O-Ring In The Primer Pocket

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Anyone have good success with placing an o-ring in the primer pocket of a 209 breech plug? My Triumph has almost no blow back in the bp area, but my Pursuit XLT has more than I like to see.

Would you recommend doing this? What size ring? Would a rubber material be better or would a metal washer work? Any info. would be helpful!
 
There are some people doing this, I have a custom BP for my Huntsman NEF and its designed for this. You might not be able to close your gun without taken out some medal for the oring you could just try I have a size 60 oring from lowes in mine. It lasts about 20-30 shots.
 
'O' ring

Viton is a material O rings are made out of to with stand Hightemps. Its a silicon material and it will last longer. Available at industrial supply houses. Its a little more expensive. You will probably have to have them order that size for you or you can go on line and probably find some you can order. The color is useally a light orangish red
Wayles
 
I have been using an "o"-ring under the primer in my family of Knight DISC rifles since the beginning of last Summer. I am getting zero blowback and the "o"-rings last for 40-50 shots for me. I do get a very slight amount of leakage from the primer on the bolt face as the primer is now containing all of the pressure.
 
jsteurrys
It might be a good idea to check the size of your touch hole if you are getting that much pressure on the primer. :roll:
 
jsteurrys
Could you please post a part # for the o-ring you are using?
Thanks, Art
 
Lee 9 said:
jsteurrys
It might be a good idea to check the size of your touch hole if you are getting that much pressure on the primer. :roll:

It is .032". The primer cup pushes back into the firing pin hole which is quite large on a Knight. The primers are still intact and have never seperated. They extract easily also.
 
BuckDoeHunter said:
Anyone have good success with placing an o-ring in the primer pocket of a 209 breech plug? My Triumph has almost no blow back in the bp area where my Pursuit XLT has more than I like to see.

Would you recommend doing this? What size ring? Would a rubber material be better or would a metal washer work? Any info. would be helpful!

BuckDoeHunter,

Never heard of such a thing, what is an o-ring? :wink:

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Seriously, I have been doing this for a couple years in a few of my custom and customized factory breech plugs. This was due to the fact that I don't like blowback and am always looking for a "better mousetrap". With the introduction of Blackhorn 209 powder, I wanted to be able to use this powder in my favorite rifle, a NEF Huntsman. I have tested this powder in my Knights, Whites, H&R, NEF, and others T/C's and CVA's. What I found out right away, was that this was not going to work reliably in my standard factory NEF breech plug, or the PR .25 ACP conversion breech plug, even with Small Rifle Magnum Primers. So I had to either find a plug that would shoot it reliably, or find one that I could modify to work 100%.

25 acp breech plug.
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The first custom plug I tested was the Hubbard plug. It worked well, but I was still left with blowback. This plug headspaces off the rim of the 209 primer, and soot bleeds back out around the primer. Iknew I could come up with something that would at least reduce this. Then it hit me, an o-ring in the bottom of the primer pocket would seal the face of the primer. I was very surprized at the results, no blowback. This plug is a two-piece, and really not what I was looking for, as I still had to use the crappy standard NEF breech plug wrench (which I also modified several years ago).

Standard NEF breech plug on left, Hubbard on the right.
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Just a small picture of some other successful mods I have done along the way. Trust me, you don't want to see them all, nor do I have the time to compile it.

L to R; Standard NEF plug without primer carrier (POS), my custom #11 primer conversion, standard 209 plug with primer carrier, .25 ACP breech plug, custom Hubbard breech plug.
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This is a uni-bushing .25 acp back to 209 primer conversion.
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This is a upside down .25 acp back to 209 conversion. This required turning down the rim slightly, and taking a little off the mouth. This worked very well, but did not conquer the blowback problem, and I had to use the brass.
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Then my prayers were answered. Nick contacted me and said that he had a breech plug for a NEF that he designed. He was using this plug in his and his sons rifles. It was a one piece plug, but the only problem was it was of the newer 5/8" variety. My two NEF rifles used the 7/8" thread. So I was on a quest to find me a NEF Sidekick with the 5/8" breech plug, and aquired one. Nick sent me a plug to try, as I was dying to find a plug that I coud just pop a primer in, no muss and no fuss. The plug came and I couldn't wait to test it out with Blackhorn 209. This plug also headspaced off the rim of the primer, so I was concerned that I might still have some blowback with BH209. But first I wanted to conduct some primer tests without a load.

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I fired it with a primer and knew I would have to tweek it a bit if I wanted to seal out blowback. I then did some measuring and came to the conclusion that I could utilize my o-ring modification in this plug as well. This would help seal the ignition, while providing maximum flame and pressure for ignition.

Here is a unfired primer, primer fired with my o-ring mod, and a primer fired without the o-ring mod.
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This is an unscientific experiment I conducted over a year ago. I fired two primer through the plug approximately a foot from the snow. Primer with o-ring on left, without on right.
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Early prototype MU plug, with my o-ring mod in the primer pocket. DONT LOOK LARRY!
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Production plug.
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Breech after a range session.
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I am running out of time, but to make a long story short. I contacted Nick with my findings and he liked it as well. I was ecstatic when he said he would make the 7/8" plugs, and tried to help as much as I could with that project.

Gotta run! (to be continued)
 
sbuff said:
I hate to be continued's.................. !!!!!

Steve

Well, work gets in the way, unfortunately. I'm not retired like some of you lucky fellers.


......continued. :wink:

The 7/8" plug works outstanding with the o-ring as well. Here are a couple pics of the plugs.

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O-ring before (left), and after (right), as well as 38 fired primers from a range session.

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Each rifle is an individual, and all are not exactly alike. Manufacturing tolerances can vary greatly from one rifle to the next. This o-ring can help close the gap.

It is not as easy as just dropping an o-ring in any breech plug and go shooting. You will need enough space to accommodate the majority of the o-ring, and the right compression. Primer lengths can vary as much as .018" from one brand to another and also should be considered.

I have used similar set-ups in some of my other rifles, mostly Knights, but that is a whole different animal.

BuckDoeHunter,

How much space do you have in the primer pocket? If you have a caliper, you can take a primer and measure it,,,, then make sure your breech plug is tight,,,,drop in the primer and fire it without a load in the barrel,,,, then re-measure the primer. The primer cup will usually move back in the battery cup, the overall length will grow to your extra headspace. This is one way, another is to place a straight edge accross your barrel breech and measure the gap between the primer rim and straight edge with a feeler gauge.

If you can get me those measurements, I can tell you if there is something available without modifying your primer pocket. You need to compress the o-ring, but less is better in this case. About .015 is perfect, so if you have about .025" of play, we might be able to set you up with a 1mm thick o-ring that may give you the right compression.

There is a little method to the madness. :lol:
 
Thanks for all the info!
Busta, I don't have calipers or a feeler gauge. I put a straight edge across the breech. There is a little space, but not much. I picked up an o-ring that fit in the pocket but it was way too thick. It was 1/16" thick, I cut it in half but it was still to thick. I couldn't close the action. It was close to closing but just didn't quite make it. What is the thinnest o-ring in your impressive collection? I need to get some more tools. You can never have too many!
 
BuckDoeHunter said:
Thanks for all the info!
Busta, I don't have calipers or a feeler gauge. I put a straight edge across the breech. There is a little space, but not much. I picked up an o-ring that fit in the pocket but it was way too thick. It was 1/16" thick, I cut it in half but it was still to thick. I couldn't close the action. It was close to closing but just didn't quite make it. What is the thinnest o-ring in your impressive collection? I need to get some more tools. You can never have too many!

BDH,

The thinnest one I have is the 1mm one in the center of the pic in the post above. That equates to approximately .0395", which sounds like it is way too much for your problem.
 
BuckDoeHunter said:
.............................. I picked up an o-ring that fit in the pocket but it was way too thick. It was 1/16" thick, I cut it in half but it was still to thick. I couldn't close the action. It was close to closing but just didn't quite make it....................


The other day whilst shooting my Omega it seemed like there was more than usual blow back.

Upon taking a closer look at the breech plug, there appeared to be considerable flame cutting at the bottom of the primer pocket, and looking closer revealed a hole being drilled sideways through the breech plug, apparently by flame.


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This breech plug has seen many rounds, and also has been modified and fitted with a savage vent liner. It hasn't seemed to be as accurate as a new unmodified breech plug, so i figured i would toss it.


Screwbolts suggested i drill the primer pocket deeper using a letter C drill which would allow the use of an O ring. I tried using an O ring in the damaged breach plug without drilling it, but couldn't get the action to close. So, i followed Screwbolts advice; purchased a letter C drill, and drilled the primer pocket some deeper.


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Here is what the breech plug looked like with the O ring installed. It fits nicely, and doesn't want to fall out. The O ring is 1/4" outside diameter; 1/8" inside diameter, and 1/16" thick.


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This morning i headed up in the hills, and fired 7 shots with the Omega, and the modified breech plug, with an O ring installed. The load was 105g BH209, a 300g 44 caliber xtp, a Harvester crush rib sabot, and a Federal 209A primer. Following is a picture of the 7 spent primers, and the used O ring as well, along with a new O ring.


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One can see there is zero blow back when using the O ring.

The accuracy wasn't very good today though. The pictured target was shot yesterday using an unmodified Omega breech plug (yellow holes), and today using the modified breech plug with the O ring, and the savage vent liner installed (green holes). The range was about 102 yard, and the air was about 30*, with no breeze.


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To me, it doesn't seem worthwhile to install a vent liner in the Omega breech plug. In my brief experience, the standard Omega breech plug seems just about perfect as is. However, once the breech plug has been used a lot, and suffers from flame damage in the primer pocket, it would seem that using the 'C' drill, and then using an O ring will extend the useful life of the breech plug. Perhaps there are those that will want to use an O ring in a 'new' breech plug so there is zero blow back. My guess is the addition of an O ring shouldn't affect accuracy, unless it makes it better.
 
ronlaughlin


Just as a side note, I have ventured in another direction rather than using an 'O' ring I am using a stainless washer. My feeling is that the 'O' ring is certainly easier and quicker but fitting the plug with the washer will last a much long time and when it does wear out push it out and install a new one.

Here is a picture of the Lehigh plug with a washer spacer installed. It allows the use of all these primers as they press fit the nose of the primer to the face of the washer.

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This is the bolt face and the primer adapter after 22 shots....

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This is the BP after 22 shots...

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And here is the target - it is only a 50 yard target... but it was effective.. It was shot with T7-2f and 8 different types of primers.

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sabotloader

You have led me to thinking about this metal washer installation, instead of an O ring. Out in the shop i have some aluminum washers that are called 'back up plates', which are used on the back side of flimsy material when using 'pop rivets'. These i could turn down on my lathe using wood cutting tools. I may give them a try. Aluminum has some strange properties when it comes to cutting it with a torch, and may be able to survive the heat from the primer and powder flame. I'll guess you think this would be silly, and it sounds silly to me too, but i am not very comfortable trying to turn stainless with my nice wood working tools.
 
ronlaughlin

I'll guess you think this would be silly, and it sounds silly to me too, but i am not very comfortable trying to turn stainless with my nice wood working tools.

What i do, is INSERT IGNORE the washer on the screw run the nut on tight, put the screw in the chuccl of a drill - spin it and apply a file until you have it filled down to the diameter you want. Remember not to make it to small as you want it to press it in.

Not sure how long the aluminum might last but surely it would out last and 'O' ring.

The other problem you have is gretting the correct thickness of shim.

That is why i say this is not as easy as a rubber 'o' ring - there is a little bit of engineering to the project...
 
sabotloader said:
flounder

#5-193

That is the number he has suggested to me....

Is that the one you tried in the Lehigh conversion too?

Im going to try the o-ring method first and then move on to your washer mod later. Sounds like a interesting test on the modded CVA pug i have if needed.

This weekend looks like its range time!!!!!! /happy dance emote :lol:
 
GM54-120

#5-193 is a commercial high pressure 'o' ring and yes that is the one - sometimes you need to 2 rings per pocket.....
 
sabotloader said:
..................................What i do, is INSERT IGNORE the washer on the screw run the nut on tight, put the screw in the chuccl of a drill - spin it and apply a file until you have it filled down to the diameter you want.....................

Hmmm.......................well........................that is just too simple.



I will give it a try!................Thank's for the head slap!
 
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