308 Win LRPs v SRPs

[Tony Z]

As promised post cyclone Narromine. I pulled the 636 barrel from the HG and replaced it with the Hart 12 twist 308 barrel and tube.
I went with more general components and away from the usual Re15 i would normally use.
Cases were picked at random from the box then FL sized, flash holes uniformed etc etc.
Primers were the usual suspects 210Ms, 205Ms and CCI 450s.
Powder was a somewhat older batch of 2208 and all charges weighed at 43 grains.
The 175 SMKs were length and ogive sorted only. Cartridge concentricity was checked and all straightened to a thou or better.
All groups were shot at 200 yards in mild wind but with another annoying mirage plaguing all our testing throughout the year.

The pic tells the story but do ignore the high shot on the 450 group. That was shooter error and was called before it was seen. Shooter basically went to sleep and the mirage bit.
There is not enough there to call anything at this short range but there is a clear POI shift. Small, but it is there and knowing how tubes work, that shift is from velocity drop. The group sizes are too close to call time so 600 yards in a week will maybe show a different result.

[Camel]

So what is your preference small or large, and reasoning behind that preference ?

I have been wondering if there would be much difference in the two, thinking of my 25 Camel, at the moment I am using LRP in Lapua Match 308 brass sized down, been wondering if there would be much difference if I used small primer pocket brass ??

Second question, whats the difference between normal brass and Palma brass ??

[Tony Z]

That is the point of the exercise Mark. Firstly with the 308 and then with a 260 and a far slower powder in Re26 at a later time to see for myself which primer option is capable of delivering smaller group aggregates. You read a lot of stuff on both sides of the primer debate, if we can call it that. I have zero interest in SDs or ESs. I just want to see what the target tells me.
All is equal except for primer, so let's see what works when we add another 400 yards. If it is as stated that SRPs and the 62 thou flash hole help deliver lower velocity spread, then we should see the result of that theory at 600 yards next week. With all things equal at 200 yards today, i will wait until all the evidence is in.

[dg]

g'day tony

speaking of primer size comparisons and testing, on a different track I had the idea a few years ago (lots of ideas with little success btw) to wonder and think about, what would happen if the primer flash was coned into the flash hole rather than ignite and then take roughly a 90 degree diversion before entering the flash hole.

to do this the following implements were made to suit small rifle primers.

one is adjustable.





i did modify the primer pockets on a few 6x47 and 6mmBR cases, but in limited testing due to less than desirable ND conditions at the time ,i never reached any conclusions , good or bad.

if you would like to have a play with them, I will send them to Townsville.

cheers
dave

[Tony Z]

Dave i often wondered if we chamfer the wrong end of flash holes that actually funnels pressure back onto the primer cup. Interesting idea with the tooling there Dave. That might need further investigation at a later date.

[Tony Z]

Well we shot 600 today. As per the script the winds were twitchy and the mirage was obscene as it always is.

This is what resulted, no mitigating circumstances or excuses as there always is, so like golf it's not how, but how many on the board that is seen.
All loads were 175 SMKs 43 grains of 2208 in weight sorted FL sized cases. Just the primers were varied as per the test pictured from last week at 200. Remember, there was no lead up load development here of any sort. Good components in a very good barrel in a 60 pound HG.

In order of firing, group size then score.

210Ms 4.488" 40pts
205Ms 2.106" 44 pts
210Ms 2.815" 46.1 pts
CCI 450s 3.720" 45 pts

It is worth mentioning that prevailing conditions of the first 210M firing was horrid, the 205Ms had as bad which makes them all the more impressive. The CCI 450s had the best opportunity to shoot tight and didn't.
The Fed 205s impacted just under 0.5 MOA lower than the 210Ms. The CCI 450s impacted just under 0.75 MOA lower than the 210Ms. So what is going on here? 450s are said to have the same brisance as 210s so one would expect similar results. Clearly not so.
Now people are going to mention a few things here, one being that barrel exit time may be the reason for the drop. Not the case with a stretcher tube. Velocity rises bullet hits high. Drops and it hits low. US forums say to get the same velocity with SRPs as LRPs, add about half a grain. That is what i see here.

Now two things stick out for me. 205Ms, the darling of SR BR shooters shot the best group in probably the worst condition. The CCI 450, the darling of the LR BR boys, shot an ordinary group in the best conditions and clearly showed a vertical spread and the lowest POI in the sighters. Someting is amiss.
It gets back to what i have come to realize in other cartridges. Magnum primers ignite more powder more completely and lower peak pressure by early movement of the projectile creating a larger chamber volume. I certainly would not advise to take it across the spectrum of all cartridges, but I have seen this in the 636 with Re15 very recently. Loads that are seen as mild when using 450s, hurt cases or show signs of pressure with other milder SRPs. A complete reversal of expectation.
My bet is 450s and 44 grains of 2208 would tighten the group and bring the cartridge back up to pressure. The load dropped off the pressure node, hence the vertical in the sighters and the group. Remember, 43 grains of Varget and the 175 SMK was in the M118 match load for years in the US military until recently replaced by Re15. So there is past form here and why i picked that exact formula to begin with as many of my 308s have and still do shoot this load extremely well.

As a conclusion it would be remiss of me to not take the SRP cases and 205Ms and tweak the load a bit to shoot an entire match at 600 yards. So it looks like the 260 test may have to wait or be transfered to another rifle.


As a footnote to this. I watched Dan Galea for most of the week down there at Narromine. His results were very impressive. The load was Lapua Palma cases, 155 Bergers very very lightly tipped (barely perceptible), 46 grains of 2208 and 205Ms.

[RDavies]

g'day tony

speaking of primer size comparisons and testing, on a different track I had the idea a few years ago (lots of ideas with little success btw) to wonder and think about, what would happen if the primer flash was coned into the flash hole rather than ignite and then take roughly a 90 degree diversion before entering the flash hole.

to do this the following implements were made to suit small rifle primers.

one is adjustable.





i did modify the primer pockets on a few 6x47 and 6mmBR cases, but in limited testing due to less than desirable ND conditions at the time ,i never reached any conclusions , good or bad.

if you would like to have a play with them, I will send them to Townsville.

cheers
dave

It would be interesting to do a good test over the cronograph after prepping with these coned reamers.

[Tony Z]

There may be more to this than we think. You are a very lateral thinker Dave. And to think you spent all those years as Glen McGrath's batting coach

https://en.m.wikipedia.org/wiki/De_Laval_nozzle

The half angle mentioned at 15 degrees being 98% efficient is, as luck would have it, exactly what centering drills are. We do one side but not the other. This needs further investigation.

[Tony Z]

Well we shot 600 yesterday afternoon and as expected the weather was crap. The aggregate was not great but the groups were very good for vertical and held waterline. I increased the load with the 205s by 0.3 grains to bring the velocity up to the LRP POI and shot the four targets with that. If i had to make a judgement i would say that the 308 SRP brass holds a tighter vertical with this barrel in this gun which would mean on a more compliant set of conditions it would in my mind shoot a tighter aggregate.

As for the 260 that i have been playing with in my Defiance action. Tested the 130 and 140 RDFs in both SRP and LRP Lapua cases with H4350, H1000 and Re23. With the H4350 the results were acceptable but the LRPs were holding tighter groups when the charges were around or over 42 grains. With H1000 the SRPs are a no go area at any level of charge in my view. The distinct click bang is around one millisecond away from shrapnel.
The Re 23 loads with the LRPs in the 260 with both the 130 and 140 RDFs is nothing short of extraordinary. I borrowed a Magnetospeed out of curiosity to get the final settled load velocity with the 130s from the 27 inch barrel at just shy of 3100 fps and the 140s were a little over 2900 fps. At no time were cases stressed. Accuracy was sub inch at 300 yards with both bullets where if i had to pick one, i would go with the 130s. They seemed a better balance with this case and Re23.
Unfortunately not so with the SRP cases. Re23 with the SRP cases is not as scary as H1000 but accuracy was at times atrocious with patterns rather than groups.
To try and get some sort of sense of what was going on, i went to a faster powder in 2208 and the 130s. At 37 grains both the LRP and SRP cases shot OK and were about at max load with similar grouping at something around 2800 fps. I have no doubt that with a bit of work i could get 2208 and the 130s in the SRP cases to shoot very well. But at nearly 300 fps slower speed why would anyone bother?
So unlike the 308 and the quicker 2208, the 260 with slower powders to try and get the really usable velocities needs something like the 210Ms to get things working properly in my view. I didn't attempt to drill the flasholes like i have heard and read of others doing, nor did i use the Synoxid RWS SRPs to try and get the slower powders to work. Not realistic either way and really defeats the theory of why SRPs and 62 thou flash holes are used.
I remain, once again, highly suspicious of claims of SRPs in medium sized cases and slow powders being the better option. Maybe with H4350 in another barrel. Maybe and possibly with newer lots being a fair bit quicker than the 1997 lot i used. But to me this is a variable i would illiminate before i fired a shot. Barrels have a very short window of accuracy for competition to try something that is fashionable over functional.

As a caveat for accuracy. At a 100 yards some of the initial test groups (three shot) with the SRPs and Re23 looked acceptable. But at 300 yards and multiple five shot groups the inconsistencies showed up on paper. Don't be fooled into thinking you have hit gold until you take the load out to atleast 300 yards. 500 is better still.
By acceptable i mean 1 MOA or 3 inches at 300 yards is simply not acceptable yet many of the SRP loads could better that and some did do way better than that.
This is where people are getting duped i feel. The accuracy testing is testing relevant to what? It may seem good when compared to nothing else at that time, but when things are head to head, same barrel same moment, then it becomes very clear as to what works or doesn't. The SRPs in this barrel on that day in good conditions on a mates paddock at 300 yards got its bum smacked by the LRPs. That is all i need to see. Not interested in theory, SDs or ESs. They never won a match, as Jacko often tells people.
To elaborate on this further so you know where this is coming from. You can place any clock in front of that muzzle. And i mean anything from $200 to $20,000 value. The SDs and ESs can be 0 (zero). The group will still be fucked. The reason? It is never about the numbers a bullet is doing, it is always about when the bullet leaves the barrel. The time delay between ignition and the bullets exit needs to be perfect. Its speed may vary but if it leaves at the same time, the group is accurate. If the velocity is perfect for each shot, but the exit varies, the group sucks. So it gets back to the base concept that without perfect pressure time curve, accuracy will elude you. Until some get their head around that it is about when the bullets leave as opposed to how fast, they may well continue to destroy barrel by chronograph.
This is where i believe the theory with SRPs in larger cases is flawed. I do not disbelieve the claims of smaller SDs etc, but given we know a barrel has a movement cycle during firing, i feel we need to see the time delay between firing pin strike and bullet exit. Not the exit speed. That is the easy way out and how often do we hear the stories about how it lies. I don't want to see data from it being done on a PPC or 6BR. I want to see it from a 260 Rem with H1000 and a 140 grain bullet. Real world, not selected world.

At some point i will try Re26 but feel it may be futile. Re26 would no doubt get higher velocity with both bullets but the case will most likely run out of volume long before it finds pressure. This will be with the LRP cases only. Winchester cases have a considerable capacity gain over Lapua so i may try them.

As a final note, everyone that knows me knows very well that as a competition caliber, i really really fucken detest any 6.5 cartridge. Some of the worst ever scores and groups seen on our range have been at the hands of a 6.5. Other than Pete Smiths Rogue and Old Trevs recent good results with the, hack spit, 6.5x47, i would have never tried a 260 for this test. I found it so good i will shoot it as a LG next season. Then we will see if that was a mistake

[justjeff]

Tony,

Shock, HORROR, you are shooting a 260 as a LG next year? Just as well I am emigrating south. Next you will be telling me you are using a .270 as a HG

Jeff

[Tony Z]

So I've been fucking with the 308 and 208 Amax's in the heavy gun. Every component from the start has been from same batch lot. The top group was shot on Saturday's session of confirming seating depth of the Amax's over 42.2 grains of 2208 and 205Ms.
Lower pic is from Sunday doing a final confirmation ten shot group of load and seating depth, stopping at six after seeing the group form.
Sunday's conditions were probably the best I've had during this test which is even more puzzling as a popped shot or a slinger could be put down to mirage or a sneaky switch in breeze. There is no way this occured here.
The pictures say it all and once again i have a very serious question mark over SRPs in larger capacity cases. Yet the same components used in the 175 SMK development showed nothing like this and were very predictable at last months 600 match. All that has changed since then is that it has gotten warmer.
If i were to take every shot fired from the start of the testing with varying powder charges and seating depths of the 208s and superimposed them, the 50 plus shot group combined is smaller than this 6 shot group. Actually it is just over half this size.
Knowing how stretcher tubes react during load development with them over many years, vertical stacking like that indicates a change in velocity. Given this is 200 yards, the velocity spread required to get that sort of spread would be quite considerable. There was no gradual rise in shots, the vertical was random. Oddly each case cycles through with no apparent change in bolt lift. No pressure signs anywhere. With some 175 loads left over from last months 600, the rifle put them into a hole. Confirming the gun et al is fine.

[Tony Z]

I did a basic primer comparison with the Palma cases to see whether the last sessions vertical was an isolated anomaly or a direct function of ignition. The CCI 450 shows a heap of vertical, more than any mirage on this day would have netted. Not surprising as it is not a match primer, just a hotter one that did show slightly heavier bolt lift in this test.
I also ran the newer 208 ELD Match as a comparison against the older 208 Amax i have run throughout this test. Same as a while back with the the 178 Amax versus the 178 ELD Match, there was a distinct accuracy deficiency.

[justjeff]

Hi Tony,

Hard to argue with the 205 load. Seems to me we have a few cartridges that need a '207' weight primer. The SR is not enough, the magnum or LR too much. Either that or change to a powder more accepting of one or other primers. I will be rechambering the 13 twist in the next week, we will see if it likes RE 26 with a 215 behind the 187 BIB.

Jeff

[Tony Z]

Jeff, the 205 group, while good even with the slinger on the right from a dingo fart, is still not anywhere near the group size of the 210 M in the regular large rifle cases.
This is odd as the 205s with the 175 SMK load is way better and more consistent than the 210 M load. The difference is about half a grain less powder which one would expect would be a better circumstance for the smaller primer.
At no time was there an urge to place a chrono under the barrel. The group matters to us, not numbers. I am convinced that a primer, large or small, is just another variable where neither, in this instance anyway, are the rule.
The 205s with the 175 SMKs have already shown great potential at 600 yards. I doubt the same can be said of the 205s and 208 Amax load, the vertical slots at 200 yards have a habit of becoming ladders at 600 yards. Big ladders as you know. Vertical slots always make me nervous.
I will shoot them at next months 600 to see if they can make a liar of me. The BC is worth it in a low powered 308. I am really tempted to run the 300 Rednex reamer in to see what some real horsepower could do. Anyone got any RWS 375 HH cases for sale? I sold all my good cases to some bloke now residing in Mehico

[justjeff]

Tony,

I have some virgin 300win mag RWS if you need them, also 50 new Saks in same if you want more case volume. Hard to go past the 340 Weatherby mod though, no pressure and heaps of velocity.

Jeff