blowback?

[earnhard3]

I hear talk about blow back.

thats when the primer is hit and lets the powder ignite to push the bullet the pressure blows back correct?

how do I KNOW I have too much. All guns have a little for sure but how do you know if its too much?

 

[jsteurrys]

I am getting zero blowback now in my Knight DISC Extreme using the NFPJ breechplug wrapped with teflon tape and an "o"-ring to seal the primer. This was not always the case using grease and FPJs which made a real mess when using T7. I had to clean the action every 10-15 shots as it would gum up. Those days are long gone and I am much happier.

 

[UtahRob]

when you see smoke coming out around the primer and it looks like this around your breech plug , Then you have WAY too much . Then its time to remove you BP and clean it !! I got this much blow by just shooting off 15 209 primers , NO powder . I was testing to see if the carbon built up was coming from the primers or powder . I gave up using 209 primers and now use .25 acp conversion with 777 .

 

[Skopia]

I am getting zero blowback now in my Knight DISC Extreme using the NFPJ breechplug wrapped with teflon tape and an "o"-ring to seal the primer. This was not always the case using grease and FPJs which made a real mess when using T7. I had to clean the action every 10-15 shots as it would gum up. Those days are long gone and I am much happier.

Could you tell me where the "o" ring goes and what size they are and what powder are you shooting?
Thanks

 

[NautiBuoys]

Blowback

When it burns the bottom of your scope, like it does on my TC System 1 (open breech). On my TC Omega there is virtually none or what very little there is, is directed down into the stock for no scope damage/ease of cleanup.

 

[jsteurrys]

The "o"-ring goes into the bottom of the counterbore that the primer fits into. It creates a face seal between the Primer and Breechplug. I am using a 5-193 "o"-ring. I am using BH 209 exclusively these days. I was a T7 user previously.

 

[Skopia]

The "o"-ring goes into the bottom of the counterbore that the primer fits into. It creates a face seal between the Primer and Breechplug. I am using a 5-193 "o"-ring. I am using BH 209 exclusively these days. I was a T7 user previously.

Be patient with me here. The "o" ring will be inserted into the cylinder, or "counter bore" that the primers fit into? If that is the case, what material is the O ring made of and does it get worn out from the pressure or heat from the primer? Also, my NFPJ plug has a domed face. This plug is OK with B209?

 

[sagebrush]

i would like to know also where is the best /or most convenient place to obtain these "o" rings?

 

[jsteurrys]

The "o"-ring does wear out after 50 or so shots. The "o"-rings that I am going with are made from Viton. The "o"-rings can be purchased from McMaster-Carr or a good hardware store. You need to do a little experimenting with the right thickness of "o"-ring as the "headspace" is not the same in all guns. I have two guns with one using 1 "o"-ring and the other 2 "o"-rings to create same amount of compression on the "o"-ring by the primer. This is determined by operator feel. The NFPJ breechplug works well with BH 209. I use Federal 209A primers.

 

[bluedog]

o-ring question?

Can you please provide a bit more info regarding the o-ring size.....I checked out the McMaster Carr site but do not understand how to translate the 5-193 size into an order from the site.....is there a part# I can reference......is the Viton material the best for the job?
Many thanks! Billy

 

[jsteurrys]

The 5-193 "o"-ring measures as follows:
ID - .176"
OD - .256"
Width or cross section - .040"
These are nominal values. These "o"-rings are manufactured by Parker Hannifin. Viton is good for 400F-500F before it starts to degrade.

 

[bluedog]

Well....I don't feel quite as incompetent as before.....when I contacted McMaster Carr about the correct o-ring (because I could not find it)....they said I could not find it because they don't have it! Below is their email to me.
'
'
'
Billy,

All of our available o-ring sizes are listed on our website. We do not currently offer a "5-193" size or a .176" ID Viton O-ring.

Regards,
Mike

 

[jsteurrys]

Look for an "o"ring with a .176" ID and a .040" cross section or metric equivalent in whatever material is readily available. There is no guarantee that what is working in my gun will work in yours as this is still in the evaluation phase.

 

[bill smith]

i get a lot of soot also but i wondered about this from a slightly different perspective. i notice that the flash hole in the primer holder/ breech plug is very small. i was told that it is typically 0.030". compare that to the flash hole in a shotshell.....where this primer is normally used. i wondered if increasing the flash hole size would allow more of the combusted material to enter the bore and send less of it backward. it seems to me that the primer makes a specific amount of soot, fire, etc. this stuff must go out of one end or the other of the breech plug.

does increasing the size of the flash hole make any sense to anyone?

 

[cell]

i get a lot of soot also but i wondered about this from a slightly different perspective

Try a different primer.I have two brands in my shooting bag.Only one gives me blowback.I'm not an expert,but I don't think increasing a flash hole is good.Thats why manufactures recommend changing your breach plug.....after a amount of use the flash hole gets bigger.

With that said I suppose it depends entirely on your breach design.

 

[wildhobbybobby]

Increasing the size of the flash hole will probably increase blowback rather than reduce it, because the high-pressure gas in the combustion chamber will have an easier path to follow back out the breech. I tried increasing the size of a flash hole in my KRB-7 and it did not make the gun work better with BH209, and did increase blowback.

The secret to containing blowback is to tightly seal the primer in the breechblock so that the gas has only one way out...through the muzzle. I have never been able to understand why the manufacturers of inline muzzleloaders haven't figured that out.

In fact, if you look at many of the 209 type breechplugs out there, they have vents that are designed to deliberately divert primer gas out into the breech, rather than funneling them into the bore. Go figure...

 

[cell]

I think they mostly have it right.Its the manufacturing tolerances of the primers that are off.Like I said I get blowback from one brand of primer,and not the other.I mentioned before that I get blowback from the special muzzyloader primers...the ones that don't have quite a big bang.All in all I sum it up to the experience of muzzyloading....aren't they supposed to be dirty fun?But the blow back on my rifle can be dangerous too.If I don't clean it off it can muck up the latch,and cause the the rifle not to close all the way.

This is on a traditions xlt by the way.I'm sure it might be different on a higher end rifle tho.

 

[squirrelhawker]

Increasing the size of the flash hole will probably increase blowback rather than reduce it, because the high-pressure gasses in the combustion chamber will have an easier path to follow back out the breech. I tried increasing the size of a flash hole in my KRB-7 and it did not make the gun work better with BH209, and did increase blowback.

The secret to containing blowback is to tightly seal the primer in the breechblock so that the gasses have only one way out...through the muzzle. I have never been able to understand why the manufacturers of inline muzzleloaders haven't figured that out.

In fact, if you look at many of the 209 type breechplugs out there, they have vents that are designed to deliberately divert primer gasses out into the breech, rather than funneling them into the bore. Go figure...

The problem is there because of good ol mass production. The processes involved in the barrel threading, breechplug and everything else has to have a tolerence. Add them all up and there is room for blowback. Some guys will get lucky and get a tight-tolerence gun. My buddy and I make our own plugs and are able to custom fit to each gun.
Even though the o-ring has been a blessing to most of you guys...the better fix (other than a custom plug) would be a gasketing material of metal....for durability reasons. I know Busta a while back did some work on this o-ring/ primer thing. I ,at the time, didnt pay a lot of attention to it. Maybe this was ALREADY tried and didnt work.

You can get shimming washers in very small sizes...and various thicknesses. The ring at the top of the 209 is what you make "conform" in this gasketing operation.
If I insert a primer that is .300" into my plug and close the action..then open it and measure it again..it will measure .295" If it was .297"..closing my action on it will result in a .295"... see what I mean. Firing the gun even with high pressure smokeless loads result in basically no blowby
by the primer. All the soot is strictly at the bottom. Im not sure how the washer idea would work..but I would sure try it...

Anybody think of any problems with this idea??

 

[squirrelhawker]

I checked out some of the small flat washers I had laying around. One for a #6 screw may have about the right i.d. hole. Slid the washer onto a nail
size 16 or so. Grind the o.d. of the washer on the grinder wheel..it will spin very quickly....being driven by such a large "drive" wheel. Vary the pressure to get the rate you want. You will be able to remove material from the o.d. of the washer in a very uniform concentric manner on this "hillbilly" washer lathe. You will want to grind down the od to the size required to be an interference fit into the primer pocket. The first one you do is actually to determine the thickness needed on your gun. When you make the final one..it will be a thou. or so larger than your pocket dia...you will drive it in for a permanent fix. If you dont have a caliper micrometer..you should get one..not real expensive for one that is good enough for "reloader" use. You can smooth out the flat surfaces of the washer with sandpaper laying on a flat surface. Another way to do this is to drive the "turned down" washer into your pocket..and then use your dremel tool with a 7/32" chainsaw sharpening stone to get a fitted thickness for your particular gun and primer. The washers I had here were .025"-.030" thick. Stainless steel. I have never had to do this to one of mine but it will work, Im sure, with some tinkering.