New to 308

[Buckeye Chuck]

I'm new to the 308 cartridge and am a little confused on barrel twist rates for it. I am in the process of building a M40 clone for the CMP Vintage Sniper Matches and would like to know what is the best barrel twist rate for 308. So I'm looking for your experience, opinions and facts on twist rate for this cartridge.
Thanks in advance
Buckeye Chuck

 

[oldrifleman]

What bullet are you planning to use. probably 1/10"twist

 

[stello1001]

8 to 11.25 should work fine with 10 being a pretty good choice

 

[db2000]

The higher the number (11.25) the slower the twist. One rotation per 11.25” (1:11.25). As stated 1:10 is probably most common. The faster twist barrels stablize heavier and longer bullets usually better than slower twist. Caliber and other factors matter but this is the general rule.
1:10-1:11.25 should be fine with 150-185 gr bullets, which are most common. Different barrels, even with the same twist rate, may prefer different bullet/powder combos or brands of factory ammo. You just have to experiment.

 

[Bearcatrp]

Go with 1:10 so you can use a variety of bullets. If you plan on staying under 185 grain, 1:11.25 will work. Do you reload or buying commercial ammo?

 

[Buckeye Chuck]

I do reload and will be mostly using 168 and 175 grain bullets

 

[Skeptic1]

I prefer 11.25

 

[oldrifleman]

With that knowledge I would also recommend the 11.25. All my shooting uses 169 and 175 grain bullets. The 11.25 is perfect for those loads. If you ever go bigger the 10 will cover you, but the 11.25 is a tried and true 308 twist.

 

[Terry Cross]

With that knowledge I would also recommend the 11.25. All my shooting uses 169 and 175 grain bullets. The 11.25 is perfect for those loads. If you ever go bigger the 10 will cover you, but the 11.25 is a tried and true 308 twist.

Interesting story about how the 1-11.25" twist became THE legendary magic sauce.

 

[oldrifleman]

Interesting story about how the 1-11.25" twist became THE legendary magic sauce.

Yeah that was told to me and likely told to the person who told me and so forth. It is how folk lore becomes legend

 

[surgeon260]

What's the magic story?

Terry, what do you prefer in your 308s?

 

[db2000]

1:10 175 SMK Savage APO.

 

[DeathBeforeDismount]

If you ever want to shoot heavier bullets like the 185 or 205, I would do a 10 twist. No reason not to.

 

[Terry Cross]

What's the magic story?

I'm gonna fuck this up so @Frank Green maybe can find time to chime in one day with more clarity of details.

Something along the lines of . . . . . .
When the M24s were being spec'd out in the 80s, smart dudes in lab coats decided that an 11.25" twist rate would be optimal for the issue "sniper" rounds. I think the 168s were still the standard but the new Sierra 175s were getting ready to come out of the gates.

During a phone call, Boots told me that the first barrels tested for the program and the first production runs of M24s that still used custom barrels were supposed to be 11.25" twist rates but the closest sine bar for the P&W rifling machines actually produced blanks with 1-10.8" twist rates.

Even though it was Boots that was telling me this, I think it was Mike Rock that was actually making the barrel blanks for that development and first runs.

Supposedly the later M24s that used "made in house/hammer forged" Remington barrels were pretty close to the 11.25" rate.

So all of the original development and aura surrounding the program that made 11.25" 5R barrels the magic golden recipe to chase and clone weren't really 11.25" at all. Those early guns set the performance bar than none of the following production guns ever lived up to.

Just a few short years later, the SR25/M110 program called for the same 11.25" twist spec.
I think Boots ran the original barrels for the early development of that program and I believe they were closer to the actual requested spec.

Terry, what do you prefer in your 308s?

For years, I kept 1-11" in inventory for all my .308s. and 1-10" twists for the WinMags. Still built .308s with 1-10 and 1-12 on request and they shot fine but my Go To default was 1-11".

Since then, the heavy 30s like the 300 Norma and 300 PRC have mainstreamed more of the longer, high BC bullets. So for the last 15yrs I have standardized 1-10" for all my .308s and 1-8.5" for all the heavy 30s.

My preferences should not be the yardstick anyone else goes by. I still don't know shit and still do stuff that proves I can't adult worth a damn.

 

[oldrifleman]

I still don't know shit and still do stuff that proves I can't adult worth a damn.

Being here on the Hide proves the same for the rest of us

 

[WeR0206]

I do reload and will be mostly using 168 and 175 grain bullets

I'd give a hard look at the new SMK's that are 169 and 177 (supposed to use similar load info as 168 and 175 cousins).

In my 308 bolt action build (using shouldered 1:10 24" pre-fit from Criterion chambered by Northland Shooter Supply) with 177 smk's pushed by 41.3gr AR-Comp in SRP Lapua brass (~2,690 avg fps) loaded at mag length (2.850”) I was getting 5 shot groups in the 3's and 4's during the first 50 shots down the tube.

 

[softcock]

I do reload and will be mostly using 168 and 175 grain bullets

11-25 5R and 175smk's .
.

 

[Ronin22]

308 is great. 708 is a riot!

 

[Frank Green]

I'm gonna fuck this up so @Frank Green maybe can find time to chime in one day with more clarity of details.

Something along the lines of . . . . . .
When the M24s were being spec'd out in the 80s, smart dudes in lab coats decided that an 11.25" twist rate would be optimal for the issue "sniper" rounds. I think the 168s were still the standard but the new Sierra 175s were getting ready to come out of the gates.

During a phone call, Boots told me that the first barrels tested for the program and the first production runs of M24s that still used custom barrels were supposed to be 11.25" twist rates but the closest sine bar for the P&W rifling machines actually produced blanks with 1-10.8" twist rates.

Even though it was Boots that was telling me this, I think it was Mike Rock that was actually making the barrel blanks for that development and first runs.

Supposedly the later M24s that used "made in house/hammer forged" Remington barrels were pretty close to the 11.25" rate.

So all of the original development and aura surrounding the program that made 11.25" 5R barrels the magic golden recipe to chase and clone weren't really 11.25" at all. Those early guns set the performance bar than none of the following production guns ever lived up to.

Just a few short years later, the SR25/M110 program called for the same 11.25" twist spec.
I think Boots ran the original barrels for the early development of that program and I believe they were closer to the actual requested spec.


For years, I kept 1-11" in inventory for all my .308s. and 1-10" twists for the WinMags. Still built .308s with 1-10 and 1-12 on request and they shot fine but my Go To default was 1-11".

Since then, the heavy 30s like the 300 Norma and 300 PRC have mainstreamed more of the longer, high BC bullets. So for the last 15yrs I have standardized 1-10" for all my .308s and 1-8.5" for all the heavy 30s.

My preferences should not be the yardstick anyone else goes by. I still don't know shit and still do stuff that proves I can't adult worth a damn.

I think for the most part Terry has it spelled out pretty good and I can only go off of memory and what I've been told by Boots and even places like KAC and Krieger when we worked there.

What I call the Sine Bar rifling machine predates the P&W hydraulic rifling machines. You moved the bar on the Sine Bar machine to a corresponding number lets say it's 10 and that would then give you a 10 twist. The later P&W hydraulic rifling machines had a leader bar running the length of the machine and for a rifler doing 30cal... it was for 10 twist. Maybe they made some bars for 12 twist. For 50cal barrels it was a 15 twist and what ever leader bar was in the machine twist wise....that's all it could do. What places like Krieger or Boots did was they modified what I would call the spindle box assy and added a plate with a gear system and the gear system was driven by the leader bar as the leader bar needs to be on the machine no matter what. By changing a combination of gears you could change the twist rate because to my knowledge nobody made different leader bars and if they did would've cost a boat load of money and not easy to change out.

If I recall correctly from Boots or Rock or whomever... the Pratt Hydraulic riflers that they have (not Sine Bars) with the gear set up they had could actually do 11.27 twist barrels. That always has stuck with me and I think everyone just called them 11.25. That's how they ended up with 11.25 twist barrels and becoming the golden child back in the day for the go to for 308w. I'll say Kreigers set up was a touch more refined and could do even more twist rates. Back when we worked at Krieger if someone called up and wanted say a 6.5mm barrel in a 8.5 twist... we would pull the gear chart for the machine we typically did the 6.5's on and look to see if we had a specific gear combination for 8.5 twist for it. If we didn't but we could do say a 8.6 and the next fastest was 8.48 we would go with the 8.48 and just stamp the barrel 8.5 twist. The 6.5mm example is just an example and not an exact one that I remember. Tracy has a picture here somewhere of the gear plate system and I'll ask him to dig it up but won't see him till next week.

I don't know who or why someone wanted a twist faster than 12 for the 308w cartridge or how that change got pushed etc.... Even today most bullets at 308w velocities will handle bullets up to 190gr. Even some 200gr bullets depending on design. The 168gr SMK will fly out of a 13 twist barrel. The 168MK was originally for 300m competition if I recall correctly and for years was the best bullet around for even hi power out to 600 yards it's pretty good. Back in the day the next bullet up that was actually better was the 180SMK and then the 190. Even Steve who works here and for years worked at Krieger doing rifling won the State Service Rifle Long Range Championship with his M1A and a Krieger barrel back in the late 80's or real early 90's. He loaded and shot the 180SMK. I bought that rifle from him a few years ago as he no longer wanted it.

When the 11.25 became the golden child I think Terry is correct that Remington then started making hammer forged barrels as 11.25 twist with 5R rifling copying / trying to duplicate Boots or Rocks barrels. Krieger and Boots where friends and shooting buddy's and back in the day Boots asked John on a gentlemen's agreement that John would never do 5R type rifling unless Boots asked him to. I want to say this was before Rock was in business and even possibly before Rock worked for Boots. I'm kind of guessing there as it's a tad before my time. No and Krieger never worked for Boots and took any training from Boots. That's a old myth. John told me that Boot's tipped John off to an auction for a rifling machine, drill and reamer back in the late 70's or say 1980 time frame. Other than that the only tip that Boots ever gave John was to watch how the bore reamers where sharpened/ground to give the best bore reaming finish prior to prelapping. I'm sure years later they would chit chat about stuff but John said that's all Boots ever really did for him. Again primarily shooting buddies.

As far as the SR25/Mk11/M110 guns go I do know that Boots originally started making all of those barrels for KAC. Reed or Art told me that they basically had a open po with Boots and would take whatever Boots could send them... even when KAC started buying blanks from Remington. So there was a time period that KAC I believe was getting barrels from Boots and Remington together.

Let me do some brain digging and look for that pic and I'll try and update this post next week sometime.

Later, Frank

 

[oldrifleman]

I think for the most part Terry has it spelled out pretty good and I can only go off of memory and what I've been told by Boots and even places like KAC and Krieger when we worked there.

What I call the Sine Bar rifling machine predates the P&W hydraulic rifling machines. You moved the bar on the Sine Bar machine to a corresponding number lets say it's 10 and that would then give you a 10 twist. The later P&W hydraulic rifling machines had a leader bar running the length of the machine and for a rifler doing 30cal... it was for 10 twist. Maybe they made some bars for 12 twist. For 50cal barrels it was a 15 twist and what ever leader bar was in the machine twist wise....that's all it could do. What places like Krieger or Boots did was they modified what I would call the spindle box assy and added a plate with a gear system and the gear system was driven by the leader bar as the leader bar needs to be on the machine no matter what. By changing a combination of gears you could change the twist rate because to my knowledge nobody made different leader bars and if they did would've cost a boat load of money and not easy to change out.

If I recall correctly from Boots or Rock or whomever... the Pratt Hydraulic riflers that they have (not Sine Bars) with the gear set up they had could actually do 11.27 twist barrels. That always has stuck with me and I think everyone just called them 11.25. That's how they ended up with 11.25 twist barrels and becoming the golden child back in the day for the go to for 308w. I'll say Kreigers set up was a touch more refined and could do even more twist rates. Back when we worked at Krieger if someone called up and wanted say a 6.5mm barrel in a 8.5 twist... we would pull the gear chart for the machine we typically did the 6.5's on and look to see if we had a specific gear combination for 8.5 twist for it. If we didn't but we could do say a 8.6 and the next fastest was 8.48 we would go with the 8.48 and just stamp the barrel 8.5 twist. The 6.5mm example is just an example and not an exact one that I remember. Tracy has a picture here somewhere of the gear plate system and I'll ask him to dig it up but won't see him till next week.

I don't know who or why someone wanted a twist faster than 12 for the 308w cartridge or how that change got pushed etc.... Even today most bullets at 308w velocities will handle bullets up to 190gr. Even some 200gr bullets depending on design. The 168gr SMK will fly out of a 13 twist barrel. The 168MK was originally for 300m competition if I recall correctly and for years was the best bullet around for even hi power out to 600 yards it's pretty good. Back in the day the next bullet up that was actually better was the 180SMK and then the 190. Even Steve who works here and for years worked at Krieger doing rifling won the State Service Rifle Long Range Championship with his M1A and a Krieger barrel back in the late 80's or real early 90's. He loaded and shot the 180SMK. I bought that rifle from him a few years ago as he no longer wanted it.

When the 11.25 became the golden child I think Terry is correct that Remington then started making hammer forged barrels as 11.25 twist with 5R rifling copying / trying to duplicate Boots or Rocks barrels. Krieger and Boots where friends and shooting buddy's and back in the day Boots asked John on a gentlemen's agreement that John would never do 5R type rifling unless Boots asked him to. I want to say this was before Rock was in business and even possibly before Rock worked for Boots. I'm kind of guessing there as it's a tad before my time. No and Krieger never worked for Boots and took any training from Boots. That's a old myth. John told me that Boot's tipped John off to an auction for a rifling machine, drill and reamer back in the late 70's or say 1980 time frame. Other than that the only tip that Boots ever gave John was to watch how the bore reamers where sharpened/ground to give the best bore reaming finish prior to prelapping. I'm sure years later they would chit chat about stuff but John said that's all Boots ever really did for him. Again primarily shooting buddies.

As far as the SR25/Mk11/M110 guns go I do know that Boots originally started making all of those barrels for KAC. Reed or Art told me that they basically had a open po with Boots and would take whatever Boots could send them... even when KAC started buying blanks from Remington. So there was a time period that KAC I believe was getting barrels from Boots and Remington together.

Let me do some brain digging and look for that pic and I'll try and update this post next week sometime.

Later, Frank

Wow, that was one of the best history lessons I have read in years. Not sure how but that should be preserved! Thank you Frank!

 

[Terry Cross]

I think for the most part Terry has it spelled out pretty good and I can only go off of memory and what I've been told by Boots and even places like KAC and Krieger when we worked there.

What I call the Sine Bar rifling machine predates the P&W hydraulic rifling machines. You moved the bar on the Sine Bar machine to a corresponding number lets say it's 10 and that would then give you a 10 twist. The later P&W hydraulic rifling machines had a leader bar running the length of the machine and for a rifler doing 30cal... it was for 10 twist. Maybe they made some bars for 12 twist. For 50cal barrels it was a 15 twist and what ever leader bar was in the machine twist wise....that's all it could do. What places like Krieger or Boots did was they modified what I would call the spindle box assy and added a plate with a gear system and the gear system was driven by the leader bar as the leader bar needs to be on the machine no matter what. By changing a combination of gears you could change the twist rate because to my knowledge nobody made different leader bars and if they did would've cost a boat load of money and not easy to change out.

If I recall correctly from Boots or Rock or whomever... the Pratt Hydraulic riflers that they have (not Sine Bars) with the gear set up they had could actually do 11.27 twist barrels. That always has stuck with me and I think everyone just called them 11.25. That's how they ended up with 11.25 twist barrels and becoming the golden child back in the day for the go to for 308w. I'll say Kreigers set up was a touch more refined and could do even more twist rates. Back when we worked at Krieger if someone called up and wanted say a 6.5mm barrel in a 8.5 twist... we would pull the gear chart for the machine we typically did the 6.5's on and look to see if we had a specific gear combination for 8.5 twist for it. If we didn't but we could do say a 8.6 and the next fastest was 8.48 we would go with the 8.48 and just stamp the barrel 8.5 twist. The 6.5mm example is just an example and not an exact one that I remember. Tracy has a picture here somewhere of the gear plate system and I'll ask him to dig it up but won't see him till next week.

I don't know who or why someone wanted a twist faster than 12 for the 308w cartridge or how that change got pushed etc.... Even today most bullets at 308w velocities will handle bullets up to 190gr. Even some 200gr bullets depending on design. The 168gr SMK will fly out of a 13 twist barrel. The 168MK was originally for 300m competition if I recall correctly and for years was the best bullet around for even hi power out to 600 yards it's pretty good. Back in the day the next bullet up that was actually better was the 180SMK and then the 190. Even Steve who works here and for years worked at Krieger doing rifling won the State Service Rifle Long Range Championship with his M1A and a Krieger barrel back in the late 80's or real early 90's. He loaded and shot the 180SMK. I bought that rifle from him a few years ago as he no longer wanted it.

When the 11.25 became the golden child I think Terry is correct that Remington then started making hammer forged barrels as 11.25 twist with 5R rifling copying / trying to duplicate Boots or Rocks barrels. Krieger and Boots where friends and shooting buddy's and back in the day Boots asked John on a gentlemen's agreement that John would never do 5R type rifling unless Boots asked him to. I want to say this was before Rock was in business and even possibly before Rock worked for Boots. I'm kind of guessing there as it's a tad before my time. No and Krieger never worked for Boots and took any training from Boots. That's a old myth. John told me that Boot's tipped John off to an auction for a rifling machine, drill and reamer back in the late 70's or say 1980 time frame. Other than that the only tip that Boots ever gave John was to watch how the bore reamers where sharpened/ground to give the best bore reaming finish prior to prelapping. I'm sure years later they would chit chat about stuff but John said that's all Boots ever really did for him. Again primarily shooting buddies.

As far as the SR25/Mk11/M110 guns go I do know that Boots originally started making all of those barrels for KAC. Reed or Art told me that they basically had a open po with Boots and would take whatever Boots could send them... even when KAC started buying blanks from Remington. So there was a time period that KAC I believe was getting barrels from Boots and Remington together.

Let me do some brain digging and look for that pic and I'll try and update this post next week sometime.

Later, Frank

Thanks for sharing Frank.
Cool clarification on the equipment stuff too. I just vaguely remembered talk about sine bars so no doubt I was using the wrong terms for the wrong machines.

Somebody could give me a rifling machine and I wouldn't even know how to power it up. That's prolly God's way of keeping me from getting pulled into a spindle and my spectacular death becoming the next YouTube sensation.

My recollection is the same regarding the 5R rifling and Boots only helped John locate his first rifling machine.

I did find my file folder with a bunch of the correspondence and copies of articles that Boots would write up for I guess sort of a news letter he would share. I need to bring that home one weekend and go through it. There might be some neat things that aren't totally over my head.

 

[surgeon260]

Me when Frank or Terry post anything: