Skip to main content

Small Rifle Primers vs. Large Rifle Primers

A close look at using small rifle primers rather than large rifle primers in reloading cartridge cases where both are offered; testing shows size matters little, with a few exceptions

Small Rifle Primers vs. Large Rifle Primers
Small Rifle primers leave case heads stronger, and brass lasts longer. Large Rifle primers ignite propellant more reliably and consistently in extremely cold temperatures.

When Lapua began offering 6.5 Creedmoor brass, and interestingly, it introduced its brass with Small Primer pockets—to the acclaim of precision competitive shooters and to the dismay of traditional propellant companies. Starline and Alpha Munitions also now offer 6.5 Creedmoor brass formed with Small Rifle primer pockets.

Advantages of using a Small Rifle primer rather than the typical Large Rifle version are twofold. Use of the smaller, less aggressive cap can result in better consistency, particularly in the form of tighter standard deviations. While this matters little inside common hunting distances, it’s a big deal to shooters reaching past a half-mile, where a mere 20-fps difference between shots can equate to inches of vertical impact difference on the target.

Additionally, a small primer pocket leaves more material intact than a large primer pocket. The case head is left stronger and less susceptible to pressure-caused deformation. Handloaders searching for the last iota of long-range performance can push bullets faster—using aggressive charges on the cusp of safe pressure limits—without loosening primer pockets.

As a result, savvy competitors with long-barreled match rifles can achieve muzzle velocities a solid 100 to 200 fps faster than typical factory-ammo speeds with a given bullet. Only experienced handloaders should attempt this. Always start low, work up slowly and carefully until you see early pressure signs, and then back off a bit.


Master riflesmith and PRS shooter Clayton Smith has pioneered a unique 7mm wildcat, the 7mm SAW, that showcases the advantages of the Small Rifle primer pocket. Formed from Lapua’s .308 Win. small-pocket Palma brass, it features an “improved” profile with a sharp shoulder angle and little body taper. Because the Small Rifle primer pocket enables the case head to maintain integrity while operating at chamber pressures in the upper spectrum, the little hotrod pushes 7mm bullets to unprecedented speeds for a short-action, standard-diameter cartridge.


The advantages of Small Rifle primer pockets in standard-size centerfire cartridges don’t come free. In an issue of RifleShooter’s sister magazine Shooting Times, handloading editor Lane Pearce addressed potential pressure issues related to the use of small pockets in standard-size cases, and he went so far as to advance some stark advice against using them except in specific circumstances. If you can hunt up a back issue, it’s worth a read.

When temperatures plummet, propellants become increasingly difficult to ignite evenly, particularly those made of a double-base compound containing nitroglycerine. There goes the added consistency you gained by using a Small Rifle primer. Stubborn ignition could theoretically go so far as to cause a slight hangfire in extreme cold.

It’s worth noting that one of my favorite 6.5 Creedmoor propellants, Hodgdon 4350, is single-based, while another, Alliant Reloder 17, is double-based. A quick call to the manufacturer will help determine whether your favorite propellant flavor is single- or double-based.

Rarely are long-range matches held in truly cold conditions. Most are scheduled during spring, summer and fall months, and temperatures range from balmy to scorching. Cold-induced reluctant ignition isn’t commonly an issue for competitors.


For hunters, however, opting to use standard-size rifle cases perforated with Small Rifle primer pockets is usually a poor decision, unless they live in mild climates and rarely hunt in temperatures below freezing. Using standard Large Rifle primers ensures reliable ignition in just about any temperature.

The second downside is obscure but presents a potential safety issue. As Pearce outlines, if the initial petite flash of a Small Rifle primer fails to instantly and fully ignite a charge, theoretically the primer could bump the projectile forward into the throat.

If the chamber throat is really rough, it could stick momentarily as the powder ignited and pressure built before breaking free and scooting down the bore. We’re talking nanoseconds but potentially enough to allow chamber pressure to spike.


However, if Lapua is confident selling standard-size cases made with Small Rifle primer pockets, I’m confident using them is safe in pretty much all conditions. Plus, some of the most savvy hand­loaders and shooters in the world—Palma competitors—regularly choose Small Rifle primer pockets in the .308, which has about seven percent greater propellant capacity than the 6.5 Creedmoor.

//content.osgnetworks.tv/rifleshooter/content/photos/SmallvsLargePrimers-1.jpg

To put on paper the accuracy and consistency differences—significant or not—between using Large and Small Rifle primers with both single- and double-based propellants, I handloaded several batches of 6.5 Creedmoor test loads with 142-grain Sierra MatchKing bullets. To eliminate as many variables as possible, I used Federal Gold Medal primers in both sizes. Cases primed with the Large Rifle version were weight-sorted, neck-turned Hornady; cases primed with Small Rifle caps were new, untouched Lapua brass.

My hope was accuracy levels would help me isolate and showcase differences between the handload types, but the results were so similar as to be inconclusive.

The two H4350 loads averaged 0.38 inch and 0.40 inch, with honors going to the Large Rifle primers. However the difference is well within my human margin of error, and those averages could just as easily swap were I to repeat the test. Standard deviations were exactly the same: five fps. The only difference was a 20-fps velocity increase with the Large Rifle primers.

To my surprise, results with the double-base Reloder 17 powder were twinlike also. Group average was within .01 inch. Standard deviation did favor the loads primed with Large Rifle caps but by the slimmest of margins—six versus seven fps. And this time, the Small Rifle primers turned in the higher muzzle velocity.

Based on this test, I have to conclude that as long as you use consistent, well-prepped brass, primer size matters little. Large Rifle versions will be more reliable in extreme cold. Small Rifle pockets will stay snug a bit longer if loaded hot. Aside from those two simple caveats, either will serve yeoman’s duty.

GET THE NEWSLETTER Join the List and Never Miss a Thing.

Recommended Articles

See More Recommendations

Popular Videos

Hornady 6MM Creedmoor

Hornady 6MM Creedmoor

Tom Beckstrand and Neal Emery of Hornady highlight the 6MM Creedmoor ammo.

Ruger Launches New American Rifle Predator in 6.5 Grendel

Ruger Launches New American Rifle Predator in 6.5 Grendel

OSG's Lynn Burkhead and Ruger's Matt WIlson kick off SHOT Show 2018 by taking a look at the Ruger Predator.

Black Hills Evolution of Rifle Cartridge: .308 Win. 175 Gr. Match

Black Hills Evolution of Rifle Cartridge: .308 Win. 175 Gr. Match

David Fortier talks with Jeff Hoffman of Black Hills Ammunition about the evolution of the .308 Win. 175 Gr. Match bullet.

Steyr Arms Announces Sniper Rifle in 6.5mm Creedmoor

Steyr Arms Announces Sniper Rifle in 6.5mm Creedmoor

Scott O'Brien from Steyr Arms sat down with Michael Bane at SHOT Show 2018 to take a look at Steyr's new tactical heavy barrel sniper rifle in 6.5mm Creedmoor.

See More Popular Videos

Trending Articles

With the introduction of the .22LR chambering option, the Blaser R8 rifle is more versatile than ever. Blaser R8 .22LR Conversion Review Reviews

Blaser R8 .22LR Conversion Review

Layne Simpson - July 30, 2020

With the introduction of the .22LR chambering option, the Blaser R8 rifle is more versatile...

The Christensen Arms lightweight Mesa Titanium Edition bolt-action hunting rifle is a peak performer.Christensen Arms Mesa Titanium Edition Rifle Review Reviews

Christensen Arms Mesa Titanium Edition Rifle Review

Brad Fitzpatrick - August 14, 2020

The Christensen Arms lightweight Mesa Titanium Edition bolt-action hunting rifle is a peak...

A .22LR rimfire rifle is a must-own for any gun owner, and these six bolt-action rimfire rifles give shooters a variety of offerings to choose from.6 Great Rimfire Bolt-Action Rifles Rimfire

6 Great Rimfire Bolt-Action Rifles

Jeff John - July 22, 2020

A .22LR rimfire rifle is a must-own for any gun owner, and these six bolt-action rimfire...

SIG SAUER adds to its Elite Match ammo line with the 30-06 Springfield.New 30-06 Springfield Elite Match Ammo from SIG SAUER Ammo

New 30-06 Springfield Elite Match Ammo from SIG SAUER

Rifleshooter Online Editors - April 03, 2019

SIG SAUER adds to its Elite Match ammo line with the 30-06 Springfield.

See More Trending Articles

More Reloading

The handloading question: With large availability factory ammo on the market, why bother with reloading? Craig Boddington offers a few answers.Reloading Ammo – Why? Reloading

Reloading Ammo – Why?

Craig Boddington - March 26, 2019

The handloading question: With large availability factory ammo on the market, why bother with...

The 6.5 Creedmoor and 6mm Creedmoor ammo cartridges are capable of incredible accuracy, making them prime candidates for reloading6mm and 6.5 Creedmoor Precision Ammo Reloading Reloading

6mm and 6.5 Creedmoor Precision Ammo Reloading

Layne Simpson

The 6.5 Creedmoor and 6mm Creedmoor ammo cartridges are capable of incredible accuracy, making...

It's no secret that 6.5mm cartridges are the hot trend in big-game ammunition, so it shouldn't have been surprising when a Weatherby Magnum became the fastest 6.5 of all. Here's some 6.5-300 Weatherby Mag load data to get you started.6.5-300 Weatherby Mag Load Data Reloading

6.5-300 Weatherby Mag Load Data

John Barsness - August 19, 2019

It's no secret that 6.5mm cartridges are the hot trend in big-game ammunition, so it shouldn't...

New reloader powders from Alliant offer improved stability in a wide range of conditions.New Powder from Alliant with Improved Stability Reloading

New Powder from Alliant with Improved Stability

Joseph von Benedikt - January 11, 2019

New reloader powders from Alliant offer improved stability in a wide range of conditions.

See More Reloading

Magazine Cover

GET THE MAGAZINE Subscribe & Save

Digital Now Included!

SUBSCRIBE NOW

Give a Gift   |   Subscriber Services

PREVIEW THIS MONTH'S ISSUE Arrow

Buy Digital Single Issues

Don't miss an issue.
Buy single digital issue for your phone or tablet.

Buy Single Digital Issue on the RifleShooter App

Other Magazines

Special Interest Magazines

See All Special Interest Magazines

GET THE NEWSLETTER Join the List and Never Miss a Thing.

Phone Icon

Get Digital Access.

All RifleShooter subscribers now have digital access to their magazine content. This means you have the option to read your magazine on most popular phones and tablets.

To get started, click the link below to visit mymagnow.com and learn how to access your digital magazine.

Get Digital Access

Not a Subscriber?
Subscribe Now