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My Stag 10 build and an interesting issue...


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Hey everyone, I'm new here on the forum. I've posted a few odds and ends around the site. But I thought I would post up an issue I had recently with my 308 build. I have gotten tons of great info from here over the years just from people posting similar issues to what I was having. So I figured I would contribute one.

Fair warning, I do tend to ramble on and on and on sometimes. I do try to break it up into paragraphs at least and use the best grammar and punctuation that my WV public school education can afford me. So... Apologies if the thread gets unbearably long.

Here's a breakdown of my rifle. It is a home build and one I researched a lot prior to building:

- Stag 10 Receiver Set. 

- Seekins SP10 Barrel, 1:11.25, 5R, 18", Intermediate Gas System, Smith Vortex. (Rock Creek Button Blank).

- Toolcraft Nitride Carrier, JP Bolt (NiB).

- RRA 2 Stage Chrome NM Trigger.

- Troy Carbon Fiber 15" M-Lok HG.

- Magpul UBR, running standard small frame carbine length H2 Buffer. (UBR = A5 Length Buffer Tube with Spacer Removed).

- Seekins Adjustable Gas Block.

That pretty much sums up the build. I run either Magpul or ASC mags. It mostly consumes the following ammo:

- Federal Gold Medal Match: 185gr Juggernauts. (Best Groups)

- Federal Gold Medal Match: 175gr SMK.

- PPU 168gr Match.

- IMI 147gr FMJ. (Plinking Ammo)

- Handload: 168gr ELD over 39.5gr H4895, LC Brass, Federal 210 Primer.

From day one, this rifle has ran flawlessly, I've recorded 426 rounds so far of all the above ammo mixed. I originally had a BCM PNT Trigger in this rifle for the first 420 rounds. I replaced the PNT Trigger a little while back with the RRA 2 Stage. When I did this, I also swapped in a bit lighter hammer spring.

So I take my rifle out to shoot, try out the new RRA trigger. I had dry fired it over 100 times prior to this and everything was properly lubed and ready to roll. I hit the ground (prone), lined up behind the rifle and started firing a 5 round group at 100yds. Ammo being used was the (cheap) PPU 168gr Match. I figured since its a new trigger and I'm just function testing, just shoot the PPU until I have confirmed everything is running properly.

I fire 3 shots, on shot number 4 I get a "click"... So I stop and run the charging handle, a live round ejects. I look it over and there isn't so much as a mark on the primer. So I go check put the brass from the previous 3 shots and one of them had a pierced primer. I pulled the bolt carrier group and found that a tiny "cup" had been punched out of the PPU primer and had stuck on the tip if my JP firing pin. This is turn jammed the firing pin back into the bolt face and wouldn't allow it to protrude.

So I cleared everything, and thought maybe it was a fluke? Soft PPU primer? I got down and tried one more time. Shot#1 fired and cycled fine, shot #2: "click" FTF again... At this point I assumed it was the trigger since its the only thing that had changed. This rifle normally eats any of the ammo I listed above, including 80rds of the PPU, prior to the trigger upgrade without a single issue. No cratering on the primers either, the JP has a smaller firing pin tip and tighter opening in the bolt face. Which is one of the reasons I'm running it.

So... at that point I pack my 308 in for the day. My thought was, lighter hammer spring and possibly lighter hammer on the RRA 2 Stage? I ordered a couple heavy hammer springs, installed the spring and tuned the RRA disconnector (polished the surfaces) so it would reset a little more crisply. The heavier hammer spring made the RRA reset a little sluggish at first. Many dry firings and a little light polishing the contact surfaces and its resetting perfectly. The heavy hammer spring didn't affect pull weight much if any. It did give the first stage a little different feel, but still a nice trigger pull.

I'm going to give it whirl this weekend and see if that heavy hammer spring solves my pierced primer issues. That was my thought anyways seeing as the trigger was the only change made. A lighter hammer spring not applying sufficient force on the firing pin would allow this to happen was my thought on it. I suppose it could possibly be unlocking a bit too soon also? Gas is adjusted right on the money, not running hot or anything. Brass is being ejected to 3-4 O'clock with all ammo listed.

Thanks for reading my gigantic post. I like to try to be thorough and thought maybe some of you guys have seen this before?...


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1 hour ago, shooterrex said:

If the problem keeps happening replace the trigger with the old one. If that clears it up it's the new trigger group.

Thats my back up plan. I have the PNT Trigger in another lower so swapping it back would be no big deal...

Hopefully I'll be able to get out tomorrow and test it out. 

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Finally got a free minute to update...

I tested out the new hammer spring on the RRA trigger Sunday. Everything functioned perfectly, no FTFs and no pierced primers. So looks like the light hammer spring was the culprit.

I have a Rem 700 I'm in the middle of building right now. After I get it all sorted I'll be back to finding a decent optic for my Stag 10. I haven't gotten into high end optics yet, just hasn't been a priority yet. I am running an old Simmons 2-10x on it just as a basic hunting scope. It is reliable so it's better than irons I suppose.

I am excited to see how this rifle does out to 600yds. That's basically the limit of what I built it for. It really loves FGMM 185gr Juggernauts which should be a good bullet in 308 for the wind. My DA is low where I live, 800'-1100' ASL on average so I need every advantage I can get. 

I'm really liking the looks of the Arken 4-14x: 


 It has a lot of features I'm looking for and the price is pretty good. Still about 4-6 week lead time, they are pretty new. I already have a Sig Alpha 2 30mm 20MOA one piece mount for whatever glass I end up with. I'm hoping this will get me out to 600yds and be a tough scope. My rifles get a lot of use. I shoot a lot of inclined shots so a cosine indicator may be in store for it after I get glass for it.20200322_155740.thumb.jpg.b981460d4be373fb3540504a65d77434.jpg

Edited by Lowlander
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