Pellet Speed Obsession

Forums PCP Airguns Pellet Speed Obsession

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    Bob_O
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    When my rifle came to me, it was tuned for 30fpe (18gr at 870fps).  I happen to like a flatter trajectory for long range shooting so I cranked it up to 950fps (36fpe).

    Yes my shot count went down, but accuracy did not suffer at all and it made 20% more power, which helps to take down pigeons at 100+ yds.

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    heavy-impact
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    Bob_O

    When my rifle came to me, it was tuned for 30fpe (18gr at 870fps).  I happen to like a flatter trajectory for long range shooting so I cranked it up to 950fps (36fpe).

    Yes my shot count went down, but accuracy did not suffer at all and it made 20% more power, which helps to take down pigeons at 100+ yds.

    What's your regulator pressure at?

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    Bob_O
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    150

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    Nick47
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    I'm leaning in your direction Centercut in terms of feels good and delivers TKO.  However, many of the newer rifles have dial up HS and Reg adjustments to adjust for max power. The AMP Reg is a tool to that end. Like Bob said, "Max power without mods" . Bob has an AMP Reg and if he has the HS adjuster he can max tune his rifle. In fact, you could power tune for various pellets/slugs. Just wondering if you can return to a previous tune consistently and the wear and tear. Certainly crosses a new bridge. I think I'll wait awhile for my next PCP.

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    heavy-impact
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    Bob_O

    150

    You must have a 500mm barrel. Shooting the 18gn JSB I average 975 fps on 100 bar from a 600mm barrel but the Impact may have more plenum volume than the crown.

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    Bob_O
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    Ah yes, that was before I converted to 600mm.

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    edosan
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    Bob_O

    I would like to try that, maybe this summer.

    Very easy to do (took me 5 minutes) …go ahead no need to wait that much…you will shoot the 24gn @ 950ish +- for sure just doing that and you will take pressure off the reg ;)

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    heavy-impact
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    Bob_O

    Ah yes, that was before I converted to 600mm.

    I haven't worked on a Crown but the port feeding the barrel transfer port on an Impact is about 7mm. The .22 barrel transfer port is about 5mm so I flare it deep to cover the port feeding it and then elongate the barrel transfer port towards the muzzle about 10-12% and break the sharp edges. Then open the pellet probe larger than the port that feeds it and knife edge the edges of that hole for the easiest turn and maximum airflow. Both parts cost about $30 total to replace if you wanted to return to original condition.

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    edosan
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    I bought the replacements, cheap and both are there..no use to them ;) (Probe and brass)

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    Centercut
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    Nick47

    I'm leaning in your direction Centercut in terms of feels good and delivers TKO.  However, many of the newer rifles have dial up HS and Reg adjustments to adjust for max power. The AMP Reg is a tool to that end. Like Bob said, "Max power without mods" . Bob has an AMP Reg and if he has the HS adjuster he can max tune his rifle. In fact, you could power tune for various pellets/slugs. Just wondering if you can return to a previous tune consistently and the wear and tear. Certainly crosses a new bridge. I think I'll wait awhile for my next PCP.

    Agree…  We all say "flatter", but what is the real difference at 100 yards between 865 and 925 FPS with the 18.1 grain JSB? If sighted in at say 45 yards (my preferred sight in distance for the Cricket mini), how much drop do you save by going to the higher velocity? In the big scheme of things, the answer is "not much", or about an inch or two.  So instead of a 4 mil dot drop, you have a 3.5-ish mil dot drop.  At 100 yards that's approximately 1.8 inches.  So instead of 14.4 inches you have 12.6 inch drop.  Not really seeing the benefit of a "flatter" trajectory here, but that's IMHO only.  Also, it takes about 5 or 6 FPE to kill a ground squirrel, less for a pigeon. At 100 yards, the 18.1 shot at 865 FPS still have triple the amount of energy necessary for a clean kill.  So again, what's a few more FPE getting?   I have nothing against maxing out your speed and power. Is it cool? Yes. Is it kinda bad ass? Yup. Is it really necessary to be a successful varmint hunter? I think not…  ;)

    Here's a photo of a ground squirrel head shot with the 18.1 JSB at 855 FPS muzzle velocity, distance of 98 yards. This is the exit wound… Its a little bloody due to the squirrel twitch and flop on loose dirt. You can see the entrance wound to the right at 2 o'clock if you look closely.

     

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    Nick47
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    As Tweeter say's , "Tinker On"…. You guys are Tops

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    Nick47
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    As Tweeter say's , "Tinker On"…. You guys are the Tops

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    tor47
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    There is probably a difference on shooting slugs, and pellets. As I understand it slugs need fast spin to be stable. All depending on the barrel, they might be unstable at "pellet" speeds. I agree with you about going to as fast as possible with pellets is not always beneficial, as you sacrifice allot in other areas. The gun might be loud, it use allot of air, might have to clean more often. And it might in some cases not be as accurate (flyers). I personally would probably use the velocity which gave me the most accuracy, but if I could find the same accuracy at some lower speed, and have the other benefits, I would probably choose the litle slower.

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    Bob_O
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    Nick,

    Yes, you can return to a previous tune no problem without worry of wear and tear.  It's just a reg adjustment.

    In fact, if you have different caliber barrel kits and/or different pellets that you have different tunes for, all that is needed is to dial in those settings from one setup to the other and you're golden.

    🙂

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    heavy-impact
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    tor47

    There is probably a difference on shooting slugs, and pellets. As I understand it slugs need fast spin to be stable. All depending on the barrel, they might be unstable at "pellet" speeds. I agree with you about going to as fast as possible with pellets is not always beneficial, as you sacrifice allot in other areas. The gun might be loud, it use allot of air, might have to clean more often. And it might in some cases not be as accurate (flyers). I personally would probably use the velocity which gave me the most accuracy, but if I could find the same accuracy at some lower speed, and have the other benefits, I would probably choose the litle slower.

    For 25 years before I discovered adult airguns I shot .22 rimfire CBs which is a 29gn .22 bullet at 720 fps. They were very accurate from the same rifles that shot 40gn bullets over 1300 fps while making about the same sound as an airgun.

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    Nick47
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    Ok keep my AMP when I get rifle back…

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    Haganaga
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    From what I’ve read on here, slugs also create more friction, so more power is needed to get the slug down the tube at the same rate as a pellet. If it’s true that slugs need to spin faster to stabilize, then I would imagine a slug barrel would have a faster twist rate or indeed you would need even more power to push the slug faster down the tube to attain slug specific spin rate. Have I got this right?

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    heavy-impact
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    Haganaga

    From what I’ve read on here, slugs also create more friction, so more power is needed to get the slug down the tube at the same rate as a pellet. If it’s true that slugs need to spin faster to stabilize, then I would imagine a slug barrel would have a faster twist rate or indeed you would need even more power to push the slug faster down the tube to attain slug specific spin rate. Have I got this right?

    A faster rate of twist is required as projectiles get longer. A diabolo pellet flies like an arrow or shuttlecock, drag on it's skirt keeps the head pointed forward and a little spin helps. Bullets (slugs) are completely dependent on spin for stabilization so barrel intended for them usually has a faster twist which also creates more friction.

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    Haganaga
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    So slugs do eat more air, by a lot it seems, over pellets.

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    heavy-impact
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    Haganaga

    So slugs do eat more air, by a lot it seems, over pellets.

    Porting helps the .22 a lot.

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