Twenty five ccaliber grooved barrels
What is the optimum number of grooves in a 25 caliber bbl? I see bbls with 2,3,4,5,6 and 8 grooves. I have no clue how to evaluate.
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That is a really interesting question. I have shot 2, 4, 5 and 6 no 3 or 8 that I recall. Twist rate and even direction (heavy recoil) plus if they are cut (how) or forged.
Affording a barrel from a top rated manufacture will be expensive enough for me just picking from their offerings with adding custom made fees.
added I would expect barrel life of a 257 Weatherby Mag to be on the short side. Stainless is a good plan. I'd be using a ball powder for my loads too.0 -
Optimal number of grooves and rate of twist (concentric) requires more variable input...
Case capacity and bullet weight / architecture play important roles in the equation...
For example the .30-06 cartridge can go from a 55gr discarding sabot submunition accelerator load to a 240gr monolithic solid with many selections in between...
Do you prefer lighter or heavier projectiles..
Do you prefer hot loads or middle of the road factory loads...
Velocity (fps) plays a role not only in accuracy but in stability...
Mike0 -
generally 2 or 4 grooves are the norm.
lots of variables are considered.0 -
I can only address pistol barrels I have done Ransom rest testing on many match grade pistol barrels in both 22 lr and 45 ACP but also on 2grove rifle barrels I have seen good results on all as well as poor results on just about all including different types of rifleing
difference comes from quality of maker no set rule sorry0 -
While with a well made factory oem or top end aftermarket replacement bbl there may be a particular set up (number of grooves and rate of twist concentric and oal) that provides optimal performance from a specific caliber / cartridge while using factory ammo within a moderate range or performance envelope (bullet weight - velocity - projectile architecture) there are still many variables that need to be factored in in order to satisfy your inquiry
Even assuming a common caliber / diameter there is room for error. I only have two .25 caliber rifles (.257 roberts +P and a .250-3000 savage) both of which have some performance peculiarities that probably required a dramatic departure in bbl design in order to achieve good performance from a narrow range of projectile weights - bbl designs that most likely would not work well with other .25 caliber cartridges
A best bet for you is to identify what factory set up is most often utilized by a known major manufacturer (rate of twist concentric and number of grooves and oal) specific to your cartridge (not simply for your caliber / diameter)
Or to inquire what works best from an trusted well established aftermarket bbl manufacturer
And you will need to bench test factory ammo or hand loaded offerings to determine what combination of cartridge design parameters work best with the rifle / platform / bbl you choose
Please excuse my amateur attempts to quantify the variables and answer your question - I am not an expert on this topic - and while I hope that my input is useful I look forward to a true experts contribution (or correction of my attempt to respond)
Mike0 -
I am looking at a custom 257 Weatherby on a Classic Winchester model 70 action. Bbl is a 27" stainless Benchmark 3 groove with 1 in 9 twist and fluted. I asked my question because I am surprised at 2 and 3 groove bbls being used. Had always thought 4 grove was standard 0 -
quote:What is the optimum number of grooves in a 25 caliber bbl?
To answer this question first before launching into a difficult discussion of barrel design and characteristics, there really is no 'optimum' number of grooves unless you specify an extremely lengthy list of definitions of the loads you choose to shoot.
The standard .25 caliber barrels use 6-groove, 10-twist barrels for modern loads shooting modern bullets. If we shift our attention to lower pressure loads or varmint bullets, we often revert to the older version of the 12-twist, 6-groove barrels. When we run compressed black powder loads, the twist will sometimes slow to a 1:14" in a 6-groove barrel.
The rest of the selections for number of grooves will usually be determined by what is popular and successful in the media support or even what we determine to be superstition, that which has shown promise before and we hesitate to change fearing failure.
The rules regarding twist rate and number of grooves for bullet stability is going through a period of change due to one man's influence on bullet making as it relates to barrels. It is unfortunate in my opinion that he has changed some of the math in order to change how the variables are weighted when we still see the same support from original mathematical models. But in order to assume and be granted the mantle of 'expert' he has to seemingly make it work in his model so as to deny the basis of the older models.
The older rule of thumb for the benchrest shooters was to use the slowest twist which would stabilize the bullet at the distance being fired. This has held true and is still being touted today. But with the influx of heavy for caliber bullets, the need for a better understanding of twist rate, number of grooves and the geometry of those grooves is being paid more attention to because of the bullet design. We are seeing in increase towards much faster twist rates in order to accommodate these newer, longer, heavier bullets, although the challenge is to maintain the integrity of the more normal lighter and shorter bullets when fired in these faster twist barrels.
When we choose a different number of grooves, the barrel maker also has to pay attention the mathematical design of those groove, the spacing or width, the depth and how the edges meet when the twist rate changes. It is not just simply setting the machine up to create 2,3,4,5,6 or 8 grooves.
So, unless I'm shooting some historical cartridge and bullet combination I will normally choose either a straight 6-groove or the slightly different version 5R for the shooting I do with modern cartridges and bullets. I have recently taken possession of a 1:7" twist, 5R .25 caliber barrel which will be dedicated to the use of a newly designed heavier bullet. Testing is pending delivery of those bullets from the manufacturer.
Best.0 -
Well, MY three groove barrel is a .308.
The logic was that the broader lands would wear longer.
But I am no longer shooting rifles much, so I may never know if it helped.
I have not seen a commercial two groove barrel.0 -
Benchmark makes commercial 2-groove barrels currently.
There is a phenomenal amount of information and experimentation data attached to the study of the number of grooves best suited to rifle barrels. There were 2-groove barrels used as early as the mid-1800's with round balls wearing a band around their middle. Alignment of the band and the rifling was critical.
Currently Dan Lilja and Pac-Nor both use 3-groove rifling, with Dan's website having a lengthy discussion of that choice. The rest can be found on many of the current crop of modern barrels. Marlin pioneered the 16-groove rifling, aptly named 'Micro Groove' due to the lack of depth of those grooves. These were used prevalently in .22LR barrels and often they were irreverently referred to as 'Micro Scratch' barrels.
I am not aware if there has there been a definitive study which concluded that there was a clear winner as to the number of grooves used in a barrel for accuracy testing. I use the 5R rifling in the vast majority of the barrels I build with although when working with .22 cal. and 6mm, I have reverted to using 4-standard grooves instead.
Best.0 -
The 1903 US Military rifle I had made by Remington had a 2 groove barrel.
You presented an obviously complexed question to answer. I suspect that to optimize the accuracy of a .25 caliber barrel that, as mentioned, a lot depends on the speed, construction, and weight of the bullet used. I have no idea where the sweet spot is.
The combination of depth, twist, and number of grooves that gives the widest window of stabilization for the widest amount of speed, and bullets used.0
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