Crosman Breech/Barrel Thoughts

[YEMX]

I think I posted about this before, I just can't find the thread...  I like how the Crosman 1400 is set up w/the single piece breech/barrel...  I'd like to do something similar, but how feasible is it?  Would anyone be willing to give it a go?  I'd have to figure out a spacer (not sure if I could use a repro of a 1400 one...) for sure...  Basically, I'd want it set up to go on top of a Disco type tube...  Not sure why I want to do this so bad.  I guess I just like the idea of the barrel and breech as a single unit. 

Here's the idea:

1 piece .25 (or .257?) barrel/breech.  Threaded for LDC
Disco-type tube from Don Cothran
Cothran powerhouse valve
Cothran rear cocking piece

Probably a Mrod trigger with a RAW trigger blade, unless I still have that Rowan Engineering trigger somewhere.  Everything else is up in the air.  I kinda want to do a scout rifle build... 

So... Thoughts?

[AmBraCol]

Here's the idea:

1 piece .25 (or .257?) barrel/breech.  Threaded for LDC
Disco-type tube from Don Cothran
Cothran powerhouse valve
Cothran rear cocking piece

Probably a Mrod trigger with a RAW trigger blade, unless I still have that Rowan Engineering trigger somewhere.  Everything else is up in the air.  I kinda want to do a scout rifle build... 

So... Thoughts?

Sounds like fun.   

[Blutroop]

I think the biggest problem will be getting the chamber and lead just right since you’ll have to ream past the part of the barrel for just the bolt. That and I wouldent want to pay extra for a longer barrel just to bore out the breech area for a bolt. I must admit though after having my 2nd version 180 I have had the same thought from time to time. I’m just to spoiled with my magazines and repeaters.

[YEMX]

I think the biggest problem will be getting the chamber and lead just right...  That and I wouldn't want to pay extra for a longer barrel...  I’m just to spoiled with my magazines and repeaters.

I was thinking the same- about both the chamber and the longer barrel...  But I think that maybe the rigidity gained by a larger diameter barrel/breech might be worth it?  I've always been a fan of single shots...  Less to break/lose 

[Ribbonstone]

Likely other ways...."we" as airgunners tend to stick with what worked for us and are hesitant to un-do what we found worked in orderto try somethng else.

I've had  very good results when tagging down the breech end with a barrel-band.  be screw set ot shim set, so long as it is a firm fix "down".


Idea is to make that horrid little front breech screw superfulus (doesn't really mattter if that little-bitty screw is in or out...althought I keep it in place as an "extra").

NOT an orginal idea...it'spretty much how Crosman makes the Challenger PCP.


LOnger barrels (like the Disco or any long-barrel 22XX conversion) willlikely get a 2nd barrel band out towards the end of the gas tube.

Shorter barrels (like the 10-14"pistol barrels) willbe let go as "freefloats"..same diameter,but shorter is stiffer.


If you guys have a better idea, I'dlike to hear it.

[Blutroop]

I’d be tempted to weld a extension onto a barrel rather than machine one down. I’ve also thought a lot about the 1389 or 250ssp load gate arrangement. 1389 backpacker was my first air rifle so I may be biased.. but I have been curious to see how much power you can put through one without blowing the load port open.
P.s. I have a 26” TJ’s .257 1-10 twist if you wanna do some swapping.

[YEMX]

Ribbonstone- I do agree, I could solve the perceived (or actual?) rigidity issue w/the tried and true method of adding a second barrel band near the breech.  Although, I've wanted to take it a step further and use a 2250 barrel band, modify it to take a Disco stock lug, use a 2nd stock bolt and pillar bed the 2nd stock mounting point.  Overkill and probably not necessary at all.  Just a "what if" kinda thing.  I do plan on incorporating this second stock mount/barrel band in this build- if I ever get it going. 

Blutroop- I saw your for sale/trade ad a little while ago for that barrel...  I certainly wish I had something to trade, or spare monies to buy it!  I also have thought about a SSP 250 type loading gate for .25 or rather, 257...  But honestly, that would be a lot of work, and those loading gates didn't particularly seal well if my memory serves me.  The SSP 250-type loading gate being blown open under this much pressure is also a concern for me...  I'll leave that idea as a bench build...  It certainly would be cool though, wouldn't it?? 

[CraigH]

It would certainly be rather more of a challenge, but the machine work is possible.

Airguns with the separate breech and barrel construction can be improved in various ways - barrel bands, more of the grub screws ( ), threaded barrels.   Of these the last is certainly the most rigid.

I also prefer the unit construction of the later variant Crosman 150, 180, and 1400.

[YEMX]

Hmmmm...  I'm really leaning towards finding someone who is willing to give this one-piece breech/barrel thing a go...  The little grub screw would probably be eliminated in this build, considering I wouldn't have the breech/barrel clearanced for the main tube- I'd use a spacer.  Although, If I DID clearance the breech/barrel and use a .5" OD barrel... Hmmmm...  Anyone know the OD of a Crosman steel breech?  Although, would .5" OD be enough to thread the muzzle end for an LDC?  Or perhaps machine in some dovetails?  Maybe I can finally build my iron sight/LDC quieted dream gun finally... HHHMMMMMMMMMM...   

[YEMX]

blutroop- your inbox is full... I tried PM'ing you

[happymecanic]

Start with a 9/16'' or 5/8'' OD barrel, have a bolt and barrel leade made in the Crosman 140/1400 style (bigger 5/16'' bolt). An advantage I see is that the breech screw is not in the pellet channel. Also you only ''lose'' about 3-3 1/2'' for the breech making it this way. You could have a dovetail rail cut with that size of barrel. BTW I measured the Crosman steel breech OD at 0.745'', so nominally 3/4''.

Using a big OD barrel also gives more rigidity for sealing well, there's ''meat'' to machine a nice TP seat and port, and threads for an LDC. I think I saw chamber reamers on Ebay or Amazon that will easily go 3'' to 4'' deep. You just need to index the bore of the barrel in a 4-jaws chuck to do a good job, and the TP and breech opening are simple milling operations.

I think money-wise it's realistic, you don't need to buy a breech, and the machining costs shouldn't be too high. You also get a simple and reliable loading system, with excellent accuracy and power potential. I'll follow this thread, and wish you good success with this project!

[Ribbonstone]

The other thought is even simpler:  Why?

Why not borrow something from the old Benjmain/Sheridan designs.   Let the bolt be able to be removed from the back, the barrel removed from the front, let the bolt carry a removable pin to cock a pinless striker, and let the breech be "forever" joined to the air tube?

NOT the soldered on barrel of a Benjamin/Sheridan....today's airgunners wouldn't put up with that....but a permanent breech, either made in one piece or attached.

Can think of several airguns that have welded on trigger housings....we kind of accept that so long as we can get the "guts" out when needed.

Does defeat the tinker-toy parts swap of Crosmans....but it would certainly be a stable breech...with a removable bolt and barrel, could still caliber-swap.

[YEMX]

Start with a 9/16'' or 5/8'' OD barrel, have a bolt and barrel leade made in the Crosman 140/1400 style (bigger 5/16'' bolt)...  you only ''lose'' about 3-3 1/2'' for the breech making it this way. You could have a dovetail rail cut with that size of barrel...  the Crosman steel breech OD at 0.745'', so nominally 3/4''.

Using a big OD barrel also gives more rigidity for sealing well, there's ''meat'' to machine a nice TP seat and port, and threads for an LDC...  I'll follow this thread, and wish you good success with this project!

Thank you for the measurements- I estimated about the same length of 3.5", measuring off a Disco tube, and a breech for the Disco.  You hit the nail on the head sir!!  Your entire post is what I have in my head.  I think I'm going to give this project a go...  I'm going to have to sell some stuff though, as this project will take care of 2 projects for me.  Which is fine.  So preliminary parts and thoughts:

-  5/8" 1-14 TJ barrel.  Not sure on length yet, but I don't think a 28" barrel (not including the breech section) would be too bad in this case.  I wonder if Mr. Cothran can make a longer reservoir?  I've already sent an email to him about this.  Very seriously considering having short sections of dovetail machined in for iron sights (peep rear, globe front).

-  5/16" bolt, o-ring on bolt

-  Cothran Powerhouse valve

-  Cothran rear cocking piece

-  Cothran main tube- no gauge (I won't be getting very many shots, so no REAL need to have a gauge, plus I'll be shooting tethered if I want to shoot longer...), probably no baby breech screw either

-  1400-type spacer, I don't want to machine a groove on the bottom of the breech/barrel. 

-  3 barrel bands- 2 that are larger 22xx looking bands, one that's a larger 2250-type band for use as a 2nd stock mounting point.  Not sure why I want this 2250-type band so much.  I just do.  thoughts on the number of bands?  I was thinking 1 near the trigger group (standard type), 1 near the end of the stock (2250-type) and one at the front, behind the fill adapter... 

-  Mrod trigger (Gen 1 of course, to work w/the Disco)

-  Have a scout scope mount made, in the same fashion as a Air Venturi mount.  I'll probably end up re-using the scope rail, as it's just the clamps (rings?) that won't fit the barrel... 

So... Thoughts?

[YEMX]

I'm thinking I'm also going to have the bolt slot and chamber machined in such a way, so that the bolt will fully seat the slug, but retract a bit to clear the TP.  Kind of like a J-slot, but more simple...  Would that even work?  The slot could be lengthened to the rear to make sure the loading port is clear for the slugs... 

I did some preliminary measurements, I'm going to keep the Disco tube at the same length, but no gauge and no 4-40 breech screw.  The barrel will be 32"+ for finishing purposes and threading, that'll net me right at or just under a 28" barrel.  The additional barrel length past the dust cap will allow me to use a Clague reflex LDC, which slides over the barrel to allow for additional volume thus making the rifle a touch more quiet.  Not sure how quiet a 100+ fpe rifle is going to be though...  I'm sure Mr. Clague will build something quite suitable for this build- he's never failed to produce astonishingly quiet LDC's in the past 

Now I'm going to have to go through my builds and figure out which one's/which parts I'm going to sell off... 

[Gippeto]

  Kind of like a J-slot, but more simple...  Would that even work? 

In a word...no. Insufficient material.

T shape might be possible, where you can pull back and then lock the bolt. Bolt opening/flopping around WOULD be an issue though, need to add a locking method...spring ball/detente might work, but not a lot of room for that either.

Problems have solutions, but solutions are rarely without their own problems...it's a vicious cycle lol.

Al

[YEMX]

  Kind of like a J-slot, but more simple...  Would that even work? 

In a word...no. Insufficient material.

T shape might be possible, where you can pull back and then lock the bolt. Bolt opening/flopping around WOULD be an issue though, need to add a locking method...spring ball/detente might work, but not a lot of room for that either.

Problems have solutions, but solutions are rarely without their own problems...it's a vicious cycle lol.

Al

I have a hard time explaining what's in my head...  Here's a drawing, such as it is...


The rifle will have a rear cocking device, so the bolt won't be cocking the gun.  That'll clear up the bolt slot in the rear, so I can retract it far enough to clear the loading port.  I hope the drawing is good enough to get my idea across.  Of course, I could still be off the mark.

The other thought is even simpler:  Why?

Why not borrow something from the old Benjmain/Sheridan designs.   Let the bolt be able to be removed from the back, the barrel removed from the front, let the bolt carry a removable pin to @#$% a pinless striker, and let the breech be "forever" joined to the air tube?

NOT the soldered on barrel of a Benjamin/Sheridan....today's airgunners wouldn't put up with that....but a permanent breech, either made in one piece or attached.

Can think of several airguns that have welded on trigger housings....we kind of accept that so long as we can get the "guts" out when needed.

Does defeat the tinker-toy parts swap of Crosmans....but it would certainly be a stable breech...with a removable bolt and barrel, could still caliber-swap.

How did I miss this post?!  Anyoo, you're not wrong...  There's no real reason to do things this way, other than I want to... 

The breech section will be very similar to a QB- bolt handle will slide into the bolt, secured with a screw, and the rear will be capped off, with the screw to anchor the rear cap doubling as the main tube cap anchor screw- did that make sense?  Ugh, I wish I were better with explaining things    Again- the bolt is not cocking the rifle.
 I will be using Cothran's rear cocking set up.  Again, you're right, building the gun this way will not retain the "Lego" feature of current Crosmans, however- that's not the point of the build.  Although, you're right- caliber changes would be quite simple...  Expensive, but simple.

[Ribbonstone]

Always thjought this was a particulary simple system.

Spring latch in a T-bolt, straight back motion, locks into a circular depression when forward.

[Gippeto]

Another option that doesn't require room to rotate the bolt... this on my .30. Collar is spring loaded and snaps into a recess in the receiver, locking the bolt. If needed, can carry it right through the receiver and have a pin in double shear.

Saw this arrangement first on an airgun from the Philippines, and like the simplicity.



Al

[CraigH]

Another option that doesn't require room to rotate the bolt... this on my .30. Collar is spring loaded and snaps into a recess in the receiver, locking the bolt. If needed, can carry it right through the receiver and have a pin in double shear.

Excellent design - I like it.   

[YEMX]

Another option that doesn't require room to rotate the bolt... this on my .30. Collar is spring loaded and snaps into a recess in the receiver, locking the bolt. If needed, can carry it right through the receiver and have a pin in double shear.


Al

Oh, I like that too- I assume the knob is sitting in a recess in the forward position?  Also assume the knob is pulled out, then pulled back?  I do like that idea!!