Quote:
Originally Posted by Salavee
Why is it that modern velocities for the 6.5 x55 are always omitted? .. there's gotta be a reason when these comparisons are made.
Try running the pressures up to 58K psi with the same bullet (147 ELD-M) and lets see what it really does .
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I would like to point out to you that the 6.5x55 Modern Sako 139 HPBTM factory ammo at 2990 MV was the best Factory ammo I could find and the 142 SHPBT was the Max load, 46,100 CUP or likely near 58K, in the Hodgdon Manual. All of the other factory loads I could find were closer to Grendel Performance than 6.5CM. That is the reason and if you actually look at the chart the 6.5x55 Sako load actually performs very similar to the 147 ELD-M Factory round in 6.5CM.
Let's see if you are happy with a comparison of the 6.5 x55 and 6.5 CM with the 143 ELDX seated out to maximum magazine length, 3.150", which is about a 0.150-0.200" jump to the lands according to one fellow who did it. I will post a drawing to show how he set it up. As you will see he reported a compressed load of H-1000 yielding 2601. H 4831 Ladder had no velocities but 47.0 grains began to get stiff bolt and at 47.5 accuracy fell off. RL 23 yielded him 2860 with 1/2 MOA accuracy and a full load of RL 26 at 51 grains gave him 2990 with 1-1.25 MOA. Perhaps someone will post more favorable results. I have also included a drawing of the Military 156 RN bullet that was pushed by 37.4 grains of some sort of flake powder. Surprisingly it set up ahead of the neck shoulder junction with bout the same length as the 143 ELD-X without the Boat Tail. It seems that the pressures were kept down by having only 0.135" bearing surface at 0263" diameter instead of about 0.350" at 0.264" like the regular 6.5 bullets. the bearing surface then tapered up to 0.261" at about 0.350". This is how the old military round was able to keep pressures down as the Bearing surface barely toughed the lands.
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Drawing of the 6.5 CM with the 143 ELD-X seated to the lands points out the only flaw in its design which is that it could have had another 0.050" free bore to accommodate the 143 ELD-X or a 0.050" longer Boat Tail to keep Bearing Surface in the Neck. Ironically the Berger 140 VLD and Sierra 150 MK are a perfect fit if one had an intermediate length magazine like the 6.5X 55. If you look closely at the RL 26 ladder that I found posted on another site you will see that a full case, or slightly compressed load of 48 grains gave 2999f/s and a Compressed 49 grains ran 3050 with likely about the same pressure as the 51 grains in the 6.5X55. I really like the ES and SD through out the ladder but would like to see how it shoots at 46.5 grains giving over 2900 fps. Guess I should have added this to the chart as we did no handloads for the 6.5CM. However we can just use the Factory 143 ELD-X loads for the 6.5 PRC!!!!
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I hope that this satisfies your mind to the fact that we are not trying to run your pet cartridge down and that your pre-conceived notions are just that. At least the best comparison that I could come up with shows that the CM gets the 143 ELD-X to the same max velocity as the "Old Swede or Norwegian", with about 3 grains less powder much the same as the 7x57 versus the 7mm08. This is likely due to the fact that the CM is able to run to the lands in the same length magazine and the slightly smaller case capacity gets more pressure with less powder. I know it goes against everything we have been conditioned to believe but slight differences in case design do make a difference and a lot of times smaller is better. I think that you will find the same to be true for the 147 ELDM and 150 SMK as well.