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Post by Richard on Jul 20, 2010 19:14:58 GMT -5
I have been noticing this for quite some time now............When I check the orfice on my vent liner after a shooting session, I notice that I get two different dimensions. If I put my needle gauge in from the tip, I get a smaller dimension than when it is feed thru the recessed head (the part that faces the powder charge) I get as much as a couple of thousandths difference. The "torch tip cleaner" will go thru the "head" but not come out the tip? So, if the tip end is .032" and he head end is .034"....................That still leaves a .032" hole that is holding back pressure from the primer/bolt face right? Do I then consider my vent liner to be worn out when the hole in the head is at .036" (or thereabouts) or when the "tip" opens to .036". It seems to me that as long as there is any portion of the hole at .032" that my vent liner is protecting the primer? ?? I have been changing when the "head" end is over .036" but maybe I don't really need to?? In my mind I am thinking the reason is because the tip has gotten more hardened in the manufacturing process due to its exposure? The "head" end is recessed. I know when drilling them, once you break thru the hardening, they drill quite easily until you get back to the end. Could be this harder tip is protecting it? Or, is it because the "head end" is facing the powder charge and takes the brunt of the heat and force? Comments? Richard
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Post by ET on Jul 20, 2010 20:43:38 GMT -5
Richard
I have found vent liners to erode this way and the smallest dimension is the one I go by. I consider the smallest dimension doing the regulating/restricting of flame/pressure. As for the head hole size developing slightly larger I suspect it is exposed to higher temp and pressure trying to drill back into the hole. It’s travel back is short lived thus the uneven wear through the vent liner hole. Just an educated guess.
Ed
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Post by jeff on Jul 20, 2010 20:50:54 GMT -5
I also watch this very close and see the same results, usually about 2 thousandths difference. It seems that I have noticed this more with 70 gr H4198 than any of the mid 40 grain charges of other powders. My 50 pacnor shoots best when I keep the tip no bigger than 32 thous. I buy mine from RW. Jeff~
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Post by boarhog on Jul 21, 2010 0:20:07 GMT -5
I have noticed the same thing on my VLs, and have wondered which measurement to use to decide when to replace.
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Post by Jon on Jul 21, 2010 2:25:09 GMT -5
Richard. Having less experiance than most I'll give my 2 cents. I can understand why it would wear from the powder end faster your loosing a little of the smaller size how far you would let it go till it would affect accuracy is a good question? I would think you would have close to the same safety as far as pressure reaching the primer. I would still think you are dealing with flow. I used to do a lot of head flow bench work and it used to amaze me what made a differance. Jon
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Post by moto357 on Jul 21, 2010 13:50:59 GMT -5
Jon, you mentioned flow.. reminds me of the angle cuts on a valve in a head, as im sure you are plenty aware of. i learned of a guy a few years ago who does 7 angle cuts on valves for increased flow, as the angles increase its flow. perhaps this has something to do with what you are talking about? makes sense to me, causing the head of the VL to wear quicker with the pressures and heat that little hole sees every time the trigger is pulled..
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Post by Richard on Jul 21, 2010 18:33:56 GMT -5
ET............I'm sort of thinking along the lines as you! I have acquired enough data on loads that I should be able to tell the difference when shooting with an "old" vent liner that still has a .032" hole. Edge, RB.................... ? Any words of wisdom??? Richard
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Post by edge on Jul 22, 2010 7:43:20 GMT -5
I have not used a vent liner in many years so I really can't help much. My first drill bushing plug was back in the Lil'Gun days, which burned out vent liners to 0.038+ in about 40 shots or less. To me that was unacceptable since I would just get through a range session when the POA would start to drift again! I decided to try a #72 drill bushing with a 0.025 diameter hole x 1/2 inch long. After several hundred Lil'Gun shots I removed the BP and measured the hole. While the picture below may not be clear, it is to scale. The primer crud buildup is the white hatched area, the red is the bushing, and the colored lines and dimensions show where that size gage pin would stop when inserted from either end. I saw wear from Both ends, but greater wear from the muzzle end. Also since I use a fouled plug I am sure that my wear pattern would be different from what someone would see when using a clean BP. edge.
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Post by deadon on Jul 22, 2010 8:41:20 GMT -5
Edge.can I use one of those in my new pacnor ,where do I get one and why isn"t everyone using them?
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Post by Richard on Jul 22, 2010 13:35:14 GMT -5
Edge..................my question, more specifically is this: As long as "any part"(front or rear) of the vent liner/bushing or whatever delivers the flame from the primer to the powder............is within the .031' to .034" range, is the rearward pressure curtailed as though the entire length of the vent is .031 to .034? In other words, am I wasting vent liners, throwing them away, because one end is .035" and the other is .032"? Richard
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Post by edge on Jul 22, 2010 14:21:13 GMT -5
IMO, Yes edge.
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Post by rangeball on Jul 22, 2010 14:25:28 GMT -5
Edge.can I use one of those in my new pacnor ,where do I get one and why isn"t everyone using them? You could contact SMI to see if they can make you a savage spec BP. They offer a carbide bushing, it's what I have in my BP from them. No wear that I can measure yet. Going from memory I think it may have been Pete in PA that was offering stainless BPs with bushings. I think RB may have been as well. Edited to add another thought. If you have a savage BP, perhaps SMI can just add a carbide bushing to it without having to create a whole new plug?
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Post by deadon on Jul 22, 2010 14:35:49 GMT -5
Edge.can I use one of those in my new pacnor ,where do I get one and why isn"t everyone using them? You could contact SMI to see if they can make you a savage spec BP. They offer a carbide bushing, it's what I have in my BP from them. No wear that I can measure yet. Going from memory I think it may have been Pete in PA that was offering stainless BPs with bushings. I think RB may have been as well. Edited to add another thought. If you have a savage BP, perhaps SMI can just add a carbide bushing to it without having to create a whole new plug? Hmmmmm, That is something else to ponder Thanks Rangeball
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Post by dannoboone on Jul 22, 2010 20:00:12 GMT -5
Edge.can I use one of those in my new pacnor ,where do I get one and why isn"t everyone using them? I got one from dave d.'s friend, Pete. It's a stainless BP with a bushing installed. I've misplaced the info, but Dave would have it.
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Post by Dave W on Jul 22, 2010 20:42:59 GMT -5
Anyone interested can contact Pete @ 610-923-9234 or pamachine@epix.net
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Post by minst7877 on Jul 22, 2010 22:16:45 GMT -5
I have a plug that RB customized with a hard recessed drill bushing. At that time you sent him the plug and he did the work on it. Still in my gun and working fine.
DC
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Post by boarhog on Jul 23, 2010 1:52:02 GMT -5
I just bought a PA Machine stainless bushing plug from Onecardchuck. I haven't popped a cap yet, but am anxious to do so. One thing I am curious about, is if the bushing can be replaced when/if it eventually wears? I assume that it is pressed into the plug. I noticed that Travers Tools had drill bushings listed in one of their sale fliers. They didn't say Carbide, but did claim them to be Rockwell 65 or so hardness. I have no idea how that compares to Carbide?
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Post by Dave W on Jul 23, 2010 4:25:27 GMT -5
Unless Pete changed things, the bushing is pressed into the plug from the primer end to eliminate the chance of the bushing being blown out the barrel. He was using hardened bushings, carbide would jack the price up.
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Deleted
Deleted Member
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Post by Deleted on Jul 23, 2010 17:29:02 GMT -5
Dave W, I bought a batch of plugs from pete and they had the bushings pressed in from the front....BAD IDEA.... on my friends rifle the bushing came out, blew the bolt back and cut his face while he was hunting in Iowa last season. he was suppose to contact pete about this but I dont know if he did. My other friend checked his and his bushing had started backing out so he abandoned his plug. I had already replaced mine with a new style hex plug recessed by RB, so a heads up to all that might have one. you might want to contact Pete about a replacement.by the way I am not bashing Pete or his work, he is a very nice guy and does excellent work......Bill
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Post by Dave W on Jul 23, 2010 18:39:37 GMT -5
Dave W, I bought a batch of plugs from pete and they had the bushings pressed in from the front....BAD IDEA.... on my friends rifle the bushing came out, blew the bolt back and cut his face while he was hunting in Iowa last season. he was suppose to contact pete about this but I dont know if he did. My other friend checked his and his bushing had started backing out so he abandoned his plug. I had already replaced mine with a new style hex plug recessed by RB, so a heads up to all that might have one. you might want to contact Pete about a replacement.by the way I am not bashing Pete or his work, he is a very nice guy and does excellent work......Bill Sorry to hear that Bill. I'm sure Pete would like to know if there is a problem.
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Post by dave d. on Jul 24, 2010 7:52:48 GMT -5
Dave W, I bought a batch of plugs from pete and they had the bushings pressed in from the front....BAD IDEA.... on my friends rifle the bushing came out, blew the bolt back and cut his face while he was hunting in Iowa last season. he was suppose to contact pete about this but I dont know if he did. My other friend checked his and his bushing had started backing out so he abandoned his plug. I had already replaced mine with a new style hex plug recessed by RB, so a heads up to all that might have one. you might want to contact Pete about a replacement.by the way I am not bashing Pete or his work, he is a very nice guy and does excellent work......Bill :)bill i'm very sorry to hear that.i have contacted pete and will get back to everyone later once i hear from him.
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Post by Richard on Jul 24, 2010 16:01:10 GMT -5
I spoke with Edge about this and believe the better way to do it is as follows: Drill the plug from the "forward" end (not the primer end) but not completely thru to the primer pocket. You need to leave some metal so the bushing cannot come back out to the primer.................Then tap the hole in front of where the bushing ends and screw in a "set screw" with a hole in it. The set screw will keep the bushing from coming forward and allow the flame to pass thru to the powder charge. As far as I am concerned? Now that I have Edge's "Blessing" on not throwing away those GOOD vent liners, I should be able to about double or triple their use. I don't know why this did not occur to me earlier in my ML career Stands to reason, that the smallest part of the hole will control the pressure. Just like an "hour glass!" I guess also the fact the vents were only costing me about $0.25 ea. Richard
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David
Button Buck
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Post by David on Jul 24, 2010 17:06:32 GMT -5
Edge..................my question, more specifically is this: As long as "any part"(front or rear) of the vent liner/bushing or whatever delivers the flame from the primer to the powder............is within the .031' to .034" range, is the rearward pressure curtailed as though the entire length of the vent is .031 to .034? In other words, am I wasting vent liners, throwing them away, because one end is .035" and the other is .032"? Richard Not sure as to if you are wasting vent liners, but in flow and pressure calculations, the length of the restriction is a variable (along with the ID, resistance coefficient, friction factor, velocity, etc). Considering the turbulent nature of high pressure gases in the vent liner, any calculation would be an approximation and only through testing could one determine any impact on accuracy. Sounds like another reason to go to the range. Maybe some targets shot with new vent liners (consistent ID) compared to worn liners (varying ID) shooting the same proven load would provide clues to the answer?
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Post by boarhog on Jul 25, 2010 1:17:38 GMT -5
The Pete's plug I got from Chuck has the bushing on the primer end. He had shot it some, with no evidence that it has moved. On the nose end, the recess is probably 3/4-1" deep. I was wondering what is to keep that end from flame cutting all the way back to the bushing?
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Post by Al on Jul 25, 2010 2:41:37 GMT -5
I spoke with Edge about this and believe the better way to do it is as follows: Drill the plug from the "forward" end (not the primer end) but not completely thru to the primer pocket. You need to leave some metal so the bushing cannot come back out to the primer.................Then tap the hole in front of where the bushing ends and screw in a "set screw" with a hole in it. The set screw will keep the bushing from coming forward and allow the flame to pass thru to the powder charge. As far as I am concerned? Now that I have Edge's "Blessing" on not throwing away those GOOD vent liners, I should be able to about double or triple their use. I don't know why this did not occur to me earlier in my ML career Stands to reason, that the smallest part of the hole will control the pressure. Just like an "hour glass!" I guess also the fact the vents were only costing me about $0.25 ea. Richard McMaster Carr sells "hollow set screws" in various sizes. They are 3/16" thick with the hex all the way thru them. I have some pics someplace of them I'll look up, but as mentioned, they are the best way to hold a bushing in.
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Post by Al on Jul 25, 2010 3:36:15 GMT -5
These were for one of the stock 700ML's shooting BH209, one is for a Savage ventliner, the other for a bushing vent. That particular plug put the bushing right up against the nose of the primer with the idea of reducing some of the carbon build up. Set screw is 3/8 x 24, bushing is 5/16
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Post by Jon on Jul 25, 2010 8:30:06 GMT -5
Al. looks like you have been on top of this. Very informative and good pictures. Thank you for the great input. Jon
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Post by Al on Jul 28, 2010 3:01:34 GMT -5
Al. looks like you have been on top of this. Very informative and good pictures. Thank you for the great input. Jon I've tossed a couple experimenting, , staking will work also. Sometimes I get a little anal making things.
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Post by Richard on Jul 28, 2010 19:45:34 GMT -5
They are "lookin' good Al!" Richard
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Post by bigmoose on Jul 29, 2010 9:40:26 GMT -5
great photo's
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