Small Rifle Primed 308 Win in Cold Weather

T

thymallus arcticus

Member
Rating - 100%
32   0   0
I thought I would share this little tidbit with the CGN community, as it was a question for me until I tried it.

I am low on LR primers but I have a 308 Win that is being picky so I am trying lots of loads and clearly running up against the issue of my dwindling LRP supply. Enter 308 Win small rifle primed brass; obviously, after a little reading I realized that this was not a new thing but it was to me.

I ordered some Starline SRP 308 Brass and grabbed a couple sleeves of Ginex SRPs. Spying the relatively miserable weather in forecast, I loaded up the SRP brass with pretty normal, fullhouse loads of Varget. Last night I cooled the loads outside overnight at -43C and shot them today at around -32C. Everything went bang at normal volume and recoil, and although not chronographed (my chronograph battery said "no way") there was no noticeable change in POI that would suggest the velocities were significantly different than my other LRP loads. Accuracy was tough to tell because it was a new load in a gun that hasn't been my best shooter but most of the loads were better than average so I am chalking it up as win.
 
I was just about to load up with Win 748 but I thought better of it and went with Varget. My rationale being that Varget should be used for the initial test since it is suppose to be one of the more temperature stable powders and I wanted to limit the number of variables. Now that I confirmed for myself that Varget plus SRP works fine in minus 30C, I can start trying the other powders.
 
There’s a really good podcast that called Vortex Nation on Spotify that speak about SRP brass vs LRP brass. Episode 297 is part 2 we’re they talk about the cold and warm weather tests they carried out and what they found. The episode before it called 10 minute talk is part 1. Was interesting, part 2 was quite technical which id be lying if I said I understood it all lol.

Worth a listen though
 
OP, Thanks for the testing you did. I too got fed up with the search and cost of LR primers and finally ordered some Starline .308 Match brass and a couple thousand SRP's

Good to go.
 
Many of the PRS shooters use SRP brass and CCI 450 primers. I use them in both my 6BRs and my 6.5 Creed and I have never had a problem but I also havent shot at minus thirty two with ammo chilled too minus 43. I do coyote hunt but minus 25s my limit. Ball powder as a rule tends to be easier to ignite.
 
I gave the Vortex Nation youtube thing a listen. Other than making my toes curl with the awkwardness of forced humour, I got a kick out the fact that they struggled with maintaining a consistently cold ammunition but clearly worked hard a controlling other factors. It was effectively the opposite situation for me, where the temperature of was the most consistent factor in my testing. It is interesting that they managed to get good results with H4350 in the 6.5CM, particularly in light of my most recent SRP 308 load results. My most recent SRP test was 110gr bullets over full charges of H4198 in Starline Ginex SRP'd brass shot at around -20C with only about 30 minutes of chill time. I got multiple delayed ignitions and a couple FTF. In other words, Varget seemed good in particularly extreme conditions, H4198 was quite poor in a not too extreme of conditions. Next up is H4895.
 
thymallus arcticus said:
I was just about to load up with Win 748 but I thought better of it and went with Varget. My rationale being that Varget should be used for the initial test since it is suppose to be one of the more temperature stable powders and I wanted to limit the number of variables. Now that I confirmed for myself that Varget plus SRP works fine in minus 30C, I can start trying the other powders.
Click to expand...

748 gives me the best accuracy in 223 from 55 grain to 77 grain. However, like you mentioned it's not a fan of temperature change. A few loads that are tack drivers when the weather is between 10-25 degrees, fall to crap when the temps around 30 or into the negatives. In the cold it's usually just a lower fps resulting in my poi dropping (group size stays close enough). Into the 30+ weather they open right up.

I am going to develop some loads this winter with varget or another powder that is temperature insensitive to use when it the temps are out of range for my 748 loads. 748 will remain my primary powder though
 
Today I tried the SRP 308 with H4895 pushing 150 gr bullets. The ammunition was chilled for several hours and shot at about -12C. This time I got out the chronograph which was interesting. One of my initial pressure testing loads with a lower powder charge gave me a delayed fire and about 2200 FPS when the adjacent charges were in the range of 2500 to 2600 fps. This round was nearly off the target at 100 m when the others sat respectably around the point of aim. I also had one round in a test group that was slow (2400 fps when adjacent loads were around 2700 fps). This group wasn't too badly impacted by the velocity change. I am not sure what to make of this but in general the accuracy was about as good as I gotten with any load so I have high hopes despite the strong likelihood that some of my results were flukes. It is going to be warm here over the next little bit so I am going to reload the identical set again and hopefully shoot them when it is above 0C to see how the SRPs do with a few more heat units. If the results are repeated, I might try a LRP loaded set.
 
Unfortunately, this exploration into SRP 308, is due lack of primer options. When I picked up my Ginex SRP (two sleeves), I bought out the local store. If I come across SR mag primers I will give them ago.
 
I use SRP Lapua 308 brass in one of my rifles mostly to essily segregate my Lapua brass for 2 target rifles. One with large primers,one with SRP. My load for both rifles is 185 Juggernaughts over Varget, Federal Matcvh LR primers and CCI450 srp. The loads are 0.2 gram different. Velocities had no variance when I shot these loads in May, July, and in the snow in January.Ammo sits in my truck overnight before range trip.
Main benefit of the SRP brass is supposed to be delay in developing loose primer pockets. Only issue I ran into was figuring out getting the right size depriming pin for the Lapua brass (it's smaller than the "standard" SRP pin in my dies. After 4 resizings I have not noted any difference yet.
 
I've wondered about SRP brass in my .243 Win., and just what the advantage is in having the smaller primer and flashhole. Is the advantage supposed to be better accuracy? And is there any evidence of this from those who've used it?
 
South Pender said:
I've wondered about SRP brass in my .243 Win., and just what the advantage is in having the smaller primer and flashhole. Is the advantage supposed to be better accuracy? And is there any evidence of this from those who've used it?
Click to expand...

the way I understand it is the pockets handle more firings at top pressures before they bag out.
 
I’m gearing up for lobbing cast out of a 450bm and discovered that hornady uses lrp for one line of factory loads and srp for another. This put me at a crossroads for which to use so I snooped around castboolits and the 450 forum to discover some anecdotal information about small primers in large cases causing in certain subsonic loads; squibs and certain compressed loads; poor powder burns and erratic velocities, however regular loads (say supersonic non compressed) were fine. There was a consensus that the flame from a srp was insufficient to ignite the powder on either extreme before the bullet entered the bore. This may also hold some weight in regards to non temperature stable powder as well.

As mentioned, I don’t know if any of this is true so I opted for lrp (which I have) over msrp (which I don’t but also recommend by others) to error on the side of caution if this information is indeed, fact.
 
Last edited:
You must log in or register to reply here.
Back
Top Bottom