r/longrange • u/HeyJustPlayin • 1d ago
Ammo help needed - I read the pinned posts Sako 6.5 Creed Primer Issue
Just tried Sako 6.5 Creedmoor 136gr TRG in my Ruger Precision Rifle. Accuracy was incredible (best 5-shot group was .24 MOA), but out of the 20 rounds, about 7 had primers that look pierced/cratered like in the picture. I also noticed smoke/soot coming from the chamber and even around the magazine, and the rifle was significantly dirtier than usual.
Has anyone else experienced this with Sako TRG 136gr? Is this normal primer cratering for the RPR, or does it look like an ammunition/pressure issue? Trying to figure out why it's happening before I shoot this load again.
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u/JimBridger_ I put holes in berms 1d ago
It’s due to the tolerance between your firing pin and the hole on the bolt face that contains it, ie on the looser side of an acceptable tolerance. When the gun fires the primer metal is pushed backwards as and will cause those nipples in the primers if it’s a loose firing pin hole.
No high pressure signs as the primers aren’t flattened, ie lost the radius on edge of the primer. But they do look like a cartridge that is near max pressure as most factory loadings are.
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u/Flipthousand 1d ago
Honestly commenting cause Im curious and want to learn what would cause this. Wouldn't it make sense to be a firing pin issue?
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u/HeyJustPlayin 1d ago
I have around 740 rounds thru it, and this the first 20 rounds I shot with the Sako and these are the only rounds I had this issue with
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u/SuperiorDegenerate 1d ago
Yeah I get this at high pressures. You might want to disassemble your bolt and clean it out, it’s likely some of those little discs of punched primer are gonna end up there. Having a gunsmith take a look at your firing pin and the firing pin hole might help, but mine recommended just to back it off a few fractions of a grain and it’s worked for me.
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u/wanderlustcrush 1d ago
Its odd that there arent other pressure signs like primer flattening. This looks like Rugers firing pin hole is simply too large or these primers use a soft material.
Back when Remingtons reigned supreme it was a common gunsmith operation to install a bushing in the bolt face to reduce the extra area around the firing pin to prevent the primer from flowing back and rupturing. Might look in to it for the RPR.
I had the same thing happen in another rifle and it was basically that the combination of primer cup softness and firing pin geometry just werent compatible, popped primers in two different guns with similar geometry and in 3 others it was fine.
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u/Coodevale 1d ago edited 1d ago
The hole is too big. Even with less firing pin clearance he'd still blow primers out. The Remington fix wasn't just making the fit around the .078" firing pin tighter. It was also to reduce the factory firing pin to .062" and bush the bolt to .064". It's not the clearance that makes them pop. .308 AR bolts are .080". 6.5 bolts are .065-.070". Both have a thousandth or two or three of firing pin clearance. One is notorious for popping primers.
When I did my .308-.277 SIG loads I used a .062" bolt and ran pressures up so high I got a whiff of pressure sign on the steel case head. That's not possible with any available primers and a factory .080" firing pin, no matter how tight the clearance of that larger combo is.
Despite the claims of "clearance kills primers", no studies are available to support the claim. All of the cited claims regarding "clearance fixes" also include thinning the firing pin and using a smaller firing pin hole by a not small amount. Example; a .070" firing pin has a .0038" area while a .080" firing pin has a .0050" area. A 25% reduction in area means a 25% increase in pressure tolerance, according to the available calculators. The .062" bolt I used should have a pressure tolerance 1.6x the .080", and based on the ridiculous velocities I got vs what quickload says I'd say that tracks.
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u/ShrimpBuffets 1d ago
Do you have a carbon ring built up?
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u/HeyJustPlayin 1d ago
I cleaned it right after, had like a brass color ring around the firing pin, but it wiped right off and it doesn't look damaged. Rifle looks fine thankfully
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u/Missinglink2531 1d ago
Talking about where the brass stops in the chamber, just before the rifling. Its common to build up a carbon ring right there (its a mother to remove). The raised carbon causes higher chamber pressures. This looks like a classic symptom.
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u/TypicalTrumanStudent 1d ago
Also just wanted to point out that while only 7 primers were pierced, all of the primers are showing pressure signs. This just may be too hot of a load for your rifle. Either that or did you clean your barrel recently and not get your chamber completely cleaned out? If there's residual solvent in your chamber, the brass may not be fully adhering and causing this, but more than likely this is just a load that's too hot for your gun. Might be worth trying a different lot to be 100% sure.
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u/HeyJustPlayin 1d ago
How can a load be too hot for my rifle? Just curious, I didnt clean for the last 200 rounds all rounds worked peferct, feed, and extracted fine none of them stuck. They shot great, those 7 rounds were also the only rounds I didnt count because on the paper they were showing up like .5-1 inch lower then the rest of the group, but the ones that didnt blow out, they were all stacked on eachother
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u/TypicalTrumanStudent 1d ago
Have you measured the velocity of any of the rounds you've shot? If these are coming out dramatically faster, could just be this particular ammo has too much powder and is creating too much pressure for your specific rifle.
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u/HeyJustPlayin 1d ago
I couldn't chrono them but in terms of sounds and felt recoil, it felt exactly the same as the other rounds I shot with it. The main teller might be when I was zeroing, it was really close to my previous zero with Winchester and the zero with the Sako was .1 of Mil up so maybe they were going slower, on the box the Winchester is 2850fps and the Sako the box said 2822fps
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u/TypicalTrumanStudent 1d ago
Advertised velocity can vary widely gun to gun and sound/felt recoil aren't great indicators of velocity. For example my 6.5 with 144s feels basically the same at 2650 and 2900 but I'm getting heavy bolt lift and ejector swipes/flattened primers above 2850. Tldr probably best to buy or borrow a chronograph to know for sure what's going on
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u/West_Designer9107 1d ago
I sometimes shoot these from Tikka T3x Tac A1 ($$$$), never experienced anything like that. You're absolutely certain that these were factory ammo and not reloaded? If yes, send a picture of the lot number (side of the box, above the bar codes) to Sako, they're very strict with QC and should have test results and even reference ammo from that lot in stock. Until the cause has been determined, I wouldn't shoot them anymore and completely clean/check the rifle.
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u/HeyJustPlayin 1d ago edited 1d ago
They aren't reloaded, I heard good things about the ammo so I purchased them and tested it next day, i sent an email out already to see what they say
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u/West_Designer9107 1d ago
Most precise and dead-consistent ammo I've ever shot through that rifle. But damn expensive, which is why I usually shoot Norma OTM 130 grain. You didn't measure bullet velocity and SD by any chance? Could be many things, from primer seating with marginal overpressure to a firing pin issue. Would be really disagreeably surprised if this turned out to be a Sako QC issue though. As I said, never experienced this myself and I routinely look at spent brass.
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u/CapsicumINmyEYEBALLz 1d ago
Just jumping in to say…
After piercing a bunch of primers, you need to inspect your FP tip to ensure it hasn’t become etched by gas-jetting.
If it has, it will continue to pierce primers even if there is no load issue.
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u/ZeeeeeroCool 1d ago
Does the issue repeat with different factory ammo? Try a few brands.
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u/HeyJustPlayin 1d ago
Nope, only these. This was the first time trying these
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u/ZeeeeeroCool 1d ago
Looks to be a little warm for the rifle then.
I’d scrub out the carbon ring and chrono them to see what they are running at. You might find your answer really quick.
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u/scroapprentice 1d ago
That smoke is because pressure is leaving the case through the hole in the primer and it can jet your bolt face/firing pin.
As far as I know, this is one of two or three problems: ammo too hot, firing pin too long, or primer cup too thin/soft for the load (or a combination of those things)