I'm following this up, because my smith came up with a creative solution to a multi-faceted problem. And there are plenty of HOWA 1500 owners out there, some of which are probably facing the same problem. Apologies in advance for incorrect nomenclature; I am not a machinist.
As mentioned, in the HOWA 1500 the firing pin hole is a standard 0.075" for both large and small. Combine that with a worn firing pin + hot loads, and you'll start to see cratering, and possibly blanking (if they are hot). The best course of action is to reduce the firing pin, and hole to approx 0.060" (for small rifle).
We discovered another drawback with the HOWA 1500 SA, and that is the bolt face is only 2.5mm thick (at the thinnest section). This is significantly thinner than say a Remington bolt face, which is more like 10mm. This made my smith uncomfortable taking the regular press-fit, bushing approach. He was worried about compromising the strength of the bolt face, and rightly so. This is the one surface you DO NOT want at all weaken, for obvious reasons. Taking a counterbored, threaded bushing screw was also not safe, along the same lines of strength compromise.
The suggestion was made to instead fill the existing hole with weld, then drill that out at the reduced diameter. Traditional welding approaches seemed dangerous as the bolt face's heat hardening may be compromised.
Enter stage laser-welding. A laser weld is superior in many ways, the main being (in this context) it does not heat affect adjacent areas. So that's exactly what he achieved:
- Laser weld filled the hole
- IMG_2291.JPG (390.12 KiB) Viewed 4043 times
- Drill and face with carbide tooling (high-speed tooling too soft)
- IMG_2293.JPG (534.65 KiB) Viewed 4043 times
- Ground and rounded firing pin
- IMG_2298.JPG (427.4 KiB) Viewed 4043 times
- Superb final fit at 0.060"
- IMG_2297.JPG (435.02 KiB) Viewed 4043 times
Here is the final outcome, no more cratering:
- Final outcome; factory loads no longer cratering.
- IMG_2302.JPG (488.1 KiB) Viewed 4043 times
(cheap/plentiful) CCI400s here I come!!
(I already have a safe full of them!
!)
Cheers,
In2.