Load dev. with155 Scenars for Designated Maksman Match

[twoatlow8]

I am getting ready for my first Designated Marksman Match. I have been told to expect 2MOA steel targets between 50 and 650 yards from field positions. It is a time plus penalties scoring sytem. One visible hit on steel scores. I intend to use Lapua Scenars for the match but I am starting from scratch with them and will need to verify the drop every 50 yards and make a data card. I only have 200 of them and will need 100 for the match.

I will load using a 2 step sizing method to reduce runout. Starting with a Lee collet neck sizer THEN a Redding body die. Hand prime, weigh charges, and seat bullets with a Forster Ultra seating die.

So I have;
-Remington Sendero in .308 Win (.6-.7 MOA with standard RCBS dies and the old 155 PalmaSMKs using Varget)
-PT&G bottom metal with Alpha Type II Magazines (ten round) Allows a max OAL of 2.950"
-200 new Lapua .308 cases
-200 155gr Scenars
-1000 old style 155 Palma MKs
-Plenty of IMR8208xbr
-Plenty of Varget

My questions are about reloading but if you have any other tidbits of wisdom related to shooting, wind, gear, or preparation, PLEASE include them. Here Goes.......

1-Should I full length resize the new brass, load some SMKs using an old recipe, and fireform them while practicing my field position shooting and then develop a Scenar load?..... OR is there a preferred method for working up a minimal runout load with my new brass? I want to use as few of the Scenars as possible in my development.

2-A reliable source has indicated that CFE223 is another good powder choice. Can someone rate the 3 powders in terms of fastest velocity to slowest velocity for a below max load?

3- Which powder would be more appropriate to use? I need to settle on one and develop with it due to the limited supply of Scenars.

4-Given that I can load out to 2.950" what OAL or "base to ogive" length should I consider as a starting point?

5-Is there anything different that you would do?

6- Is anyone scratching their head and asking, "Why doesnt he just use the SMKs, those are big targets." ?

Thanks in advance for any and all responses
Warmest Regards, Joe

 

[Dave P]

I get much better accuracy in 308 M-14 with SMK or Nolsler 155's. Scenars never cut the mustard for me.

 

[Unclenick]

…will need to verify the drop every 50 yards and make a data card.

Use the free exterior ballistics program at JBM. Set the ballistic coefficient type to G7 and use a value of 0.236, which was measured by Bryan Litz for the GB491 (I am assuming this is your bullet). That should be good to a about a quarter moa over the 50-600 yard range you mentioned. The more information you put in, the more accurate it will be, including all the atmospheric data.

1-Should I full length resize the new brass, load some SMKs using an old recipe, and fireform them while practicing my field position shooting and then develop a Scenar load?..... OR is there a preferred method for working up a minimal runout load with my new brass? I want to use as few of the Scenars as possible in my development.

In general, for fully resized loads, best accuracy comes from new brass never fireformed, so save 100 aside for that. This happens because most commercial chambers are at least slightly tipped out of square with the bore axis, so the fireformed heads will be slightly out of square and will touch different places on the bolt face first as they stretch back, adding a small and irregular recoil moment location. You can avoid that irregularity by always orienting the case head in the chamber the same way for firing. Easy firing single-shot, but not so easy feeding from a magazine. I don't know the rules of the game you are shooting in. Squad Designated Marksmen always were issued self-loaders of some kind, AFAIK, so the use of your Sendero makes it sound more like a general tactical course or a sniper course. But it will let you control load orientation if you aren't up against a clock and needing to load rapidly.

You may improve uniformity of bullet pull by running them through the Collet Die to straighten case mouth dents, but Lapua forming is already so uniform I wouldn't count on that to improve anything. You could weigh the cases. The last time I bought Lapua it sorted into two distinct narrow bell curves, indicating it had come off two sets of tooling. If you segregate it by tooling set, then any tiny average difference in neck diameter should be gone. Here's how mine sorted out. You can see two distinct clusters about 2 grains apart.

2-A reliable source has indicated that CFE223 is another good powder choice. Can someone rate the 3 powders in terms of fastest velocity to slowest velocity for a below max load?

I've not tried CFE 223. If your gun's barrel tends to foul easily and you won't get to clean it during the match, it may be an advantage. I've always had best accuracy with stick powders like Varget, but I've also owned a barrel that fouled with copper so fast it lost accuracy starting at about shot 40, so it couldn't finish a match that way without trouble. My first cure was moly-coating bullets for it, followed by firelapping it so this issue went away. If CFE additive had existed at the time, that might have helped, too.

3- Which powder would be more appropriate to use? I need to settle on one and develop with it due to the limited supply of Scenars.

Read up on Dan Newberry's OCW load development technique. I've had it work in as few as 27 rounds to zero in on a best load. If you have a scanner, the On Target Data System has a 15 day free trial. It will print special targets you shoot, then will find the hole centers for you and evaluate OCW round robins and Audette ladders for you. Doing that with both powders will tell you which has better potential for you. Like all variations on ladders, the OCW works best at 300 yards with no wind, but unlike an Audette ladder, you can often make it work pretty well at shorter ranges.

4-Given that I can load out to 2.950" what OAL or "base to ogive" length should I consider as a starting point?

You could start with the manufacturers standard COL for it in their data. Or you can try the method Berger uses for VLD load development. Just remember that when you start with a bullet jammed into the lands, it will raise pressure somewhere around 20% over a normal seating depth, so back it (the load) off about 10% from normal maximum for this test to compensate for that, then keep it constant during Berger's other depths in 0.030" increments.

5-Is there anything different that you would do?

Assuming your Lapua brass is standard primer and not the small primer Palma brass, I'd be using either Federal 210M or Tula KVB7 primers. The latter are much harder to seat, but produce very low SD. But the Federals are easy to seat well and come close to being as good.

6- Is anyone scratching their head and asking, "Why doesnt he just use the SMKs, those are big targets." ?

Not me. I suspect you want the higher BC for insurance and that the newer high BC Sierra Palma is unavailable. Supplies are still limited in some parts of the country, and that may be affecting your decision. All sorts of "stuff" happens.