Firing pin bushed, now poor grouping

[rcw3]

Boyd,

+1 on that....
Robert mentionned 'cratering' when the original poster mentionned 'flattening'. This is a totally different observation. It is notorious that small pins are causing less cratering than the big ones..
R.G.C

Maybe we are looking at different posts, but this thread was started by "Potatoe" and the first posting of the thread speaks of "cratering primers" before having his firing pin bushed. My earlier reply was directed to that. I think there is some misunderstanding.

Robert

 

[Robert]

/quote]

Maybe we are looking at different posts, but this thread was started by "Potatoe" and the first posting of the thread speaks of "cratering primers" before having his firing pin bushed. My earlier reply was directed to that. I think there is some misunderstanding.

Robert

Robert,

Yes, Potatoe effectively mentionned 'cratering' in his first post, but this was before his bolt was bushed.

On his sencond post he then pointed it was now 'flattening' primers after bushing.

There is two comonn causes on cratering LR primers, often also linked together:
1)-Overpressure
2)-Weak spring or spongy blow allowing the FP to slightly blow back under 1)- aboce and metal to flow inthe hole arpund the tip.

As the second is greatly reduced with the smaller firing pin and hole, also likely less play between hole and tip, if flattening is then oberved with the same load, the conclusion is obvuous...

R.G.C

 

[potatoe]

Sorry I'm late to my party here. I've been toying around with the gun. I did check the headspace and that did not change, and I also checked the lands again to make sure I was still jamming the bullets the same as before, which that didn't change either. The only thing that I could really lean on as being the culprit was the primer ignition now being more intense from the smaller FP was changing the pressures enough to make my gun not like it. When I stated earlier that the 205m's weren't that popular, I didn't mean in general I was saying that they are not really the 'go to' for the Dasher's.

I still can't figure out the flatten primers, the smith said he didn't think that was much to worry about as long as I didn't see any ejector marks and said that the energy that was pushing the primer back into the FP hole before is now just being transferred across the bolt face since it has no where else to go. But I did see a few that showed a very slight blemish of the ejector - that was with my original load prior to the FP bushing . So I wanted to make a decent size change in pressure thats why I went down to 30.5 - 31 grs which is a very light load for the Dasher with 105gr. bullets. I still get the flatten primers, and it hasn't seemed to make to pockets loose, but I doubt I'll get the life out of the brass as I would have before. But I can't see going much less than 30.5grs.

I did get to go shoot yesterday at a new range that could get me out to 200 yards to test some other bullets as well. The conditions were not that good. We had a 5-10 left cross wind, and the benches were very sorry. The gun did show some life though, I did get some vertical that I didn't really care for but atleast it showed me something to work with. Plus a few of the groups were better than what I got at 100 yards the first time I shot after getting the firing pin bushed. I'll keep plugging along with these lighter loads.

I also want to shoot some groundhogs with this gun that's why there is a 75gr. V-max in there

The one on the left was fired prior to the bushing, also notice the now bushed FP strike is slightly off center.