Dasher Woes - Please Help!!

[Joe Salt]

What kind of info do you need to put mine though Quick load? I'll gladly give you what I have.

Joe Salt

 

[BCBRAD]

QuickLoad is a guide. I use it, as well. According to what changes you make in entering information, it changes the output. Using my cartridge length and barrel length, it is 60,321 psi at 32.5. That’s with the standard weighting factor.

Did you calculate start pressure? Mine is 10,535 psi with the bullet 0.010" of the lands. The default weight factor is 0.40, the 6 Dasher is 0.57 by my calculation. For 32.2 gns of Varget the pressure is 72,742 psi and 3013 ft/s in a 29" bbl. The max psi for the Dasher is listed at 65,000 psi.
The default start pressure for cup/core bullets is 3625 psi, add 7,200 psi for a jammed bullet, if jammed the total start pressure is 10,825 psi. Now subtract ~29 psi for every 0.001" off the lands. This is 290 psi and the total start pressure is 10,535 psi.
As you can see the max pressure for 32.2 of Varget is 72+ which is ~ 7,000 psi more than default of 65,000 psi.
What is your start pressure?
In QL every function relates back to velocity which accounts for all variables.

 

[BCBRAD]

So your saying with that QL. with me running 33.4 gr. Varget with a 103 VT. I'm up over 75,000 psi? I don't understand these numbers, not saying there not right, but with my Dasher I can go up to like 34.1 before I get any pressure. So please explain how that QL. program can decipher from one rifle to another? No WAY

Joe Salt

Many well made rifles do not show traditional pressure signs ,other than velocity, until 70+++ psi.

 

[BCBRAD]

What kind of info do you need to put mine though Quick load? I'll gladly give you what I have.

Joe Salt

Internal volume of case in grains of water, filled to the top of the neck.
Distance bullet is off the lands , in thousands of inches
Bullet weight and kind eg: 105 lapua scenar
Bullet length, diameter, diameter of the boat tail, length of boat tail
Powder weight and kind, X number of grains of what ever powder
Cartridge overall length, COL
Case length
Velocity, average of 5 rounds
Barrel length, bolt face to muzzle

I will run it on QL for you.

 

[TylerFromMS]

Did you calculate start pressure? Mine is 10,535 psi with the bullet 0.010" of the lands. The default weight factor is 0.40, the 6 Dasher is 0.57 by my calculation. For 32.2 gns of Varget the pressure is 72,742 psi and 3013 ft/s in a 29" bbl. The max psi for the Dasher is listed at 65,000 psi.
The default start pressure for cup/core bullets is 3625 psi, add 7,200 psi for a jammed bullet, if jammed the total start pressure is 10,825 psi. Now subtract ~29 psi for every 0.001" off the lands. This is 290 psi and the total start pressure is 10,535 psi.
As you can see the max pressure for 32.2 of Varget is 72+ which is ~ 7,000 psi more than default of 65,000 psi.
What is your start pressure?
In QL every function relates back to velocity which accounts for all variables.

Who said anything about jamming bullets?

 

[Joe Salt]

I'm going the same speed as you just at 3000 fps at 33.4 of Varget and just touching the lands. Water volume I done it once can't remember, just guess.

Joe Salt

 

[BCBRAD]

Who said anything about jamming bullets?

It is a starting point for calculations

 

[BCBRAD]

I'm going the same speed as you just at 3000 fps at 33.4 of Varget and just touching the lands. Water volume I done it once can't remember, just guess.

Joe Salt

You are ~80 000 psi using all my parameters for a 29" bbl.

I use H-4350 and hit the 4th node at 1.324 mS
Velocity is 2845 ft/s with 32.94 gn of H 4350
At 57 800 psi, won't make it to the next node and stay under 65 000 psi

 

[Joe Salt]

BCBRAD Thanks but I wouldn't count on mine being at 80,000 psi I can open the bolt with one finger. No pressure and my brass lasts a long time.
Like I was saying I don't have much faith in those Number things. But who am I to not believe in math. When I start a new barrel, the first thing I do is find out how much powder I can run before I get pressure. And like I said I can go almost a grain more. Not that I want to but if I need a little more H.P. I can get it.

Joe Salt

 

[TylerFromMS]

It is a starting point for calculations

So using the "stock" values, and only changing coal, powder, and powder charge, I am within 15-20fps, and way under pressure. Labradar and magnetospeed verified.

I see you use OBT. Someone smarter than me gave me this when I asked about it: "It is based off barrel reflections but doesn't take into account the barrel is mechanically locked with the action - a big dampener of widely varying size and shape depending on action configuration and make. Neither does it take into account the pretty big speed of sound difference between stainless and chromoly steels and their hardness/production method." He equated it to trying to see the future. It is a neat tool, but like QuickLoad, it is not infallable. That is a mild load in the lower node of a dasher with .130 freebore jumping a hybrid 0.030.

Now, back to the point of the post: OP is waiting to hear from the gunsmith.

 

[BCBRAD]

As an example I loaded the 112 gn Barnes match in my 6 Dasher. With all my weights and measures 33.14 gns of H-4350 gave me 2790 ft/s, a 5 shot group at 109 yards/100m produced a 0.5 moa group , two groups. Loaded 10 rounds to test the QL model.
The velocity of 2790 puts me off the node for a 28.938" bbl of 1.321 mS. It requires 2813 ft/s. So I adjusted the burn rate with the original 'modelled' load to reflect the actual velocity of 2790 ft/s. Then I increased the powder charge to 33.42 gns H-4350 so the final result will be 2813 ft/s at 61 777 psi.
This puts me exactly on a node. I will range trial the amended charge weight. Past experience points to the best load.
This is also an OCW load, so is tolerant to minor variances in the load.
So, I expect a little better accuracy with the revised load.
The load described has an ES of <10 ft/s and I don't fiddle with seating depth at all.

 

[Longtrain]

Looks like your chamber is too tight at the back end.

I’m a Dasher shooter, I only use FF’ed Lapua, so I’ve got no experience with Alpha brass. With the myriad of posts in this thread and all the information, I didn’t think I could add anything, but after looking at your fired cases, maybe I can.

When I started shooting the Dasher I was using Wilson hand dies, after a couple of firings, I had chambering problems where the case would not chamber. On some other cases, after firing I could not get secondary extraction and had to either bump it with my palm or use a rubber mallet to gently pop the bolt open. Obviously, my problem was not FL sizing the cases, even resizing those cases did not fix them, they had to be tossed.

The markings on your brass just above the rim is exactly what I had on my stuck cases. If you’re FL sizing, I agree that either your chamber is under sized, roughly finished or both, causing markings, which is not right for sure. David Tubb has a YouTube video just out where he speaks of small base dies and making sure that his rounds drop into the chamber easily, maybe worth a look.
Casting the chamber and having it measured and examined for flaws is a good idea IMO, then re-chambered with a good reamer of dimensions friendly to Alpha brass, or a small base custom die or both. (My reamer is .2704, no-turn Blue Box Lapua, so Alpha wouldn’t work without neck turning)
Good luck.

 

[L W P]

So after reading this post and what looks like a rear chamber issue, would a .471" reamer be more appropriate for Alpha brass? Or does the rear chamber just need polishing up?

 

[L W P]

I’ve been getting the same velocities with both brands of brass. I do believe the work hardening of the base of the Lapua from fireforming loads leads us to believe the Alpha is running into higher pressure quicker. Using a fireforming load for its first firing changed my results as far as pressure signs in subsequent firings.

New Alpha weighed within 4 grains of fireformed and chamfered Lapua.

I loaded up some of my Lapua brass that had been fired in my chamber, cut by the same person and same reamer:

View attachment 1175993

Notice the scrapes near the head. I shot some of OPs brass and loads in my rifle and it ejected perfectly. I usually run the same load thereabouts, in both brands of brass, and it does pretty well. I’ve tested a node 1 grain higher that was also good, but I didn’t want to trash my brass that quickly.
Lapua, 3rd firing:
View attachment 1176006

Alpha straight out of the box with only a mandrel ran through the mouth. Same load:
View attachment 1176007

Do I trust the actual velocities of the Shotmarker? No. Do I trust the shots measured from the same Shotmarker at the same time with no change in setup to correlate? Absolutely. SD and ES has shrank significantly on 2nd and 3rd firings. I’ve repeated my results with a borrowed magnetospeed.

OP is waiting to hear back from the gunsmith today. I believe the winners were those that said a burr or tight spot in the chamber. The action and brass is solid.

Is your reamer specs the exact same as OP? Also I wounder why Alpha doesn't make their 6 Dasher brass as an optional small flash hole?

 

[TylerFromMS]

Is your reamer specs the exact same as OP? Also I wounder why Alpha doesn't make their 6 Dasher brass as an optional small flash hole?

Same barrel and twist, same reamer, same smith. The rear of the chamber needed to be polished, as that solved the issues.

I honestly don't believe that the different flash hole size matters that much in this case. I'm a nobody, though, so grain of salt and all.

 

[L W P]

Same barrel and twist, same reamer, same smith. The rear of the chamber needed to be polished, as that solved the issues.

I honestly don't believe that the different flash hole size matters that much in this case. I'm a nobody, though, so grain of salt and all.

Thanks for the info.