Posted: 3/9/2018 3:29:20 AM EDT
|
I'm wondering if there's any way to determine MPI of one load on a rifle zeroed on irons for another load, relative to the trajectory that the rifle is zeroed on.
The rifle is being zeroed on 7.62 NATO ball ammo at 200m with the sight at the 200m setting. I'd like to figure out where Federal GMM 168s will impact using the same point of aim used when shooting the former type of cartridge. Seems like there should be some way to figure this out mathematically, but Google searches are worthless to this end and I'm just not finding the info that I need. Or is this something I'll just have to shoot and find out that way? I'm heading out to go shoot in the morning. Using a ballistics calculator I was able to find out the trajectory for each, but it is based on the idea that the rifle is zeroed for each cartridge. The trajectories don't look dramatically different if I were to zero for one and shoot it, and then zero for the other and shoot it, but I'm not sure what to do with the data that I have to see where I should be hitting with one cartridge with the rifle zeroed for the other. Also, does anyone know the BCs for the British and Belgian NATO projectiles? I can only find the G7 BC for the American M80 projectile and have been using that, but the ammo I'm shooting right now uses the British projectile design. I doubt they are more than marginally different. |
The finest opportunity ever given to the world was thrown away because the passion for equality made vain the hope for freedom.
-Lord Acton
-Lord Acton
| At the very least, I think you need to shoot both rounds at the same distance and POA to see how the POIs compare at that distance. Then, depending on what degree of precision you want/need, you can stick your data in a ballistic calculator and start putting things together... I think you can assume that the bullets have similar BC for the sake of this exercise. If you get real BC data later, you can substitute that where applicable for tables that are closer to reality. |
|
Originally Posted By Reorx:
At the very least, I think you need to shoot both rounds at the same distance and POA to see how the POIs compare at that distance. Then, depending on what degree of precision you want/need, you can stick your data in a ballistic calculator and start putting things together... I think you can assume that the bullets have similar BC for the sake of this exercise. If you get real BC data later, you can substitute that where applicable for tables that are closer to reality. I'm going to start off at 25m and go from there. I would like to know if there's a way to do this mathematically since I have other rifle/ammo combos I'm wondering about with respect to similar circumstances, such as with my Mosin Nagant. The sights are calibrated for a 200 grain projectile and the light ball stuff is hitting so high that by 300m I'm almost entirely off paper with the rounds sailing over the target when I aim at the ground with the sights on the corresponding setting. If there was a way to compare trajectories given a zero for the former cartridge without wasting a bunch of ammo that'd be awesome. |
The finest opportunity ever given to the world was thrown away because the passion for equality made vain the hope for freedom.
-Lord Acton
-Lord Acton
| If you zero the rifle with each type of ammo at the same (pick your favorite common distance - 100 yards?) and you have the information necessary to put into a ballistic calculator to generate a table (bullet info, MV, atmospherics, etc.) you should be able to generate ballistic tables for each type of ammo zeroed at the same distance so you can compare the tables and know where each ammo is in comparison to the others out of the same rifle... that's the only mathy way I know how to do it. There might be a calculator that can do what you want but I have never seen one... |
|
Well, at 25m the 168 grain GMM ammo has a MPI a bit higher than the Malaysian ball given the same POA. A comparison of the trajectories, which of course presume that the rifle is zeroed for the cartridge in question (as opposed to another), show the GMM hitting over 1/4" above POA at 25m, but I'm not sure how that corresponds to a zero on the ball ammo.
After I moved out to 100m (with plans to end the day at 300m), things got weird. I got the rifle zeroed on the Malaysian ball ammo at 25m, which based on the tables should mean about the same POI relative to POA at 200m, which is what I want. But when I went to 100m, with the target stapled near the bottom of the backer, aiming at the bottom of the black, I found no impacts. Happened again. I shot at a rock near the target stand and the round impacted the ground well in advance of the rock. I decided to aim at the top of the white of the target (about 13" square) and the MPI ended up being at about the centre of the 6" black, maybe a bit below that (eyeballing it). According to the ballistics tables, I should be hitting 2.7" (JBM) or 2.8" (Hornady) above the POA. Instead I'm hitting several inches below POA. I didn't bother going out further at that point, especially since it was getting close to sunset and I wanted to get out of the desert area I was at before dark. I'll have to go out and shoot again. I really need to find some milsurp ball ammo for comparison. |
The finest opportunity ever given to the world was thrown away because the passion for equality made vain the hope for freedom.
-Lord Acton
-Lord Acton
|
Originally Posted By Reorx:
If you zero the rifle with each type of ammo at the same (pick your favorite common distance - 100 yards?) and you have the information necessary to put into a ballistic calculator to generate a table (bullet info, MV, atmospherics, etc.) you should be able to generate ballistic tables for each type of ammo zeroed at the same distance so you can compare the tables and know where each ammo is in comparison to the others out of the same rifle... that's the only mathy way I know how to do it. There might be a calculator that can do what you want but I have never seen one... |
The finest opportunity ever given to the world was thrown away because the passion for equality made vain the hope for freedom.
-Lord Acton
-Lord Acton
|
Try Hornady's 4DOF calculator: https://www.hornady.com/team-hornady/ballistic-calculators/#
Set up the ballistics for what you know your zero is. Once you have that, then check the use zero angle box in the firearm section. Your known information should get you your angle of departure. Then using that same angle, you can change bullet and velocity and have a pretty good idea where it'll go. |
|
Originally Posted By TripletDad:
Try Hornady's 4DOF calculator: https://www.hornady.com/team-hornady/ballistic-calculators/# Set up the ballistics for what you know your zero is. Once you have that, then check the use zero angle box in the firearm section. Your known information should get you your angle of departure. Then using that same angle, you can change bullet and velocity and have a pretty good idea where it'll go. I've been using their regular calculator to get ballistics tables. Something's not right with my trajectory, in any case. It differs radically from what the calculators say it should be. |
The finest opportunity ever given to the world was thrown away because the passion for equality made vain the hope for freedom.
-Lord Acton
-Lord Acton
|
Trying to do it "mathematically" without comparing zero and POI from each round at 200 at best is going to give you a rough estimate. You really need to see how each round actually performs through a given rifle/barrel.
What did was pick my gold standard round, in this case FGMM. I zeroed it for 200 yds and recorded the data. For any new rounds or loads I leave my scope or sights set for that standard and see where it goups at 200 relative to the standard. I record that data, and make the relative adjustment for a given range. For example, if a round grouped 1.25 moa high and .75 moa right compared to my standard at 200, and my chart or calculator says com up 6 moa elevation and right 1.5 moa for a given distance and a wind for the *current round*, I would adjust elevation up 4.75 moa and windage right .75 moa instead to account for the difference. Edit: noticed my mistake and changed it "standard round" to "*current round*". |
|
Do you know the 100 yard poi or each load? Say the 168 is 2.375" high and 2" left.
If so a ballistic solver will tell you. I have multiple loads for each of my precision rifles but use one mechanical zero on my scope, I never re-zero. To answer your question, no, there is no way to(accurately) estimate poi at any given distance if you don't know a base line distance poi. |
MOA ALL DAY- 169 Arfcom rifles confirmed
|
Originally Posted By popnfresh:
Do you know the 100 yard poi or each load? Say the 168 is 2.375" high and 2" left. If so a ballistic solver will tell you. I have multiple loads for each of my precision rifles but use one mechanical zero on my scope, I never re-zero. To answer your question, no, there is no way to(accurately) estimate poi at any given distance if you don't know a base line distance poi. While shooting at 25m, the GMM MPI was higher than the Malaysian MPI after I got it zeroed to POA. I never got to try the GMM at 100m, as it was getting late and my Malaysian trajectory was far off from the tables. I only have 15 rounds of GMM left to spare, so I need to use it wisely. At 25m, using the Malaysian ball ammo, MPI relative to POA should be virtually identical to MPI at 200m based on the tables. Zeroed at 25m, at 100m my MPI was 7" below POA when it should be 2.8" above POA. I have no idea why there is about a 10" discrepancy. Without knowing what exactly is going on, I don't think I can figure things out with respect to the GMM. I'm going to try to get some Hirtenberger ball ammo and see how that compares (and see if I stop getting case separations; so far this Malaysian stuff seems like garbage). Windage at 25m is about the same for both loads, though. What is a "ballistic solver"? |
The finest opportunity ever given to the world was thrown away because the passion for equality made vain the hope for freedom.
-Lord Acton
-Lord Acton
|
Alright, so I measured the targets and looked at the tables.
At 25m, the Malaysian should be hitting less than 1/200" above POA. At 100m it should be hitting a bit over 2.8" above POA. This is for a 200m zero. For a 200m zero with 168gr. GMM, MPI should be 0.16" above POA at 25m, and 3.15" above POA at 100m. On paper, the average MPI for the Malaysian was 0.15" above POA at 25m once I got it dialed in, which is less than half a click in adjustment from zero. At 100m, MPI for a 15-round group (all groups shot at 25m were 5-rounders for both loads) was 9.8" below POA, which is 12.64" below where it should be at that range based on the ballistics table, maybe a bit lower, actually, since it's a tad above where it should be at 25m (12.8" perhaps?). The average MPI at 25m for the GMM was 1.35" above POA, for an average difference of 1.2" over the MPI of the Malaysian ball at that range. |
The finest opportunity ever given to the world was thrown away because the passion for equality made vain the hope for freedom.
-Lord Acton
-Lord Acton
|
Originally Posted By bigstick61:
Alright, so I measured the targets and looked at the tables. At 25m, the Malaysian should be hitting less than 1/200" above POA. At 100m it should be hitting a bit over 2.8" above POA. This is for a 200m zero. For a 200m zero with 168gr. GMM, MPI should be 0.16" above POA at 25m, and 3.15" above POA at 100m. On paper, the average MPI for the Malaysian was 0.15" above POA at 25m once I got it dialed in, which is less than half a click in adjustment from zero. At 100m, MPI for a 15-round group (all groups shot at 25m were 5-rounders for both loads) was 9.8" below POA, which is 12.64" below where it should be at that range based on the ballistics table, maybe a bit lower, actually, since it's a tad above where it should be at 25m (12.8" perhaps?). The average MPI at 25m for the GMM was 1.35" above POA, for an average difference of 1.2" over the MPI of the Malaysian ball at that range. Going by a chart is not going to cut it. There are far too many variables to use generic data. Ballistic solver predicts drops at various distance from your known zero. It requires muzzle velocity, ballistic coefficient of the bullet, zero, sight height over bore and air temp at a minimum to get close. Different but similar loads can have drastic poi differences at 100yds, I think maybe your 25m zero may be too close to show that so that could be why it seems so far off at greater distances. But you really cannot go by published muzzle velocity data, it can be so far off that it would be useless for what you are doing. It(MV) needs to be measured for your rifle at the time and conditions in which you are shooting. |
MOA ALL DAY- 169 Arfcom rifles confirmed
|
It's unlikely that I can get a chrono in time before my last opportunity to go shoot prior to Cola Warrior (I used factory figures adjusted for barrel length for GMM, and other people's chrono results, similarly adjusted, for the ball ammo). I'll just have to zero for GMM when I go shooting this week, as the trajectory at longer ranges seems to be quite off. Excluding flyers (I consistently get one low and to the left in my 5-shot groups), I'm hitting over a foot above POA and 3.3 inches to the right in terms of MPI at 200m with the sights zeroed for ball ammo. At 25m it was on average 1.8" high and 0.7" to the right relative to POA. Had a round keyhole with one group at 200m. There were a few twigs from a bush in its path, but if that can cause that, then 1:12 must not stabilize the 168 grain GMM well. I'd still like to know how to calculate trajectory for one load relative to the one a rifle is zeroed for, given appropriate inputs. I asked my brother the other day and he started talking about LaGrangian this, and Hamiltonian that. |
The finest opportunity ever given to the world was thrown away because the passion for equality made vain the hope for freedom.
-Lord Acton
-Lord Acton
|
Originally Posted By bigstick61:
I'd still like to know how to calculate trajectory for one load relative to the one a rifle is zeroed for, given appropriate inputs. I asked my brother the other day and he started talking about LaGrangian this, and Hamiltonian that. A 12 twist should be plenty for 168s. You need to know both zeroes (poi at a distance). Example Sight height= .75" Standard atmos conditions Load A is zeroed at 100 yds Load B is 12" high at 100 yds Load A is 175smk .238G7 2550fps Load B is 168smk .218G7 2600fps Load A 25 yds 0.0" 100 yds 0.0" 200 yds -5.4" 300 yds -18.2" 400 yds -39.4" Load B 25 yds +3.0" 100yds +12.0 200yds +18.7" 300yds +18.0" 400yds +9.3" |
MOA ALL DAY- 169 Arfcom rifles confirmed
|
I know this is an old post, but I figured I'd chime in. I am trying to do the same for 77gr and 62 gr 5.56. This is what I came up with. What we really want to know is the angle of departure of the bullet in relation to the optic. Without actually diving deep into the formulas, there is a crude way to do this. 1) Use a ballistic calculator to find the rise of the bullet at a very close distance (when gravity hasn't yet worked its magic with any significance) I used 5 yards. At 5 yards (180 inches) my 77gr rises .39 inches according to the calculator. 2) Put the new BC, grain weight, and velocty of the 62 grain bullet, and see what happens. For me, the rise at 5 yards at the same zero distance was .34 inches. Not what we want. 3) Adjust the zero distance on that new load in small increments, until your rise at 5 yards is the same as the first load's (.39 inches in this example). Turns out for the loads I was looking at, my 200 yard 77gr zero is equivalent to a 235 yard zero with the 62gr load. I have not checked IRL to verify the accuracy of this method, but it is theoretically sound, albeit not very precise. Cheers! |
|
Fire at zero distance. Measure offset. Say 2moa up, 2moa left. Figure ballistics. -3moa at 300yds from zero. Ok, but you impact 2moa high. Your actual drop should be 1moa at 300yds. Say drop at 500yds is supposed to be 12moa. Then your actual impacts should be 10moa low. In a rough, DIY field sense, this is as good as you're going to get. Just a simple offset. With a highpower rifle, I'd want to do this at 100yds for zero, to maximize the flat shooting. |
Nut coal is best coal. Now available in 87lb bags.
|
Originally Posted By barkwild: I know this is an old post, but I figured I'd chime in. I am trying to do the same for 77gr and 62 gr 5.56. This is what I came up with. What we really want to know is the angle of departure of the bullet in relation to the optic. Without actually diving deep into the formulas, there is a crude way to do this. 1) Use a ballistic calculator to find the rise of the bullet at a very close distance (when gravity hasn't yet worked its magic with any significance) I used 5 yards. At 5 yards (180 inches) my 77gr rises .39 inches according to the calculator. 2) Put the new BC, grain weight, and velocty of the 62 grain bullet, and see what happens. For me, the rise at 5 yards at the same zero distance was .34 inches. Not what we want. 3) Adjust the zero distance on that new load in small increments, until your rise at 5 yards is the same as the first load's (.39 inches in this example). Turns out for the loads I was looking at, my 200 yard 77gr zero is equivalent to a 235 yard zero with the 62gr load. I have not checked IRL to verify the accuracy of this method, but it is theoretically sound, albeit not very precise. Cheers! What Fritz said.............. You can't use any mathematical solutions until you see how differently the 2 cartridges shoot in your rifle. You have to shoot them first, there is no way around that. Shoot the 2 cartridges out as far as you can.... ie 200yds. Then compare the different point of impacts.......... THEN use the charts to compare the two. ie I run a 200yd zero, so I shoot load "A" which is zero'd. When I shoot load "B" it may be say 4" left and up from "A." THEN use your theoretical charts to compare the trajectories..... But to honest, save yourself the headache..... make note of the 2 zero's, tape them to the rifle. Shoot "A", use "A" zero. Shoot "B", use "B" zero. THEN run the charts for whatever further zero you don't have. |
|
Originally Posted By bigstick61: I'm wondering if there's any way to determine MPI of one load on a rifle zeroed on irons for another load, relative to the trajectory that the rifle is zeroed on. No, there isn’t. Many people seem to think that the difference in the points of impact between two different loads fired from a rifle with the same windage and elevation settings on the sights are due solely to the difference in the exterior ballistics (trajectory) of the two loads. This notion is false. There isn’t a ballistic program on the planet that can predict these changes in the points of impact and trying to do so using the different muzzle velocities and different ballistic coefficients of the two different loads is a wild-goose chase. The difference in the points of impact between two different loads (with the same sight settings on the rifle) out to say 75-100 yards will be due in large part to matters of interior ballistics; barrel harmonics and recoil vectors for instance. These components may not be the same from rifle to rifle and are not predictable using ballistic software. The only way to know what the difference in the points of impact will be, is to shoot the different loads in your weapon. To illustrate the above points with a specific example, the graph below shows that there is nearly no discernable difference in the trajectories of the Sierra 55 grain BlitzKing and the Hornady 70 grain GMX out to 100 yards.  Yet, when I actually fired the Hornady 70 grain GMX load from an AR-15 that had been zeroed for POA=POI at 100 yards with the 55 grain BlitzKings, the group of the 70 grain GMX impacted 2.9” LOW and 3.7” TO THE LEFT of the point of aim.  ... |
All that is necessary for Trolls to flourish, is for good men to do nothing.
In God We Trust. Everyone else must post data.
In God We Trust. Everyone else must post data.
|
Originally Posted By Molon: No, there isn’t. Many people seem to think that the difference in the points of impact between two different loads fired from a rifle with the same windage and elevation settings on the sights are due solely to the difference in the exterior ballistics (trajectory) of the two loads. This notion is false. There isn’t a ballistic program on the planet that can predict these changes in the points of impact and trying to do so using the different muzzle velocities and different ballistic coefficients of the two different loads is a wild-goose chase. The difference in the points of impact between two different loads (with the same sight settings on the rifle) out to say 75-100 yards will be due in large part to matters of interior ballistics; barrel harmonics and recoil vectors for instance. These components may not be the same from rifle to rifle and are not predictable using ballistic software. The only way to know what the difference in the points of impact will be, is to shoot the different loads in your weapon. To illustrate the above points with a specific example, the graph below shows that there is nearly no discernable difference in the trajectories of the Sierra 55 grain BlitzKing and the Hornady 70 grain GMX out to 100 yards. https://www.ar15.com/media/mediaFiles/28568/differences_points_of_impact_70_gmx_vs_5-1791811.jpg Yet, when I actually fired the Hornady 70 grain GMX load from an AR-15 that had been zeroed for POA=POI at 100 yards with the 55 grain BlitzKings, the group of the 70 grain GMX impacted 2.9” LOW and 3.7” TO THE LEFT of the point of aim. https://www.ar15.com/media/mediaFiles/28568/point_of_impact_shift_001-1793075.jpg ... This topic has come to mind again for a different rifle. In trying to find answers my thread was one of the first results, lol. Right now I am trying to figure things out with my m/39 Mosin-Nagant. Its sights are calibrated for D166, which has a standard velocity of 2,340 fps out of a 27" barrel (which is what the m/39 has). It launches a projectile with a rebated boat tail that weighs 200.6 grains and has a G1 BC of .448 and a G7 BC of .224. The closest thing I have found is LVE Extra Match. Based on values given for a different barrel length I expected that out of a 27" barrel the velocity would be around 2,546 fps. Average measured with a chrono from 5 rounds was 2,639 fps. It uses a projectile that has a conventional boat tail and weighs 200.6 grains, with a G1 BC of .491 and G7 BC of .259. My problem is that the trajectory is extremely high. Even worse with other ammunition. I was aiming at the bottom of the target and the rounds were sailing over the target. Even at 150m, the lowest setting, I was having this issue. At close ranges I had to shoot very low to get on paper. My friend shimmed the front end, placing shims under the handguard. He went as far as possible, to the point that the wood removed under the barrel exposed the channel for the cleaning rod. So we reached the limit there. This helped a lot, but it is still shooting high. I know that the LVE Extra Match ammo, having a higher IV and BC will impact higher than D166 at a given range. But I am trying to figure out by just how much. Ballpark, at least. Doesn't have to be perfect. I want to know if the way the rifle shoots is good enough for now, or if it needs more adjustment (maybe shims on the other end). D166 with a 150m zero should have POA equal POI at 33 yards. At this range and sight setting, my rifle shoots the LVE ammo such that the MPI is about 5" high. If a rifle was zeroed for LVE and was put on the 550m setting, then it would produce similar results at 33 yards, based on plugging the numbers into a ballistic calculator. I am trying to find answers mathematically because I cannot find any D166 ammo. Surplus is a collector item and I have yet to come across it. Lapua made it commercially, but if they even make it at all today, it does not seem to get imported, although it has been years ago in the past. But it is basically unavailable. I am a college student renting a room and just have no way to set up for reloading, so loading my own is out for the time being. So I cannot just fire some D166 and see how it compares or what it does. I also have a ton of light ball ammo which seems basically unusable out of my Mosin-Nagant, as the issue with it shooting high is much worse. I am going to shoot tomorrow and try to get better data and then try the rifle at 550m and see if this all corresponds well. |
The finest opportunity ever given to the world was thrown away because the passion for equality made vain the hope for freedom.
-Lord Acton
-Lord Acton
|
I also gave up on the 168gr. GMM ammo that was the original topic of this thread. I eventually got a sense of the trajectory out of a 17" barrel using irons calibrated for Belgian NATO ball ammo out of a 21" barrel. But accuracy was only marginally better than with ball ammo and the rounds were not stabilized very well. If they so much as touched a leaf they would start keyholing. Any disruption and the rounds would tumble in flight. A FAL uses a 1:12 twist barrel, which should be sufficient, but it seems not. I ended up trying Hornady 155-grain ELD-M, which has now been discontinued. Not only did my rifle shoot noticeably smaller groups, but I discovered that the trajectory out of a 17" barrel corresponds almost exactly to the trajectory of NATO ball ammo out of a 21" barrel, which meant that the sights can be used at their settings and POA should about equal POI at the range at which the sight is set. And no stability issues. With the ELD-M ammo gone, the slightly lower velocity LE version of it not being sold to the general public by Hornady or its distributors, and me being unable to reload at present, I have substituted Hornady Black 155-grain AMAX, which is close enough for now. In fact, with this ammo I have been able to use the irons to hit targets past 700 yards with iron sights out of my FAL. I don't believe I could have done this had I continued to try to use the GMM. |
The finest opportunity ever given to the world was thrown away because the passion for equality made vain the hope for freedom.
-Lord Acton
-Lord Acton
|
OP, you are stuck in a false economy loop. Find or load the best ammunition you can to do what you want. Swapping between new factory purpose-precision and surplus ammunition is futile. You are discovering (it seems at some cost for ammo, gas, and time), a zero is not a zero until confirmed. You are not building enough consistent data before changing variables (running out of or changing bullets, brands, weights, and loads). You state you want data for 7.62 NATO yet you are using ammo from at least three or four different countries. NATO standardization doesn't mean you'll get the same results, trajectories. or groups and zeros from different weapons (16-, 17-, 18-, 20-, and 24-inch barrels). |
|
Originally Posted By Sinister: OP, you are stuck in a false economy loop. Find or load the best ammunition you can to do what you want. Swapping between new factory purpose-precision and surplus ammunition is futile. You are discovering (it seems at some cost for ammo, gas, and time), a zero is not a zero until confirmed. You are not building enough consistent data before changing variables (running out of or changing bullets, brands, weights, and loads). You state you want data for 7.62 NATO yet you are using ammo from at least three or four different countries. NATO standardization doesn't mean you'll get the same results, trajectories. or groups and zeros from different weapons (16-, 17-, 18-, 20-, and 24-inch barrels). I'm not really looking for this for the FAL anymore. I found something that worked for me. Right now it is more for the Mosin-Nagant. LVE Extra Match is the absolute closest thing I could find to the ammo for which its sights are calibrated. But it is shooting way, way too high. Before my friend installed some shims I was aiming at the ground in front of the target stand and still having most rounds go over the target, that's how bad it was. This was especially pronounced with easier to find ammo, like Soviet spec light ball ammo, of which I have quite a lot. While I know it is hitting way too high, I do know that the LVE will impact higher at a given range for which the sights are calibrated (the calibration is fixed, so a zero for another ammunition is only good at the setting at which it was done, and the degree to which it is hitting high is beyond what can be fixed by adjusting elevation via swapping front sight blades with taller ones). The question is roughly how much higher should it be? I know that different rifles, manufacturers of ammo, etc. can cause variations but there should be a sort of ballpark range in which the performance should fall for each type made to a given spec. I just want to be able to calculate the following: For sights calibrated for Finnish D166 ammo, using that ammo, assuming the zero is correct for that type of ammo generally, what should be the difference in point of impact at a given range for LVE Extra Match compared to D166? Obviously it is a general figure and the exact difference would need to be determined by shooting, but I am trying to get a ballpark figure so that I have some idea of what steps to take to try to get this rifle to shoot lower. Reloading is not an option currently and D166 is not commercially available (I'm not sure if Lapua even makes it anymore, but if they do, it does not appear to be imported anymore, and what's left here is collector ammo that rarely pops up, and at collector prices). But in the future when I have a better space for setting up for reloading, I intend to do so. But in the meantime I want to be able to shoot the rifle with the ammo that I can get or have, and to do this some things need to be changed, such as more shims in the stock under the action. I just want to make sure it is around where it should be for the correct ammo once I can make it while making it usable with other ammo. Right now it is shooting better than it was, but is still way too high. At the 150m setting the POI is high enough that it is the equivalent of a 406m zero for that setting. I had to set up a second target below the one I was trying to shoot to use as an aiming point just to get on paper on the latter, even at 100m. I feel like there should be a mathematical way to calculate this. |
The finest opportunity ever given to the world was thrown away because the passion for equality made vain the hope for freedom.
-Lord Acton
-Lord Acton
|
Not accounting for recoil, harmonics, and whatever else moves during barrel time, I think the closest will be setting the ballstic calculator to not adjust for zero range which should should treat the bore as parallel to the ground. What model of Mosin Nagant? Have you tried with/without bayonet? |
"Technique isn't something that can be taught. It's something you find on your own." - Bunta Fujiwara
|
Originally Posted By HighpowerRifleBrony: Not accounting for recoil, harmonics, and whatever else moves during barrel time, I think the closest will be setting the ballstic calculator to not adjust for zero range which should should treat the bore as parallel to the ground. What model of Mosin Nagant? Have you tried with/without bayonet? Finnish m/39 |
The finest opportunity ever given to the world was thrown away because the passion for equality made vain the hope for freedom.
-Lord Acton
-Lord Acton
|
OP: Holy cow, just holy cow. Look, I'm more confused than ever on what you are trying to accomplish here. OK, so you have an M39 that is shooting high. This is common, very common. You can get other front sights for it and make the adjustments that way to get on paper, with what ever ammo you are using. You want a higher front sight than you have now. And be done with this. Otherwise: NO, there is no mathematical way to figure out some difference in various ammos. And yes, like Brophy mentioned, some of these Mosins are zeroed with a Bayonet attached. If you have one, try it with that as well. So PLEASE go get a higher front sight, get on paper and be done with this. Now there is a mathematical way of figuring which front sight you will need. PS: Here: https://jackweigand.com/point-of-impact-adjustment-formula/ |
|
Originally Posted By TGH456E: OP: Holy cow, just holy cow. Look, I'm more confused than ever on what you are trying to accomplish here. OK, so you have an M39 that is shooting high. This is common, very common. You can get other front sights for it and make the adjustments that way to get on paper, with what ever ammo you are using. You want a higher front sight than you have now. And be done with this. Otherwise: NO, there is no mathematical way to figure out some difference in various ammos. And yes, like Brophy mentioned, some of these Mosins are zeroed with a Bayonet attached. If you have one, try it with that as well. So PLEASE go get a higher front sight, get on paper and be done with this. Now there is a mathematical way of figuring which front sight you will need. PS: Here: https://jackweigand.com/point-of-impact-adjustment-formula/ They don't make front sight blades high enough for the adjustments needed. If it wasn't for shimming the fore end it would be shooting way, way higher than it is now. Shooting this high is not normal. No one who has looked at it thinks the degree to which it is shooting high is normal. And no, m/39s were not zeroed with the bayonet attached. Finnish bayonets are hundreds of dollars, too. |
The finest opportunity ever given to the world was thrown away because the passion for equality made vain the hope for freedom.
-Lord Acton
-Lord Acton
|
Originally Posted By bigstick61: They don't make front sight blades high enough for the adjustments needed. If it wasn't for shimming the fore end it would be shooting way, way higher than it is now. Shooting this high is not normal. No one who has looked at it thinks the degree to which it is shooting high is normal. And no, m/39s were not zeroed with the bayonet attached. Finnish bayonets are hundreds of dollars, too. Sir: A cursory look around the internet shows numerous sources of "tall," "extra tall," M39 front sights. Thats how I zeroed mine BTW, but I digress. Using the equation I linked and the highest replacement front sight I found (.374), it provides 58-59" inches of elevation drop at 100yds. Or just short of 5 feet. The reason for so many front sights being available is that is how they zeroed them at the factory or during refurbishing. How else would they? Thats also why they marked their height in mm on top, so you could easily adjust them. Lastly since you seem to have one the manuals (to know they didn't zero with bayonets attached like other Moisins), did it not explain the zeroing process using the various front sights? Did it also not explain that like alot of military rifles of that era, to use a "belt buckle" POI so despite ranging errors and stress, hits would be probable? Since you had maybe 2ft of elevation to play with? (With the rifle shooting high along its trajectory) And then when we (modern civilian shooters) get them and try a precise POI, are frustrated because they are shooting high? |