.38/.357 prototype

[bruski]

Sparky,

 I made two more bolts that are centered and the only thing that is bothering me now is the fact that my head space has to be practically zero for all of my extractors to function properly. This is with dummy rounds in the chambers. I realize that after firing the cartridges they should be well seated under the extractors but what about a misfired cartridge. I know from experience that this will haunt me during testing even though there is no reason for any misfires. The extractors that I used are as hard as a rock so filing won\'t work. Maybe a cut off wheel in the Dremal tool will work if needed. It is difficult for me to work with tiny parts with my handicap so I think that I will test first before screwing up anything that works.

 

 The housing is still a problem. This prototype will function without a housing though. My rear end cap is countersunk into the cam on the back end so the shaft is supported by a bushing in the rear and head space is adjustable with two jam nuts in the front and two in the rear.

 

  bruski     

[Cutter]

Going to ease back into this build, starting with Cams.

At 60 degrees the cartridge will be .500 into the chamber keeping ti in place at firing

[Cutter]

Bruski,

I’m planning on a stiff spring in the recoil unit to allow some blowback.

That should give the extractor a full grip on the casing , an at the same

time eliminate those close tolerances.

Also, a misfired cartridge should pull out easier than an expanded shell.

[bruski]

Cutter,

 The stiff spring is a good idea. I will try this with a spring around the front shaft between the front barrel plate and the back side of the frame  bushing in the front.

 

bruski

[Sparky_NY]

Stiff spring allowing some blow back has possibilities but is getting into a potentially dangerous area also.     A 357 runs around 35,000 psi chamber pressure and IF the case blows back more than just a few thousandths, the danger of a case wall rupture is likely.      Case wall ruptures are NOT a pretty thing and very dangerous.     Even a 22 will blow out the wall if not fully supported by the chamber.    Semi autos commonly have the bolt locked until chamber pressure decreases then unlock and the spring takes it from there, so the bolt is locked during peak chamber pressures. 

 

I would guess that a blow back amount equal or less than the length of the relief groove just ahead of the rim would not be a problem, but that is just a guess.

 

Just something to consider.

[Cutter]

Stiff spring allowing some blow back has possibilities but is getting into a potentially dangerous area also.     A 357 runs around 35,000 psi chamber pressure and IF the case blows back more than just a few thousandths, the danger of a case wall rupture is likely.      Case wall ruptures are NOT a pretty thing and very dangerous.     Even a 22 will blow out the wall if not fully supported by the chamber.    Semi autos commonly have the bolt locked until chamber pressure decreases then unlock and the spring takes it from there, so the bolt is locked during peak chamber pressures. 

 

I would guess that a blow back amount equal or less than the length of the relief groove just ahead of the rim would not be a problem, but that is just a guess.

 

Just something to consider.

 

 

Good point Sparky,

My plan is to have an adjustable recoil unit.

My extractors would need about .020 for a full grip.

 

One size will not fit all extractors.

[bruski]

The total amount of blow back can be adjusted with the head space nuts on the front of the shaft if you place the spring around the shaft behind the bushing and in front of the barrel plate nut. If the thrust bearing in front starts to get pounded to much, then a bronze thrust washer could replace it or even some sort of soft buffer washer.

 

bruski

[Cutter]

The total amount of blow back can be adjusted with the head space nuts on the front of the shaft if you place the spring around the shaft behind the bushing and in front of the barrel plate nut. If the thrust bearing in front starts to get pounded to much, then a bronze thrust washer could replace it or even some sort of soft buffer washer.

 

bruski

 

I like that Bruski, much simpler than what I had in mind.

[Sparky_NY]

Got the frame rails and front piece all made up (free 304 stainless).    Cut the housing tube to length (brass pneumatic cylinder), made the rails, slotted the housing and silver soldered the rails in.    Its beginning to look like a gun !     Surprising how it looks like the rendering I posted earlier.

 

Next... have to drill some holes in the frame rails and tig weld the front cross piece into place.    Then I need to make up the mainshaft.

[bruski]

Looking good Sparky, very nice indeed.

 

bruski

[bruski]

Cutter,

 Your cam plan should work perfectly for the cams on this gun.

 

bruski

[Sparky_NY]

Cutter,

 Your cam plan should work perfectly for the cams on this gun.

 

bruski

From Cutters previous posts I also \"advanced\" the cam timing.   Can\'t say without looking but my bullet nose is started into the chamber at about 2:00 position.    I did similar advancing the eject side to get them out a bit sooner too. 

[Sparky_NY]

wonder if you guys noticed???    SAAMI drawings for both 38 and 357 do not show the recessed groove around the case, right at the rim.   All the brass I have as well as some factory ammo ALL have that groove.  

 

Considering that recessed groove is NOT supported by the chamber in ANY gun, I believe it would be safe to relieve the barrels in that area for the extractor to engage the rim without any concerns of case blowouts.    That is provided the relief does not extend and further forward than the area of the cartridge groove.    

 

At least I sure hope so !      I relieved that area on my gun for deeper extractor engagement on the rim in battery position,  but no further forward.

[Sparky_NY]

These 357 gatling guns should have quite a bit higher velocity and thus power than a 357 pistol because of the 18 inch barrels.    Ever wonder how much faster / more powerful       Here is a article that answers the question.   The difference is AMAZING !      

 

https://www.thetruthaboutguns.com/2011/05/chris-dumm/lever-action-ballistics-30-30-vs-357-magnum/\'>https://www.thetruthaboutguns.com/2011/05/chris-dumm/lever-action-ballistics-30-30-vs-357-magnum/

[bruski]

I have a chronograph to measure the bullet speeds. I plan to find out for sure how fast they are traveling at about 5 or 10 feet from the muzzle. If I don\'t blow the sh#t out of it first.

 

bruski

[bruski]

Just for kicks, I have a Rossi lever action that shoots 38 special or .357 magnums to compare it too.

 

bruski

[Sparky_NY]

Just for kicks, I have a Rossi lever action that shoots 38 special or .357 magnums to compare it too.

 

bruski

Should be near identical.     I was quite surprised at how much more poop the longer barrel makes compared to a pistol.  

 

  I am anxious to see how the bruce feed works out,  that will be great.  I wonder if with a longer section of single column at the bottom and taller double stack if 100 rounds would be possible???    Maybe 40/40/10 as a guess.

[bruski]

I clocked some 158 grain Flat Point lead semi wad cutter 38 specials today with the Rossi lever action and they averaged 1335 FPS at 15 feet away from the muzzle. More to continue on the 357\'s which I am reloading now. The big boxes of cartridges that I posed a while back are all 38 specials.

 

bruski

[Cutter]

Received my brass today, 4” diameter $$

Have to give up beer for a day  

[Sparky_NY]

 

Received my brass today, 4” diameter $$

Have to give up beer for a day  

 

Hope you didn\'t pay the big bucks for it.   A guy on ebay has 4\" rounds in many lengths.    I got a 4\" round 4 inch long for $60 with free ship from him.

 

Thats STILL a lot of money,   geesh brass is expensive now,   all metals for that matter.