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Nucleus Light Primer Strikes

So just got back from my smith's and got a little education.

The formula he uses is one he and Jerry Stiller came up with about 12-15 years ago to ensure sufficient FP energy for reliable ignition with most any primer. The formula is quite simple in that you take the spring rate in pounds and multiply it by the FP travel to the bolt face. So in my case I have 0.194" of total travel minus the 0.035" protrusion = 0.159" x 16-lbs = 2.544 . He refers to this as the Power Factor

Based on the testing they did he said they found that the optimal combination is when you get a power factor of around 4 or just a little over. Anything lighter than 3.75 and you start risking the possibility of light primer strikes or cold fires from primers with harder/thicker cups, and anything higher than 5 you just have a lot of wasted energy.

So if we take that basic formula and work backwards we can determine the required spring rate for optimal ignition the given amount of FP fall.

4 / 0.159 = 25.157 (coincidence?)

Now I know someone will ask, "What about sear drag?" Well, according to him so long as it's not more than 4 or 5-lbs. you really don't need to adjust or account for it.

We also discovered that a 24# long-action Savage FP spring is 0.010" too small on the ID to fit over a Nucleus firing pin. Was worth a shot!
 
Yes. I’ve had issues with CCI450’s, Fed 205’s, Fed 210’s and factory FGMM 6 creedmoor (which uses Fed primers).

Besides the lack of ignition, I was also shipped a LH bolt face as a spare with my RH actions.

If anyone is looking for an action, let me know. I guess I’m stuck with one of these since I’ve got barrels spun up to use the shouldered barloc, but I’m not planning on using the second one that is unfired, or any future ARC actions for that matter.
 
I'm having an opposite effect and getting cratering with Lapua srp; cci 450; h4350 (all charge weights); TT Diamond. I'm going to try new brass and a new box of primers to compare. I've read some things about the fp hole being slightly larger on remy 700 bolts which can cause this, so maybe that is all it is. There doesn't seem to be any signs of excessive pressure, I've measured case heads against factory Hornady and the are the same. The factory loads aren't cratering however.

View media item 901
The nuke uses a small firing pin. The light firing pin spring may be exasperating the cratering. I’d be curious if it goes away with the 25lb spring.
I’ve got pretty much the same issue as you but I’m running rem 7.5 primers vs. 450s. It craters 95% regardless of charge weight.
 
The nuke uses a small firing pin. The light firing pin spring may be exasperating the cratering. I’d be curious if it goes away with the 25lb spring.
I’ve got pretty much the same issue as you but I’m running rem 7.5 primers vs. 450s. It craters 95% regardless of charge weight.

View media item 902
Apparently this is possibly a new issue then. I got the above reply from arc. This past weekend were the first shots through mine. I’m going back out this weekend and will change out some components cci41 , starline brass, new lapua etc and see how it goes. I don’t care about the cratering if it’s only superficial, just haven’t had this before.
 
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This is what my brass looks like. All of them fired and no cratering, using BR-2 primers. My rifle is number 11, so I’m assuming it has the 16# spring in it.

2A38A7F7-624D-4A12-AC0F-B80F4C104658.jpeg
 
The 0.183" number might be incorrect as I was going from memory of what my 'smith said 6-months ago.

If I measure off the back face of the firing pin (where you would screw in the hex bolt to compress the spring) to the rear face of the bolt shroud I get the following:

Dropped (fired) = 0.312"
Cocked with bolt up = 0.128"
Cocked with bolt down = 0.118"

That puts the travel at 0.194" with the trigger in place.

With no trigger I get the following:

Uncocked (bolt down) = 0.312"
Cocked (bolt up) = 0.118"

That's a difference of 0.194"

Heading out to my smith's later this afternoon and plan on taking it with me just to verify numbers and see if maybe he has a spring that will work in this thing. Not likely, but worth a shot.

There's enough of a disparity between our numbers I remeasured my unassembled long action Nucleus as soon as I got home.

Without a trigger installed (which typically provides a little overcocking for additional energy) the firing pin has 0.255" of travel (0.300" firing pin tail to shroud in the fired position, 0.045" tail to shroud firing pin cocked.)

If I unscrew the firing pin shroud one one full rotation (the thread pitch for the threads between the firing pin shroud and the bolt body is 20 threads per inch, so 0.050" per rotation) and reinstall the lock pin, the action will still go together and function seemingly as normal, but with significantly decreased firing pin travel because the shroud and firing pin are now an additional 0.050" rearwards from the sear and the cocking ramps on the back of the bolt. With the shroud unscrewed a full turn from where it should be and then reassembled the firing pin tail to firing pin shroud measures 0.313" in the fired condition (nearly identical to your 0.312" dimension) and in the cocked position it's 0.106" for 0.207" firing pin travel. Again, very similar to your numbers.

Losing 0.050" of firing pin travel is a substantial amount of energy... and with my firing pin travel and depth from shroud dimensions at one turn out being very close to yours you may want to verify your firing pin shroud is fully screwed in and it's not assembled a full turn out. Screw the firing pin shroud all the way in until it bottoms against the back of the bolt body and then unscrew it only until the lock pin hole in the firing pin shroud lines up with the notch for the lock pin on the back of the bolt body. There should only be a very small gap between the firing pin shroud and the back of the bolt body when it's assembled.

If your firing pin shroud was indeed assembled one turn out further than it should have been, you'll probably also have to reset the firing pin protrusion at this point.

Hope that's all your problem is, it would be a simple fix!


So just got back from my smith's and got a little education.

The formula he uses is one he and Jerry Stiller came up with about 12-15 years ago to ensure sufficient FP energy for reliable ignition with most any primer. The formula is quite simple in that you take the spring rate in pounds and multiply it by the FP travel to the bolt face. So in my case I have 0.194" of total travel minus the 0.035" protrusion = 0.159" x 16-lbs = 2.544 . He refers to this as the Power Factor

Based on the testing they did he said they found that the optimal combination is when you get a power factor of around 4 or just a little over. Anything lighter than 3.75 and you start risking the possibility of light primer strikes or cold fires from primers with harder/thicker cups, and anything higher than 5 you just have a lot of wasted energy.

So if we take that basic formula and work backwards we can determine the required spring rate for optimal ignition the given amount of FP fall.

4 / 0.159 = 25.157 (coincidence?)

Now I know someone will ask, "What about sear drag?" Well, according to him so long as it's not more than 4 or 5-lbs. you really don't need to adjust or account for it.

We also discovered that a 24# long-action Savage FP spring is 0.010" too small on the ID to fit over a Nucleus firing pin. Was worth a shot!

Regarding that formula... here's the numbers for my 223AI short action Nucleus with the CG Mod 22 trigger

Total FP travel with the Mod 22: 0.276" (0.250" bolt only plus 0.026" overcocking with the trigger)
FP protrusion: 0.035"

With the 16# spring the "power factor" is (0.276 - 0.035) * 16 = 3.856
With the 19# spring it would be (0.276 - 0.035) * 19 = 4.579

So according that quick and dirty "power factor" formula your gunsmith used, either the 16# spring or 19# spring are fine in my action & trigger combo, and a 16.59# spring would yield a "perfect" 4 for the power factor.
 
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M
There's enough of a disparity between our numbers I remeasured my unassembled long action Nucleus as soon as I got home.

Without a trigger installed (which typically provides a little overcocking for additional energy) the firing pin has 0.255" of travel (0.300" firing pin tail to shroud in the fired position, 0.045" tail to shroud firing pin cocked.)

If I unscrew the firing pin shroud one one full rotation (the thread pitch for the threads between the firing pin shroud and the bolt body is 20 threads per inch, so 0.050" per rotation) and reinstall the lock pin, the action will still go together and function seemingly as normal, but with significantly decreased firing pin travel because the shroud and firing pin are now an additional 0.050" rearwards from the sear. With the shroud unscrewed a full turn from where it should be and then reassembled the firing pin tail to firing pin shroud measures 0.313" in the fired condition (nearly identical to your 0.312" dimension) and in the cocked position it's 0.106" for 0.207" firing pin travel. Again, very similar to your numbers.

Losing 0.050" of firing pin travel is a substantial amount of energy... and with my firing pin travel and depth from shroud dimensions at one turn out being very close to yours you may want to verify your firing pin shroud is fully screwed in and it's not assembled a full turn out. Screw the firing pin shroud all the way in until it bottoms against the back of the bolt body and then unscrew it only until the lock pin hole in the firing pin shroud lines up with the notch for the lock pin on the back of the bolt body. There should only be a very small gap between the firing pin shroud and the back of the bolt body when it's assembled.

If your firing pin shroud was indeed assembled one turn out further than it should have been, you'll probably also have to reset the firing pin protrusion at this point.

Hope that's all your problem is, it would be a simple fix!




Regarding that formula... here's the numbers for my 223AI short action Nucleus with the CG Mod 22 trigger

Total FP travel with the Mod 22: 0.276" (0.250" bolt only plus 0.026" overcocking with the trigger)
FP protrusion: 0.035"

With the 16# spring the "power factor" is (0.276 - 0.035) * 16 = 3.856
With the 19# spring it would be (0.276 - 0.035) * 19 = 4.579

So according that quick and dirty "power factor" formula your gunsmith used, either the 16# spring or 19# spring are fine in my action & trigger combo, and a 16.59# spring would yield a "perfect" 4 for the power factor.


My left hand short action nucleus measures .205 firing pin travel after I’ve removed some travel from the cocking piece so his numbers are only about .020 off mine perhaps the long action differs from short actions
0.292” fired
0.086” cocked both measured from rear of shroud to end of firing pin best I can with caliper mine has run well so far with large primers as is
 
My left hand short action nucleus measures .205 firing pin travel after I’ve removed some travel from the cocking piece so his numbers are only about .020 off mine perhaps the long action differs from short actions
0.292” fired
0.086” cocked both measured from rear of shroud to end of firing pin best I can with caliper mine has run well so far with large primers as is

Just went and remeasured my short action...

Bolt only:
0.298 fired, 0.045 cocked = 0.253" FP travel
(Both dimensions and overall travel of the bolt only are within 0.002" of my long action which was 0.300" / 0.045")

Bolt in the action with CG Mod 22 trigger:
0.298 fired, 0.024 cocked = 0.274" FP travel

If both the bolt body and firing pin shroud were threaded in a lathe without controlling the lead in point of the threads, I would expect variation in the fired/cocked/FP travel dimensions between my two bolts based upon where the threads time in the assembled condition. But with both my long and short action bolts measuring within 0.002" for firing pin tail to shroud clearance and overall FP travel I'm guessing ARC is controlling the lead in point of the threads on both the bolt body and firing pin shroud (thread milling, possibly) to ensure they time correctly in the assembled condition to have the proper amount of firing pin travel when assembled.
 
I went to get cci 450s for the srp brass I have arriving after work and lgs was closed I may just order a few thousand federal primers I have not seen many if anyone having issues with them I wanted to go with 450s because that’s all I can get locally but if it saves me some trouble I will have to hold off

So before i go that route I haven’t seen anyone mention it, but has anybody had problems with there nuke and fed 205 small primers and failures?

Havent had a single fed 205M primer fail.
 
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My nucleus has cratering too.
F3BB94F5-CA4F-446D-8B56-CA2E7AACE7E9.jpeg

This is with factory ammo.
4BA97002-46F2-46FD-94E5-5E265E101107.jpeg

These are my reloads. Recipe is 6mm Creed Lapua SR brass using a cci 450, 41.25 grr of 4350 behind a 105 Berger VLD or a 108 eld.

I don’t care though. I get cratering with my savage and RPR. I don’t consider it an issue until a primer pops.
 
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Just went and remeasured my short action...

Bolt only:
0.298 fired, 0.045 cocked = 0.253" FP travel
(Both dimensions and overall travel of the bolt only are within 0.002" of my long action which was 0.300" / 0.045")

Bolt in the action with CG Mod 22 trigger:
0.298 fired, 0.024 cocked = 0.274" FP travel

If both the bolt body and firing pin shroud were threaded in a lathe without controlling the lead in point of the threads, I would expect variation in the fired/cocked/FP travel dimensions between my two bolts based upon where the threads time in the assembled condition. But with both my long and short action bolts measuring within 0.002" for firing pin tail to shroud clearance and overall FP travel I'm guessing ARC is controlling the lead in point of the threads on both the bolt body and firing pin shroud (thread milling, possibly) to ensure they time correctly in the assembled condition to have the proper amount of firing pin travel when assembled.

So fired we are only .006” apart but you have significantly more on the back end a lot of the variation must be in where the trigger sits I’m using a tt diamond as I said I have modified my cocking piece to smoothen things up a bit but not .050 are you using the same trigger in your long and short actions?
 
My nucleus has cratering too.
View attachment 7033309
This is with factory ammo.
View attachment 7033313
These are my reloads. Recipe is 6mm Creed Lapua SR brass using a cci 450, 41.25 grr of 4350 behind a 105 Berger VLD or a 108 eld.

I don’t care though. I get cratering with my savage and RPR. I don’t consider it an issue until a primer pops.


Looks like my brass, my rifle so far is shooting lights out. This is a 12 shot group ranging from 2600-2760. All of the craters seem the same at eye measurements. I’m doing some more tests tomorrow, but hoping it’s just a slightly larger fp hole causing the flowing of the primer, and nothing to worry about. No other pressure signs that I can gauge either. This has been my only concern to this point, the action is running perfect for my purposes.
View media item 903
 
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So fired we are only .006” apart but you have significantly more on the back end a lot of the variation must be in where the trigger sits I’m using a tt diamond as I said I have modified my cocking piece to smoothen things up a bit but not .050 are you using the same trigger in your long and short actions?

No trigger in my long action at the moment, it's just a bare action. But the bolt by itself with no trigger has 0.255" of firing pin travel, I'd expect a little additional FP travel once a trigger is installed since it will probably have some overcocking.

Your 0.086" cocked / bolt open dimension makes me think your firing pin shroud might be 1 turn too far out from the bolt body... with the threads being 20 TPI one turn is 0.050". Both my long and short actions are right at 0.045" firing pin tail to firing pin shroud with the bolt handle in the open position. What's the measurement on your action with the bolt handle open and also with the bolt closed but the firing pin cocked?

On my assembled short action with the CG Mod 22 that 0.045" dimension with the bolt handle open drops to 0.024" with the bolt closed and the firing pin cocked because the CG Mod 22 has some overcocking that yields additional firing pin travel when closing the bolt. Can you take a picture showing the gap between the firing pin shroud and the back of the bolt body with the bolt handle in both the open and closed positions?
 
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Yes I can and I have tried to tighten the shroud twice now after seeing your post I bottom out before I can make another revolution to get the detent back in bot I’m at .065” bolt open and/or out of the action
image.jpg


.086” is cocked with the bolt in the closed position

If you didn’t have exactly the same measurement between the two actions I would say your firing pin may have come unscrewed from the cocking piece only because that happened to me earlier on I only found out when I used the little disassembly bolt and washer to take the bolt apart and noticed it spinning but maybe changes have been made mine is a preorder action from some of the first batches I believe
 
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Yeah, that gap is quite a bit more than my two bolts and certainly not helping your firing pin travel, but if you can't get another full rotation out of it I'm not sure what to do. Does the shroud bottom out on the back of the bolt before you can get another full rotation out of it, or does it stop rotating before all the gap is gone like something else is stopping it from threading in the rest of the way?

For reference, here's one of mine... note how much less the gap is.

Firing pin cocked / bolt open position (same condition as your picture above)

IMG_20190226_201348.jpg



Firing pin dropped / bolt closed position. The gap increases 0.010" in this position as the shroud "unscrews" relative to the bolt body as the bolt body rotates 72 degrees from the bolt open position to the bolt closed position.

IMG_20190226_201325.jpg
 
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You bring up an interesting point first of all there is .035 gap there in that picture so if one rotation=.050” I don’t have enough but it does shoulder right up there is nothing stopping it other than it runs into the bolt body before I can get back around but the interesting part to me is being a left handed action the body is tightening into the shroud when I close my bolt handle opposite yours which explains why I lose travel upon closing where you gain travel when closing , but none the less I have less travel overall I have an unmodified cocking piece in my parts collection I will have to install it tomorow and see what it gave me I dont remember how much material I took off
265121C2-21DF-4B1F-9959-3FF7B7E0CF6F.jpeg


Photo with firing pin in the fired position
 
Good point on the RH vs LH action differences, if ARC used RH threads between the bolt body and firing pin shroud for the left hand actions the shroud to bolt gap on your LH action will decrease 0.010" when you close the bolt.

Based on my limited sample of 2 Nucleus actions, my hunch is you should have approximately 0.250-0.255" of firing pin travel with only the cocking ramps on the back of the bolt body from the bolt closed to bolt open positions. Anything significantly less than that would lead me to believe the shroud is unscrewed further out from where it should be-- and if you can't get that extra revolution tighter out of it before it bottoms out there's the possibility your bolt and shroud have thread timing error stacking going on (or a little too much material on the flange of the firing pin shroud facing bolt body) preventing you from getting it that extra turn tighter and picking up additional firing pin travel.

I suppose that's one advantage to a bayonet-style bolt and firing pin shroud interface like an AI or Bighorn TL3, there's no worries about thread timing messing with the relationship of the firing pin shroud to the bolt body like a threaded interface-- provided the bayonet lugs on the firing pin shroud are in the correct place and the receiving grooves in the bolt body are in the correct place. There also won't be any change in distance between the two components as the bolt rotates relative to the firing pin shroud as you close and open the bolt.

Be interesting to have people post the bolt open vs bolt closed firing pin tail to shroud dimensions with the bolt out of the action and also in the action with the trigger in place and see if there's a trend between actions not having light strike problems and actions having light strike problems.
 
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I suppose I am one of the lucky ones, (serial number 25, so I have one of the very early ones) I started out with the 16lb spring but have since swapped to the 19lb just for a piece of mind. However I have not had any issues with light primer strikes on either spring. I am running a Timney Calvin elite, and have not tried other triggers. It really surprises me to see all the issues people are having. I know I would be frustrated as hell!

From reading this thread it looks to be all over, no real item that is causing the issues. I have tried only CCI BR4 and CCI 450 primers but have no issues with either of those as well. I get a solid hit with little to no cratering as some have shown photos of above.
 
Update...

First, I got an email from ARC yesterday and they are sending me out the 25# spring. Might go ahead and buy a 19 and 22# just to have on hand to experiment since they're inexpensive and I have a feeling the 25# is going to make the bolt lift worse than that of a Savage.

Second, reading Anderson_A's post and seeing his pictures I can say I have the same issue with the shroud not being properly aligned when screwed all the way down. Mine is about 1/4 turn (90 degrees) short of allowing the shroud plunger pin to line up with its corresponding slot in the bolt sleeve.

Now here's where it gets interesting...

Because if this I always backed off the shroud the 3/4 turn necessary to get the pin and slot go align properly, thus resulting in the 0.050" shorter firing pin travel as Kiba has pointed out. This is how I came to have the numbers I previously listed which were:

Cocked (bolt up) = 0.128"
Cocked (bolt down) = 0.118" (decocking 0.010" on close)
Fired = 0.312"
Total Firing Pin Travel = 0.194" (or 0.184" after decocking on close)

Now explain this because I sure as hell can't....

IF rather than backing the shroud off the 3/4 turn to get the pin and corresponding slot to align I only slightly unscrew the shroud a few degrees so that the cocking piece lug lines up with its ramp and then unscrew the striker disassembly screw I get totally different numbers. Note that at this position the shroud is 180 degrees out from where it needs to be and I have to muscle it around to get it properly orientated.

Here's the numbers I get when I assemble it in this fashion...

Cocked (bolt up) = 0.065"
Cocked (bolt down) = 0.075" (decocking 0.010" on close)
Fired = 0.295"
Total Firing Pin Travel = 0.230" (or 0.220" after decocking on close)

Everything ends up in the exact same place no matter which way it's assembled so I can't for the life of me figure out why it results in a 0.036" difference in firing pin travel. The 0.035" gap between the shroud and bolt sleeve that was noted by Anderson_A stays consistent with either assembly method. It's got me baffled!

So with 0.036" more firing pin travel I snuck out to the range today to see if it would make a difference and it sure did. Of the 45 rounds I had remaining of the 50 I originally loaded (other 5 rounds were those that fired out of 20 tried previously) all but three of them fired on the first hit. Two of those three never fired even with 5+ additional hits, while the third fired on the second hit. Still not perfect, but a LOT better than it was.

Kiba mentions the threads for the shroud and the difference in rotation direction for RH v. LH actions. My guess is that's why the RH actions are seeing 0.010" of overcock on bolt close while I'm seeing 0.010" of decock on close. Makes sense in my head at least. LOL
 
I can tell the difference between the 16lb and 19lb spring. In fact a measured it. Bolt lift force increased by 20%. @tomcatfan was there. A 25lb spring would be excessive IMO and and completely negate that “light bolt lift” the Nucleus is advertised to have.
 
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curious if anyone getting light strikes is using factory ammo?

I plan to roll my own when my JH shows up, but from previous posts from PVA it seems like a culprit could be primer seating issues. I know when I've had some issues with semi auto (pistols and rifles) I always went back to a box of factory ammo to see if I could replicate the issues and figure out if there was possibly an issue with my load or process instead of the rifle/pistol. Sometimes the issue was hardware (loose gas key in an AR) sometimes ammo (powder charge on an FNX45). Helps to narrow down where the issue is coming from...
 
All, as far as the issue with screwing in the shroud, eventually that issue should be gone, because ARC told me that they planned to go to a tool less design. I saw it on the Mausingfield and the Archimedes. They are consolidating production for what they can across models is what I understand. Doesn't help us now.

I looked at all three of my Nukes, but couldn't exactly see what you all are talking about as far as how far you need to screw it in. I will have to go back through the comments and figure out what you are talking about there.
 
I looked at all three of my Nukes, but couldn't exactly see what you all are talking about as far as how far you need to screw it in. I will have to go back through the comments and figure out what you are talking about there.

When you have the screw/washer in the back of the bolt to compress the FP spring for disassembly/reassembly, we're talking about where the shrouds ends up when screwed all the way in until it stops.
 
In this first pic the shroud is screwed all the way in until it bottoms out on the bolt sleeve. Notice the slot for the plunger pin, and that there's no hole in the shroud there for said plunger pin.
DSC02311.JPG


Now in this pic I have backed the shroud off to align the plunger pin hole with the plunger pin slot in the bolt sleeve. Notice the gap between the shroud and sleeve - that's the 0.035" gape that's been mentioned a few times now. When I put the plunger pin back in and release the disassembly screw in this position I end up with the shorter firing pin travel number.
DSC02312.JPG



This pic shows how the cocking piece lug is just past the matching ramp slot in the bolt sleeve when the shroud is screwed all the way down until it stops. Also notice the plunger pin hole in the shroud. In this position the plunger pin will fully extend and thus lock the bolt preventing it from being able to rotate as the pin gets wedged up against the block of the bolt handle.
DSC02313.JPG



This last pic shows the shroud just backed off a little bit to allow the cocking piece lug to align with the cocking ramp slot in the bolt sleeve. Also note that the plunger pin hole in the shroud is now over the bold handle so it can't fully extend if assembled in this position. If I put the plunger pin back in and remove the disassembly screw while in this position and then muscle the shroud around to be properly oriented (here it's 180 degrees out) I somehow gain 0.036" of firing pin travel even though the gap between the shroud and bolt sleeve ends up being the same at 0.035".
DSC02314.JPG
 
In followup to my previous post, I'm happy to report 100% ignition during today's range trip. Nucleus action running a pre-production 25# spring and Huber Concepts trigger.

Conditions were a cold 14.8 deg. F, and I fired 50 rounds off the tripod, gathered chronograph data, and shot four different primers; CCI BR-2s and 250s in Nosler brass with several firings and CCI BR-4s and 450x in virgin Lapua brass. I'm going to load another 100 rounds for some additional near-term shooting, but it seems like the initial light-strike problem is resolved with proper firing pin nut setting and the 25# spring.

IMG_2838.jpeg
 
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How heavy was the bolt lift with the 25# spring?

When initially testing the action in the shop it felt a bit heavy, but after getting to the range and shooting 20 rounds, it struck me that I hadn't even noticed the lift. After paying closer attention, the best way to describe this combination is smooth yet noticeable and distinct without feeling like it needs to be muscled... if that makes any sense.
 
Tagging in. I’ve had 2 light strikes in 60 test rounds with the 19# spring. TT ARC today and they’re sending a 25lb spring. I hope this resolves the issue. Does anyone know what other actions or MFGs use in rated springs. I’m running Peterson SRP Brass, CCI 250’s.
 
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Does anyone know what other actions or MFGs use in rated springs.

From my understanding that is relative to a specific action so comparing spring weights across actions is not meaningful data.

There’s a post in this thread that touched on power of the firing spring strike which sounded like more meaningful data... but math and stuff. I just expect mine to feel good and function reliably.
 
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I'm having an opposite effect and getting cratering with Lapua srp; cci 450; h4350 (all charge weights); TT Diamond. I'm going to try new brass and a new box of primers to compare. I've read some things about the fp hole being slightly larger on remy 700 bolts which can cause this, so maybe that is all it is. There doesn't seem to be any signs of excessive pressure, I've measured case heads against factory Hornady and the are the same. The factory loads aren't cratering however.

View media item 901

Range update. Stripped the bolt and ran it through ultra sonic. Shot new lapua brass with new box of 450’s and some starline with 41’s. Same deal. No light strikes and everything went off. I’m gonna chalk up the cratering as a nuance in mine and hopefully doesn’t start doing the light strikes. I found a great node with sd of 3.1 and es of 10 no other signs of pressure. I have a local match in April so that should be a good test.

View media item 910
 
All, as far as the issue with screwing in the shroud, eventually that issue should be gone, because ARC told me that they planned to go to a tool less design. I saw it on the Mausingfield and the Archimedes. They are consolidating production for what they can across models is what I understand. Doesn't help us now.

I looked at all three of my Nukes, but couldn't exactly see what you all are talking about as far as how far you need to screw it in. I will have to go back through the comments and figure out what you are talking about there.

One thing to note here before anyone goes screaming to ARC about the shroud to bolt body gap causing light strikes... the gap between the firing pin shroud and the back of the bolt *can* vary between bolts-- but unless the shroud is so far back the firing pin can't protrude through the bolt face 0.035" before the cocking piece bottoms out in the shroud and/or the shroud is so far back the locking plunger can't engage the notch in the back of the bolt body, the gap amount between the bolt and shroud in the assembled condition really doesn't matter and shouldn’t be used as an indicator of a problem.

The forward motion of firing pin and attached cocking piece is limited by the shroud so the firing pin doesn't launch across the shop when you remove it from the bolt body-- but only when it's removed from the bolt. The forward movement of the firing pin and cocking piece when installed in the bolt is limited by the castle nut and washer on the front of the firing pin which controls firing pin protrusion.

The amount of rearward movement of the firing pin and cocking piece during bolt cycling is a function of the cocking ramps on the back of the bolt body and also the trigger sear in the closed & cocked position.

The shroud keeps the firing pin, cocking piece, and spring retained when you remove it from the bolt; so the shroud itself can limit the forward movement of the firing pin-- but normally only when removed from the bolt. If the shroud was unscrewed too far from the bolt body when assembling the bolt, the firing pin would not be able to move forward far enough to protrude from the bolt face and ignite the primer as the cocking piece and FP forward motion would be stopped by the cocking piece bottoming out in the shroud. Having the shroud unscrewed too far may also prevent the shroud locking plunger from engaging the notch in the back of the bolt-- so as long as either of those conditions aren’t happening it doesn’t matter if the gap between the back of the bolt and the firing pin shroud is 0.020" or 0.070" when assembled.

The real question here is why both of my actions have around 0.253" of firing pin travel without the influence of the trigger & sear from the bolt open to bolt closed positions (with the FP protrusion set at 0.035") while other people are reporting their actions only have about 0.195-0.205" of FP travel in the same conditions. That “lost” 0.050" of FP travel is robbing the energy needed to ignite the primers reliably. Measuring the FP travel from the back of the shroud to the tail of the firing pin will show a 0.010” difference between LH and RH actions, but that measured 0.010” difference is only because the shroud moves 0.010” relative to the bolt body over 72 degrees of bolt rotation-- and that 0.010” shroud movement between bolt closed and bolt open is opposite in an LH action compared to an RH action. The *total* amount of FP travel from bolt closed to bolt open should be the same between RH and LH actions as that’s controlled by the FP protrusion setting, cocking ramps and cocking piece. Without seeing a "problem" action in person I can only guess as to possible causes limiting the firing pin travel between bolt open and bolt closed...

1. incorrect / too shallow cocking ramp cuts on back of bolt body. However, if the cocking ramps were cut too shallow that could limit the forward FP movement during firing as the cam surfaces on the cocking piece would hit the bottom of the ramps and stop the firing pin before the firing pin protrudes from the bolt face.

2. back/flat portion of bolt body cut too short which would limit FP cocking on bolt opening since that would effectively shorten the cocking ramps. However, this would only limit the amount of FP cocking on bolt open-- with a trigger installed, an action with this issue would probably have a *lot* of overcocking on close from the sear. This condition should still produce adequate FP travel from cocked to fired... unless the sear on your trigger is way too short or you significantly shortened the sear engagement surface on the cocking piece to reduce the amount of overcocking / “bump” on close.

3. trigger pins located too far forward / trigger sear too short / a combination of both. While this would limit FP travel from cocked to fired, it would limit FP travel *only* with the trigger in the system... the bolt itself should still have approximately 0.250" FP travel from the bolt open to bolt closed positions with the bolt removed from the rifle. For example say the trigger sear was 0.075" too far forward; you should see and feel that 0.075" of FP drop during bolt close before the cocking piece engages the sear and catches the firing pin.

4. Firing pin too long or back of cocking piece too short (the surface of the cocking piece that the firing pin tightens against.) If either of these were the case, even if the FP protrusion was correctly set to 0.035", the firing pin being too long or the back of the cocking piece being too short would place the cocking piece further to the rear away from the cocking ramps and sear, so the total amount of FP travel both with and without the trigger would be reduced since the cocking piece would be held further back from the cocking ramps and also from the sear.

Those are a few ideas I had while looking at my actions... and they're all just ideas without being able to look at and measure a "problem" action in person.

I really would like to see the root cause of this light strike issue identified and resolved for those who are experiencing it to satisfy my curiosity… and also because I can only guess at the frustration level for those experiencing it.
 
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Update,
I just emailed ARC inquiring on the 25 lb firing pin spring and they are shipping me one. They are available now, but still no official announcement.
I went from 20 % ignition to 98% ignition by installing a 19 lb spring while still using a Timney trigger. 78% increase of ignition rate with 3 lbs increased force. 25 lb spring increased preload to 9 lb over stock spring should make this 100% ignition regardless of sear friction or sear length of the Timney.
In the case of my rifle I have the following going against me. I live and shoot on the gulf coast and the salt air forces a need for preservative function of oil. read this as thick ass oil! I also have a personal salinity and acidity of perspiration that is horrid and rusts stainless barrels with only a touch. 98% humidity never helps with this along with 80 degree weather in December. We sweat in the south!
I have to lube everything, I do use dry lube where possible" Coated firing pin and bolt" but the original spring removed has a slight dusting of rust during its stay in my parts cabinet. This was not oiled as per ARC instructions. I have a dry Lock graphite based bube on the new 19 lb spring. The 98% success rate was with the dry lubed spring. Something also was noticed that the firing pin was covered with oil after lubing the outside of the bolt for smoother cycling. I would suggest that using a 25 lb spring would be best due to the following. Oil will get to the firing pin and over time will thicken and lower firing pin speed and force. The heavier spring should help to decrease velocity ES due to more consistent primer strikes. This will be compared to previous firings across 2 chronographs and the results posted. Also this rifle is shooting a 7mm-300 wsm wildcat and these shots are for fire forming brass and load development. This can make for a softer strike especially if there is excessive headspace. Mine only gained .0015" and was a snug bolt close on fired cased before bumping the shoulder back .0015". Also I use CCI-BR2 primers that are a harder cup for the firing pin to indent, but much more forgiving for cratering and piercing.
I did a test with a borrowed Bix and Andy with a low .036" sear to reduce the drag and the sear was longer than the Timney and gave a longer power stroke with less sear friction. This combo worked 100%, and if you follow Teds suggestions as to correct the light strikes along with a trigger that has similar sear length and clearance the problems should go away barring lube finding its way to the firing pin. If you want better odds, get the 19 lb spring with the above procedures worked well, but might need regular bolt teardown and cleaning."Every time you shoot it". The 25 lb should work with all triggers and sparing lubrication unless your action has something else going on that is not what the rest of us are having issue with.

I totally understand that Ted designed this action and why he went with the smaller firing pin and lighter spring, It just might not work every time with issues of oil thickness/drag. different triggers with higher and or shorter sears that drag and or reduce the power stroke of the firing pin. primer seating heights, primer construction, factory or reloaded ammo, etc.
 
TT ARC today and am sending them my LH bolt for them to inspect and remove the 19lb spring put in the 25 lb. i could do it but I want them to inspect all of it!
 
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After 13 months of reading and waiting I finnally shot my preorder nucleus today. I am using a tt diamond and a Barloc barrel nut setup with a 6mm creed criterion prefit. Today was small sample but I fired 33 rounds of factory hornady eldm and black without any issue. My action still has the original 16 lb spring, I did strip the bolt down and degrease everything throroughly. I am planning to do a local match Sunday and get another 70 or so sounds through it, I’ll report back if any issues. so far so good, I am very pleased with the whole setup
 
Preordered, Nucleus SN 55, received in July'18. 340 rounds total, 40 of those today in 20*F weather. No failures to ignite. TriggerTech Diamond. Original 16lb spring. Cleaned/lubed the firing pin with Hornady 1shot and left it alone. No issues to date with this Nucleus fire control group.

 
Got my 25# spring in the mail today and installed it. Bolt lift is a bit heavier, but I can still lift it with one finger - though it takes noticeably more effort. Not as stiff as a factory Savage bolt lift, but not near as light as the lift on a properly trued & timed Savage.

If you're one of those who grasps the knob with your fingers rather than properly working the bolt with just your finger and thumb by rocking your hand you probably won't notice the difference.

Need to get some ammo loaded up before I can hit the range with it.
 
Am I missing something on striker disassembly? I see caught the video of how to remove the striker assembly from the bolt, but I must be missing how to remove the castle nut, firing pin, and spring from the shroud.
 
I have shot 75-100 rounds of factory 140 eldm in 20*F weather with the 16lb spring and TT special trigger with no issues.
Haven't cleaned the striker assembly either.
 
Am I missing something on striker disassembly? I see caught the video of how to remove the striker assembly from the bolt, but I must be missing how to remove the castle nut, firing pin, and spring from the shroud.

You have to remove the castle nut and the spring and take the striker and cocking piece out the back of the shroud. To remove the castle nut, use the big washer ARC sent with the action, slip it over the castle nut, compress the spring, and unscrew the castle nut.
 
You have to remove the castle nut and the spring and take the striker and cocking piece out the back of the shroud. To remove the castle nut, use the big washer ARC sent with the action, slip it over the castle nut, compress the spring, and unscrew the castle nut.
Never mind, I was overcompressing the spring thinking it needed more travel to unscrew.
 
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Did a brave thing today. Replaced my 19lb spring with the stock 16lb. Will run it in the WAR Rifles PRS match.

Pin and spring are bone dry. Cleaned with carb cleaner and dried in dehydrator. Spring actually creaks when I lift the bolt.

.031" firing pin protrusion.

When I got the rifle, I had fired about 400 rounds with the 16lb spring before I started having issues. I had never cleaned it, and noticed from day 1 that the pin drop seemed "lethargic". I cleaned and installed the 19lb spring and never had an issue. Today after cleaning and drying with the 16lb spring, the pin seems to drop with more aggression than when I first got the Nucleus.

Bolt lift difference to me is very noticeable. With the 16lb spring, I can lift without rotating rifle. With the 19lb spring, I have to have a firm grip on rifle and even then I often break position.

I'm going to test it out a few times before the match, as well as clean/dry immediately before match (and probably after first day).
 
Did a brave thing today. Replaced my 19lb spring with the stock 16lb. Will run it in the WAR Rifles PRS match.

Pin and spring are bone dry. Cleaned with carb cleaner and dried in dehydrator. Spring actually creaks when I lift the bolt.

.031" firing pin protrusion.

When I got the rifle, I had fired about 400 rounds with the 16lb spring before I started having issues. I had never cleaned it, and noticed from day 1 that the pin drop seemed "lethargic". I cleaned and installed the 19lb spring and never had an issue. Today after cleaning and drying with the 16lb spring, the pin seems to drop with more aggression than when I first got the Nucleus.

Bolt lift difference to me is very noticeable. With the 16lb spring, I can lift without rotating rifle. With the 19lb spring, I have to have a firm grip on rifle and even then I often break position.

I'm going to test it out a few times before the match, as well as clean/dry immediately before match (and probably after first day).

I noticed that after cleaning mine with carb cleaner that there is a very noticeable difference in how much apparent energy the firing pin is receiving compared to the way it was shipped. Granted, it had grease in lots of places it shouldn’t have when received, based on Teds provided drawings.
Still waiting on the 25lb springs as a safety measure, but I’ll be attempting to run it in a local match Saturday with the 16lb spring, provided that I don’t get any FTF when testing on Friday.
 
Is ted sending 19 and 25lb springs or is it something you guys are buying?
 
I asked for both, but the cs guy makes it sound like they’re only sending 25 lb ones out now. I hope they still send both.
 
Is ted sending 19 and 25lb springs or is it something you guys are buying?

Like everything, it seems to be a crap shoot. I was told “springs will be available for purchase” when I inquired.
 
Springs are available new bolt heads are coming blah blah blah. What’s the truth and the current status?
 
Did a brave thing today. Replaced my 19lb spring with the stock 16lb. Will run it in the WAR Rifles PRS match.

Pin and spring are bone dry. Cleaned with carb cleaner and dried in dehydrator. Spring actually creaks when I lift the bolt.

.031" firing pin protrusion.

When I got the rifle, I had fired about 400 rounds with the 16lb spring before I started having issues. I had never cleaned it, and noticed from day 1 that the pin drop seemed "lethargic". I cleaned and installed the 19lb spring and never had an issue. Today after cleaning and drying with the 16lb spring, the pin seems to drop with more aggression than when I first got the Nucleus.

Bolt lift difference to me is very noticeable. With the 16lb spring, I can lift without rotating rifle. With the 19lb spring, I have to have a firm grip on rifle and even then I often break position.

I'm going to test it out a few times before the match, as well as clean/dry immediately before match (and probably after first day).

Took it to the range today. 32 degrees out. 6 CM in Lapua brass and CCi450 primers.

Only fired 16 rounds but no failures. My magnetospeed is not functioning anymore so I was unable to see how consistent velocity was.

I plan on going to Peacemaker next wednesday for more testing. Anyone a member with a labradar?
 
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