Primer ridge

[Gun-fun]

Hi, I am having a problem with my reloads and need some help.
I have been reloading for 35 years so not new to the game.

I got my new barrel an SI and set it up 16 inch with carbine gas it has a .095 port.

So I am loading once fired LC brass it is cut to 1.355 and grows to 1.360 after sizing, using CCI 400 primers and hodgen H110, I started with M80s 14. 5 grains, no pressure signs , as I got up around 16.0 I see a ridge around the primer indent but the radius on the edge of the primer is good went to 16.5, primer flatter still has ridge. Poor day to chrono but by 16.5 high 1600 FPS. None of these rounds locked the bolt back so changed the bolt carrier for a NB plated and then it locked but still there is that pesky ridge around the primer even though the radius on the edge is still there and the brass ahead of the groove is .373-.374 same as prior to firing.

Decided to try lighter bullet went to sierra 110 HP started at 15 grains of H110 looked ok, by 16. there is that ridge no bolt lock to this point, by 17. primer starting to flatten with ridge? this should still be a light load, changed to carbine lower with David Tubbs spring- no ridge, no hold open. by 18.primer ridge back primer not flat and will not feed next round.

I know this is a new barrel and I have only shot 15 rounds or so through it, so it needs to wear in, yet I haven't had this ridge with 5.56 barrels and hot loads?

I am going to pull the gas block and make sure that it is alighned right and if so I probly need to open up the port from .095 too? What is standard for a sonic load gun? And why that ridge around the primer indent?

Thanks.

[Darkstang]

That ridge is due to the firing pin hole in the bolt face. Basically the cup is flowing back into the hole. This is why a lot of people bush the pin hole on bolt guns. Short of trying another bolt, not much you can do. I watch for the center of the primer strike hole to start coming back up like a volcano. The first sign of a flow back dimple, too much pressure for sure..

[Gun-fun]

Thanks Broncman,
although its strange that when I changed the bolt I had the same ridge? I guess I will try a couple of others I have. Also that the ridge went away when changing the main spring at least till I went hotter on the load, although it was still not any where near max. I will keep trying, oh and I pulled the gas block and from the carbon around the hole its close to centered.
I think I will put one of the bolts I have been using in the BLK in my 5.56 and use some XM193 ammo thats hot enough That if its firing pin hole size it should show the ridge on those primers allso.
Too bad its 3:00 AM the family wouldn't be happy with me going out and trying it right now

[Gun-fun]

That ridge is due to the firing pin hole in the bolt face. Basically the cup is flowing back into the hole. This is why a lot of people bush the pin hole on bolt guns. Short of trying another bolt, not much you can do. I watch for the center of the primer strike hole to start coming back up like a volcano. The first sign of a flow back dimple, too much pressure for sure..

Ok so I pull the BCG and put it in a 5.56 gun and fired a few XM193s , they are as hot as I know and there is no ridge around the firing pin indent, so it dosn't appear to be a problem with the bolt having too big of a hole.

So WHAT is it with this 300 BLK? Loads that arn't that hot, don't lock the bolt back and still show signs of too much pressure!

147 gr M80, CCI 400, h110, 16.5 Gr, 1680 fps= crater around firing pin indent and no bolt hold open on last round. I now have a weak single shot for an AR.

[Rifleman]

That ridge is due to the firing pin hole in the bolt face. Basically the cup is flowing back into the hole. This is why a lot of people bush the pin hole on bolt guns. Short of trying another bolt, not much you can do. I watch for the center of the primer strike hole to start coming back up like a volcano. The first sign of a flow back dimple, too much pressure for sure..

Ok so I pull the BCG and put it in a 5.56 gun and fired a few XM193s , they are as hot as I know and there is no ridge around the firing pin indent, so it dosn't appear to be a problem with the bolt having too big of a hole.

So WHAT is it with this 300 BLK? Loads that arn't that hot, don't lock the bolt back and still show signs of too much pressure!

147 gr M80, CCI 400, h110, 16.5 Gr, 1680 fps= crater around firing pin indent and no bolt hold open on last round. I now have a weak single shot for an AR.

XM193 uses CCI41 primers with a thicker cup that won't show cratering as soon. It is also difficult to compare two cartridges that use different powders with different burn rates. The 5.56 load may be hot, but uses a much slower burning powder.

[Gun-fun]

Ok so I went with a winchester primer and no more ridge
Now I see inconsistant pressure with one primer being pretty flat and another not so much, same thing with bolt hold open, I wonder why? It is around 32 degrees here and I hear H110 is temp sensitive? I will have a little more time tomorrow to run several across chrono.

[JohnInNH]

I get that slight ridge with FACTORY Remington 125 OTM.

I also get it with some of my W296 loads I thought they were maybe to hot, but like you the ridge had NO primer signs of pressure. Just that slight ridge you can feel with you fingernail. The radius is round, and very little bolt face impression on the flat.

This is with my Micro7 FYI... It seems to be a 296 powder anomaly and not happening with A1680 or 5744.

I may ignore it and load till the primer gets a slight bolt face impression and a slight squared edge. (similar to factory supersonic loads)

If I keep the FPS at about 2250 with a 125 TNT and no loose primers .. and no flowing into the pocket with just this pesky ridge I will not get overly concerned. I think it has to do with the pressure curve and the Remprimer cups.

[Gun-fun]

I havn't got a chance to run over the chrono yet. When will it stop snowing! So I looked at the gas port size, this is a SI 16" barrel with carbine length gas port, The port was at .092 even though they said .095 on there info so it was close, but I havn't been able to get bolt hold open on last round as I have been loading singles while testing reloads. Drilled port too .104 Now I have bolt hold open YEA!! This is with 16. grains of H110 and a 147 gr M80 loaded to 2.140 OAL the win. primers look good with no crater and a med radius left on the edge.(prior to opening port even 17 gr. h110 would not hold bolt open and primers were getting flat)
Well when the snow gos away and I can crono and find my brass I will look at refining this load, at least I have a round to plink with. Time to go out to the lathe and make more brass

[Gun-fun]

I get that slight ridge with FACTORY Remington 125 OTM.

I also get it with some of my W296 loads I thought they were maybe to hot, but like you the ridge had NO primer signs of pressure. Just that slight ridge you can feel with you fingernail. The radius is round, and very little bolt face impression on the flat.

This is with my Micro7 FYI... It seems to be a 296 powder anomaly and not happening with A1680 or 5744.

I may ignore it and load till the primer gets a slight bolt face impression and a slight squared edge. (similar to factory supersonic loads)

If I keep the FPS at about 2250 with a 125 TNT and no loose primers .. and no flowing into the pocket with just this pesky ridge I will not get overly concerned. I think it has to do with the pressure curve and the Remprimer cups.

Oh and I was glad to see your post that even factory ammo can have a primer ridge, I think you are right about the pressure curve, maybe due to the faster powders there is a fast small spike thats not substained long enough to show in the over all pressure.