Testing Primers

[ninosdemente]

I have been using CCI primers #200 and #450. I have tried #BR4 as well but not many. I got #450 when I was planning to load for AR15, never got to it and just used it for .223 bolt action.

Last week visit to Cabela's I was able to get #400 (3) and #BR2 (4), well because that is all they had available.

How does one test the different brands and its different primer types? How does one determine which one is good enough for your firearm/load? I can think of using the same projectile, powder brand/weight, etc. Keeping the same variables as possible, if applicable. Thanks in advanced.

[Bfglowkey]

My personal opinion and practice:

If I am ONLY changing primer brand/type I test fire 5 rounds and record the velocity etc. if it is vastly off of how the load normally performs, I rework the load. Now caveats to that is sane and smart reloading practice states if you change anything you rework the load. I have found that in my style of reloading ( I rarely if ever run hot loads) I can safely change out primer brands 99% of the time and not have a massively adverse effect. Now if it was brass, powder or bullet... I back down 5-10% of my current kid and work back up. Again...MY practice and MY decision on how I choose to address different primers. When in doubt, rework the load.

[Unclenick]

In rifle cartridges designed for large rifle primers, changing primers usually results in only small if any changes in pressure and velocity, but they can produce significant differences in velocity SD. In rifle cartridges using small rifle primers and in some pistol cartridges for either size primer, there can be more significant differences.

In the 223/5.56 specifically, in a 2006 Handloader article series, Charles Petty produced a velocity change with 55-grain V-max bullets over a fixed charge of Reloader 10X of 3150 to 3300 fps just by changing primers. That's equivalent to about 5% change in the powder charge, according to QuickLOAD. In the 22 Hornet, velocities can not only change significantly, but they can also become quite erratic when the primer has too much power. This appears to be caused by a primer that is too powerful, starting to unseat and move the bullet before the powder charge is burning fast enough to do the job. This means the bullet is in differing proximities to the throat when the powder does take command of the pressure, causing an associated peak pressure variation. The same can happen with pistol cartridges when the powder space is small.

The way I test for this is to try different primers and see which one produces the smallest velocity standard deviation for a 30-shot sample. That's a lot of shooting but it gives you a pretty reliable result. For smaller samples, you really want to perform a separate test to see if the difference is real or random. Usually for 95% (0.95 probability) confidence. Student's T-test is the standard method and it is built into Excel's solvers, but you will have to watch a YouTube video or two to know how to interpret its output numbers.

The reality is that the bigger the difference in SD, the smaller the number of shots you can get away with in your sample, but we have to dig into the complexities of statistics to know how to determine that number. Also, be aware that the standard method of calculating sample standard deviation that is built into your chronograph gets less reliable than some other methods for samples smaller than eight. https://www.shootingsoftware.com/ftp...%20of%20SD.pdf for samples smaller than eight, you divide the extreme spread by a fixed coefficient to get a better estimate.

If you are in a situation where you have to use a smaller sample than eight, you can compare the machine calculation to the result from Bramwell's method, and if they aren't close, refire the test. Assuming that refire gives you a combined number of samples that exceed eight, add the squares of the two machine SDs from the two samples and take the square root of that sum. That will give you the machine SD for the combined shots. If you do the same with the SD's arrived at by Denton's method, at that stage the results should be much less different.

To get sigma (population SD) estimate:

Sample Size    Divide ES by
     2            1.128
     3            1.693
     4            2.059
     5            2.326
     6            2.534
     7            2.704

[ninosdemente]

Thank you guys for the help. I guess then in this case, for me it would do me no good as I have no method of measuring velocity.

[Bart B.]

A friend tested primers shooting BBs from an air rifle barrel adapted to a Remington 700 action chambered for the 17 Rem. Primers producing lowest average velocity also had the lowest spread. They shot the most accurate test groups with 308 Win chambered match rifles.

[Rimfire5]

I have another approach to comparing primers.

I shoot the same powder with each primer at the same exit time (B_Time ms on QuickLOAD load sheets).

I shoot a variety of bullets and powders and shoot enough groups to get a good statistical base.

When you compare results with enough data, you can analyze by bullet, by powder, etc.
I was surprised how much difference there were in overall averages by primer.

With a Savage 12 FV .223, I tested CCI BR-4 and Remington 7 1/2 BR primers with 69 grain Sierra SMKs and TMKs and 77 grain Sierra SMKs and TMKs.
For 617 groups overall average the difference was 3.2% in favor of the Rem 7 1/2 BRs.
The Std. Dev. of the groups from both primers was essentially identical.
For 69 grain bullets, the difference was 9.4% in favor of the Rem 7 1/2 BR but the Std. Dev. was 7.8% greater for the Rem 7 1/2 BRs.
For 77 grain bullets, the difference was 2.5% in favor of the Rem 7 1/2 BR but the Std. Dev. for the groups was 4.55 larger for the Rem 7 1/2 BRs.
The group size Std. Dev. being larger indicates that the groups has a larger variation, but the accuracy was actually better. That could be explained by some of the smallest group sizes with the CCI BR-4 SRPs might have been larger than the Rem 7 1/2 BRs but the largest group sizes were about the same.

I did the same type of test with a Savage 12 LRP in 6.5mm Creedmoor, but I tested CCI BR-4, CCI 400, Federal 205M and Federal 210M. The 210M large rifle primers were tested in Norma brass and the small rifle primers were tested in Lapua brass.
The test included 130 to 147 grain bullets across 10 types.
The CCI BR-4 SRP primers had the best overall average.
The CCI 400 SRP primers averaged 10.3% larger groups with a 9.9% larger Std. Dev. for the CCI400s
The Federal 210M primers averaged 16.8 larger groups with a 45.5% larger Std. Dev. for the Fed 201Ms
The Federal 205M SRP primers averaged 46.9% larger groups with a 74.0% larger Std. Dev. for the Fed 205Ms.

For me, accuracy is the end game and consistency of the group sizes is a great indicator. The consistently lower Std. Dev. is a great indicator of the best result.

[Unclenick]

Were you re-tuning the loads for minimum group size with each primer?

[ninosdemente]

Rimfire5, thank you for your reply and for your results. Thanks Bart for your reply as well.

[rc]

I was playing with small rifle primers a few years back and tried Federal, CCI and Winchester. Winchester produced consistently smaller groups. I haven't had a chance to try a newer batch of Remington Bench Rest primers I picked up.

[Rimfire5]

Unclenick,

With the 12 FV 6.5mm Creedmoor, I shot a lot of groups with each primer until I got enough data to make a reasonable conclusion.
I tried to keep the loads at the same exit time for each load, and picked the exit time that gave the best results.
With temperature and other variations, I managed to keep the loads within 0.005 msec. exit time across the tests.
Two of the primers showed a very great difference in accuracy and two were clearly outliers.

Then I took the two best performers (with less than 10% difference in accuracy) and concentrated on them and tried to see if I could identify the overall best primers. I did a bit of adjusting for both to see if I could determine anything about preferences.

The results stayed in the same ballpark even during the larger samples so I concluded that the BR-4 primers did indeed perform best.
I now use BR-4 primers for that caliber.

With the .223, I started with the BR-4s and got good results. I found out from two posters on another site that they had gotten good results with Remington 7 1/2 BRs. I had lots of data with the CCI BR-4s so I shot the same loads with Remingtons. The difference in the primers was much less obvious and I tried different bullet weights to see if that would make a difference. As reported, there was a difference but I suspected that 'shooter induced variations' may have contributed. The overall difference was small and the group averages were also very small, under 0.3 inches at 100 yards for both. For these primers it is hard to make a strong case between them.

I now use Remington 7 1/2 BR primers for the 12 V .223 and BR-4 primers for the 12 FV 6.5mm Creedmoor, probably because I have over 5000 of each and want to use them equally.

[Unclenick]

Yes, I got the barrel time match, but wondered if you had tried varying that. Barrel time tends to keep you optimal, but if there is a difference in gas bypass time due to a difference in how fast pressure builds, it could shift the optimum barrel time a little. Probably not a lot. I was just curious if you had tried that experiment. But even without it, this is still good and very interesting information and I am glad you shared it.

[Rimfire5]

Now I think I understand your question and it is a good one.
Before I started to test primers I tried lots increments around the projected exit time for each barrel to verify that the expectation was valid.
Also, there are going to be variations in velocity in any reloading process so that is also monitored to see if the conditions remain consistent.
Out of a lot of loads, not every one hit the expected velocity when measured. I adjusted the 'real' exit time calculation so I could account for the variation when comparing results.

I experimented when I first got my three 6.5mm Creedmoors and also with three my .223s and found that they all shoot best when within 0.010 msec. of the reflection at the chamber.
It didn't seem to matter what the bullet is as long as the projected velocity and exit time for the powder-bullet combination is in the desired range. That is what I load for.
I didn't find much of a muzzle velocity difference between the best primers for either caliber.

I only have one rifle with a muzzle brake (a .308) that has its best accuracy off the chamber reflection by more than 0.010 msec.
I suspect that the the type of steel in the muzzle brake is different than what I thought it was.
Of course, there is a possibility that the batch of steel in the barrel had either a bit more or a bit less carbon than expected. Either or both of those causes would change the reflection speed of the barrel and and would adjust the desired exit time calculation.
There is also a remote possibility that I measured the barrel or muzzle brake wrong, but all of my other rifles must have been measured correctly, so I would think I probably measured this on correctly also.

[Unclenick]

Could also be a small difference in grain orientation. That affects speed of sound in steel.