ELR rifle barrel life is always an issue for service rifle , competition folk literaly have multiple dope for changes to a bore after 20+rds
So larger bores will likely work better
Here is the list of cartridges / bullets used during the last Ko2M finale
375 Chey-Tac with 400 gr Lazer,
416 Barrett with 500 gr Lazer,
37 XC with 400 gr Lazer,
375 Chey-Tac with 400 gr Lazer,
no data,
375 Chey-Tac with 400 gr Lazer,
416 Hellfire with 500 gr Lazer,
416 Hellfire with 550 gr Lazer,
416 Hellfire with 550 gr Lazer,
416 Hellfire with 525 gr Lazer,
416 Barrett with 500 gr Lazer,
416 Barrett with 550 gr Lazer,
416 Barrett with 500 gr Lazer,
375 Chey-Tac with 400 gr Lazer.
*The .416" Hellfire is based on an elongated Chey-Tac case, necked up to .416".
A post from FB on 400MODBB in 33XC
This is a reconstruction of a post I put up last year, about my experience with my Bartlein 400MODBB 33XC barrel.
There are claims out there giving 400MODBB 1.5x to 2x longer life when compared with 416 SS.
My Bartlein 400MODBB was .338 Cal 1 5/8" Ø, 34" 1:7.5, given the full TacomHQ Structured treatment, including cryogenic.
The expected life was 850-1000.
I had set my mind on using the Warner Flat Line 285gr with Tubb Nosering®, G1 0.968, G7 0.484
The barrel was initially chambered with Manson Precision Reamers to 33XC Tubb 4 6/25/2020 print, which gives a 0.225" freebore.
In what follows, Mz were 2900-3150fps, and in the UK using Vit 570. I did try 24N41.
When I visited David July 2022, the barrel already had 67 shots.
We were shooting the Warners for the firest time and David advised seating on the lands.
We loaded and shot 72, but the seating CBTO was not changed from the initial measurement.
After zeroing at 200 yds, we went to 1,500 and 2,000 yds, and hitting plates.
Back in the UK, after 208 shots, the CBTO had moved out 0.186" and there was not enough bullet in the case without a > 0.100+ jump.
Through Manson Reamers, I found a earlier Tubb print for Cutting Edge Lazers with 0.100" freebore, but it noted for Warner Flat Line, use a 0.050" freebore.
My barrel had enough material to re-chamber, so Manson supplied a 0.050" freebore reamer and I re-chambered.
I was concerned about what had happened, so kept records of CBTO measurements for different bullets, but still just shooting the 285gr Warner Flat Lines.
I recorded CBTOs for Berger 300gr OTM, DTAC 299, Cutting Edge LZR 265gr, Badlands 265gr & 285gr, and Warner Flat Line 265gr.
If you can see the graph, after 61shots, the lands had moved 0.106" and interestingly after 3 TMS shots, a further 0.047".
By 211 shots, the Warner CBTO had moved 0.209" but after 167 shots I had stopped using them, because the results were tanking, no better than 1.5MOA @ 200 yds.
I had changed to Cutting Edge LZR 300gr, which gave sub 0.4MOA at 200 yds for the next 99 shots and achieved sub 1MOA at 1760 yds in difficult wind.
This restored my faith in the 33XC, despite the barrel rapidly approaching End of Life.
My take away on my experience with this 400MODBB barrel is twofold.
The first, the sleek profile of Warner Flat Lines (in .338 which is all I have used) are so incredibly sensitive to wear on lands, that if you had a 25 shot competition, the jump for the last shot will have increased by at least 0.015"
For a Cutting Edge LZR 265gr, it would only have increased by 0.007"
By 61 shots, Warner increased by 0.106" but the LZR, only 0.019" and the same for the DTAC299.
I leave it up to you to decide if that wear is acceptable.
The second take away, with a competitive BC bullet, the wear on 400MODBB lands mean that if you prepare for a competition, you need to know what an increase jump of 0.015" - 0.020" does to your last few 2 mile shots.
Then, when you go home, you will be starting again working up a new load, but you’ll be chasing a runaway CBTO.
I am led to believe the following:
1. Despite people complaining to Bartlein, they blame the shooter.
2. There might be less effect with smaller calibers, but there may be some relationship between the ratio of bullet diameter and the land wear / change in CBTO.
3. There may have been a batch of Bartlein 400MODBB barrels that were poorly heat treated or other there were other material problems. This might explain differing experiences.
If you look at my website (still WIP), you will see that I have 2 x 37XC barrels and 3x 416 Barrett projects in the build, all Bartlein 400MODBB
I will be keeping records of CBTOs after every trip to the range.
My new K&S Arms 33XC barrel is 416 SS, but I will be chambering it with a 0.050" freebore and use Cutting Edge LZR 300gr Single Feed.
The original Bartlein 33XC will be wire EDM’d in half to examine the bore and carry out hardness tests.
View attachment 8335728
www.marinecorpstimes.com
