Dasher primer cratering

[pburr]

Don't bump anything! Resize without bumping and shoot it again. See if that had an impact.

 

[savagedasher]

Don't bump anything! Resize without bumping and shoot it again. See if that had an impact.

Others have had that happen . Take the expander ball of the sizing die . Larry

 

[pburr]

Others have had that happen . Take the expander ball of the sizing die . Larry

Help me out here, but I'm unsure how taking out an expander ball will have an impact on the OP's problem? Seriously, I would want to know? I personally don't use them, but if he is saying he bumped the shoulders back by .004 that seems a little much to me!

 

[savagedasher]

Help me out here, but I'm unsure how taking out an expander ball will have an impact on the OP's problem? Seriously, I would want to know? I personally don't use them, but if he is saying he bumped the shoulders back by .004 that seems a little much to me!

.004 can be too much . With the expanded ball on the die it can give you a false reading. Sure cured the same problem for friends I shoot with .

 

[DOGCAPPER]

Not too much pressure or the primer edges would be flattened. Fireing pin fit is the culprit.

 

[savagedasher]

How short are the cases on headspace? Matt

See you have seen that before. Larry

 

[gambleone]

Going to try & get the new pin/spring Bat has come out with.
Thanks for all the input.

 

[dogdude]

At .004 bump its Headspace..bumped some to much and they looked just like yours, thankfully I used those as foulers.

 

[CaptainMal]

Thanks for the picture. I have had a Savage with two Dasher barrels, a Dasher BAT, and currently have two Stolle actions in Dasher. ALL did or do what you show to some degree.

It was worse when I had a carbon build-up once. All of mine do that or did that. Kind of guess I think it's normal for a Dasher.

 

[Jeff Conover]

Too much shoulder bump will cause a dasher case to blank primers. The dasher case with a 40 degree shoulder has less taper that a normal case such as a 308 and acts differently. All cartridge cases seal up in the chamber at the case mouth and the front of the case back when fired. If head space is too big the case can split in the body because the head did not meet the bolt face before the case failed.

The case grips and seals into the chamber from the case mouth, not from the bolt forward. Everything is going on in milliseconds. The chamber shoulder is the stop in the chamber and the case acts like a balloon and needs the full support of the chamber and the bolt so not to fail.

The primer pressure forces the case forward in the chamber. If the dasher shoulder is bumped back further, then the case is driven into the chamber further. The primer sets back against the bolt face and say the case head is pushed .007" forward of the bolt face instead say .002".

If the dasher case head is too slow to set back against the bolt, the primer will dimple or blank because it took too much pressure against the firing pin hole without the help of the case head against the bolt face.

If the case is properly sized the case head will meet the bolt face in time and reseat the primer in the pocket and spread the pressure across the case head. The pressure timing will be correct and the primer will not be an issue.

To set up your sizing die pull you firing pin and do not have a strong ejector place you unsized cases in the chamber. Adjust the sizing die until the bolt just closes.

 

[savagedasher]

Too much shoulder bump will cause a dasher case to blank primers. The dasher case with a 40 degree shoulder has less taper that a normal case such as a 308 and acts differently. All cartridge cases seal up in the chamber at the case mouth and the front of the case back when fired. If head space is too big the case can split in the body because the head did not meet the bolt face before the case failed.

The case grips and seals into the chamber from the case mouth, not from the bolt forward. Everything is going on in milliseconds. The chamber shoulder is the stop in the chamber and the case acts like a balloon and needs the full support of the chamber and the bolt so not to fail.

The primer pressure forces the case forward in the chamber. If the dasher shoulder is bumped back further, then the case is driven into the chamber further. The primer sets back against the bolt face and say the case head is pushed .007" forward of the bolt face instead say .002".

If the dasher case head is too slow to set back against the bolt, the primer will dimple or blank because it took too much pressure against the firing pin hole without the help of the case head against the bolt face.

If the case is properly sized the case head will meet the bolt face in time and reseat the primer in the pocket and spread the pressure across the case head. The pressure timing will be correct and the primer will not be an issue.

To set up your sizing die pull you firing pin and do not have a strong ejector place you unsized cases in the chamber. Adjust the sizing die until the bolt just closes.

How many of times have you blank primers fire fourming. ?
That is a head space issues.
Too much headspace when sizing is the same .Larry

 

[Jeff Conover]

I fire form with cream of wheat with a false shoulder on the neck, but a jammed bullet to hold the case head back works. Also firing forming is done at low pressure.

 

[savagedasher]

I fire form with cream of wheat with a false shoulder on the neck, but a jammed bullet to hold the case head back works. Also firing forming is done at low pressure.

I have done it all ways. The best has been heavyweight flat base bullet with a firm load . Larry

 

[savagedasher]

I have done it all ways. The best has been heavyweight flat base bullet with a firm load . Larry

With a hard jam Larry

 

[BoydAllen]

Use a bathroom scale and a block of wood thicker than the dimension from the front of the firing pin shoulder to the tip of the pin. Drill a hole in the block that is big enough for the front of the pin, and small enough so that the block can support the pin on the front of the shoulder. Note how far out of your shroud your cocking indicator is when the action is cocked, and with that in mind, put the block on the scale, insert the tip of the pin in the block, and holding on to the shroud, press down to the point where the cocking indicator is sticking out about the same as when the action is cocked. Then read the scale. From your picture, the stock spring looks to be on the light side. If you talk with someone who modifies BAT striker assemblies, you may find one that uses heavier springs. Personally, as long as you are not piercing primers, and do not have any other signs of excess pressure, I would not worry about the crater. I think that the pressure is backing out the pin after the initial strike. Load a case with a primer only, fire the primer and take a look at the dent. Let us know what happens. Something that can happen with some powders is that a hard carbon ring can start to form in the throat of the chamber, but I think that the effect on pressure would be consistent. BATs are often on the edge as far as striker system energy, with the result that a cottage industry has grown up centered around making modifications. I would give someone like Wayne Campbell a call. http://benchrest.com/campbell/
He is a very accomplished shooter that knows a lot about these actions and can help you with your problem.

 

[gambleone]

I did what you asked Boyd. I fired 6 cci-450 primers. 3 not bumped at all & 3 bumped
4thou. All primers perfect, like they should be. No dimples or craters. I will size so
the bolt closes easy without bumping any more than 1thou. I'll try this & post here.
Was kind of an accident i bumped that much. Never intended to. I have the new .280
pin/spring combo coming from Bat just case it is a weak spring.