunnion after drilling the barrel pin, use a needle file to take the leading edge off the barrel pin slot in the barrel and top front edge off the barrel pin hole in the trunnion, then blow out the shavings then LUBE, then proceed to press out. Works all the time for me.
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Old 03-13-2018, 12:27 PM   #30
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I went that way on my first few. Then I realized it is far easier to work around the receiver while pressing the barrel and drilling the pin than it is to press the barrel out and try to get it head spaced correctly the second time.

To all their own I guess, but everyone should try it both ways.
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