338 Lapua Magnum Load Data Questions for TRG 42

[tantoco]

I'm new to loading for long range shooting and appreciate everyone's guidance. I'm building up a load for a TRG 42 using a slightly modified Optimal Charge Weight method (http://optimalchargeweight.embarqspace.com/). I'll provide all the data I gathered, my question, based on the data what is my Optimal Charge Weight? Looking at the results my guess is 92.2gr but I don't have enough experience (or good data) to be certain.

Here's the components for my load:
- .338" 300gr Sierra Matchking HPBT Projectile
- 1.72" Projectile Length
- Hodgdon Retumbo Powder
- Winchester Large Rifle Magnum Primer
- Lapua Brass

I got a max charge from Hodgdon's Website of 94gr and backed off 10%, then worked up 14 different charges to test. I realize now that was probably wastefull and overkill. Something else to note, no high pressure signs at 94.2gr and that group was pretty tight and close to POA based on sight being half an inch low right, does that mean I should run additional tests beyond the max charge weight?

I used a C.O.L. of 3.717 by measuring the C.O.L. that touches the lands then backed off .02.

Another lesson learned was not to use Shoot-N-C targets, made it difficult replicate sight picture.

Another challenge was I didn't make enough rounds to sight-in the new scope (HDMR on Spuhr one peice base and rings) so when I began the test I think I was low right half an inch.

Other data:
- Chrono. setup 10 ft. from end of barrel
- 27.125" barrel length
- 10" right hand rate of twist
- 100 yard zero and range
- 2" sight height
- 1423 ft. altitude
- 30 barometric pressure
- 80 temperature
- 18.7% relative humidity
- Avg. 2 mph wind from 10 o'clock.

Here's the results of the groups, where I have 2 shots very close then one further out I'm not sure if those are fliers due to me or a non-optimal charge weight. The chrono. gave me Extreme Spread (ES) and Standard Deviation (SD), not really sure what I should be learning from these two values. All were 3 shot groups.

- Group 1: 85gr, 2544 high, 2493 low, 2509 avg, 52 ES, 30 SD, .3 group size, 1.303 11 o'clock from POA.

- Group 2: 86.7gr, 2559 high, 2534 low, 2546 avg, 25 ES, 17 SD, .439 group size, .879 11 o'clock from POA.

- Group 3: 88.4gr, 2635 high, 2629 low, 2631 avg, 6 ES, 3 SD, 2 shots were dups at 2629, .232 group size, .317 12 o'clock from POA.

- Group 4: 89.1gr, 2682 high, 2661 low, 2675 avg, 21 ES, 9 SD, .747 group size, 1.008 12 o'clock from POA.

- Group 5: 89.3gr, 2645 high, 2609 low, 2631 avg, 36 ES, 19 SD, .071 group size, .364 10 o'clock from POA excluding possible flier, 1.353 group size, .530 11 o'clock from POA including possible flier.

- Group 6: 89.7gr, 2672 high, 2650 low, 2661 avg, 22 ES, 11 SD, 1.129 group size, .520 12 o'clock from POA.

- Group 7: 90.3gr, 2672 high, 2629 low, 2655 avg, 43 ES, 23 SD, 1.071 group size, .924 12 o'clock from POA.

- Group 8: 90.9gr, 2726 high, 2672 low, 2695 avg, 54 ES, 27 SD, .394 group size, .445 12 o'clock from POA.

- Group 9: 91.6gr, 2743 high, 2704 low, 2723 avg, 39 ES, 27 SD, only 2 shots, data on one shot missed due to battery going dead, .11 group size, .164 4 o'clock from POA excluding possible flier, .805 group size, .534 5 o'clock from POA including possible flier.

- Group 10: 91.9gr, 2754 high, 2704 low, 2726 avg, 50 ES, 25 SD, cleaned barrel after this group, .164 group size, .598 4 o'clock from POA excluding possible flier, .8 group size, .329 5 o'clock from POA including possible flier.

- Group 11: 92.2gr, 2754 high, 2726 low, 2743 avg, 28 ES, 14 SD, .149 group size, .114 3 o'clock from POA.

- Group 12: 92.9gr, 2812 high, 2760 low, 2779 avg, 52 ES, 28 SD, .331 group size, .217 7 o'clock from POA.

- Group 13: 93.5gr, 2801 high, 2772 low, 2789 avg, 29 ES, 15 SD, 1.103 group size, .335 4 o'clock from POA.

- Group 14: 94.2gr, 2836 high, 2783 low, 2802 avg, 53 ES, 29 SD, .227 group size, .228 6 o'clock from POA.

Thanks for any guidance you all can offer.

 

[Gunfighting Inc]

Re: 338 Lapua Magnum Load Data Questions for TRG 42

I use 94.2 grains of Retumbo with my 285 grain bullets and get great results. Your velocity and group size are good. Now take it out to some significant distance and see how you like it.

 

[tantoco]

Re: 338 Lapua Magnum Load Data Questions for TRG 42

Thanks for the feedback. It's hard to read the 2nd and 3rd targets. The group order, starting with #6 where the 1st target left off, goes bottom left, bottom right, center, top left, and top right (e.g. target 2: #6 bottom left, #7 bottom right, #8 center, etc.). Per the Optimal Charge Weight (OCW) method I'm supposed to look for three groups that are pretty tight and close to POA, to me that looks like 91.6gr, 92.2gr, and 92.9gr. Based on that I think my OCW is 92.2gr. Once I figure out the load to go with you bet I'll be pushing some distance! Thanks again and happy holidays.

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Reinman</div><div class="ubbcode-body">I use 94.2 grains of Retumbo with my 285 grain bullets and get great results. Your velocity and group size are good. Now take it out to some significant distance and see how you like it. </div></div>

 

[.50 Cal Cow]

Re: 338 Lapua Magnum Load Data Questions for TRG 42

As you read, OCW also states to look for the scatter node and your optimal should be one or two groups above that depending on your increments. And judging from your picture it looks like your group at 93.5 appears to be a scatter node so 94.2 or around as well may be your sweet spot.

 

[Lt. Arclight]

Re: 338 Lapua Magnum Load Data Questions for TRG 42

I load and shoot alot of 338LM. Over 6K rounds since mid 2005. I've wasted alot of powder and barrel life trying to get the "optimum" load. I give you credit for your attention to detail.

I personally would not try to develop a long range load at NOTHING less than 300 yards. IMO, you are better off selecting a max load without pressure signs and getting time behind the gun.3 shot groups are meaningless IMO. Buy a box of factory Lapua ammo get zeroed at 300yards and you should easily be able to hold at least moa. Until then-how do you know those 3 shoot groups aren't shooter induced?

You say you are new to the long range loading game-are you also new to the long range SHOOTING game? For the longest time I loaded 87grains of RL25 300SMK fed215M and Lapua brass and started reading the wind.

With such a large case capacity, temp variation and overall case volume difference-even within the same lot of Lapua brass, I've found that changes less than 0.5grains changed little in overall performance. We are talking about less than 0.5% of the overall load.

There isn't a perfect load. And there isn't a perfect shooter. But trigger time is far more important than scale and press time.

Your COAL is long enough for sure.Retumbo is a good powder with excellent temp performance. You are in the ballpark. I always load to magazine length for my AIAW which is 3.600 and shoot a 25"Bartlein barrel chambered by GAP with a 1/9.3 twist.

Don't drive your self crazy.I wrecked a barrel on a new McMillan Tac338 and lost alot of sleep trying to get it to shoot.Long story short and new Schneider barrel chambered by GAP made the stick shoot like a laser.From then on I stuck with one load and spent time learning my fundamentals. Check out some of the instructional video's done by Lowlight. You would be amazed at how many little errors add up at long range.

Load up 40 or so rounds and let that TRG stretch its legs. Really. Plenty of guys win comps with Black Hills or other factory ammo.338LM is not a 100 yard record holder and good results at 100yards don't necessarily mean 1000 yard stellar results.

I've also had better results with MORE than a 1/10" twist shooting the 300SMK.The 250SMK,250 Lapua Scenar and 250 lockbase do great at even beyond 1000yards. Just my 2 cents. Best of luck.

 

[l115a3]

Re: 338 Lapua Magnum Load Data Questions for TRG 42

Woow look you found the best node for your rifle.


I had pull down one Factory Ammunition to weight their charge,

Black Hills .338 Lapua Magnum 300 SMK
Powder weight = 101.4 gr.

 

[tantoco]

Re: 338 Lapua Magnum Load Data Questions for TRG 42

Thank you all for the experience and insight. Surprising to know that the Black Hills has 101.4gr, also thanks for the scatter node note. This is he first time I shot this TRG and was hoping to finalize the load, looks like I will do one more test starting with 94.2gr working up to one iteration past 101.4gr. or until signs of pressure, then put the load development behind me and start focusing on shooting.

 

[Lt. Arclight]

Re: 338 Lapua Magnum Load Data Questions for TRG 42

My guess is Black Hills in using US869 a ball powder,it meters easily-NOT RETUMBO.101.4grains of Retumbo would be a DISASTER.

 

[tantoco]

Re: 338 Lapua Magnum Load Data Questions for TRG 42

Thanks Arclight, I didn't think of that. I loaded them last night and the cases were so full I could hear the bullets compressing the powder when I was seating them, I didn't know what to make of it. Does anyone have any feedback on what they think my maximum charge should be? Thanks again.

 

[Lt. Arclight]

Re: 338 Lapua Magnum Load Data Questions for TRG 42

90 grains of Retumbo behind a 300SMK has ALWAYS worked for me in An AR30 both with the factory barrel as well as a 1/9 Schneider 30",Also in a McMillian TAC338 with a 29" 1/9 Schneider. And finally in my AI AW with the 27" factory barrel and a 25" Bartlein 1/9.5. (All barrel work done by GA Precision).

Load to magazine length and go shoot. Check other posts in this forum-there is no "magic" to get a 338LM to shoot with 300SMK's.Sometimes conditions such as HOT temps will make an acceptable load show pressure signs. The MAX load isn't always the most accurate. And unless you are going well beyond 1500 yards,why push it so hard? Barrel life is very good, no reason to burn the throat out trying to find that special load.

87gr. of RL25 is another good load. You are over thinking this.The 338LM is NOT a benchrest cartridge. You have a proven gun-many have had very good results with the TRG42. IMHO, you are just chasing your tail. Load up and go to the range. Really.If you can't hold sub moa at 300yards all the powder and bullets in the world aren't going to help at 1000yds.

PS: you are VERY LUCKY not to have touched off 100 or so grains of compressed Retumbo.

 

[tantoco]

Re: 338 Lapua Magnum Load Data Questions for TRG 42

Arclight, you saved my butt! Don't have anyone here to shoot with, I'm flying solo, without you all's experience I'd be learning "the hard way." I'm going to pull those big boys and reload them to 92.2gr based on the test above and call it a day with load development. Thanks again!