Loads for 77gr TMK

[markymark]

Hello,

 

Does anyone use the .223 77gr TMK on here? I can't find any load data on it.

 

You can find data for the SMK but not the TMK. The TMK is significantly longer bullet but will be loaded at spec of 2.26" as I want them magazine fed. This will be a significantly compressed load if using the normal SMK data.

 

Does anyone sharing their load data with TMK and what velocities they are getting? (Hopefully with N140 or H4895)

 

Thanks in advance,

 

Mark

[John MH]

Use the same loads as the SMK, compressed charges are quite normal with both bullets.

[MrCetrizine]

24.3gn of N140 gives me 2780 ft/s from a 20" 1:8 twist barrel.

[markymark]

24.3gn of N140 gives me 2780 ft/s from a 20" 1:8 twist barrel.

You can fit all that in a case and still make up to standard COAL?

 

I've also got a 20" 1:8 and I would be very happy with those results!

 

Out of interest you using normal small rifle or magnum primers to achieve that velocity?

 

Thanks for your help guys

[gun nut]

Try CFE223 its a very dense powder. 24.3gr behind a 77smk shoots bug holes in my .223 wylde. Use br4 primers if you have them.

 

Mike

[MrCetrizine]

You can fit all that in a case and still make up to standard COAL?

I've also got a 20" 1:8 and I would be very happy with those results!

Out of interest you using normal small rifle or magnum primers to achieve that velocity?

Thanks for your help guys

Yes, it's a bit crunchy when seating the bullet but not what I'd call compressed. I went as high as 24.7 while load developing without pressure signs. I'm using an extended drop funnel to ensure a tight case fill.

 

I was using CCI BR4 primers but switched to standard CCI 400 with no noticeable difference.

[bradders]

It was designed as a mag length (2.250") bullet for 300yd rapid fire

[markymark]

I finally got around to finding my lands. Any previous ammo I have made just replicated factory ammo using standard specs.

 

Results:

 

My COL on the .223 is 2.457" or

62.42mm. My magazine can actually accept more so this is not the limiting factor. (Please bare in mind this was done using the 77gr TMK which is a very pointy bullet. Some of the bullet tip is perhaps into the rifling at that stage but is not actually in contact with the lands.)

 

Now back to the TMK, it is suggested just making them to standard length. However if I have the space in the magazine and the space in the rifle, would I not make longer to start with? Is jump always bad or do some rifles like it?

 

Obviously if I lengthen to bullet by changing the seating depth I will allow a higher case capacity and won't run into any powder compression issues I was previously worried about.

 

Now this will be the first time doing some serious load development. Do I keep to standard case spec, work the powder charge then later fine tune on seating depth & jump. Or given that I have the space in the mag and COAL in the rifle start with a longer bullet to allow more potential powder and reduced jump?

 

I know every rifle is different with different ammo but is there a good starting point in regards seating depth off the lands?

[Laurie]

I know every rifle is different with different ammo but is there a good starting point in regards seating depth off the lands?

 

It is determined more by bullet type / shape than anything else. Secant ogive designs (many Hornady models, but even more so those described as 'VLD' types) are much less jump tolerant than those with tangent or 'Hybrid' forms. Often they either have to be seated into the lands or well off.

 

Those 77s designed for loading to 2.25" AR mag length by definition have to be able to accept a lot of jump as most .223 chambers developed for the US XTC discipline have freebores determined by the use of 80gn bullets loaded to 2.445" COAL or longer and single-loaded in the prone 600 yard stage. Magazine length rounds loaded with 69s and 77s therefore produce a lot of jump, but the tangent ogive bullets used will normally accept it.

 

Playing around with Sierra, Lapua and Berger 77s some years back in a Wylde chamber 223, I loaded them to 2.25 and also to have the 'usual' optimum tangent ogive bullet amount of jump (10 to 15 thou'). To my surprise, the deep seated bullets performed just as well, maybe even a little better, than those seated 'optimally' - and in both cases groups were good, well under the half-inch 100 yard mark for five shots.

 

Going further, when trying Reload Swiss RS52 with 90s in a 223 FTR rifle chambered with the PT&G '223 ISSF' chamber with its 0.169" freebore last year, I loaded up some Sierra 77s to put the bottom of the shank just above the base of the case-neck above RS52 - no idea of the jump in this super long FB chamber, but likely in excess of 100 thou'. To my surprise, once loads / MVs became high enough (3,000 fps plus from a 28-inch barrel) they shot tiny groups!

 

I've not yet tried the 77gn TMK - will do soon - but as JohnMH and Bradders point out, this bullet is designed as per the MK version to be seated deeply and make a large jump, so it should perform pretty well as per the older model when so treated. If your magazine allows you to use longer COALs, then you can load them to have a shorter jump - 15 thou' is always a good starting point - and see if they shoot any better for you. If nothing else, it'll stop you cringing as you hear / feel those powder kernels crunching as you seat bullets.

[gbal]

marky,you know that bullet shape (ogive eg) is an important determiner of the COAL of a loaded round. Commercial ammo keeps the COAL just under magazine length.As you note,it's irrelevant if some of the bullet tip is into the barrel,before the bearing surface contacts the lands. That is why length to ogive is critical-exceed that and the bullet is progressively pushed into the lands-a few bullets are OK just touching,but more increases pressure.

Here is what Sinclair's Precision Reloading & Shooting Handbook advises:

 

"Most .22 caliber center fire rifles perform best with the bullets .010 to .020 off the rifling'.....a guide,each rifle/bullet option can be individual.But that amount of "jump' is a good starting point.(note seating depth is a fine tune,to be done after basic best powder charge is determined.In larger calibres,especially,modern bullet designs_the hybrids-have much increases the tolerance for seating depth,so that it can be considerably less fussy. Stat around .010 to .015 as measured with a comparator. Odds are veery much that you will be close to optimum at that (increase 'jump' if needed).Cartridge Length To Ogive is the way better measure,because chambers-or rather where the rifling starts just varies in different makes/models(sometimes by design-eg to allow longer bullets).

Ideally,you do not want to be scrunching powder in the case,and you may end up -as throat erodes ,"chasing" the rifling down the barrel (we're talking small amounts) to maintain jump-don't worry about that in a 22 cf,unless it's seriously hot-nothing much you can do about erosion anyhow.

 

Seat now about ,010 to .015 off touching.

 

gbal

 

gbal

[Andrew]

I contacted Nosler about their new RDF bullets. The 70 grain RDF is .965" long compared to the .900 inch, 69 grain Custom Competition I have been shooting. All of these bullets were tested to magazine length. Use standard data. (with the usual caveat about reducing loads when you change components) This correlates with reports I get from PRS guys shooting them in warmer climes. I loaded these over my standard Varget load to magazine length: definitely a compressed load. Despite sub zero Fahrenheit weather I'm tempted to try to get them out to the range for a brief test. ~Andrew

[markymark]

First and foremost thank you (particularly Laurie & gbal). I love this forum that people take the time to write lengthy well considered replies. It's very much appreciated! A wealth of knowledge.

 

From what I have read, I am getting the take home message: (and correct me if I am wrong)

 

That the sierra 77SMK much like many of the sierra designs are very jump tolerant. I should achieve good or great accuracy with conventional COAL but there maybe some gains to be had playing with seating depth. However it's a fine tune, and should be considered after achieving a safe powder load at a desired velocity.

 

I thought I would perhaps start my testing based at or around 2.330"

 

Bullet length for 77gr SMK .997"

Bullet length for 77gr TMK 1.066"

0.069" difference or 1.75mm

 

Standard COAl of 2.260" + TMK difference = 2.329" (59.16mm)

 

So that was born from adding the difference in bullet length between the SMK and TMK and should benefit from being slightly closer to the lands whilst providing the same case volume as it's SMK sibling. All in aid to avoid any powder crunch.

 

Hopefully work up to a safe load using my N140 and try altering seating depths later on down the road......

[markymark]

Definitely feeling more educated now. Thank you all.

 

http://www.bergerbullets.com/effects-of-cartridge-over-all-length-coal-and-cartridge-base-to-ogive-cbto-part-2/

 

Found that an interesting read for anyone else's benefit

 

Cheers

[gbal]

Definitely feeling more educated now. Thank you all.

http://www.bergerbullets.com/effects-of-cartridge-over-all-length-coal-and-cartridge-base-to-ogive-cbto-part-2/

Found that an interesting read for anyone else's benefit

Cheers

Well found,Marky-I should have referenced that article - CBTO (Cartridge Base To Ogive) is way more informative than COAL (magazine fit apart).

Bryan Litz -head ballistician now at Berger Bullets-on any ballistic topic (including rocket science) is informative and data driven.

A guru -and exceptionally fine target shooter too.

 

gbal

[VarmLR]

First and foremost thank you (particularly Laurie & gbal). I love this forum that people take the time to write lengthy well considered replies. It's very much appreciated! A wealth of knowledge.

 

From what I have read, I am getting the take home message: (and correct me if I am wrong)

 

That the sierra 77SMK much like many of the sierra designs are very jump tolerant. I should achieve good or great accuracy with conventional COAL but there maybe some gains to be had playing with seating depth. However it's a fine tune, and should be considered after achieving a safe powder load at a desired velocity.

 

I thought I would perhaps start my testing based at or around 2.330"

 

Bullet length for 77gr SMK .997"

Bullet length for 77gr TMK 1.066"

0.069" difference or 1.75mm

 

Standard COAl of 2.260" + TMK difference = 2.329" (59.16mm)

 

So that was born from adding the difference in bullet length between the SMK and TMK and should benefit from being slightly closer to the lands whilst providing the same case volume as it's SMK sibling. All in aid to avoid any powder crunch.

 

Hopefully work up to a safe load using my N140 and try altering seating depths later on down the road......

 

 

I can certainly echo Lauries findings here with the 69 TMKs anyway. Best groups shot with those were with surprisingly long jumps. I settled for a COL of 2.26" using 23.6gr N140 for 2780 fps which was a lightly compressed load. I tried various seatings but best results were either close up to the lands (within 15 thou) or over 100 thou. I haven't tried the 77gr but would expect them to be similar. How much of the good uniformity of ES and SD achieved along with some of the tiny groups shot that was attributable to the compressed loading as much as the jump, I don't know. Certainly, seating at 15 thou and raising the loads to 24.5gr also seemed to provide some good groups.

[markymark]

Thank you VarmLR for your insights too, I'm hoping I can actually get back to you guys with some results soon! I've either been busy or the weather has been horrendous.

 

Instead of starting another thread I thought I would consult the oracles again. Thanks to Spud I have my new shiney Magentospeed and hope to test out all my loads shortly. The question is, how much does the weather and in this case the cold affect MV? I know it has some effect but just how much? When I manage to shoot next it will certainly be single figures and perhaps only just above freezing. Obviously I am looking to hit a good velocity whilst working up my loads but how much do I need to hold back when testing now compared to using the same round later on the year? Once I've found the sweet spot I want to make a large batch because I struggle to find the time.

 

Will the cold give me disappointing MV and or will they be safe to shoot later in the year when temps are higher?

 

Thanks again,

 

Mark

[MrCetrizine]

Velocity at the muzzle will be essentially unchanged within measurable tolerance. Velocity at distance changes due to air density which is altered by temperature, humidity and altitude.

 

So as your chrono measures at the muzzle, you'll get the same readings regardless of weather.

[gbal]

Mark,MrC is right about the effects of ambient air temperature on bullet flight-velocity beyond the muzzle is essentialluy a function of air density,with temperature involved.

 

Not so sure there is wide agreement about no effects of temperature within the rifle/ammo .I'd check some of this out for yourself-it's another rather complex topic,but consider:

 

Target shooters try to keep their ammo at a known temperature (close to what they have it calibrated during load dev/previous shooting (eg use of cool boxes when it gets hot-as it does in US,UK less potential extremes- Still,they think it matters.....

 

You will find much advice to allow for increased pressure (NB not simply velocity) when winter loads are used in summer (see below for some data)

 

Varied authorities quote something like one C/F degree is about equivalent to 1/1.5 fps velocity change-it may not be completely linear over the temp range,and......but that isn't always separating rifle./ammo tempand air temp....see below...

 

Powders are marketed at least ,as to their 'temperature insensitivity' ie their resistance to temperature changes (Varget is one such;again probably more critical when temp changes can be large...but again,some reloaders take this into account...

 

Powder temperature at ignition is important-it relates to maximum average peak pressure (and of course,ammo powder temp is related to outside temperature,if in rifle for a few minutes.....so....

 

Kestrel Meters conducted very well controlled tests-ammo kept at various temperatures was quickly loaded in various rifles (AI,Blaser Tac< custom REm) and fired with the same ambient air temperaures and range conditions. They found varying effects on POI (scope shifts,even rifle barrel diameter controlled etc etc!)-not huge,but there-and cartridge temperature was the only variable....

 

Shooter Ballistic "Calculator for IOS and Android" advises: 'enter data (muzzle velocity variation per degree' and Shooter adjusts MV based on current powder temperature'.

 

So,"the prudent man" would take this on board-since we cannot measure pressure directly,best make some allowance for likely increased velocity from the same powder load as temperature increases-especially near publushed maxima; maybe ball park 1c degree gives 2+ fps (1degree F gives 1fps)......of course,that's what a good chrono like the magneto can verify-or not...you just have to await the weather....

 

 

Interesting,isn't it :-)

 

gbal

[VarmLR]

I've found that temperature is a factor for MV at the muzzle, due to the temperature sensitivity of the powder used. Some of my hotter loads developed in the spring started to show pressure signs on the brass in the heat of summer. Conversely, some of my loads developed in the summer were a full 50fps down or so during some very cold weather. It depends entirely on the temperature sensitivity of the propellant used and how the ammunition is stored.

 

You can store ammo at room temperature in a coolbox during the cold weather and when chambered, there ought to be little MV difference unless you leave it around long enoug to cool down,. You can also use the coolbox trick in summer if you have some hotter loads. Won't work for stalkers (I keep the bullets on an inside jacket pocket to use bodyheat to keep them warm when carrying spares) but never use hot loads for stalking anyway, so heat is never an issue.

[markymark]

Update:

 

So I'll only really just managed to get my test loads to the range. Please see below:

 

 

 

 

 

 

 

Not sure if they are pressure signs on some of the rear cases on the far right being the 24.5gr of N140 load. However at my max load, but not the most accurate MV was only 2,664. Not sure if to be disappointed with this or not as others have achieved more MV with less powder (also N140 for 20" barrel)

 

Thoughts welcome.

 

Many thanks,

 

Mark

[MrCetrizine]

2.35” is long for a TMK. It would put it well into the lands on my rifle and may explain the cratering you're getting on the 24+ gn loads.

 

I take it you meant 2,664 FPS not 1,664 as that would be a massive issue. 100+/- FPS difference from one rifle to another even with similar characteristics is normal and may be changed by seating a little deeper, changing primer, altering neck tension, etc.

[markymark]

Thanks for the reply. Yes my mistake, 2664 fps!

 

The extended COAL was in fact one of the (or the) best permorming bullet, all be it a very small test group. Only the initial testing, but gives me a good idea which ones to develop. At 2.36" the OGIVE is still not in the lands and still room yet to go longer if I wanted.

 

Could you please explain why a longer COAL might produce pressure signs over standard. Standard COAL is a compressed load, and I was under the impression that compression causes pressure spikes.

 

Cheers,

 

Mark

[MrCetrizine]

If you jam the bullet into the lands then it has both the static friction of the neck and the compression by the lands to overcome in one instance. This leads to a pressure spike.

 

Whereas, seating with a jump gives the bullet time to move before engaging the rifling which allows the initial pressure buildup to be slightly relieved before the next point of resistance when the bullet hits the lands.

[Laurie]

Yes, as per the previous reply. Also, a compressed charge does not in itself change pressures at all. This is a very widely held but quite incorrect belief. Over compressed loads may create other other problems and/or be a symptom of having chosen an inappropriate powder for the application, but doesn't change pressures except in some extreme specialised cases.

 

If the loading is really massively compressed, in theory at any rate enough powder kernels are damaged / crushed to change their burning rates to something faster. This was always believed to be a bigger threat with ball powders as they rely very heavily on their deterrent coatings to control burning rates. Crack enough little balls open goes the thinking and those kernels start the burn much more readily pushing peak pressures up. However, think about a cartridge - you'd have to have enough charge compression by the bullet base to distort the very ductile brass case long before you'd smash up enough of the charge to start having problems. It would also be much more likely to happen with straight-wall designs where the bullet base diameter is almost the same as that of the case and is less likely to happen with a bottle-neck design using a boat-tail bullet like the 77s in 223 Rem.

 

There are potential problems though. In the absence of a cannelured bullet and heavy case crimp, over compression can see changes in COALs, both across the board with COALs increasing as compression increases, and also in terms of variations between individual cartridges. Using a really compressed charge of N165 in 7mm-08 recently, I got a 10 thou' COAL increase with my heaviest charge weight. Had I been running with a tiny bullet jump or with a mild placement in the lands, this could have seen real pressure increase issues, but with a 15-20 thou' clearance, bullets were still being jumped albeit by a lot less.

 

The H.P. White Laboratory found in experiments in the 1950s in .30-06 that very heavily compressed charges, also those that were very heavy and had been 'settled' using vibration or a slow pour through a very long drop tube gave considerably larger ES / SD values than equivalent pressure loadings which allowed the powder to be poured into the case normally. It was ascribed to the densely packed and aligned kernels impeding charge penetration by hot primer particles resulting in ignition / early charge burn inconsistency. (This was in the days of very long grain 'log' powders, and may be less of an issue with modern short-cut types.)

 

On the large bore straight-wall case + ball powders, Winchester-Western was apparently unconcerned by common fears here when it designed and introduced the first all-American African dangerous game cartridge the .458 Winchester Magnum in 1956. It was deliberately made small (compared to British Rigby and H&H etc designs) to fit an unmodified Winchester 70 action, but resulted in barely enough case capacity and a very heavily compressed / crimped set-up with the Winchester ball powder used. In testing etc, Winchester was happy (although many African rifle specialists like Terry Wieland are very critical of taking a cartridge like this to hot environments - the English companies left lots of air-space around the Cordite charges in their cartridges for very good reasons). However, when the cartridge and rifle had been on sale for a couple of years, horror stories of hangfires and squib load firings became widespread - bullets with such low velocities they cleared the barrel but hit the ground 20 yards in front of the muzzle and bounced along the ground! Winchester technicians couldn't replicate the problems until they tried ammo that had sat on the shelf for a year or two. Investigation showed that perfectly fresh ammo was OK, but when it sat for a while in this massively compressed state, the kernels became fused together causing big lumps of powder in the charge that wouldn't ignite or burn properly. (Bad news when you're shooting at something that can kill you!) Winchester had to change the loading to a less compressed form which also reduced MVs to get around it.

[VarmLR]

Update:

 

So I'll only really just managed to get my test loads to the range. Please see below:

 

 

 

 

 

 

 

Not sure if they are pressure signs on some of the rear cases on the far right being the 24.5gr of N140 load. However at my max load, but not the most accurate MV was only 2,664. Not sure if to be disappointed with this or not as others have achieved more MV with less powder (also N140 for 20" barrel)

 

Thoughts welcome.

 

Many thanks,

 

Mark

 

 

That bottom grouping is very respectable Mark. Your MV or 2664fps seems perfectly reasonable and about expected for the 77gr bullet. I get slightly more in mine (about 40fps more) but my barrel and chamber are different to yours.

 

Hard to tell exactly from the photos but your heavier loads closer to the lands seem to show some signs of pressure on the primers. The bottom picture shows the 24g and 24.5 charges for the longer COAL resulting in some flattening and spread of primers. Personally, depending on how close these were to the lands, I'd back off a bit, especially to account for any pressure rise due to increased burn rate with summer temperatures on the propellant. You don't seem to be getting the same issue at the shorter overall lengths , so it may be worth picking your best group at the 2.26 length and varying seating by say 20 thou each way to see of the node opens or closes. I'm guessing that you wont have much room in the cases at 2.26 when loading to 24 or more. I load to 23.6 N140 using 69TMKs at 2.26 COL. I have tried compressing the loads to around 105% of max volume with slightly improved results, but backed off a little when I started to get pressure signs, then played with seating depth to get the best results.

 

Laurie makes some very good points and gives very sensible advice about the use of compressed loads close up to the lands. Not a good thing to do imho when developing loads in the depths of winter!