A .357 air gun regulated to shoot 81 grain JSB'S @ 900fps, also equates to 97 grain slugs at 850fps. It starts at a 4200psi fill and gives (pm info, no way of telling if all gauges are on) roughly 16 good shots, ending at 2700psi.
Now, let's just say 15 good shots & assume they're all within a 10fps spread at most. I know, everything has to be sorted, weighed, no blow by, etc to get single digit spread.
My main questions are as follows, and please understand I truly have a math disability. This equates to 100 psi per shot. I'm guessing the reg is set at 2700psi, but I don't think it takes 2700psi on a 81 grain .357 surface area (it would be over 2x the pressure as it's under 1/2 inch, almost 1/3rd so maybe triple 2700psi?) to move a 81 grain pellet at 900fps.
Now, besides the fact that most people don't want a 4-5' rifle, or longer, so companies give on efficiency by gaining appeal in a shorter barrel. I don't know the formulae for optimal air usage L=length/D=diameter/W=weight/P= pressure; but I'd sure like to learn it. Anyway, this subject is a .357 WAR with Cothran valve & Cobra regulator. I don't know barrel length.
I'm asking what it really takes in pressure to push this 81 grain at 900fps. I noticed my usual rule of thumb, add or subtract 10fps for each grain, did NOT apply here according to members info of 900fps w/ 81 grain & 850fps, same setting on a 97.? Morrill slug. I'd have estimated a drop roughly of as much as 170fps. Maybe this 10fps per grain works for spring guns, but I'm obviously way off here as he only dropped 50fps.
So besides the general math question of formulae, how much pressure is really pushing on that 81g .357, what rifles are most efficient, most powerful, most consistent, AND, most importantly, most accurate? Let me make an observation.
I think most of us know, slugs & Diabolo skirted pellets are VERY different. Very few barrels can shoot both pellets & slugs accurately at all distances. Let's assume all ammo is perfect & consistent. The pressure (this is my main question, remember?) Created by my Sumatra. 25 simply shreds the skirt right off soft lead JSB King 25.43's at anything past TP#6-7 max. In fact, TP#1 is just enough to send it through the barrel and bounce off a pillow or sink to bottom of 5 gallon bucket. It mics exactly at .251. I've re-shot these "sized" pellets and they'll do well. They hit higher though on TP#4 where I shoot the Kings normally at 32 yards. Less friction, higher POI.
I can switch to 33.95 soft JSB'S and these have larger, thicker skirts. I can turn power up on these to maybe TP#9-10.
Now, the only slug I've tried so far is what came with this LNIB Sumatra from Mr. Lindt. Thank you SO much. As good as they come to deal with. The slugs in question are now discontinued but they're Air Venturi blue plastic box 50 grain .253 solid core, round nose, 90° back that is concave to a depth of 0.030" (Starrett depth gauge). If swage they take a bit of pressure but will size out at .251.
Starting with a .251 slug, of 40 grains maximum, and a design that's air gun friendly for high pressure (where the diabolo skirt was never meant for these speeds, initial blast to get it going) why is it that we seem to have problems getting anywhere near even 0.100 let alone around 0.120-0.140BC like a .22LR, short?
I don't know. Any answers? As I wrote this I found out none of my CPHP'S are even engaging the 10 year old barrels L&G's. Looked under a scope. Not the least bit. It's amazing it shoots as good as it even does but time to get a Maximus barrel on her as I have like 5K CPHP'S in tins. $7.00 @ Wally World & good to 30-50 yards out of any of my .22's
Now, let's just say 15 good shots & assume they're all within a 10fps spread at most. I know, everything has to be sorted, weighed, no blow by, etc to get single digit spread.
My main questions are as follows, and please understand I truly have a math disability. This equates to 100 psi per shot. I'm guessing the reg is set at 2700psi, but I don't think it takes 2700psi on a 81 grain .357 surface area (it would be over 2x the pressure as it's under 1/2 inch, almost 1/3rd so maybe triple 2700psi?) to move a 81 grain pellet at 900fps.
Now, besides the fact that most people don't want a 4-5' rifle, or longer, so companies give on efficiency by gaining appeal in a shorter barrel. I don't know the formulae for optimal air usage L=length/D=diameter/W=weight/P= pressure; but I'd sure like to learn it. Anyway, this subject is a .357 WAR with Cothran valve & Cobra regulator. I don't know barrel length.
I'm asking what it really takes in pressure to push this 81 grain at 900fps. I noticed my usual rule of thumb, add or subtract 10fps for each grain, did NOT apply here according to members info of 900fps w/ 81 grain & 850fps, same setting on a 97.? Morrill slug. I'd have estimated a drop roughly of as much as 170fps. Maybe this 10fps per grain works for spring guns, but I'm obviously way off here as he only dropped 50fps.
So besides the general math question of formulae, how much pressure is really pushing on that 81g .357, what rifles are most efficient, most powerful, most consistent, AND, most importantly, most accurate? Let me make an observation.
I think most of us know, slugs & Diabolo skirted pellets are VERY different. Very few barrels can shoot both pellets & slugs accurately at all distances. Let's assume all ammo is perfect & consistent. The pressure (this is my main question, remember?) Created by my Sumatra. 25 simply shreds the skirt right off soft lead JSB King 25.43's at anything past TP#6-7 max. In fact, TP#1 is just enough to send it through the barrel and bounce off a pillow or sink to bottom of 5 gallon bucket. It mics exactly at .251. I've re-shot these "sized" pellets and they'll do well. They hit higher though on TP#4 where I shoot the Kings normally at 32 yards. Less friction, higher POI.
I can switch to 33.95 soft JSB'S and these have larger, thicker skirts. I can turn power up on these to maybe TP#9-10.
Now, the only slug I've tried so far is what came with this LNIB Sumatra from Mr. Lindt. Thank you SO much. As good as they come to deal with. The slugs in question are now discontinued but they're Air Venturi blue plastic box 50 grain .253 solid core, round nose, 90° back that is concave to a depth of 0.030" (Starrett depth gauge). If swage they take a bit of pressure but will size out at .251.
Starting with a .251 slug, of 40 grains maximum, and a design that's air gun friendly for high pressure (where the diabolo skirt was never meant for these speeds, initial blast to get it going) why is it that we seem to have problems getting anywhere near even 0.100 let alone around 0.120-0.140BC like a .22LR, short?
I don't know. Any answers? As I wrote this I found out none of my CPHP'S are even engaging the 10 year old barrels L&G's. Looked under a scope. Not the least bit. It's amazing it shoots as good as it even does but time to get a Maximus barrel on her as I have like 5K CPHP'S in tins. $7.00 @ Wally World & good to 30-50 yards out of any of my .22's
