Dasher Woes - Please Help!!

[Snipers World]

Hey guys I am seeking the collective knowledge of this forum to help me diagnose a secondary extraction issue with my new 6 dasher build. The action, barrel and brass were all new at the start of this gun. My issue is that when I shoot I am having secondary extraction issues requiring a mallet to extract the brass on virgin and sized.

Components:
Brass - Alpha Dasher
Action - TL3 LA
Barrel - Krieger 7.5 1.25
Powder - Varet (32.0) grains
Bullet - Berger 109
FL Die - Whidden w/ .267 & .268 bushing
Seating - Wilson Inline

The first thing I examined was pressure - The cases nor action show any signs of pressure. There is no primer flow or push, no strange carbon rings, the speed is as expected at 600 yard (shotmarker), the bolt close and open are both normal with zero extra resistance on open after firing. Sized cases have no extraction problems and the freebore was cut for the 109 and im 30 thou off the lands. I had problems at 32.0 grains of powder (I'm not currently aware if less powder will still produce this issue but I would NOT expect pressure around 32gn of varget)

I talked to my gunsmith, Alpha, and Big horn to try and diagnose the issue and am still working on it. At first, I thought there may be a primary extraction issue not getting the case moving but upon talking to big horn their engineer was positive that was not the issue and I can visibly see the bolt start extraction in the primary stage making me think that is not the problem.I am seeing brass swipe on the bolt face.

I spoke with Alpha munition who had me measure multiple parameters and the brass was all within spec. After talking with Alpha I measured the necks of my brass and every single one of them is 0.2705 OD. My gunsmith told me that my neck was reamed to 0.272. If my neck was 0.272 I would expect my brass to be closer .272 or .2715 and thus believe I am having neck tensions issues from the gunsmith. I am not positive on this theory and would like to hear some others input on this.

I am waiting on a call back from my gunsmith currently now that I am aware of the fired neck OD but would like to hear some other opinions. Again there are no signs of pressure of the case and the problem is exclusive to secondary extraction.

 

[GT Accuracy]

So reading this, I am hearing that upon firing, the cases are fine, but to extract a loaded, unfired case you're having extraction issues?

"e bolt close and open are both normal with zero extra resistance on open after firing."

Are you leaving the case in the chamber even with easy bolt movement?

 

[CaptainMal]

Did I miss your turned neck wall thickness? Do remember my usage of original Norma brass in Dasher took a couple grains less powder than using Lapua cases because that brass alone did not take the same powder charge and give results like Lapua brass.

Thought of that and the final headspace fit of your brass to that chamber. Know nothing about Alpha Dasher but reads like a pre-formed case maybe.

 

[Snipers World]

So reading this, I am hearing that upon firing, the cases are fine, but to extract a loaded, unfired case you're having extraction issues?

"e bolt close and open are both normal with zero extra resistance on open after firing."

Are you leaving the case in the chamber even with easy bolt movement?

opposite, maybe I was unclear. A Fired case is getting stuck and sized new case is fine.

 

[Snipers World]

Did I miss your turned neck wall thickness? Do remember my usage of original Norma brass in Dasher took a couple grains less powder than using Lapua cases because that brass alone did not take the same powder charge and give results like Lapua brass.

Thought of that and the final headspace fit of your brass to that chamber. Know nothing about Alpha Dasher but reads like a pre-formed case maybe.

I don't turn necks but the case wall thickness is 10-11 thou. The Alpha is a formed factory case

 

[Nightraider]

I don't turn necks but the case wall thickness is 10-11 thou. The Alpha is a formed factory case

All of my Dasher barrels are .275" neck diameter. For this very reason, the neck clearance isn't enough.

 

[shoot4fun]

I don't turn necks but the case wall thickness is 10-11 thou. The Alpha is a formed factory case

Strange, as all my 200 pieces of Alpha 6 Dasher brass are on the order of .013 thickness. I did a skim turn on them and my loaded round is .268 (not that is AFTER the neck turn). If they were .010-.011 as you say a loaded round would be .266 at the most.
Also, you note the fired case neck diameter and say it should be larger because of your chamber size. not necessarily so due to "spring back". There is really not a issue with your fired neck diameter in my mind.
Primary extraction means (if we are talking same lingo) that when the bolt is lifted past a certain point you see it begin to move rearward just enough to break the case loose from the chamber? Do you actually see the Primary extraction working properly but just cannot pull the bolt back once the bolt lugs are unlocked fully?
I also get from your component description that the action is a long action? Why? Do you feed from a magazine or single feed the rounds?

 

[Snipers World]

Strange, as all my 200 pieces of Alpha 6 Dasher brass are on the order of .013 thickness. I did a skim turn on them and my loaded round is .268 (not that is AFTER the neck turn). If they were .010-.011 as you say a loaded round would be .266 at the most.
Also, you note the fired case neck diameter and say it should be larger because of your chamber size. not necessarily so due to "spring back". There is really not a issue with your fired neck diameter in my mind.
Primary extraction means (if we are talking same lingo) that when the bolt is lifted past a certain point you see it begin to move rearward just enough to break the case loose from the chamber? Do you actually see the Primary extraction working properly but just cannot pull the bolt back once the bolt lugs are unlocked fully?
I also get from your component description that the action is a long action? Why? Do you feed from a magazine or single feed the rounds?

I'll double-check wall thickness but with the 109 hybird I am at .270 loaded OD. I'm aware that math is a little odd if the bullet is 243 and 11 on each side so I'll double-check but I'm 100% positive the loaded case OD is .270 - .2695

We are on the same page on primary extraction I can physically see bolt start to move rear at top of open and once the lugs are unlocked I cannot pull the bolt back.

I single feed rounds and chose the LA for flexibility in cartridges/ uses for action in future.

 

[JFrank]

How did you determine that 32 grains was the correct load ?

 

[divingin]

Is the stickiness repeatable by re-chambering a fired piece of brass? If so, can alleviate it by sizing without a bushing (which would imply it's expansion in the case body or base to datum measurement)? Can you alleviate it by running the bushing but not sizing the body (short stroke the brass into the sizing die)? Might give you a clue as to where the problem is occurring.

 

[Sheldon N]

My gut is telling me that your primary extraction is not actually performing the proper function of primary extraction. I have a hard time imagining how the case could be pulled back the amount of primary extraction with no resistance then all of a sudden become extremely stuck. With the case body taper the only thing left stuck would be the case neck. Perhaps it's something to do with extractor geometry and rim dimensions because you're running Dasher in a long action. The bolt faces are the same though so I don't know how that would be possible.

That being said, I know of friends who have had to turn necks on Alpha brass with a .272 chamber because it's just not enough clearance.

Do you have the capability to turn a neck or two and test?

 

[shoot4fun]

I'll double-check wall thickness but with the 109 hybird I am at .270 loaded OD. I'm aware that math is a little odd if the bullet is 243 and 11 on each side so I'll double-check but I'm 100% positive the loaded case OD is .270 - .2695

We are on the same page on primary extraction I can physically see bolt start to move rear at top of open and once the lugs are unlocked I cannot pull the bolt back.

I single feed rounds and chose the LA for flexibility in cartridges/ uses for action in future.

My normal load for 6Dasher in Lapua Brass with 105 grain bullets is 32.7 Varget with a CCI450 primer. Yesterday was my first outing with the Alpha brass and I had zero issues with extraction/ejection with my Curtis Vector action using Magpul AICS mags. NOTE that I saw extractor swipe along with flattened primers on my brass with 32.2 Varget, 105 Hybrid and CCI450. I have taken no measurements of case head expansion or otherwise yet but I feel like more pressure is going to be generated with the Alpha brass for a couple reasons. First of all, it weighs (at least mine) quite a bit more than Lapua formed from 6BR blue box brass and has a much larger flash hole. I feel somewhat tempted to back up to the CCI400 primer to see if that lowers pressure without giving up performance. My shooting session was on steel only but the EPS 106 grain bullet 10 off the lands with 32.2 Varget and CCI450 shot a very tight cluster of five shots under 1.5" at 300 yards. I also shot some 110 A-Tips along with the Hybrids I already mentioned. I did not have a chance to shoot with my chronograph so have no idea the velocities achieved but found zero at 300-500 yards with these loads to be within .1 mrad of my usual 32.7 load at same distances.

 

[DJB]

I had that problem a few years back. Turned out to be wrong headspacing. First i was not pushing the shoulder back enough. Then I end up pushing the shoulder back too far. About .005. I full resize my cases, and set the shoulder back about .002. That took care of the hard bolt lift. DJB

 

[sharpdoug]

This maybe out of left field but...a friend of mine had a .223 built for his daughter and it had the same extraction problem your having. The chamber had a scratch in the body of the chamber from the reamer. Insertion of the case was perfect, bolt lift was fine, it just required a mallet to remove the case from the chamber. Re-reamed the chamber, checked for deformation and scratches found none, works perfectly now. Just a thought. DK

 

[shoot4fun]

Not in left field at all. I recently saw the same thing in a shooting buddy's rifle. Oddly, it was a 223 as well.

 

[foxguy]

Sounds like some case measurements need to be taken on new vs fired brass 200 line just above the web, and just below the shoulder body junction. And re-measure these on resized brass.

I would measure the shoulder position on new brass and on fired brass. Just so you know how much the shoulder is or isn't expanding.

On fired brass I would insure I was bumping the shoulder back .002 when resizing?

I have had this problem on fired brass when the case wasn't resized bumping the shoulder back a couple thousands. (Just neck sizing on once fired brass.)

 

[Chuckhunter]

I have a Berger Manual and their Max load for a 108Gr. bullet with Varget in a Dasher is 31.3 and the starting load is 26.5Gr's. Personally I would go back and start at 27Gr's and work back up until you experience extraction difficulty. 109 Hybrids may have a lot more bearing area than some of their other bullets like VLD's and standard match bullets. Your lot of Varget may be a little on the Hot side and the internal Volume of the Alpha Brass is probably different than the Lapua, might just be the perfect storm. If 32Gr's is as low as you have been, I'd go low and work back up. Easiest, cheapest, thing to do first. If it doesn't work, you may have more serious problems. Also ditto what foxguy said.

 

[Snipers World]

Hey guys thanks for all the help. I came out and fired some cases today at a real light load of 30.5gn to see what would happen. I noticed some unusual markings on my brass the whole way down the body and above the .2 line.

 

[shoot4fun]

Hey guys thanks for all the help. I came out and fired some cases today at a real light load of 30.5gn to see what would happen. I noticed some unusual markings on my brass the whole way down the body and above the .2 line.

If you have access to a bore scope you should take a look at the chamber. It is quite possible what you describe is caused by a deep scratch or gouge in the chamber. Also, you post got me thinking about the effects of my outing with Alpha brass so I measured the brass for excess expansion at the 200 line. I'm happy to say I saw only .001 expansion there.

 

[swd]

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