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How much did getting your bolt bushed help catering/piercing?

The issue is tolerance stack. IIRC, the firing pin dimensions are .068 to .070 and the bolt head firing pin hole is .071 to .073

So if you have a slightly undersized firing pin and a max dimension bolt head, you can end up with .006 to .007 clearance (WAY too much ) between the bolt head hole and firing pin. This is the scenario I encountered and was piercing primers with light hand loads and many factory loads.

I fixed this by ordering several firing pins from Savage and cherry picking the one that fit best. No more issues and the total cost was like $18.00 shipped to my door. Savage Customer Service was tops by me, and I was out of action for less than a week.
I fully understand the issue. I was just wondering how ordering another part from Savage would solve your problem, unless Savage has realized the need to change the manufacturing tolerance. I may have missed it but don't remember reading where you had said you ordered several and picked the best one. I guess in this instance that strategy paid off. Could have been you ordered several on many occasions and never did get one that works. Seems like the majority of companies these days operate under the theory of "that's close enough, get it out the door". I ran CNC lathes at one time for a company building flywheels for John Deere. We measured and charted key dimensions on every flywheel and measured and charted every dimension on every 4th flywheel. On top of that, QC picked several out of the stack and re checked them. Not many out of spec parts get out the door with that kind of attention to detail. I'm guessing that PTG and Greg Tannel give that kind of attention to detail.
 
Cratering is caused by force pushing the brass up. Force = pressure x area. Bushing reduces the area by the ratio of the square of the diameters. I've NEVER seen a crater with a .062 nominal firing pin. QED.

--Jerry

PS So it is just physics. It will work on any brand bolt. If your firing pin is .080 or higher, I guarantee you'll have craters eventually. There is a middle ground. Many custom actions use a .070 pin which seems to work. If you prefer that, I can bush to any diameter you want. Don't recommend going much below .062 but I wouldn't be afraid to try it if you have a good reason.

The one limitation is material of the bolt. Many guys won't touch an old Mauser action because they are often hardened and unpredictably so. AI is hardened. I generally can bush them. I'm always willing to take jobs others turn down. Will cost a bit more.
 
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Timeout, yup, you get it. You've been there and know that without 100% inspection, there will be substandard parts making their way through the manufacturing process.
Ask any manufacturing business owner about the costs of Quality Assurance (QA), and they will tell you it's a never ending expense that only seems to go up, and a prime killer of profitability. In the commercial manufacturing world, when profits dwindle, QA is the first department to take the hit.

So if you read between the lines in my first post, my firing pin was substandard, the diameter was too small. The firing pins are probably made by a sub contractor and only a sample is inspected before each shipment is accepted. I was just unlucky and got the runt of the batch.

By purchasing a quantity I was able to cherry pick a good fit. As I recall, they were like $2 each.

Bushing a one piece bolt makes good sense, but makes little sense on a Savage. If it were me and replacing the bolt head became necessary, I'd chamber one of my fire formed cases, and see if the bolt closes normally. If so, I'd put several pieces of tape on the head, checking the fit at every additional layer, (or use the partially seated primer method) to determine headspace of the new bolt head compared to the old bolt head. If it's way too loose or way too tight (unlikely, but possible) and resetting the headspace becomes necessary, OP will have to buy or borrow the tools, at additional cost. The design of the Savage makes this process easy enough that just about anybody can DIY.

Small differences in fit can be dealt with by adjusting FL dies. If further cratering is experienced, OP can switch to a primer with a heavier cup material to help reduce possible piercing.

YMMV
 
Link,
Bad cratering will erode the firing pin hole can result in hard bolt lift by itself.

Texas10,
The fit is irrelevant. I know bushing sounds like we are trying to reduce the gap. That's not it. the diameter of the firing pin hole is what matters. The firing pin is actually pushed back of the primer by the force generated by pressure in the casing.

--jerry
 
While Fire Forming Dasher loads with a Savage and forming barrel, I found that Winchester primers pierced 10% of the shots. And CCI br4 never pierced.
 

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