TMKs - Seating distance off the lands

[VarmLR]

Anyone else had issues with Sierra TMKs seated close to the lands (say up to 10 thou?). I can't seem to find a node for 69gr 224 bullets...most groups are similar (all around 1 moa or slightly more) i.e. poor. I seated 10 thou off lands and am beginning to think that the TMK might be sensitive to jump. Anyone tried them with much larger jump? At the same time, I tried some 60gr Vmax, again, 10 thou off lands and was looking at a group less than half the size. Barrel is 1/8 twist 223 so should favour the heavier bullet. I normally start load dev with 10 thou jump and vary powder charge but am now thinking that I should start at book seating length, get the tightest group and then try altering leade. Any advice welcome.

[MrCetrizine]

My 1:8 .223 T3 likes them 5 thou off the lands, the same as the SMK. I only use 77gn though, I could never get the 69s to group well.

[Akeld]

Just off the lands for mine

[VarmLR]

My 1:8 .223 T3 likes them 5 thou off the lands, the same as the SMK. I only use 77gn though, I could never get the 69s to group well.

 

Interesting. You're not the first person to say the same. I tried various distances to check whether it was just they needed more time to stabilise but with similar results. I may try some more seated to book length (ie reloading manual) and see what they do and if no change, just accept that they don't shot well from the rifle.

[Big Al]

Myself and a couple of friends who all have 9 twist barrels have had excellent results with 69 TMK's in 22BR and 22/250 and have found them to be relatively unfussy when it comes to seating depth. Ive had good results touching and at 10 and 20 thou off, I think my friends are around 10 to 30 thou away with one of them saying his groups were getting better the further away he went. Ive had other types of bullets jumping as much as 160 thou with tremendous accuracy, dont be afraid to push them into the case a bit and get them jumping but factor in the potential rise in pressure if your near max load.

 

Have you done an OCW test?

[VarmLR]

Myself and a couple of friends who all have 9 twist barrels have had excellent results with 69 TMK's in 22BR and 22/250 and have found them to be relatively unfussy when it comes to seating depth. Ive had good results touching and at 10 and 20 thou off, I think my friends are around 10 to 300 thou away with one of them saying his groups were getting better the further away he went. Ive had other types of bullets jumping as much as 160 thou with tremendous accuracy, dont be afraid to push them into the case a bit and get them jumping but factor in the potential rise in pressure if your near max load.

 

Have you done an OCW test?

 

Hi, yes, I have. I Looked to the maximum recommended loads from load data tables (Lee, Sierra, Viht) and took the lowest of the max recommended loads. I looked to the min recommended loads and took the highest of these. I then worked up loads starting low to high in 0.2 grain intervals. Starting with a clean bore, and allowing two fouling shots, I then shot groups of 5 shots, with a minute or two between shots to allow the barrel to cool. At 25 shots, I cleaned the barrel, fired two more fouling shots, and resumed in the same manner. I then looked to the groups to see if I could identify nodes where bullet groups fell to the same place. Most did but a few were off considerably from the others.

 

From the groups that landed to the same place, I looked first for the most consistent grouping patterns, then selected a few of the tighter groups. Three loads stood out. 24.6g N140, 24.8 and 25.4 (but 23.6 was also not too bad). They all gave the tightest and most consistent groups landing in the same spot. Those groups were 0.86, 0.9 and 1.04 inches respectively, so not something any of us would want to broadcast! Doing the same thing for my 308 and 155MKs, I was getting nodes at 42.6 and 44g N140 and groups of 0.35 and 0.4 inches, so respectable. The 223 are anything but.

 

I will revisit action screw torque settings and eliminate any issues there, but the stock is lnlet and bedded, and other loads like 60 Vmax group well, hence I'm a little baffled by why the 69s don't work well.

 

I hope that the method I've used approximates to an Optimal Charge Weight test.

[Big Al]

Is it a new rifle with new brass?

 

Ive heard a few people say that they found both the 69 and 77TMK's very easy to get to shoot well and that has been the findings of myself and two friends. I accept that doesn't mean everyone will be successful all of the time but all three of us worked up very accurate loads quickly and easily and with less attention to detail on the OCW test than you showed. I usually go in 0.3gr increments or sometimes even 0.5gr ones as I feel it shows up the nodes easier, you can then work either side of these weights to fine tune. Personally I think sometimes people make changes that are too small during the early stages of load development and its harder to sort the wheat from the chaff.

 

I think I would take your most accurate powder charge and then load up your rounds in 5's starting with touching and then moving 10 thou away from the lands until 40 thou. If you can't find the accuracy you want then maybe the barrel doesn't like the bullets - what make of barrel is it?

 

If the rifle groups well with other loads at the same stock bolt torque and with the same scope then you can rule them out.

[VarmLR]

The action 15 years old at least. The barrel is a new L-W Match, 26 inch 6 groove button rifled in LW50. It has had around 300 rounds through it since it was fitted a few months ago. The stock is new, and has been bedded. I think I'll start again in larger intervals, well off the lands to begin with just to see if there is any significant difference and adjust loads to account for pressure rise with bullets seated deeper. I'll do two lots, one seated about 100 thou off and one at about 30 thou off. That ought to show any sensitivity to jump. I'll just shoot 3 shot groups to start with and work up more statistically relevant groups once I've established the best loads/jump for these "wheat from chaff" tests.

[onehole]

I am using the 69 TMK in my 1 in 8 22PPC and also in a 1 in 9 Howa Mini in 223...I load developed both rifles with a 5 thou jump ,,,,,,blown away with 22PPC performance and also that of the little Howa. Firmly believe you can choose a jump within reason and load to suit in most cases,,,,,if not then would suspect something else and even think the bullet is not quite suiting that barrel?,,,only a thought,,,,,O

[Big Al]

The action 15 years old at least. The barrel is a new L-W Match, 26 inch 6 groove button rifled in LW50. It has had around 300 rounds through it since it was fitted a few months ago. The stock is new, and has been bedded. I think I'll start again in larger intervals, well off the lands to begin with just to see if there is any significant difference and adjust loads to account for pressure rise with bullets seated deeper. I'll do two lots, one seated about 100 thou off and one at about 30 thou off. That ought to show any sensitivity to jump. I'll just shoot 3 shot groups to start with and work up more statistically relevant groups once I've established the best loads/jump for these "wheat from chaff" tests.

 

 

I dont see any logic in such a big and random difference in seating depths. Although I said earlier that I feel jumps need to be big enough to see I can't get my head around a 30 thou and then straight to 100 thou jumps.

 

I had a 20BR which I was using 55gr Bergers, on the advice of Berger I went touching, then -40 thou, -80thou and -120 thou. Each group got better and so I tried -160 thou and the rifle shout 1/2"@300yds more than once, I never changed anything after that. All of these were tested using the same powder charge.

[VarmLR]

 

 

I dont see any logic in such a big and random difference in seating depths. Although I said earlier that I feel jumps need to be big enough to see I can't get my head around a 30 thou and then straight to 100 thou jumps.

 

I had a 20BR which I was using 55gr Bergers, on the advice of Berger I went touching, then -40 thou, -80thou and -120 thou. Each group got better and so I tried -160 thou and the rifle shout 1/2"@300yds more than once, I never changed anything after that. All of these were tested using the same powder charge.

 

The only reason for the big jump was that it was recommended to see if the rifle shot any better or worse with the best of the (poor) groups. What you say makes sense though so I may just start at 20 thou off and work back in 20 or 30 thou jumps. I know that 10 though doesn't work for me.

 

However (he said with red face )....I found what I think might be the REAL culprit whilst stripping the Rifle this afternoon just to start from scratch and check everything was tickety-boo. There was a small piece of card lodged under the barrel about half way down. Scratching my head I wondered how it got there and why it got there! Then I noticed it was a small covering originally used over the proof stamp which must have come off and somehow lodged itself just under the barrel! Offending item now removed and I've had a little more taken from the stock all round just to be on the safe side so I am 100% happy it's free floating without compromise forward of the bedding lug.

[Big Al]

Let us know how it goes?

[Charlts]

I'm 10 thou off with my pet 69gr TMK loads, I know of a few guys jumping 20 thou with the 77gr TMK's.

[VarmLR]

Thinking about it they are quite an aggressive Ovige profile, looking like a secant profile rather than a shorter tangent Ogive like the SMKs. Originally I had thought that they were a tipped SMK but this appears not to be the case. Their tip is broader and the Ogive much longer. I've found the SMKs to be very jump tolerant and shoot the .308 SMK at 50 thou jump (so that I can magazine feed it) with excellent results. The TMK may well respond at just one or two seating depths, so now the issue with the rifle was found and sorted, starting at 10 thou and moving back in 20 to 30 thou intervals to between 100 and 130 thou should show up the best seating depth for my rifle. It would seem that patience is needed (and deeper pockets) when developing loads for the TMK!

[Big Al]

Thinking about it they are quite an aggressive Ovige profile, looking like a secant profile rather than a shorter tangent Ogive like the SMKs. Originally I had thought that they were a tipped SMK but this appears not to be the case. Their tip is broader and the Ogive much longer. I've found the SMKs to be very jump tolerant and shoot the .308 SMK at 50 thou jump (so that I can magazine feed it) with excellent results. The TMK may well respond at just one or two seating depths, so now the issue with the rifle was found and sorted, starting at 10 thou and moving back in 20 to 30 thou intervals to between 100 and 130 thou should show up the best seating depth for my rifle. It would seem that patience is needed (and deeper pockets) when developing loads for the TMK!

 

 

The certainly hasn't been mine or my friends experiences. I will be amazed if you can't get sensible groups around 1/2" with them 10 or 20 thou off. If your rifle shoots other bullets well then I dont think TMK's are a marmite type of bullet - good luck though

[VarmLR]

I'll update the thread once I have a chance to load and test some more. Probably a week or so.

[gbal]

Varm, you are in the ball park. Here is what Sierra said about the then new (2014) green tipped MKs:

 

"The meplet point on the tip is smaller than the meplet on the SMK,and most of the ogives changed too from the legacy SMK product."

 

ie the TMKs are mostly not plastic tipped legacy Match King Hollow points ...does that include the 69 and 77 g 224s...well, the 77 seems a new shape,because:

 

"the BC gains are mostly from the reshaped ogives" and the new green tip TMK 77 now has the same BC(.420) as the old,legacy 80g HPBTMK.

 

gbal

[VarmLR]

Thanks gbal...that seems to tie up...makes sense. Just took a look on the Sierra website. Looking at the ogives side by side, they're very different. Also interesting to note some of the issues when deeper seating the TMKs as some bullet seaters may damage the tip or leave marks on the ogive due to the large radius. I didn't notice any when seating mine but they were only at 10 thou but forewarned is forearmed!

[gun nut]

Varmler, get yourself a lee hand press, load 20 rnds of your best lower powder load, and seat them all 10 thou off. When you start shooting keep screwing your seater die in 1 turn between groups, this will be approx 36thou each time. Within 4 groups you will find a node.

 

Mike

[VarmLR]

Thanks Mike, noted. I have a Breech-lock press and can do the same with that. Best load with N140 seems to be around 24.5g but I need to re-try a few loads with the (now fully) floated barrel. Haven't found a lower load that seems to work with these that well.

[VarmLR]

Took the rifle out today and tested a couple of loads and seating distances for comparison. Weather wasn't great, winds gusting between 8 and 15mph and blustery rain showers. Target was moving a little in that wind as board was acting like a sail so I had to try and shoot in between gusts. Not ideal!

 

Sunday saw some group testing of loads. I picked the two best loads (both at 10 thou off lands) which were 23.6g N140 and 24.6g N140. Groups in between opened up a bit from this, so there are two definite nodes for load.

 

Starting with the 23.6g loads, I shot these at 10, 40, 70 and 100 thou off lands. Best group in the squally conditions was not great but was 0.6 inches at 70 thou off.

 

Results: 23.6g N140

 

Thousandths: Group (inches):

 

10 1.28

40 0.79

70 0.60

100 0.90

 

Next, I tried the 24.7g loads. These were not seated any deeper than 40 thou as it was starting to be a compressed load by 20 thou off lands, so although I loaded to 70 thou, I could feel the propellant crunching in the seating die as it was being compressed and prudence and safety meant that I didn't venture to shoot those loads! Therefore I tried 10, 15, 20 and 40 with no pressure signs by 40:

 

Thousandths: Group (inches):

 

10 1.09

15 0.82

20 0.82

40 0.78

 

These aren't great groupings, but I reckon with the target rocking back and forth it wasn't helping matters and the group sizes were opening vertically on the tighter groups so that might indicate that in still conditions I may have perhaps halved the group sizes (probably about right). The tightest groups had most holes touching with one flyer north of the group but I included all fliers on the groups.

 

I don't know how representative this is of a typical tolerance to jump with the TMKs as some report no change with their rifles, but from the above, I'm minded to think that the accuracy node might lay somewhere between 50 and 60 thou off? Tightest group was at 70 thou off but there was a greater expansion back to 40 then there was back out to 100 thou so the group may be opening up by 70 thou assuming there's a node between these seating depths (as the lower charge was a tighter group further seated in than the heavier load, and the group seemed to be closing with seating depth getting more on the heavier load, this might be a fair assumption).

 

I'll try several more with both loads seated at 55 thou off and pick the tightest one as the accuracy load/seating depth for the TMK in my rifle. It's not great though. I was shooting 0.3 with the 308 and SMK 155s (40 thou off) by comparison.

 

Does the above seem a logical end point for the TMKs in this rifle or are there any other tricks that I can play?

[onehole]

Varm I really wouldn,t be load testing and evaluating in those conditions but if I had a rifle that would pretty much hold .5 on a good day then your groups aint so bad for a bad day which is clearly the conditions you shot in.Think the trick that's left just maybe being patient and waiting for a better day.Your 308 had a little more wind bucking on board with the 155,s ,bc and may have had something to do with turning in a better performance.,,,,,,,,O.

[VarmLR]

That's very fair comment. It started off a good day, light breeze but by the time I'd driven to my shooting land, it had picked up big time and rather than pack up and go home I decided to stick it out and shoot between the worst of the wind. Don't know if I'm expecting too much, but on a still day I'd want to see them clover-leafing so quarter of an inch to perhaps .3 at 100 yds from this rifle should be a reasonable expectation all else being equal, and me doing my part. There's not much point in building a long range vermin control outfit if I can't shoot into 2 inches at 400 yds all day long, so .5 moa is my goal (obviously with different bullets. The rifle likes 60gr Vmax).

 

In spite of the conditions, there was a correlation between group size and seating depth for each load.

[gun nut]

VarmLR

 

what you are actually doing when you change seating depth/ powder load is altering the point in the oscillation of the muzzle at which the bullet leaves the crown, so there are multiple combinations of the 2 variables that will work, just as there are multiple velocities/loads that mean the bullet exits at a minimum oscillation node( in a 22" barrel these seem to equate to 2650fps ish and 3000ish from my experience, although there may be ones in between). What the OCW method seeks to do is give you a guide as to when the muzzle is at it's least amplitude of movement. That's why small changes in temp/load etc around that node still shoot to essentially to the same poi.

Forgive me if I'm teaching my granny to suck eggs, but so many people bang on about "these bullets like to jump this and those ones that etc etc " when all they are actually doing is tuning the exit point of the bullet from the barrel to a zero amplitude node. Once you get your head round this doing load development becomes more of science and less of a black art!

 

Hope that helps

 

Mike

 

PS In those weather conditions it would be risky to draw any firm conclusions, but sounds like you're heading the right way

[sean223]

Why not try and jam them in the lands. Am shooting 77gr TMKs in a 1:8 twist 24" barrel at 5tho jam. It may work for you!