18" or 22" predatOBR 260

[Z06pilot]

I am going to order a predatOBR 260 this week. I have a mark 8 3.5-25, a sico omega, prs stock, geissele match trigger, and sico radius in hand waiting to install on this rifle. I plan to shoot it supressed most of the time, and if they shoot well use flatline solid bullets for targets out to about 1400 meters. Given the additional length of the supressor, the 22" seems a bit long, especially given the relativly thin profile of the barrel. On the other hand, i would imagine a 80-100fps speed difference, and possibly a better sd with the 22" barrel. Thoughts?

 

[padom]

Why do you think barrel length will give you a better SD? That has to do with the load you choose....

I highly doubt you will be able to run flatlines in a 260rem AR10 at any length or speed that makes them worth their money before you run into magazine length restrictions... If I was going to be shooting to 1400yds a Larue OBR wouldnt be my first, second or third choice either.

1. 26" Bolt gun in 6.5cm or 260rem
2. Custom 22" 6.5cm Bartlein/MEGA AR10 (If you are dead set on an AR10)
3. JP 22" 6.5cm AR10 if you want a factory AR10 that shoots

 

[NukeMMC]

I have a GAP10 Gen 2 (Seekins upper/lower) in .260 with a 20" Bartlein 1:8.2". Even using KAC magazines, my use of any VLD-style bullet will not get the ogive close enough to the lands. I just loaded 130gr ELDMs to a .030" jump and they were mag-length limited. 140SMKs are fine but the 130TMKs are even longer than the ELDMs and would end up with a .050-.060" jump. Pretty sure you'll not find the Flatlines to be THAT jump tolerant.

 

[padom]

Exactly. This is why everyone goes 6.5cm in an AR10 with .264 bullets. You won't be mag limited.

 

[DuneShoot]

I ordered their recent FDE heavy offering with the option to buy a 260 barrel.
I have been shooting it in the 308 configuration and after todays range trip I decided to finally swap over to 260.

I went with the 22". Figured for a bench gun why not squeeze all the velocity I can out of it.
You will need a heavier buffer if you're going to use that Omega. I proved it worked on mine today (in 308) where as yesterday and previous range trips I have bad luck with the Omega and their H2 buffer.

 

[Defender3]

I understand this is a single data point so YMMV. I’'ve owned a 22"” .260 tOBR since February and have about 1200rds down the tube. I’'m limited on range choices so the majority has been at 100 yards, but I've had multiple range sessions on Quantico at 600, 800 and 1,000 yards.

I selected the 22"” so I could squeeze a bit more velocity out of the rifle for the longer ranges (all I do is square range stuff). I'’ve shot it suppressed with the LaRue TQ and while not a large velocity increase, there were increases in MVs.

I’'ve shot a variety of factory ammo to include: Hornady 130g ELD-Ms, Prime 130g OTM, FGGM 142g SMK, Gorilla 123g SMK and Gorilla 130g Berger Hybrid. By far, my rifle prefers the H130s, which are loaded to 2.7925 with a BTO of 2.1775 and give you a MV of 2810fps. My opinion is the Prime and FGMM are not the best rounds for this rifle. The Prime is loaded to the edge at 2900fps and despite a 22” barrel, +2 gas system and a heavier buffer, the brass exhibits signs of pressure. The FGMM is worse and I’ve had popper primers in the gasser. I just leave the Prime and FGMM for the bolt gun, and FWIW, I was firing the .260 bolt this weekend (suppressed) and had a popped primer in it with the FGMM (maybe a temp related issue). The Gorilla is loaded lighter for gassers, but it’s not as consistent in my rifle as the H130s. Given I can order factory H130s for $1.17rd delivered, they're a great option.

I’'m working up loads for the LaRue but 41.8g -– 42.2g of H4350 work well with the 130g class of bullets. I'’m working heavier loads with the 147g ELD-M, but 39.7 and 41.2g of H4350 seem to be nodes. It’'s been reported the heavier 140g and 147g class of bullets prefer being pushed about 2600fps in this rifle and my initial firings confirm. I've not loaded a flatline but I think it would be a challenge given the mag's COAL of about 2.870 (and not knowing the BTO for that bullet). I'm focusing on loads for the 147g ELD-Ms and I'm going to try and work some 140g Nosler RDFs, but given the performance of the H130s, I'm not sure how much more I could squeeze from the rifle.

I’'ve shot it suppressed from 100y to 1,000y with no issues. POI shifts but good DOPE had me hitting steel at 1,000 after 5 sighters.

I’'ve probably overachieved a bit with my answer, but if you have a question, ask and I’ll do my best to answer.

Rifle on the 1,000y line at Quantico this past weekend. [IMG2=JSON]{"data-align":"none","data-size":"full","src":"https:\/\/www.AR15.Com\/media\/mediaFiles\/52736\/IMG_5608_JPG-273481.jpg"}[/IMG2]
[IMG2=JSON]{"data-align":"none","data-size":"full","src":"https:\/\/www.AR15.Com\/media\/mediaFiles\/52736\/IMG_5609_JPG-273482.jpg"}[/IMG2]

At 1,000 yards (last weekend) on a 12"x20" 2/3 IPSC type steel target. I can do better, but that day I didn't.

Unsuppressed 5 shot group with the factory H130s: [IMG2=JSON]{"data-align":"none","data-size":"full","src":"https:\/\/www.AR15.Com\/media\/mediaFiles\/52736\/1000_L260_Unsuppressed-273579.jpg"}[/IMG2]

Suppressed 5-shot group with the H130s: [IMG2=JSON]{"data-align":"none","data-size":"full","src":"https:\/\/www.AR15.Com\/media\/mediaFiles\/52736\/1000y_Suppressed_with_TQ-273580.jpg"}[/IMG2]

 

[Defender3]

Forgot to answer your question, the 22" barrel measures 0.750" from the gas block forward.

 

[Z06pilot]

Why do you think barrel length will give you a better SD? That has to do with the load you choose....

I highly doubt you will be able to run flatlines in a 260rem AR10 at any length or speed that makes them worth their money before you run into magazine length restrictions... If I was going to be shooting to 1400yds a Larue OBR wouldnt be my first, second or third choice either.

1. 26" Bolt gun in 6.5cm or 260rem
2. Custom 22" 6.5cm Bartlein/MEGA AR10 (If you are dead set on an AR10)
3. JP 22" 6.5cm AR10 if you want a factory AR10 that shoots

Regarding barrel length and sd, I have had better sd numbers with 24" and 26" barrels on rifles i have had vs 16 and 20" rifles with handloads. I assumed it was due to the burn being more complete in the longer barrels. But perhaps if i had done ladder testing for the shorter barrels, my results would have been different.

I appreciate your rifle suggestions, they are certainly good ones. For me, if i am going to have a 26" bolt gun, i would probably go for 300 norma or 300 win mag. In fact, i think my next rifle will be a 300 norma on a mausingfield action.

I was set to build a 6.5 cm on a mega maten 14" railed reciever set. I liked the switch barrel ability of the predatobr, because i can carry a second barrel in 308 instead of an entire upper. I am hoping to get decent accuracy out of it, if i dont, i will sell it.

Flatline bullets, mabey it was more optomism than i should have had, but after reading the snipershide review were frank mentions that "this bullet like the 160gn 30 cal flatline will work in a semi auto. I think the 2900fps load is about perfect to run in a gasser. This will push this rifle to the next level especially if you want to compete with it." I understand he is talking about a 6.5cm and not a 260, and I wish larue would have made this in a 6.5cm instead of a 260, but am hopfull this will still work. I did contact warner tool, and they said tht their bullets are not jump sensitive like some companys vlds, but we will see.

I really appreciate all of the info provided here especially from defender3! This will be very helpful for narrowing down bullet and ammo choices.

One last thing i have been considering on the 22 vs 18 inch barrel length is stiffness. An article i read by Dan Lilija http://riflebarrels.com/a-look-at-the-rigidity-of-benchrest-barrels/ leads me to believe there is a significant difference between a 22 and 18 inch barrel, although he is looking at much heavier profile barrels.

 

[Defender3]

Regarding barrel length and sd, I have had better sd numbers with 24" and 26" barrels on rifles i have had vs 16 and 20" rifles with handloads. I assumed it was due to the burn being more complete in the longer barrels. But perhaps if i had done ladder testing for the shorter barrels, my results would have been different.

I appreciate your rifle suggestions, they are certainly good ones. For me, if i am going to have a 26" bolt gun, i would probably go for 300 norma or 300 win mag. In fact, i think my next rifle will be a 300 norma on a mausingfield action.

I was set to build a 6.5 cm on a mega maten 14" railed reciever set. I liked the switch barrel ability of the predatobr, because i can carry a second barrel in 308 instead of an entire upper. I am hoping to get decent accuracy out of it, if i dont, i will sell it.

Flatline bullets, mabey it was more optomism than i should have had, but after reading the snipershide review were frank mentions that "this bullet like the 160gn 30 cal flatline will work in a semi auto. I think the 2900fps load is about perfect to run in a gasser. This will push this rifle to the next level especially if you want to compete with it." I understand he is talking about a 6.5cm and not a 260, and I wish larue would have made this in a 6.5cm instead of a 260, but am hopfull this will still work. I did contact warner tool, and they said tht their bullets are not jump sensitive like some companys vlds, but we will see.

I really appreciate all of the info provided here especially from defender3! This will be very helpful for narrowing down bullet and ammo choices.

One last thing i have been considering on the 22 vs 18 inch barrel length is stiffness. An article i read by Dan Lilija http://riflebarrels.com/a-look-at-the-rigidity-of-benchrest-barrels/ leads me to believe there is a significant difference between a 22 and 18 inch barrel, although he is looking at much heavier profile barrels.

You could also read (if you haven't already), about Optimum Barrel Timing and the associated barrel harmonics discussions dealing with barrel whip and timing the bullet as it leaves the barrel. I'm purposely not being more specific as I'll overrun my headlights pretty quickly.