Small vs Large primers: Gospel or Koolaid?

[Tommie]

In years past I've read two articles written by very respected columnists/gunsmiths regarding this question. In both articles (22 BR and 6mm Wasp) the test involved using identically prepped brass of both primer configurations. In both accounts the verdict was that primer size made no measurable difference in accuracy.

We're all familiar with the discussion points. And I have to agree that the PPC case's small primer and tiny flash hole seem to be a "magic" combo.

So, is the accuracy superiority (at least in short-range bench rest cartridges) scientific fact, a theory or voodoo?

 

[Dusty Stevens]

Each cartridge has its own characteristics. Some need large magnum primers while others simply need small rifles. Its all in the efficiency of each case design

 

[spclark]

Scientific fact is asking a lot, considering what that kind of documentation would require before anyone would accept it.

I know in my experience shooting both 308 for Palma (with 155 grain bullets) and 6XC (105VLD) at 600 and 1,000 yards (sling & irons, not F-Class just yet thanks) I'm more confident using small rifle primers than large.

When I'd used LR exclusively my scores were't as consistent as they are now. Making allowances for my skills improving over time I believe using small primers contributes to more consistent performance... I just can't prove it.

I can prove my brass lasts longer though.

 

[ShootDots]

Scientific fact is asking a lot, considering what that kind of documentation would require before anyone would accept it.

I know in my experience shooting both 308 for Palma (with 155 grain bullets) and 6XC (105VLD) at 600 and 1,000 yards (sling & irons, not F-Class just yet thanks) I'm more confident using small rifle primers than large.

When I'd used LR exclusively my scores were't as consistent as they are now. Making allowances for my skills improving over time I believe using small primers contributes to more consistent performance... I just can't prove it.

I can prove my brass lasts longer though.

The statement above "I can prove my brass lasts longer though", is the reason, I believe, MOST people who opt for a S/R primer over a L/R primer do so... The primer pockets can withstand more pressure than the L/R primer brass. Whether or not it produces smaller groups or tighter "e.s.'s" may or may not be valid. Each rifle, and what it likes will be the determining factor in that.. Personally, I wish that EVERY cartridge made that is of a .308 case or smaller, used S/R primers!

 

[Keith Glasscock]

Interesting question. I'd add that some things are conditions / atmospherics dependent.

I know that my Dasher doesn't like really cold weather (below 25F) It still shoots, but I can't get it to "like" the load as well regardless of charge variations.

I know that my LP 308 brass doesn't care. Groups look the same at all temperatures (after charge adjustments).

I think the real test would be to load up some of each primer size in 308 and have a little test at various temperatures to see if it is primer dependent or not. It would require developing two distinct loads, one for each type of primer and then either chronographing or, more ideally, shooting them at 600+ yards.

 

[Changeling]

Interesting question. I'd add that some things are conditions / atmospherics dependent.

I know that my Dasher doesn't like really cold weather (below 25F) It still shoots, but I can't get it to "like" the load as well regardless of charge variations.

I know that my LP 308 brass doesn't care. Groups look the same at all temperatures (after charge adjustments).

I think the real test would be to load up some of each primer size in 308 and have a little test at various temperatures to see if it is primer dependent or not. It would require developing two distinct loads, one for each type of primer and then either chronographing or, more ideally, shooting them at 600+ yards.

Excellent suggestion, I've been wondering (never asked though) if the SR primers had problems say down to "0" degrees are so. in 243 size cases and smaller.
I have heard of problems problems but nothing I would consider concrete evidence.

 

[Keith Glasscock]

I don't have any evidence as to *why* I've had problems at low temps with the Dasher. I just know that I haven't had any luck.

 

[Damfino]

I can't tell the difference in any quantifiable measurement, such as, group size, extreme spread, match scores, etc., at 100 or 1000 yards, but as discussed above brass life makes the Palma primer Lapua .308 brass more attractive. Especially given the expense and the labor intensive nature of brass prep.

 

[Laurie]

SR primers in Lapua 'Palma' brass do reduce .308 Win velocity spreads compared to equivalent loads in standard LR primer Lapua brass. That has been proven many times, the ES reduction being around a third. That may not make the cartridge more 'accurate', but it should reduce elevations at long ranges. The reason why it's called the 'Palma' case is because it was developed at the request of the US Palma teams, the standard Palma 308 loading of a 155gn Sierra 'Palma' MK at around 2,975-3,000 being somewhat ballistically stretched at the longest stage distance of 1,000 yards.

MVs are usually reduced in the 'Palma' case, 15-35 fps all other things being equal so most charges need to increased by around 0.5gn to get back to the same level.

My own testing with 308 is that some extruded powders suffer problems with ambient temperatures below around 4 or 5-deg C (ie in the 30s F). Viht N140 gave larger spreads and groups in the Palma brass with the CCI-BR4 than with standard brass with the Federal 210M. With a rerun in the spring with the temperature in the 50s, the results were reversed with the Palma case the clear 'winner'. Viht N150 though was apparently unaffected on the same winter's day that the N140 combination was fired.

Testing Hodgdon CFE223 a few weeks ago with temperatures in the 40s, two different sets of loads (two different bullets / weights) gave poor groups, large ES values and a number of slight 'hangfires' with the Palma case, while there had been no problems a week earlier with standard brass and LR primers in slightly colder temperatures. One cartridge (ex 25) in each load combination was a complete misfire. Pulling the bullet afterwards showed both primers had fired OK, simply failed to ignite the powder.

With smaller cases and powder charges - the BRs, Dasher, 6.5X47L, PPCs - this may be less of an issue. The traditional rationale for small primers + smaller diameter flash-holes is that the LR primer is overly powerful for the most consistent performance with 28-35gn power charges. It has been proven on many occasions that BR performance deteriorates if the flash-hole is opened up from its 1.5mm diameter to the more usual 2mm, not just in ES / SD, but also in achiveable group sizes.

 

[riflewoman]

Dennis Flaherty, the Palma Shooter, once was talking about primers and he couldn't say with any certainty that primer size or brand was provably better to make Long Range 308 ammunition. At one point he even made up a test barrel that was chambered in 308 but had a .177 bore he shot BBs thru over a chronograph trying to find the most consistent primers. He would then try them in his 308 at 600 but couldn't find a correlation.

In my own testing SR primers in 308 cases I have determined the there are too many variables to say with certainty that SR primers will shoot better in 308 sized cases.

 

[spclark]

Good stuff here.

I'll add that I've learned from a reliable source that Wolf expects to continue importing Russian-sourced primers. This comes from a Wolf rep at SHOT last week.

A quick check on GUNBOT shows three popular vendors stocking large and small in both rifle and pistol products (some magnum) right now. Some are Wolf, others Tula.

 

[MattPeetz]

Would small rifle primers work with a slow powder like IMR7977 in the 51gr and lower range?

 

[spclark]

What cartridge & bullet?

I use SR in Palma brass w/155's but nothing gets fired unless it's above 50 degrees. Charge weights around 44-46 grains & by some standards fast powders.

 

[MattPeetz]

For a remington 260 but specifically 260 ackley. I have good success with slower powders as i run longer barrels and in my ackley i am running a heavier bullet. I've just wondered about using the palma brass. It would be for my comp gun and 50 degrees is probably the lowest i will see.

 

[STS]

A very interesting discussion so far. I have a passion for coyote calling and as such I have seen a fair amount of cold weather. At -20 degrees I have the sense that my .22x47 Lapua did not want to go off. They don't do a classic hang fire but there was a noticeable delay in the shot. Those of course are small rifle primers.

 

[riflewoman]

What has been found is that with 308 size cases, using powders slower than 4064 AND primers that are less hot than the Rem 71/2 poor ignition characteristics are observed.

 

[Berger.Fan222]

Testing Hodgdon CFE223 a few weeks ago with temperatures in the 40s, two different sets of loads (two different bullets / weights) gave poor groups, large ES values and a number of slight 'hangfires' with the Palma case, while there had been no problems a week earlier with standard brass and LR primers in slightly colder temperatures. One cartridge (ex 25) in each load combination was a complete misfire. Pulling the bullet afterwards showed both primers had fired OK, simply failed to ignite the powder.

We've seen more failures and hangfires (< 1 sec) with ball powders also. Never a problem with Varget and H4895.

 

[Laurie]

For a remington 260 but specifically 260 ackley. I have good success with slower powders as i run longer barrels and in my ackley i am running a heavier bullet. I've just wondered about using the palma brass. It would be for my comp gun and 50 degrees is probably the lowest i will see.

This is becoming a common practice in some places. 'Down Under' (New Zealand as well as Australian) shooters have long reformed .308 Win 'Palma' cases into 260 Rem and other 308 based models. It's the known case-head strength and its ability to repeatedly take high pressures as well as precision that attracts. If you search around on this forum, you'll find some posts on this. There are also some interesting reports on performance with hot 6.5mm Hornady Creedmoor loads using reformed 'Palma' cases vice the standard Hornady product. That's a bit more advanced re-forming though than a simple neck 308 down to 7mm-08 and 260 Rem followed by a neck-turn. I've got a box I've reformed for a 7mm-08 F-Class rifle. It's too early though to say how it's working out. This will ultimately be used with case-full loads of relatively slow burning powders such as Viht N165 with heavier bullets.

 

[Laurie]

A very interesting discussion so far. I have a passion for coyote calling and as such I have seen a fair amount of cold weather. At -20 degrees I have the sense that my .22x47 Lapua did not want to go off. They don't do a classic hang fire but there was a noticeable delay in the shot. Those of course are small rifle primers.

I'd think that at these sorts of temperatures the 6.5X47's use of small primers risks severely compromising cartridge performance. if nothing else, a chronograph comparison with warm weather performance would likely throw up some interesting differences. The X47 must be on the limit for powder charge size in very cold conditions. Lapua didn't develop this cartridge as an all-round sporting rifle number for use in any conditions. Its original rationale was to knock the 6mm BR Norma off its cartridge-to-use position in European ISSF 3-position 300 metre competition. In Europe (the UK aside) this is the premier fullbore competition discipline with big bucks involved and a lot of PR and marketing benefits to the manufacturers of the winners' rifles and ammunition. Lapua sponsors many of the top shooters, but really, really wants to have the winners' default cartridge bearing its name instead of Norma. As it happend the X47 has not been successful in ousting the BR in this role, but been adopted for lots of others including 'hunting' which may or may not have been intended by Lapua. Certainly, when sample prototype 6.5X47 Lapua brass was handed around at SHOT back in whenever, and was reported on in the Accurate Shooter Daily Bulletin, it was large primer equipped. between that point and introduction of the production version, the company took the decision to change to the small primer form.

 

[dkhunt14]

A very interesting discussion so far. I have a passion for coyote calling and as such I have seen a fair amount of cold weather. At -20 degrees I have the sense that my .22x47 Lapua did not want to go off. They don't do a classic hang fire but there was a noticeable delay in the shot. Those of course are small rifle primers.

I would think at -20 a lot of cartridges would show poorer performance. Not just small rifle primers. Some would be more noticeable then others. Matt