Let’s look at SR primers. I tried a total of 15 from 10 manufacturers, with a 16th as the aforementioned follow-on which became available after the others were ‘done’. (Actually, this became 14 and 15th after one of the originals had to be withdrawn). In addition to the commonly available American makes, five European manufacturers were represented (Fiocchi from Italy, Russian Murom, Serbian Prvi Partizan, – ‘PPU’ as it’s usually abbreviated to – Czech Sellier & Bellot / S&B, and Finnish Vihtavuori). There was one from South America, the Brazilian CBC Magtech 7½ model. Missing this time round were Sweden’s Norma and Germany’s RWS, neither seen much in the UK these days.
The original 15
But first, we have to mention seating them – in cases that had been cleaned, sized and annealed before being used in the tests. Case-pockets were cleaned and the new caps inserted using the Lee Auto-Prime XR hand tool, the one with the square primer magazine. Sinclair International describes the tool as ‘semi-sensitive’, a description I’d agree with for LR primers but, as the SR variety seat with much less effort, I find it 90% plus sensitive in this role, all bar the occasional cap being easily ‘felt’ into the fully bottomed-out position and then given a tad more pressure on the handle. To me, this is the first plus in SRP 308 brass over the traditional LRP type and a not insignificant one at that – the more consistently and sensitively one seats primers, the better the chance of good performance.
Lee Auto-Prime XR hand tool
The intertwined issues of names and types were confusing enough when we looked at large primers a couple of years ago. There is no across the board standard system of naming either size but at least the word ‘Magnum’ was generally used to describe more ‘powerful’ versions when dealing with LR models – many recommended only for use with very large-capacity cases and truly heavy powder charges as in the Weatherby and Remington ‘Ultra’ Magnums. Moreover, irrespective of make and type, all LR primers are specified to use 0.027” thick brass cups. When we get to SR primers, ‘magnum’ may have a different meaning.
To understand the issues at play here, we need to travel back nearly 90 years. The original SR primer was developed in the late 1920s for the 22 Hornet with its 43,500 psi maximum pressure followed by other small, relatively low pressure designs such as the 218 Bee. As it was common practice in those cash-strapped depression-era times for 22 LR rimfires to be converted to handle these little centrefires, old Martini Cadet actions also employed, many rifles had less firing-pin energy available than that in actions designed around larger, higher pressure centrefire rounds such as the 30-06 and 270 Winchester. Put the two issues together and a thick tough cup was not only unneeded by the cartridge but was actually undesirable. With the Hornet becoming a popular number in the 1930s and 40s especially in the USA, Winchester, Remington and CCI made SR primers with this in mind and today’s CCI-400 and Remington 6½ models haven’t changed in this respect from their introduction having thin (0.020”) cups.
The little 1930s .22 Hornet used weak primer cups, this needed with many rifles being converted rimfires.
It was only when Remington launched its 222 in 1950 that we start to see SRP-using high performance varmint cartridges appear. Even at that, the triple-two is rated at 50,000 psi, mild by today’s standards although it appears Remington developed its thicker (0.025”) cup No. 7½ primer for factory loads in this cartridge. Although sometimes described as an ‘SR magnum’, I believe the only difference between them is in the cup thickness, the contents being identical. (The 7½BR appears to be somewhat different having been developed for the larger ‘hotter’ 17 Remington cartridge. It seems this version has superseded the plain 7½ which is no longer listed by Remington). Depending on the compiler, loading manuals can specify either standard or SR Magnum grades for the 222 Rem.
The 222 Remington needed a ‘tougher’ primer than the Hornet, hence Remington’s No. 7½ SRM
Move onto higher pressure cartridges still and ‘hard’ primers become essential. Remington used to attach a warning to its No. 6½ standard SR model which seems to have disappeared from its own literature but is still quoted by American components supplier Midsouth in its online catalogue:
Warning: Remington does not recommend this primer for use in the 17 Remington, 222 Remington, 223 Remington, 204 Ruger, 17 Remington Fireball. Use the 7-1/2 Small Rifle Bench Rest primer in these cartridges.
The 6-1/2 Small Rifle primer is primarily designed for use in the 22 Hornet.
We actually have three cup thickness specifications in use:
0.020”. Remington 6½, CCI-400 and (maybe) Winchester WSR the latter reputed to be 0.021” thick. The original Russian (Murom) PMC standard SR model with deep copper colour cups turns out to be equally weak, either through metal thickness and/or the material employed.
0.0225”. Federal 205 and 205M (match) models. They are said to be different grades / lots of the same product, the M version selected for its lot consistency.
0.025”. CCI-450 (SR Magnum), CCI-BR4 (Magnum / match); CBC Magtech 7½; PMC /Murom SR Magnum and Murom brand SR223.
As to the others tried from PPU, Fiocchi and Sellier & Bellot there is no indication of ‘type’ on the packaging, nor have I been able to find anything relevant online but, I can say that none produced any pressure-induced problems in my tests. However, I shot them in a custom FTR orientated action and use in an AR-15 type rifle may show up deficiencies that I wouldn’t see.
223 Remington and 5.56mm need strong, thick-cup primers especially when used in AR-15 type rifles with their floating firing pins. (CCI also makes a milspec version called the CCI-41.)
Cratering and Blanking
Despite BR/Magnum models with their thicker cups being stronger than the original standard grades, they will still ‘crater’/‘blank’ with 50,000 psi plus loadings in a rifle with a fat firing-pin and/or one that is a poor fit in the bolt-face aperture thereby allowing primer cup metal to be extruded into it.
A cautionary tale is that of my FN Special Police Rifle (‘SPR’), an excellent longarm based around selected pre-64 type Winchester M70 actions and in a Macmillan A4 stock that really suits my shooting position and style. It was originally bought in 308 Win chambering and used in the first season of GB FTR class competition including some GBFCA National League rounds where its 24-inch barrel proved to be a fatal handicap on 1000 yard stages, the rifle (unsurprisingly) being incapable of producing the necessary MVs. With a custom-built rifle replacing it in season two, I had to decide what to do with the SPR as I had no use for a tactical/general-purpose 308. Sell it? …. or rebarrell it to something better suited to my shooting needs?
The latter option won out and, as the then recently introduced 6.5X47 Lapua was the wonder-cartridge of the age, that was the obvious choice. Unfortunately, with the FN/M70’s bolt employing a super-fat firing pin, it turned out to be a poor one – SR Magnum primers cratered noticeably at Viht’s mild starting load pressures and started ‘blanking’ at a mere 1.5-2gn higher levels. There is a minor gunsmithing industry in the USA bushing factory rifle bolts and turning their firing pins down, but nobody offered this service here at the time.
Cratered and one ‘blanked’ Remington 7½BR primers in 6.5X47 Lapua rounds fired in the FN SPR – a rifle bolt issue, not primer cup strength.
So, the rifle was simply re-chambered to the LRP-equipped 260 Rem cartridge and the problem was solved. Why SR primers ‘crater’ or fail in the form of ‘blanking’ so readily, compared to their LRP equivalents, at any given peak pressure is one of those gunsmithing mysteries that I’ve never understood – but unfortunately it’s a fact of life one has to be aware of if choosing one of the growing number of high-performance/precision cartridge designs that now employ them. Custom match and BR actions are OK in this regard, it’s a potential issue with mass-produced factory numbers – and many of them are either unaffected or even if they are, not badly enough to require more than modest downloading.
That was a rifle related issue, either as a standalone factor or one that worsens problems emanating from the primer itself in the form of a weak cup. The Stolle Atlas match action in my FTR rifle used for the tests doesn’t suffer this, so any primer failure comes from weaknesses in that component when subjected to higher pressures than it was designed to deal with. Problems potentially come in two forms, usually in combination when the cause is bolt-related. ‘Cratering’ sees primer-cup material extruded around the still protruding firing pin tip immediately after ignition leaving a raised ring, or ‘crater’ around the pin indent in the primer-cup face.
Cratered Remington 6½ primers in test cartridges. Note the pinhole in the bottom right example
If stresses/extrusion become excessive, a small disk or sometimes a cylindrical plug of extruded brass shears out of the centre of the cup (‘blanking’) and is usually blown into the bolt body after the firing-pin tip retracts. The shooter may notice a wisp of smoke seep out of the action, even feel a breath of escaping gas or kick on the trigger. This is very undesirable as it will erode the firing-pin tip and can damage/affect the trigger mechanism and its settings. The displaced brass disk(s) blown back into the bolt affect striker fall making it inconsistent or in a worst case scenario produce light strikes and mis/hang-fires.
Whilst ‘blanking’ often occurs as a result of severe ‘cratering’ that has overtaxed the cup’s metal, it can also occur on its own with very ‘soft’ primers, the cup simply failing with little or even any surrounding ring or crater visible. This either/or result was what I saw during my tests with ‘cratering’ evident on four or five models, two – CCI-400 and Remington 6½ – severely, the others so mildly as to be ignored and a single model, Vihtavuori’s No. 22 suffering two blanked examples in six rounds.
‘Blanked’ Vihtavuori primers – use was discontinued after the second occurrence and the remaining rounds ‘pulled’
If your Remy 700 PSS or suchlike produces severely cratered primers, the first question I ask owners when they seek advice is what SRP model is being used. If the answer is, as it usually turns out, to be the CCI-400, PMC, or Rem 6½ standard types, my response is to switch to ‘Magnum’ (or BR) models. I first have to overcome user objections based on misconceptions about SR ‘Magnums’ that the 223 (or whatever) is far too small a cartridge to need a magnum primer. Forget the ‘magnum’ label – more often than not it’s a misnomer for what should really be called ‘heavy duty primers’ and as I’ll show in the test results in Part 3, there is little difference in average MVs and SDs between types in the 308 ‘Palma’ case at any rate. Switching to a Magnum/BR type may not cure a 700’s tendency to crater primers completely but it usually makes the problem manageable. If it doesn’t, then load reduction or a bolt-bushing job is called for.
Weak thin-cup models.
So, let’s see what primer manufacturers and others say about SRP types. We’ve already covered CCI and Remington models – the No. 400 and 6½ grades ‘soft’, the others (No.s 450, BR4, 7½BR) with thicker, harder cups for high-pressure cartridges and loads. Within that, the two CCI models have a reputation for being the ‘hardest’ out there – if you ‘blank’ those, you’ve got problems! There is another CCI model that I’ve never seen in the UK, the No. 41 military spec product. It is akin to the 450 SRM but has the anvil-depth repositioned in the cup to allow for inadvertent strikes from AR-15 type military rifles’ floating firing-pins, thereby guarding against slamfires or other highly undesirable unplanned ignition occurrences.
Strong / thick cup ‘Magnum’ or BR primers
Winchester only makes a single SR model, the WSR. When I shot a straight-pull AR-15 many years back this was the primer to use – cheap, widely available, ‘hard’ and reliable – largely based on US XTC practice where most competitors preferred it. This version was ‘silver’ (nickel plated) and very tough, then Winchester changed its specifications maybe 10 years ago, the ‘new’ brass colour WSR proving much ‘softer’ and now prone to ‘blank’ in ARs. It is said to have 0.021”, therefore thin, cup metal. I had no problems with it in either of my tests, so it is apparently strong enough for a tightly-breached bolt-action.
Russian primers present major nomenclature and categorisation problems. First off, there are four names in play – PMC, Murom, Tula, and Wolf, of which the last pair are better known to American handloaders than to Europeans. There is a degree of disagreement on US shooting forums as to whether Wolf and Tula are the same product with many respondents adamant, they’re not. All the research results I’ve dredged up suggest that irrespective of name they originate in the one outfit, the JSC (joint stock company?) ‘Murom Apparatus Producing Company’ whose registered address is in Murom City in western Russia. Murom works closely with Russian ammunition manufacturers Wolf and Barnaul. (‘Tula’ and ‘Wolf’ do appear to be different outfits but source identical primers from Murom for their US imports).
We first received Murom manufactured primers in the UK under the PMC label. PMC = the Poongsang Metals Corporation, a large South Korean ammunition manufacturer. This was some 15-20 years ago and the name disappeared here maybe some 10 years back so, anything so branded is old stock. Recent Russian primers sold in Europe are branded ‘Murom’ – but no new supplies are coming into the EU or USA under whatever brand name because of joint trade sanctions set up against Putin’s Russian Federation resulting from its recent Crimea and eastern Ukraine land grabs.
PMC set up a US subsidiary originally in California, later Nevada, to import and market its ROK manufactured pistol and military rifle ammunition (but used various alternative company names to westernise itself, ‘Pan Metal Corp. being one). Later, it created an in-country manufacturing arm for sporting ammunition marketed as PMC or for its premium grades loaded with Barnes bullets, the El Dorado Cartridge Co. It also supplied brass and primers to handloaders which is where Murom enters the picture, its products rebranded as PMC. They arrived here via Germany and UK importer York Guns Limited.
There were two SR PMC models, the standard grade (KVB-223) and SR Magnum (KVB-223M?). The former is a deep copper colour, apparently from the cup metal itself not plating and is very ‘soft’. I first encountered this model in my straight-pull AR-15 days and mid-pressure 69gn match loads produced a high percentage of ‘blanked’ examples. This model appears to just hold together when used in tight/small firing-pin custom-action rifles but, as we’ll see in Part 3, fired examples go pancake flat erroneously suggesting excessive pressures for those read the runes from fired primer appearance. The SR Magnum version was ‘silver’ colour (nickel plated) and as ‘tough’ as the CCI-450/BR4 duo but, in ignition terms, milder than either in small cartridges such as the 223 Rem. Word had it that as with the Remington 6½/7½ twosome, the Standard and Magnum versions’ internals are identical and they differ only in their cup thickness/strength.
The weak ‘standard’ copper-colour PMC branded version still turns up regularly in gunshops or classifieds, so be sure of what you’re buying. This model is likely to crater badly in your average Remington 700 or Savage 10/12 but, if you hear of any of the SRMs for sale, grab them.
Under the Murom / Tula / Wolf names and more recent production there appears to be three models now:
KVB-223 (standard Small Rifle). No longer copper-colour, instead ‘brass’ (plated?), this may or may not be the same as the old PMC version. In any event, it is still regarded as too weak for many cartridges and actions, especially 223 Rem ARs.
KVB-5,56M (Small Rifle Magnum). ‘Silver’ appearance. As the name suggests, it is a tougher milspec version suitable for 5.56mm pressures and automatic weapons. As before, the contents and ignition performance are unchanged from the standard KVB-223 version. Some US AR-15 shooters complain of poor/failed ignition with St. Marks Powder Co. Winchester/Hodgdon ball powders. (This may be a primer seating issue too as Murom primers are sometimes a tight fit and shooters don’t press them fully home).
KVB-223M (Small Rifle 223 REM / SR223). Brass-coloured cups. This is a ‘tough’ example as per the ‘Magnum’ but is described as being slightly more powerful and better suited to ‘hard to ignite’ ball powders. This model in Wolf or Tula guise has become a favourite of the many 223 Rem AR-15 users who choose ball powders for their good metering characteristics in high output progressive press loading. (I’ve also seen it described as Murom works coding ‘KVB-223REM’).
Two Russian SR primer models with deceptively similar names but very different characteristics. The older PMC ‘Small Rifle’ model (bottom / copper cups) is weak and unsuitable for many applications; the Murom ‘Small Rifle 223 Rem’ top is both tougher and ‘hotter’
There is an unfortunate matter here though. With such confusion over names and descriptions, the ‘KVB-whatever’ factory product name is the best way of differentiating between the various Murom manufactured types. Crazily, it doesn’t appear anywhere on the 100 primer tray sleeve or the 10-tray 1000 ct. box. The only place you’ll find the Murom OEM description is on the 5000 primer cardboard ‘outer’ (packaging) that they leave the factory in. OK if you’re able to buy 5000 in this form but a problem if your local retailer has unpacked them and stacked them as 1000 ct. boxes on his shelf!
Getting a Load
Having cleaned, sized, annealed and primed my 100 twice-fired ‘Palma’ cases, I needed a load to use throughout the tests, working charges up to produce full working pressures. The primer used here was the CCI-BR4 match product, same as I use in my FTR ammunition. I also wanted to compare this with the results from standard (LRP) Lapua .308 Win cases – same bullets and powder. Vihtavuori’s 308 Win loads data page on its website gave a maximum load of 44.8gn N150 with the 167gn Scenar at 2.795” COAL – a cartridge length I couldn’t use in my rifle’s chamber as even with its slightly longer ‘freebore’ to suit long 155s seated shallow, the 167 ran into the lands at a much shorter COAL and had to be seated very deep – therefore raising pressures significantly.
The QuickLOAD PC program computed 45.0gn N150 at the actual usable COAL as producing 2800 fps MV (32-inch barrel, remember) for a PMax of 55,488 psi, a bit low compared to the SAAMI allowed MAP of 62,000 psi but giving some essential ‘wriggle-room’ should the model underestimate pressures. This result is of course for standard LRP brass/primers and 25 brand new Lapua examples were used, unaltered except for an inside mouth-chamfer to avoid damaging bullets during seating, and the necks run over a mandrel expander to ensure roundness and reduce Lapua’s very high ‘out of the box’ neck-tension. Italian Fiocchi standard LR primers were carefully seated and charge weights of N150 rose from 43 to 45gn in half-grain steps for this ‘control group’.
I previously mentioned that the Palma shooters had found that the SRP case needs heavier charges to achieve the same MVs, my experience at that time being it’s usually around a half-grain or slightly more with Hodgdon’s ADI manufactured powders (H4895, VarGet, IMR-8208 XBR), so a slightly heavier top load was in order for the SRP work-up batches. As the ‘Palma’ case is very strong, I decided to push the boat out a little further still, loading 30 rounds covering 43 to 46gn in five-round batches, a full grain step between the first pair, the others in half-grain moves as per the ‘control’ LRP cartridges. Two additional ‘starting load’ 43gn charge examples were loaded to foul the barrel before starting to measure and record MVs.
Heavy charges can be used in this cartridge-case because it is so strong and accepts pressures that wear LRP equivalents out in a few firing cycles but, I suspect something else is in play here. I think the small flash-hole may change charge burn-behaviours, especially in the early stages where pressures peak. If so, this could reduce the peak pressures generated with any particular combination. However, I’ve no evidence for this assertion and must offer it as a hypothesis, not proven fact.
In any event, I’d decided to go with 46gn as a top load in the ‘Palma’ version, a full grain weight up on the top LRP batch charge. The test loads using the two case types were shot at 100 yards side by side in a cool but pleasant early September day on Diggle Ranges with temperatures around 13-deg C. (56/57-deg F to our American readers). These and all subsequent test groups were fired with a MagnetoSpeed V3 bayo’ attached to the barrel – this affects group patterns and POI but the use of the tool was a constant affecting all combinations equally and the rifle was rezeroed to take this into account.
The Osprey Rifles Stolle Atlas based FTR rifle with MagnetoSpeed V3 chronograph photographed during a barrel cooling break while working the Palma brass test loads up
I have seen shooters state on forum posts or elsewhere, that the two varieties of Lapua 308 Win case have different capacities. If this happens, I suspect it is a production lot issue as the water capacity of fireformed cases bought at the same time have been nearly identical in my experience – 56.1gn water here and that’s what I input in QuickLOAD. QuickLOAD has no primer type adjustment facility, so one has to ‘fiddle’ charge weights for SRP results to obtain matching computed MVs to see where actual pressures lie.
What do I mean by that? Well, QL predicts 2857 fps from my top SRP 46.0gn charge weight at over 60,000 psi PMax but, as we’ll see below, the program underestimated LRP brass MVs and hence pressures and, less surprisingly, went the other way with the SRP type, the less vigorous primer and small flash-hole reducing actual performance and pressures. So, I simply reduced the charge-weight in the QL entry box until predicted MVs matched actual SRP velocities – in this case a relatively small ‘fiddle factor’ but which reduced the calculated pressure value by 3,000 psi.
Range Day One
So finally, after all the planning, components stocktaking, looking up loads tables and QuickLOAD modelling, it was off to the 100 yard benchrest range to shoot the initial 57 test cartridges split 25/32 LRP/SRP with rising charge-weights to see what they did on the paper and through chronograph readouts. The conventional LRP Lapua case based loads were shot first, the clean bore fouled with the first group, a breather taken mid-session to avoid ‘over-cooking’ the barrel. The first thing to note was that MVs were higher than QuickLOAD predicted, the top load of 45gn N150 seeing 2841 fps compared to the program’s computed 2,801. This represents some additional 3000 psi chamber pressure (hence the need for the aforementioned ‘wriggle-room’) and likely saw a PMax value around 58,600 psi – where we want to be and still within the SAAMI 62,000 psi envelope. (However, at that level, LRP cases would likely be fit only for the scrap bin after a half-dozen firings).
Yes, Vihtavuori once made primers – some ancient No. 22 SR examples found in a gunshop clearout and probably dating from the 1980s.
They proved hopelessly fragile in this application. However, whilst pressures/MVs were OK, nothing else was! Groups were dire, velocity spreads not much better. Even with the MagnetoSpeed attached, groups running from half to nearly an inch averaging around two-thirds were well below expectations. MV ES values started out poor too with 37 and 52 fps spreads over the first two fouled-barrel strings, then improving to the high teens with the final pair.
As I have had good experiences with the brass, primer and powder with various bullets in the rifle and it normally performs well with new cases in the ‘minimum SAAMI’ chamber, this suggested the problem lay with the 167gn Scenar. Given the need for the very deep bullet-seating/short COAL to keep it off the lands, I was concerned that the bullet was a poor match to the chamber and/or bore dimensions. Having to start again from scratch would be a serious setback with winter approaching, not to mention the cost of getting on for 400 Bergers in place of available Scenars that I’d no longer use in competition. I was worried!
The ‘control’ Large Rifle primer cartridges gave disappointing results alongside higher than predicted velocities
The barrel was allowed to cool completely, cleaned and a couple of fouling shots fired before putting the six five-round groups using the ‘Palma’ brass downrange, again taking breaks to avoid barrel overheating. An improvement over LRP results quickly became apparent given a final spread of 0.2 to 0.6-inch groups averaging 0.47” and ES values running from 11 to 19 fps averaging 15.
45.5gn gave a nicely shaped 0.2-inch group – actually in the high ‘ones’ on re-measuring it with callipers. Note – nothing had been changed other than the case type – even the MagnetoSpeed bayo’ had been left on between sessions and during barrel-cleaning avoiding any repositioning that could affect barrel-harmonics.
The other big difference was average recorded MVs – they were well down on those from the LRP brass results. (See Table 1.) The ‘Palma’ case 45.0gn value was 2,786 fps compared to 2,841 fps from its large-primer stablemate. Even the top ‘Palma’ charge of 46gn at 2828 fps was still below that (45gn) LRP value. So, instead of the expected half-grain charge discrepancy, maybe 0.7gn tops, the SRP brass needed an additional 1.4gn N150 to match LRP velocities. I can’t explain it but that’s what the chronograph reported! With the superb sub 0.2” group, 45.5gn at 2809 fps MV, with an only so-so 17 fps velocity spread was chosen for the subsequent SR primer tests.
Fiddling charge values around in QuickLOAD to get that velocity suggests pressures were running at a comfortable 57,700 psi – plenty of safety margin, not too punishing on the barrel (not at all on ‘Palma’ cases) but high enough to produce 100% charge burn and work efficiently.
The SRP ‘Palma’ work-up loads gave much lower velocities and reduced group sizes
Putting aside any qualitative changes in results from the two types of case, this shows up another important issue. Loading manual and manufacturers’ loads data are usually accompanied by a warning that the loads quoted and performance attained only apply to that exact combination of components. Different makes of brass have different capacities for instance affecting pressures and safe maximum loads. It is apparent that ‘Palma type’ brass is rather different from anything else available in this respect, almost creating a new sub-species of the 308 Winchester.
When loading ‘Palma’ brass using ‘ordinary’ 308 Win loads table data from published sources, any error is ‘right-side’, ie discrepancies result in lower pressures and velocities. However, given the widespread adoption of the ‘Palma’ case by keen long-range target shooters who often maximise velocities with really ‘hot’, punishing loads and the equally widespread dissemination of same in range-house chats or on Internet forums, one has to be even more careful than usual in adopting other people’s ‘recommendations’. It is essential to ascertain the case and primer makes/types.
Putting another shooter’s already high-pressure ‘Palma’ case load into any LRP hull is a failsafe recipe for producing an excessive pressure load, potentially one that is dangerously so. Doing so for a heavy, thick-wall low capacity LRP model could well see you counting fingers after taking a shot. Be warned!
So in line with my own strictures, be aware that the 46gn N150 charge used in the SRP brass work-up is 1.2gn above Vihtavuori’s maximum charge for standard LRP Lapua brass based handloads and will produce excessive pressures in it!
Part 3 will cover the primer model chronograph tests and the match load primer ‘toughness’ trial. I’ll also look at the remaining small primer/flash-hole 308 Win ‘issue’ – temperature effects, or more prosaically, can one use these cases in cold weather and/or with all powder types?