SMI question

[depo]

Can someone explain to me how does Smi not need some type of replaceable "vent liner"? My quess is, with the 4" longer barrel, they use slower powders (2015) which in turn operate at lower pressure causing less erotion. Still, in time, something must need to be replaced, unless it's the entire breech plug? Any help would be appreciated.

 

[big6x6]

Can someone explain to me how does Smi not need some type of replaceable "vent liner"? My quess is, with the 4" longer barrel, they use slower powders (2015) which in turn operate at lower pressure causing less erotion. Still, in time, something must need to be replaced, unless it's the entire breech plug? Any help would be appreciated.

My ULA doesn't have a vent liner either. :huh?: I've shot it a good bit and have not had a single issue. Since August the breechplug has been out only twice, once when I got the gun new just to LOOK at it and I took it out in October just to clean from stem to stern. Everything looked fine. Nice not to have a ventliner to fiddle with. There has NEVER been one iota of carbon residue in that breechplug either. Guess what? The ULA has only had VV N-110 fired in it! Forbes said I wouldn't need another breech plug. I'm beginning to believe him!

 

[Doohan]

Have you tried 200 SST's in that gun Chuck?

Neat on the breechplug.. I guess SMI is the same!

 

[big6x6]

Have you tried 200 SST's in that gun Chuck?

I did with 5744 thinking it would be the powder of choice. Since talking with IH I'm going to try N-110 since it is doing so well for him with that bullet.

 

[rname]

depo I think it is the design of the breach plug with the vent hole next to the primer and the material the plug is made of stainless which withstands heat and flame better. I have a breach plug with over 3000 shots and still only .oo1 larger than when I made it. Ron Name

 

[Rifleman]

I was wondering about the erosion on the Nula and SMI, good thread.

 

[Mountain Man]

Can someone explain to me how does Smi not need some type of replaceable "vent liner"? My quess is, with the 4" longer barrel, they use slower powders (2015) which in turn operate at lower pressure causing less erotion. Still, in time, something must need to be replaced, unless it's the entire breech plug? Any help would be appreciated.

I posted in another thread about how the Savage plug acts like a car muffler to minimize pressure to the primer. This requires the dead/open space inside the plug, which pressurizes as the powder burns in the barrel. In order to pressurize, gasses have to flow through the vent liner.

The Savage plug is, I think, a major factor in the Savage being able to withstand the kind of ridiculously overcharged test loads the gun was destruction-tested with. However, under normal, responsible loading techniques, it's probably not necessary.

The SMI, and NULA, I would guess, don't have an open/dead space between the powder end of the breech plug and the primer. Thus, there is VERY little space to fill with gas in order to reach pressure. This means there is comparitively little gas flow through or into the breech plug and primer vent. Drastically smaller flow equals drastically less erosion. Less erosion equals no need for a replaceable vent liner.

The Savage design serves a purpose: excess safety in the face of the possibility that people will do stupid things. If nothing significantly stupid is ever done with the gun, it's probably not necessary, IMO.

 

[Anonymous]

The Savage design serves a purpose: excess safety in the face of the possibility that people will do stupid things. If nothing significantly stupid is ever done with the gun, it's probably not necessary, IMO.

It is for that reason it is highly unlikely the fundamental Savage 10ML breechplug design will ever change.

 

[Mountain Man]

That was exactly what I thought. :wink:

 

[big6x6]

I posted in another thread about how the Savage plug acts like a car muffler to minimize pressure to the primer.

This makes no sense at ALL to me how a cylinder in a breech plug with a total volume of .98 cu in at BEST has anything to do with the ability of a muzzleloader to sustain a heavier than normal pressure load? :?: Who did the testing compared to a breechplug SANS this cavity and WITH this cavity? Isn't THAT the only way to determine this? Just curious.... Looks to me that the STRUCTURE of a Savage ML, or ANY muzzleloader is THE determining factor in this..ie steel quality/thickness, breechplug to receiver tolerences, etc...

 

[Mountain Man]

Chuck, my theory is as I repost below. It is just a theory, unless RW knows that the Balls, or Savage, or someone else has tested peak pressure differences.

My theory is based on the supposition that excess PEAK pressure is the most dangerous thing. Peak pressure, especially with the faster powders that are more likely to be overcharged by accident, is reached withing the first 1/8 to 1/4 millisecond after ignition, said in another way, for three-quarters to seven-eighths of the time that the bullet is traveling down the barrel, pressure is falling instead of rising. I don't know whether the cavity in the plug seperated from barrel pressure by a .30 hole provides enough of a time delay to get the plug cavity/primer face past the barrel's peak pressure. If it can achieve that, I would theorize that the pressure inside the cavity, and thus against the primer, would reach some fraction that represents a good percentage, but less than, the barrel's peak. For instance, in a gross overcharge, perhaps the barrel pressure peaks at 75,000 psi, but because of the delayed pressure absortion, perhaps the internal plug pressure only reaches 60,000 psi. Like you point out, it's only a theory until somebody actually tests it, but for now that is my theory.

Not that I think it should make on WHIT of difference in how careful we are. An exploding barrel is no better than an exploding breech plug in my book. Likewise, I don't think that the safety issue is so significant that I would hesitate to buy an SMI or NULA as soon as I can. Just gotta keep saving that pocket change... :lol:

Anyway, what I had previously posted:

Also, the Savage plug is very different from any other plug on the market. The same feature and effect that makes it safer keeps it from transferring as much energy from the primer to the powder.

Most breech plugs have very little internal hollow space/volume from the front edge of the primer to front edge of the plug (where the powder rests). In contrast, the Savage has a internal open column approximately 1/4" in diameter and approximately 1.8" long, and it's capped with the vent liner with only a .030" diameter hole. Without the ventliner, when pressure in tehe barrel jumps up to 30,000 psi, give or take, and then begins sloping off, pressure at the face of the primer would always be pretty much equal to the barrel/"chamber-area" pressure.

In effect, this design of the Savage plug acts as a pressure delay chamber, in much the same way as a car muffler does. Gases under 30,000 psi of pressure, give or take, are going to flow through a .030" hole at a certain rate of speed. But, it is flowing into a chamber (the space running from vent liner to primer) that is 10 times larger in diameter--and remember, because it is a cylinder, volume increases exponentially with diameter. It takes some amount of time for a sufficient volume of gases to flow through the .030" hole to fully pressurize that chamber. Granted, the amounts of timer we are talking about are measured in fractions of milliseconds, but the time differentials should still be there.

So, the entire time the pressure is builing in the barrel, the pressure in the plug chamber/space is lagging behind it. Then, when pressure in the barrel peaks and starts falling, pressure inside the plug chamber/space does not climb to the same peak as the barrel saw, but immediately reverses and starts following barrel pressure back down.

This means that pressure against the inside face of the primer never reaches the same peak as pressure inside the barrel. This is a good thing, since 209A primers were designed to handle the much, much lower pressures of shotguns, and it keeps more pressure off of the bolt face.

The flip side is the flame/gases from the primer detonation encounter the same obstacle to lighting and pressurizing the powder in the barrel of the 10ML. Obviously, the 209 primer does this and does it well. Nevertheless, while a large rifle or small rifle primer may work well with blackpowder in other rifles, or might work well with smokeless in a different muzzleloader with a different style plug, I don't think that the "muffler" effect of the Savage plug would be conducive to use of weaker/smaller primers.

 

[savagebrother]

well i can tell you in the .45 cal. that the s.m.i. breech plug blew primers at less than optimum pressures. that noted the .45 cal. generates pressure much faster. i had them make me one of their plugs with the savage style vent liner screw when they did the work on my ruger no. 1. i used it and problem was solved. the reason for no vent liner in the fifty is there is less pressure across the face of the .50 cal. plug than the .45. also being right next to the primer does not allow the transfer of hot powder gases to the vent hole itself, it has no where to go but the primer itself. i am going to by the veriflame system and see if it makes a difference when using the s.m.i. style breech plug. i will post the findings as i get them.
sb

 

[MCee67]

:huh?: Whut?