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Old February 21, 2021, 02:45 PM   #1
Mitchja95
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Workup lapua mega for m38 Swede

Help.
Gentlemen: I need some experienced counsel. I have been reloading for almost 20 years. I reload for 8 rifles ranging from the .243 Win to the .338 WinMag. But this is my first milsurp.
I’m trying to work up a load for a hog hunt coming in a few weeks.
Rifle: 1916 Carl Gustav M38 6.5x55
Bullet: 155gr Lapua Mega
Case: PPU, Once-fired, partial full-length resize.
Powder: RL 22
During this period of limited powder and bullet options. I chose a recipe from Vihtavouri that called for 42.3- 49grs of N165 with Velocities between 2223-2478 fps. Can’t get N165. So the best info I could find said RL22 was a good substitute.
Searching for my rifle lands I Stretched the COAL out to 3.05”. Stopped before I found them.My First ladder test started at 47.5 gr. My velocities were 2,650 to 2675!! My primers are not flattening at all. But they are cratering.


I stopped and loaded a new string starting at 45grs and velocities dropped to 2550-2575. But the primer still cratered. I Stopped and started another string at 42.5grs. My velocities dropped to 2435-2460. My accuracy was excellent but there was still minor cratering. I thought I would try again.
I loaded a string starting at 40grs. Because I was using cases that I had pulled bullets from, I used what I thought was a medium crimp from a Lee Factory die. My Velocities shot back up to 2724, 2726 and 2699 with barely perceptible cratering. But what was going on with the velocities? I turned off my chrono and restarted, thinking maybe it was having a spell (yes, it has acted up before)
I shot my next group at 40.5grs. Velocities were 2574,2549 and 2496.
I like the load of 42.5grs at 2450 fps. Should I be concerned about the minor cratering, knowing it’s an old bolt and firing pin with unmatched numbers. Should I be concerned about this action launching a 155 grain bullet at 2450fps?
Would seating my bullet to the recommended 2.874 COAL help or hurt?
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Old February 21, 2021, 07:02 PM   #2
ligonierbill
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Based on my experience with 160 gr Hornady and Woodleigh, you should be OK. I am running them at 2,600 using Re-22. You were probably too hot with the initial load though. Regarding COL, 3.05 seems long with those blunt Megas, but if they fit, they fit. My rifle is a strong rebarreled Mauser 98.

Last edited by ligonierbill; February 21, 2021 at 08:32 PM.
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Old February 21, 2021, 07:45 PM   #3
Shadow9mm
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according to my older lee manual manual for the 6.5x55 with a 160g jacketed bullet and reloader 22 at a COL of 2.957. This manual is about 13yrs old, and the loads tend to be a touch on the hot side these days so use caution.
start 43.2g at 2348fps
max 47.0g at 2535fps

As far as the minor cratering, look at your firing pin hole with a magnifying glass. I had a new rifle with a similar issue, it cratered every round it fired factory and starting hand loads. Turned out they had chamfered the firing pin hole. Also on a old military surplus gun you may have more tolerance between the firing pin and firing pin hole. If your primers are not flattening and flowing, I would ignore the cratering.
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Old February 22, 2021, 01:33 AM   #4
Mitchja95
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Thank you, gentlemen. I can’t tell you how much I appreciate your time.
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Old February 22, 2021, 11:55 AM   #5
Unclenick
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Do you have a sense of how close to the lands you are? When you reach the lands, peak pressure is usually in the 10-20% higher range than you will have with normal seating.

If you don't have a comparator for measuring, just push a bullet into the throat with the eraser end of a pencil and put a cleaning rod in through the muzzle to touch the bullet nose. Mark the rod level with the muzzle using a pencil when it touches the bullet nose. Then knock the bullet out and close the breech and let the cleaning rod touch the bolt face and mark it with a pencil again. The distance between the two marks is the maximum COL you can get to without jamming the lands firmly with the bullet. If you are 0.030" shorter than that, then proximity to the throat should not be affecting pressure much.
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Old February 22, 2021, 08:18 PM   #6
Mitchja95
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Excellent hack, unclenick. Thank you. As soon as I got home today I saw you’re post and ran downstairs and tried it. I used masking tape to mark for each reference. Not a micro reading but it confirmed that I’m easily .06” off the lands. Maybe someday after my upcoming hunt I’ll work with seating a little. I know how I can perfect the technique in the future and will work that into my routine. Thank you.
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Old February 23, 2021, 04:26 PM   #7
lonniemike
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If 2450fps works for you, use it. Your M38 has a ?22-23" long? tube? But from a M96's 29" long tube, a touch on the hot side could/would be "old factory Norma 156 loaded to 2645fps". Both Oehler and Labradar reads are within 5-10 fps of the ammo boxes spec. Turn the chrono on and use it. Be safe, Work up, Bullet seating changes can change pressure and speed, Experiment with crimp, Look for best accuracy. BestoLuck
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