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Considering a build in 6.5-284 using a Lilja 3 groove barrel as the title indicates. Just curious if anyone here has done this or has feedback in general regarding the 3 groove design. Twist rate would be 1:8. I've read mixed opinions regarding the design and various issues including projectile fragmentation.
Thanks!
Good question. Everyone I know shooting that chambering has a 4 groove. I would consult Lija and the bullet makers like Berger etc...
Thanks I didn't think to email bullet manufacturers for feedback. I was just intrigued by the idea of 3 grooves, 4 groove might be the best.
Typically 3 groove barrels and fast twists are not bullet friendly. I've never seen a 3 groove barrel that shot as well as a 4,5 or 6 groove.
Quote:
Originally Posted by sharpshooter
When you are up in the Pac NW, give me a PM and you can shoot my 3-groove 6.5 Creedmoor. Shoots as well or better than a 4, 5, or 6. The 3-groove replaced a 5 groove and kicked it's butt in the accuracy department. Faster speeds, easy clean, and tack driving accuracy.
15 shots at 100 yards with my 6.5 Creedmoor 3-groove:
https://im1.shutterfly.com/ng/servic...746025/enhance
Day before yesterday I ordered a new 2-GROOVE barrel for my .308.
One thing to remember, the lands will be wider which gives the throat more "beef". Less tendency to erode where you have more lands and only so much room to squeeze them in.
As Deadshot2 pointed out, the design has less tendency to erode in the throat, the 6.5-284 is known to be hard on barrels. From what I've read after a certain round count there has been projectile fragmentation(seems random across the board and not specific to a manufacture). It's theorized its due to the wider lands which are squeezing the bullet with more force while having a lower bearing surface ratio. Hence the higher velocities. Possibly the answer is to shoot bullets with thick jacket designs.
Thanks for the feedback guys.
The issue is probably more predominant in barrels with cut rifling that uses a more traditional "square" cut. Canted rifling where the root of the rifling is wider than the peak is by design less prone to this kind of failure. In reality the canted rifling, often found in buttoned or hammered barrels is just a "flat spot" away from "Polygonal Rifling" which gives far better gas seal and resultant speed.Quote:
Originally Posted by RustyShackle
When I ordered my .30 cal barrel I spent some time with one of the owners at Benchmark and he just kept shaking his head saying "they sure do shoot!" (we were talking about the 2 groove, I already knew the 3-groove does :) )
FWIW, I might look to the composition of the basic barrel metal itself. Different steel makers may have slightly different formula's and/or quality control. Various "inclusions" in the metal itself can cause these failures just like they cause a lot of machinists to loose hair. :)
Deadshot2, just curious how far you have stretched the distance shooting the 2 and 3 groove barrels? I have read about the old 03A3's with two groove barrels and the original acceptance reports stated "they shot within acceptable accuracy requirements". But this was also probably a moderately liberal margin due to the war effort. I believe the reason they went to two groove vs four was cost cutting measures and to expedite production. Maybe not relevant to the discussion at hand but something I've been pondering.
I have decided that the barrel material will be stainless (416) as they tend to have longer life vs cm barrels. Is there really that large of a difference in the composition for the material for the top barrel makers?
I am not a metallurgist however I am an engineer and can grasp the many concepts of the different properties but probably lacking as it relates to compositions and how it relates to barrel characteristics. Any recommended reading regarding that?
And to squirrel off here I've also come across information that indicates odd number grooves give the most equal engraving resistance so the bullet is best centered in the bore which tend to have better accuracy. As the lands are not equally opposed on either side of the bore, rather lands and grooves oppose one another.
I too have heard/read that the 2-groove was used to expedite production. Don't know how true that is but sounds good.Quote:
Originally Posted by RustyShackle
As for accuracy and distance, my three groove holds accuracy as far as I choose to shoot (currently 800-1k). No loss of accuracy other than wind of course. If I were to try and stretch farther I believe there is an advantage to the fewer grooves due to less bullet distortion. As long as the bullets have uniform jacket thickness (advantage to those with thin jackets) they remain balanced and won't pitch or yaw. When that happens too much of the side of the bullet is hitting the air and they drop speed like a blue-haired old lady drops quarters in a slot machine.
Back to the old O3-A3, the two groovers were sought after for their LR accuracy. I happen to have one and it IS accurate. Too bad it was sporterized but it was my Dad's so it's double "special".
The two-groove .308 is still 12 weeks out. It's going on my Remington SS action but I'm having it "nutted".
Having followed this stuff for quite some time, my take is a good barrel is a good barrel regardless of groves, ratchet, squares or rectangles.
And two groves are some and some. If done to spec, they performed on par with 4 and 6 (Smith Corona produced a fair number of barrels in 6 grove late into the war) )
Done wrong, the two groves of course did not shoot well.
It was an expediency measure, the bolt actions were usually second tier use not front line (some did serve and beyond snipers) but most were rear line troops, artillery, chemical, prisoner of war, Seabeas (those two used Model of 1917s) just anyone that needed a weapons but not a Garand.
Oddly one mfg said it was going to9 reduce their rate to go from 4 to 2 and kept on making them as 4s under an exemption (they were setup and two is a lot different than 4)
Range had nothing to do with accuracy, either they were or were not. Groves do not either.
You would have to talk to someone who has bore scoped a lot of barrels to verify this, I have been told the 416 barrels to last longer but in adverse firing conditions the metal "flakes" in the throat area where CM just cracks. Don't know how true that is or under what circumstances but another factor that makes rifles more interesting.Quote:
I have decided that the barrel material will be stainless (416) as they tend to have longer life vs cm barrels. Is there really that large of a difference in the composition for the material for the top barrel makers?
i don't plan on running hot with the barrel, I hadn't heard of the "flaking" issue. Guess more reading for me.Quote:
Originally Posted by Robinhood
If comparing C/M barrels with 416 barrels for longevity you have to state which C/M barrel steel. Is it 4140 or 4150? 4140 is the commonly used alloy because the 4150 is harder and presents some challenges when creating the barrel itself. 4150 would probably give more usable life but how much more and is it worth it for most firearms?
When referring to 416 it's almost always 416R "Crucible Steel" or one of the "clones" as "Crucible" is a TM.
Experience with a Lilja 3 groove but 7mmRUM chamber. Groups opening up at 700 rounds. Cleans like a dream from day one. Don't know if more or less grooves would make any difference on an overbore like this.
I have a 3 groove X-caliber fluted in 7-08, 8.5 twist and a 10 twist 6 groove, same reamer and action. The 6 groove shows slightly better accuracy potential. Sort of apples and oranges comparison though.
Loathar Walthar uses a harder stainless steel and CM. Some barrel finishers don't care to work on them.Quote:
If comparing C/M barrels with 416 barrels for longevity you have to state which C/M barrel steel. Is it 4140 or 4150? 4140 is the commonly used alloy because the 4150 is harder and presents some challenges when creating the barrel itself. 4150 would probably give more usable life but how much more and is it worth it for most firearms?
When referring to 416 it's almost always 416R "Crucible Steel" or one of the "clones" as "Crucible" is a TM.
Some calibers are Savage Pre fit with a Varming profile so you can go around that.