I don't know for sure, but from what he has written, i don't think Mike has looked much at an Accura breech plug. If he has he can fix what i say. Otherwise, please allow me to jump in here.

The flash hole of the Accura breech plug is only about 1/8" long. There isn't enough steel there to 'add much more of a concave end to what's already there. This is why i intend to install a vent liner in said breech plug. Installing a vent liner will allow one to make more of a concavity.

Please forgive me, if my intrusion here is unwelcome.

O.K. Mike, but I was just trying to figure out what was best for the use of Loose Powder with the end of the BP. If it was better to have more of a concave end with powder then I was gonna try and give it a little more (concave) As for CVA spending some time on the BP, most of My CVA BP's are the same on the ends, I dont think they tried hard enough or spent enough time.
Thank's for your thought's.
(BP)

Breechplug

I am not really sure whether more or less is the best answer - I believe it is best to have the concave end on the BP. It seems to me it is easier to ignite the tip of the cone of powder and let that burn through the bulk of the powder.

Again the problem that I am trying to help is blow back through the nipple - not ignition. I think if you want to help ignition (if you are having a problem is to install the Lehigh Vent Liner in the bottom of the concave cone of the BP.

Yes Mike Blowback is what were doing here sorry.....I have NO problem with ignition, it was just a passing thought that went with the redoing of the Flashchannel. Im getting the BP drilled out tomorrow and I'll let you know how it goes. I should be able to shoot too as our temps are gonna go up, finally, from below zero to 20.
Thank's Mike
(BP)

Breechplug

When you close your Accura is the primer held in the primer cup tightly against the breech block? If you were to check your Triumph - I think you will find that the primer is held fairly snugly in the primer cup as you pull the trigger guard up to the closed position... This certainly helps reduce blow back also.....

I could show you a prime example of this with my Omega and the 25 acp conversion if you want to drive a few thousand miles...

I think lee has also pointed out that there is no standard length in the world of shotgun primers... Winchesters being the longest - near .030 and Cheddite being one of the shorter @ .286 in length

i believe you hit the nail on the head here for a blowback free ML.
i have three guns here that are blowback free,the triumph,knight vision and nef sidekick with metrics unlimited BP.
the triumph's toggle lock pulls the barrel assembly tight to the receiver and snugs up the primer tight in the primer pocket sealing the breech.the vision effectively does the same thing as it slightly crushes the primer when you close the action.
the metric's plug uses an o-ring to stop blowback as again it seals the breech.the metrics plug also does not have flash channel.when i had a knight shadow the simple addition of an o-ring turned that gun into a 100 % blowback free gun that shot blackhorn 100 % even in very cold temps.i do believe your on the mark with the larger flash channels helping with the carbon build up and really like the vent liner mods you folks are doing.i am going to try making a brass shim for the NFPJ plug for my disc-xt.this will go in the primer pocket to see if i can get a 100% seal
(it's only about 95% now)this thread has been a very interesting read.good luck to all.........karl

Mike, when the ACCURA is closed it is tight so I cant see what's going on with the Primer and if there's any room inbetween the primer and breechblock. I mostly use T7 Primers, Win W209's my second choice. I have'nt checked to see wich primer leaves the most blowback but I will. I just checked and the Win W209 Primers are a tad bit bigger than the T7's
Ron (BP)

Breechplug

Correct the W209's are slightly thicker in diameter than the Win T7 primers. so they should fit a little better.

Here is a picture of the primer sitting in the pocket on the Triumph. If you lay a straight edge across the primer and the breech plug - the primer is just slightly and I mean slightly taller than the edge of the BP. With the gun closed but not latched you can feel and see the BP touch up against the breech block. When you close the trigger it seems to tighten it just a bit more. This is a Win T7 primer in the cup. I can not actually say that the block presses on the primer but it is very close to that. If the primer expands in length at all during ignition it sure would be.

Sabotloader the Win W209's are also a tad bit longer than the T7's. With some of the longer primers would this cause the primer to be pushed in too tight to the BP and block? I know it's o.k. to be a tad bit loose with the shorter primer but what effect does the longer primer and tighter fit cause if any? I know they cant make the BP and Block to fit just one type of primer so there has to be some kind of clearance to fit all types, but can the longer primers be crushed when the breech is closed damaging the primer?
(BP)

Breechplug

Agreed think I got .305 for the W's and .301 for the T7's

I think the companies have made allowances for the different length primers in tier designs...

It would be my belief that you can compress the primer some and not cause an adverse effect, but if you compress it to much you might cause the primer to become pregnant upon shooting making removal from the primer cup more difficult. Think that is one reason the T7 primers are less in diameter than the normal W209.

I do think you could 'crush' or overcompress a primer...

Interesting experiment for you with the type of BP you have in an Accura. Turn the breech plug out a few threads. To the point that the gun will not close - then back in just enough to get the gun closed. Insert a primer and see if the gun will close. If it does pop the primer - what does the area look like? Keep moving the BP in and testing to see if at some point there is a difference in material you see in the firing pin area.

Busta has installed 'O' rings under the primer to take up the space and get some primer compression.

Sabotloader
I tried loosening the BP out a tad then putting in the primer, it was too tight to do, when I did get the breech closed the BP was almost hand tight as I usually have it. Mabey just one O-Ring would be enough to make a really snug fit, or the fit now is as tight as it can be. I'll try a O-Ring when I get some to fit and see what happens. Does Busta have a ACCURA and that's what he tried it on?
(BP)

Breechplug

I do not believe Busta does have an Accura - his efforts were direct at NEF breech plugs which are a lot like the Accura/Omega/Encore plugs....

Sabotloader
how loose can the BP be and still be tight enough to not let blow-by get through? Or was the pourpose of loosening the BP to see if there was room for improvement?
(BP)

Breechplug

Loose BP - I can not even image shooting a gun with a loose BP. Seen way to many bolts and screws give under pressure when they are loose. I always snug mine up to compress the teflon tape. I just do not want the BP working back and forth at all, so I am not a finger tight person or one that backs the plug off a 1/4 which I have seen suggested.

I suppose for a couple of test shots with a milder load of powder you might be able to get some experiments conducted... Think the best thing is try the 'O' ring under the primer if you can find the right size.

Just take your BP to the hardware/automotive parts store and start testing - get some of the correct diameter and in a couple of different thicknesses...

Mike
I have always finger tightened my BP's, there snug but not tight, it's hard to explain it. It would'nt make a difference in blow back with a finger tight BP would it? You'd think this would give it a better tighter fit in the breech with the Primer, right? Most of the blow back comes from the primer?
It's just once a long time ago I got a BP stuck and had a heck of a time getting it out, I used to really snug em down, since then I just snug em in with my fingers, no BP wrench. I never felt any wiggle in the BP when I did this or I'd have snugged it in better.
I just want to get the most out of the BP, should I tighten it in a little better and how do you know when tight is too tight? I'll get some O Rings tomorrow and try em out.
(BP)

I just had a thought......has anyone ever thought of a 2-Piece BP, one that the primer goes inbetween the 2 parts? It would seal the Primer inside. It probably would be a pain at first and second shots would'nt happen that quick but it seems as if it might work??? And NO I have'nt been drinking! LOL
(BP)

Breechplug

When i tape my BP's I can not even turn them by hand - they go in with a ratchet and are snugged with the ratchet handle... the plug is fairly snug all the way through the turning process as the tape is compressed..... again not tight but sung.

I think it might... this is not a good comparison but, put the lid on a bottle of windex loose - turn the bottle up side down - might it leak? Sure might be possible! Put an engine head on a motor that is suppose to hold repeated compression strokes from cold to warm temperatures, but only moserately tighten the bolts - will it leak??? How about the effects of metal temperature. again poor analygies but you get my drift.

Look at the face of your breech plug - then look inside the barrel at the end of the breech plug threads. Do you see a corresponding face in there. Ideally the face of the pug should mate with the face of the bore in the barrel. Ideally the blow back around the threads should be stopped right where these two surfaces mate.

Have you seen this drawing that UC has illustrated for me?



Next thing I do not want you to think I am telling you how to do it - because there is more than one way to skin a cat - but you might try it one time and see.

There have been a lot of peole that have experianced that same thing - but were you or even them using tape at the time and did the tape go on an in smoothly... And that is exactly why i say it works for me but your results may be different.

Look at this picture - and I have to admit it is not the norm - the tape does not usually come out still on the BP as it does in my Remingtons but it does show how well the threads were sealed...



I hear you and I know what you mean - no one wants to stick a BP...

For me and only me - I do use a socket and ratchet to install the plug - I do snug it up with the socket and ratchet to the point that I feel I am compressing the the tape on the nose of the plug but not tearing it. To check this after the plug is install I shine a light down the barrel. I should see tape all the way around the bottom of the barrel where it has been compressed face to face. That is why I wrap over the nose of the BP. Again works for me but... it has taken me awhile to develope putting thetape on correctly and the feel of installing it.

None of this has anything to do with the blow back - back up the middle if the BP - that is another different game...

Wish this made as much sense to you as it does to me - actually wish I could just drive over and show ya...

There is a two piece 209 unit built for sidehammers - the name of the device eludes me at the moment (old timers disease) The closet thing to it for inlines is something like a 25acp conversion... which uses a prime and a shell casing... Wish I could show you how that works in my Omega - would not be as effective in a break open though...

Sabotloader,

Is that your Remington"s Breech plug in the last photos?

Breechplug,

Because the threads on the breechplugs are relatively course threads, Just being a little loose is several thousands of an inch. The o-rings used in the above mentioned posts are available at Lowes in packs of 100 IIRC. they will be found as faucet repair parts I believe. Your rifle, if it has looseness to the primer pocket, the o-ring would make a good seal. from what I have read on GB outdoors they last a long time also.

Donot run with a loose bP, this will allow gas cutting of the threads to get started, Once this starts the BP will be ruined fast and there is a good chance that the thread internaly in the barrel will suffer also. Grease-oil-tape, in/on the threads of the BP act as a sealant, yes even a film of oil.

Notice on Sabot loaders shown BP above the threads do not go all the way to the face. This is important and has a purpose, if there is gas leakage at the sealing surface( and I asure you there is on a naked BP, SLs tape helps stop it) This gas leaked will be Hot and very High Pressure, The small area of no threads is an expansion chamber (for a lack of better terms), this small area will allow the temp of the leaked gas to cool some and bleed off pressure slowing them down minimizing the gas cutting and erosion to the very important THREADS.

Ken

Screwbolts

Yes, that is one my Rem BP's. And as I said The Remingtons are the only ML that the tape usually comes out intact and still on the BP.

I know some have the XT speed BP and since I use the Teflon tape on them I put a picture on.
The thing I found thats different is that I need to spray the Teflon with Birchwood Casey synthetic oil after I stretch it on to be able to operate the insertion and extraction of the BP with bare fingers.
It is not necessary with this type BP but it sure makes clean up a lot easier. The BP shown are from my Triumph and my Endeavor encore, the Triumph still has the home-made Savage type vent-liner the Encore Endeavor has the Lehigh, the Triumph has the vent liner backed up a couple turns so it is visible. I found making vent liners a painstaking job and not worth it when you can by then for about 5 dollars. Although I have never burned one out if it did [matter of time] even though they are much harder than a breach plug it is simple to replace them and much cheaper than an XT breach plug. It is also nice to take them out when doing a thorough cleaning, polishing the flame channel also helps keep the carbon form sticking.

Sabotloader
From now on I'll snug (tighten) the BP down with the wrench and do the inspection inside the barrel to check the tape. This along with the O Rings should make a world of a difference. As I stated awhile back, the blow back was'nt all that bad, it was just on the fireing pin area and breech that surrounds it. This should be a big improvement I'll let you's know. The last thing I want to do is tun the threads in the Barrel, a BP can be replaced. My older style inlines had blow back pretty bad, plus I was using 150gr's of Pellets wich made it worse. After a session of shooting the outside of the breech area including the bottom of the scope was covered in blowback, I used to have to put bore butter on the outside of the barrel and scope where the blow back got just so it would clean off easier. Plus when I shot I'd actually feel the blowback particles hit me in the face.
Second I was afraid to look this morning after mentioning the (2-Piece BP) I thought I was gonna get thrown off the Forum,LOL! But hey ya never know if they had a 2-piece BP where the Primer was set inside then the second piece of the BP would screw onto it completely containing the Primer just leaving a small hole where the firing pin would ignite it, and when closed would make a tight fit.........
So on my Triumph the BP can only get tightened as much as the (turn) allows and no more, wich is good as you know when tight is tight, you cant overtighten it. On My ACCURA I'll just have to find that sweet spot.
Thank's for all the advice Mike, and everyone else, I'll let you know the results.
(BP)

Just goes to show you even thou I read your post and found the info very good, I missed the word Remington, Thank you for clarifying. I just reread it LMAO ,Yes it is plain as day listed as your Remingtons.

LMAO

Ken

Lee can you post a pic (not thumbnail) as for some reason I cant open the darn things on My Computer.
Thank's
(BP)

Breechplug

At the fireing rang I really do not like to loosen the plug and for me it is not necessary... But, I would back to Cayugad's words of wisdom for you when you are starting out.... after 7/10 shots with your wrench back the plug off just a smige and re-snug it.... I would do this until you are comfortable with the whole operation...

Just remember with that plug you are battling two sources of possible blow back. Blow back from the threads and blow back from the primer system in the BP.

I am positive the tape will stop the BB from the threads... and I am sure the 'O' ring will help the 2nd source.

If you look at your Triumph BP you will see they stop thread blow back with the gas rings on the nose of the BP and what might get by that is stopped by the 'O' ring at the collar. And that 'O' ring is replaceable.

I would say that is a pretty accurate description...

The Triumph works so well because you are actually compressing those steel gas rings in that quarter of a turn to creat the seal... That design came from one of the milatary rifles that use the same type gas rings.

At first do not be afraid to even put a light coat of gun oil on the outside of the Teflon tape to help it screw in smoother if you are having a problem... It should go in smooth and with about the same amount of twist pressure all the way to the snug position.

Aint it all fun?

Breechplug

Here is Lee's picture

Screwbolts

No problem - I NEVER do that :D

Thank's Sabotloader
One other question, I know the BP on the Triumph is a good one, but since the Primer also sits a tad bit above the BP, if one were to put a O Ring under the Primer on the TC's BP then this should really make it work good? Also I cant open lee's pic, it wont even give me a (hand) on it, just a (arrow).
(BP)

Breechplug

Really do not think it is necessary - I can not get ANY blowback from the Triumph even with a 140 grains of BH. It is the cleanest gun I own..

I posted Lees's picture for you...

Breach Plug I took those BP out of the guns to take the picture they were in the guns ready to shoot. Lee

Got some O Rings to put behind the Primer today and just went out and shot a few rounds into the McKenzie Deer Targets that I still have in my yard from Bow Season. It made a Big Difference. I first used a T7 Primer that was loose fitting in the BP, it fell out if you tipped the BP twords the ground. The O Ring made a better seal and there was hardly any blowback. Then I tried a Remington Kleen Bore Primer that was a tighter fit, blowback was even less. Both were almost clean, but the Rem. was better. I suspect the hole in the Breechplug is TOO BIG, it lets too much blowback through, it should be smaller. Does anyone else have a ACCURA and notice this?
And I can get away with this as I live in the Country and my only neighbors are my Inlaws that live accross the road from me. My Mother in Law called a few minutes later and said are you shooting Coyotes again? I said yes to keep it short.
So a O Ring behind the Primer in a ACCURA cuts the Blowback to hardly none.
(BP)

I forgot to mention this...I have always been pleased with the preformance of my ACCURA, accuracy has been more than I could hope for. The little bit of blowback I got did'nt matter much as it was very minimal. I just wanted to see if I could get it eliminated or just about. The BP does have a hole too big for most Primers and a smaller hole would probably make a big difference. When CVA comes out with the New ACCURA with it's new and improved BP it should be a ML that would make anyone happy to own. The 3 I have now are good enough for me so I cant wait to see the newer ones, they should be a awsome ML for the money.
(BP)

Breechplug
Have you tried any Winchester 209 reloading primers? They are the longest primer and I was wondering if the length would help control the blowback with out an O ring. Lee

Lee do you mean the Win W209 Primers? if so I have them, they are slightly longer but Im not really sure this is the cause. As mentioned above in my other reply, the Primer Hole in the ACCURA's BP it too big, all the primers I have tried in the BP are too loose fitting. Most of the blowback is getting through there I suspect. If the primer hole was smaller Im sure this would eliminate most of the problem.
I have tried the T7, Win W209, Rem. Kleenbore and CCI's, there all loose in the BP. I know the longer primer would lessen the blowback but not eliminate most of it.
(BP)

Breechplug

If you make the primer holder area much smaller you might have a problem getting a spent primer out of the cup.

The primer casing acts much like the brass shell casing in your rifle. As it is shot and pressure is exerted the primer can swell to the walls of the cup to created a seal as does a conventional shell casing. After shooting and with some cooling the primer then should contract back to some where it's orginal size so that it can be easily removed. Problem... aliminum/steel batter cups that you find on on a lot of primers today (less expensive) do not expand as well nor do the contract back done as well or as fast.

One of the reasons that I like the Cheddite and and Rem's are they still have conventional Brass battery cups.

BP you may have experiance this in your trap shooting - Shotgun shells with a true brass base, seem to last longer and work smoother (Winchester AA's or Remington STS's) than the steel bases or steel bases that a plated with a brass color. In my Rem 870 with the 28" factory barrel the steel shotguns shells will actually get stuck unless I really wait for them to cool.

Just thinking off the top of my head....

True about the Primers and Trap Shooting experiences with reloading and shooting, but the ACCURA's BP's primer holding area is the loosest of any BP's I ever had. As you mentioned though after the primer is shot it does fit tight in the primer cup. During the firing of the primer does it expand so fast to fill the gap that it does'nt allow any blowback to escape?
(BP)

Breechplug

That I do not know - but i would think that when the back pressure hits it would cause the primer to enlarge. Again I am not sure, but the certainly got something right with the TC speed breech and the primers wobbles in it also.

Well, i ordered vent liners from Lehigh on the 7th, and had hopes they would have arrived here today, but they didn't. In anticipation of their arrival, i started the work on the breech plug of my Accura toward making it more like the Omega breech plug.





The plug on the left is a brand new Accura plug, the one in the middle is an Accura plug that has seen many shots, modified to accept a vent liner, and the plug on the right is an Omega plug.

Now, when the vent liners arrive here, i imagine the modified plug may require a little more work to be just right, then it will be off to the range.

Ron I cant wait to see your results.
(BP)

Ron, did you get your vent liners yet??? Just wondering how your doing on your BP Project?
(BP)

Both the Savage, and the Lehigh vent liners arrived here yesterday.

I began with the install of the Lehigh, and it seemed to work quite nicely. The unmodified Accura breech plug on the left, the modified Accura breech plug centered, and the unmodified Omega breech plug on the right.





Then, i gave the savage vent liner a try, and it also fit nicely.



I decided to install the Lehigh vent, and loaded the Accura that has factory open sights, with 105g BH209, Harvester Smooth Sabot, 300g xtp, and W209 primer.

This morning i headed for the hills, set out a target, and moved the truck to the place i normally park it, which turned out to be 101yd from target according to the laser range finder.

The first shot was into a stump, and then i fired 8 shots at this target:



The rifle appears to be shooting some high now, with this modification. Ignition was instant, and i ended up loading and shooting the rifle about 16 times before going hunting. Blowback may have been less than what it was before being modified, but then again maybe not.

After returning home from hunting, i replaced the Lehigh vent liner with the Savage vent liner, and will try it out tomorrow morning.