Factory ammunition cratering?! (.338 LM)

[ringer706]

So I am still learning the ropes on cartridge loading, so maybe this isn't a big deal, but it seemed to jump out at me.

I went to the range today to sight in my new DTA SRS for the first time. This is a factory new gun and has not had any rounds through it. I bought a single box of Corbon .338 ammunition (300gr scenars on lapua brass, box labeled at 2800 FPS) and every single round showed a cratered primer. From the primer base to the top of the crater is about .010-.015". Should I be concerned? None of the rounds were difficult to remove from the chamber, and I don't see any other overpressure signs.

Also, I looked in my reloading manual and none of the max loads broke 2700 FPS for a 300gr bullet, so the box is labeled about 120 FPS OVER the best book max.

Thoughts? Could it being a new chamber cause exacerbate anything?

 

[ChrisGarrett]

Re: Factory ammunition cratering?! (.338 LM)

Sounds like your bolt's firing pin hole is a bit on the larger side and the primer cup is flowing under pressure, up and into the hole and around the pin's tip, which is one way we get cratered primers.

Chris

 

[Paladin2147]

Re: Factory ammunition cratering?! (.338 LM)

How was bolt lift?

 

[ringer706]

Re: Factory ammunition cratering?! (.338 LM)

Bolt lift was fine, no more force than when practicing with dummy rounds or when I cycled through a couple live ones with the firing pin pulled.

@ChrisGarrett... So if we were to assume that is the case, is there anything to be concerned about? Could the primers possibly rupture if there was a big enough gap?

 

[ChrisGarrett]

Re: Factory ammunition cratering?! (.338 LM)

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: ringer706</div><div class="ubbcode-body">Bolt lift was fine, no more force than when practicing with dummy rounds or when I cycled through a couple live ones with the firing pin pulled.

@ChrisGarrett... So if we were to assume that is the case, is there anything to be concerned about? Could the primers possibly rupture if there was a big enough gap? </div></div>

I wouldn't worry about it, but I'd like to see a picture of the primers just to make sure you don't have something totally freaky going on.

I know for the Rem M-700 bolts, you can get, or have installed, little bushings to shrink things down a bit, but ehhhh.

Fire away!

Chris

 

[ringer706]

Re: Factory ammunition cratering?! (.338 LM)

Here's a few of the cases from this afternoon. The crater rim seems to be thicker in width than most pictures I've seen. I'll let you be the judge.

 

[jr81452]

Re: Factory ammunition cratering?! (.338 LM)

ChrisGarret called it right. Pinhole in the bolt face is to large. An oversize pin or a bushing job would solve it, but it doesn't present any real problem the way it is. I don't see any high pressure signs.

 

[Fuzzball]

Re: Factory ammunition cratering?! (.338 LM)

@ChrisGarrett... "So if we were to assume that is the case, is there anything to be concerned about? Could the primers possibly rupture if there was a big enough gap?"

Suspect Chris is correct and, yes, it greatly increases the potential for a pierced/blanked primer. And, at best, that's not good for the bolt face.

I would return it to the dealer-maker, along with a few of those cases, and insist it be corrected while it's still new.

 

[MALLARD]

Re: Factory ammunition cratering?! (.338 LM)

+1 you can bush the pin , Greg Tannel is the guy to go to. but you'll never see any crater marks again , so you won't be able to read pressure signs from the primers.

 

[ChrisGarrett]

Re: Factory ammunition cratering?! (.338 LM)

Those are some of the most pronounced craters I've ever seen and I've looked at a lot of cratered primers.

As Fuzzball alludes too, that metal forming the crater's ridgeline has to come from somewhere in the primer cup and well, if it's flowing from someplace, that place can't be any stronger with less metal there, can it?

It is a 338LM, not a 223Rem, after all.

Like I and others have said, this is kind of a common problem, but when it's a bit less pronounced, we don't really worry about it too much.

Either get it plugged with a bushing, try to find a wider tipped firing pin, or just email a photo to the manufacturer and let them send you a new bolt, or fix it for you.

Chris

 

[ringer706]

Re: Factory ammunition cratering?! (.338 LM)

Thanks for all of the input guys!

I wound up calling desert tactical about it this morning, and as soon as I said I was having cratering with factory ammo, before I could even get it out, they asked if it was corbon. It turns out my bolt is already bushed and before they sent it back to me for unrelated service, the whole rifle was spec-checked so I don't think necessarily a rifle problem. I was told the firing pin diameter is only .003" undersized of the hole.

The guys at DTA told me that they've actually sent reps to corbon about their ammunition because they kept getting calls about it. From what he told me, the specific round I was shooting (300gr scenars @2800FPS) was about 7,000 PSI over maximum SAAMI spec. At this point, since I only bought the corbon to sight in the rifle and get a feel for it, I'm not going to worry. I will be starting a batch of hand loads soon, so if I don't see it any more, I'll let it go.

Thanks again for all of the input!

 

[ChrisGarrett]

Re: Factory ammunition cratering?! (.338 LM)

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: ringer706</div><div class="ubbcode-body">Thanks for all of the input guys!

I wound up calling desert tactical about it this morning, and as soon as I said I was having cratering with factory ammo, before I could even get it out, they asked if it was corbon. It turns out my bolt is already bushed and before they sent it back to me for unrelated service, the whole rifle was spec-checked so I don't think necessarily a rifle problem. I was told the firing pin diameter is only .003" undersized of the hole.

The guys at DTA told me that they've actually sent reps to corbon about their ammunition because they kept getting calls about it. From what he told me, the specific round I was shooting (300gr scenars @2800FPS) was about 7,000 PSI over maximum SAAMI spec. At this point, since I only bought the corbon to sight in the rifle and get a feel for it, I'm not going to worry. I will be starting a batch of hand loads soon, so if I don't see it any more, I'll let it go.

Thanks again for all of the input! </div></div>

Load some up and fire away. If the problem persists, you know that they're pulling a 'wall job' on you.

Chris

 

[Fuzzball]

Re: Factory ammunition cratering?! (.338 LM)

About 40 years ago I sent a new Weatherby Vangard .243 (along with three fired Remington cases) back for the same problem. They returned it with no change but included three fired Federal cases without a trace of cratering; letter said my bolt/pin "meets factory tolerences." I got some Federal primers and have never had another instance of cratering unless I change primers! I've seen the same thing occur with Springfield 1903A3 rifles. (Seems 'soft' Federal primers really aren't so soft!)

 

[InsidetheStorm]

Re: Factory ammunition cratering?! (.338 LM)

I saw the same thing on my brand new remington in 300 win mag. Exactly the same. I saw it on handloads firing a 200g SGK over 74.5g h-100 and a fed match primer. no where close to max. No heavy bolt lift, ect, ect. Thanks for the education, now I know it's not a big deal. If holes start showing up in primers, I guess I'll know I need to fix it.

 

[MALLARD]

Re: Factory ammunition cratering?! (.338 LM)

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: ringer706</div><div class="ubbcode-body"> It turns out my bolt is already bushed and before they sent it back to me for unrelated service, the whole rifle was spec-checked so I don't think necessarily a rifle problem. I was told the firing pin diameter is only .003" undersized of the hole.
</div></div>

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: ringer706</div><div class="ubbcode-body">The guys at DTA told me that they've actually sent reps to corbon about their ammunition because they kept getting calls about it. From what he told me, the specific round I was shooting (300gr scenars @2800FPS) was about 7,000 PSI over maximum SAAMI spec. </div></div>

...

i am not sure you read what i wrote. If the pin has been bushed you will not see any cratering. So, either your pin has not been bushed , or it was done poorly.

as i understand it you see no other signs of excessive pressure other then the cratered primers right ? does that make sense ? no , if you were 7000 psi overpressure you should see at least 1 other sign of overpressure. High MV , excessive recoil, casehead marks. I spent some time working up loads right along the max pressure and i will get several indications of excessive pressure before i actually reach my max pressure.

it is possible to have no signs of pressure and still have an overpressured load. But , something doesnt sound right to me. I love it when companies tell you it's someone else's fault.

 

[former naval person]

Re: Factory ammunition cratering?! (.338 LM)

Look at the face of your bolt with a magnifying glass. You should be able to see a circular bushing around the hole. If you can find someone(a machinist) with a set of pin gauges you can get him to measure the hole, and the firing pin with a micrometer. That will tell you if it is mismatched. By the way...Greg Tanner does the bushing and firing pin tip matching and returns the bolt within a week. Fine workmanship.

 

[leadbullet]

Re: Factory ammunition cratering?! (.338 LM)

all that work and worry about a primer you can't re-use anyway, the rifle shot fine there were no evidence of malfunction except an aesthetic primer condition that doesn't affect anything, let it go and shoot some more.

 

[Paladin2147]

Re: Factory ammunition cratering?! (.338 LM)

I think you got a gun problem - not a ammo problem. Other than the crater - the primers look fine.

 

[Fuzzball]

Re: Factory ammunition cratering?! (.338 LM)

"no evidence of malfunction except an aesthetic primer condition that doesn't affect anything,"

!!! That much cratering is bit more than aesthetics and it WILL affect things if one blanks.

 

[Jeffvn]

Re: Factory ammunition cratering?! (.338 LM)

+1 on Gre-Tan (Greg Tannel) doing a kick ass bushing job and turning it fast.

http://www.gretanrifles.com/

And that is some of the worst cratering I've seen. If that represents someone's idea of "bushing" a bolt, I certainly don't want them working on my gear.

Jeffvn

 

[jaminen]

Don't know if you solved your problem but we have 5 of them and 3 of them have bolts in which the bushing used for the firing pin hole began pushing back and this caused factory ammo to blow primers, and in one case caused (the overpressure) the extractor to blow out of the gun (lucky i wasn't shooting supoprt side!). The factory hasn't been good at all about the problem... offering us "credit" towards new bolts instead of fixing the problem. These are Gen 1 bolts FYI - they have since been redesigned... supposedly for manufacturing ease and not related to our issues (although the changes have addressed the cause of our bolts failing - I'm sure by accident).

.308 SRS FYI w/ from 443 to 822 rounds at failure.

Good luck.

 

[.50 Cal Cow]

About 40 years ago I sent a new Weatherby Vangard .243 (along with three fired Remington cases) back for the same problem. They returned it with no change but included three fired Federal cases without a trace of cratering; letter said my bolt/pin "meets factory tolerences." I got some Federal primers and have never had another instance of cratering unless I change primers! I've seen the same thing occur with Springfield 1903A3 rifles. (Seems 'soft' Federal primers really aren't so soft!)

Funny that would be the opposite of my 300WM Rem700. I started with Federal primers and ended up with similar results as the pictures above. I have since switched to CCI250's and the problem while not totally gone is so much less pronounced I don't worry about it anymore. I'm hoping the Tula's I just bought are as hard as the CCI's since I haven't found CCI's anywhere for the past 3 month's.

To the OP maybe once you start to reload just factor primer brand into the equation and see if that helps the problem like it seems to have with my 700.