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PostPosted: Sat Dec 12, 2015 7:16 pm 
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Joined: Thu Oct 08, 2015 6:35 pm
Posts: 87
I started work on legalizing my .177 conversion today.

This all started out with simply swapping parts between my 2240 and 1377. I kept the stock hammer spring, transfer port, etc. The only parts I used from the 1377 were the breech, bolt and barrel.

It shot very nicely with no further tweaking. It was a little quieter, grouped very well, pointed nicely, and felt better balanced with the longer barrel.

However, it was shooting well in excess of the PAL limit. With 8.2 gr RWS Meisterkugelns, and a fresh powerless, it peaked in excess of 550 fps.

My original chrony numbers were suspect, as I was having trouble sorting out the lighting for my new Caldwell chronograph.After about 30 test shots, I got the lighting sorted out, and it gave me a nice, consistent 5-shot string that looked like this: Average 526 fps, Standard Deviation 2.1, Min 524 fps, Max 529 fps, spread 5, TMV 526 fps

For obvious reasons (I don't have a PAL), I disassembled it after the initial test session.


Last edited by BassmanSteve on Sat Dec 12, 2015 7:42 pm, edited 1 time in total.

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PostPosted: Sat Dec 12, 2015 7:39 pm 
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After receiving an order from Mellon Air this week, I put the pistol back together, and set about getting it adjusted for sub-PAL velocities.

The thing that caught my eye back in November, was the 5 fps spread over five shots. No wonder it was grouping nice and tight...

Ideally, I would like to retain that consistency, while getting 7.9gr pellets down to around 400-450 fps. If it was as quiet as my 1377 at four pumps, and gave me around 50-70 useable shots per powerless, that would be a bonus.

The parts I installed were a tuned 1377-length barrel from Mr Mellon (re-crowned and polished muzzle, recut bevel at the breech), a stainless extended probe, and an aluminum power adjuster.

I didn't hear a major difference in the report when dry firing, until I had the power adjuster backed off 4 turns. So I used that as the baseline for my first 10-shot string: Avg 406.9 fps, SD 31.2, Min 342, Max 436, Spread 94, TMV 407 fps.

Even at 18 feet, there was a pretty big vertical spread in the POI, presumably because of that 94 fps variation in velocity. The hammer strike and the pellet hitting the trap were much louder than the "pop" of the C02 being discharged.

I noticed that the Meisterkugelns didn't like the Mellon probe and barrel. It felt tight and "clicky" as I closed the bolt. Since Crosman Premier HP's from the tin (7.9 gr) felt nicer, I shot another 10-shot string at 4 turns out: Avg 411.2, SD 24.8, Min 363, Max 441, Spread 78.

Not a significant improvement, consistency-wise...

Staying with the CPHP's, I turned the power adjuster back in, to 3 turns out. Consistency was better: Avg 455.3, SD 16.1, Min 420, Max 476, Spread 56.

Out of curiosity, I backed the adjuster out another half-turn, to see if it would get worse. Instead, it got a little better: Avg 449.1, SD 12.2, Min 425, Max 468, Spread 43.

Thinking that the new barrel might just be settling in, I checked my screws for tightness, then tried another string, without making any changes: Avg 432.0 FPS, SD 12.5, Min 416, Max 456, Spread 40.

At that point, I ran out of time, and had to end the session.

FYI, all shot strings listed in this post, were off the same C02 powerless. The date of the original test session with the 1377 barrel, was November 23rd...


Last edited by BassmanSteve on Sat Dec 12, 2015 8:07 pm, edited 2 times in total.

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PostPosted: Sat Dec 12, 2015 8:00 pm 
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One thing is clear to me, and backed up by past experience with modifying motorcycles and audio gear: I made the classic noob mistake of changing too many variables at once.

Anyway, I've read myself silly, looking at posts on down-tuning, but I don't have enough experience to make sense of what I'm reading.

Next time out, I may try swapping in the 1377 transfer port, or put the stock 1377 bolt and/or barrel back in.

But first, I'd like to understand more about the principles behind this stuff, instead of shooting blind (so to speak). Would any of the forum experts like to weigh in?

Here are just some of my questions:
- Is the 2240 TP too big for the .177 barrel?
- Have I backed out too far for the standard Crosman hammer spring (about 3/16" less preload at 4 turns out)?
- Is the hammer too heavy for .177 at these velocities?
- Could other factors like the stock, unpolished tube and hammer be contributing to the velocity spread?
- Is the velocity more consistent at full power simply because the power plant is self-regulating when it's dumping that much C02?


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PostPosted: Sat Dec 12, 2015 10:09 pm 
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Location: Coalmont BC
I would start by clipping the hammer spring to drastically decrease the amount of CO2 you are using.... If you can lighten the hammer, that works great in a .177, you can eliminate half the hammer weight without problem.... Stock porting works fine in .177, and the 2240 and 1377 ports are the same size.... That is not to say you might decrease your CO2 use with a smaller port, however I have not done that.... Also, you can try stuffing the valve to decrease the volume of CO2 inside, as it is larger than needed for .177, but again I have never bothered.... A couple of pieces of brass hobby tubing the right length works well, apparently....

Done right, you can get over 100 shots per cartridge at just under 500 fps in .177 cal, depending on barrel length (the longer it is, the more you can detune the gun for that velocity, so you get more shots).... I got 130 shots at 490 fps (7.8 gr) with an 18" barrel.... and not only that but the velocity was stable from 40* to 75* F.... and from the beginning of the cartridge to the end.... That is a side benefit of sipping tiny amounts of CO2....

Bob

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Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal;
Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!


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PostPosted: Sat Dec 12, 2015 11:20 pm 
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Location: mb
For winding down CO2 platforms(22XX,QB) to use .177 barrels, I personally like stuffing the valve and lightening the hammer. Polishing the hammer and ensuring there
isn't any torque on the hammer spring, helps reduce shot-to-shot deviation as well. Some RVA's(power adjusters) impart twist into the hammer spring, as well may not
allow the spring to seat flat. I've successfully used guides and/or fitted and lubricated spring seats to address the issue. I try to use the lightest hammer spring I can, that'll still
give the desired muzzle velocity, as using an overly stout hammer spring, adversely affects trigger pull on a 22XX based gun.
As Bob(rsterne) has mentioned, the stock 22XX hammer is too heavy by at least half(even for 22), and the valve is over volume by a similar amount.
My early experiments with Transfer Ports has led me to always matching them, to the diameter of the exhaust port of the valve. I found that restrictive TP's,
weren't conducive to the best efficiency(shots per cart). YMMV.
Quote:
. . . mistake of changing too many variables at once. . . .

You're in good company. Been there too. . . .

There's a few schools of thought on many of these mods. The fun is trying them all, and finding out what works best/easiest for you.

Good Luck!

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PostPosted: Sun Dec 13, 2015 6:42 am 
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rsterne wrote:
...Stock porting works fine in .177, and the 2240 and 1377 ports are the same size....

Pardon my noobness, but am I using the wrong terminology?

I'm talking about the little aluminum part that sits between the tube and the barrel, not the port in the side of the valve.

The inside diameter of the one in my 1377 is a lot smaller than the one in the 2240. I'll have to take a picture to illustrate.

Regardless, this is all excellent information. Thank you, gentlemen.


Last edited by BassmanSteve on Sun Dec 13, 2015 7:02 am, edited 1 time in total.

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PostPosted: Sun Dec 13, 2015 6:59 am 
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PS: I've noticed that a lot of people tune for 490 to 495 FPS with standard pellets.

I would worry that a firearms inspector would test with a lighter pellet, or use a chronograph that was accurate at a shorter distance from the muzzle, and then rule it restricted.

Also, I love the mouse-fart quietness of my 1377 at 3 or 4 pumps, as my only shooting option is indoors. It chronies below 400 FPS, yet it's still pretty accurate at such close range.

Is there an accuracy-related reason for flirting with the PAL limit?


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PostPosted: Sun Dec 13, 2015 11:10 am 
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Posts: 1754
Location: mb
Quote:
. . .I'm talking about the little aluminum part that sits between the tube and the barrel, . . .1377 is a lot smaller than the one in the 2240.. . .

Transfer port is correct. And I agree with your findings; there is a distinct size difference between the one typically found in a 1377 vs a 2240. The one from a 1322
and 2289 can be the same or different as well. I think there are a couple different part numbers, as well as manufacturing tolerance over the years has fluctuated as well.
I do believe they are still steel though, as I've never seen one personally that are aluminium. You'll know for sure if you have to enlarge it. . .
Quote:
. . . tune for 490 to 495 FPS with standard pellets.. . . firearms inspector . . . test with a lighter pellet, . . .Is there an accuracy-related reason . . .

Very contentious, controversial and much debated topic. You need to do what's right for you. What position are you prepared to defend? And could it be to your own peril?
I think it was Gippetto that used the automobile analogy - You can't be convicted of going 200kmph, just because you're driving a vehicle that is capable of achieving
the speed. . . . But still, we're mostly adults, that need to decide what is the right path for ourselves. I contend, that if your airarms are in the hands of the CFO, the speed
of said gun is likely the least of your current issues/problems. . .

As to accuracy, only you can test your particular gun to determine what works best for it, your shooting distance, and the pellets of your choosing. We do however
live in a "more is better" society, hence the frequent scramble for the edge of the limit. . . to which I'm as guilty as the worst offender.

The big name brand manufacturers do everything possible to ensure compliance, but there's plenty of lesser known brands that are selling <500 guns in Canada,
that are well over the speed limit. . . Very few recreational airgunners use/own chronys. Unwitting Felons? Maybe, but I submit that as long as the illegal guns, are used
in an otherwise legal manner, there isn't likely to be any issue. . . YMMV.

Over the years, while shooting in different suitable locations, I've been approached by RCMP, OPP, City Police, and Game Wardens/ Conservation Officers. The topic
of 500fps has been mentioned a few of those times, but not once was a chrony whipped out to confirm compliance. Do the right things in the right places, and you should
expect reasonable outcomes. . . Again; YMMV. Good Luck!

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PostPosted: Sun Dec 13, 2015 11:42 am 
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Location: Coalmont BC
My apologies, the Canadian 1377s are sometimes equipped with a smaller transfer port, sometimes a bleed hole in the valve, or possibly both....

Bob

_________________
Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal;
Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!


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PostPosted: Mon Dec 14, 2015 7:43 am 
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My machine tool collection consists of a large drill press (1948 Canadian Buffalo), a bench grinder, and a Dremel.

After spending a couple of hours reading up on how to lighten a hammer, pricing lathes and milling machines, etc., reality finally set in. I don't expect to lighten more than 1 or 2 hammers in my entire lifetime. Meanwhile, my hobby time is severely limited, and my budget is sub-$500 per year.

Is it true that freehand lightening with a Dremel could take up to 18 hours to reduce the hammer weight by a useful amount?

If that's true, then what I really need to do, is find a properly-equipped machinist who can bang off a lightened hammer in an hour or two, and either sells them, or will cut mine.

Where do you find someone who works on small parts and one-offs, and what could I expect to pay?


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PostPosted: Mon Dec 14, 2015 10:48 am 
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Location: mb
Quote:
My machine tool collection consists of . . .a bench grinder. . .

In my humble opinion, you already own the right tool for the job.. . . It's all I've ever used for striker surgery. . .
The hammer is apparently hardened steel, and some guys have suggested that it's taken hours to remove any appreciable mass. . . :?
Start to finish in well under an hour, although I'll admit that my first one took longer, due to nervousness and the concern of "wrecking" it. . . .
Best part about Crosman current models; spare parts are plentiful and reasonably inexpensive.

Alternatively, post a WTB(Wanted to Buy) ad in the appropriate forum, and see who answers. There's also the Freelance forum which might prove helpful as well. . .

Order up a spare, as soon as you have it on site, start butchering. . . Worst case scenario; you clean up the swarf pile, install the replacement hammer
unmolested, and shoot targets until you get alternate ideas. . . . :lol:

Good Luck!

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PostPosted: Mon Dec 14, 2015 12:08 pm 
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Location: Vancouver
18 hours to grind down a Crosman striker? Huh, wouldn't have thought that possible, but I guess I've met the odd person like that. For mine it took about half an hour and two Dremel 3/4" grindstones. Which aren't cheap, but gave me better control than my bench grinder. I wore a good mask, silicone rubber with fine particle filters, as it's really not healthy breathing all that carborundum dust from the fast-shrinking grindstones. The Crosman strikers are case hardened. That makes use of a mill rather a difficult proposition, as high speed steel cutters will just chip and fall apart hitting the outer surface. A carbide cutter taken in very slowly might work but I wouldn't want to try in case it just shattered. Grinding seemed the obvious route. Once through the case hardened later it's just mild steel, easy enough to carve.

Using a lathe would be problematic as it would probably impact sear function with the 2240. I left the upper and lower edges of my striker alone, only removed steel from the sides, rather deeply, cutting almost to the spring hole. Asymmetric carving like that is a job for a Dremel. Just take small passes at first, little bites, until you get into the rhythm of it. Mark out your planned area of stock removal with a Sharpie and think about just getting up to those lines, no further. Think about the direction a grinding wheel wants to climb in the cut, so you know what to expect when the Dremel tries to run away from you and grind something you didn't want ground. Starting in the middle of the marked area is best, working your hollow outward in both directions smoothly so you're enlarging the hollow, not creating ripples which can make for difficulty as the grinder hits them.


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PostPosted: Mon Dec 14, 2015 6:51 pm 
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Location: Canada
Do any of you guys have pictures of the 2240 hammer after you have ground half off.
I think it's time for me to save some gas and reduce the hammer weight. :idea:
Tazz

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PostPosted: Mon Dec 14, 2015 9:08 pm 
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I used a lathe to lighten mine by 50%.... I used a carbide bit and once through the case hardened skin it turns reasonably easy from the inside out....

Image

There is no problem with the sear using a 2240 trigger group.... However, you cannot cut away the bottom of the hammer (in fact you have to fill it in) if you use a PRod trigger group....

Bob

_________________
Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal;
Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!


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PostPosted: Wed Dec 16, 2015 9:44 am 
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Location: Canada
Thanks Bob.

That hammer looks like it went on a large diet. :)

I guess my grinder will be up for it.

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