Chambers?

D

Dennis D.

Member
I've been playing with chambers on my TM1000 and am having a reoccurring problem with all of them.
Chamber one is as it comes from the factory, a simple 90 degree countersink was used to create a tapered entrance and sealing surface. The finish was very rough and shaved bits of lead. After polishing, it no longer shaved lead but it did roll the back of the skirt of the pellet leaving a little trailing edge. Chamber #2 was a 2 degree leade just like a Calfee style rimfire chamber, the leade started just past the port in the barrel and was just big enough for the head of the pellet to enter the barrel without resistance. The skirt still folded back and created a little ridge at back of the skirt. Chamber 3 was the same with a 1degree leade. better but still rolls the back of the pellet more than I'd like. Chamber 4 starts as a 1degree leade into the barrel big enough so the skirt easily enters the barrel then a straight section about .125 long then another 1 degree leade into the rifling just past the barrel port. This leaves less of a trailing edge on the rear of the skirt however it does occasionally produce a very paper thin wire edge that detaches from the skirt in some places. This happens about once every 10 or twelfth pellet pushed through. This occurs more with the JSB pellets than with H&N's but it is sporadic. All the chambers except the factory one where polished to a bright finish. Barrels used are in .177 and .20 cal. and show the same results.
I realize that the skirt design currently used contributes to this and I notice that the JSB Monsters show less of an effect than the standard pellets.
Any one come up with what they think is the perfect chamber yet?

Dennis
 
Hi Dennis, I don't know anything. Hurry and firgure it out. When I see you next summer you can fix mine. I hope. Don
 
Dennis,

Only my opinion.

This is the problem. I think you need to know what pellet your barrel shoots best before you can cut the best chamber. There seem to be 3 distinct pellet families, H&N, Crosman and JSB. Even within the families, there are variations in shape and length. A basic 1.5 degree chamber approximately .285 deep can be cut. Dave Kiff has, what he calls throaters, that are 1.5 degree tapers starting at one dimension and ending at another. Mine is for .22 caliber and starts at .216 and ends at .223. Reduce your pellet selection to the very best. This could be more than one but that makes the next steps somewhat of a compromise unless the dimensions are VERY close. Measure head diameter, skirt diameter and length. This measuring can be a challenge, so use your best equipment. Now, cut a chamber that replicates the pellets shape. Depth can be just touching the lands or a bit tighter. Shoot those pellets and see where you are.

Obviously, if you find something better, let me know.
 
Well, now we have hit on a great subject to discuss Dennis and it appears you have gone to great lengths to improve your condition. I went all through tis over a year ago so can relate with your agony.
I believe Steve is right. It becomes a catch 22 situation as you kinda need a good shooting gun to discover what pellet makes this gun sorta happy. You can refine the method later. So that is why we all play and keep pellet manufactures in business. Sooner or later a trend will emerge from shooting and the stats will produce something that generally will work saving us poor souls a lot of time and money not to mention the frustration. Shaving lead is a pain and can in no way be doing accuracy any good as you just know some still remains as flakes in your bbl. Push a patch through and prove it. So let's speculate a bit, what happens to those flakes when the next pellet comes ripping down the bbl? Does the air in front of the pellet push it ahead of the pellet or is it overtaken and imbedded into the moving pellet? I do not have aclue but I can assure you one of those things IS happening .

It may be as easy as different lead hardness or skirt thickness giving us the condition of one pellet flaking less than another. Changing chamber angles and correct diameters at the rear of the chamber along with polish are the usial methods to achieve success. Both need to be done with equal care as not to round off the lands that support the head of the pellet and most definitly really on center. I personally like to see a pellet be gently swaged on a super smooth surface as it moves forward rather than an abrupt skirt reduction at the instant the air overcomes resistance. It just makes good sense to me that a gentle swage and not a .007 abrupt reduction would tend to less upset and keep a pellet more on center as it starts down the bbl.

Now if the pellet companys would give us prints of their pellets our job would be much easier but I have not succeeded in 2 years so had to have a batch shadowgraphed to obtain the exact pellet dimensions. Now you can have a reamer made.

I would like to see the major players weigh in on this like Jim Herrick and Dan Brown and other successful shooters that produce winning chambers and let them enlighten us................come on guys help us out here.

Frank
 
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Well I'm far from a major player Frank. Here is what I usually do. Guns that require that the pellet be seated by hand into the rifling like steyrs, usfts, and Chip's sumo, I will cut a 1.5* lead with a small radius at the outer edge. Guns that are probe fed like the Rapid and TM, I prefer to mount a thimble to the end of the barrel. The bore of the thimble is just a little bigger than the groove diameter of the barrel. Since the pellet is held precisely as it enters the barrel I use a 30* per side lead.
Dan
 
Thanks Dan for your input. You are also very humble. Dale Earnhart once stated he was only a farmer that raced on weekends.

Dennis back to the flake thing. New dies in the case of Cometta were very sharp and pristine especially in the two step skirt area. I have pellets from the same die six months later and found the pristine edges gone and very thin flakes of lead appearing in the inside of the thin first step in the skirt. In some cases the flake went completely around the inside of the skirt coming out in one piece. This all taking place after careful washing. I too have seen what looked like a flake or bubble but when poked with a sharp point found a hole or void in the pellet. These found almost always inside the cavity.

I used to find the flakes when I cleaned my barrel as you thinking I had a chamber problem and made every attempt to smooth all surfaces and sharp edges that I assumed caused the problem to no avail. It was only later that I found the problem to be not in the gun but in the pellets themselves................cleaning them was not removing all the flakes and found I needed to pay special attention when looking at them before sizing. This dramaticlly reduced my flake problem..................

frank
 
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I'm not having problems with the flakes left over from manufacturing or flakes being shaved from roughness in the chamber. Whats happens is that as the pellet is swagged down at the trailing edge of the skirt a very thin whisker of lead is formed. Occasionally, say every 6th or 10th pellet this whisker actually detaches from the skirt in places leaving a little tail. Just like the whisker that forms on a knife blade when you sharpen it. Now of course this is happening when I push the pellets through by hand and I am assuming that the same thing is happening when they are fired as well. I understand why it is happening but have yet to figure out how to prevent it. In reality I'm not even sure that it is a problem as they may be blasted off upon firing but I can't help but think that it may be the cause of some of the odd fliers that occur. Since it happens to some degree or another with all of the brands of pellets I've tested, both lubed and bare it's not related to any particular brand but to the general design of the pellet. When you swage metal it moves. I'd just like to find a chamber that doesn't induce a deformity to the trailing edge of the skirt.

dennis
 
I'm not having problems with the flakes left over from manufacturing or flakes being shaved from roughness in the chamber. Whats happens is that as the pellet is swagged down at the trailing edge of the skirt a very thin whisker of lead is formed. Occasionally, say every 6th or 10th pellet this whisker actually detaches from the skirt in places leaving a little tail. Just like the whisker that forms on a knife blade when you sharpen it. Now of course this is happening when I push the pellets through by hand and I am assuming that the same thing is happening when they are fired as well. I understand why it is happening but have yet to figure out how to prevent it. In reality I'm not even sure that it is a problem as they may be blasted off upon firing but I can't help but think that it may be the cause of some of the odd fliers that occur. Since it happens to some degree or another with all of the brands of pellets I've tested, both lubed and bare it's not related to any particular brand but to the general design of the pellet. When you swage metal it moves. I'd just like to find a chamber that doesn't induce a deformity to the trailing edge of the skirt.

dennis
 
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