Breech Plug Comparison
#1
Nontypical Buck
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Breech Plug Comparison
Today we went to the hills to compare two breech plug. Bullet velocity from each plug was measured. One plug is sized for a vent liner with a 3/8" head, and has a 5/32" flame channel. The other is sized to receive a vent liner with a 5/16" head, and has a 1/8" flame channel. Both vent liner have a 0.028" flash hole.
The clock ended up about 14 yard out. Rifle used was the V2; load was 270g Deep Curl, 110g BH209, green Harvester sabot, and STS primer. Powder was dispensed into tubes by Redding 3-BR measure.
The clock ended up about 14 yard out. Rifle used was the V2; load was 270g Deep Curl, 110g BH209, green Harvester sabot, and STS primer. Powder was dispensed into tubes by Redding 3-BR measure.
#2
Giant Nontypical
Join Date: Nov 2005
Posts: 6,585
That is very interesting. While some would look at the total velocity what impresses me is the difference between high and low.
5/32 shows only 11 feet difference while the 1/8 shows 27 feet per second difference
,the 19 feet per second faster by the 1/8 is almost immaterial by comparison to the consistency of the 5/32.
I have a question: with the velocity starting high and tapering down, were both groups started on a clean barrel?
5/32 shows only 11 feet difference while the 1/8 shows 27 feet per second difference
,the 19 feet per second faster by the 1/8 is almost immaterial by comparison to the consistency of the 5/32.
I have a question: with the velocity starting high and tapering down, were both groups started on a clean barrel?
#4
Nontypical Buck
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lemoyne
The first shot using the plug with the 1/8" flame channel was on a cold clean barrel. Then the third, fifth, seventh and ninth shot. The shots by the plug with the 5/32" flame channel were the sixteenth, seventeenth, eighteenth, nineteenth, and twentieth shots through the barrel.
The first shot using the plug with the 1/8" flame channel was on a cold clean barrel. Then the third, fifth, seventh and ninth shot. The shots by the plug with the 5/32" flame channel were the sixteenth, seventeenth, eighteenth, nineteenth, and twentieth shots through the barrel.
#6
Typical Buck
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#7
Nontypical Buck
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Range was about 100 yard.
To me the only shot that seemed to jump far out of the set was the first though the plug with the 1/8" flame channel. That was the first shot from a cold clean barrel. To me, all other shots were just fine, and seemed quite consistent. These loads were all measured by volume, using a Redding 3-BR measure, and dropped into tubes which were carried to the hills, and poured into the rifle barrel.
Bottom target was shot last using the breech plug with a 5/32" flash channel. These were the sixteenth through twentieth shots through the rifle. Chances are good, i was kinda bored by then, and did not do my part. The middle target was shot with the breech plug with the 1/8" flame channel. The ventliner was switched between shots, but the same plug was used. Half the shots were when there was a 0.028" flash hole; the other half with a 0.034" flash hole.
The top target was shot using the breech plug with a 5/32" flame channel, without the vent liner in place. Essentially, the flash hole was 5/32"; velocities were inconsistent, and primers had to be pulled out using a pliers. These primer exhibited sign of excess pressure.
Further testing will be done.
#8
Nontypical Buck
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The 5/32" flame channel had a 27 fps total spread.
If one tosses the 1929 fps shot on a cold clean barrel, the 1/8" flame channel had a 16 fps total spread.
The 1/8" flame channel had the least spread when comparing fouled barrel, and it also had the highest velocity.
More testing is required.