In this post let’s take a look to see if primer size affects the performance of hand loads in the 6.5 Creedmoor. I’ll be shooting the same brand of brass, powder, and bullets to see if there is anything we can learn from it to improve upon our reloading practices.
Last month, I published Does primer size matter? 6.5 Creedmoor small v. large rifle primer brass comparisons. . I compared the performance of a large rifle primer to a small rifle primer in Starline 6.5 Creedmoor brass. I had selected my two favorite primers, Wolf Large Rifle and CCI 450 Small Magnum Rifle for use in the test. Many readers commented that I was comparing the “best” large rifle primer to a inferior small rifle magnum primer and suggested a comparison of the same brand primers. To that end I have repeated the same test between the CCI 200 (standard large rifle) and the CCI 400 (standard small rifle) primers.
I wanted to make a direct comparison between small and large rifle primer brass. This wouldn’t usually be possible since most brass makers either produce 6.5 Creedmoor brass in large or small rifle primer size. Starline brass offers 6.5 Creedmoor brass in both large and small primer sizes (as does Peterson Cartridge). This means we can make a direct comparison of the two different types of brass. Some manufactures offer a .059″ (1.5mm) flash hole with their small rifle brass; Starline uses a .080″ (2mm) flash hole in both large and small rifle primer versions of their 6.5 Creedmoor brass. You’ll note that the flash hole size isn’t specified in the SAAMI document referenced here.
Comparing hand load data is always interesting, there are so many variables to control for it is hard to get reliable data. Let’s say for instance, in the case of this brass case test, I ran the exact same load in both cartridges. One could argue that the load was optimized for a large or small rifle primer and that it doesn’t necessarily show the benefits of one over the other. To address this, I decided that I would test 5 different charges of the same powder, H4350, with the same bullet (142 SMK). I loaded 10 rounds of each load in each type of brass and fired two five-shot groups at 100 yards on a Rite in the Rain Storm Sight Target. I used a MagnetoSpeed V3 Barrel Mounted Ballistic Chronograph to gather data for each ten shot series. The cases used in this round of testing are 2XF.
Before we get shooting, let’s take a look at the disclaimer below:
WARNING: The loads shown are for informational purposes only. They are only safe in the rifle shown and may not be safe in yours. Consult appropriate load manuals prior to developing your own handloads. Rifleshooter.com and its authors, do not assume any responsibility, directly or indirectly for the safety of the readers attempting to follow any instructions or perform any of the tasks shown, or the use or misuse of any information contained herein, on this website.
For a test rifle I went to my favorite 6.5 Creedmoor rifle.
I built it with parts from Brownells, including:
- Remington 700 short action receiver with “upgraded” one piece bolt
- Proof Research 6.5 mm 1:8″ twist Sendero contour stainless steel barrel
- Timney Calvin Elite 2-Stage trigger
- Badger Ordnance Maximized scope base
- Spuhr ISMS scope mount
- SCHMIDT & BENDER – PMII/LP/MTC/LT 5-25X56MM SCOPE LOCKING TURRET FFP ILLUM. MSR
The chassis is the excellent MDT ESS system. This one is equipped with the folding stock and carbon fiber fore end.
The results of my testing are displayed in the table below.
Primer size versus group size
This graph compares the primer size to the average group size. Smaller is better. You’ll note that the results seem to be pretty evenly matched between small (CCI 200) and large rifle (CCI 400) primers, with the exception of the 42.0 Gr. H4350 group utilizing the small primer.
Primer size versus standard deviation
This graph compares the primer size to the standard deviation (ft/sec). Smaller is better. In 4 out of the 5 loads, the small rifle primer (CCI 400) had a lower standard deviation.
Primer size versus muzzle velocity
This graph compares the primer size to the muzzle velocity. In 3 of the 5 loads the small primer (CCI 400) was faster than the large primer (CCI 200). In 2 of the loads the large primer was faster. The velocities in most loads were remarkably similar.
How did the CCI 200 and 400 stack up against the Wolf Large Rifle and CCI 450 primer?
I was somewhat hesitant to make a direct comparison against the Wolf and CCI 450 primers primarily because the ambient temperature of this test, 94F, was far higher than the last two tests (64F and 57F respectively). Additionally, the brass is now 2XF which I would think would have some (most likely small) effect on the results. With those two caveats in mind, let’s look at how they compare.
It is hard to pick out a clear winner amongst the primers in terms of group size. If you take a look at the 4 most precise loads, 40.8, 41.1, 41.4 and 41.7, you’ll notice the CCI 450 1Xf (light blue) seems to perform a little better than the other primers. It is worth noting that in the virgin brass loads, the CCI 450 (green) works best on the 41.4 grain load, but doesn’t seem to offer any particular advantage in the other loads.
Taking a look at standard deviation, I don’t see a clear winner. It does look like the 40.8 grain load has the lowest average SD amongst the loads.
I also listed the velocities on the table above. You’ll note that the CCI 200 and 400 have the highest velocities for all loads. I’d attribute this to the change in ambient temperature.
Once again, the testing seems to raise more questions than provide answers. The only definitive conclusion I can draw from the data set so far is that this rifle seems to like the 40.8 grain load the best in Starline brass.
To read the first part of this series, please see: Does primer size matter? 6.5 Creedmoor small v. large rifle primer brass comparisons.