Author Topic: .38/.357 prototype (Read 75041 times)

bruski · « **Reply #40 on:** June 06, 2018, 09:41:48 PM »

Well, from what I can tell so far is that the spring resistance is not a problem with a larger and heavier rotating mass. It must be like a flywheel affect going on or something.

If you look at the more modern Gatlings, they go both ways. The minigun firing pins don\'t move much more than a 1/4 of an inch or so and are automatic with the rotating bolt head that locks. When the bolt head rotates to the locked position, the firing pins are cocked compressing the spring then released then reset while unlocking and extracting.

I plan to remake some larger diameter bolts and try a different type of firing pin instead of using the mold ejector pins that I am using now. Not sure what, but they will be heavier like a AR-15 type or similar.

Bruski

Sparky_NY · « **Reply #41 on:** June 15, 2018, 07:31:26 PM »

Bruski, I like your bolt and feed pan setup but am confused about its geometry. Do you have any pics or drawings of the bolt and the carrier/pan? It appears to be a round profile bolt without the flats like the RGG gun design has, also the feed pan does not have any flats it appears. Cutter and I have been brainstorming ideas on bolts for a centerfire thus the questions.

Thanks !

George

bruski · « **Reply #42 on:** June 16, 2018, 11:25:20 AM »

HI Sparky,

There is no need for the flats on the bolts or pan area. The bolts are round and the ejector pin that protrudes up into the bottom of the bolts work as a guide and also the cam follower pins protrude upwards through a slot milled in the carrier. The cam followers are near the center of the bolts and the carrier slots are milled the full length up to the pan area.

bruski

Sparky_NY · « **Reply #43 on:** June 16, 2018, 12:01:19 PM »

HI Sparky,

There is no need for the flats on the bolts or pan area. The bolts are round and the ejector pin that protrudes up into the bottom of the bolts work as a guide and also the cam follower pins protrude upwards through a slot milled in the carrier. The cam followers are near the center of the bolts and the carrier slots are milled the full length up to the pan area.

bruski

Thank you !!! I am now clear on the subject. What was your end feelings on the follower near the center of the bolt, better than the end?

bruski · « **Reply #44 on:** June 16, 2018, 03:02:48 PM »

Yes, they seem to slide better with the follower in the middle area. The other reason for having them near the middle was to help keep everything shorter and lighter weight. The cam path on bottom dead center is almost up to the pan area.

bruski

Cutter · « **Reply #45 on:** June 17, 2018, 11:23:36 AM »

This is the 38 cartridge setting in a .625 bore/bolt

Any problems ??

bruski · « **Reply #46 on:** June 17, 2018, 12:44:25 PM »

Cutter,

The .625 seems large in the drawing, but it should work ok with plenty of space for a good extractor on top. The firing pin center needs to be raised up to the rim diameter center. The barrel chambers need a slight feeding ramp if anybody is going to use flat pointed bullets.

bruski

Cutter · « **Reply #47 on:** June 17, 2018, 12:59:01 PM »

Cutter,

The .625 seems large in the drawing, but it should work ok with plenty of space for a good extractor on top. The firing pin center needs to be raised up to the rim diameter center. The barrel chambers need a slight feeding ramp if anybody is going to use flat pointed bullets.

bruski

So, the firing pin would be offset

about .100 from bolt center ?

Cutter · « **Reply #48 on:** June 17, 2018, 01:28:17 PM »

It would look like this with a .0925 offset

bruski · « **Reply #49 on:** June 17, 2018, 03:42:58 PM »

That looks right.I think.

bruski

Sparky_NY · « **Reply #50 on:** June 17, 2018, 06:06:59 PM »

Cutter,

The .625 seems large in the drawing, but it should work ok with plenty of space for a good extractor on top. The firing pin center needs to be raised up to the rim diameter center. The barrel chambers need a slight feeding ramp if anybody is going to use flat pointed bullets.

bruski

If a feed ramp, even slight is put in the actual chamber, the cases will fire form to that shape, might even blow out the case in the area. (Saami says max chamber pressure for a 357 is 35K psi) This is why most guns have any feedramp prior to the chamber. I have discussed the feed geometry with Cutter. The common arrangement keeps the back of cartridge \"up\" due to the larger diameter of the rim and the nose of the round sits on the pan causing a tiltied down attitude as it enters the chamber rather than being in line with the chamber. It would be best if any type bullet shape could be used.

Its good to brainstorm some of these things before a problem shows on a completed build.

bruski · « **Reply #51 on:** June 17, 2018, 10:34:42 PM »

HI,

Cutter, were you thinking on a bolt with an offset turned on the front of it? Or keeping the .625 for the whole length of it?

bruski

Cutter · « **Reply #52 on:** June 18, 2018, 09:46:13 AM »

HI,

Cutter, were you thinking on a bolt with an offset turned on the front of it? Or keeping the .625 for the whole length of it?

bruski

Yes Bruski,

Offset through the whole length.

This is a preliminary drawing of a 5/8 bolt

Cutter · « **Reply #53 on:** June 18, 2018, 10:27:12 AM »

What I donâ€™t like about a larger bolt

with offset is too much wiggle room in the pan

RumRunr · « **Reply #54 on:** June 18, 2018, 05:02:03 PM »

From my experience, you want bolt face on center line with bore center. If having problem feeding round into chamber then not inline, causing binding. Just my .02

Are you thinking a feed ramp is needed?

bruski · « **Reply #55 on:** June 18, 2018, 05:51:54 PM »

The wiggle room might be a problem for sure. Remember the problems that I had with the .500 bolts and recoil bounce. What about a 7/16\" x 5/8\" rectangular bolt? The carrier and pan slots could be milled no problem.

bruski

RumRunr · « **Reply #56 on:** June 18, 2018, 06:06:23 PM »

Why not make the rounded portion on bottom a square and that way helps keep it rigid and still have room for pin ejector

Cutter · « **Reply #57 on:** June 18, 2018, 07:48:41 PM »

A larger 3/4 bolt with flats milled and

a .230 straight radius in the pan

RumRunr · « **Reply #58 on:** June 18, 2018, 10:13:20 PM »

Cutter- that is more like how I was invisioning it.

Or you could keep radius square and use it as guide and keep it short to go around/over pin

RumRunr · « **Reply #59 on:** June 18, 2018, 10:14:45 PM »

So what about a thicker barrel plate with a feed ramp milled in? To help with loading cartridges..

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Author Topic: .38/.357 prototype (Read 75041 times)