Ramshot TAC 5.56 77gr OTM dirty case/accuracy question

Zatoichi66 · Aug 1, 2021

I’m using 1X LC brass, Nosler 77gr OTM and 24.5 grains of TAC with CCI 41 caps. The upper is a Compass Lake Engineering 20” Krieger 1/8 build (their SAM-R) with CLE chamber. I’m trying to replicate Black Hills Mk262 so i can save the few factory rounds i have, but still practice. After researching recipes, i settled on the above load & was astonished on how dirty the spent cases were. Accuracy was mediocre. My goal is accuracy & replicating Mk262 loads. At this time, my plan is to drop to 24.0 grains and increase by 0.2 grains for 5 rounds and test, but in my online reading, some report TAC likes/needs to be at max for accuracy, which is 24.8 grains per VV data. So, maybe it’s futile to reduce the load?

i can’t imagine 0.3 grain would affect brass obturation & case dirtiness, but i’ve encountered claims that both accuracy & “case cleanliness” are obtained at max TAC charges. My 5.56 reloading experience is limited. I used to use WC846 surplus for plinking ammo—TAC is new to me for 5.56.

can anyone more experienced offer advice?

I suspect trial & error is the answer, which is fine—but if i could save some time & powder, that would be appreciated.

nn8734 · Aug 1, 2021

one of My mk262 mod 1 clone loads is 77smk, 24.5G of TAC, 1x Lake city and Remington 7-1/2 primer. Cases get a little dirty but I put them in Thumbler’s Tumbler and they come out looking brand new.

The other uses AA2520 at 25.0g, same components as above.

What do you mean by “accuracy was mediocre”? Are you saying it doesn’t group well? If so, that’s precision potential (or lack thereof).

Try tweaking seating depth first. If that doesn’t work, Try switching primers, that may help. Or if it’s more feasible, switch to the 77smk.

ETA: Answeing one of your questions, TAC does like to be near its max safe charge in my experience with it - all my loads using it had their best precision, SD/ES right at pressure. Also .3g is material with the 5.56, esp with TAC.

Xcount · Aug 1, 2021

I've known guys that ran 24.0gr. I would never recommend using a crimp die for accuracy rounds but that is what they said they needed to make it work. They said the Lee FCD is all they used and it made a huge difference.

Zatoichi66 · Aug 1, 2021

nn8734 said:
one of My mk262 mod 1 clone loads is 77smk, 24.5G of TAC, 1x Lake city and Remington 7-1/2 primer. Cases get a little dirty but I put them in Thumbler’s Tumbler and they come out looking brand new.

The other uses AA2520 at 25.0g, same components as above.

What do you mean by “accuracy was mediocre”? Are you saying it doesn’t group well? If so, that’s precision potential (or lack thereof).

Try tweaking seating depth first. If that doesn’t work, Try switching primers, that may help. Or if it’s more feasible, switch to the 77smk.

ETA: Answeing one of your questions, TAC does like to be near its max safe charge in my experience with it - all my loads using it had their best precision, SD/ES right at pressure. Also .3g is material with the 5.56, esp with TAC.

“Accuracy was mediocre” means the groups were around 2” at 1 hundred yards and i didn’t bring any Black Hills for comparison. i have grouped MOA with this rifle & Black Hills Mk262. And I forgot the chronograph….and different POA/POI vs last session i confirmed zero with Black Hills Mk262.

I do clean brass, actually dry walnut tumbled first, then wet pins/tumbler after resizing, tomremove Hornady One Shot lube, so my obtuse question about cleaning & accuracy aren’t meant to be confuing. Just looking for experienced directions given conflicting info online about TAC.

Zatoichi66 · Aug 1, 2021

Xcount said:
I've known guys that ran 24.0gr. I would never recommend using a crimp die for accuracy rounds but that is what they said they needed to make it work. They said the Lee FCD is all they used and it made a huge difference.

I have a Lee crimp die i use on my 5.56 reloads (55 gr FMJ) and can crimp, but my understanding is when accuracy is desired, crimps can hurt.

maybe my crimp info is wrong?

sounds like i need to:

1) Bring Black Hills factory Mk262 for direct comparison
2) Try lower & higher loads
3) remember the chronograph….

nn8734 · Aug 1, 2021

Zatoichi66 said:
“Accuracy was mediocre” means the groups were around 2” at 1 hundred yards and i didn’t bring any Black Hills for comparison. i have grouped MOA with this rifle & Black Hills Mk262. And I forgot the chronograph….and different POA/POI vs last session i confirmed zero with Black Hills Mk262.

I do clean brass, actually dry walnut tumbled first, then wet pins/tumbler after resizing, tomremove Hornady One Shot lube, so my obtuse question about cleaning & accuracy aren’t meant to be confuing. Just looking for experienced directions given conflicting info online about TAC.

How did you arrive at 24.5 initially? Did you do an OCW or Ladder? Or did you just pick that charge weight and go with it?

Zatoichi66 · Aug 1, 2021

To be blunt: I shoot my Tikkas way better than this AR build. I was struggling to bounce between easy to shoot accurately bolt guns & the AR. It has a Geissele SSA trigger, but the whole semiauto cycling was distracting compared to the Tikkas. In a prior thread, i showed my best group with a Tikka that was sub-0.75” but i’ve never done that with this CLE build. I’m new to precision rifles.

i’m getting old & less flexible between rifles/platforms.

nn8734 · Aug 1, 2021

Zatoichi66 said:
To be blunt: I shoot my Tikkas way better than this AR build. I was struggling to bounce between easy to shoot accurately bolt guns & the AR. It has a Geissele SSA trigger, but the whole semiauto cycling was distracting compared to the Tikkas. In a prior thread, i showed my best group with a Tikka that was sub-0.75” but i’ve never done that with this CLE build. I’m new to precision rifles.

i’m getting old & less flexible between rifles/platforms.

The tikka, like most bolt guns, masks flaws in your fundamentals. They get exposed when shooting semis. That said, if shooting Mk262 at 1 MOA and your load at 2 MOA then fundamentals are only part of the story.

Zatoichi66 · Aug 1, 2021

nn8734 said:
How did you arrive at 24.5 initially? Did you do an OCW or Ladder? Or did you just pick that charge weight and go with it?

Picked based on reading & no, i haven’t tried to tailor a load to this barrel. I figured backwards, if Mk262 shoots well, replicating Mk262 would be key….it seems working up reloads with this barrel may yield better results.

whatsupdoc · Aug 1, 2021

CLE chamber will show pressure on some standard loads, so take it slow.
Do not crimp.
Did you crono the Black Hills ammo?
As far as accuracy a Krieger barrel with a CLE chamber normally shoots very well so it could be the bullets the
load or the shooter.

nn8734 · Aug 1, 2021

Zatoichi66 said:
Picked based on reading & no, i haven’t tried to tailor a load to this barrel. I figured backwards, if Mk262 shoots well, replicating Mk262 would be key….it seems working up reloads with this barrel may yield better results.

Yep, found the problem. Work up a load and then post the initial results if you want help interpreting what you see on paper / MV data. I prefer OCWs but others have had success with other methods

Zatoichi66 · Aug 1, 2021

No to chrono BH.
yes to shooter. I’m “minute of steel plate” trying to transition to smallest paper groups.
yes, as the shooter, i’m probably the weakest link.

Zatoichi66 · Aug 1, 2021

whatsupdoc said:
CLE chamber will show pressure on some standard loads, so take it slow.
Do not crimp.
Did you crono the Black Hills ammo?
As far as accuracy a Krieger barrel with a CLE chamber normally shoots very well so it could be the bullets the
load or the shooter.

The cases from my loads looked like typical 5.56 loads—some swipes & minimal primer cratering, similar to Black Hills i’ve shot through the rifle. I’ve read BH uses TAC for this load, but I realize that is probably internet lore….yes, i realize the CLE chamber is tighter than a Wylde or 5.56 chamber, but this SAM-R build was supposedly designed for use with Mk262.

as noted, i’ve realized i’m going about this the wrong way in trying to replicate Mk262 rather than tailor the load to the barrel; I’m glad i learned this before i did something more stupid.

thanks all.

nn8734 · Aug 1, 2021

Zatoichi66 said:
The cases from my loads looked like typical 5.56 loads—some swipes & minimal primer cratering, similar to Black Hills i’ve shot through the rifle. I’ve read BH uses TAC for this load, but I realize that is probably internet lore….yes, i realize the CLE chamber is tighter than a Wylde or 5.56 chamber, but this SAM-R build was supposedly designed for use with Mk262.

as noted, i’ve realized i’m going about this the wrong way in trying to replicate Mk262 rather than tailor the load to the barrel; I’m glad i learned this before i did something more stupid.

thanks all.

BH uses non-canister grade powder with additives not available to us mere mortals. According to Jeff Hoffman, when Mk262 was in development BH included an additive in the powder recipe that resulted in a gain of over 100 fps with no pressure consequences. Think Chris Bartucci talks about it in one of his videos on the Mk12 family.

Cascade Hemi · Aug 1, 2021

24.5gr of TAC is around 61kPSI. I'm not sure what your goals are but I assume they aren't the same the army's. I'd work up from 23gr knowing that you aren't achieving anything by going with the highest possible pressure.

Xcount · Aug 1, 2021

MK262 is crimped.

just saying...

blackblue · Aug 1, 2021

If it matters western shows TAC at 24.8 in 5.56 loads at 61.5k with a 77gr sierra.

Rhed · Aug 2, 2021

The whole concern is a dirty case?

TxWelder35 · Aug 2, 2021

I’ve tried 3 powders for a mk262 clone

out of my 18” proof barrel with Wylde chamber and a rem 7.5 primer and LC brass

24.8gn of 2520 will get me 2750fps in the 100 degree summer heat and 1/2-3/4” groups. in the winter there a pretty noticeable loss of velocity and the groups open up, will need to redevelop this load in the winter.

23.6gn of 8208xbr will get me 2750fps and it’s temp stable same 1/2-3/4” groups

iirc both are like 20SD and 50 ES with a powder thrower, I’m

both loads are at the top end.

tried cfe223 with a 75gn hornady bthp the other day.

25.6gn got me to 2900 fps with a 9.4 sd and 41 es.

25.3gn was 2850 fps a sd of 17 and es of 77

I was told that cfe likes to be at the very top to keep the sd/es down

all my sd/es data is over like 50 rounds with a Labradar. I could cherry pick 10 in a row in single digits sd/es on any of those loads.

edited to add, I shoot 100% suppresses and my brass is pretty much completely completely covered in carbon no matter what I shoot

Zatoichi66 · Aug 2, 2021

Rhed said:
The whole concern is a dirty case?

No, unless the dirty case is an indication of more powder being required for accuracy. Again, several other reloading forums recommend max TAC for accuracy, and note that “dirty cases” are the norm with too low powder charges. The majority of folks say TAC is clean—a handful say it’s dirty, especially at lower charges where poor accuracy is demonstrated. Internet lore?

BH Mk262 shoots well in this rifle, so my plan was to duplicate Mk262 which would allow me to develop loads based on the barrel. It seemed to make sense at the time—no need to change zero, etc.

i was wrong & will load up a ladder loads, the standard way.

whatsupdoc · Aug 2, 2021

Forget cloning MK262 bullshit, find a load that your rifle likes and learn to shoot.
The thing is if you are not capable of shooting small groups with an AR how are you going to
test ammo for accuracy.

Pay close attention to your trigger pull and after the rifle fires and cycles make sure you consciously feel
the trigger reset.

Zatoichi66 · Aug 2, 2021

whatsupdoc said:
Forget cloning MK262 bullshit, find a load that your rifle likes and learn to shoot.
The thing is if you are not capable of shooting small groups with an AR how are you going to
test ammo for accuracy.

Pay close attention to your trigger pull and after the rifle fires and cycles make sure you consciously feel
the trigger reset.

You are correct—at least I didn’t get hurt by bassackward thinking!

308pirate · Aug 2, 2021

Zatoichi66 said:
I’m using 1X LC brass, Nosler 77gr OTM and 24.5 grains of TAC with CCI 41 caps. The upper is a Compass Lake Engineering 20” Krieger 1/8 build (their SAM-R) with CLE chamber. I’m trying to replicate Black Hills Mk262 so i can save the few factory rounds i have, but still practice. After researching recipes, i settled on the above load & was astonished on how dirty the spent cases were. Accuracy was mediocre. My goal is accuracy & replicating Mk262 loads. At this time, my plan is to drop to 24.0 grains and increase by 0.2 grains for 5 rounds and test, but in my online reading, some report TAC likes/needs to be at max for accuracy, which is 24.8 grains per VV data. So, maybe it’s futile to reduce the load?

i can’t imagine 0.3 grain would affect brass obturation & case dirtiness, but i’ve encountered claims that both accuracy & “case cleanliness” are obtained at max TAC charges. My 5.56 reloading experience is limited. I used to use WC846 surplus for plinking ammo—TAC is new to me for 5.56.

can anyone more experienced offer advice?

I suspect trial & error is the answer, which is fine—but if i could save some time & powder, that would be appreciated.

I can tell you that going from 42.5 to 43.3 grains of TAC in my 308 load (178 gr ELD-M, Lapua brass) completely eliminated the sooting I was seeing. That's not the reason why I went up in charge, but the effect was there nevertheless.

I concur with the observations that TAC likes to be run hard.

smoothy8500 · Aug 2, 2021

Zatoichi66 said:
....yes, i realize the CLE chamber is tighter....but this SAM-R build was supposedly designed for use with Mk262.

The CLE chamber was designed for National Match AR's which typically aren't run at 5.56 NATO pressures. Secondary to that is your choice of Nosler Custom Competition 77's. My experience with them in my NM AR15 is that they don't show best accuracy loaded at NATO pressures either. They are a solid performer at 600 yards loaded at 223 velocity and will be an adequate training round, but not at the same POI of the MK 262.

Zatoichi66 · Aug 2, 2021

smoothy8500 said:
The CLE chamber was designed for National Match AR's which typically aren't run at 5.56 NATO pressures. Secondary to that is your choice of Nosler Custom Competition 77's. My experience with them in my NM AR15 is that they don't show best accuracy loaded at NATO pressures either. They are a solid performer at 600 yards loaded at 223 velocity and will be an adequate training round, but not at the same POI of the MK 262.

I guess I’m confused at how/why Mk262 & SAM-R was chosen. Regardless, for my needs—I need to forget this idea & just develop a load while working on my semiauto skills.

308pirate · Aug 2, 2021

whatsupdoc said:
Forget cloning MK262 bullshit, find a load that your rifle likes and learn to shoot.

I agree. /thread

I wish I had seen this first, I wouldn't have added fuel to this dumpster fire of a thread.

@Zatoichi66 please forget everything in this thread (including what I said earlier) except the post I quoted.

Zatoichi66 · Aug 2, 2021

308pirate said:
I agree. /thread

I wish I had seen this first, I wouldn't have added fuel to this dumpster fire of a thread.

@Zatoichi66 please forget everything in this thread (including what I said earlier) except the post I quoted.

You didn’t add anything other than experience. I appreciate your help.

Reader’s Digest version: I tried to clone Mk262 with different components hoping it would work accurately as a short-cut rather than typical, proper recommended load work up. I failed, just like everyone who asks for someone else load data for a different rifle.

just like with many “short cuts,” time lost is it’s own experience & expense. I’m a little embarrassed but still have all my fingers—that’s a good day!

Rhed · Aug 2, 2021

308pirate said:
I can tell you that going from 42.5 to 43.3 grains of TAC in my 308 load (178 gr ELD-M, Lapua brass) completely eliminated the sooting I was seeing. That's not the reason why I went up in charge, but the effect was there nevertheless.

I concur with the observations that TAC likes to be run hard.

42.2 of TAC for my .308 175 smk. For my .223 rifle with 77 gn tmk, I get good results with RL15. Never tried TAC for .223. Though, I do .002 neck with a light taper crimp on my semi.

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Ramshot TAC 5.56 77gr OTM dirty case/accuracy question

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