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Posted: 4/20/2015 10:18:08 AM EDT
| If you've experimented with these, please post results and loads here. 77 SMK loads are welcome as well but please let us know which bullet you used. I notice the 77 TMK is longer than the SMK so I'm wondering if people are running into pressure issues from seating them further into the case. My goal is to push the 77 TMK to 2800 out of a 20" barrel. So far I was not able to do with the 8208 as I ran into a pressure spike at 22.9 grains. Case did not show issues, but velocity consistency went down considerably. |
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I was able to get 2,550-600 out of a 16" LaRue with the TMK over Varget and R15. I could not get the accuracy I wanted loading to mag length. Loading long and single loading I averaged right at .8 moa for multiple 5 shot groups.
I get better accuracy with the Berger 77 otm loaded to mag length so I am now using them. Use the search feature and you will find more specific data on the TMK's. |
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My best load for the 77gr TMK is the same I would use for the SMK 77gr and the Hornady 75gr match.
All are slightly over max. All get flattened primers but no other major pressure signs in my rifles. I load the SMK and Horn match to 2.245" I load the TMK to 2.255" All using PMC commercial brass CCi 400 primers IMR 8208 xbr 23.4gr I suspect using harder primers, the primer flattening would most likely go away. .5-.75moa avg with 5 shot groups. Have done 10 shot groups around .75moa. Chrono'd a small sample recently. These were loaded by dropping charges straight from the LEE perfect powder measure. I did not hand weigh each charge. 5 round sample out of an 18" barrel 2652 2682 2681 2653 2667 That being said, I think I prefer the 75gr Hornady out of all of them...but I plan on really working the TMK in smaller than .3gr increments in the near future. |
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77 TMK
23.6 TAC FC Primed pull down brass with a light crimp. 10 shot groups at 1.05-1.1 MOA avg so far. Still working on XBR 8208 loads at the moment, showing promise between 23.0 and 23.4 with Tula 5.56 primers. No crimp on the XBR loads. OAL is 2.245 on all loads. Trying to get a load under 1 MOA to shoot the challenge. These loads are out of an 18'' WOA SPR barrel. |
| Your guys' loads with 8208 are in line with what I was expecting. I loaded it from 22.3-22.9 and ran into a pressure spike going from 22.7 to 22.9. Accuracy and standard deviation were excellent up to 22.7. At 22.9 the bolt failed to lock back despite the lower charges doing so and the SD went from single digits or close to them to 30fps. Velocity jumped almost 100 fps going from 22.7 to 22.9 grains of 8208. |
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Your guys' loads with 8208 are in line with what I was expecting. I loaded it from 22.3-22.9 and ran into a pressure spike going from 22.7 to 22.9. Accuracy and standard deviation were excellent up to 22.7. At 22.9 the bolt failed to lock back despite the lower charges doing so and the SD went from single digits or close to them to 30fps. Velocity jumped almost 100 fps going from 22.7 to 22.9 grains of 8208. This is my first time using XBR and have read about other guys seeing pressure spikes that your describing. I started right at 23.0 and ran .3 increments up to 23.6, on the first try out loads 23.0 and 23.3 groups were nearly identical and 23.6 began to open up. I really need to buy a chronograph. |
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Quoted:
If you've experimented with these, please post results and loads here. 77 SMK loads are welcome as well but please let us know which bullet you used. I notice the 77 TMK is longer than the SMK so I'm wondering if people are running into pressure issues from seating them further into the case. My goal is to push the 77 TMK to 2800 out of a 20" barrel. So far I was not able to do with the 8208 as I ran into a pressure spike at 22.9 grains. Case did not show issues, but velocity consistency went down considerably. OP, The factory BHA 5.56MM. 77GR. TMK load shoots very well at mag length of 2.248". The 0.72" 5 shot group below included the fouler round at 7 o'clock fired from a clean/cold bore. And 69GR. & 77GR. TMKs over 5.56MM pressure TAC & IMR 8208 XBR handloads are easily shooting sub MOA. I need more benchrest/chrono time to refine them further especially when approaching full 5.56MM NATO pressure level but I think I can get them close to 0.5 MOA @100yds. in good conditions. They were kept at mag length of 2.255" or less for hunting and they have made 70+ whitetail/bobcat/varmint kills so far this season with excellent terminal performance even from short 10.0"/10.3"10.5" barrels. TAC will yield higher MV at warmer propellant temperature but IMR 8208 XBR loads are almost immune to thermal variation from -10F to +135F. HTH. 
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Took some loads out again with 77 SMKs loaded to 2.260, just short enough to work in a pmag. Powder was 8208 XBR and I continued to use geco once fired brass and CCI BR4.
22.6 was stupidly accurate: 
Measured .332" at 100 yards Unfortunately the chrono data was not so good. 2691 average 70 fps ES with SD of 26. However I noticed one round was considerably further off than the rest and if I omitted it SD dropped to 14. 22.7 was not quite as accurate with a .580" group but had an average velocity of 2720 and SD of 10. Going to 22.8 and 22.9 is where things got interesting. At 22.8 accuracy opened up to the .7 range and SD jumped to 30 fps. Velocity was not noticeably different from 22.7. At 22.9 accuracy was slightly better than 22.8 but SD dropped to 7 fps. The velocity at 22.9 actually dropped this time to below that of 22.7 and 22.8. I have no idea where these discrepancies come from or why they are so far off my first day of testing. The good news is my order for 77 TMKs came in today and I will be trying those out this weekend. |
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One of the guys from SWA put their 5.56MM 77GR. SMK load data in print years back but I pulled one down to verify the charge weight was in fact 23.8GR. Chamber type has a big effect on max charge a barrel will allow. The Colt 5.56MM & CLE 5.56MM Match chambers I have behave the same with that load and all other 5.56MM I have fired to date. Many civi shooters on SH including myself have used that 23.8GR load or the SWA factory load for years. MV is within 4 FPS of the BHA 77GR. SMK AMU load & both loads usually group 0.5 MOA or better in an accurized AR15/M16. But the BHA AMU load uses a spherical propellant so is a bit thermally sensitive (about 1 FPS/degree F). The SWA 5.56MM factory load or an 8208 handload doesn't care what the OAT or barrel temp is within reason. If you can put your bare hand on the barrel and not freeze to it or burn yourself, 8208 shoots virtually the same. Same with H4895 but IMR 8208 XBR tightened up the ES/SD just a bit and consistently throws within 0.1GR for me. Here are some thermal sensitivity numbers on several propellants at full 5.56MM NATO pressure and a couple factory 5.56MM 77GR. SMK loads.
All loads fired from 18" SS 1x7.7 Krieger/CLE 5.56MM Match chamber barrel: 
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So my first attempt at loading TMKs totally failed:
Left to right: 77 TMK loaded to mag length(squashed shoulder), 77 SMK loaded to mag length, 77 TMK loaded as deep as it will go. I seated my first one at the same die position as I did with 77 SMK loaded to mag length. The TMK round ended up being 2.315 or something along those lines. I then adjusted the die to seat it deeper for the next round. It ended up squashing the shoulder of the case as pictured.I then tried it on an empty case and still squashed the shoulder as before. Anybody have a clue on what happened? My guess is that my redding die (with crimp) is not designed for bullets this long and put the crimp on prematurely. But this is just a guess. I then tried to load more by not pulling the level down all the way, but stopping once I felt resistance. The shortest I can get the cartridge is 2.304, which is still too long to fit in a mag. Anybody have suggestions? |
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Yikes!
I personally do not crimp with the seater die. I actually don't crimp much of anything anymore, aside from some handgun and some 55gr loads that are designated for hard use/plinking. If I were to crimp any rifle round, it would be with a lee factory crimp die and it would be a light crimp at that. Were you adjusting the whole die down to seat deeper? |
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Yep, that's exactly what was happening. I realized it as soon as I woke up this morning. I try to never load ammo after 2300. Things like this always happen when I do.
I adjusted the die properly, with no crimp and the 77 TMKs seated to mag length. It seemed to compress the shit out of my powder. It's a relatively light charge of 22.5 grains of 8208 so I can't imagine what would happen if I took it up. I have a hard time seeing how I would fit 24ish grains of varget in there. |
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There is a trick to loading long & ultra-long bullets such as the SMK/TMK/TSX/TTSX especially over heavy charges of stick rifle propellant for those using arbor dies. I start the bullet into the case using a Wilson micro seater arbor die then invert the die to fully seat the bullet to the desired COAL. This allows gravity to work for you in displacing the propellant to the side of the bullet as it is pressed into the case & also allows the bullet to be seated with much reduced pressure eliminating bullet tip distortion. Spherical propellants such as TAC easily flow around the base of the ultra-long 70GR. TSX bullet as it is seated using normal techniques.
EDIT: This is not my first rodeo as I have been handloading for about 43 years now. If you are using standard threaded dies, the technique is to partially seat the bullet to the point where you feel resistance, remove the cartridge from the shell holder, invert & shake, then return to the shell holder for final seating of the bullet. I have successfully seated the 70GR. TSX over more than 25.0GR. of Varget using this technique. Barnes 5.56MM NATO data on the 70GR. TSX goes well above 25.0GR. Varget but it is the responsibility of the handloader to work the load up in their individual barrel using accepted practices. We have credible 5.56MM NATO pressure load data on several propellants now but IMR 8208 XBR is not yet one of them. Work it up slowly using 0.1GR. or at most 0.2GR increases on heavy charges. IMO, increasing charge weight by more than 0.2GR. on heavy 5.56MM NATO charges is excessive due to the small case volume of the .223/5.56MM cartridge case. Use caution guys. |
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I went to the range to test the TMKs out today. I only took 8 rounds with me because I had messed up loading. I had also installed a new trigger in this rifle. Accuracy was not nearly as good as the SMKs, but still sub-moa. Every single shot I took today felt bad because I wasn't used to the new trigger. Too light. The velocities were way low. 22.5 grains of 8208 only clocked 2670 or so. I also had one click no boom. When I extracted the round, it had a nice strong primer strike. However I noticed the primer was above flush with the base of the case, and I know I seated it below flush. Is it possible that since I compressed the shit out of these rounds that I somehow damaged the primer? I have no idea why that round did not go off. I will try again tomorrow with more loads.
I had to seat the TMKs significantly deeper into the case compared to the 77 SMKs. I'm thinking that may have had something to do with the accuracy as well. |
Range day today! All groups below are with 77 grain TMKs loaded to 2.260" and fed perfectly out of a PMAG.
I had previously settled on 22.6 grains of 8208 XBR as my most accurate with both SMKs and TMKs. My rifle doesn't quite like the TMKs as much as the SMKs. I'm thinking it has to do with the increased amount of jump needed to get to mag length. It clearly does not like the varget loads, so I am done with varget. There was a noticeable difference in velocity from the GECO brass and the IMI brass. I have some Lapua brass now that I will try on my next outing. I made the mistake of installing a new trigger on this rifle that I'm not quite used to yet, so I'm not sure if the groups with horizontal dispersion are due to the trigger or me. I called quite a few shots that were "eh could have been better", but no bad pulls. I've been having issues with my scale, so I borrowed a friend's chargemaster for the next attempt. If I weigh a charge with my current scale, then take the charge off and put it immediately back on, it will give me different weights, sometimes off by .3-.4 grains.If anybody has suggestions to try, I'm open to them. At the moment I'm starting to wonder if the increased BC of the TMKs are worth the accuracy loss over the standard 77 SMK. |
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Went to the range this morning, thinking with XBR i'm going with a charge of 23.4 gr. No pressure signs and an OAL of 2.245. I'm going to load up some more of the 23.4 when my new dies come in tomorrow and shoot again to see if I can do any better. <a href="http://s826.photobucket.com/user/DirtyMoe21/media/77TMK_xbr_23.4_zpsfyrxnccm.jpg.html" target="_blank">http://i826.photobucket.com/albums/zz182/DirtyMoe21/77TMK_xbr_23.4_zpsfyrxnccm.jpg</a> Looking good! 23.4gr XBR @ 2.245oal is my go to load. I worked that one up hard, and while there were other good accuracy nodes, the 23.4 had the exact velocity I was looking for. The great thing about that load is it works in ALL of my ARs. From the 10.5" pistol, up to the 18" spr and everything in between. 10.5" 1:8, 14.5" 1:7, 16" 1:9 18" 1:8 all shoot great. |
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So I totally fucked up my test yesterday:
1. I used a chargemaster I'm borrowing instead of the scale that I've been using. 22.6 on the chargemaster was lighter than 22.6 on my scale, so these charges were not in the node I had found previously. 2. I forgot to bring my rear bag to the range so I improvised. Probably not as accurate as my rear bag. Velocity results: "22.6" grains of IMR 8208 (really 22.4-.5 according to my scale), 77 TMK loaded to 2.260 in Geco brass: 2692, 19.7 SD "22.6" grains of IMR 8208 (really 22.4-.5 according to my scale), 77 TMK loaded to 2.260 in Lapua brass: 2669, 12.4 SD "22.6" grains of IMR 8208 (really 22.4-.5 according to my scale), 77 SMK loaded to 2.260 in Geco brass: 2689, 5.1 SD "22.6" grains of IMR 8208 (really 22.4-.5 according to my scale), 77 SMK loaded to 2.260 in Lapua brass: 2656, 14.2 SD Picture of groups to come, but nothing special. Really the only thing I can conclude from my results is that loads with Geco brass is consistently faster than IMI and Lapua. Accuracy difference between SMK and TMK was minimal. I will have to redo the test with proper equipment and charge. |
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So my first attempt at loading TMKs totally failed: http://i1092.photobucket.com/albums/i408/lennyo3034/20150422_235526_zps3qsx1zvj.jpg Left to right: 77 TMK loaded to mag length(squashed shoulder), 77 SMK loaded to mag length, 77 TMK loaded as deep as it will go. I seated my first one at the same die position as I did with 77 SMK loaded to mag length. The TMK round ended up being 2.315 or something along those lines. I then adjusted the die to seat it deeper for the next round. It ended up squashing the shoulder of the case as pictured.I then tried it on an empty case and still squashed the shoulder as before. Anybody have a clue on what happened? My guess is that my redding die (with crimp) is not designed for bullets this long and put the crimp on prematurely. But this is just a guess. I then tried to load more by not pulling the level down all the way, but stopping once I felt resistance. The shortest I can get the cartridge is 2.304, which is still too long to fit in a mag. Anybody have suggestions? The bullet has a different ogive.... so it is going to crimp at a different place. Man, I'd seriously stop crimping at all, and I'd damn sure not crimp while seating. That's no recipe for accuracy. Either don't crimp, or crimp with a Lee factory die in a separate stage. |
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I've already stopped crimping. It was really a brain fart late at night when reloading.
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Lennyo3034, if you want to get a longer mag, check the ASC one ,their description states: The interior dimensions of OAL 2.316” ± .002 are perfect for reloads. http://www.ammosc.com/223-stainless-steel-10-rd-magazine/ My particular lower does not get along well with ASC mags. I tried 6.5 Grendel in this rifle and I had all sorts of feeding issues with this rifle. Perhaps the .223 mags would work better. However I'd like to F-AR class matches and they limit round OAL to 2.260. I have a match in two weeks so we'll see how it goes. |
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Update: Ran into a friend at the range doing the same thing yesterday.
He was running: LC brass, fed primers, 23.6 IMR 8208 XBR, 77 TMK. Accuracy was not quite as good as he said the rifle was shooting with the same load using 77 SMK. Velocities actually dropped from 2750 to 2700ish. Is it possible that he's packing too much powder into there and it's causing weird velocity issues? There did not appear to be any pressure signs on his brass. 2700 seems pretty slow for 23.6 grains, especially considering I'm getting higher than that with a full grain less powder. |
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