MichalS Posted August 2, 2019 Report Share Posted August 2, 2019 Today I tested my first 6.5CM loads with 139gr Scenar in Stag 10 AR, Hornady LRP brass (S&B primer). I prepared 25 cartridges, starting at 41.5gr and finishing at 43.5gr every 0.5gr to plot the velocity. COAL 2.80". According to RS load data max load in this combination is 44.8gr RS62, so I thought I was conservative. First 4 shots @41.5gr were fine, with MV in the 795-800m/s. On the fith shot with the same velocity the primer pierced. MV was 794m/s and the shot actually went inside the earlier group... Was it a defective primer? Shall I ignore it and continue? Michal Quote Link to comment Share on other sites More sharing options...
phoenix Posted August 2, 2019 Report Share Posted August 2, 2019 A friend had this problem with a Bergara B14BMP. in 6.5 CM It happened with several different types of primer including Murom and others I don't remember There was a problem with the firing pin which involved sending the rifle back and getting the firing pin replaced Cheers Bruce Quote Link to comment Share on other sites More sharing options...
Re-Pete Posted August 2, 2019 Report Share Posted August 2, 2019 Have a look at the firing pin tip with a magnifying glass.........if it's a smooth dome with no sharp protrusions, chances are you had a dud primer. The strikes actually look quite light from your photo's. Pete Quote Link to comment Share on other sites More sharing options...
MichalS Posted August 3, 2019 Author Report Share Posted August 3, 2019 Firing pin seems to be OK. Would You fire the next loads? Quote Link to comment Share on other sites More sharing options...
TJC Posted August 3, 2019 Report Share Posted August 3, 2019 Run your finger over the other primers. If any are sharpish to the touch then it probably confirms the load is too hot. Quote Link to comment Share on other sites More sharing options...
ray Posted August 3, 2019 Report Share Posted August 3, 2019 I see swipe marks clearly on 3 cases, shavings on the bolt face. I have found the s&p lrp to crater much easier than cci 200s. Either way your overpressure Quote Link to comment Share on other sites More sharing options...
No i deer Posted August 3, 2019 Report Share Posted August 3, 2019 You need a magnum primer with a thicker cup Quote Link to comment Share on other sites More sharing options...
phaedra1106uk Posted August 3, 2019 Report Share Posted August 3, 2019 Friend just had his Begara B14-BMP returned for piercing primers, not a hot load being used, 35.5gr of N150 with a 139gr Scenar. He was told the distributor had "done something to the bolt face and firing pin". Took it out last Sunday and got another pierced primer in the first 10 rounds. Rifle is going back. Quote Link to comment Share on other sites More sharing options...
Re-Pete Posted August 3, 2019 Report Share Posted August 3, 2019 It may be a reflection in the photo, but there's a mark on the tip that looks as though it might be chipped,which could cause piercing. It would also be a good idea to measure the protrusion. Should be around 1.6mm. Pete Quote Link to comment Share on other sites More sharing options...
MichalS Posted August 3, 2019 Author Report Share Posted August 3, 2019 It seems the S&B primers are the weak link. I repeated the experiment today and again got cratering and a pierced primer, this time @42.5gr RS62. I did another set with the same load (41.5-43gr RS62), 140gr Berger LRBT and Federal GM primers and was able to get ~835m/s @43.0gr (~2750fps) with no pressure signs. Groups were awful though. Got good grouping with 139 Scenar @42.0gr/805m/s (0.35MOA), I will push it further with GM primer. Edit: On closer inspection there is a bit of cratering @43.0gr (nearest row). Quote Link to comment Share on other sites More sharing options...
Re-Pete Posted August 3, 2019 Report Share Posted August 3, 2019 There are bright circular wipe marks on the case heads that typically occur when the brass is extruding into the ejector hole, ie pressure on the high side................ Pete Quote Link to comment Share on other sites More sharing options...
One on top of two Posted August 3, 2019 Report Share Posted August 3, 2019 If your using LRP 42 grains will be about max , SRP will be around 44 - ish if I’m using SRP I use 41.5 .. RS 62 is too temp sensitive to run at max loads especially with LRP . Quote Link to comment Share on other sites More sharing options...
No i deer Posted August 3, 2019 Report Share Posted August 3, 2019 Shiney spots on the base = a hot load, that surprises me as I tried 42grs in my 6.5x47 and I didn't have any pressure signs I just felt it was harsher than I expected, dropped it back 0.5grs and it felt better and shot like a laser at 600yds. I thought the creedmoor had more powder room so I'm surprised your getting pressure signs at 42grs. Quote Link to comment Share on other sites More sharing options...
No i deer Posted August 3, 2019 Report Share Posted August 3, 2019 I missed that it was LRP brass not SRP brass 🤔. 2 extra grains of powder if you use the SRP 🤔. What velocity from 44grs of RS62 pushing a 139gr scenar...? Quote Link to comment Share on other sites More sharing options...
One on top of two Posted August 3, 2019 Report Share Posted August 3, 2019 I will get 2700 avg with 44 grains of RS 62 with SRP and 2700 avg with 41.6 grains of RS62 with LRP both of the above using 139 scenar Quote Link to comment Share on other sites More sharing options...
One on top of two Posted August 3, 2019 Report Share Posted August 3, 2019 This today was using 41 grains of Norma 204 with Peterson LRP and 139 scenar Quote Link to comment Share on other sites More sharing options...
One on top of two Posted August 3, 2019 Report Share Posted August 3, 2019 . Quote Link to comment Share on other sites More sharing options...
GT3_richy Posted August 3, 2019 Report Share Posted August 3, 2019 This is a semi-auto gas gun, right? Quote Link to comment Share on other sites More sharing options...
MichalS Posted August 3, 2019 Author Report Share Posted August 3, 2019 Yes, semi auto gas gun (AR 10). RS load data gives 44.8gr (sic!) as the max load for 140's with LR primer in Hornady brass... Quote Link to comment Share on other sites More sharing options...
No i deer Posted August 4, 2019 Report Share Posted August 4, 2019 14 hours ago, One on top of two said: This today was using 41 grains of Norma 204 with Peterson LRP and 139 scenar So why go with the creedmoor when the 6.5x47 out performs it.... Quote Link to comment Share on other sites More sharing options...
dodgyrog Posted August 4, 2019 Report Share Posted August 4, 2019 1 hour ago, No i deer said: So why go with the creedmoor when the 6.5x47 out performs it.... Fad? Flavour of the month? Quote Link to comment Share on other sites More sharing options...
One on top of two Posted August 4, 2019 Report Share Posted August 4, 2019 Hahaha 👍 I’m just working up loads of 204 at the min. This is just a starting point really Quote Link to comment Share on other sites More sharing options...
No i deer Posted August 4, 2019 Report Share Posted August 4, 2019 😴😉😁🐌😂😆 Quote Link to comment Share on other sites More sharing options...
GT3_richy Posted August 4, 2019 Report Share Posted August 4, 2019 7 hours ago, dodgyrog said: Fad? Flavour of the month? 10 year+ fad/fotm? Bare in mind this isnt a bolt gun. I know nothing of ARs short of reading bits here and there but things like excess gas pressure can cause ejector marks I believe, likewise headspace/chamber issues can twonk primers. Quote Link to comment Share on other sites More sharing options...
No i deer Posted August 4, 2019 Report Share Posted August 4, 2019 Just get a bolt gun 😉 One of today's test 5 shot groups with my 7mm saum with 184gr hybrids 💋💋😉 Quote Link to comment Share on other sites More sharing options...
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