GTA
All Springer/NP/PCP Air Gun Discussion General => Machine Shop Talk & AG Parts Machining => Engineering- Research & Development => Topic started by: QVTom on November 26, 2012, 06:35:13 PM
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First post for the new gate. I hope it is appropriate :)
I have some PCP designs in the works. These are clean sheet designs, not mods or copies of existing guns.
I'm looking for thoughts on external pistol type hammers vs the slide hammers used in most PCPs? I'm especially interested in reliability and repeatability for the most consistent shot string possible.
External:
pros: 1) Can easily be de-cocked with out cycling action and double loading projectiles. 2) Gives a visible hammer cocked indicator. 3) looks realistic on replica style arms.
cons: 1) open to ingress of debris. 2) May get whacked and damaged in the field.
Internal slide:
pros: 1) possible easier to modify and tune. compression springs, spacers, guides etc. 2) protected from the environment.
Cons: ??
Tom
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The friction of a swing hammer will be the most consistent.
Easy enough to modify weight by adding or removing material from the thumb pad
Easy enough to modify stroke by adding or removing material from the striker face
Easy enough to modify valve actuation distance by adding or removing a spacer (o-ring) around the exposed stem.
Easy enough to modify spring preload if the action is designed correctly.
Hard to get the same level of trigger weight adjustability as a refined trigger group might.
Exposed hammers look and feel right! Real rifles have 'em!
http://www.youtube.com/watch?v=Ea5uxOpa_qs# (http://www.youtube.com/watch?v=Ea5uxOpa_qs#)
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I love hammers! I have a few semi-auto PBs but still carry my single shot H&R Deluxe 95% of the time. The transfer bar safety on their receivers is ingenious and I would love to mod one of their SB1 receivers into an airgun. I've got a .50 barrel with a twist rate that would be ideal.
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First post for the new gate. I hope it is appropriate :)
I have some PCP designs in the works. These are clean sheet designs, not mods or copies of existing guns.
I'm looking for thoughts on external pistol type hammers vs the slide hammers used in most PCPs? I'm especially interested in reliability and repeatability for the most consistent shot string possible.
External:
pros: 1) Can easily be de-cocked with out cycling action and double loading projectiles. 2) Gives a visible hammer cocked indicator. 3) looks realistic on replica style arms.
cons: 1) open to ingress of debris. 2) May get whacked and damaged in the field.
Internal slide:
pros: 1) possible easier to modify and tune. compression springs, spacers, guides etc. 2) protected from the environment.
Cons: ??
Tom
how about this type?.. it has a swing breech with an external hammer
(http://i1353.photobucket.com/albums/q674/plinker81366/IMG_1046.jpg)
(http://)
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I have seen a number of different types of springs used with external hammers, and I have to say that I like the look of an external hammer. Do any of them have the ease of spring force adjustment that the conventional sliding hammer and spring do?
Thanks,
Lloyd-ss
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I have seen a number of different types of springs used with external hammers, and I have to say that I like the look of an external hammer. Do any of them have the ease of spring force adjustment that the conventional sliding hammer and spring do?
Thanks,
Lloyd-ss
actually yes, the coil spring is located in the pistol grip hosing,at the bottom end there is a screw holding the spring back..tighten it and you get more hammer preload and vice versa..all you need is a screwdriver,
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Plinker, can you define "swing breech". That is an interesting looking gun. I really like the idea of the external hammer, the pistol grip gives plenty of room for a hammer spring. Thanks for posting.
Tom
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tom this is the swing when its opened,the pic is a little blurry, but you can see that there is a swing that opens the breech.
(http://i1353.photobucket.com/albums/q674/plinker81366/Facebook/Mobile%20Uploads/208441_479812278758544_2096528818_n.jpg)
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once the swing is open,then the pellet is inserted directly into the chamber by just simply pushing it with your thumb.
(http://i1353.photobucket.com/albums/q674/plinker81366/Facebook/Mobile%20Uploads/644428_479811718758600_434577451_n.jpg)
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tom here is alsothe bottom part where the hammer preload adjuster is located
(http://i1353.photobucket.com/albums/q674/plinker81366/Facebook/Mobile%20Uploads/382337_479812552091850_1968091994_n.jpg)
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Its also an advantage than you can use a shorter more powerfull spring.. or springwashers and just change the placement of the spring.
Im using springwashers on my Röhm Twinmaster HPA pistol.
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Wow, great info all around. I love seeing different ways to accomplish similar results.
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I wonder how hard it would be to cock a swing hammer that was powerful enough to fire a big bore with a big valve? I know that cocking a conventional hammer for a big valve can be difficult.
Lloyd-ss
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havent seen bigbores here..some 25 cal...but i heard there are some using the same set up..an air shotgun, chambering a 44 mag shell filled with shot,( havent seen it yet)..
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I wonder how hard it would be to cock a swing hammer that was powerful enough to fire a big bore with a big valve? I know that cocking a conventional hammer for a big valve can be difficult.
Lloyd-ss
I guess it would depend some on the range of motion and more on the thumbs ability to draw back the hammer vs pulling back a conventions charging bolt. Thumbs are powerful but so is the fore arm.
What about your PCP pistol? How difficult is that one to cock?
Tom
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tom this is the swing when its opened,the pic is a little blurry, but you can see that there is a swing that opens the breech.
(http://i1353.photobucket.com/albums/q674/plinker81366/Facebook/Mobile%20Uploads/208441_479812278758544_2096528818_n.jpg)
Now that is an interesting design. Is this something you have built?
This is why guns appeal to me so much, it's all about form follows function and there is always one more unique form to improve the function. This is where the beauty is.
Tom
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I wonder how hard it would be to cock a swing hammer that was powerful enough to fire a big bore with a big valve? I know that cocking a conventional hammer for a big valve can be difficult.
Lloyd-ss
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What about your PCP pistol? How difficult is that one to cock?
Tom
Tom, I don't think we can compare the hammer force on my prototype PCP pistol to the hammer force for other PCP pistols. Its internals are a bit abnormal and don't require too much of a hammer hit. The hammer is not hitting a conventional valve stem, nor is it hitting the stem of a conventional valve. If that makes any sense.
Lloyd
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I had a Korean pistol at one time, with the external hammer, way powerful but got hardly any shots. I think it was LD suggested to just use synthetic washers over the valve pin, to whatever thickness you wanted, to get less power/more shots. Kind of a pre-cursor to the BStaley Marauder o-ring mod. Point is, there are other ways to 'tune' an external hammer than weight and spring strength, so if you like the look, go for it.
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I had a Korean pistol at one time, with the external hammer, way powerful but got hardly any shots. I think it was LD suggested to just use synthetic washers over the valve pin, to whatever thickness you wanted, to get less power/more shots. Kind of a pre-cursor to the BStaley Marauder o-ring mod. Point is, there are other ways to 'tune' an external hammer than weight and spring strength, so if you like the look, go for it.
+1
good points
Lloyd-ss