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Discussion Starter · #1 ·
So third trip to the range with the USP CT .45 and third broken o-ring. This time it broke as soon as I got to the range in front of two friends who were anxious to test out the pistol. I racked the slide back to clear it before loading up and it was already broken. No idea how it broke. It was a new ring, well lubricated, and clean gun.

I didn't have any rings left so I went ahead and let my friends shoot without the o-ring for about an hour without any problems. Well except one of them had an accidental discharge as decocking and blew a hole in the table at the indoor range. But that's a story for another day and all I can do about that is sigh at this point.

The other two o-rings broke on me when removing the barrel for cleaning. They like to snag up on the slide and break even when I'm being extra careful.

To solve this problem I ordered 20 identical Viton O-rings from McMaster-Carr for the grand total of $17.02.
 

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Field strip the gun. Then run your pinky finger along the inside of the muzzle area of the slide.

You are looking for a burr which was not removed by the factory.

A burr on the inside of the slide will chew up the O-rings fairly quickly. I have a friend who purchased a slightly used tac40 because the original owner got sick of replacing o-rings every other box of ammo. First thing my friend did was polish that area and the o-rings never broke again.
 

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Don't use your finger. A burr too small to feel with your finger is still big enough to eat an o-ring. Use a cotton ball and run it around inside and out. A burr will snag the cotton right now and be sure to go in both directions as well as parallel with the barrel and slide. There is a burr there and do it on the barrel groove also. With any luck you did not throw up a bunch of burrs shooting it without the o-ring which is very likely to happen. If you do have burrs polish it well with Crocus cloth and only polish until you remove the burr. You only want to remove the burrs, not any metal.
I've yet to damage an o-ring so something for certain is wrong. If you have to send it to HK and let them fix it.
 

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I agree with BB. I have shot in excess of 5K rounds between my Tac45, Expert40 and CT45 and have never replaced an O-ring so far. Not a lot of rounds for three guns but it illustrates that there is an issue with your slide that I believe HK has to look at. That's what they are there for.
 

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Man I love this forum! New HK things to learn everyday!

It makes me happy to know things like this because now I can pass the info along to someone who might need it.

Good luck with your USP CT. :)
 

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Discussion Starter · #7 ·
Yes thanks for all the help. I never would have found the o-ring size to bulk order them without this forum. I am planning to look for the burrs when the new rings come in and will let everyone know what I find.

How long does it usually take HK to repair an issue like this? I'd hate to be without the CT for very long.
 

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I'm guessing you could remove minor burrs yourself using some fine grit sandpaper or a small file. Anything major though I would send the pistol to HK.
 

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Dear God do NOT use anything like sandpaper or a file, not in the name of all things holy!
Anything more coarse than Crocus cloth and you are going to make matters worse, and even might ruin something.
Put down the file, put down the sand paper, and step away from the gun.
Get the Crocus cloth or send it to HK for repair.
 

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Dear God do NOT use anything like sandpaper or a file, not in the name of all things holy!
Anything more coarse than Crocus cloth and you are going to make matters worse, and even might ruin something.
Put down the file, put down the sand paper, and step away from the gun.
Get the Crocus cloth or send it to HK for repair.
+1

All you want to do, is polish the surphaces, not grind them down. A rough surphace will be worse for the O-rings than burs would be.

ETA

If you sent it into HK for repair, it may take a couple weeks... Mabey 1 or 2... Its a very easy fix, especially for them, so it might only take a day for them to work on it, but it depends on how busy they are, and when they get around to it. The shipping will be the killer, to overnight it to and from the factory!
 

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Dear God do NOT use anything like sandpaper or a file, not in the name of all things holy!
Anything more coarse than Crocus cloth and you are going to make matters worse, and even might ruin something.
Put down the file, put down the sand paper, and step away from the gun.
Get the Crocus cloth or send it to HK for repair.
Really? So the tolerences are that tight? In that case I would definatly just send the gun back to HK.
 

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It is not so much that the tolerances are so tight but rather anything more coarse than Crocus cloth is going to raise more burrs, not eliminate them. Plus, a file and sand paper is going to remove the HE finish (it is more than just a surface finish but you are going to remove more than just the surface when you attack with a file and/or sand paper) and now you set up a condition likely to rust and the part will need re-finishing rather than what at first only required a light buffing.
 

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I hope H&K 4 Life is talking about a gunsmith file, not a machinist's file. I use one to remove the sharp edge off of the o-ring groove, after machining. And as far as sandpaper goes, I polish trigger parts on the USP all the time with it. Not your 26G I use in the welding field, but 400G on up to 2000G. Next comes a buffing pad. Like used on fine shoes and pipes for smoking, on a bench grinder and Flitz polishing paste. Looks like blue toothpaste. You think HK can install a Match trigger and get the most out of it. Ha, I've torn into the factory match triggers on the production guns. They are still a production gun. None of the rub area's are polished.

Be Safe
Gayle
 

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Oh, and who says you can't have a Match trigger on a Compact?

To take this topic way off topic... Compact with factory barrel with Match sites, Match Trigger group and Match O-ring on barrel. Now I'm working on destroying a Match weight assembly to work with a compact and a Jarvis barrel. Have a Jarvis threaded barrel for "quite time" already and love it, after I ringed it.

Why, because this is the USA and I can! Waste of money, yeah, but it is fun...




Be Safe
Gayle
 

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This is all very interesting and useful information. I was impling that you could possibly use a very fine file to just remove the burrs carefully if the burrs were very minor. It hadn't occured to me that you could remove the HE coating, that was a total oversight on my part. And of course producing more burrs than you get rid of is not a good thing at all.

I'm not a gunsmith (maybe someday with some training, hopefully) but I am a gun-tech for paintball markers/airsoft and I see things like burrs all the time and O-rings are what a paintball marker is mostly comprised of. Normally, you would carefully remove any present burrs and re-install a new and greased oring. I am beginning to realize that while firearms and paint markers are similar in many ways they also have alot of differences as well. For instance, no HE coating to be mindful of on paintball marker parts.

All I can say is, thank god for HK-Pro and it's fine and helpful members!
 

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Discussion Starter · #16 ·
Just a quick update.

The o-rings arrived today from McMaster-Carr and they are perfect. Even better then the ones that came with the pistol because they are solid black instead of whatever color that came with it (red?). I racked the slide about 50 times and they seem to be holding up so I'm not going to fool with filing anything just yet.

FYI, the product number for the rings are 9263-K112 and their website is http://www.mcmaster.com/

After shipping they were almost exactly $1 each. I also put one on the threads to keep the thread protector from coming loose and it seems to be doing the job.
 

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Just a quick update.

The o-rings arrived today from McMaster-Carr and they are perfect. Even better then the ones that came with the pistol because they are solid black instead of whatever color that came with it (red?). I racked the slide about 50 times and they seem to be holding up so I'm not going to fool with filing anything just yet.

FYI, the product number for the rings are 9263-K112 and their website is http://www.mcmaster.com/

After shipping they were almost exactly $1 each. I also put one on the threads to keep the thread protector from coming loose and it seems to be doing the job.
Wow, that is terrific, I'm tucking this part number into my cases tonight!!! I still have all my original orings and all the original "spares" that HK provides.

I think the advice of crocus cloth is right on the money; you gotta realize that no matter what type of file you use the whole point behind the oring is to increase accuracy by settling the slide to exact center each time every time we are talking 3 thousandths if i remember right ... you cannot measure such things by sight or by hand unless you are very very very practiced perhaps (by the way practice that crap on glocks okay? :-} :-} :-} ). The points on the HE finish are all totally true. So, if the crocus cloth doesnt just debur the bur, send it to HK and allow them the time to do it right.

Now, I would not want to derail this thread but I'm publicly proposing that gemarsh start a thread with pics and procedures step-by-step on the trigger polishing techniques!!! A "Trigger Polishing 101"! Cheers.
 

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O rings

+1 for Mcmaster.com, if you have trouble finding them look up Viton o-rings, they are 1mm wide, 14 mm ID for the 45's. 12 mm ID for 40's.
 

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When you type in the order number leave out the dash and just enter the string of numbers. $8.51 for a pack of 10.
I have been buying my o-rings from allorings.com, another good vender of Viton 75D o-rings. It has been so long since I ordered (and have yet to use one) I don't recall the prices but I do recall that you had to e-mail them the size you want since they did not list it on their site. I hope they have changed that now but a quick looks shows it still looks mostly the same. The site you listed is much easier to find and order what you want but allorings has done very well by me in the past.

Also, for the TP there is no need to use the expensive Viton 75 D rings. A standard 3/8 ID 1/16 CS ring will work just as well for holding on the TP. Since you have to remove it each time for cleaning you are almost certain to break it in two or three outings so make the TP o-ring as cheap as you can get.
 
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