Load development at 400 yards with a .338 Lapua Magnum

[MCMXI]

I've had an AI AWM for quite a few years but have never worked up a load for it, in part because I managed to get my hands on a few hundred rounds of Remington 250gr (Lapua Scenar) ammunition at no cost and have been shooting that with decent results out to 600 yards. That Remington ammunition sends a 250gr bullet downrange with a muzzle velocity of 2,950 fps and it's tough on AR550 steel at 100 yards, and still tough on AR500 steel at 400 yards. For this reason I decided to do load development at 400 yards since I like ringing steel as I shoot for groups. Some preliminary research a couple of years ago led to my purchasing 16lb of Hodgdon H1000 powder and Federal GM215M primers to drive the thousands of 250gr Lapua Scenar bullets that I'd obtained around the same time. This past weekend I had some spare time so figured I'd start to work up a load. After looking through my various reloading manuals and online, I didn't have much to go on. Berger's 250gr load data got me started. I put together five rounds using 90.0gr of H1000 powder, a Federal GM215M primer, new Lapua cases (neck sized) and 250gr Lapua Scenar bullet with a COAL of 3.625". Here's the first group ... and I would have been very pleased but the average velocity was only 2,751 fps (~ 50,632 psi according to QuickLOAD).



So I put together five more rounds with 93.0gr of H1000 and shot this group. You can see a couple of Barnes bullets copper hits from another day's session.



The average velocity was 2,875 fps (~ 59,280 psi according to QuickLOAD) which is better but still a little on the slow side. The 1.582" group was a real surprise so now I'm going to try 94.0gr which is still safe for pressure and see if I can push the bullet to 2,925 fps. All in all I'm really pleased since I've only tried two loads and ten rounds at this point. I have +0.5 mil of elevation dialed in so as not to hit the aiming dot which is a 2" circle. Also, all shooting was done prone off a bipod and with a rear bag.

 

[MCMXI]

I forgot to mention that I decided to do load development with the AAC TITAN-QD suppressor attached since that is how I shoot the rifle 99% of the time. Once I have "the" load I'll shoot unsuppressed to see how much of a POI shift I have at 400 yards.

 

[Dudedog]

Nice shooting, nice rig.
Been loading a lot of pistol lately and thinking 16lb is a lot of powder, but I forget how quick it goes in my 7mm rifle at 65gr a pop, and at 90+ for you even quicker

 

[MCMXI]

Dudedog, thanks. 94.0gr per round will get me about 75 rounds per pound so I'm good for 1,200 rounds. I will certainly need to buy more powder once it's available, along with more primers since I use the GM215M for other loads as well. The good thing is that I won't need to use a bunch of components working up the load. I'm going to try 94.0gr this weekend, and if I get the velocity and accuracy that I'm looking for I'll load up 93.5gr and 94.5gr to bracket the load ... and I'm done.

 

[taliv]

very cool. those are awesome guns and they shoot surprisingly well

 

[MCMXI]

taliv, thanks. I wanted to ask you about your load development for suppressed rifles. I've never worked up a load with a suppressor attached. Do you typically work up the load unsupppressed and then see how it shoots suppressed, or do you work up the load suppressed and see how it shoots unsuppressed? So far I've found that every rifle I own that shoots well will shoot even better with a suppressor attached. I'm just wondering if I'm doing this backwards. Your comment re the AIs is true. I have three and they're all 0.5 moa or better rifles with a variety of factory ammunition, and capable of even better accuracy with handloads.

In case anyone is wondering why the COAL of my handloads is 3.625" rather than the more standard SAAMI/CIP dimension of 3.682" common today, it's because the older AI AWMs and AI magazines won't accept the 3.682" COAL.

 

[taliv]

i never take the suppressor off. i don't really work up loads though. the main caliber i shoot 260AI goes through barrels in 2000 rounds so i just seat the bullet to AICS mag length and try to target a particular velocity (usually 3000 fps) and then when it starts falling off, i add a little more powder so i don't have to keep reprinting my dope cards.

iow, i don't do ladder tests or ocw or any of that. if i did, i would definitely use the suppressor because theoretically, you're tuning the load to the barrel harmonics, right? so the can would make a huge difference in that


humorously, i'll also add that inside a year, my suppressor will build up half a pound of carbon fouling. seems like that would also affect the ocw/ladder stuff. anyway, you might want to weigh your can if you're into that.

 

[MCMXI]

I've been thinking about ordering a 260AI barrel for my AI AW currently in .308 Win. Weighing the can? I hadn't thought of that. Hmmm ... I like data, and with only a few rounds through the can this would be the time to do it. I'm amazed that your can holds on to so much carbon, then again, I have no point of reference.

 

[taliv]

check your pm in a few min

 

[Nature Boy]

Please quit posting pictures of that sweet rig, you're making me want one!

 

[MCMXI]

HA! HA! I just changed my desktop at work to that photo and I have two screens so it's double the trouble. I really need to order some of those TAB suppressor covers. The mirage is starting to become a problem.

taliv, thanks for the PM ... and the education!

 

[MCMXI]

It was a warm weekend in MT but despite the mirage off the ground and the suppressor I tried 94.0gr (2,888 fps), 95.0gr (2,943 fps), 95.5gr (2,916 fps) and 96.0gr (2,973 fps) at 410 yards this weekend with ok results. According to QuickLOAD and the two models that I ran, the 95.0gr, 95.5gr and 96.0gr loads were slightly over pressure but QL lists the MAP at 60,916 psi whereas SAAMI shows 65,000 psi. That's confusing!! The primers did look slightly cratered and more flattened (slight radius left on outside edge) than previous loads but extraction was ok. The problem I now face is that given the COAL, powder and primer combination, I can't get to 2,950 fps with good accuracy and safe pressures unless SAAMI max pressure of 65,000 psi is correct. Using QuickLOAD and nodal analysis (using barrel time), the accuracy load is supposed to be between 92.2gr and 92.6gr with a velocity around 2,865 fps. So far the best group has been with 93.0gr (@ 2,875 fps) so I have some faith in the nodal analysis model. Here's a link to the SAAMI pressure specs.

http://www.saami.org/specifications_and_information/specifications/Velocity_Pressure_CfR.pdf


Here's the 94.0gr load ... and yes, I missed the target twice so the group shown is not correct. Best case scenario is that I put two shots just outside the steel since it was windy.




I decided to shoot 8 rounds of the 95.0gr load and discounted the round on the left simply to get a better idea of the capability of the load rather than my inability to adjust for a sudden gust of wind.




Finally, I shot a group with the 96.0gr load and it's getting hard to tell new hits from old hits but this is the worst case group. Not bad but not great and possibly over pressure if QuickLOAD is correct.

 

[bush3755]

I don't think 3 shot groups are significant enough to represent the accuracy one can count on all the time. 10 shot ones are better. I shoot 20 rounds in a group testing for accuracy; they're all much larger than any single 3 or 4 shot string in the series.

Benchrest 5 shot single group records are under .010" at 100 yards. One hundred is the best range to asses best accuracy as groups' MOA values increase with range due to external ballistic variables and atmospheric conditions. Aggregates of several 10 shot groups at 100 yards have their average around .200" with the largest single groups over .300" If that doesn't tell people that tiny few shot groups are 99% luck, well........ And those records are the best accuracy attained. All those thousands of other groups are larger - much, much larger in some instances.

If that rifle shoots about 1/2 MOA at 400 yards with several loads, good for you.

 

[ironworkerwill]

Very nice, all the way around. Lots to love about AI!

 

[MCMXI]

ironworkerwill, thanks ...

I don't think 3 shot groups are significant enough to represent the accuracy one can count on all the time. 10 shot ones are better. I shoot 20 rounds in a group testing for accuracy; they're all much larger than any single 3 or 4 shot string in the series.

I've shot quite a lot of F-Class matches so 15 to 20 shot groups are not unusual for me and I agree that the more shots in the group the better. However, for load development I find that 5 shot groups work well. You can see the problem that I'd have with all of these loads at 100 yards. It would be hard to tell the difference between any of them since they would most likely all make one hole. There are certainly atmospheric variables in play and I'm dealing with mirage, wind, varying air temperature etc. but that makes the results all the more interesting and this AI AWM seems to be a very forgiving rifle with decent groups from 90.0gr to 96.0gr.

 

[bush3755]

To me, a one hole group means the extreme spread is no larger than bullet diameter.

Most cartridges shoot very accurate across a 5% spread in specific charge weights. One may need to shoot 25 or more shots to tell the difference. Zeros may be different for each one used. At ranges through 300 yards, a 3/10ths grain spread in a given charge weight is good enough for sub 1/2 MOA accuracy using the right stick powder.

 

[Rule3]

I just have to look at this in awe! Pretty impressive shooting and scenery. We just do not see that around here.

Reminds me of a show on Discovery or somewhere about Army Sniper school. Didn't know that SEALS actually had to go and pass that school!

 

[MCMXI]

Rule3, thanks. It is beautiful up here in MT with one of the best climates (for me) anywhere in the US. I'm lucky to be able to shoot out to 1,300 yards outside my back door and never take that for granted. Here's some more scenery for you to enjoy. My targets are way to the right of this view.

 

[Rule3]

 

[ironworkerwill]

I'd surely go broke there! It'd be too easy to shoot too much, if that's even possible.

 

[Nature Boy]

Agreed. I'd need an ammo factory and a barrel fabricating shop.