CVA Accura MR QR breech plug project

[sbuff]

Not to derail the thread but saying the knight UL is the best production ML made is a very bold statement.

I'll sit back and keep reading.
Steve

 

[Grouse]

Make the plug seal on rear and front length wouldnt matter.

Curious what would you change on my plug for knight bolt gun.

The length is hard to reduce since you need a minimum volume for for flame channel. .800x.156 works well.

So primer pocket .230 +.800 channel + .250 bushing+ .187 lock ring. 1.467 is about as short as it can be.

In your case I have no doubt your doing the best you can. But your using someone else's breech plug and bushing correct? Your plug looks similar to an older savage plug, with added bushing. But your plug is very long for my preference. My goal in the Ultralite was to have a very similar bolt and breech plug to the NULA custom ML. I have a pic of your plug up against the NULA plug and you'll see what I mean. The primer would be inserted into the breech plug and extracted by the bolt. Can't upload pics for some reason, ill see if Sabotloader can post it for me.

 

[sabotloader]

Posted for Grouse

 

[GM54-120]

The NULA plug is incredibly short and has one huge difference than other plugs.

Primers are totally supported and enclosed. They head space on the rim of the primer not on the nose. When the bolt is closed it looks like this but with zero gap between the plug and bolt.

Even the rim is enclosed by the bolt.

This design allows the primer to withstand far more pressure without bulging. It also has one major weakness. Headspace must be perfect and its very primer specific. I can only use a CCI in mine.

 

[Squeeze]

Not to derail the thread but saying the knight UL is the best production ML made is a very bold statement.

I'll sit back and keep reading.
Steve

:lol: I keep seeing that too. It was "supposed to have this and that" but it doesn't Yet it is far superior to all the rifles with identical and interchangeable parts. outside the stock...its just lighter

 

[sabotloader]

Question: With a rear sealing breech plug... will shooting with BP and T7 cause the plug to seize? With the rear seal it seems like the blow back can more easily work back up the threads of the plug?

 

[bestill]

No issues!
The carbon blasts typically only travels about2 threads and use a thin wrap of Teflon tape on threads with a little gun oils on tape. Removes easily and cleaning is simple.

 

[Grouse]

No issues!
The carbon blasts typically only travels about2 threads and use a thin wrap of Teflon tape on threads with a little gun oils on tape. Removes easily and cleaning is simple.

It seems like every way i look at it, a front sealing plug is better. What is your opinion on why a rear sealing plug is better? Just curious to know myself.

 

[sabotloader]

No issues!
The carbon blasts typically only travels about2 threads and use a thin wrap of Teflon tape on threads with a little gun oils on tape. Removes easily and cleaning is simple.

Thank you for the come back! that certainly makes me more interested.

 

[a1smokepole]

In the SML world the new breech plug made by luke is a rear seal and works very will and that's with smokeless powder. and like bestill said only two threads gets powder on it with out tape. and its smaller in size witch gives you more meat in the barrel around the plug. a big plug is not needed you only need to remove a round and powder.

 

[bestill]

No issues!
The carbon blasts typically only travels about2 threads and use a thin wrap of Teflon tape on threads with a little gun oils on tape. Removes easily and cleaning is simple.

It seems like every way i look at it, a front sealing plug is better. What is your opinion on why a rear sealing plug is better? Just curious to know myself.

Rear has no issues with gas cutting like a front sealing plug. Also with machining a front sealing plug down in barrel at say 1.5" with small boring bar is much tougher than a rear sealing plug at say .5"

But the main reason is gas cutting.
Knight and savage are notorious for gas cutting front seal..
The rear seal will not cut also a perfect seal. Once a front sealing plug gas cuts it's a junk barrel typically barrel is softer than plug

 

[a1smokepole]

No issues!
The carbon blasts typically only travels about2 threads and use a thin wrap of Teflon tape on threads with a little gun oils on tape. Removes easily and cleaning is simple.

It seems like every way i look at it, a front sealing plug is better. What is your opinion on why a rear sealing plug is better? Just curious to know myself.

Rear has no issues with gas cutting like a front sealing plug. Also with machining a front sealing plug down in barrel at say 1.5" with small boring bar is much tougher than a rear sealing plug at say .5"

But the main reason is gas cutting.
Knight and savage are notorious for gas cutting front seal..
The rear seal will not cut also a perfect seal. Once a front sealing plug gas cuts it's a junk barrel typically barrel is softer than plug

And I have seen this on knights plug over time it eats away at the seal this is with a gun that has around 5000 round on it and got it new back in 1989. had to have it cleaned up at the machine shop and steel shoot it every now and then.

 

[bestill]

Also rear sealing breech plug can be made with much smaller thread to gain barrel chamber integrity.
Front sealing plug requires a much larger thread to get a front sealing surface

 

[a1smokepole]

Posted for Grouse

The two plug in this pic or rear sealing plugs the one on the left looks like lukes plug.

 

[Grouse]

Posted for Grouse

The two plug in this pic or rear sealing plugs the one on the left looks like lukes plug.

Yes, the plug on the left is Bestils plug. The one in the middle is a NULA plug. Which is a smokeless ML.

 

[bestill]

clarification :
The plug on left is arrowhead sporting goods breech plug.
I use in all custom builds.

Bestill plug is a custom fit knight bolt gun breech plug not pictured.

 

[JStanley]

Rear has no issues with gas cutting like a front sealing plug. Also with machining a front sealing plug down in barrel at say 1.5" with small boring bar is much tougher than a rear sealing plug at say .5"

But the main reason is gas cutting.
Knight and savage are notorious for gas cutting front seal..
The rear seal will not cut also a perfect seal. Once a front sealing plug gas cuts it's a junk barrel typically barrel is softer than plug

Having done a little custom work by re-barreling a "rescued" gun, I can definitely testify to what you describe above about machining difficulty for the front sealing plug. Here's a question: if a person brought me a rifle, with mild gas cutting on the barrel/plug shelf and it was an open breech, slam-fire type, could I make a new, rear sealing breech plug for it if I maintained the proper head spacing & such? Slam fire guns have a bit of leeway built in with the distance of hammer throw and if the end result was good rear seal, good hammer/nipple contact, would that work? Would the gas cutting continue or would it stop where it is since a tight seal isn't being made on the bp face any more? Really interested in y'all's wisdom (apologies for any thread hijacking )

 

[Tannhauser]

I wanted to chime in and say this thread has provided some of the more interesting gun forum reading this year. I really appreciate the members who share their technical insight and experiences.

 

[Grouse]

Its all good stuff guys, feel free to post and ask questions. I like what Bestil is doing and support it.

 

[Grouse]

clarification :
The plug on left is arrowhead sporting goods breech plug.
I use in all custom builds.

Bestill plug is a custom fit knight bolt gun breech plug not pictured.

So which is better? The plug i pictured i thought was what you put in my Knight rebuild? I just bought an extra for back up for whatever reason.