I had a once in a lifetime opportunity to get an MWIR ELR clip-on or buy a new truck. Trucks are always available, so I chose differently.
Edit: I don't want to derail this AI pic thread any further so this is the last I'll say about it: it's almost more useful as an ELR spotter.
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Sorry to take the topic back to barrel twists.
Had some free time at work so decided to make a table for the bullet stability for ELD-M, SMK and TMK bullets.
Good news is that even at low speeds (2400fps like you might see in a short barrel) most projectiles are at least somewhat stable, but do definitely need to choose wisely if you want a fully stabilized projectile in a 1:12 twist barrel.
I then took the worst bullet I'd looked at (175gr TMK) and compared to a 1:10 and 1:11 twist.
Basically at any realistic velocity you are fine with a 1:11 twist or faster, obviously the heavier projectiles (180gr+) start becoming and issue but I had to stop somewhere. Maybe if I'm bored at work again I'll add more projectiles and twists.
TLDR is, don't buy a 1:12 twist barrel if you can help it.
Had some free time at work so decided to make a table for the bullet stability for ELD-M, SMK and TMK bullets.
Good news is that even at low speeds (2400fps like you might see in a short barrel) most projectiles are at least somewhat stable, but do definitely need to choose wisely if you want a fully stabilized projectile in a 1:12 twist barrel.
I then took the worst bullet I'd looked at (175gr TMK) and compared to a 1:10 and 1:11 twist.
Basically at any realistic velocity you are fine with a 1:11 twist or faster, obviously the heavier projectiles (180gr+) start becoming and issue but I had to stop somewhere. Maybe if I'm bored at work again I'll add more projectiles and twists.
TLDR is, don't buy a 1:12 twist barrel if you can help it.
Attachments
Also, while I still can't fully contribute to the picture thread, I'm getting very close now.
Again, it isn't just about the bullet weight, but the bullet length as well that matters.
Plenty of folks ran the M40, M40A1, M40A3 and M40A5 out past 1000 yards just fine, which has a 1:12 twist barrel, and ran M118LR rounds, essentially Federal GMM SMK 175gr. I did reach out to a sniper instructor peer who has combat experience with the M40 rifles, who confirmed the distance and capability for me.
We also have @FUNCTIONAL with very direct experience running the M40. Sorry to call you out but it's important. Hell I want to share more of that shot data just as a solid reference...
There's no reason why the 1:12 Lothar Walther barrels aren't extremely capable. But, the right round needs to be chosen for it.
And so this circles right back to why I made my original post sharing the shot group: the Sierra 168gr TMK round with it's improved 9° boat tail seems to work best in this barrel, which I've so far tested in 20", and I have no doubt will perform equally well in my 24". My next range day I hope to get 300 round shot groups, and later, 700 round shot groups depending on wind.
I'll share all the images and data I have on this round. For us Yankees, the Federal GMM SMK 168gr & 175gr, and the Federal LE T308T 168gr, seem to be the most effective and cost conscious round to use in these barrels.
I don't have experience with Lapua or Berger rounds in these calibers, so I leave it to others to comment on what else shoots well. I invite it as this data is important for folks like us to have.
And yes, I read every single post in this forum regarding the Arctic Warfare and AT308 looking for ballistic data of factory rounds, and found excruciatingly little.
I hope the attached data helps for context. And I have much more data that shows how the length of Hornady rounds do not stabilize. I also tried the stability factor with a Berger 185gr round without success, but I'd entertain actually shooting it to see how it performs.
I don't understand how @hafejd30 is shooting 178gr ELD-X rounds. As far as I'm concerned, he's committing voodoo witchcraft as everything I have says that round should shoot like shit in a 1:12 barrel. But he's doing something right with his hand loads.
Shot data simulates shooting in early March at Cameo Shooting Complex in Palisades, CO. USA
And my groupings again with the T308T 168gr TMK for good measure so everything is in one place:
I really only have that barrel should I want to throw a clip-on on there for coyotes. I might pop the 6.5 Creedmoor off here in a few hundred rounds and shoot the 6 for a while, we shall see.
I just confirmed 100% it’s a 1:12. Has shot many groups under 1/2 moa. Always a hammer and always holds zero. Going on year 5 with my baby
I have a 18” 1:10 Bartlein ready to thread on when this one decides to go. But lots of life in it yet
Just breaking spring in the UP of Michigan so starting to sling lead more again
Gave me a chance to move the gun room over the winter. Loving the new setup
No worries @HKSniper11B I'm a big proponent of try it and see how it goes. Many hate the 175 RDF. When they saw my success with it a few guys tried and couldn't get it to shoot...I probably inherited 1k 175RDFs from people who just gave them to me after giving up. Likewise I have horrible luck with ELDM bullets.
Either way... going to do some experimenting after my 22lr match Saturday. Found 11 rounds of fgmm with 185 gr burgers. Going to sling them through my A5 with 1:12t and see what happens. If I have 175 or 168 fgmm I'll do a direct comparison.
Edit. For reference it shoots good out of a 11.25t barrel. The middle group I'll chalk up to me screwing up.
Either way... going to do some experimenting after my 22lr match Saturday. Found 11 rounds of fgmm with 185 gr burgers. Going to sling them through my A5 with 1:12t and see what happens. If I have 175 or 168 fgmm I'll do a direct comparison.
Edit. For reference it shoots good out of a 11.25t barrel. The middle group I'll chalk up to me screwing up.
My AT shot Hornady factory 175s 4in at 100yd.... I've never had ANY factory Hornady shoot well in my rifles. I did have one .6MOA 10-shot group at 600 with my 175SMK handloads so I seem to echo your experience.
Hadn't noticed that the 50bmg mag was actually "two pieces" joined together before (see the six rivet-looking spots where the inside and outside pieces are joined, making it double-layered at the front.
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"You vs the guy she tells you not to worry about"
My barrel is a 1:12 LW AT. Started life at 26” and I was getting 2800 even from M118LR 175gr SMK.
I recently chopped it to 20” and spent a weekend plinking to 1 mile.
We put 200 rounds of 168gr Fed GMM and another 150 rounds of M118LR through it.
Both shot the same poi at 100m and there was only 20fps between the loads at the muzzle 2600 and 2580 respectively. Both shot extremely well at 100m with very small groups around 3/4” or better.
However as we started to increase the range the 175gr bullet started to shine in both wind deflection and ability to make impacts past 1000m. This shouldn’t come as a surprise to those of you who understand BC and the fundamentals of LR shooting.
The 168gr became very challenging at 900m and out. We struggled to get consistent impacts at 1000m and couldn’t land a single shot at 1100m.
The 175gr however was making impacts at 1200m with some regularity and was a breeze at 1100m. We also had a stab at the 1640m target and recorded 1 hit which I put down to pure luck as conditions were challenging at best (long grass and 5-15mph full value winds that regularly switch direction).
Next step is to load some lapua harass with 176 Atip match and see if we can compete with the 6.5 crowd at the next PRS match.
TPH
I recently chopped it to 20” and spent a weekend plinking to 1 mile.
We put 200 rounds of 168gr Fed GMM and another 150 rounds of M118LR through it.
Both shot the same poi at 100m and there was only 20fps between the loads at the muzzle 2600 and 2580 respectively. Both shot extremely well at 100m with very small groups around 3/4” or better.
However as we started to increase the range the 175gr bullet started to shine in both wind deflection and ability to make impacts past 1000m. This shouldn’t come as a surprise to those of you who understand BC and the fundamentals of LR shooting.
The 168gr became very challenging at 900m and out. We struggled to get consistent impacts at 1000m and couldn’t land a single shot at 1100m.
The 175gr however was making impacts at 1200m with some regularity and was a breeze at 1100m. We also had a stab at the 1640m target and recorded 1 hit which I put down to pure luck as conditions were challenging at best (long grass and 5-15mph full value winds that regularly switch direction).
Next step is to load some lapua harass with 176 Atip match and see if we can compete with the 6.5 crowd at the next PRS match.
TPH
