I THINK I Can Make This

[gitano]

http://thehunterslife.com/forums/showthread.php?t=15614
Drop down to post #32 to see the appropriate pictures.

And I'm going to give it a try.

But not in .22 RF.

At the moment, I'm thinking .25 Hornet or .25 Remington Jet. Why .25 caliber you ask? Because I have a 21.5" barrel stub left over from a "gov't project". (Project halted by me because of stupid moron gov't reps.) That barrel stub has all the 'meat' necessary at the breech end from which I can machine the "receiver".

Why those cases? Because I'm looking for a reloadable cartridge with ballistics - both internal and external - on the order of a rimfire cartridge; ala the .22 WMR. This is a 'spiffy' little action, but it's not a STRONG, spiffy little action. .22 RF chamber pressure standard is 24kPSI. Both the Hornet and the Rem Jet chamber pressure standard is ~40kPSI, BUT... I don't HAVE to load to that pressure.

I am certain I can make every component, except one: The hammer. I have taken the "action" apart into its elemental pieces, and the hammer is the only piece that looks like a real challenge. The shaping isn't too intimidating, but the placement of the holes for the pins is extremely critical. Just not sure I can get that right the first - or even third - time. Maybe. Maybe not.

Another component that would be difficult for me to make would be the hammer kocking spring. However, there are lotsa black powder folks "out there" that can do that, and I will have one of them make it for me. It's possible, (I haven't checked yet), that Track of the Wolf (TotW) might have one in stock that I might be able to use or modify to use. At any rate, concern for getting that spring pales in comparison to the concern over making the hammer.

Not sure I'll make a trigger group. I was initially thinking I'd just use the existing group and the stock. However, if I'm going to the trouble to make the "barreled action", I might just go the whole nine yards and make a whole new rifle. Have to wait an see on that front.

I'm trying to think of ways to beef that breech up. As designed, the rearward thrust is held by the two screws in the 'ears' of the 'trapdoor-type' breech block. Larger screws and beefier 'ears' will offer some improvement. I can, of course crunch some numbers on 'bolt (breech) thrust' and get a mechanical engineer to provide specs based on screw diameter and ear thickness. But... I might just 'wing it'.

Anyway, I'll post everything about the build here in this thread.


Paul

[gitano]

https://www.trackofthewolf.com/Categories/PartDetail.aspx/0/1/LOCK-LR-1100-MS


Looks like TotW may indeed have something I can use. Keeping my fingers crossed.


Paul

[gitano]

The diameter of the rim of the .22 Remington Jet is 0.440". (Radius of 0.220".) Therefore, the area of the head is pi*0.220"*0.220" = 0.152 square inches. The SAAMI max pressure for the Jet is 40,000 PSI. Therefore, the MAXIMUM thrust on the breech face is 0.152 square inches*40000 pounds per square inch=6082 Pounds. So the design of the breech will have to be such that it can withstand 1.3*6082 Pounds=7906 Pounds. (SAAMI design specs require an action to withstand, without deformation, the max pressure PLUS 30% .) I'll round that to 8000 pounds. That is if I end up using the Jet case.

Doing the same math for the Hornet case, I get: 5442 Pounds of MAX thrust on the breech. Hmm...

Doing the math in the .22LR, I get: 1893 Pounds of MAX thrust on the breech.

So the original breech can absolutely handle something slightly less than 2000 Pounds of thrust. The Jet represents a 4-fold increase over that.  Hmm...

That is if I choose to load to max pressure. Which I never do.


Paul

[gitano]

Hmm... Been down this road before. "It's" coming back to me.

The. 25-20 is likely the perfect choice for this project. Its MAX breech thrust is 6655 Pounds.

Using the Hornady 75-grain V-Max, I can deliver 575 ft-lb, at an impact velocity of 1860 f/s, to 150 yards at a breech thrust of 4520 Pounds, with a trajectory of plus and minus one inch. That's 'only' 2.5 times what the .22 LR 'pushes' on the breech. The .25-20 is The One.


Paul

[gitano]

I'm getting carried away. Again. I need to put some design constraints on this thing in order to keep my eye on what I want this rifle to be. Namely: A reloadable, QUIET, 'garden gun'. I neither need, nor want, "maxes". So...

I think a 60-grain, Hornady FlatPoint is fine!
I think a .22 RF muzzle velocity in the range of 1200 to 1500 f/s is fine. Maybe, if I can pull it off, something subsonic like 950 f/s too.


Paul

[gitano]

It's got it's challenges, primarily head/rim diameter too small at 0.307/0.311 for a standard 0.373 bolt face, but the 5.7x28 does have the small RELOADABLE case going for it. Head/rim diameter is a moot issue in a falling or tilting block, OR the "action" I am contemplating making. So... It's between the .25/20, and the 5.7x28 case necked up to .25.

Paul

[gitano]

Some pictures for comparison. I didn't have a clue about the 5.7x28 until I found some brass at the range. (I have a dummy round already necked up to .25.)

Loading to 25,000 PSI (.22LR max pressure), yields MAX "bolt" thrust of 2405 PSI. Better than both the .25/20 and the Jet, even when both are loaded 'down'.

I am of course going to look at using the unmodified (.22 caliber) case. However, I don't imagine that I'll be able to get the MVs down in the 12-15 hundreds of f/s and still keep pressure up over 20,000. The pressure experience has taught that is required for sealing the chamber and getting CONSISTENT ignition. AND... I have the .25 cal barrel in hand.

.22LR, .17HMR, .22WMR, 5.7x28


5.7x28 with .223 Remington


Paul

[Jamie.270]

If you want to reduce the rearward thrust PSI even further, you might consider the .22 TCM casing.
It has a .376 base diameter.

[gitano]

While it seems somewhat counter-intuitive, the larger the head diameter, the greater the bolt thrust. Consider a head diameter of 1 square inch. The max bolt thrust would be equal to the max pressure. Now consider a head diameter of 0.5 square inches; max bolt thrust would be 1/2 the max pressure. Therefore, the larger head of the .22 TCM, (a cartridge heretofore unknown to me), would increase the bolt thrust over the 5.7x28 case, not diminish it.

That said, the "proper" nominal head diameter of 0.373" plus the small size of the case, makes the .22 TCM an excellent candidate for consideration for this project. Now I have to find cases.


Paul

[gitano]

You'll be shocked to find out that I did some number crunching with the .22 TCM. ��

Using a 57-grain Lyman cast bullet and 4 grains of Trail Boss, I get a muzzle velocity of 1400 f/s at a max chamber pressure if 23,000 PSI. That's basically identical to. 22LR internal ballistics. �� Except I don't like cast bullets.

So, using a 60-grain Sierra HP, and the exact same load, I get a MV of 1381 f/s, at a max pressure if 24,700 PSI.

Dropping the charge down to 3.8 grains, drops the max pressure to 22,800 PSI and the MV to 1343 f/s. Perfect! Looks like the .22 TCM might actually be THE cartridge for this build.

Given the 60-grain bullet, it's not exactly .22 rimfire performance, (it's better), but close enough. Change the bullet type to "spitzer" yields a little, (very little), better trajectory and better impact energy and velocity.

In a stronger action, the 35-grain V-Max can be driven to at least 3100 f/s. But... I dont need another "Hornet".



Paul

[gitano]

However! I've been down this 'low pressure' road, and the results were abysmal.

Paul

[Jamie.270]

You'll be shocked to find out that I did some number crunching with the .22 TCM. ��
Paul

Me?
Shocked by you, Mr "Paper Whipper" himself, crunching numbers?


HA!  Nevah!!!

[gitano]

Oh yeah... Forgot, temporarily, about the .25 caliber barrel - in hand. Which would require necking the TCM up.

Paul

[Jamie.270]

Oh yeah... Forgot, temporarily, about the .25 caliber barrel - in hand. Which would require necking the TCM up.

Paul

What is the bullet length/size limit, given this barrel's twist rate and the velocities you're looking for?

[gitano]

I'm pretty sure the twist rate is 1:10. I've been working pretty hard, (paper-whipping all design elements), on getting the velocity down to 1050 f/s. I'd settle for 1500-ish if I can't get slower. 1250 f/s would be OK. (Remember that I need to keep the max pressure down somewhere around 25 kPSI.) So... No trouble stabilizing a 60-grain .25 caliber bullet with a 1:10 twist. I haven't looked/calculated it, but I'm pretty sure I can stabilize an 80-grainer doing 1050-ish at 1:10.

I don't want to go above 60-grains, but I don't have any 60-grain .257 bullets in hand, and because the rat sons of bachelors bullet manufacturers that learned (from Barack Hussein Obama) that they could LOWER production, create the APPEARANCE of shortage, and thereby INCREASE PROFITS, there are NONE OF THOSE, (or any other for the most part), bullets to be had. I have some 75-grainers, and I have a mold that throws a 72-grainer (when gas check is included). You know what I think of cast bullets. :frown However, I think a cast 72-grainer doing 1050-ish might be exactly what I'm looking for. That is if I could hit the broad side of a barn with it. [/SIZE]

Paul

[gitano]

A 1:10 twist will theoretically stabilize a 100-grain lead bullet doing 950 f/s. With a little room to spare. And, by the way, I have some 50-grain FMJ bullets left over from the .25 ACP project, but they are only point two five ONE inches  in diameter.


Paul

[Jamie.270]

Hitting the broadside of that barn at any significant range is always tricky when you're flirting with trans-sonic velocities.  

Passing through that barrier is disruptive to any object's flight path, but from everything I've read, is exacerbated as the mass of the projectile is reduced.
Many air gunners have learned this the hard way.


I think if it were me, I'd try for even less muzzle velocity, (950?fps) unless the goal is just to consistently hit targets on the porch/deck.

[gitano]

I too have read quite a bit about the issues associated with bullets crossing the 'sound barrier', but I THINK that's a problem more for the benchrest crowd that are looking for microscopic precision at LONG ranges where small fluctuations in the bullet's path lead to unacceptable, to them, variance in the bullet's point of impact. I base that opinion on personal experience with .22 RF performance.

Part of the challenge is slowing the bullet down. At 1050, I'm already looking at charges in the 1 to 2 GRAIN, range. When you get down there, small changes make big differences, AND it's difficult to get the necessary precision in the charge weight.  Its MUCH easier to go up in MV than it is to go down. 1050 is on the ragged edge of what I think I can achieve in terms of consistent charge weight precision. 1250 f/s is "acceptable" because it is still typical .22 RF performance, but not particularly "quiet".

I have to frequently remind myself of my goal: To BUILD this rifle's action, (which happens to be integral with the barrel). I'm getting to the point of considering purchasing a .22 RF BBL. But then I'd be back at what to do with the .257 bbl?


Paul

[gitano]

Re "ranges of interest": I would want this thing to be a MOSTLY 50 yd and less cartridge, but have the energy and trajectory to make a 100 yd shot if I so chose. Kind of .22 WMR performance as a function of bullet diameter and weight, not velocity.

Paul

[gitano]

As is often the case when I get tired of speculating about this or that, I just go 'verify'. So, instead of continuing to guess what .257 bullets I have in hand, I decided to inventory exactly what I have.

At first I was a little surprised at the total count as well as the variety, but then I remembered that my youngest had done a "research project" in about the 8th grade in which she looked at bullet penetration based on weight, type, and impact velocity. Also, "you" may recall that I tried - in vain - to get the various .25s I have/had to shoot "slower". Lo and behold, I found a box of the 60-grainers that are "out of stock" on the planet! I also found a box of the gas-checked, cast 72-grainers. So I don't have make any more of those until I find out they actually work. Furthermore, I have three varieties of 60-grainers in "30" caliber, and I am most certainly not above squeezing bullets into the size I want! I might very well squeeze some of those .30 caliber bullets through some 7mm, 6.5mm, and .257 sizing dies.

I'm still considering buying a .251 barrel liner (at $6/inch ), IF I can get it in a "fast" - at least 1:12 - twist rate. That's a BIG 'if'. I would put it in one of my milsurp 8mm take-off barrels and use the .25 ACP case.


Paul

[gitano]

Correct that - $7.89 per inch! :angry:

17-incher costs ONE HUNDRED THIRTY-FOUR DOLLARS AND THIRTEEN CENTS! !@#$%^&*

And the twist rate is 1:14. I'll have to see if that 'works'.

Paul

PS - It appears that 1:16 twist rate will stabilize the 60-grainer. Therefore, the 1:14 should work.

Paul

[gitano]

Or... I could just give in and run the MV up to between 1500 and 2000, and have a reloadable .25 caliber "22 Mag". That's easy to do and keep max pressure below 25000 PSI. But it certainly wouldn't be quiet.


Paul

[gitano]

Just got a promo for .22 RF ammo, and was looking at Norma Match ("Elite Match Grade Long Rifle"). Published MV is 1082 f/s. I THINK if flirting with the sound barrier affected precision in RFs, "they" would stay away from it in "match" ammo.

Paul

[Jamie.270]

Just got a promo for .22 RF ammo, and was looking at Norma Match ("Elite Match Grade Long Rifle"). Published MV is 1082 f/s. I THINK if flirting with the sound barrier affected precision in RFs, "they" would stay away from it in "match" ammo.

 Paul

Could be I s'pose.
But, .22 rimfire matches are (for the most part) at 25 and 50 yds. At those ranges I doubt the trans sonic barrier would even be factor.
And even then, all the "match" ammo I've seen for the .22RF has been 40 gr (or more), which is a relatively long bullet for the .22.


Honestly, I THINK consistent velocity will likely be a bigger stumbling block than the sonic barrier, when it comes to developing acceptable precision, at shorter ranges anyway.



And if all else fails, there's always PCP airguns!

[gitano]

I had a substantial response, but because I do a lot of these on my phone, it went "into the ether". :angry:

I was cleaning my fort and found some 32 Smith and Wesson Long cases. Hmm... I wonder what one of these would look like necked down to .25? The answer is: Pretty much the same as the necked-up TCM case does. The TCM cases are easier to get. Not that that matters much, as I probably have a lifetime's supply (300) in hand.

I also discovered a bullet-maker called "Bear Creek Bullets". They make swaged, solid lead, coated, bullets for mostly obsolete cartridges. They make one 90-grain bullet in .258 caliber. That's heavier than I want, but at least they have them, and a significant number of people really like their bullets, so I'll probably get some. Everyone claims zero leading after thousands if shots. We'll see.

I think I have a pretty clear picture of the internal ballistics of the thing I want. Looks like it's time to start 'making chips'.

Paul

PS - For $.02, I'd put this whole thing on an AR.

Paul

[Jamie.270]

Well, I for one, am waiting with baited breath (so to speak) for the results of this endeavor.
So let the chips fly!

[gitano]

I have been distracted by another project. One everyone here will be keenly interested in, but I don't want to reveal the details now. When it gets 'locked in', I'll post what it's about here. I promise it will be interesting.

That said, I've got some machining I have to do for some repair work for the next few days. As soon as I can get started on this project, I'll post here.

Paul

[gitano]

The original barrel on the Stevens Model 15 is chambered for the 32 Long Colt, so I went looking for ammo. (Fat chance, right!) What I found was a guy that makes"reloadable" .32 LC cases. Sorta. What he makes is a brass sleeve into which you load a .22 RF BLANK or nail gun cartridge and a .311-.312 bullet,:mad: in the mouth. The 'blank' is offset so that the centerfire firing pin hits the rim of the blank, and that propels the bullet. Interesting solution. If I remember correctly, the cases are $3.50 each. That's not terrible, and I think probably fairly 'doable'. Here's an interesting note: OF COURSE you can't mail ammo unless you use UPS AND pay a HAZMAT fee. However, no such constraints on blanks! I just bought 100 rounds off of Amazon. I can make my own 'sleeves', but at $3.50 each, i might have to buy a few of them.

This doesn't negate the. 25 caliber project, but it does mean I might be shooting the Favorite sooner than later. I also just bought a .22 RF barrel for it, but I have to get a .22 ejector for it. The 32 Long Colt ejector doesn't work.

Paul

[gitano]

Hmm... I have a 1:9 twist, .223 caliber barrel liner 'left over' from when I made the 10/22 from the 80% receiver. (The barrel liner maker would not sell just 1 liner.) That liner fits almost perfectly in 8mm Mauser milsurp take-off bbls.

Consider this:
1) I put that liner in one of the MANY 8mm milsurp take-off bbls I have;
2) Chamber it for either the .22 TCM or the 5.7x28;
3) Stick that bbl on one of the two RB actions I have that are waiting for bbls;
4) Use Pyrodex RS BLACK POWDER substitute behind a Lyman gas-checked 53-grain cast bullet, for which I have the mold;
5) And get 1050 f/s muzzle velocity with that .22 caliber cast bullet without having to wildcat the TCM or 5.7x28 case up to .25 caliber. (In other words, not have to buy a custom reamer.) Furthermore, while staying well within the pressure specs of the RB, I could get a jacketed bullet up to .22 RF magnum velocities - (2k-ish).

Hmm...

Paul

[Jamie.270]

That oughta work.
If'n you don't care if it smokes a little.

[gitano]

This thing will be mostly for my grandkids. They'll have to put up with the smoke. Builds character. :D

Paul

[gitano]

I promised pictures of "chips" and here they are:
This is a 1.25" round bar mounted in the lathe and turned to 1.007" to match the breech diameter of the existing "Teutonic" Flobert.


This is the finished (turned) billet parted off and in my hand.


This is what happens when you THINK you have the work-piece held tightly in the soft jaws. No real harm done because damage was in area that is going to be milled away. However, since soft jaws clearly weren't going to work, I had to make some work-holding jaws.


The work-holding jaws being fabricated. They consists of two pieces of 1/2" aluminum clamped in the vise with a 3/4" piece of wood between them. (3/4" will be milled out of the round billet). Using a 1" mill, I milled/drilled down through the wood, but not out the bottom of the aluminum. That left a shelf for the work-piece to register against.


The work-holding jaws made.


Empty jaws before seating work-piece.


The billet in the work-holding jaws.


Milling 0.750x1.600 slot in the billet.


The milling finished.


A square 3/4" billet setting between the "wings" of the breech block.


This is a practice piece. Helps with determining proper order of operations, and things like "can't use soft jaws". Also, I haven't been "on the machines" for a long time, so this practice piece helps get back in the proper mindset for machine work. There's lots left to do with this breech block; drill firing pin hole, drill holes for screwing ears to "action", drill and tap firing pin retaining screw, round sharp edges, and "finish", but this is a pretty good start.


Paul

[gitano]

Got to spend 5 hours at the mill today. Yippee! Worked on the Flobert breech and made a 'blank-seating die' for the Stevens Favorite. I've finished the mill work on the breech. Now it's on to drilling, hand filing, and finishing.

Really glad I made this practice piece. Order of  operations seems straight forward, but there are a couple of places where 'out of order' snuck up on me. Didn't cause me to have to restart, but it did create extra work and some gymnastics.

I didn't get any 'work' pictures, but I'll post pictures of the completed, (for today anyway), pieces when I get them loaded on the computer.


Paul

[gitano]

Here are the promised pictures, but only of the modified .32 S&W Case "primed" by .22 RF blanks, and the die I made to seat the blanks in the modified case. I have to take pictures of the Flobert breech yet.

Here's the modified case from the side.


Here's the head. It's been drilled to accept the blank body, and milled to recess the blank head in the .32 SW head.


These are the blanks I'm using.




Here's the case beside the "blank seating die" I made.


The blank started in the modified case. The blank will not seat with finger pressure.


The blank, in the modified case, in the die.


Die, case, and blank in vise.


The finished, "primed" case.


You might wonder why I didn't just thread the die so it could be used in a press. Fair enough. The answer is that I only have 10 cases. I didn't want to go through the rigmarole of threading the die just for 10 cases.

So...

All the above 'fiddling' got me to thinking. Why not just do the same with the .257 barrel... Using a .25-20 case, there's no need for any mods other than modifying the .25-20 case to take the blank. Here's the big advantage: That blank is the "perfect" charge to keep the velocity down where I want it! You may have noticed, that the box of blanks I bought was for the highest power available. As you can see (if you look at the box), there are 5 levels down in power from these "purple" ones. So, test the purple ones; if the MV is too high, keep dropping back until I find the blank that provides the MV I want. The "four" (yellow) level (the recommended level by the guy that makes the modified cases), gives a MV of 850 to 950 f/s for his 100-grain .312 cal bullets. We'll see what the #6 (purple) blank does with a 72-grain cast bullet or a 60-grain jacketed bullet. The extra capacity of the .25-20 should moderate the MV a little. Like I said, we'll see.

The modified .32 cases cost $3.50 each. I can modify .25-20 cases for free excluding the cost of the cases. Furthermore, if I ever wanted to shoot .25-20 cartridges from the Favorite, (not likely, but possible), all I'd have to do is change the rimfire breech for the centerfire breech. (I have the CF breech, and will shortly have both.)

More when there is more.


Paul

PS -- Looks like no one is using the #2 and #1 blanks, so they're not available. But I ordered a box each of the #5, #4, and #3.

Paul

[gitano]

Here are pictures of the breech of the "Flobert" up to this point. It's still crude, (but not quite as bad as the pictures would indicate), but there's a great deal of "finishing" to do.









Here is the breech block for the Stevens Favorite. It started out as the breech for a .32 caliber RIMFIRE rifle. It was modified to CENTERFIRE. I am not going to change it back to RF. Instead, I am going to try to make a replicate, but in RF configuration. Since I don't have any steel plate that is 0.543" thick, (the thickness of the existing breech), I am going to use some 4140, 2" round stock I have. I had to use a grinder and cutoff wheel to take an inch off of the round billet. Since I will be milling this, and 4140 usually comes heat treated, I decided to anneal the workpiece first in a programmable kiln I have. I heated the piece to 1600F and held it there for an hour. Then, fairly quickly, (opened the kiln door), dropped the temperature to 1390F. Then programmed the kiln to lower the temperature to 1260F at a rate of 25 degrees per hour. (About 5 hours and 20 minutes). Then let it cool to room temperature over night. When I took it from the kiln, it was "softer". When I finish shaping it, I'll temper it by
1) reheating it to 1550F;
2) quench in oil;
3) then heat up to 400F;
4) hold it there for an hour;
5) then let it cool to room temp.

Here are annotated pictures of the existing breech.








The "chunk" in the kiln, but after annealing.


In the dividing head in vertical orientation. (It would be on a rotation table if I had one.)


You can see the scale on the "chunk". I got most of it off with a wire brush, but some of it was too stubborn. It doesn't matter because it's all going to be milled off anyway.


Paul

[gitano]

Work continues on two fronts: Flobert and Favorite. Here are some pictures of milling the replacement, rimfire, breech block on the Stevens Favorite.

This first picture is the 'chunk' clamped in the milling vise and milling off the first flat, (the top of the breech). Subsequent pictures will clarify.


This is the piece after that first milling, with the pattern I used on top so you can better see how the milling will proceed. The next picture will show the next flat to be cut.


This shows the next flat that will be cut. Once this flat is cut there are no more straight cuts. All subsequent milling will be performed with the piece in the dividing head so I can rotate the piece as needed.


There are four holes that will be drilled after the entire profile of the breech block has been milled:
1) Firing pin - not terribly critical in terms of positioning since nothing of the action will be rotating around the firing pin, and firing pin strike has a certain 'flexibility' regardless of centerfire or rimfire ignition.
2) Firing pin retaining pin - wide "room for error" in this hole.
3) Lever linkage pin - VERY critical placement relative to several faces of the breech block. Almost no room for error.
4) Extractor pin - VERY critical placement relative to several faces of the breech block. Almost no room for error.

I will use the existing breech block as the pattern for locating the critical holes.

I have a feeling that there will be more hand filing on this thing than I want there to be. That's another reason why I annealed it. Speaking of which, it ain't THAT soft even now!



Paul

[gitano]

In this installment, I have finished with the "flats". All of the rest of the surfaces are curved.



Here is the original breech block on the workpiece showing the relationships between the  faces that have been milled and those yet to be milled, as well as the holes.



Paul

[Jamie.270]

Too bad they don't make a pantograph work holder for a vertical mill!

[gitano]

Next installment of "making chips":

Getting started.




Getting finished.






Starting to resemble the original.


Paul

[gitano]

The profiling performed on the mill is complete.



I'll finish the profiling at the grinder.


Got the important holes drilled "to spec".


Here's the original on top of the new one positioned with pins in the holes to align them.


I still have to mill the groove, but that requires taking the workpiece out of the dividing head and positioning vertically in the vise. (Pictures will clarify.) Once the groove is milled, I'll drill the firing pin hole(s). Plural because there are two diameter holes; one for the pin itself, and one for the body of the firing pin captured inside the breechblock.

More later.

Paul

[gitano]

Next installment.

I started today by removing the excess metal that I used to hold the workpiece in the vise. This took a while.






Here's what it looked like coming off the mill and compared to the original.


The below picture is after a few minutes on the grinder. (The workpiece is adjacent to another breech block I got from Numrich.) I'm not finished on the grinder by a long shot, but the "rough edges" are ground off.


I can't decide, (don't know), whether to harden/temper before I mill the groove. If I harden first, I may have a difficult time milling. If I harden last, the "ears", (only an eighth of an inch thick and with a hole in the middle), may warp when I heat to 1600F and quench. (Then temper at 400 for a couple of hours, for a hardness of 55-60 Rockwell.) My "go to machinist guys", Jay Edwards, drinksgin, and j0e_bl0ggs, are gone. The only one left is Paul Hoskins.

Paul

[gitano]

In order to determine whether I should temper first then mill, (to prevent warping), or mill first then temper, (because breech would be too hard to mill after tempering), I took a piece of scrap from removing the breech from the workpiece, (see post number 41, third picture), and hardened/tempered it.

Into the kiln at 1600 degrees Fahrenheit, soak for 30 minutes, (1 hour per inch of thickness),  then quench in oil, then back in kiln to 450 degrees for two hours, then allow to cool to ambient in kiln overnight. Expected Rockwell hardness of 55-60.

Here's a picture of the kiln.


The "chunk" at 1600F.

Notice how you can see the heating element in the left wall of the kiln. You can't see that with your naked eye. That's because the sensor in the camera is sensitive to infra red. Lots of people don't realize that you can take "heat" images with most cell phone cameras.

After quenching.


It looks exactly the same after tempering, so no picture of that. I don't have a way to measure hardness, but this piece is "too hard" for my mill cutters. Which answers the question of "order of operations" with respect to milling and tempering.

I thought I MIGHT mill the groove, and then insert a piece of 0.250" bar in between the "ears", and then clamp them to the bar, but I don't have a clamp suitable for that, and I don't really want to try to make one. I'll just temper and hope for the best. After the groove is milled, the "ears" are only 1/8" thick.

So, left 'to do' are:
1) Mill "the groove",
2) Drill the holes (3 of them) for the firing pin,
3) Sand to final thickness,
4) Make firing pin and retaining pin
5) Harden then temper breech, firing pin, and firing pin retaining pin,
6) Grind breech to final shape.

While I was looking this post, it occurred to me that what I MIGHT do is get the 1/4" bar to put in the milled groove, drill holes in it to match the holes in the breech block, then use bolts and nuts through those holes to "clamp" the breech block ears to the 1/4" insert. That should/might prevent the ears from warping.

News at 11.


Paul

[gitano]

Apparently, the "purple pills" are too strong!




Here's the loaded round. Looks like I'll have to use the lower powered yellow or green versions of the .22 blanks. My breechblock actually fits the breech a bit tighter than the original, so it would have been a bit uglier yet with the original. Neither are "tight" against the breech. The issue isn't the breech block, as it has fairly tight tolerances on shape and size. The issue is the barrel breech. I could be back another 50 thousandths.


The loaded cartridge.


Comparison between my breech block and the original.








I thought I would be sanding for the final finish, but when I took it out of the kiln it had a very nice 'case coloring' and I didn't want to remove that. Therefore, mine is a bit 'scratchy'. I don't really care because I know what I could make it look like because I've done it before. I'm "happy" with this. It was A LOT of work! But then, making "one-off" items usually is.

It works and looks as good as the original. Not much I would change in the process. If I were to consider making more of them, I MIGHT ask a local CNC shop to shape the basic shape, and I would mill grooves, drill holes, and make the firing pin. The real time consumer and 'pain' was getting the fundamental shape milled.

I can't get my hands on the weaker .22 blanks until mid June.

Paul

[Jamie.270]

I'm trying to figure out how that case head ended up torn all to he!! and wadded up like that.



bummer.


Are you sure the bore isn't undersize somehow?

[gitano]

Sorry about the tardy response. Only excuse is "It's Springtime in Alaska!"

Re bore/chamber size:
Nah. I checked, (mic'd), before test-firing.

I think the 'purple' blanks are not for using in firearm. By that I mean that I know they are made for "nail guns", but they are really not intended for use in firearms. Why would you need a 'muscular' blank?

They MAY 'work' in the "Flobert" I'm making. (Yes, I'm still making that.) Given the potential cases I intend to use, maybe the extra case capacity will render the purple blanks useful.

I THINK I'm going to make my own .25-20 cases for the purpose of using the nail-gun blanks. The combination of larger case capacity, completely enclosing the blank in a close-fitting "chamber" within the fabricated .25-20 case MAY allow them to be used. One issue remaining is "headspace" - the fit of the breechblock to the breech. The "Flobert's" design does not ensure a tight headspace. The greater the headspace, the greater the chance that the purple blanks won't be able to be used. Just too powerful. Furthermore, the strength of the purple blanks may obviate their use because they propel the bullet faster than I want (subsonic). Time will tell.

Paul