Out of Box Factory configuration

[rhorgan]

Does anyone know how man fps and any other out of box factory settings on the Mrod?

I thought I remembered 880 fps but since I do not have a Chrono, I am using a ballistic model that tells me with a ballisitic coefficient of .025 ( which I believe the Crosman .177 premiers are),zeroing in at 32 yards will require 3 mil dot holdover. I was shooting low and re-ran using 800 fps which show 4 mil dot and this was dead on.

[TN_Yankee]

I bought a .177 Mrod from Midway USA a few weeks ago, and just got my chrono the other day. My rifle is stock - I haven't adjusted anything on it.

I chrono'd the CP Ultra Mag, Benjamin Discovery HP & Air Arms Diabolo Field Heavy (made by JSB) yesterday. Here's my Ultra Mag data:



First thing I noticed was that there's no curve to my shots - all 3 pellets started at their highest velocity and went down from there. I've definitely got some adjusting to do.

Mike

[rhorgan]

Very very cool...Thanks so much for sending along

[lamerabbit]

Yankee:

You need to adjust your gun as you should be able to get at least 30 consistent shots at that power level, so something is out of wack with your gun. I shoot the same pellets, (CPH), at just over 900 FPS, and get over 30 consistent shots with only a 2400 PSI charge...........

Anyway, Good Luck and happy Shooting

Jim

[Supercharged86]

Hi Mike, First thing that I noticed from your data is your chrony placement, 5' is good for a powder burner but way to far for a PCP (or air in general), the ideal placement is 18". Although, it won't change much but your shots are actually a little faster than mentioned. Likewise, If shot count isn't important for you, (as it isn't for me), than having a bell curve isn't necessary. In fact, I have mine tuned the exact same way, I want my first 5-10 shots to be the fastest, the rest doesn't matter. If you want the bell curve then you need to tune for the mid point of your psi range, In other words, if you want to fill to 2900 and shoot to 2000 then tune it for max fps at 2450; this is basically how the "A-Team" tuning guide explains it. Cheers. Steve

[lamerabbit]

Actually Steve:

You are not necessarily correct about the chronograph placement; I always use ten feet, because with pre-charged guns I always use lubed pellets, and the greater distance keeps the chronograph from reading the oil as it were. I remember when those little plastic muzzle chronographs came out. It was interesting to see that most spring guns shot their most consistent velocity that way with a good tuned TX 200 shooting the same muzzle velocity almost every shot. However, with most chronographs the farther away you are the more variation you will get in your muzzle velocity to a point and that point can be anywhere between 25 yards to past 50 yards, with air rifles, unless there is a problem with the barrel, or pellet/barrel combination.

Most air rifles will get their largest velocity spread around the 25 yard mark, but not always. I tested so many rifles and pellets when I built Air Rifle Ballistics that I can’t even remember the number of rifles used, let alone the number of CP, and CPH dies and over 90 other brands of pellets. I shot everything from Career 707’s to Theoben Eliminators and back again. Not to mention everything from a FWB P70 to a couple of USFT’s. That darn 25 caliber Beeman Kodiak, AKA Webly Patriot made my teeth hurt every time I shot it, in fact they still hurt just from thinking about it.

You are always better off understanding the velocity variation due mostly to pellet stabilization than not. Many assume that if the pellet leaves the barrel at velocity “X” in will always reach the target at velocity “Y” but the truth is it never does! If it did the pellet would always hit the exact same place, with the exception of wind deflection, of course.
If you think I am wrong just chronograph a 22 long rifle high velocity round across a chronograph at 25 yards and keep doing it, you will be amazed at the velocity spread, and by the time you are done you will wonder how the darn this ever hits the target!

Velocity variation is a good part of the accuracy equation, and should be understood by all shooters and that’s just my two cents.

Jim

[TN_Yankee]

Yankee:

You need to adjust your gun as you should be able to get at least 30 consistent shots at that power level, so something is out of wack with your gun. I shoot the same pellets, (CPH), at just over 900 FPS, and get over 30 consistent shots with only a 2400 PSI charge...........

I don't want to hijack rhorgan's thread too much further, but this is what I want to do. I'm looking for high air efficiency off a relatively low fill, giving me a high number of consistent shots. I'm running off a 4500 psi SCBA, but I don't have any hunting opportunities right now, so I'm just punching paper. I figure any pest birds that come along into my yard will still be adequately dispatched with these power levels.

5 feet did turn out to be a little far for the chrono. My rifle rest isn't very heavy, so it would occasionally slide on the old table I'm using outside as I ran the bolt, which would in turn misalign the barrel & chrono sensors. I'll likely bring it in a couple feet closer.

I'll start a new thread when I get the chance to start adjusting the rifle from its factory settings. Hard to find the time, and the weather doesn't want to cooperate, either.

Thanks, guys.

Mike

[Supercharged86]

Sorry you disagree Jim, just going by what I was told by Ray and Hans.

[Lammy1000]

Yankee:

You need to adjust your gun as you should be able to get at least 30 consistent shots at that power level, so something is out of wack with your gun. I shoot the same pellets, (CPH), at just over 900 FPS, and get over 30 consistent shots with only a 2400 PSI charge...........

I don't want to hijack rhorgan's thread too much further, but this is what I want to do. I'm looking for high air efficiency off a relatively low fill, giving me a high number of consistent shots. I'm running off a 4500 psi SCBA, but I don't have any hunting opportunities right now, so I'm just punching paper. I figure any pest birds that come along into my yard will still be adequately dispatched with these power levels.

5 feet did turn out to be a little far for the chrono. My rifle rest isn't very heavy, so it would occasionally slide on the old table I'm using outside as I ran the bolt, which would in turn misalign the barrel & chrono sensors. I'll likely bring it in a couple feet closer.

I'll start a new thread when I get the chance to start adjusting the rifle from its factory settings. Hard to find the time, and the weather doesn't want to cooperate, either.

Thanks, guys.

Mike

Hi Mike, If you want a very efficient tune in .177 with enough punch for crows, then try 2H, 10S and ~2 Valve. I fill to 2200 psi and get 45 shots with an avg velocity of 880 fps,extreme spead of 35 fps. Very accurate out to 70 yards and I get well over 2000 shots from a 3000 psi, 80cf scuba. Pellet is 7.9 gr Crosman Premier hp. Lou

[TN_Yankee]

Thanks for the tuning info, Lou. Its sounds real good, but the first time around the Crosman HPs didn't shoot too well for me. I'll try them again after some tuning, though.

Thanks,

Mike