Wanted to ask you guys a question. I worked up some handloads for my 308 (fn tsr xp with 20" barrel). 168 gr matchkings with 39.5 grains of H4895. I didn't have a chronograph so what I did was to zero at 89m (as per rangefinder) and then shoot at 251m. I know those are wierd measurements but it is not my range I have a 1cm/100m per click scope so I keep it all in metric. Anyway. I needed to come up 12 clicks at that distance (30cm). I tried to plug that into a ballistic calc to estimate the velocity and got about 2550-2600 closer to 2600. Does this sound right out of a short barrel? It sounds faster than it should to me. Any tips are appreciated. Still looking for someone in my area with a chrony to make sure. Thanks
Velocity
- Thread starter polarcow
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Re: Velocity
I ran the numbers in JBM with 2500fps, 2" sight height, and 29.00inHg. Using a 97yd (89m) zero, I got 12 clicks at 270yd (251m).
Make sure your units are all correct and atmospherics are accounted for with your ballistic app.
I ran the numbers in JBM with 2500fps, 2" sight height, and 29.00inHg. Using a 97yd (89m) zero, I got 12 clicks at 270yd (251m).
Make sure your units are all correct and atmospherics are accounted for with your ballistic app.
Re: Velocity
How would a 20 moa base affect the sight height that you put in? I measured at the rear of the scope where it should be highest and got betwee 4.5cm and 5cm (1.77 and 1.96). Is this negligible? Also, Temp9, what did you use for click value? MOA or cm's? Thanks.
How would a 20 moa base affect the sight height that you put in? I measured at the rear of the scope where it should be highest and got betwee 4.5cm and 5cm (1.77 and 1.96). Is this negligible? Also, Temp9, what did you use for click value? MOA or cm's? Thanks.
Re: Velocity
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: polarcow</div><div class="ubbcode-body">Wanted to ask you guys a question. I worked up some handloads for my 308 (fn tsr xp with 20" barrel). 168 gr matchkings with 39.5 grains of H4895. I didn't have a chronograph so what I did was to zero at 89m (as per rangefinder) and then shoot at 251m. I know those are wierd measurements but it is not my range I have a 1cm/100m per click scope so I keep it all in metric. Anyway. I needed to come up 12 clicks at that distance (30cm). I tried to plug that into a ballistic calc to estimate the velocity and got about 2550-2600 closer to 2600. Does this sound right out of a short barrel? It sounds faster than it should to me. Any tips are appreciated. Still looking for someone in my area with a chrony to make sure. Thanks
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Your Scope is incorrectly marked 1cm@100m, it's .1mrad.
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: polarcow</div><div class="ubbcode-body">Wanted to ask you guys a question. I worked up some handloads for my 308 (fn tsr xp with 20" barrel). 168 gr matchkings with 39.5 grains of H4895. I didn't have a chronograph so what I did was to zero at 89m (as per rangefinder) and then shoot at 251m. I know those are wierd measurements but it is not my range I have a 1cm/100m per click scope so I keep it all in metric. Anyway. I needed to come up 12 clicks at that distance (30cm). I tried to plug that into a ballistic calc to estimate the velocity and got about 2550-2600 closer to 2600. Does this sound right out of a short barrel? It sounds faster than it should to me. Any tips are appreciated. Still looking for someone in my area with a chrony to make sure. Thanks
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Your Scope is incorrectly marked 1cm@100m, it's .1mrad.
Re: Velocity
Well it subtends the same linear distance at 100 meters so I don't think that is the issue. Twelve clicks at 250 meters would still be 30cm (11.8 inches at 273.4 yards)correct?
Well it subtends the same linear distance at 100 meters so I don't think that is the issue. Twelve clicks at 250 meters would still be 30cm (11.8 inches at 273.4 yards)correct?
Re: Velocity
The difference would be negligible. Sight height shouldn't matter all that much. Moving from 2" to 1.5" sight height changed the POI only .9" (~.08 mils) at 270 yards. However, I believe you would measure from the center of the objective lens to the center of the bore to be completely correct.
I was going by .1 mil clicks. So that would be 1.2 mil.
Polarcow, you are correct. 1cm at 100m is exactly .1 mils. Mils are more definite than MOA for these applications.
The difference would be negligible. Sight height shouldn't matter all that much. Moving from 2" to 1.5" sight height changed the POI only .9" (~.08 mils) at 270 yards. However, I believe you would measure from the center of the objective lens to the center of the bore to be completely correct.
I was going by .1 mil clicks. So that would be 1.2 mil.
Polarcow, you are correct. 1cm at 100m is exactly .1 mils. Mils are more definite than MOA for these applications.
Re: Velocity
ok so I got a chance to stretch out my rifle/round combo to 800 yards. With a 100 yard zero, it dropped 1.5 mils to 300, 5.7 to 600, 7.6 to 700 and a whopping 10.4 to 800. I tried to duplicate the data in a ballistic calculator but it is dropping so fast past 600 and 700 I couldn't make it work. Assuming 2500fps it should only drop 9.4 at 800 so one whole mil not a small deviation at that range. I am using sierra mk 168 still with the same load/powder combo. I have a 1-12" twist so I don't know if the bullets are tumbling but it doesn't appear so looking at the target. Also, there was a slight (3-5mph) wind right to left. Any thoughts as to why it starts dropping way faster than predicted?
ok so I got a chance to stretch out my rifle/round combo to 800 yards. With a 100 yard zero, it dropped 1.5 mils to 300, 5.7 to 600, 7.6 to 700 and a whopping 10.4 to 800. I tried to duplicate the data in a ballistic calculator but it is dropping so fast past 600 and 700 I couldn't make it work. Assuming 2500fps it should only drop 9.4 at 800 so one whole mil not a small deviation at that range. I am using sierra mk 168 still with the same load/powder combo. I have a 1-12" twist so I don't know if the bullets are tumbling but it doesn't appear so looking at the target. Also, there was a slight (3-5mph) wind right to left. Any thoughts as to why it starts dropping way faster than predicted?
Re: Velocity
The 168smk suffers from a poor boat tail design that causes it to act all kinds of funky as it approaches Mach 1. With your light(ish) load and short barrel, I'd guess you're approaching mach 1 at 750 yards or so.
If the ballistic calculator solution seems legit from 100-700, I'd use those data points, and forget the 750+ data.
If you'd like to shoot out past 700 or so, consider a different bullet, such as the 155 Scenar, 175smk, etc etc etc.
The 168smk suffers from a poor boat tail design that causes it to act all kinds of funky as it approaches Mach 1. With your light(ish) load and short barrel, I'd guess you're approaching mach 1 at 750 yards or so.
If the ballistic calculator solution seems legit from 100-700, I'd use those data points, and forget the 750+ data.
If you'd like to shoot out past 700 or so, consider a different bullet, such as the 155 Scenar, 175smk, etc etc etc.
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