Revisiting 6mm LONG build

[YEMX]

When you say 25 cal insert, is this something you custom made? 

If it is the adapter Don designed to make the Cothran drop in a Marauder, it has a pretty small transfer port   and will significantly limit performance.....

I didn't make it- it's part of the insert Don makes with this Cothran valves...  I'll have to measure it... Hang on a minute

[YEMX]

If it is the adapter Don designed to make the Cothran drop in a Marauder, it has a pretty small transfer port   and will significantly limit performance..... I do not believe that would fit in an unmolested breech

You are absolutely correct.  I'll have to pull that collar out and make a new TP w/full .250" porting.  GAH!  I should have remembered that- I've been away for too long...  Good catch!  I would have noticed it later, but it's better to catch this stuff early on!  Much appreciated!

Oh- the breech is getting modified.  I'm sinking the sleeve over an inch into the breech, and I'll of course have to make the TP hole larger to match the new, larger TP. 

[YEMX]

I always do this back and forth on my projects!!   

Okay.  After some more planning, and measuring and shifting other project plans around, I've FINALLY decided on what direction I'm taking!  LOL

Full length Mrod tube
700cc bottle (yes, it fits!)
29" barrel

I'm still working on the reverse bottle adapter.  I'm dedicating my efforts to getting this piece done first.  It's pretty much the only thing that this project hinges on, so it needs to be done right, and first.  I've got the drawing done, and I'm about to send everything off to my machinist friend.  I'll update when I have something new.  Hopefully that'll be when I have a completed reverse bottle adapter! 

[Scotchmo]

Both of my Armada bottle builds use rear bottle connections between the gauge port and a fill adapter on the regulator. You can use a 1/8 npt nipple. It’s simpler than making a reverse (forward) bottle adapter.

[YEMX]

That's an interesting use of an ASA!! 

[YEMX]

Here's some progress pics of the reverse bottle block:





I tried to copy the RAI block, and have a 1/8" gap between the Mrod main tube and the bottle.  The second pic is a mock up on a spare tube- not at my house, everything is still with my machinist buddy.  When I get the block and bottle back, I'll get it all together and do a leak down test.  Once it passes, I'll be getting the breech modifications squared away and get the barrel machined and assembled.  We're getting closer!!

[bear air]

That reverse block is awful purdy!!!! Very nice.

[Spin]

CARM already makes .25 cal FLEX / WARP mags so a .243 would think so close it would be doable.

Yessir- it's just the length of the slug- these Arsenal Bowman slugs are a HAIR too long.  I'll see if he can play around with the thickness of the face plates, w/o screwing with the exterior dimensions.
[
Shim it! You can buy precision shim stock easy enough/quote]

[mackeral5]

Here's some progress pics of the reverse bottle block:





I tried to copy the RAI block, and have a 1/8" gap between the Mrod main tube and the bottle.  The second pic is a mock up on a spare tube- not at my house, everything is still with my machinist buddy.  When I get the block and bottle back, I'll get it all together and do a leak down test.  Once it passes, I'll be getting the breech modifications squared away and get the barrel machined and assembled.  We're getting closer!!

Looks great, definitely worth the wait!!!!!  I must add that I have not seen many things that made me a bit envious of the owner, this is one.  You've had many cool builds, but this one truly stands out to me.

[YEMX]

Shim it! You can buy precision shim stock easy enough

The opening in the breech isn't long enough to fit a magazine for these 6mm slugs.  I'll revisit it down the road (just to be sure), but I'm pretty sure this will be a single shot only rifle.  Which I'm fine with.

[YEMX]

That reverse block is awful purdy!!!! Very nice.

It really IS a nice block!  Matt really did a banger of a job on this!  Especially given my pretty awful drawing!  LOL 

[YEMX]

Looks great, definitely worth the wait!!!!!  I must add that I have not seen many things that made me a bit envious of the owner, this is one.  You've had many cool builds, but this one truly stands out to me.

Thank you!  This reverse bottle adapter definitely IS worth the wait!

The next bottle adapter idea is gonna be a hoot (nothing crazy though).  I had you and Chris in mind when the idea popped into my head, due to y'all's work/interest in 9mm Brods.  I got the idea from Monkeydad1969 initially...  If it gets made, I'll be sure to see if y'all are interested...  Oh!  I just had another idea!  LOL  Gotta send a PM off!

[YEMX]

No real updates.  Life is getting in the way.  Still going to finish this build, don't worry!  Two small changes:

-  I'll be shortening the tube (plenum), it doesn't need to be this big for 6mm anyway.  The original idea was to use a full length Mrod tube.
-  I'll be using a 500cc bottle, and an adjustable Ninja reg from Hajimoto.

The shorter plenum also opens up the opportunity to  have more space for a reflex shroud, so at the very least I can have a *potentially* quieter gun, which is ALWAYS appreciated. 

Anyhoo, updates as they come.

[YEMX]

The main tube and new Ninja Flex bottle are with my machinist, rough SWAG measurement, the Mrod main tube will be shortened by 3", which will make for a pretty large plenum!  I'm stoked. 

Reverse bottle adapter block will now include a boss to mount a barrel band. 

[Scotchmo]

The main tube and new Ninja Flex bottle are with my machinist, rough SWAG measurement, the Mrod main tube will be shortened by 3", which will make for a pretty large plenum!  I'm stoked. 

Reverse bottle adapter block will now include a boss to mount a barrel band. 

You’ll end up with about a 170cc plenum. Plenty big plenum for a high power 6mm. What slug/velocity/fpe are you planning on?

[YEMX]

The main tube and new Ninja Flex bottle are with my machinist, rough SWAG measurement, the Mrod main tube will be shortened by 3", which will make for a pretty large plenum!  I'm stoked. 

Reverse bottle adapter block will now include a boss to mount a barrel band. 

You’ll end up with about a 170cc plenum. Plenty big plenum for a high power 6mm. What slug/velocity/fpe are you planning on?

The slug will be a HP version of the Arsenal 6mm Bowman mold.  I've also got an unmodified mold.  With a 24" barrel, I think Bob's calculated theoretical max is 140 fpe?  That's my goal- or as close to it as possible.  I believe the solid slugs are 60 grains, with a HP, I have no idea...  Less than 60 grains LOL  I think I'll either use a 26" or a 28" barrel.  I'm leaning towards the 28" length.  I think I had a 24" long barrel before, with a standard Brod, and I was only making around 100 fpe at 2800 psi (I think)... With a 20" barrel, in an AF platform, I was doing about 90 fpe.

[Scotchmo]

Why hollow point?

For high FPE, 28” definitely better than 24”. If going with a TJ, I’d go at least 36”. You can always cut it later if you don’t need the FPE.

[YEMX]

Why hollow point?

For high FPE, 28” definitely better than 24”. If going with a TJ, I’d go at least 36”. You can always cut it later if you don’t need the FPE.

I'm more than likely going 28".  I'll be using a TJ, but definitely not going longer than 28" final OAL.  This will have an LDC on it, anything longer than 28" will be ungainly.  At least to me. 

HP is mainly to see if/how much it'll expand but also to see how lighter slugs will do.  If they'll expand, I feel like  this 6mm will be pretty devastating on targets. 

[YEMX]

Well, slight change...  This will have a 26" or slightly shorter (longer than 25" for sure) barrel.  I did a little change with another project and will have a 26" blank to work with.  Which is good, because I've already spent the money on the blank LOL  So the Brod won't be getting as much power as it could be.  But honestly, anything over 100 fpe will be fine with me.  For this build anyway.  This build is more like my white whale than anything else.  It's the build that started the whole 6mm craze for me (Thanks Bob!!  LOL), and I never did build one that I was completely happy with...  But that's the only major change for now.