.338 Lapua - AI AXMC - Ammo Question - 250 or 300grain?

[Monk Medic]

Background:
So I have about 350 rounds on my AI AXMC rifle, have been larger shooting the Lapua brand .338 in 300 grain, did run some 250 during break in, but didn’t document. I tend to bit of a data junkie, so I usually compile a data book on each rifle, and check MV over time.
At this point, my data books are based on the 300 grain round.

I was running low on the expensive Lapua 300 gr stuff, and had a box of Federal Match 250grain rounds sitting around that had been given to me.
So on my last range trip I shot those, along with some of the 300. Shooting to about 700 yards out.

Observations:
The 250 grain shot flatter, no surprise there, higher muzzle velocity for the lighter round.
What did surprise me was that the 250 gr around seemed to group might tighter at distance than the 300 that I had been shooting.
Switched back to the 300, and yes, that seemed true.
I had no more 250s to shoot, have ordered some so I can do a true A/B test to verify this, but in the meantime wanted to ask a few questions.

Questions:
1) Does my gun just like the 250s better, is that why the accuracy seemed improved?
2) Is the 250 the round of choice in 1,000 yards and in?
3) Anyone else notice this, curious what others shooting .338 on a regular basis have found.
4) Any downside to using the 250s for say, 1,000 yards and in, in terms of barrel life?
5) Do my observations make sense, or is that just an aberration?

Thanks much,
Monk

 

[TripleBull]

We put about 600 rounds of factory Lapua ammo down the tube of our Masterpiece Arms 338LM. We shot about 400 of the 250 grain Scenars and 200 of the 300s. Most of our shooting was 1k yards and beyond. We're at an elevation of 5000' ASL and the 250's go transonic around a mile whereas the 300's get out a little farther. I can feel the recoil difference between the 250s and 300s but can't say that I could see a difference in accuracy or precision and I tend to take quite a bit of data like MV on every shot and summarize on-target performance. We mostly shoot paper and only occasionally steel. I don't think it's trivial to compare days of shooting at ELR when the conditions vary as widely as they do here.

For your second question, we saw good performance from the 250's at a mile. On a day with highly variable wind up to 25 knots, 5 shot groups ran from 3+MOA down to a little over 1MOA. Others here have had good things to say about the 250 Scenars down into the subsonic range.

A couple of months ago, we bought an AX/MC in 338LM. So far, we have only shot 300 grain Scenar factory ammo through it. We've been breaking the barrel in at 1K yards for the most part. So far it has not matched the best performance we got from the Masterpiece Arms, but every time out with it, we've had truly heinous wind, so I'll wait to compare like with like. For certain, I like the shooting dynamics better with the AI. The reticle stays on target better and the gun feels far more stable during the trigger squeeze.

I'm looking to move to other projectiles soon on the AI. I've got a couple of boxes of the Berger 300s and will probably pick up a few hundred of the Flatlines. It will be interesting to see how the higher muzzle velocity of the Flatlines works with their high ballistic coefficient. Fun times ahead.

 

[diverdon]

If I remember correctly a few years ago Lowlight said that the sweet spot for the .338L was with 285gr and under. There just was not enough ass to get the 300gr's where they needed to be to see the advantage of the BC. He went on to say that the 300gr's shined best with the .338 Norma.

 

[Monk Medic]

Hi Don,
I think that is excellent advice, if it came from Frank, double so.
Thank you!

 

[Monk Medic]

We put about 600 rounds of factory Lapua ammo down the tube of our Masterpiece Arms 338LM. We shot about 400 of the 250 grain Scenars and 200 of the 300s. Most of our shooting was 1k yards and beyond. We're at an elevation of 5000' ASL and the 250's go transonic around a mile whereas the 300's get out a little farther. I can feel the recoil difference between the 250s and 300s but can't say that I could see a difference in accuracy or precision and I tend to take quite a bit of data like MV on every shot and summarize on-target performance. We mostly shoot paper and only occasionally steel. I don't think it's trivial to compare days of shooting at ELR when the conditions vary as widely as they do here.

For your second question, we saw good performance from the 250's at a mile. On a day with highly variable wind up to 25 knots, 5 shot groups ran from 3+MOA down to a little over 1MOA. Others here have had good things to say about the 250 Scenars down into the subsonic range.

A couple of months ago, we bought an AX/MC in 338LM. So far, we have only shot 300 grain Scenar factory ammo through it. We've been breaking the barrel in at 1K yards for the most part. So far it has not matched the best performance we got from the Masterpiece Arms, but every time out with it, we've had truly heinous wind, so I'll wait to compare like with like. For certain, I like the shooting dynamics better with the AI. The reticle stays on target better and the gun feels far more stable during the trigger squeeze.

I'm looking to move to other projectiles soon on the AI. I've got a couple of boxes of the Berger 300s and will probably pick up a few hundred of the Flatlines. It will be interesting to see how the higher muzzle velocity of the Flatlines works with their high ballistic coefficient. Fun times ahead.

Excellent information sir, I’ll be quite interested in what you discover with the AL and the 300.
Any thoughts on running the 250 with the AI? I’d very interested in that. If my round is staying supersonic up to a mile, then I think I am all set with what I need to switch ammo over to. I’ll spend some time this week or weekend doing just that, and gathering data.
I’ve been shooting the Lapua Scenars as well, any thoughts on the Federal Gold Metal Match? I’ve been using those in my other bolt guns, very happy so far.

 

[surgeon260]

If I remember correctly a few years ago Lowlight said that the sweet spot for the .338L was with 285gr and under. There just was not enough ass to get the 300gr's where they needed to be to see the advantage of the BC. He went on to say that the 300gr's shined best with the .338 Norma.

I didn't see the original post from Lowlight, but I don't understand this statement. My experience has been that the Lapua is faster than the Norma, even when loaded to identical COAL which puts a 300 way far down in the Lapua case. With a long throat, the Lapua will have an even greater speed advantage. So how is it that the Lapua can't push the 300s fast enough but the Norma can?

 

[TripleBull]

Excellent information sir, I’ll be quite interested in what you discover with the AL and the 300.
Any thoughts on running the 250 with the AI? I’d very interested in that. If my round is staying supersonic up to a mile, then I think I am all set with what I need to switch ammo over to. I’ll spend some time this week or weekend doing just that, and gathering data.
I’ve been shooting the Lapua Scenars as well, any thoughts on the Federal Gold Metal Match? I’ve been using those in my other bolt guns, very happy so far.

I've never shot Federal GGM in 338. I've liked them in 308 but it could be gun/barrel specific for your AX/MC. Worth a try. Handloading any good projectile is probably a significant step up over factory. The ammo I handloaded for our MPA was an eye-opener. Excellent SD and ES compared to factory, and smaller groups.

 

[mercracing]

I have a case of Prime to try in my MC once my suppressor is out of jail. I’ll keep you posted with what I find.

 

[Laseredge]

I didn't see the original post from Lowlight, but I don't understand this statement. My experience has been that the Lapua is faster than the Norma, even when loaded to identical COAL which puts a 300 way far down in the Lapua case. With a long throat, the Lapua will have an even greater speed advantage. So how is it that the Lapua can't push the 300s fast enough but the Norma can?

Frank’s logic and experience is that the .338LM shooting 300 class bullets really helped by being @2800fps+ at the muzzle to maximize potential at extended range (2000+ yds.) The 285’s are just a bit easier to load to that velocity than 300’s, especially out of a factory 27” barrel. This is something that they were seeing at the Gunsite LR courses.

 

[surgeon260]

Frank’s logic and experience is that the .338LM shooting 300 class bullets really helped by being @2800fps+ at the muzzle to maximize potential at extended range (2000+ yds.) The 285’s are just a bit easier to load to that velocity than 300’s, especially out of a factory 27” barrel. This is something that they were seeing at the Gunsite LR courses.

Fair enough, but I still don't understand the statement that the 338 Norma is better suited to the 300s than the 338 Lapua. The Lapua will push them faster in pretty much every conceivable scenario.

 

[Monk Medic]

Frank’s logic and experience is that the .338LM shooting 300 class bullets really helped by being @2800fps+ at the muzzle to maximize potential at extended range (2000+ yds.) The 285’s are just a bit easier to load to that velocity than 300’s, especially out of a factory 27” barrel. This is something that they were seeing at the Gunsite LR courses.

Appreciate that. Thanks for the reply!

Most of the commercial Lapua ammo seems to be either 250 or 300.

On my 27” AI AXMC using the Lapua Scenars :
- 300 is 2774 fps at the muzzle
- 250 is 3024 fps

Thoughts?

So I understand, are you saying 285 grain rounds are Frank’s suggestion?

Is that statement or discussion of Frank’s posted somewhere on the forum, or where can I read his original words?

 

[surgeon260]

285s have a longer bearing surface than Berger 300s. In my experience you can't push them any faster despite the lighter weight.

 

[HillBilly n TX]

I believe this is the thread you’re looking for. https://www.snipershide.com/shooting/threads/what-cartridge-for-a-one-mile-shoot.6870573/

 

[Monk Medic]

I believe this is the thread you’re looking for. https://www.snipershide.com/shooting/threads/what-cartridge-for-a-one-mile-shoot.6870573/

Perfect, thanks HillBilly, I printed and saved that as reference!

 

[Monk Medic]

Made the decision to switch over to the Lapua 250 grain projectiles today.
Been going back and forth all week, shooting and trying both, and I say for what I am going to use the rifle for, 1 mile and under, the 250s take the cake.
Flatter shooting round, higher MV, and as referenced earlier Frank (Lowlight) testimonial seems to tie the ribbons on it.

So I did the final switchover this afternoon.
Took the .338 Lapua AI AXMC out to the range, redid my zero for 250 grain rounds, obtained Magnetospeed chronograph readings.
Updated my datebook, and reconfirmed zero before I left.
Very happy and comfortable with this decision.
Updated the Applied Ballistic software and app, then the Kestrel and the SIG Rangefinder.
Nice thing is that if I want to switch back, I still have all my 300 grain projectile data, just need to put the cards back into the book.

Super happy how well the gun shoots with this ammo, season is drawing to an end here in Maine.
I've got just one 1,000 yard shooting before the snow flies.