Bolt Face

[AzDak42]

So....

A few weeks back I noticed that my 7mm-08 48 was leaving a weird impression on the primer. It's was a full circular indent around the firing pin dent. Upon inspection of the bolt face, I noticed that their was a ring around the firing pin hole that looked like it was a raised area around the firing pin corresponding to the ring on the primer. I gave a call to Nosler and shipped my rifle back to have them take a look. I heard back that they had smoothed the bolt face and had sent it off to refinish.

Fast forward a few weeks and I have it back in hand. They sent along a handful of fired brass showing no ring around the primer. The extractor is bright and shiny and it looks like it the bolt was refinished. But.. after their test firing, durned if the bolt face doesn't have a ring around it where the finish is now uneven. (Just to be sure, I cleaned up the bolt face with a q tip and some hoppes, and sure enough, I can feel the indent with my fingernail.)

Thinking maybe I'm nuts, I pulled the bolt on my 48 in 35 Whelen and cleaned up that bolt face with the same qtip and hoppes. Most of the finish looks to have been warn away. (The nosler is probably less than 50 rounds, and the 7mm08 is about the same.)

Am I off my nut? Given the pressure the bolt face has slaming back into it, it's probably not surprising that the finish goes away quickly. Is this normal? Can anyone else check their boltface and see what there is to see?

Here's some pics.. thought they might help..

 

[IdahoCTD]

Are the primers seated deep enough in the cases you fired? If not it will rub the bolt face when the bolt is closed. This rubbing could case the coating to wear thin. Usually it's a circle out around the edge of the primer where it rubs when not seated deep enough.

 

[AzDak42]

Are the primers seated deep enough in the cases you fired? If not it will rub the bolt face when the bolt is closed. This rubbing could case the coating to wear thin. Usually it's a circle out around the edge of the primer where it rubs when not seated deep enough.

Well.. The primer indentation happened 1/2 way through the first box of factory loads. (10 rounds or so.) I ran them over a straight edge and all were below the level of the brass. On my handloads, I uniform the pockets on all my brass before putting in the primer, and seat it using the Hornady single stage press primer.. I also QA each round with a straight edge to make sure.

So I'm thinking not the issue. But I'll go double check.

edit: even better, I found a pic I took of the first box of ammo:

 

[IdahoCTD]

The picture from before definitely was a manufacturing issue. The second picture of the bolt just looks to be a poor finish. It does look like your getting pretty light primer strikes (it's hard to tell for sure from the picture). Have you compared the brass before and after firing? Maybe it's a head space issue now that the bolt surface was recut. Typically the difference between a go gauge and a no go gauge is only .003". That raised surface could have easily been .001 to .002 (even more if the base surface was touched when it was cut). So depending on where the head space was set and weather or not it was rechecked when you sent it in it could be excessive now. That would explain the light primer strikes and the primers backing out upon firing.

 

[AzDak42]

Well.. back she goes.

 

[AzDak42]

After a week delay from my being on vacation, my 7mm-08 showed up on Friday. Unfortunately, they can't resolve the finish on the bolt face wearing off. They tried a few different coatings, and it continued to flake. They are comfortable it won't affect function and that the bolt face is smooth.

I'll take it to the range and see if with another 20-40 rounds we have any more cratering on the primers.

Does make me wonder how this works on other bolt faces on other guns though...

 

[killdeernow]

The real question is: how does it shoot? If you're getting sub MOA and the brass is "normal" let 'er fly. If however, your primer pocket is loose and you’re showing signs of pressure, that's a different issue.

I find this post interesting. Interesting enough I had to go out and check my Win M70 in 30-06. I noticed the Win M70 has no finish on the bolt face. Just bare metal. I just checked some fired cases and noticed nothing but a perfect indentation in the primer.

Looking at the pics my conclusion is it has to w/the micro finish Nosler applies to weather proof it. I like the fact that you showed Winchester and Hornady brass. That rules out any manufacturing issues with the cartridge (although statistical confidence would come from 3 different manufacturers) unless you are reloading which you stated you weren’t.

I'm surprised Nosler sent it back looking like that. I found in the past that they had great customer service. My point is, I thought they'd give you something that had a new, polished, freshly coated, squared and lapped with a smooth face that wreaked quality...

Not the case here by looking at the “after” pic. Again, I’m surprised.

That’s good to know. Keep us posted on the performance.

 

[AzDak42]

A day off work meant I had some time at the range to see how it was going to behave after coming home from it's repeat trip to Nosler.

I started off with some Nosler factory 140g Accubonds as a baseline to see how it would shoot. I was a bit nervous as I had the first 5 shot group that came in around 3". Looking at it though, I believe the majority of the variation was from the first two cold bore shots. Things started to tighten up after that.

I had a batch of hand loaded 120g Btips over Varget.

The first group looked like this @41g:

You might notice that's only 4 shots... the missing bullet hole was off the paper by about 8". Somebody touched off a 300 RUM with a muzzle break on the bench next to me as I was in mid squeeze. I'm just thankful I didn't have to run home and change pants.

The 42g & 43g loadings were not as accurate, but both were in the 1.5" range. Then with a fairly hot barrel and firing quickly, I ran another 5 rounds @41g again and it was .88". With the right loads, she's easily sub-moa. I did another 3 shot group of the factory 140g Accubonds and it was a .75" group with a hot barrel.

The primers are still getting the halo effect, but no other pressure signs. (Which given these were very light loads, I'm not surprised.)

The bolt face finish is definitely etched in the same pattern it had before. (It came back that way from their test firing.) Thankfully, it doesn't seem to be causing any accuracy issues. So while I'm disappointed that my 48C has the defect on the bolt face, and that two trips to the shop weren't enough to resolve it, at this point, I'm just going to live with it. If this really is just the nature of cerakote on a bolt face, I'd rather have had it left it bare metal or just parkerized.

Here's a pic if you're curious:
(It really doesn't show the detail well, but it almost looks like the cerakote is flowing outward.)

The staff at Nosler was good to work with and very prompt when I'd call or email., but I have to admit, I'm surprised they just ended up saying "that's just how it is"... not exactly was I'd have hoped for a rifle in this price range.

edit: fixed one of the links

 

[Anonymous]

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Here's my M48 .300WSM bolt face. No idea how many rounds but shot a lot and hunted hard. Still drives tacks.

 

[Nosler4]

Hey All,

We see this to some degree on most all of our rifles. I spoke to our NoslerCustom Division Manager about this and he had the following to say:

Some degree of this is normal on any gun with a coated bolt face. Face it - it's a layer of paint. Be it ceramic, Kryptonite, whatever - it's still paint. The head of a cartridge has a natural indent around the primer caused by the radius of the primer cup and the primer pocket coming together. What this means is that when the round is fired, and the shell thrusts back against the bolt face (with a great deal of force depending on case taper, chamber finish, load pressure, brass thickness and hardness, headspace, etc), the force on said paint will not be even. Additionally, when the bolt is lifted after firing, the case stays put and the bolt rotates against it causing wear on the paint.

All of these things are a normal tradeoff to having an all-weather bolt face. Yes, we could leave the bolt face unpainted and have no marking or ring, but then rust becomes a factor. We choose the lesser of two evils.

Each gun is different and many different factors influence this phenomenon, hence the reason some guns and caliber do it worse than others.

I hope that clears things up a bit! Of course if there are any questions, let me know.

 

[DrMike]

Good explanation, Shawn. Thank you.

 

[IdahoCTD]

You might consider Nitriding the bolts rather than coating them. It makes the bolt harder and weather proof. It would result in a better end product although it would cost a bit more.

 

[Anonymous]

Hey All,

We see this to some degree on most all of our rifles. I spoke to our NoslerCustom Division Manager about this and he had the following to say:....All of these things are a normal tradeoff to having an all-weather bolt face. Yes, we could leave the bolt face unpainted and have no marking or ring, but then rust becomes a factor. We choose the lesser of two evils.

Thanks for the explanation. I thought the wear was perfectly normal- when you consider what I've put the OTHER 99.9% of the gun through a little dimple around the firing pin hole isn't a big deal to me.

FWIW- I hunt my rifle hard and I hunt it a lot. I went 12 straight days this year in the pouring rain on a caribou hunt. Rifle was drowned, rained on, slopped through wet brush and frozen a couple of times- no maintenance in the field at all, no point really.I hung it a couple times over the tent heater to dry it out- that's it. I missed an opportunity at an awesome bull because so much water was on the scope lenses I couldn't even see through it and was out of a dry anything to wipe 'em off. My partners Remington SPS stainless was almost orange by the time we got back.

I could tell some stories about what this rifle has been through but I'd hate to hear Shawn cry... :lol:

I took it all down when I got home and found no rust or corrosion anywhere. Even areas where the coating had chipped or worn away (and there are quite a few of them now) were corrosion free... the sling swivels rusted as did the scope ring screws but they're aftermarket accesories. I wish I could get some Cerakote coated stainless Talley's to match though <hint>...

I've hunted this rifle 6 years and it's absolutely the best foul weather rifle I've yet to find.

 

[russ808]

I have to agree with hodgeman, I just came back from 6 days of hunting in dusty powdery red dirt as well as a rain shower on the island of Molokai. Not a spot of rust on the rifle but the scope rings and mounts were nice and rusty. The dirt also has lots of salt in it as we were hunting on property not far from the ocean. The rifle did well, not so good for the deer.
Russ