Accuracy potential of a crosman barrel.

[Colt25]

I received a Crosman 1377 of xmas 12-13 (back when they had brown grips) and shot it for awhile, and did some valve mods and painted the grips black and since I had another 1377 I already knew the platform and was comfortable modifying it. Well now I wanted to mount a scope, but the Crosman intermounts were too flimsy and I thought I'd just make one. Well an hour or so on the milling machine and I had a mice mount out of 6061 (T6) aluminum.





So I played around with a rifle scope since I didn't have a pistol scope and even though there is not enough eye relief I can shoot it on the bench with my eye close to the scope, no big deal for now.
I shot a group tonight to see what the gun could do with a stock breech.



Nice looking group, but notice the three shots to the left? I know I didn't pull the shots, they were definitive flyers. But they are not just flyers, three in ten shots is unacceptable.
I took the gun apart and looked at the barrel. Bingo! It's a defect......



See that straight ridge going through the barrel where the red arrow is pointing? That's a major problem. I might try and lap the bore to see of I can smooth it out but I might have to take too much.....

[breakfastchef]

I saw a similar defect on a Crosman .22 barrel. It was very inaccurate. Maybe it was caused when the 'thing/mandrel' was pulled out of the bore during the rifling process. If you can improve the accuracy, let us know what you did.

[airriflenut]

I was getting about 3-4 fliers in a 10-shot string in the 24" (.177) barrel of my Beast, this was with its preferred diet of RWS Superdome.  It wasn't bad shooting form so I tried a "bore smoothing kit".  Being a woodturner I have various polishing compounds on hand and this idea hit me one day.

I used a cheese grater to shave compound off the bars; black Emory, Brown tripoli, white diamond, reg rouge and blue rouge.  Those are in the order they are used.  The shavings were put into empty pellet tins then put onto the warming plate of a coffee maker to melt.  Once melted I add a small amount of mineral oil to get a soft paste consistency.

To smooth the bore, a cotton t-shirt patch is wrapped tight around a Dewey jag to the point that it's a moderately tight fit.  I then get some paste on my fingers and coat the patch well.  Using the Dewey rod I carefully (so as nit to bend the rod) run the patch back and forth.  Black Emory-15 strokes, Brown tripoli and white diamond-25 strokes each, red rouge-30 strokes and finish with 45-50-strokes of blue rouge.  Then a good cleaning with solventvand sundry patches thru until they come out white.

From my perspective the bore has a bit more shine after this process, what rough edges I could see before seem to have been smoothed out.  The results are 3/4" groups at 50 yardd!!

Good luck on your barrel work.

[K.O.]

I honestly can not see it well enough to tell if it is a ridge or a gouge...

how is your leade on mine the beginning of the rifling was sharp edged and it had a small burr at the port.

At what range was the group  I had a tight barrel that would cause finning and it looked about like that at 20 yards.

[Colt25]

I honestly can not see it well enough to tell if it is a ridge or a gouge...

how is your leade on mine the beginning of the rifling was sharp edged and it had a small burr at the port.

At what range was the group  I had a tight barrel that would cause finning and it looked about like that at 20 yards.

It's a ridge, and the group was at 10m.
The ridge is a bad thing because there is a chance the ridge will cat as rifling keeping the pellet from spinning. I pushed some pellets through, and some spun with the rifling, and some went straight through without spinning. Or at least that's what the rifling indentations on the pellets told me.....

I was getting about 3-4 fliers in a 10-shot string in the 24" (.177) barrel of my Beast, this was with its preferred diet of RWS Superdome.  It wasn't bad shooting form so I tried a "bore smoothing kit".  Being a woodturner I have various polishing compounds on hand and this idea hit me one day.

I used a cheese grater to shave compound off the bars; black Emory, Brown tripoli, white diamond, reg rouge and blue rouge.  Those are in the order they are used.  The shavings were put into empty pellet tins then put onto the warming plate of a coffee maker to melt.  Once melted I add a small amount of mineral oil to get a soft paste consistency.

To smooth the bore, a cotton t-shirt patch is wrapped tight around a Dewey jag to the point that it's a moderately tight fit.  I then get some paste on my fingers and coat the patch well.  Using the Dewey rod I carefully (so as nit to bend the rod) run the patch back and forth.  Black Emory-15 strokes, Brown tripoli and white diamond-25 strokes each, red rouge-30 strokes and finish with 45-50-strokes of blue rouge.  Then a good cleaning with solventvand sundry patches thru until they come out white.

From my perspective the bore has a bit more shine after this process, what rough edges I could see before seem to have been smoothed out.  The results are 3/4" groups at 50 yardd!!

Good luck on your barrel work.

Great results! I'm going to put some car scratch remover between the skirt and head of some pellets and fire them through to fore lap the bore.
I don't think I can remove the while ridge but I hope to smooth it out a little. If that doesn't work, I'll try a coarser grit then work my way down like you did.

[airriflenut]

The leade on my 24" barrel has no sharp rifling edges, the "smoothing" process I did appears to have smooth the leade as well.  The pellets seat with just a slight resistance into the rifling.

There is an Oak (quite a few actually) at 25 yards from my shop window, I've nailed some roofing nails into that tree.  The head of the nail is about 3/8", I usually plink 50 or more pellets at the nails every few days (from the window), most all shots are "on the nail" (pun intended).  Wind obviously has a hand with some misses.

I've shot 3/4" at a measured 50 yards on paper, if we ever get a calm day I'll shoot some groups at various ranges and post some pics.  There is another Oak 51 yards off, I shoot at a knot about 1.5" diameter mainly for gauging drift at different winds.

She shoots damn good for a Crosman barrel after I smoothed the bore.

[airriflenut]

Let us know how that polish between the head and skirt work, it sounds like a good method.  If you have any felt cleaning pellets those may work better loaded up with abrasive pastes.

I don't know it they are still available, but years ago there were center fire rifle bullets with various grits to fire lap a barrel so the same principle just might be good in airgun barrels.

[Colt25]

Let us know how that polish between the head and skirt work, it sounds like a good method.  If you have any felt cleaning pellets those may work better loaded up with abrasive pastes.

I don't know it they are still available, but years ago there were center fire rifle bullets with various grits to fire lap a barrel so the same principle just might be good in airgun barrels.

Yea, it works really good because the inertia when the pellet shoots forward drives the compound outwards.
I thought about felt pellets, but I didn't have any and they are too expensive for this.

[K.O.]

Q-tips with the paper stem..

[KevinP]

Well an hour or so on the milling machine and I had a mice mount out of 6061 (T6) aluminum.

N.I.C.E  job  ...   

[BigErn]

Love the solid mount you made  . How did you get those scope rings off that scope to move to the front. I have the same scope for one of my pistols and I could not figure out how to take the rings off    I wanted to mount it like yours to help with the eye relief problem.

[ped]

there is an Oak (quite a few actually) at 25 yards from my shop window, I've nailed some roofing nails into that tree.  The head of the nail is about 3/8", I usually plink 50 or more pellets at the nails every few days (from the window), most all shots are "on the nail" (pun intended).  Wind obviously has a hand with some misses.
[/quote]
some loggers going to love you for the nails,it's my pet hate(as a logger)
spent more time sharpening saws after hitting nails than cutting last week and believe me it's no fun sharpening by hand an 880 with a 3' bar and a 640 with a 25" bar 3 or 4 times in a day
as to the barrel i'd try either lead lapping or fire lapping but would probally swap it for another one
ped

[Colt25]

Well an hour or so on the milling machine and I had a mice mount out of 6061 (T6) aluminum.

N.I.C.E  job  ...   

Thanks! I had to make a custom single point milling cutter out of an allen wrench too. Didn't have a dovetail cutter small enough for the 1/2" maximum collet size on my mill.

Love the solid mount you made  . How did you get those scope rings off that scope to move to the front. I have the same scope for one of my pistols and I could not figure out how to take the rings off    I wanted to mount it like yours to help with the eye relief problem.

I had to remove the turret assembly. Two screws and it popped off, then you can slide the rings to one side.
The scope is not nitrogen filled, so you don't have to worry about that just be careful you don't get any dist or dirt in there.
Also, it can be a hair tricky to get back on, but it's very simple as long as you make sure the screws screw in straight. But anyone can put it back together, don't worry. 

[Colt25]

I fire lapped the bore then ran some homemade lapping compound through the bore then thoroughly cleaned it. I also took the time to re-crown the muzzle by putting it in my wood lathe and using a 3/8" round HSS burr to get the main crown then polished it with a super hard Arkansas stone to remove the burrs and smooth it out. Passed the Q-tip test flawlessly.
(sorry for the blurry photo)


I then shot a 10 shot group at 10m to see if it payed off.


That's a 3/8-16 tap for size.

Still a flyer, but the group improved a LOT!
I'm starting to wonder if the elongated group and flyer were caused by scope parallax...

More to come.

[eric]

I'm starting to wonder if the elongated group and flyer were caused by scope parallax... or crappy pellets