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Posted: 8/5/2013 7:33:53 PM EDT
| So I am loading for my new .260 remington build and I am really scratching my head over what COAL to start with. My Lee book shows 36grn as a starting load and 41grn as a max load for Reloader 17 with a COAL of 2.745. Now enters the confusion, I Am shooting Berger 140 VLD's in a 26" CBI barrel that has .080 free bore. I have been reading that VLD's like to be seated long in the .260 and with my free bore I don't want to jump too far. So do I start with the recomended load and play with length later or can I start with a longer COAL like 2.880. And if I do set them longer can I still use the listed starting and max charges or do I need to make a change to that too. |
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you can seat bullets as long as your magazine will let you. always chamber and unload new rounds a few times and inspect the bullet tips for rifle marks.
as a general rule try to only change one thing at a time. Just try standard length first find an accurate load then start loading them longer. At this point if you are way over the COAL you can start thinking about adding more powder in 0.2 gr increments. |
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If you are limited by Magazine length then seat your bullets so they fit into the mag. Do not worry about Lee's OAL, it means nothing to you and YOUR rifle.
If you are not limited by Mag length then find your Max OAL for your choice of bullet and bullet weight and reduce by desired amount. At this point if you are way over the COAL you can start thinking about adding more powder in 0.2 gr increments. Do not do this. This is bass ackwards. The longer your OAL the closer you are to the lands. The Closer you are to the lands the higher the pressure. Find your Max OAL, either by Mag length or chamber length and start there, Use your published starting load. Do not go below "start" loads. Work your way up looking for accuracy and pressure. If you need to adjust your OAL shorter you can do so without pressure worries as seating deeper will not increase pressures, in fact it will reduce them. |
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Quoted:
If you are limited by Magazine length then seat your bullets so they fit into the mag. Do not worry about Lee's OAL, it means nothing to you and YOUR rifle. If you are not limited by Mag length then find your Max OAL for your choice of bullet and bullet weight and reduce by desired amount. Do not do this. This is bass ackwards. The longer your OAL the closer you are to the lands. The Closer you are to the lands the higher the pressure. Find your Max OAL, either by Mag length or chamber length and start there, Use your published starting load. Do not go below "start" loads. Work your way up looking for accuracy and pressure. If you need to adjust your OAL shorter you can do so without pressure worries as seating deeper will not increase pressures, in fact it will reduce them. Quoted:
If you are limited by Magazine length then seat your bullets so they fit into the mag. Do not worry about Lee's OAL, it means nothing to you and YOUR rifle. If you are not limited by Mag length then find your Max OAL for your choice of bullet and bullet weight and reduce by desired amount. At this point if you are way over the COAL you can start thinking about adding more powder in 0.2 gr increments. Do not do this. This is bass ackwards. The longer your OAL the closer you are to the lands. The Closer you are to the lands the higher the pressure. Find your Max OAL, either by Mag length or chamber length and start there, Use your published starting load. Do not go below "start" loads. Work your way up looking for accuracy and pressure. If you need to adjust your OAL shorter you can do so without pressure worries as seating deeper will not increase pressures, in fact it will reduce them. Ok so since AI mags without modification will hold me to no more than 2.880 I will start there and begin with Lee's published starting loads. then work up from there in .5gr increments. |
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Here are a couple of recipes from another site for comparison.
1. This is a load Zak Smith of DEMIGODLLC.com uses for his .260 Rem during competition. Lapua .243 brass expanded, turned, sized, fired, reamed, then sized again. Seated 0.005" into the lands makes it a tack-driver,... at least with my rifle.
This is considered a MEDIUM load by the developer. [No COAL listed]. 2800 fps, 26" bbl. The next accuracy node for my rifle seems to be 43.5gr of H4350 with this bullet. While still very accurate, it seems to run a little hot i.e. primer pockets expanding and flattened primers. 140 gr VLD berger OTM over 40.7 gr H4350 ============================================== 2. This load was developed using Berger very low drag (VLD), jacketed, hollow-point, boat-tailed, match bullets (Target VLD).
In terms of power, the developer considers this a MAXIMUM load. The velocity measurement is by chronograph. Winchester cases and CCI 200 primers were used in development. 2915 fps, 26" bbl. COAL 2.820. COMMENTS: No pressure signs whatsoever in my rifle, but this is over "book" max. Start at 40gr and work up. I'm necking down Winchester 7mm-08 brass. Also tried Federal 210M with this load, but SD not as tight. With the CCI200s SD is only 4 fps. This load is consistently around a 0.5-0.6 MOA performer. I've shot down in the 0.3-0.4 range with it many times. Only 7.2 MILs elevation to 1k yards. 140 gr VLD berger OTM over 42.6 gr Reloder-17 So, as one can see, if you start setting up things so you are into the lands, you should definitely back off to "start" values and work up, looking for pressure signs. Hornady (stony point) makes some gages to help gage the land distance setup you need. Case head surface to ogive/land contact is what you are going to measure, then subtract or add as you see fit. |
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Straight from Berger
The folks at Berger Bullets have just released an interesting technical bulletin that describes methods for optimizing bullet seating depths with Berger VLDs. The document explains how to find the OAL “sweet spot” for VLDs in your rifle. Interestingly, while VLDs commonly work best seated into the rifling .010? or more, Berger’s research indicates that, in some rifles, VLDs perform well jumped .040? or more. This is a significant finding, one that’s backed-up by real-world testing by many shooters. The key point in Berger’s report is that: “VLD bullets shoot best when loaded to a Cartridge Overall Length (COAL) that puts the bullet in a ‘sweet spot’. This sweet spot is a band .030? to .040? wide and is located anywhere between jamming the bullets into the lands and .150? jump off the lands.” CLICK HERE to download Berger VLD Tuning Tips Writing in the report, Berger’s Eric Stecker observes: “Many reloaders feel (and I tend to agree) that meaningful COAL adjustments are .002 to .005. Every once in a while I might adjust the COAL by .010 but this seems like I am moving the bullet the length of a football field. The only way a shooter will be able to benefit from this situation is to let go of this opinion that more than .010 change is too much (me included).” For target competition shooters (for whom it is practical to seat into the lands), Berger recommends the following test to find your rifle’s VLD sweet spot. Load 24 rounds at the following COAL: 1. .010? into (touching) the lands (jam) 6 rounds 2. .040? off the lands (jump) 6 rounds 3. .080? off the lands (jump) 6 rounds 4. .120? off the lands (jump) 6 rounds Berger predicts that: “One of these 4 COALs will outperform the other three by a considerable margin. Once you know which one of these 4 COAL shoots best then you can tweak the COAL +/- .002 or .005.” OBSERVATION and WARNING Berger may definitely be on to something here, and we applaud Berger’s testers for testing a very broad range of seating depths. However, we want to issue a STRONG WARNING to reloaders who may be inclined to try the 4-step method listed above. Be aware that, as you load your cartridge progressively shorter, putting the bullet deeper into the case, you will be reducing the effective case capacity dramatically. With smaller cases, such as the .223 Rem and 6mmBR, moving from .010? into the lands to .080? and .120? off the lands can CAUSE a dramatic pressure rise. So, a load .010? into the lands that may be safe can be WAY OVERPRESSURE with the bullet seated .120? off the lands (i.e. .130? deeper in the case, the difference between .010? in and .120? out). To illustrate, using a QuickLOAD simulation for the 6mmBR cartridge, moving the bullet 0.130? deeper into the case can raise pressures dramatically. With the Berger 105 VLD seated .010? in the lands (with 0.220 of bearing surface in the neck), and a charge of 30.0 grains of Varget, QuickLOAD predicts 60,887 psi. (This is using ADI 2208 data, and a 5500 psi start initiation value). If we move the bullet back 0.130? further into the case, QuickLOAD predicts 64,420 psi (even after we drop start initiation pressure to the “default” non-jammed 3625 psi value). The 64,420 psi level is way higher! Cartridge & LoadCOALJam/Jump*Start PressureMax Pressure 6mmBR, 30.0 Varget Berger 105 VLD2.354?+0.010? in lands5500 psi60,887 psi 6mmBR, 30.0 Varget Berger 105 VLD2.324?-0.20? JUMP3625 psi59,645 psi 6mmBR, 30.0 Varget Berger 105 VLD2.264?-0.80? JUMP3625 psi62,413 psi 6mmBR, 30.0 Varget Berger 105 VLD2.224?-0.120? JUMP3625 psi64,420 psi * As used here, this is the variance in OAL from a load length where the bullet ogive just touches the lands (first jacket to barrel contact). Loading bullets to an OAL beyond that point is “jamming” (seating bullet into lands), while loading to an OAL shorter than that is “jumping” (seating bullet away from lands). NOTE: This is only a software simulation, and the real pressures you encounter may be different. But, the point is that moving the bullet 0.130? further down in a 6mmBR case can raise pressures more than 3,000 psi! Therefore, you must employ EXTREME CAUTION when moving your bullets that much in a relatively small case. Remember that going from .010? jam to a very long jump will probably increase pressures in your cartridge so you MUST adjust your load accordingly. |
| Ok so it looks like it really would be advisable to do a new workup each time I change OAL. Thank you all for the help. This has been very helpful. I like Bergers 4 step idea for finding the sweet spot. Looks like I have a lot of shooting to do to dial this one in. Sounds like fun! |
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