Blowback
 

I just had a thought as I read Sabotloader's report on his Renington Bolt Conversion. He mentioned how he was going to modify the head space between his bolt and T7 Primers, as some people may not fully tighten there Breech Plugs as he does tighten his, thus allowing for the small difference in space between the two.
Here's my question.....I am one of the one's that just (finger tighten) my BP. A long time ago I had a bad experience where I had the BP too tight and I had a heck of a time getting it off, when I did I from then on just finger tightened it so this would never happen again.
If one finger tightens there BP does this allow more blow back as I assume it would? Also when one get's blow back form the BP does the blow back cause a loss in the full effects of the powder charge? Would you lose velocity from the loss of blow back?
Also are there any other effects on the ML from blow back besides just more of a mess to clean?
(BP)

In all my ML 's it the primers that gives me the blow by not the powder . I fired 15 primers ( no powder ) through a clean BP and it got so fowled up with carbon, i had flames coming out the side . It didn't do it with 1-10 primers shot . As the carbon builds up in the breech plug the hole down the middle gets smaller and smaller , then i got tons of blow by . I gave up using 209 primers , IMO they are to hot for some BP's and BH209 needs a hot primer . so i have gone to using 777 powder and a .25acp conversion that uses small rifle and pistol primers . With this conversion i get NO blow by ever because for one, i get a 100 % seal and two , i use weaker primers that do not load up the breech plug with carbon . It's a win win for me . I was replacing breech plugs every tub of powder and the Bh209 is more $$$ , they want 38.00 compared to 24.00 for 777 . here is a photo on my Encore BP after firing 15 primers only ( no powder ) from a clean breech plug . I used a drill bit to clean out the flash hole and fire channel before doing this test .

I shot a 1/2 tub of Bh209 with this new BP ( photo below) and you can see the flame cutting caused by the Win 209 primers going across the ring in the bottom of the primer pocket . Even with the longest 209 primers the carbon would build up and the blow by would get very bad and even start blowing the primer apart and bulging the side of the primers .

http://i365.photobucket.com/albums/o...ckDSCN0154.jpg

same breech plug with only 5 primers shot through it and you can see it starting to get blow by and i really started to get bad at around 10 and i stopped at 15 . I also got flame/fire cutting from the blow by in the primer pocket of the BP ands once that starts , you will no longer have a good seal and you can kiss that BP good by .

http://i365.photobucket.com/albums/o...tsDSCN0163.jpg

NO more problem since i started using this BP .http://www.thebuckskinner.com/breech_plug.html as you form fit each brass to your gun by closing the breech on the brass giving you that 100% seal and a spotless gun , also my gun got so bad the firing pin got stuck in a primer and i could not open my encore and i had to remove the hinge pin to get it apart , then remove the firing pin and cleaned it removing the carbon from it . that was the final straw and is stopped using 209 primers and any powder that needed them . It was a good move for me !!:woot:

Thank's for the info UtahRob, I have also done some reading on the conversion away from 209's to the .25acp's It makes sence, but after Im sighted in and if I shoot a few shots I clean My ML throughly so the carbon build up from the 209's is'nt a problem for me. My question was if a finger tight BreechPlug would allow blowback and thus cause a loss of velocity from it.
(BP)

Breechplug

Here are my thoughts... the finger tight plug will allow some blow back back around the breech plug, even with BP grease. How much I am unsure of as it varies in each gun depending on how tight or loose your particular BP is. I have always maintained it is best to stop the blow back at the flange of the BP and the barrel flange inside the bore. If you get it stopped there then you really do not have to worry about it coming back down or out the BP threads. In my case I use teflon tape on the face of the BP and the threads to prevent this.

As to effecting accuracy - unless it was a bad blow back leak I can not imagine that you would ever notice it in the accuracy department. Just remember blow back will contrubute to loss of velocity but again I can not imagine it affecting accuracy with a normal person doing the shooting.

I think that would depend upon a number of things... how close tolerance your plug's threads are to the barrel's threads, what kind of seal you establish and with what agent (tape, grease, or ?), the design of the plug's nose, and what kind of powder you are shooting. I tighten to just snug but usually with a tool of some sort - no torquing beyond snug.

You have two possible paths for blowback, one past the threads and another from around the primer. Around the primer is generally most offensive and matching the proper primer to your plug can make a huge difference. Blowback past the threads is usually stopped by either grease and/or tape - backing the plug away from the fully seated position could only increase the chance of this type of blowback.

There could be situations where backing out the plug a bit would actually improve headspace and provide better sealing in the primer pocket resulting in less blowback. But I think most designers of breech plugs have the intention of the plug being snugged in place. I don't believe I've ever read an owner's manual that suggested otherwise.

That's a very good assessment, myself I'd feel more comfortable if I knew my plug was tight. I'd hate to think of what would happen if some how the plug would back itself out enough to finally come completely out upon firring. I just snug mine up in my Knight:barmy:

Mike, I did get some teflon tape like you recommended, but I just put it on the threads of the BP, above you say you also put it on the (face) of the BP. Do you put it on the face of the BP and leave just enough so it does'nt cover the falsh hole? My problem may be with my T7 Primers in My ACCURA, when I open the action to remover the primer at the end of a Hunt, the primer just falls out into my hand, they fit loose, are they too loose? I dont want to change primers now as Im already sighted in, but I do get more blow back then I'd like.
(BP)

UC, from what I assume your also a ACCURA guy, do you have any problem with blowback, and what primers do you use with your ACCURA? If you read what I just worte to Sabotloader you'll see my problem. It's not a bad problem but I'd like to solve it, my accuracy is fine and the Ml shoots great, I just now think that the T7 Primers that Im using are too loose and let too much blowback out because of there looseness.
(BP)

Breechplug

That seems a bit odd to me. As you know I am in the middle of this Remington project and just completed measuring various primers. The longest primers I have are the Win T7 and W209's. They both measure right at .300. You would think with that length when you close your barrel the primer would be pushed up tight against the rear block. If you go to other primers they will get shorter and allow a less tight fit.

I have never handled an Accura, but I have a Triumph, which is as clean as you get; but it uses the Speed Breech. I just put a T7 primer in it and closed the barrel. I thought it might touch the rear block as I closed it - it did not - so I would say it might be somewhat loose also. In the Omega which has the older style breech plug which I assume is what is in an Accura - it also gets very dirty because of primer blow back - not blow back from the bore. I solved that problem when I switched to the 25 acp. All the rest of my inlines have the regular type old style breech plug and they all get dirty.

Busta has done a lot of work with the NEF and the use of 'O' rings to stop the problem by forcing the primer up against the 'O' ring to create a tight seal.

Grouse is struggling with the same problem with the Knight DISC series guns trying to clean them up.

It is my assesment that you need a long breech plug with a larger flash channel under the nipple to really provide enough space to stop the primer blow back. Knight did this somewhat with the new BP for the Vision - it is really not longer but the flash channel has been bored larger giving more room for expanding gases.

I would also tell that the T7 primer is one of the dirtier primers, which really has never bothered me to much because I like the way it works with T7.

Breechplug

It really doesn't matter if you cover the hole or not. The first primer you pop before loading will clear the flash hole.



Here is a wrapped Knight breech plug....




T7 primers are naturally dirty - matbe one of the most dirty primers - but I like the way they work with T7 so I will continue to use them. + they are not so hot that the will cause pre-mature gas cutting on the breech plug.

Doesn't your breech plug have a spring that wraps around the BP. The spring has an end that protrudes into the nipple and should hold you primer in place. It should not fall out just because you open the gun - unless they copied TC Encore extractor also...

Mike, my older CVA Breechplugs had the spring in them to hold the primer in, but the newer BP's for My ACCURA dont, they fit too loose. Im thinking they are causing the blowback as the carbon escapes around the inside diameter of where the primer fits into the breechplug. I dont have a problem with fit as when the action meets the breechplug and primer, that is good. It's the primer fit in the breechplug hole where the primer sits.
I have to be careful in the dark in the morning when I put the primer in and close the action as sometimes the primer falls out befor I get the action closed and I dont notice it, or I do see it fall out and have to put a fresh one in. I'd be really bummed if it fell out and I did'nt see it and then have a good buck in my sights and pull the hammer back and then nothing! So now I have to be careful when puttng the primer in to make sure it's there and did'nt fall out. Also Im still gonna send you the pic of my big doe to put on the forum for me, but I was waiting for a pic of a big buck to go with it,,,lol Thank's Mike
(BP)

Breechplug

Something has to hold the primer in... You do not think it is a magnetic thing do you? I know some breech plugs have that now...

I just mic'ed a T7 primer and they have a diameter .244 - I measured a Cheddite and it measures .2465. So they might be a little small but something besides diameter has to hold them in place.

Gotta go to the CVA site be right back... Well that was no luck... could not find anything...

Check with UC - he can tell you for sure -

But, anyway the shooting of the primer and the pressure should make them obturate out a bit to help make that seal. I am at a loss...

Ok two more thoughts just came to mind... I think Mountain Devil -Fronter Gander or what ever is experiancing the same thing you are talking about. He started a thread about wrapping his CCI ML primers with teflon tape to help seal the BP blowback - did not mention that they fall out of his Accura... so maybe this is common thing thing....

Second - I just tried a T7 primer on one my shot gun hulls. It dropped right in the primer pocket - no pressing neccessary - just turned the shell over and tap and it fell back out.... It is definetly thinner than a regular shotgun 209 primer, but only by a few thousands...

No my mind is running away - I thought you were a trap shooter also.. what primers do you use for reloading if you reload???

I keep checking my email looking for it... the picture

I haven't shot the accura yet but i backed out the firing pin bushes a few thousandths to push the primer tightly into the BP. Im not worried about the primer fouling, its nothing since i remove my scope for cleaning. Wincheste W209s are longer than the ccis im using and those w209s are super clean.

I've shot nothing but Win209A in mine with blowback only an issue when I fired Swiss behind a 496 grain conical. With sabot loads, I get almost nothing.

If you hold the rifle barrel pointed up when opening the action, the W209A are loose enough to fall out but not for normal action opening. Very easy to remove though.

After 12 rounds of T7 FFg plus 9 rounds with BH209 (sabot loads)

Breechplug

From those two replys - I think your original assement may be correct the T7 primer might not be the best fit.

While they are the longest 209 primer that i have they are also the skinniest. The Win W209 that UC talked about is almost the same length. I just tried dropping that one in a Remington hull also. I could seat it by just pushing it in with my finger so it is not much thicker than the T7 (which makes sense since they both are made by Win)

The Remington STS is thicker than both of the Win's, as are Cheddites and Feds.

The next thing is to look into to what FG said...

I have no idea what he may be talking about but if that can be done it would certainly help if you could pin the primer against the shelf in the BP.

that there lil screwy thingy. Inside it holds the firing pin/spring. Back it out a little and adjust for proper fit. The CCI Inline MZL primers now fit tight when its locked up. May take a couple shots later on and see if it does anything or not. Will be sure to report back.

Not often i can agree with FG but on this particular thing I think he has a got an good idea if it can be done without damaging the mechanism. It that part strong enough or the threads on both the part and block to handle the blow back pressure? Over many-many shots. I always worry about a loose part, as a loose part creates movent, even a a small movement, can cause a failure...

i fired 2 bare primers today. The first was perfect but the second primer had a real funny, dull/sizzling sound and primer smoke poured out of the stock. Keep in mind, this was just a bare primer!! I opened the rifle and i dont know what the deal was but the primer did something to where it got to messy it splattered my BP grease all over. I think some primers are just a lot weaker than others or something. What ever it was, that second primer was plain bad.

Guy's I dont have a problem with the T7 Primer as fit with the firing pin, everything works well, no need to adjust the fit by backing off the firing pin. I guess the problem with the loose fitting T7's wont be a problem as long as I make sure it does'nt fall out as Im closing the action. I think CVA should have the stainless wire on the breechplugs like on my older CVA's, they fit snug no matter what size primer you use, but some you do need the capper extractor to remove it after firing. I guess the stainless steel wire on the older BP's of CVA's has it's advantages and disadvantages, the only disadvantage would be if you needed a quick seconf shot and did'nt have the extractor toll handy you'd never be able to get the spent primer out fast or with just your finger. But I am getting blowback with the bigger than average hole in the BP for the primers now used in the ACCURA.
(BP)

I would just switch to the Win209A and be done with it. Those T7 and similar primers seem to just cost more so far as I can tell. Sub 1" groups suit me. :)

Underclocked

The only thing is you can get the T7 primers @ Wal mart for $1.75 if you watch. That is why I have a ton of them and they are easy on the 'flash hole' and they do not create the 'cud ring' the hotter primers do with T7. The w209a is in the middle of the line when it comes to heat but way ahead of the T7 primer.

i cant stop using the cci mzl primers! these babies are awesome and allow me to load one right after the other. Including sabots! I stopped after 6 shots, i may have to try a dozen or 2 just to see how many it takes before its toast.

Oh, I had almost forgotten about the crud ring. ;)

FG, just suffer then. :)

lol im not suffering, its winter! when i have time on my hands i just start looking at things and like to play with them and see what happens.

mossy oak brush looks like a nice pattern for my Accura's stock :D


Oh damn it!

Or Matthews Lost camo

UC, I do use the Win209A Primers in my other ACCURA, but the one I chose and sighted in for that Im using for this Hunting season is sighted in with the T7 Primers. It's no big deal, for now I'll just use the T7's and after the season I'll sight in with the Win's. But then again I could break in My SS/Bk ACCURA with it's first ML Kill that's using the Win Primers. But the SS/Camo ACCURA looks so much better than the SS/Bk, either way Im a Happy Hunter!
(BP)

I had both (two in the camo) and actually prefer the black - but I wish they had taken it a little easier with the white streaks. Only have the black spec now (and the APEX!). :)