Why am i blowing primers ( Rem 7 1/2 br) ONLY

[bozo699]

I have set them aside for now I'm using 450s I'm just looking ahead when I have no more 450s and I have to go back to the 7.5 5000 in the ammo box may be last resort

How much head space are you running?
Wayne

 

[Adam 6mm build]

Men I really appreciate the input some of these are way out of my league I see I have a lot of learning to do

 

[Link]

From what I have seen 29 gr Varget is a mild load? Just change primers?

 

[bozo699]

Men I really appreciate the input some of these are way out of my league I see I have a lot of learning to do

Make sure you bump your brass about .002-.003 drop your charge a grain or grain and a half make sure your neck tension isn’t too much.002-.004 make sure your not jamming into the lands and work your load back up with the 7-1/2 primers, check firing pin protrusion and if it was properly bushed,check for a carbon ring and it should be good to go!... good luck
Wayne

 

[L.Sherm]

I think 7 1/2 are thinner like 205’s use 450’s or BR 4’s and your problem will probably go away.
Wayne

7.5's have the same cup thickness as BR4 and 450's

 

[shoot4fun]

My 6br 1-8 twist 29grn varget 105s am I not setting them deep enough (more crush)

This should be a compatible load IF you are using Lapua brass.
For Peterson brass maybe you should drop a couple tenths and try again.
As already stated, you may have a carbon ring causing a pressure spike. Unless you have a bore scope it will be difficult to determine.
I have tested 6BR, Peterson brass, RP 7 1/2, 105 Hybrid but using SW Precision powder (29.7 grains) without primer blown.

 

[carlsbad]

I have never seen a firing pin hole bushed to .062 blow primers or even have significant cratering.

I have seen a couple of misguided machinists bush a firing pin without turning the pin down. They think the problem is that the firing pin is too loose in the hole. that isn't the case. In fact, a couple of thou clearance is recommended. You don't want any binding as the pin comes through the hole. the problem is that the hole is too big and the brass tries to collapse into it.

think of the brass across the hole as a trampoline If the diameter of the trampoline is too great, it won't be able to hold up the bouncer. same with firing pins. If the diameter is too great, the brass in the primer will be pushed into it.

Now if your (the OPs) bolt has been bushed to .062 and you're still blowing primers, your pressure is offscale high.

 

[JB10]

I have set them aside for now I'm using 450s I'm just looking ahead when I have no more 450s with the way things are and I have to go back to the 7.5 5000 in the ammo box may be last resort

Ill take those 7 1/2 off ur hand. I love them in bolt action 223 and my ar's.

 

[JB10]

In my 6br im using h4895 but running fed 205 with no issues. Plain stock r700 action with no work done to it. Lapua brass

 

[Hal]

Wasn't there a bad lot of Remington 71/2s.
You might try a different lot # of primers.

Hal

 

[timeout]

I have never seen a firing pin hole bushed to .062 blow primers or even have significant cratering.

I have seen a couple of misguided machinists bush a firing pin without turning the pin down. They think the problem is that the firing pin is too loose in the hole. that isn't the case. In fact, a couple of thou clearance is recommended. You don't want any binding as the pin comes through the hole. the problem is that the hole is too big and the brass tries to collapse into it.

think of the brass across the hole as a trampoline If the diameter of the trampoline is too great, it won't be able to hold up the bouncer. same with firing pins. If the diameter is too great, the brass in the primer will be pushed into it.

Now if your (the OPs) bolt has been bushed to .062 and you're still blowing primers, your pressure is offscale high.

I am using Rem 7 1/2's almost exclusively in my Dashers. I have had bolts bushed by Carlsbad and Gretan. I haven't had a blown primer since. Is your firing pin .062" diameter? The smaller diameter firing pin is crucial in remedying your problem.

 

[dgeesaman]

40 x action bushed firepin it only does it with rem 7 1/2 primers

How do other primers look? Are they extruding around the pin? Are the corners flattening?

What about the 7-1/2s - any of those signs?

David

 

[expiper]

how old are your primers,,,,back in the 70's the Rem. 7-1/2's had cups that were tooooo thin,,,I pock marked the bolt face of a cupla rifles with them,,,,you may have some of these old ones,,,if they are blowing it could ruin your trigger,,,,stop using them,,,Roger

 

[spclark]

Nobody's yet asked what condition your firing pin's in... have you looked at its tip with a loupe or some other kind of magnification? Is it smooth & rounded or is there some damage from one of the earliest blown primers? If present that alone will affect every primer fired afterwards.

 

[expiper]

I'm having issues with blowing Rem 7 1/2 br primers please give some advice to correct the issue thanks Adam

I just thought of something else (I responded #33) ,,,I notice your action is a 40x,,,,is the bbl a Rem original in 6mm BR,,,if soooo,,,the chamber could be the old 1.520" length and your ctg. brass could be to long!!!...just thinking out loud,,,,its tuff to diagnose problems from miles away ,,,Roger

 

[243winxb]

Hotter 7 1/2 prime, more pressure, reduce powder charge.

 

[NorCalMikie]

Or, just throw more $$$ at it by "NEEDING" a firing pin bush???
NEVER had issues with needing the firing pin bushed and, I HAVE needed to beat the bolt handle open a few times with a HOT load.
And, the only issues with primers was from too much head space.

If it was me having issues, I would start by making sure I hadn't pushed the shoulders back too far when sizing and caused a head space issue.
When the round goes BANG, the case isn't against the bolt head, (head space issue) the primer starts to back out of the pocket and gets punched by the firing pin. Case head against the bolt head ? That issue cured.
If the fired brass will re chamber with no issues, size the neck without pushing the shoulder back.
Think about going to a lower node. (before fixing the blame on the primers or the firing pin bushing thing) Still get the accuracy without suffering brass issues.
Keep it simple.

 

[timeout]

Or, just throw more $$$ at it by "NEEDING" a firing pin bush???
NEVER had issues with needing the firing pin bushed and, I HAVE needed to beat the bolt handle open a few times with a HOT load.
And, the only issues with primers was from too much head space.

If it was me having issues, I would start by making sure I hadn't pushed the shoulders back too far when sizing and caused a head space issue.
When the round goes BANG, the case isn't against the bolt head, (head space issue) the primer starts to back out of the pocket and gets punched by the firing pin. Case head against the bolt head ? That issue cured.
If the fired brass will re chamber with no issues, size the neck without pushing the shoulder back.
Think about going to a lower node. (before fixing the blame on the primers or the firing pin bushing thing) Still get the accuracy without suffering brass issues.
Keep it simple.

I have popped a couple of primers in a 6BR and the issue wasn't excessive headspace, nor had I created excessive head space by pushing the shoulders too far back. The primers being used in those particular cases were Federal GM205M. The action was a Rem 700 with a stock Rem bolt and firing pin. The solution to my problem was having the bolt bushed and the firing pin downsized to .062". I have never had an issue with any primer in any of my Rems since bolts are bushed and the firing pin diameter decreased. So yes, IMHO, there is a reason to have bolts bushed. Pretty hard to decrease the firing pin diameter without bushing the bolt. I can say that there are plenty of shooters that have eliminated the blown primer issue by decreasing the diameter of the firing pin.

 

[carlsbad]

We tend to focus on which brand of primer is better because that is the easiest thing to change but the bottom line is, there are minimal differences and switching to a different primer may help, but it won't help much. If it solves your problem, you don't have much margin and slight changes can push you right back into problems again. There are 2 real, permanent solutions available:
1. significantly reduce your pressure via load changes.
2. turn firing pin and bush.

--Jerry

 

[Jdne5b]

Send your bolt to Carlsbad, even if it's been bushed maybe its still too big or too much clearance. He fixed mine up and nothing pierces now. Before I could even pierce a cci450.

Post pictures of the fired rounds if you have some.