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 Posted: Sun Jul 03, 2011 1:42 pm |
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| rsterne |
| Moderator |
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| Joined: 15 Jan 2008 |
| Posts: 2998 |
| Location: Coalmont, BC |
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I just measured 10 pellets from each of 3 tins of JSB 15.9 gr. Exacts.... Here are the results for the head diameter:
Marked as 5.52 mm
Max: 0.217"
Min: 0.216"
Marked as 5.50 mm
Max: 0.2165"
Min: 0.2155"
Not marked as to diameter
Max: 0.2175"
Min: 0.215"
As you can see, all the 5.50mm pellets and 5.52mm pellets were within the range of diameters of the unmarked tin.... All that the marked diameter means is that they are within a narrower tolerance range (ie better quality control or possibly sorted by size).... I measured the skirt diameter on the unmarked pellets and it varied through an even larger range from 0.2255" to 0.2285"....
I then did some other pellets for comparison purposes:
RWS Superdome:
Head: 0.2155" to 0.218"
Skirt: 0.2245" to 0.2275"
H&N FTT 5.50mm:
Head: 0.2190" to 0.2210"
Skirt: 0.2260" to 0.2290"
Crosman Premier HP:
Head: 0.216" to 0.218"
Skirt: 0.2220" to 0.2245"
When taken over all the types of pellets measured, the head diameter varied from a low of 0.215" to a high of 0.221".... and the skirt diameter varied from 0.222" to 0.229".... Note that the skirt is significantly (an average 0.009") larger than the groove diameter of the barrel.... but it is so thin that it easily conforms to the bore when loaded.... When you consider the very wide tolerance range between pellet types.... I would be hard pressed to believe that a difference of 0.04mm (ie 0.0016") in one single pellet type would be noticed in how the pellet loads by the average shooter.... when the tolerance in diameter within most tins of pellets is more than that....
Here is a photo of some JSB 15.9 gr. Exact pellets pushed through a bore (right) and shot through the same bore (left) at 720 fps....
You can clearly see the obturation that occurs as the skirt expands and fills the rifling completely when fired.... compared to the minimal engraving by the rifling on the pellets pushed through....
Bob |
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Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal: Too many to count! |
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| Posted: Sun Jan 08, 2012 9:37 pm |
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| jason3064 |
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| Joined: 27 Nov 2011 |
| Posts: 40 |
| Location: Trinidad & Tobago |
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| You just saved me some money mod,thanks man |
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| Posted: Mon Jan 09, 2012 9:10 am |
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| mod90 |
| Veteran Member |
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| Joined: 04 Jun 2011 |
| Posts: 279 |
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Anytime Jason  Just pay it forward. |
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