Jim Kauber
Alpha Munitions CSO
alphamunitions.com
President / Director of Training
The Site Firearms Training Center
thesitetraining.com
If you hear it and repeat it enough it has to be true! Just ask me and my internet-based opinion will verify it! Such is the ongoing discussion that theorizes the significant benefits in accuracy, ignition consistency, single digit standard deviations (SD) low extreme spreads (ES) and extended case life of the small rifle primer (SRP) brass over large (LRP). When I see this on our social media sites I wonder if the individuals are parroting the aforementioned or have actually done their own head to head SRP/LRP comparisons, collected the data and summarized the observed differences in an unbiased, comprehensive format. If they have, I think all the rest of us would be interested in seeing the results.
One of the great benefits of being a member of this fantastic Alpha Munitions Team is having the time, resources and support to implement our own evaluation processes to any number of given subject matter, which brings us back to the SRP/LRP data comparison or lack thereof. Since this seems to be a predominant subject to many in the precision rifle disciplines especially those of us that reload, we thought it beneficial to conduct our own testing with our own ultra-premium brass offered in both large and small primers. That being said though, let me state that these tests were not conducted in a controlled laboratory setting but rather in the cold, damp environment of the Pacific Northwest winter where Density Altitude spanned – 1061’ to +360’ and temperatures ranged from 29° to 51° F. Also, rest assured velocities were not cherry picked in order to show better data. On a couple occasions with both LRP and SRP I’d see a single spike or drop in a velocity outside the norm. These stayed, as this is reality; unexplained, but reality nonetheless.
Here’s the testing equipment used:
Rifles:
260 Remington – built by Benchmark Barrels http://www.benchmark-barrels.com
- Remington 700 short action
- 26” Sendero contour 1:8 twist 5 groove barrel w/Benchmark Miller Brake™ – Medium
- Bedded in a HS Precision PST 25 stock
- Nightforce 5-25 ATACR, MOAR reticle in Vortex Precision Matched Rings
- Jewell trigger
6.5 Creedmoor – built by Benchmark Barrels
- GA Precision Tempest action
- 24” Sendero contour 1:8 twist 5 groove barrel w/Benchmark Tactical Brake™ – Std W/Pinch Bolt
- Bedded in an Accuracy International AX stock
- Nightforce NXS 5.5-22X56, MOAR reticle in NF Ultralite rings
- Jewell trigger
6 Creedmoor – built by Benchmark Barrels
- GA Precision Tempest action
- 24” MTU contour 1:7.75 twist 5 groove barrel w/Benchmark Tactical Brake™ – Std W/Pinch Bolt
- Bedded in an Accuracy International AX stock
- Nightforce 5-25 ATACR, MOAR reticle in a Spuhr SP4603B, 20 MOA ring mount
- Jewell trigger
Reloading Equipment:
- Forster Co-Ax press
- Forster FL sizer die w/Ultra Micrometer Seater die
- RCBS Chargemaster 1500 w/McDonald’s straw modification to minimize overthrows.
- Forster Co-Ax Primer Seater
- Lee Decapping die
- Lyman Case Prep Xpress
- Wilson Case Trimmer
- Hornady Lock-N-Load Overall Length Gauge
- Sinclair Concentricity Gauge w/Clockwise Tools Electronic Dial Indicator
- Forster Co-Ax Case and Cartridge Inspector
- Forster Datum Dial
- Forster High Pressure Case Sizing Lube
- Sinclair small primer pocket uniformer
- K&M large primer pocket uniformer
- Thumler’s Tumbler Ultra-Vibe 10 w/untreated corncob media
- HFS Minus Pin Gauge set
Chronograph: MagnetoSpeed V3
- In addition to the 10 test rounds of each caliber and primer size, I loaded an additional 10 to shoot without the MagnetoSpeed attached. What I found was the MagnetoSpeed shifted the point of impact generally high left .5 – 1.25 MOA but did not affect group size.
Reloading Data:
260 Remington
- Alpha Munitions LRP / SRP trimmed to 2.025 at each firing
- Primers: CCI BR 2 Large Rifle, CCI 450 Small Rifle Magnum & CCI *BR 4 Small Rifle Match
- Powder: Hodgdon H4350 @ 43.0 gr
- Bullet: 142 Sierra Matchking seated .025 off rifling, Case Base to Ogive, CBTO 2.234
*In addition to CCI 450 small rifle magnum primers, the 260 test included CCI BR-4 small rifle match primers but misfires were occurring at a rate of ≈8% primarily during the 1st firing. Though you’ll see the results of using the BR-4 primers in the Table 4 graph, I dropped these in the 6.5 and 6 Creedmoor tests. I wouldn’t recommend using standard or match small rifle primers with these calibers.
6.5 Creedmoor
- Alpha Munitions LRP / SRP trimmed to 1.912 at each firing
- Primers: Federal 210M Large Rifle Match, CCI 450 Small Rifle Magnum
- Powder: Hodgdon H4350 @ 41.5 gr
- Bullet: 139 Lapua Scenar seated .020 off rifling, Case Base to Ogive, CBTO 2.210
6 Creedmoor
- Alpha Munitions LRP / SRP trimmed to 1.912 at each firing
- Primers: Federal 210M Large Rifle Match, CCI 450 Small Rifle Magnum
- *Powder: Alliant RL-16 @ 40.5 gr., first 2 strings, 40.2 gr., third string, 39.8 gr., fourth string.
- Bullet: 110 Sierra Matchking seated .010 off rifling, Case Base to Ogive, CBTO 2.155
* While shooting the LRP/SRP version of our 6 Creedmoor I was experiencing VERY high spikes in pressure evident by blown primers and hard bolt lifts even when the velocities remained close to the same. With each string these pressures increased to the point I was dropping .3 – .4 grains of RL 16 to compensate but the pressures just kept building. After calling Ron Sinnema, owner, CEO of Benchmark Barrels, and an endless resource of technical information, his single question was; “Have you been staying ahead of the carbon ring build-up in the barrel?” Well, no but I have been cleaning on a regular basis was my response. Just let me say that after I removed the hardened carbon ring according to Ron’s procedure, that SRP RL-16 load of 39.8 grains dropped from an average velocity of 3058 fps, SD 7, ES 23 to an average of 2960 fps, SD 4 and ES 15.
I’m going to drop the carbon build-up issue for now because this gives me another noteworthy subject to address in the very near future.
Loading and Firing Procedures
10 cases of 260, 6.5 CM, 6 CM, LRP and SRP were randomly selected from batches of 100 each caliber, primer size sent from our Ogden, UT factory. All 10 cases for each caliber weighed within 1 grain. Each was prepped and loaded exactly the same with the same lot number of components to ensure loaded ammunition consistency. The loaded ammunition was then shot and chronographed in five, 10 shot strings per caliber, primer type for a total of 300 firings; 150 LRP, 150 SRP.
Fired cases were prepped the same way:
- Cases cleaned
- De-primed
- Full length re-sized
- Shoulder bumped back .002 from fired dimensions
- .002 neck tension
- Trimmed to length
- Case mouth chamfered and de-burred
- Powder thrown to .1 grain
- Bullets seated to consistent, specified depth
- Rifles were cleaned between each 10 round string, let sit for 15 minutes to cool barrels between each string then 2 fouling shots were fired prior to chronographing.
260 Remington Data
Figure 1: Velocity Comparison of 260 Remington LRP and SRP looking at the average velocity of each shot string and the corresponding statistical data.
6.5 Creedmoor Data
Figure 2: Velocity Comparison of 6.5 Creedmoor LRP and SRP looking at the average velocity of each shot string and the corresponding statistical data.
6 Creedmoor Data
Figure 3: Velocity Comparison of 6 Creedmoor LRP and SRP looking at the average velocity of each shot string and the corresponding statistical data.
Observations, personal opinion and what you didn’t see:
Looking at the performance data for these calibers, the 260 SRP clearly had the lowest SDs and ESs. The 6.5 Creedmoor LRP had lower SDs and ESs in 3 of 5 firings and the 6 Creedmoor SDs were essentially the same though the LRP exhibited slightly lower ESs. So, at least in our 300 shot LRP/SRP comparison test, there wasn’t the monumental SRP performance advantage over the LRP like anticipated, actually just the opposite occurred. The differences for the most part were insignificant when it comes to range performance. A few consistent observations during these tests though:
The large primer, given all else is exactly the same, produces higher velocities.
In every fired string, the small primer groups were slightly smaller than the large.
If the SRP is fired in a firearm using the large, .078 firing pin and large firing pin hole, you will experience cratered or pierced primer cups at higher pressures/velocities.
What you didn’t see, though I suspect some would like solid information, was a case longevity test. I’ve done this before, as have several of our top ranked competition friends including those at Team Area 419 with everyone coming to the same conclusion; when pushed to maximum velocities and pressures, the SRP will out live the LRP before the large primer pockets expand to a point where they will no longer hold the primer. At no point during any of the testing I’ve done to date did the small primer pockets expand greater than .173, a dimension that will still adequately hold the primer in place. The same can’t be said of the large primer brass. What are these case life numbers? The loading component lot differences, barrel, chamber differences combined with the public’s reloading expertise are unknowns that are just too varied to come up with solid numbers. The only aspects we can control are our brass dimensions and quality. The rest is up to you.
In conclusion, should you wait on or switch from LRP to SRP? Only you can determine that answer. Each of us has our reasons to stay or switch. If you’re like me, and I suspect a lot of you are, and were able to score on a case of Federal 210Ms for example, I’m staying. If you’re on the fence and want to make a change to SRP, then there’s absolutely no down side to doing so. When you look at 30, ten shot strings, 29 were all single digit SDs regardless of large or small primers used and all groups were sub ¾ MOA.
Stay safe.
Awesome article guys, From the results, SRPs produce smaller groups in all three rifles…. is this a significant stat or is the difference negligible?
I found the accuracy difference insignificant between the LRP and SRP loads. Well, insignificant when shooting long range in field conditions anyway. The extreme difference was with the 260 at .25 MOA, the 6.5CM .12 MOA and the 6 CM .13 MOA. Bear in mind these were 10 shot groups and most shooters I know cannot hold to those tolerances at long range (including myself). To put this in perspective, .13 MOA at a thousand is 1.3″. Great question and I’m sure others would ask the same. – Jim Kauber
Could the smaller group size with SRP be due to lower v0 hence less recoil?
Theoretically it makes perfect sense.- Jim Kauber
That should not make a difference. the length of time that the bullet is in the barrel and could be effected by movement is not long enough to be effected by the slight recoil difference based on speed. the bullet is long gone before those movement effects are taking place. So assuming that the same stable position is used the added velocity and recoil wouldn’t have any effect on group size.
Great article!
What difference would Magnum primers make?
In South Africa, our sole powder manufacturer (Somchem), provides load data, but only with CCI 250 primers for 6.5 Creedmoor. Which is strange to me?
I’ve compared results between CCI 200 vs CCI 250, using Norma brass, Lapua Scenar 139gr bullets and 41gr S365. Howa heavy barrel bed in a Boyds Atone stock.
Velocity was much more consistent using CCI 250, but accuracy was terrible (~2MOA) compared to that achieved with CCI 200 (Sub MOA).
Have you done similar tests? Is there any merrit in using Magnum primers for 6.5 Creedmoor?
“I have not done a large standard/magnum primer comparison test on the 6.5 Creedmoor for the simple reason the case capacity does not warrant such a test. I see no merit in using a large magnum primer in charges less than 70 grains unless the specific powder is hard to light..like ball powder.” -Jim Kauber
Do you think the results would change if the flash hole were .060 instead of .080 on the small rifle primer?
George,
Another good question. Yes, there certainly is a difference. Again, last year we ran our own head to head test with Lapua 6.5 SRP brass which, as you no doubt know has a .059 flash hole. What we found is that at below freezing temperatures the .080 diameter flash hole brass produced more consistent powder ignition with lower SD and ESs. Above 40 degrees though, no difference; sometimes Alpha performed better and other times Lapua performed better, all very close though. We did not make the decision to go with the .080 flash hole lightly but rather took into consideration the overall performance factor across the temperature span. – Jim Kauber
In regards to small vs large flash holes.. I have some 6.5 x 47 Lapua brass some of the brass before I knew better I punched out the primers with large pin… hence they are now large flash holes. Do you think there would be much of a difference in using them with the exact same load and recipe except for the flash hole size??? Affect of accuracy, velocity or just maybe more temperature sensitive as your above response noted?
Thanks great article and insight!
This response citing a test against lapua is a credit to you. You made a comparison, explained a data driven engineering decision, and didn’t disparage your competition. I applaud you sir. Gentlemanly respect of your competition makes you and your company better, and certainly earned my respect.
Jim,
Great article. Good data is always hard to argue with. One more thing that was touched upon in your article is the Large firing pin vs Small firing pin. For those trying to decide between LRP and SRP that have a Large firing pin, I would recommend the LRP brass. Your potential for problems will be much less, even though you may get a few less firing. Blowing primers can damage your bolt, firing pin, or firing pin hole is much worse of a problem.
Excellent article! I have Alpha LRP I use in my .260 bolt and gasser, and just received my Alpha SRP. I appreciate the reloading, loading and firing details and am looking forward to your article on the carbon ring.
Great field work. Alpha is all I’m using anymore. I haven’t used the source yet due to getting 13es/6.8sd with a .08” group from my 260 rem tikka/143eld-x loads. I will be using srp on my 6.5 cm loads though
Jim,
Interesting information. As an aside, if you want to compare ancient primers to new ones let me know. I have a carton or so of 210M primers that are about 20 years old.
The delta-V seems to be more than can be explained by LRP increased primer pressure alone. Since the V was lower with the SRP, that suggests that not all the powder is being burned, or the burn rate has changed slightly. So how do we explain the lower SD with the SRP?
(FWIW, your results mirror my own tests using LRP and SRP 6mm PPC brass exactly.)
Brilliant experiment and article, Jim. Well presented and authoratative.
My interest is in the .260Rem results…
Given that the avg group size for the SRP is almost 40% smaller (significant) than the LRP, and yet the velocity difference is within a very few fps (>1%), what thoughts do you have on why there is this significant difference in group size, particularly in regard to the other cases?
My own feelings are that the case capacity or case shape may be an influencing factor. What do you think?
To your knowledge, has anyone used Alpha brass of both LRP & SRP in a .260 Rem Ackley Improved to at least investigate the case SHAPE aspect? (I plan to put a .260Rem AI barrel on my Accuracy International AT, as I believe that this will be the ultimate medium capacity, short action 6.5mm cartridge…)
Thank you.
Incidentally, I had planned to purchase some of your SRP .260 Rem brass anyway, which was why I was on your site, this article/experiment just confirms my purchase…
Neil, I haven’t an extensive quantifiable answer to your question regarding why the SRP produced noticeably smaller groups in the 260 other than ignition consistency which was the intent of the experiment. As you noticed, the accuracy difference was more pronounced with the 20°shoulder case when compared to the Creedmoor’s 30°. I concur with your theory of case shape being the most influencing factor when it comes to accuracy but it would be interesting to see the results of a LRP/SRP comparison with regards to case capacity in a 260 Ackley Improved. I think you just helped me make up my mind on what I should re-barrel my 308 in.- Jim
Has there been any thought about running a series of statistical tests (i.e. Z or t) to determine if the different scenario yield “significant” differences in group size?
Try the small rifle primers on a cold day. And by cold I don’t mean gotta wear a sweatshirt to the range.
Really great article, and I appreciate the time you took to put it together. I had never heard of the carbon ring until this article. This actually explains some issues I saw at the range this past weekend. I had a similar issue, noticed much more recoil than normal and aberrant shots. I recalled I didn’t clean my rifle from the previous range trip and I think this may have been the culprit as well. I am sure I will be lambasted for not cleaning it, so I will explain. I had a ton of personal issues come up and well those took precedence. Great write up Mr. Kauber! I am going to buy a 100 Alpha and see how they do against Lapua and Peterson cases.
-Phil
Could someone explain a good way to determine if you have a carbon ring and how to go about removing it?
Thank you for the great comparison between the lrp and s&p. I was curious if the point of impact changed with all things being equal except primers.
To be perfectly honest, I didn’t pay too much attention to shift in impact between LRP and SRP as I was evaluating velocity, Standard Deviation, Extreme Spreads and group sizes. When you have the velocity differences seen between the primers though, point of impact will change due primarily to barrel vibration and muzzle position as the bullet is released from the barrel.