cratered primers ?

[patchhound]

just how high is the presure when you start seeing cratered primers? is it something you can live with or should you back down. honestly, a lot of the loads i see for my 6mmbr look like they would make me eat my bolt, i`ve worked up a load of 30.5grs of varget and 75gr v-max with a cci 400 primmer, norma brass and i`m starting to see a hint of cratering. the book says 30.8 max but i see other loads of 32+ varget so just how far do you push it? i`ve reloaded for about a year and i`ve always have kept myself in the safe zone but my new load shoots good, i just don`t know for sure if it`s better or not to have some cratering.

 

[Forum Boss]

If you have a factory Rem or Savage action WITHOUT a bushed firing pin, you will see flow back into the firing pin hole, sometimes at a relatively modest charge.

How are your primer pockets with the 30.5gr Varget? That's a pretty definitive sign. If they're still tight like new, I wouldn't sweat it. Your 30.5 is a load many folks are running with 105s and it should be well under max with the 75s UNLESS you have an extremely short throat or you are going WAY into the lands.

What's your OAL?

 

[MrK.]

I was wondering the same thing. Here is a pic of one of my 7mm TCU cases shot with my 14in Contender. One of my friends freaked out when he saw them. Another seemed unconcerned. It is a stout load admitedly but I have never seen any signs of gas escaping around the primer and the case heads average about the same diameters new ones. I have been shooting this load for close to 20 years and am just now rotating in new brass. This is 29grains of H335 with a 145gr grain speer spitzer. It is a grain and a half below max in my Speer #11 but I understand above max in some other pubs. Shoots a single hole at 75 yds which is about as far as my old eyes can shoot reliably with my 2X Leupold. Hot or Not?

 

[Forum Boss]

Swamp,

If that's a CCI primer, that a BIG crater. Even noting what I said about the non-bushed firing pin, that's more crater than I like to see.

BUT, look carefully at the edges of the primer, where it meets the pocket walls. There is still a pretty normal radius there. Usually, when you are really up in the high pressure range, one will see flattening at the edges.

I think that photo is mostly a flow issue. I'd first change to CCIs if you haven't already.

 

[ScottyS]

Hot or Not?

Offhand I would say no. That looks more like classic cratering due to loose firing-pin-hole tolerances. The edges of the primer are still rounded, and not flat. There are several signs to look for besides just cratering. Just gauging the primer edge by itself I would say that you're getting close to the top end, but not dangerous.

Plus, the longevity of the load bears you out.

 

[patchhound]

my oal is 2.235 and i`m off the lands about .005. my action is a CZ 550. i don`t see any cratering at 30grs but my groups open up .25 easy . i`m tempted to push her alittle more but i don`t think it`s real safe, have`nt tried the R15 yet. i`ve only reloaded this brass two times and the primmer pockets are fine so i`m still stuck on how to see PROBLEMS. when should i back down?

 

[ScottyS]

Oops, posted right behind the Ed.

Extra hits all around!

 

[Forum Boss]

my oal is 2.235 and i`m off the lands about .005. my action is a CZ 550. i don`t see any cratering at 30grs but my groups open up .25 easy . i`m tempted to push her alittle more but i don`t think it`s real safe, have`nt tried the R15 yet. i`ve only reloaded this brass two times and the primmer pockets are fine so i`m still stuck on how to see PROBLEMS. when should i back down?

Measure the web of your case right at the top of the extractor groove. Another sign that shows you're too hot is ejector smear. That's a round spot right over the ejector hole. When the brass starts flowing into that area you're too hot.

Going back to Patchhound's load. With 30.5 Varget and 75 V-max at your OAL, QuickLOAD is giving pressure in the 44,000 psi range--way below max. NOW, QuickLOAD can be off for a zillion reasons, but keep in mind that I consider 62000 psi to be a HOT load in this case. So you've got a lot of room to play. 100% load density with the 75s at 2.235 OAL is showing at 32.6 Varget and 53500 psi.

 

[MrK.]

The primer in the pic is a Winchester WSR. I simple use Winchester primers out of habit. I always felt that my 7TCU rounds were safe because the edges of the primer still had a good radius,as mentioned). Thanks for the input. Why should I chnge to CCI? The only head to head tests I have done have been CCI 300s vs Winchester WLPs in my supressed Ruger 77/44 rifle. I was initially looking for quieter rounds but found that the WLPs gave a smaller extreme spread in velocity. This is with a very low charge of Win 296 and a 300gr XTP

ps I keep a spent factory .257 Weatherby case on the shelf above my bench. These loads are pretty hot. I like to compare the primers I shoot to this case. This one is pretty flat.

 

[Forum Boss]

If the WLRs give you the best results, there's no need to change. However, on a hardness scale the Wins are the most soft while the CCIs are the most hard,among domestic primers). You'll see less cratering with the CCIs that's all I meant.

 

[patchhound]

thanx moderator, i`ll try pushing her a little harder and see what happens. i`m also gona go back to a 450 primmer since the first loads i shot were to lite- will get back to ya later.