308 Win LRPs v SRPs

[Brad Y]

Interesting topic. Basically my experience:

Small rifle primer and slow powder is not real productive unless there is some pressure there to help encourage a good ignition and burn. However lighter 155 class are doing well with 8208 and srp. Obviously faster powder easier to spark up. Choice of primers goes down to what ever works best. I prefer the safety of the 450 and the thicker cups however recent lots of them have chronied slower than br4 or 205m. Maybe upping 0.2-0.5gr powder will get the slower primers working again. One thing with the 205m is in real cold mornings they seem to go off the boil and ignition problems occur. 450’s not so much. More testing will happen here and again this was with 2208. The 200gr Berger’s don’t seem to have an issue with ignition but will research it more. Large primer loads definitely don’t have the ignition problems the small primers get and you can probably run 155’s to 185’s very reliably on 2206h or 2208 with them. But for 200gr loads I haven’t gone there yet fearing the less brass around the case head won’t fare well and pockets will get loose quickly. I’m able to get 200’s over 2700 in a tikka action with a 30 inch barrel and primer pocket life with srp is pretty good. But I’m not going there with large primer cases. Maybe a lower node in lrp will be safer for those cold mornings if small primers seem to show the effect of cold temps with slow powders. I reckon ammo 12hrs in the freezer then shot over a chrony will show if I need to make a cold load up. In terms of brass strength, it’s definitely worth using the srp brass and tuning a load if it holds good vertical.

[trevort]

I've just formed some 6slr from 308 lapua and I just bought 99 SLR cases from Kickin that he formed from palma cases.

They will be firing 87gn bergers at fallow deer over re16.

Interested to see what happens!

[Brad Y]

I reckon large will be more consistent. That powder is getting slow for a small primer.

[trevort]

Brad initial testing was very limited but 42.3 gns was not max and will be a good start point


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[mick_762]

Brad initial testing was very limited but 42.3 gns was not max and will be a good start point


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Will be interesting to see where your final pressure point with SRP brass is Trev, as you have seen, the same reamer has given no pressure signs at 42.6gn with LRP Norma reformed brass.

[Tony Z]

This weekend gone i was out chasing hogs and other vermin. My 6x47 runs two loads, one with 75 Vmax, the other with 87 Vmax. Both with Re15 and CCI 400s. Both loads print over the top of each other at a 100 yards and both do under half inch for five shots. Last weekend on the Sunday i was sighting in a new barrel on another rifle and had the 6x47 there for any stray crows about. Anyway i decided to check both 6x47 loads out at the 100 yard target. The day was one of the coldest up here for over a hundred years they said, about 13 degrees. On the scopes Zero setting both loads hit their POI but with a lot of vertical, about 3/4" of vertical. Three shot groups stacked vertically for both loads.
Now anyone who claims it may be the Re15 should think on this. I went from high 20s to to low 30s C here to Narromine in the mid teens C a few years ago with the same batch lot of Re15 and won the LG group agg. If it is powder temperature sensitivity, it would have shown up then, and it didn't. The load in the 6BR was 30.2 grains of Re 15, 103 CHs and the same CCI 400s. A couple of years ago i went to Narromine, this time with the 636, 34.5 grains of again the same batch lot of Re 15 and CCI 450s. Again from one extreme temperature to another and had no issues with vertical at the 600.
It would appear that Tubb was right in my view, once you exceed 35 grains of powder using the SRPs, there is a possibility that under certain conditions you may have ignition issues. Some of which i saw when attempting to use this cartridge at 1 K.
Now it could be said a CCI 450 could solve the issue in my 6x47. That may be true if i could get it to group with that primer. It's OK with that primer but it is far better with the milder 400s.

Just to add, it is under some misconception that Lapua did extensive testing to establish that the SRP was the best primer for the 6.5 x 47 case. While that may be true INSIDE A TEST FACILITY, it is in another world outside of it. The point being i remember it being clearly stated by one of the US importers that they insisted on the SRP in this case. A short range BR shooter that like so many of them think PPC is good, so the recipe is good for everything else. Try applying that recipe to a 50 BMG. There are far too many instances of poor ignition with the SRP in the 6.5 x 47 case across US forums for it to be shooter error.
Where some of this started is way back in the 80s with Remington SRPs in 308 cases. This carried on with one slight flaw. The majority of shooters using this case were those converting them back to 308 x 1.5" for Hunterclass etc. The forerunner of the 30BR using under 35 grain loads of the fast burning IMR 4198 with 110 to 125 grain somethings. From there the legend grew.

[Brad Y]

I believe that there is a point where the SRP becomes inconsistent with ignition. However I think there are factors such as powder burn rate, full pressure curve and yes the amount of energy the primer puts out are factors.

Some recent batches of 450’s have tested similar velocities to 205’s and BR4’s have shown to be warmer. And powders differ each batch too.

My general starting point is 2208 in 308 with 200gr bullets and cci450’s but I’m going to do the work with 2206h in my current barrel again. My theory is that in the cooler weather over winter it might promote better ignition.

[Glenn]

I run 67 Copperheads over 40.0grs of RE15 in my 6x47Lap with a Fed match primer.
Speed is 3800+!
I used 40.0grs 2208 for years before I went to Reloader.

I have had my 6x47lap for 11 years!
I have shot in the high 30's and sub zero temperatures and have NEVER had one ignition issue, EVER!!!

I'm not a target shooter so I have never used heavy projectiles.

I am a hunter who fires around a 1000+ shot a year and the 6x47Lap with lighter projectiles makes
a spectacular Varmint gun!

Glenn

[Tony Z]

Gooday Glenn. You have just reminded me to give you a call.

I fully agree, the 6x47 makes for a great varmint cartridge.
The pic below shows the two groups, 75s on the left, 87s on the right. The POI is right on for the majority and is in keeping with when it was zeroed quite a ways back apart from a little left drift on the second group from a slight breeze.

[Brad Y]

Here’s something interesting I found online.

https://youtu.be/bil4iiSqGXU

[Tony Z]

Glad you posted that up Brad. I didn't because the links take you to the Creedmoor tests he did. That is way more scary, especially part 3.

[trevort]

I tried the slr cases formed from Palma brass at the weekend. These had been fired before so we’re already sharp shouldered slr cases.
It’s a killing things rifle with 200m likely the maximum range so three shot groups are all I fired and the load of 42.6 gn re16 appeared mild and accurate enough or my use.
I also had cases I’d just formed from standard lap 308 cases. Tough bolt lift at 42.3 gns ( which is where I started). I suspect that the case capacity will increase after fireforming to the slr so I will use a milder fireforming load on them and compare again when done


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[Brad Y]

Glad you posted that up Brad. I didn't because the links take you to the Creedmoor tests he did. That is way more scary, especially part 3.

Possibly worthy of some investigation. I’m not going to attempt to make my gun hang fire though. I’ve done some work on ignition in my gun and have found that of the common sr primers the cci450 isn’t as hot as I thought! It still groups but just in primer change I’ve cut my ES by a huge amount. Going to do more work on it this weekend and hopefully be able to play with the tuner at 400m Sunday before a 1kBR session in the arvo.

[Tony Z]

Brad i found the pressures dropped considerably when using 450's. Not always the best grouping out of them, more often the worst and as for ES, i wouldn't have a clue as i never use a chrono for load development and only for velocity confirmation at a later time.

You're right about those hangfires. The last hangfire i had, and only one i've had, half of the scope landed in the range car park after it went through the tin roof, the other half hit around the 50 meter mark and the barrel came out of the action and dropped on the bench intact. The right side of the stock was never found. I still have the barrel but the action was sent for display to Stuart Elliott and from there it is unknown. The load was a full case of 2214, now long discontinued, in a modified 7mm Rem Mag firing a 168 SMK. The first 3 shots went into an inch at 500 meters, the fourth is yet to terminate. There was no sign of a hangfire on the first shots. The primers were Fed 215Ms. The powder charge was 100% load density where through previous load development i found that you could not fit enough 2214 into the case to cause any pressure signs under normal conditions. To this day i have no idea as to why that rifle came apart but i clearly remember the click, wait for it, kaboom.

I always say, hangfires are a millisecond away from becoming a grenade. There was an instance that Jeff can elaborate on where a 300 RUM AI was doing some serious hangfire stuff. I think after the third Jeff pulled the shooter off the firing line and told him to go home and dismantle that load. A case full of 2225 and BR2s. He returned at another time with 215s and there were no issues. Actually he shot a sub inch group at that 600 yard match.

I cannot believe that johnny goes looking for hangfires.

[justjeff]

Brad,

The really scary thing about the situation TZ is talking about. Some rounds didn't go off, just 'click'. After we dug our way back out of our instant slit trench, we pulled one apart. There was a normal looking layer of powder, underneath this was a fused mass, which had obviously got hot enough to melt together, but not to ignite. This was a good example of when not to listen to a now retired gunsmith in Townsville, who advised the shooter to use the softest LR primer on the market, to ignite 110gr of 2225.

Kept me busy as RO for a little while, and probably the closest I've ever come to seeing a firearm incident.

Jeff