Author Topic: Ogive Length vs. OAL Data for Krieger chambered barrel  (Read 451 times)

Offline KRC

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Ogive Length vs. OAL Data for Krieger chambered barrel
« on: May 26, 2019, 09:42:36 AM »
Sharing this OgiveL and OAL info, which my be known to many, but surprised me.

I finally got around to drilling and tapping a 224V case for use with a “Chamber-All & OAL” tool and taking some seating-depth-to-lands readings. I was quite surprised at the results. Barrel is a Krieger 6.5T, chambered by Krieger.

Below I’ve indicated the measured “Ogive Length” using the “22” caliber measuring bushing included with the tool, as well as the OAL of the cartridge with the seated bullet, for the three bullets I’ve concentrated on with my 224V loading. Measured seating depths were with very light contact of the bullet to the lands. Readings varied about +/- .003”.

               77 SMK               88 ELD-M               90 SMK
OgL       ~1.815”                  ~1.790”                ~1.820”
OAL       ~2.220”                  ~2.330”                ~2.320”
Diff:         .385"                       .540"                    .500"

What surprised me was that I have been loading OAL’s from 2.260” to 2.320” thinking I was well into the lands at OAL’s much over 2.260”. Apparently, I have only been loading the 77 SMK’s at or into the lands.

My results to date have been somewhat frustrating. (Besides the frustration of the 88 ELD-M tip breaking issue.) I have achieved acceptable precision only with the 77 SMK’s, close to acceptable with the 88 ELD-M’s at OAL’s of ~2.290”, and completely unacceptable precision to date with limited 90 SMK testing, but only tested at ~2.265-2.270” OAL’s.

The 88 ELD-M results appear to be consistent with those who report that these bullets like to “jump”, with the jump of ~.040" at an OAL of 2.290".

Even with a “window” mag, I don’t think I’m going to be able to load the 90 SMK’s into the lands, where I suspect improved precision may be lurking.

I have loaded with 2000MR, RE15, H4895 and Varget, with Varget showing the best overall performance. My next batch of testing was to be the heavy bullets with H4895 and H4350 (completely opposite burn rates?), but I’m now thinking of returning to Varget with as-long-as-possible OAL’s with the 90 SMK’s.

Offline Hammerhead

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Re: Ogive Length vs. OAL Data for Krieger chambered barrel
« Reply #1 on: May 27, 2019, 08:06:32 AM »
Looks like your results are similar with mine. 88's seated at 2.306 is max for my mag and they would give .5 performance with RE-15 and had good velocity. 90 SMK seated at the OAL would never give less than .750. 95SMK seated well beyond mag length to get as close to the lands as possible would give quarter moa but I didn't want to have to hand feed an autoloader. The biggest breakthrough for my rifle was hybrid bullets like the Berger 82bt. They will shoot quarter moa out to 600 and of course they are discontinued now. Haven't tried any of the new 83gr offerings as they are only available in factory ammo now but I suspect their performance to be close.

Offline Furdown

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Re: Ogive Length vs. OAL Data for Krieger chambered barrel
« Reply #2 on: May 27, 2019, 01:33:20 PM »
KRC,  Hammerhead,  I just received an order of 85 Grain Barnes Match Burners.  I could not find any load data for them so I called Barnes.  I told them I was using RL-15 and they gave me 23.4 min and 26 max.   The Barnes Match Burners must have the Ogive further forward. I'm touching the lands at a COAL of 2.225. Definitely no magazine length issues with this bullet. 
 To measure COAL I'm using a home made tool using the split case method. I backed of 5 thous and loaded 10 rounds at 25 grains, 10 at 25.5 grains and 10 at 26 grains. At 100 yards the  26 grains was the most accurate with sub MOA but there were unacceptable pressure signs.  25.5 grains also gave sub MOA results.  25 Grains gave 1.5 MOA results.  There could be more accuracy nodes below 25 grains but my range time was limited. The weather closed in on me before I could get any Velocity data.  When I do I'll post them.   KRC,I'm still shaking  broken 88 ELD tip out of my suppressor !