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Post # 4: The Barrel Crown 

11/17/2013

1 Comment

 
It seems there are nearly as many opinions ABOUT what a good crown is as there are barrels.

Let's break it down and go for the obvious first.  

The end of the barrel can be flat faced without any harm to the accuracy of the gun.  How could the face have anything to do with the flight of the pellet, anyway?  But... any future bumping of that flat face may result in damage to the bore edge.  That just might affect the accuracy of the gun. I personally like BOTH a raised outer face perimeter with a faint bevel to the edge of the tip OD to take away the sharp edge.


The end of the bore (where the ID meets the face) should be crowned.  I like a 60 degree bevel at the interface of the face and the bore. However, if properly done (on a lathe), I see no reason why 50 or 75 or 90 would not work.  As long as it is symmetrical and smooth there should be no downside to one angle over another.  I expect that any good crown job will be very accurately made (again, on a lathe) with a crowning bit... a good burr check... and finally a good polishing with a lapping bit and compound.


I am convinced that none of the above really matters as long as the transition from rifled bore to crowned angle to face is smooth, symmetrical and without burr or dragger.  


Rule of thumb: If the pellet does not touch it as it exits the barrel, then it is not important.


Some of the best shooting guns I have shot have factory crowns that are not too pretty to look at.  Inversely, some of the barrels with absolutely gorgeous and accurately made crowns just will not group like the others.  So why is that? The problem is not the crown. It is something else.  


Does the gun NEED a different pellet?  Odd how our guns like certain pellets, yet another of the same model may need a different one entirely.  The answer is that there are numerous variations of the bore (diameter, straightness, any choking going on?)... variation of the lands and grooves of the rifling (the highly regarded Lothar Walther match barrels for our guns have more lands and grooves, but their crowns are actually quite plain AND ALL LOOK THE SAME)... variations of the leade of one barrel to the next and how well they seat (or distort?) the pellet on average, etc. 


Some people put an awful lot of importance to the crown.  I look at it as one of those things that if done accurately just eliminates the crown of a gun as a variable in our quest for the "nail driver" accuracy we all want.  Put another way: In my humble opinion, a bad crown can negatively affect accuracy (by physical interference and/or being non-symmetrical). But if it is not doing that... then it is a neutral that is having no negative OR positive affect.  One good crown job is no better or worse than any other good crown job.  A crown is either problematic or it is sufficient.  I say barrel crowns do not fit the "mojo" category.


Have fun shooting!


 



1 Comment

Post # 3 - Cleanliness is next to Godliness?

11/3/2013

0 Comments

 
Well, in the grand scheme of things, maybe that is taking it a bit TOO far, but the sentiment is a good one for our guns.

The bad news:  When you get a brand spanking new Crosman gun (Co2 or pump), it will most likely NOT be as clean and smooth and lubed up as it needs to be to start its long life of service to its new owner.  The catch is that what I am about to recommend (what I ALWAYS do) will most certainly void your warranty.  So if that bothers you in any way, stop reading NOW.  I understand that this is not for everybody.  I know two truths for myself: I want to clean and re-lube my new gun... and there is no scenario in this world where I personally would ever need to send anything back to Crosman to fix for me. Even if in my cleaning I find a defective part, the gun will not go back to Crosman. They may be sending me a replacement part... and they may request that I send the bad part back to them.  Fine. WIthin days or weeks, my gun will be so changed that there is no way the warranty means anything to me whatsoever.  So please take this into consideration before you do ANYTHING. 

The good news: Our guns are easily dis-assembled and just as easily reassembled. And if you are new to "our guns", what better way to learn how it works and become familiar with all the parts and how they are assembled than to go through it for a good initial cleaning, polishing and lubing?  I can guarantee you that this was the best way for me to learn them inside and out when I first began.

Knowing the parts intimately and truly understanding their functions and interactions is absolutely a MUST for the serious modder / builder to make certain they wind up with a truly improved air gun. It sure helps to thoroughly know your gun before you try to change something you don't even fully understand, especially if you are the type that might actually come up with new modifications, procedures, new designs for improvement... or to solve a problem.

Second only to this one-on-one communion between you and your new gun during this initial cleaning exercise, I recommend that you join the CAPOF forum and start reading, pondering, looking and asking questions. In a short time you will know the answers to questions that you read from the new batch of newbies that come after you.

Finally, do not forget internet searches and Youtube videos (both best taken with a grain of salt at times, but usually educational and informative).  I actually found out about the CAPOF (Crosman Air Pistol Owners Forum) by watching interesting videos made by BRUTUZ the creator and web master of the forum! 

Notice: Dear Reader, I am telling you what I do and why.  I do not know your mechanical aptitude, what tools you have, whether you know how to use tools, what your fine motor skills and eye/hand coordination are, whether you can look at an exploded drawing from the Crosman site and see how things work, or whether you have the ability to have a clue where parts you just removed go back together.  Bottom line: Disassemble, clean and reassemble your gun if YOU want to do it... if YOU feel comfortable doing it, and YOU take full responsibility for attempting it.  If this disclaimer causes you to pause and/or doubt yourself, then do not do it.  Do not call me asking for the safety ball and spring you lost because you were following my recommendation to disassemble and clean your gun.  

Back to cleanliness!  I am not going to detail dis-assembly and reassembly.  There are some good Youtube videos to help you if you need it.  Watch them first before you begin and as many times as you need to do the job.  

While you are doing this total (or near total) tear down, wipe every part down with a clean cloth. Terry towel scrap or rag is just fine.  Just don't leave anything behind. I use white just so I get to look at all that black and brown gunk that covers much of the internals. Feel every surface that you can with your fingers and make note of any raised edges or burrs.  There should be none, but most times there are.  Maybe not anything totally absurd, but just not clean and smooth.  Now I do not recommend that you do any metal material removal at all.  But if the hammer looks like it was picked up off a greasy tray that it had been laying on for awhile... and the discoloration will not wipe off, then perhaps a very light sanding... or solvent bath... or tumbling in your reload vibratory tumbler if you have one... is in order.  

I do have both a vibratory tumbler and a solvent bath.  My set method for cleaning is to toss the hammer, the sear, the springs and the brass bolt (o-ring removed) in it on top of some walnut shell media for a couple of hours. Afterward, I blow them off with the air hose and finally I give them a bath in acetone or naptha or lacquer thinner, etc. Of course remember that nothing rubber (o-rings, seals, gasket) or blued gets the tumbler or the solvent bath.  If you have neither of these then you can do just fine with your cloth and perhaps some 60 grit paper if needed.  Do not sand anything blued and/or external, of course.  I suppose only the hammer and the outside of the 22xx valve are the only two light sanding candidates.


Push some cleaning pellets down the barrel until one comes out really clean.  It is usually the third one for me.  Then take that clean one and run it through once more from the opposite end.

Do not forget the inside of the tube.  I hold it up to the light and peer into it to look for anything that is not a smooth shine.  I run a cloth through it until it is clean.  

If this is your first time, perhaps skip over taking the valve apart (the two halves of the body just unscrews... and they only have seven parts including the o-rings and the valve housing halves on the pumpers... and only six for the CO2 valves).  But if you are game, go for it.  To unscrew the valve halves, I wrap a piece of business card around one end for scratch protection, then clamp it securely with vise grips... and turn the other end with the chuck end of a drill bit that just fills the valve port opening.  I can do this over and over without scratching the outside of the valve.  You may have a different or better idea.  I know my ways works just fine for me.  

I certainly do find little "treasures" from time to time in the valves: a piece of grit, or excessive locktite on the threads of the 22x valves... an occasional tiny piece of metal shaving (swarf)... and certainly more of the discolored lubricant that you will have already seen on the outside of the valve, on the hammer and spring and inside the tube.

So now you have it all apart and everything is clean.  Now we need to re-lubricate before we re-assemble. I use my own Cart Gun Oil (same as Pellgunoil) and just put a drop on my fingers and then rub over all the surfaces as I re-assemble.  No heavy application on anything, just a light surface film is all it needs.  This includes the threads of the CO2 cap, the springs, the hammer, the hammer pin, the valve parts inside and out, the sear, the bolt/probe, all o-rings, etc. etc.  I do not lube the barrel at all.  It will get mistings later as it is being used. Use a tiny amount of a lithium or synthetic grease on the sear and trigger pins, on the sear spot where the trigger contacts one end and on the sear spot where it contacts both the spring from below and the hammer catch from above. 

Until next time... Have fun shooting!
0 Comments

Post #2... Modifaction #1 - Sear Spring Adjuster "Tuning" Mod

11/2/2013

5 Comments

 
Here we have the Crosman Sear Spring Adjuster.  It is comprised of three parts (the spring, the base and the adjuster).  This upgraded sear spring comes on the 2300S and the Crosman Custom Shop 2300KT and 2400 KT pistols and carbines.
Picture
This upgrade will also fit any of the trigger frames of the 22xx and 13xx familes as well as the Backpacker.

These guns with the stock sear spring will have a trigger pull in the 3.5 to 4.0 lb. range.

Add this upgrade with the adjuster all the way down and you will immediately have a trigger pull in the 2.5 to 3.0 lb. range.  Getting better, huh?  But that's all there is?  The adjuster is all the way down and you can't relax the spring any further !?  Nah!

So lets mod the mod, then... shall we? 

Cut about two loops off of the spring on one end only.  If you can't count loops, then just make it about 1/4" inch shorter.  Re-install the spring with the freshly cut end of the spring DOWN.  With the adjuster lowered all the way, cock the gun and dry fire it.  If it will fire, then take the spring off and cut another loop off.  What?  Yes, we do not want the gun to release the hammer with the adjuster all the way down.  Fast forward to you having the spring in with the adjuster down and the gun will not release the hammer.  GOOD!

NOW... adjust the adjuster up while testing every 1/4 turn until it WILL release the hammer (dry fire).  Dry fire over and over to make sure it will release the hammer every time.  Adjust up in 1/4 turns until it does release the hammer many times in a row.  

Congratulations!  You now have a trigger pull in the 1.5 to 2.0 lb. range.  Feels really good, huh?  You are now about 1/2 the trigger pull of the stock trigger spring... and you have doubled the affect of the adjustable sear spring from approx. 1 pound of pull reduction to approximately 2 pounds of pull.  

If that is too light for you, there is still more upward adjustment to go higher with spring tension and trigger pull.  So, there is no harm done and we have not lost anything at all (except I am positive you just voided your sear spring adjuster warranty).  Pity that. ;)

Oh, almost forgot: If you have a CCS (Crosman Custom Shop) trigger frame that has the adjustable trigger stop, now is the time to set it as close to the the trigger as possible without preventing repetitive firing.  It takes the "slop" out of the trigger travel past the point of firing.  

Less unnecessary movement = better grouping / accuracy.  A repeatably predictable trigger pull that you can "get used to" and count on = better grouping / accuracy.

Next time we'll talk a bit about the finer points of cleaning and polishing and de-burring (Oh MY!).

Until next time... Have fun shooting!

5 Comments

Blog Post #1 - About "our" airguns (for the Crosman newbies)

10/31/2013

5 Comments

 
There are so many brands of air guns... pistols, rifles and carbines.  So why Crosman?  What makes Crosman so special? Crosman has done a wonderful thing in making the CO2 22xx family and the 13xx pump family.  

These include the C02 1740, 2240, 1750, 2250B, 2250XE, 2760, 2260, 2300T, 2300S, 2300KT, and 2400.  On the pneumatic pumpers we have the 1377, PC77, 1322, and Backpacker.  

First, these guns share many components across the two power plant platforms.  A moderator on one of the better forums put it that Crosmans are the "Lego's of air guns".  I will add that only the Barbie doll has more opportunity for dress up combinations... but just barely.


The guns are well made and are surprisingly accurate right out of the box.  The cost to buy new is ridiculously low in my opinion.  But that is a good thing, because the designs lend themselves to nearly infinite combinations of modifications for looks / style, performance, accuracy, and accessorizing.  

Some folks may wonder why anyone in their right mind would buy a 2240 for less than $60, and then change and add things to their liking until they end up with 2, 3, 4 or 5 times the initial cost of that new gun.  The best way to get the point across is to hand someone a stock 2240 or 1377, etc. to look at, feel and shoot.  Not bad at all.  But then hand them a custom build to look at, feel and shoot.  Most would instantly "get it".

The next blog page will be a how-to that will be an easy, free do-it-yourself mod with no chance of failure and guaranteed improvement. 

Until then... Have Fun Shooting!


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    Author: 
    David Grimes

    A serious airgun enthusiast with a particular fondness of Crosman pistols, I learn something almost every day.  


    I am not an overall expert or guru, but I will share some things from time to time that maybe some of you will find interesting.  


    There are often many ways to accomplish an objective. I do not pretend to either know them all or imply that I am always right. 


    Therefore, I reserve the right to be wrong from time to time.  ;) 

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