6mm Creedmoor Small rifle primer

[Ironworker]

What is the purpose of a small rifle primer option in a 6mm Creedmoor ?

 

[Tommie]

This will be interesting.

 

[mike a]

Makes less noise with a silencer? Or primer pockets last longer with hot loads. That’s my two guesses.

 

[lb-ft]

Only advantage I’ve personally experienced is extended brass life with no loss of ignition quality or precision.

RL19 in Alpha SRP shooting Nosler 105s with CCI 450s.

Factory Ruger. Results are very satisfactory. As in I haven’t wanted to try any other loads, no need to.

Small sample size, take it for what it is.

 

[Laurie]

Small primer brass in larger cartridges (> capacity than that of 6.5X47mm Lapua) has two origins.

The first is that Remington produced very thin-wall SP / small flash-hole 308 Win brass in the dawn of its BR cartridges back in the 1970s/80s. That was because although SAAMI registered, Remington didn't intend making any factory brass or ammo initially. BR adopters bought this special 308 Win brass and used forming die sets / trimmers to make their own. It was variously called 308 Win 'Competition' or 'UBBR' (Unformed Basic Bench Rest). There is still a considerable number of these cases in circulation.

Many people tried loading these 308 cases as supplied and results were mixed, but overall rated unsatisfactory. This was due to perceived ignition (insufficiently vigorous) issues in all but the most favourable combinations and environments. Some people reamed flash-holes out which at least partly solved the problems. So, the idea of SP versions of larger cased numbers (ie larger than the BR and 220 Russian / PPCs etc) pretty well died out for a generation.

Then secondly, around 15 years ago, the US Palma teams started looking at reviving the SP 308 Win with a view to reducing MV ES/SD values. This was driven by a team member whose name I forget who had produced excellent results with Remington UBBR based handloads. The team captains approached Lapua which made up a number of SP cases (easily done as they used the same case-head format as existing Lapua 6BR and 6.5X47mm designs) for team (and company) evaluation. Around the same time, (2004/5) Lapua was developing its 6.5X47mm, and primer / F-H dimensions raised a fundamental design question. Both forms were developed and after extensive trials, the SP / SF-H form was chosen. That raised viable SP powder charges to ~40gn levels from the BR's 30gn.

Meanwhile a full season of secret tests by selected US Palma team members took place in real-range conditions. The US team was then in the run-up to an international 4-yearly World or Palma championship fixture and these tests validated the concept. With the standard US Palma recipe of Lapua case, 155gn Sierra Palma MK and 44 or 45 point something grain charge of H. VarGet, there had been no ignition issues and ES values were reduced by a third. The reduced primer energy saw slightly reduced average MVs and charges were increased to return them to the previous LP brass levels, around 1gn more needed. This was then announced in the US Teams' Forum

http://www.usrifleteams.com/lrforum/

and that the team then being selected and trained up for the following year's fixture would use SP ammunition. It had been cleared with ICFRA and Lapua had adopted the SP brass as a production item and was about to put it on general sale so all competing nations' teams could follow the US example if they so wished. This was a VERY controversial move among American sling shooters and there were many and varied objections to its adoption on the teams' forum. Some questioned its 'legality' but most questioned the decision on the basis that it simply wouldn't work reliably enough given the 1980s' experiences.

The Palma shooters didn't increase pressures / MVs, their interest being entirely in reducing ESs and hence 'elevations' on the paper. F-Class and the new F/TR sub-discipline competitors soon took notice of this development and started adopting the new brass, also to reduce long-range elevations. Users soon discovered that the cases were considerably stronger though and survived heavy loads for longer. LP Lapua 308 Win brass only lasted around 3 or 4 firings in hot loads before pockets became slack; Palma variants appeared to have an indefinite life. So, people reasoned they'd safely accept yet heavier loads / higher pressures and this has become a common feature in many F/TR loading practices.

So, even before Lapua made SP Creedmoor brass, shooters interested in pushing their own loads' capabilities in other cartridges started to reform 308 Palma brass into 260, 7mm-08, 243 or whatever. With new companies entering the case market typified by Peterson Cartridge Co., it was a natural evolution to offer two versions of many popular match or long-range gong-shooting etc numbers, so a number of such now exist. With the Creedmoor cases being early members of these companies' ranges, SP/SF-H variants were obvious introductions and have been very successful commercially.

So, the main reasons for adopting this form in 6CM will be the hopes of helping improve precision, but also (likely primarily for many) to 1) run faster and 2) obtain better case life with max pressure loads.

Note also, that the small dia. (1.5mm / 0.059") flash-hole usually comes with the small primer pocket, but not always. Starline has decided to retain the 2mm / 0.079" diameter with its SP brass variants. PPU started producing Grendel brass with the large pocket / large F-H, but users complained of very short case life despite the cartridge's low SAAMI MAP ceiling. (A large primer pocket removes a great deal of metal / strength in its 0.439" dia. case-head, far more proportionately than in the 308 etc' 0.473".) SO, the company changed to the SP format for this model, but also retained the larger 2mm F-H despite the primer size reduction.

The possible downsides of inadvertent or unwise / uninformed SP brass choice in Creedmoor / 308 size cartridges / powder charges where there are such choices include:

• May not give proper ignition with some hard to ignite powder grades. (eg CFE-223 IME in 308 Palma brass)
• May not work well - or at all - in low temperatures, so inadvisable for winter 'hunting' use in cold regions.
• Excessive primer cup cratering, even 'blanking', in actions with large firing pins and / or poor pin tip fit in the bolt-face.
• Risk of seriously over-pressure / dangerous loads if 'unofficial' very heavy SP loads are switched to LP brass without a large charge weight reduction and rework of loads.

 

[mike a]

Small primer brass in larger cartridges (> capacity than that of 6.5X47mm Lapua) has two origins.

The first is that Remington produced very thin-wall SP / small flash-hole 308 Win brass in the dawn of its BR cartridges back in the 1970s/80s. That was because although SAAMI registered, Remington didn't intend making any factory brass or ammo initially. BR adopters bought this special 308 Win brass and used forming die sets / trimmers to make their own. It was variously called 308 Win 'Competition' or 'UBBR' (Unformed Basic Bench Rest). There is still a considerable number of these cases in circulation.

Many people tried loading these 308 cases as supplied and results were mixed, but overall rated unsatisfactory. This was due to perceived ignition (insufficiently vigorous) issues in all but the most favourable combinations and environments. Some people reamed flash-holes out which at least partly solved the problems. So, the idea of SP versions of larger cased numbers (ie larger than the BR and 220 Russian / PPCs etc) pretty well died out for a generation.

Then secondly, around 15 years ago, the US Palma teams started looking at reviving the SP 308 Win with a view to reducing MV ES/SD values. This was driven by a team member whose name I forget who had produced excellent results with Remington UBBR based handloads. The team captains approached Lapua which made up a number of SP cases (easily done as they used the same case-head format as existing Lapua 6BR and 6.5X47mm designs) for team (and company) evaluation. Around the same time, (2004/5) Lapua was developing its 6.5X47mm, and primer / F-H dimensions raised a fundamental design question. Both forms were developed and after extensive trials, the SP / SF-H form was chosen. That raised viable SP powder charges to ~40gn levels from the BR's 30gn.

Meanwhile a full season of secret tests by selected US Palma team members took place in real-range conditions. The US team was then in the run-up to an international 4-yearly World or Palma championship fixture and these tests validated the concept. With the standard US Palma recipe of Lapua case, 155gn Sierra Palma MK and 44 or 45 point something grain charge of H. VarGet, there had been no ignition issues and ES values were reduced by a third. The reduced primer energy saw slightly reduced average MVs and charges were increased to return them to the previous LP brass levels, around 1gn more needed. This was then announced in the US Teams' Forum

http://www.usrifleteams.com/lrforum/

and that the team then being selected and trained up for the following year's fixture would use SP ammunition. It had been cleared with ICFRA and Lapua had adopted the SP brass as a production item and was about to put it on general sale so all competing nations' teams could follow the US example if they so wished. This was a VERY controversial move among American sling shooters and there were many and varied objections to its adoption on the teams' forum. Some questioned its 'legality' but most questioned the decision on the basis that it simply wouldn't work reliably enough given the 1980s' experiences.

The Palma shooters didn't increase pressures / MVs, their interest being entirely in reducing ESs and hence 'elevations' on the paper. F-Class and the new F/TR sub-discipline competitors soon took notice of this development and started adopting the new brass, also to reduce long-range elevations. Users soon discovered that the cases were considerably stronger though and survived heavy loads for longer. LP Lapua 308 Win brass only lasted around 3 or 4 firings in hot loads before pockets became slack; Palma variants appeared to have an indefinite life. So, people reasoned they'd safely accept yet heavier loads / higher pressures and this has become a common feature in many F/TR loading practices.

So, even before Lapua made SP Creedmoor brass, shooters interested in pushing their own loads' capabilities in other cartridges started to reform 308 Palma brass into 260, 7mm-08, 243 or whatever. With new companies entering the case market typified by Peterson Cartridge Co., it was a natural evolution to offer two versions of many popular match or long-range gong-shooting etc numbers, so a number of such now exist. With the Creedmoor cases being early members of these companies' ranges, SP/SF-H variants were obvious introductions and have been very successful commercially.

So, the main reasons for adopting this form in 6CM will be the hopes of helping improve precision, but also (likely primarily for many) to 1) run faster and 2) obtain better case life with max pressure loads.

Note also, that the small dia. (1.5mm / 0.059") flash-hole usually comes with the small primer pocket, but not always. Starline has decided to retain the 2mm / 0.079" diameter with its SP brass variants. PPU started producing Grendel brass with the large pocket / large F-H, but users complained of very short case life despite the cartridge's low SAAMI MAP ceiling. (A large primer pocket removes a great deal of metal / strength in its 0.439" dia. case-head, far more proportionately than in the 308 etc' 0.473".) SO, the company changed to the SP format for this model, but also retained the larger 2mm F-H despite the primer size reduction.

The possible downsides of inadvertent or unwise / uninformed SP brass choice in Creedmoor / 308 size cartridges / powder charges where there are such choices include:

• May not give proper ignition with some hard to ignite powder grades. (eg CFE-223 IME in 308 Palma brass)
• May not work well - or at all - in low temperatures, so inadvisable for winter 'hunting' use in cold regions.
• Excessive primer cup cratering, even 'blanking', in actions with large firing pins and / or poor pin tip fit in the bolt-face.
• Risk of seriously over-pressure / dangerous loads if 'unofficial' very heavy SP loads are switched to LP brass without a large charge weight reduction and rework of loads.

Sir, you are truly a wealth of knowledge. Very good. Thanx for all that you contribute. Mike

 

[Dusty Stevens]

^ thats true, thanks laurie!!

from what ive seen over the long haul, i dont want small primers in anything bigger than a br case. You may get good numbers enough times to fool you with a 243/308 sized case and srp, but its going to bite you someday, and the bad part about it is you may not even know its what did it. Tubb has done lots of tests and you can look at his 6xc sized brass and figure out what he found out. Brass is an expendable component so the pockets getting looser faster on lrp case heads is not a valid excuse either. If theres even a possibility you may shoot in ~60deg or less temps youll see the issue a lot faster

 

[Laurie]

If theres even a possibility you may shoot in ~60deg or less temps youll see the issue a lot faster

I did some winter powder tests in 308 Palma brass when the cases were first introduced. Of necessity, it was a limited sample - Viht N140, N150 and N550; Hodgdon 414 (to get a ball type in).

Temperatures were about 3 or 4-deg C (37-39 deg F) and the (open) ammo boxes were placed with their contents directly exposed to a brisk and very cold wind.

N140 gave sub-standard results and pretty large ES values in the SP brass. Apart from the reduced MV SP effects, N150 and N550 gave very similar results with both types of case / primer. The one powder I'd confidently expected very poor results from - H414 - actually did much better (smaller groups and reduced ES/SD) in SP brass over the LP equivalent over some five charge weights / groups averaged.

Retesting the N140 loads in higher temperatures the following spring (in the 50s) produced a big improvement.

Until a few years ago, Europe's largest annual F-Class match, the GB European Championship meeting with some 180 or so competitors in those days, around half F/TR shooting 308 Win, was held in the first week of November at the UK National Shooting Centre Bisley in southern England. Even with our mild winters, 60 degrees we did not see! Ever! With six individual matches at 800/900/1,000 yards and a Sunday international team match of 15 rounds per competitor at each of those distances, 308 F/TR scores were high, sometimes exceptionally so. The vast majority of F/TR entrants used the SP Palma case, so some pretty large samples found no issues in sub-60 deg temperatures using a pretty large range of powders - H4895, VarGet, IMR-8208XBR, various Viht N100 and 500 series, and no doubt some other IMR, Alliant, Norma and other makes of powder too.

Since those days, I've fired over 1,000 7mm-08 rounds in F-Class over three seasons using reformed SP 308 cases and Rem 7 1/2BR primers with a compressed charge of 47.1gn Viht N160. We shoot F matches all year round (first 2020 match was 4th January; last is 27th December) on an exposed range just under 1,000 ft ASL. Freezing air is uncommon, but temperatures in the 30s, 40s and 50s are the norm (not many in the 60s or above even in high summer up here either!). This load / primer combination has never let me down in any temperature I've shot in with excellent 'elevations'. (The reason for using Palma cases was I had a lot of them spare after switching from F/TR to Open.)

 

[rafale]

I had very good results with Perterson 243 SRP ,using CCI 450 and N 160 and the next step will be with a heavy charge of N 165 . I think
there is no issue with a simple base powder but it's maybe a different story with double base.

 

[Laurie]

I had very good results with Perterson 243 SRP ,using CCI 450 and N 160 and the next step will be with a heavy charge of N 165 . I think

I'm working along the same lines with my 6SLR for which I have 50 Peterson SP 243s ready to reform. If N165 works, I intend to use that powder alone to prolong barrel life as much as possible.

I claim no original thinking here - it was an AS Bulletin feature on Joe Hendricks Jr winning the CMP Cup with his 6mm Competition Match chambered Eliseo Competition Machine RTS tubegun.

Here:

http://bulletin.accurateshooter.com/?s=Joe+Hendricks+Jr&submit=Search

Note this section of the report in particular:

6mm Competition Match Cartridge — Slower Powder Yields Better Barrel Life
My dad was shooting a 6XC for a while and was getting tired of going through almost two barrels a year. So, he came up with the 6mm Competition Match. Like I said, it is a .243 Winchester with a 31-degree shoulder. This delivers the same (if not better) velocity as the other popular 6mm cartridges, but we get almost double the barrel life because we increased the case capacity, so we can shoot a slower burning powder. The barrel I took to Camp Perry that won the CMP Cup had over 3700 rounds on it when I was finished. [EDITOR: Take note readers! Most 6mm barrels are toast after 2500 rounds.] Granted it definitely needed to come off at that point, but it obviously was still shooting well enough to win!

Accurate Load with Peterson Brass, Berger Bullets, and Vihtavuori N165
The two loads I shot all week were Berger 108gr BT behind Vihtavuori N165 in Peterson Cartridge Company brass for 200 and 300 yards, and then Berger 115 VLD behind N165 in Peterson brass for 600 yards. Both loads are easily going over 3000 FPS. I try to only use the best components for reloading, so that’s why I go with Berger, Vihtavuori, and Peterson. Obviously Berger and Vihtavuori quality are pretty known, but I believe Peterson is right up there with Lapua[.] I’ve visited the Petersen factory many times. I’m always blown away by the time and effort Peterson puts into everything.

I use Viht N165 a lot in 284 Win and other cartridges and always found it very easy to work with provided the case capacity is such that you can get a large enough charge in. (The 7mm-08 isn't sadly even with 175/180s, maybe the AI version would have just enough room.) I'd take issue with the report on one thing only. It's not the slower burning powder that yields better barrel life rather N165's modest energy content (the lowest of any powder listed in QuickLOAD) and its consequent cool burning. I've always found it very easy to ignite reliably in all temperatures, so the SP Peterson brass should be OK. (If not, I know SP ignition works fine for N160 and this powder can also be used in the 6SLR / Comp Match.)

I got the rifle back from the gunsmith with its SLR barrel just days before Covid spread throughout the UK and lockdown was imposed, so it has yet to be run in, have a scope mounted etc, never mind loads developed.

 

[lb-ft]

Laurie you're too modest! I've read several of your UK published pieces on primer testing. Extensive, thorough, scientifically approached and very helpful.

http://www.targetshooter.co.uk/?p=1471

 

[Laurie]

@lb-ft. You're very kind sir - I'm embarrassed, but grateful.

 

[Chuckhunter]

Shot 3 variations back in the Eighties with the UBBR Brass, straight .308, 6X44, and then a 30X44. All three shot well with the right powder/bullet combination. Back in those days, nobody was making a lightweight 30 Cal. bullet. Struggled with the 30X44 until I got ahold of some of Ed Watson's 125GR. customs and then the gun took off. My friend Roger Gower won two IBS Hunter Class national championships with the 6X44 and believe he also had a Pa state championship as well. I also believe Joel Kendrick revived that caliber and won the 600 yard shooter of the year with it. It was a real chore forming all of that stuff but fun none the less. That brass was also used by Jim Stekl (not sure of spelling) to make the first Br cases in an attempt to compete with the PPC with and American made cartridge. Sure am glad he did that although never being able to dethrone the PPC the Br sure has achieved an incredible amount of success in other disciplines. Thanks for the trip down memory lane fellows.

 

[Tparrish]

Good read interesting stuff. Got a few questions answered about the SRP in creedmoor case,

 

[LRTom]

I was that US Palma team member that Laurie forgot his name. After winning a US Nat’l, Canadian McDonald Agg and Gov. General using Rem UBBR cases. I approached Lapua with the idea of making a SP 308 case. At the time I had found that using SRP I got better Es/Sd vs. LRP no matter brand or lot. We found the added benefit of holding higher pressures.

 

[Tommie]

What we need is SRP .50 BMG brass to get those SD numbers in line.

 

[Laurie]

I was that US Palma team member that Laurie forgot his name. After winning a US Nat’l, Canadian McDonald Agg and Gov. General using Rem UBBR cases. I approached Lapua with the idea of making a SP 308 case. At the time I had found that using SRP I got better Es/Sd vs. LRP no matter brand or lot. We found the added benefit of holding higher pressures.

Thank you sir (and very well done too for doing the initial work and helping to get the show on the road).

I followed the saga closely at the time on the Long Range Forums. I don't know if it has been archived or deleted since, but haven't managed to find the thread(s) in recent years using the forum's search function.

What I've never seen is an explanation of why SP ignition was 'marginal', or as many of the LR Forum's members alleged worse, back in the UBBR days, but wasn't by the oughties. I've always assumed that the chemistry of powders and/or primers has improved over the years. For example today's powder grain burning behaviour modifier coatings may inhibit initial ignition less than was the case 30 years ago?

Not everyone is convinced that it is adequate. There is one prominent AS Forum member who states that SP ignition isn't consistent / reliable for any case size and powder charge above those of the 6.5X47mm Lapua.

 

[Hohn]

Having excellent results with a full case of RL26 in Peterson SRP 6.5 creedmoor. The most consistent loads I’ve produced yet. Modest pressure and enough speed with 140s and 147s to shoot inside a Dasher.

Did you see the excellent series JOHNNY of Johnny’s reloading bench did on testing SRP brass? He tested several primers, extruded vs ball, full case vs less full, and identified what mattered and didn’t in his SRP starline 6.5 cases.

 

[Hohn]

Not everyone is convinced that it is adequate. There is one prominent AS Forum member who states that SP ignition isn't consistent / reliable for any case size and powder charge above those of the 6.5X47mm Lapua.

The primer only ignites the powder closest to the flash hole. A flame front propagates through the powder column.

The argument strikes me as being akin to saying that, above a certain cylinder size, you need a much more powerful spark plug in your gasoline engine.

 

[msalm]

I had one negative result with a 22 Creed I built using srp Peterson 6mm Creed brass. I had noticeable hang fires when working up loads. I used a flash hole chamfering tool with the larger .080”? tip and opened up the small flash hole to the lrp size and the hang fires went away. This may have been with a ball powder, don’t remember what I was using at the time, with 60gr Sierra TMK.