The Science Behind Shooting: 7mm SAW vs the 6’s

SAW

West Texas Ordnance 7mm SAW

Wildcat cartridges are nothing new in the long-range shooting community. If there is a way to make something better or more efficient someone will make it so. I happen to be a huge fan of the Precision Rifle Blog and noticed that a 7mm cartridge made it into last years top 100 shooters. It is the 7mm SAW and it is West Texas Ordnances brain child.

PRS Applications

If you read the referenced article from Cal over at the Precision Rifle Blog you will see that PRS shooters primarily favor the 6mm and 6.5mm calibers. They bring a lot to the table shooting a high bc round with low recoil. In a competition where you will be shooting multiple strings a day and are required to spot your own misses for adjustments this makes them ideal. So what benefits do we gain with the 7mm SAW?

According to West Texas Ordnance

SAW
https://westtexordnance.com/7mm-saw/
Ballistic coefficients

So how do the ballistic coefficients compare from a 6mm to a 6.5mm to a 7mm? Using Hornady ELD-Match ammunition here is the data.

SAW
http://m.hornady.com/store/6mm-.243-108-gr-ELD-Match/
SAW
http://m.hornady.com/store/6.5mm-.264-140-GR-ELD-Match/
SAW
http://m.hornady.com/store/7mm-.284-162-GR-ELD-Match/
Terminal ballistics

Using the data from West Texas Ordnance on their barrel length and power tests of 7mm SAW as well as data from Copper Creek Cartridge Co for 6 and 6.5mm Creedmoor I ran the ballistics charts below. All data is run at a 0 DA with 10 MPH cross winds at 90°.

SAW
6mm Creedmoor 108GR ELD-MATCH 3080 FPS
SAW
6.5 Creedmoor 140GR ELD-MATCH AT 2810 FPS
SAW
7mm SAW 162GR ELD-MATCH AT 2911 FPS
SAW
Bullet Drop Comparison
SAW
Wind Drift Comparison
Recoil

Using Shooters Calculators Recoil Calculator and basing the results off of available load data we can see that the 7mm SAW does produce more recoil then both the 6.5 and 6mm Creedmoor. The rifle weight was set to 16 lbs for all 3 calibers and it is worth noting that this is without a brake installed. Most brakes on the market popular in practical precision matches can reduce recoil as much as 60%.

Overview

Looking at the data above we can see that the 7mm SAW does have advantages over both the 6mm and 6.5mm calibers. It has a significant advantage in bullet drop and wind drift. Another important fact is the barrel life. The 6mm and 6.5mm calibers are known to burn barrels faster than other calibers out there. The downside seems to be a higher recoiling rifle. Hopefully we will see more data as time goes on and be able to compare how it shoots with a highly effective muzzle brake installed.

West Texas Ordnance is currently working on bringing quality reloading tools to the market and according to their website they should be available soon. I can honestly say that I am impressed with the data and will be closely following this caliber as a possible option when it comes time for my next build or rebarrel.

So do you think we will see some changes in the PRS world in regards to the 7mm SAW? Let us know what you think in the comments!

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The Science Behind Shooting: Ranging Targets

The Science Behind Shooting: Ranging Targets

In an effort to take the voodoo magic out of finding the distance of an unknown target today we are going to cover how to properly range a target using your scope reticle.

Luckily for us there are proven formulas that we can use to estimate range. The first thing that we need is the height of the target. Be it a known target at an unknown distance or an animal we can usually associate a height to our target based of experience. It is important to note that we need to be as precise as possible when we determine the height of our target as it can affect the range and our corrections. Here is an example of target sizes provided by the Applied Ballistics Toolbox app:ranging

Ranging with Mils

The formula for finding an unknown distance in Mils is the following:

(Height of target in YARDS x 1000) ÷ mils= Distance to target in yards

So assuming you are ranging a medium sized deer of an estimated height of 17.5 inches and the height from belly to back reads as 1 Mil through your scope the math would look like this:

((17.5 inches ÷ 36 inches) x 1000) ÷ 1 = distance to target in yards

(.4861111 x 1000) x 1 = distance to target in yards

486.1111 x 1 = 486.1111 yards

An important part of this formula is ensuring that you divide the target in inches by 36 inches or 1 yard. Failing to do so will give you incorrect data. To show you the importance of estimating height of target correctly lets assume that the deer we ranged was not in fact a medium deer with a height of 17.5″ from belly to back but was a large deer with a belly to back height of 19.5″:

((19.5 inches ÷ 36 inches) x 1000) ÷ 1 = distance to target in yards

(.5416666 x 1000) x 1 = distance to target in yards

541.6666 x 1 = 541.6666 yards

As you can see two inches makes a difference of 55.5555 yards in target range. How would that effect our chance of a first round hit? Using my .308 and shooting 178 GR Hornady BTHP at 2550 FPS at a 0 DA and a G1 BC of .53 factoring in 10 MPH cross winds at 90° the data looks like this:rangingranging

We would be off target by .7 mils at 541 yards. In this case our point of impact would be low by 13.6332 inches. More than enough to miss hitting critical mass on the deer for a clean kill. Your windage correction would be off by .1 mil or 1.9476″ at 541 yards. Getting the correct range is important. It ensures that your data is correct. If we get the range wrong we will not be using a correct firing solution which will lead to misses.

Ranging with MOA

The formula for calculating distance if you use MOA is as follows:

(Target height in inches x 95.5) ÷ target height in MOA = distance to target in yards

So if we had a medium deer with an assumed belly to back height of 17.5″ that measured 3.4 MOA the math would look like this:

(17.5 inches x 95.5) ÷ 3.4 = distance to target in yards

1671.25 ÷ 3.4= 491.54411 yards.

When we talk about the formula for ranging targets in MOA the biggest error I see pertains to the constant number in the formula. The 95.5. Some people will use 100 instead of 95.5. We use the 95.5 number because 1 MOA at 100 yards is not an inch, it is 1.047 inches. The 4.5 off from 100 takes this extra .047 inches into account and gives you a more correct range estimation. Below is the same target height and MOA height using 100 in place of the 95.5:

(17.5″ x 100) ÷ 3.4 = distance to target in yards

1750 ÷ 3.4= 514.70588 yards

At this range using 100 in place of the 95.5 adds 23.16177 yards to our correct number. This error will only compound itself as the range becomes farther away and will not allow you to get an accurate firing solution.

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The Science Behind Shooting: Mils and MOA

The Science Behind Shooting: Mils and MOA

Today we are going to be looking at the practical applications of angular measurement systems. These are Mils and MOA. We use both in our scope reticle and adjustment turrets. Using Mils or MOA is a personal preference of the user and the application. Mils is not inferior to MOA and MOA is not inferior to mils. 

MILS and MOA- Introduction


We all know that 1 Mil at 100 yards is 3.6 inches and that 1 MOA at 100 yards is 1.047 inches. When we increase distance we increase what 1 Mil or 1 MOA is relative to the distance of our target. The purpose of this article is not cover what we already know to be true but rather to look at the topic from a different point of view.

 

Mils

Mils

I recently posted the above image on the Long Range Shooting group and gave the following information. The red circle is your aiming point on a target at 300 yards. The blue circle is where your round impacted. The scope is a ffp and using mils. How much did you miss by and what is your correction?


There are a couple of right answers to this question. For example we can find how many inches off we were. If we take 1 Mil at 100 yards which is 3.6 inches we can do that math. It looks like this:


3.6 (1 Mil at 100 yards)×3 (distance to target being 300 yards)=10.8 (1 Mil at 300 yards)x3 (number of Mils low that the bullet impacted below the aiming point)=32.4 inches. Assuming you are running a 1/10th Mil scope turret we then divide 32.4 inches by 1.08 (1/10th of a Mil at 300 yards) and get 30 clicks of the turret in adjustments or 3 Mils.


Math takes time in between shots that we may or may not have time for on the hunt, in the field, or on the stage we are currently shooting. So what is the easier and faster method of adjustment? Our reticle is our ruler.  We had the correction long before we came off the scope to do the math. Our impact was 3 mils low. Our corrected firing solution is to dial or hold 3 mils high. 

 

MOA

 

Mils





If I run a similar example for MOA using the picture above and the following: Target is at 300 yards. The red circle is your point of aim the blue circle is your point of impact. Scope is FFP the math would look like this:


1.047 (1 MOA at 100 yards)×3 (distance to target being 300 yards)=3.141 (1 MOA at 300 yards)x10(number of MOA low that the bullet impacted below the aiming point)=31.41 inches. Assuming you are running a 1/4th MOA scope turret we can then divide 31.41 inches by .78525 (1/4th of a MOA at 300 yards) and get 40 clicks of the turret in adjustments or 10 MOA of adjustment.

Thinking in mils and moa

If you stop thinking about what the actual distance that our adjustments are in terms of inches or centimeters and look at and think of all of our adjustments as the measurement system our scopes are set up in we will be faster and more accurate. We can then measure our misses right from our scopes using the reticle system provided like a ruler and make faster follow-up shots without wasting time to back into a number that our reticle has already given us.

It doesn’t matter if we need 1 Mil or MOA of adjustment at 100, 300, 500, 800, or 1000 yards. Although that adjustment works out to be a different number in inches or centimeters at those ranges on our scopes it is the same 1 Mil or MOA adjustment.

It is worth mentioning that these formulas do have a time and a place on the range or in the field. If you are trying to range a target of known size at an unknown distance for example. I will cover those formulas in a future article. 

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