A 25 Cal Fortitude

[FuzzyGrub]

Is there any reason to use stainless as opposed to brass? The brass may be easier to  work with. 

I am curious as I have never done this before, and will likely be modding a .22 bolt for use in a .25 in the near future.

The SS was the only option I found that had a thin enough wall.  at least at McMaster-Carr.

Update: OK, see some under "structural tubing" that may work.

[screwwork]

John,

You could sleeve the barrel with .5 OD x .032 wall tubing may be about 0.09 long to get better barrel to mag alignment?
Sleeving the bolt, Brass or SS wouldn't matter. Brass is easier to work with.
I don't see a need to sleeve the probe for better pellet loading.

[mackeral5]

Is there any reason to use stainless as opposed to brass? The brass may be easier to  work with. 

I am curious as I have never done this before, and will likely be modding a .22 bolt for use in a .25 in the near future.

The SS was the only option I found that had a thin enough wall.  at least at McMaster-Carr.

Understood I see you are needing .010 vs .014 wall.    This is helpful for me to think about my project.  I may be tempted to turn the probe down with fine sandpaper and go for a tight press fit...

For future reference, I buy all of my k&s brass hobby tubing through Amazon prime, typically cheaper than Mcmaster.

[FuzzyGrub]

Actually, that SS tube may be too loose with the nominal 0.010" gap.  Good catch.  This one is probably too tight and would require some bolt machining: https://www.mcmaster.com/6100k191


Here are the two I found in brass:

Bolt: https://www.mcmaster.com/8859k24

Probe: https://www.mcmaster.com/8859k21

I prefer McMC for researching the specs.  On Amazon, it depends on the particular seller what is listed.  The brass are much cheaper than the SS.  Do you know if there is a inner welded seam on brass?  or is it smooth, ie drawn?

[FuzzyGrub]

John,

You could sleeve the barrel with .5 OD x .032 wall tubing may be about 0.09 long to get better barrel to mag alignment?
Sleeving the bolt, Brass or SS wouldn't matter. Brass is easier to work with.
I don't see a need to sleeve the probe for better pellet loading.

At this time, until I find there would be an issue, plan to bore the breech through the full 1/2" and just notch the barrel at those mounting screws.  That would allow the barrel to still be useable on a Mrod, if things change in the future. 

I agree with you on the bolt probe, but it seams like it would be easy to do, and wouldn't make it worse.  I'll probably order the tube and make final decision latter. 

[mackeral5]

Actually, that SS tube may be too loose with the nominal 0.010" gap.  Good catch.  This one is probably too tight and would require some bolt machining: https://www.mcmaster.com/6100k191


Here are the two I found in brass:

Bolt: https://www.mcmaster.com/8859k24

Probe: https://www.mcmaster.com/8859k21

I prefer McMC for researching the specs.  On Amazon, it depends on the particular seller what is listed.  The brass are much cheaper than the SS.  Do you know if there is a inner welded seam on brass?  or is it smooth, ie drawn?

Understood and agreed on specs.  I try to use manufacturers websites, in this case k&s and then find the part number on amazon.

K&S is smooth, I use it for Cobra valve chambers and orings seal perfectly....

K & S PRECISION METALS 8131 1/4 x...

[FuzzyGrub]

Understood and agreed on specs.  I try to use manufacturers websites, in this case k&s and then find the part number on amazon.

K&S is smooth, I use it for Cobra valve chambers and orings seal perfectly....

K & S PRECISION METALS 8131 1/4 x...

Thx, yea had to go to K&S site for the tube thickness verification to part number. 

[FuzzyGrub]

You convinced me, went with brass.   

[mackeral5]

You convinced me, went with brass. 

Brass is so easy to work with...  I chuck it in my cordless drill and cut it with a sharp tubing cutter.  Spin the tube fast with the drill, while gently tightening the cutter.   Cuts very clean with virtually no deformation/compression

[FuzzyGrub]

You convinced me, went with brass. 

Brass is so easy to work with...  I chuck it in my cordless drill and cut it with a sharp tubing cutter.  Spin the tube fast with the drill, while gently tightening the cutter.   Cuts very clean with virtually no deformation/compression

Thx.  I've made safeties from brass rod before and that was easy enough.  Also purchased tubing to repair valves for poppet stem wear.  I haven't needed it yet. 

[subscriber]

You convinced me, went with brass. 

You did yourself a favor.  304 SS work hardens like crazy and can bring machining operations to a standstill.

[FuzzyGrub]

The barrel will be here today.  Plenum just shipped out from the Netherlands. 

And just received notice that the McMasterCarr order will arrive today!  I went with them because I had other items on the list (fittings, gauges, etc), that I didn't want to try to find on Amazon.  The tubing itself was half the price of Amazon, but that does not include shipping.  MC doesn't provide the shipping cost till after, which is rather annoying. 

FWIW: MC shipping was $8.25, which puts Amazon Prime at the slightly better bargain, if you were just ordering the brass tubes.  Getting it in one day was a nice surprise.

Anyway, looks like I will be test fitting the bolt this weekend.   

[FuzzyGrub]

Even though ordered from MC with no brand indicated, but did have tolerance specs, what was delivered was the K&S #8131 and #8128.  Both will slide over their bolt locations without an interference fit.  Both will need epoxy.  The OD's were spot on, given my caliper measuring capability. 

The latest version of miniature 0-4K gauge not thrilled with.  The numbering has gotten smaller, and the needle range is less than the prior one.  See below.   

[FuzzyGrub]

I cleaned the 25 cal barrel and pushed half a dozen pellets through.  The choke on this 25 GM barrel is VERY tight.  It takes some effort to push the pellets through.   It is much tighter than the two other GM barrels I have.  Does not sound promising.  I will have to install it on one of my Mrods to see what the accuracy is. 

FWIW: The new 177 Mrod barrel has a TP burr that sliced off a good sliver of the pellet tail. 

[mackeral5]

Even though ordered from MC with no brand indicated, but did have tolerance specs, what was delivered was the K&S #8131 and #8128.  Both will slide over their bolt locations without an interference fit.  Both will need epoxy.  The OD's were spot on, given my caliper measuring capability. 

The latest version of miniature 0-4K gauge not thrilled with.  The numbering has gotten smaller, and the needle range is less than the prior one.  See below.   

Looks like it is coming together.  On the tight barrel, while I've never done it, I've read where others have been very successful when starting with a tight barrel and polishing it out to size.  Though it will be extra work, I bet you will end up with great results.

Another note.... where applicable, that tubing solders very well when using flux and a micro torch.   

On the gauges....  that is a sore subject for me.  I have a pile of micro gauges that didn't match what I thought I ordered....

[screwwork]

Are you looking for shooting slugs or pellets the .25 GM barrel?
on .177 barrel, can you clean up the burr without to much trouble?

On a side note, I got to shoot the mini-rod yesterday, it likes the .25 JSB heavy MKII's. the wind was light to gusty and pushing the pellets around up to 3".  My barrel doesn't like the slugs so it is going to get the choke removed and see how it does then.
Also pulled out the Prod .177 shooting 21gr slugs - 850fps at 100 yards, (2 3/16" groups) I cannot wait to get on some rabbits or g-squirrels with it with low wind. I have a better long range scope for it an Aeon 6-24x  50 SF that is going to get mounted before my next outing as long as I can get it sighted in first at long range.

[FuzzyGrub]

I cut my first tubing for the bolt.  It is about 1/16" too long and will fix that.  I did not have any issue just using a standard tubing cutter and going slow.  I did insert the back end of a #2 drill up to within 1/8" of the cut, for tube support.   

Looking at the 22 bolt probe, it fits the 25 cal JSB pellet well.   It is about the same diameter as the flat of the pellet.   The 0.156" tubing has to push on the conical edges of the tail of the pellet.  For now, not going to sleeve the probe end.

The rear breech hole was too tight for the sleeved bolt.  I had to open it up a little with a 17/64" drill. 

That did expose a possible problem with going with the standard Mrod mag.  About 0.090-0.095" has to come off the back.  That will leave only 0.025-0.030" before breaking into the larger channel.  That would be a really thin wall.  I'll have to do more thinking about the mag solution.

[FuzzyGrub]

The barrel will be for pellet shooting only.  My experience with 177 and 22 cal with tight chokes, has not been positive.  This is by far the tightest choked barrel I have ever had.  It would take allot of polishing to get it where it needs to be.  I'll still test it in the Mrod and see.  I might return to crosman for exchange.

Yep, NP fixing the 177 barrel TP burr.  Typical crosman.   

[screwwork]

The good news is you can test GM barrel in another gun before machining it! 
As for using factory mag, opening up the breech could be the best choice in the long run IMO.

[FuzzyGrub]

I can't get a good picture of the pellet, but the whole circumference of the pellet head is being resized by pushing though the choke.  I'll leave that testing for tomorrow.    I have too many parts laying around already.