If you were ordering a 260 AI barrel.......

[Gollum]

Thinking hard about ordering a 260AI barrel from Pac-Nor, for 2-3-500 yard target shooting, maybe beyond.

Lapua 139 Scenars seem to be the bullet in vogue for them right now, what would be the ideal twist, and land configuration?


what they offer:

6.5mm,.264")
3 groove 8" 8.50" 9" 10"
4 groove 7" 8.60" 11"
5 groove 8" 9" 12"
6 groove 10"
Polygonal 8" 8.50" 9"

 

[2644ever]

Get the 3 groove supermatch stainless with a 8" twist, you'll never regret your purchase. Get it at least 27" long.Be very careful with barrel break-in, follow Pac Nor's instructions and shoot moly plated Scenars.

 

[techshooter]

I just fitted and broke in a Bartlien's 5R, 8.5" twist, 30", 1.25" straight cylinder contour, chambered in 206AI, on my switch barrel rig. Look here for lots more information:

http://www.the-long-family.com/260AI.htm

This barrel is essentially perfect. It was nearly perfectly straight, and the borescope and slugging told me that the bore was perfectly lapped. I got zero copper fouling after a string of 90 rounds yesterday. It is shooting under 0.5" with everything that I put through it. Great service and quality from Bartlien's - you can't go wrong.

I found that the Berger 130 grain VLDs shot very, very well, much better than the 123 Lapua Scenars, or the 142 SMKs. Moly seems to help in all the 6.5mm chamberings that I have used.

Cheers,

 

[Forum Boss]

Chris,

Great report on the .260 AI. I also had major doughnut issues with necking up .243 brass to .260 Rem standard. Even when I could seat bullet of choice,123 Scenar), the thickness at base of neck was messing up neck tension and smooth seating. I tried a K&M "doughnut cutter" mandrel and that helped but still wasn't a complete solution.

The best thing I found,and Ken of K&M helped with this), was to FL size the case,base to mouth--not just a body sizer) with a non-bushing full-length die. THEN run your expander mandrel in but IMPORTANT-- halt the expander BEFORE you get the doughnut. Then go in with the neck-turner mandrel with the cutter tip.

After all this is done, shoot the case and then neck-turn them. You'll find more brass build-up at the neck shoulder junction, so set the cutter to just clean up the bottom 30% of the neck.

On your .260 AI load, I think you'll see ES/SD go down with H4350. Also, I couldn't tell from your article whether you were seating into the rifling--there was a mention of .010" out from lands. Anyway, try the 130s .015" into the lands,past point of first contact with Stoney Pt) if you haven't already. Also, try a load at 3050 and 3120. These are known vels where these bullets seem to like to run,at least in other barrels).

I'm surprised your 123 Scenars didn't measure out so well. Mine were really, really consistent--but they were produced three years ago.

Also, when you get the brass really optimized I think the ES will go way down. I don't envy you the task. It's a lot of work when compared to just shooting a 6.5x47 or 6.5-284. Good news is Winchester is supposed to be making .260 Rem brass for Black Hills soon.

 

[Forum Boss]

Gollom

In the PacNor, I'd also recommend the 3-groove SuperMatch, 27-28", about .90-.92 at muzzle. I'm not a fan of moly so that's up to you.

Break-in on my PacNor was super-easy. Try patches only, or just a nylon brush. Don't get real aggressive--they'll have done a good job lapping that thing. I've never put a brush in my PacNor barrel, and it has never copper fouled with anything running under 3100 fps.

 

[rhino]

I would think that the .260 AI running 139's would run at 2950 in a 30 inch tube easily. Your basically only a Skotch behind my Swede in case capacity.

OBT in my opinion means F*c*ing shit! I tried it and it never aligned for me in my swede. Shoot and chrono your loads. That way you can measure and have numbers to back up the loads.

I have just ordered a 6.5 30 inch Bartlein in 1-8.5 twist 5 R profile. Its going on my WTC RIFLE and chambering will be the 6.5x55 swede.

RHINOUT!

 

[montanaearl]

chris, i am really interested in your project. i have a bartlein 6.5mm, 5R, 8.5 twist barrel coming that will also be chambered for 260AI,actually with a 6.5-08AI JGS reamer). your comment on throat length would be most appreciated. the print for my reamer shows 0.050 freebore, and as i plan to get to the 140s, it seems short. to what dimension did you throat your chamber? i also had the same experience with availability of R-P 260Rem brass and ordered the 243win lapua. your comments on prep are also most appreciated.

 

[techshooter]

Montanaearl:

If you poke around on my web site, I have the chamber prints for all my more interesting rifles posted, including the 260AI. Look under the "Projects" button. This reamer is from Dave Kiff at PTG, and it also has a very short throat. I used a 6.5mm 1.5 degree throater to set the throat length for the 123 to 130 grain VLDs. The 142s work as well, as I set the length for them as a worst case.

Here is what I measured on the chamber right after reaming. The dimensions are from the base of a case to the bullet ogive, as measured with a Stoney Point 25 caliber bullet comparator. This dimension is where the bullet is hard into the lands, and will not go farther without a lot of force. I always use this as my reference point, as it is very easy for me to consistently measure this depth, where a "just touching" point is very hard for me to get consistently. Either way, the data below will tell you how much I had to extend the throat after the chamber reaming:

As Reamed:
Case Base to Ogive for 123 Lapua Scenar: 2.250"
Case Base to Ogive for 142 Sierra MatchKing: 2.253"

To keep the 142 SMK out of the Donut region of the case neck, the Case Base to Ogive length needs to be 2.435"

Therefore, the throat needs to be deepened by 2.435"-2.253"=0.182"

After Deepening Throat:
Case Base to Ogive for 123 Lapua Scenar: 2.429"
Case Base to Ogive for 142 Sierra MatchKing: 2.430"

I hit the desired length less 0.005" I stopped there as I expect this throat to erode. :thumb:

I know that most professional smiths would not want to take the time to do a separate throating operation, but for me, I really like the flexibility of setting any throat length, using the same chamber reamer. My time is irrelevant, as I like the process of building as much as the shooting.

I just ordered 500 Remington 260 brass from Midway. They were in stock as of last night. I decided that the hassle of getting rid of the donuts with the Lapua is more than overcome with the low cost of the Remington brass, which allows me to sort by neck thickness, and toss any that have more than 0.0015" variation. My first set of Remington brass is still going strong, and shoots very well. In fact, the Remington brass has a bit more case capacity:

Lapua .243 fireformed: 55.9 grains H2O
260 Rem. fireformed: 57.4 grains H2O

With the Rem. Brass, just sort by case wall thickness if you have a mind to, clean up the primer pockets, de-burr the inside of the flash hole, size the necks, inside chamfer the neck with a 14 degree VLD tool, and you are good to go. Your smith should set the headspace so that the brass has a slight crush when chambering unfired brass,about 0.004"). I never depend on the bullet tension to hold the case in place for this first firing. I use GM215M primers. Ramshot Hunter has been the primary, but H4350 is on the list as well. I wanted to try the ball powder, and so far, I am very pleased with it. It is very clean, even cleaner than the H4350 in my 6.5-284. The ES and SD are good as well. There may be better,H4350 is my bet for the next best candidate), but how much is not yet known.

Hope that this helps. Let me know if I can answer any more questions. I am really pleased with this caliber so far. It is my main candidate for a 1500+ yard prairie dog hit this coming May.

Cheers,

 

[techshooter]

Moderator:

I sort of replied to your question regarding how I defined seating depth in my post above. I use hard jammed in as "zero", as I can measure that most consistently. Therefore, if there is about 0.020" to 0.030" between "just touching" and "hard in", the bullets are somewhere between 0.010" and 0.020" into the lands by the "just touching" reference. I have definitely observed that all my "match" chamberings need to have the VLDs seated into the lands. I have found that if the bullet is set right at the zero "hard in" point, erratic shot start pressures are observed with the PressureTrace instrument. I suspect that there are subtle interactions between the initial bullet movement and the powder burn ramp up. Something is different, as if the bullet is backed off even 0.005" from this point, it all goes away.

Cheers,

 

[mysticplayer]

If interested, you can read my thoughts on the 6.5 Mystic which is my version of the 260AI in the Gun of the Week #75.

I really like this wildcat and have had excellent results using H4831SC, CCI BR2, 139Lapua's uncoated,will try moly this spring) and necked down 308 Win brass.

I am shooting two 30" Gaillard barrels with 8 twists. Both shoot very well with one, extremely well. The rifles showed a distinct preference for the Lapua bullet over Hornady and Sierra.

H4831SC gave me better load density and LR accuracy over the H4350. Velocities were very similar at 2900fps. I can go to 2950ps but accuracy slips just a bit. Max velocity was a smidge over 3000fps but brass life was poor.

OAL length is 2.90" as an average measured to the tip of the cartridge. Throat life has been very good so far.

I used a Manson Throater 1.5 deg. to lengthen the orig chamber to fit the cartridge to 2.90". Throat wear now has the bullet moving a few thou before engraving. I found that seating on the lands didn't work for my rifles.

I really like forming my brass from 308 Win. After fireforming and neck turning, the case life has been superb. All the neck sizing is done with a 260Rem Lee collet neck die with a spacer. I am now using a 7-08AI body die from Redding to bump the shoulder.

I am able to fit the brass to the chamber so sizing is minimal. I am playing with annealing and I think this will really help make the neck tension more consistent. Still working on my technique but shows promise.

Good luck with your project.

Jerry

 

[montanaearl]

chris, thanks very much for the data, after posting this i will go to your site for the print. however, with my very crude measurements, I had calculated needing 0.221 additional freebore. i was using the 140JLK bullet data, and assuming a starting point of 0.050 clearance from neck-shoulder junction to boattail-bearing surface junction, which if decreased to 0.030 puts my calcs very close to your findings. what i am trying to do is save a little time by having my chamber throated deeper initially and minimize trips to the gunsmith, so this information is very valuable. looking to me like throating an additional 0.185 might be the place to start.

 

[montanaearl]

chris, I match up the prints,PT&G vs. JGS) and they are almost identical, excepting the JGS has 0.004 more neck,less case length) which i suppose will translate into slightly less case capacity. finally, when looking at bullets, I had pick the 140JLK, the 140Berger and 139Scenars from standpoint of highest BC to start. I am curious as to your thinking when starting with the 130s. Thanks again for the help.

 

[techshooter]

Montanaearl:

I was looking at the end game at 1500 yards: I wanted supersonic velocities at that distance. I had trouble getting that with the 142SMK at 2900, it was borderline. The 140 Berger VLD at 2950 has the same velocity at 1500 yards as the 130 Berger VLD at 3050. Both beat the 123 Lapua Scenar at 3115 FPS.

I started with the 123s hoping to get ~3200, and achieved that, but the accuracy was best at about 3115 or so. I have yet to push them to the next higher node, as I was running out of daylight this last trip to the range. 3170 was pretty hot. I have not yet tried any other powder except Ramshot Hunter. I have both H4831SC and H4350 on hand, those are next.

I had ordered some 130 Bergers and had them on hand, so I tried those, and found the accuracy to be excellent. I might be able to get them to about 3050 to 3070 with good accuracy, or even higher, but time will tell. If they can get to about 3150, then they are better than the 140s at 3000. It's all a matter of when you reach the fastest accurate node for a given bullet weight relative to the maximum case pressure. Sometimes a little drop in the bullet weight can let you get to the next higher node, and beat out the heavier bullet in the same rifle.

Given the fact that I can get 2950 with the 142 SMKs while fireforming, I am confident that I can get the 140 Bergers up to about 3000 without much trouble. I have to order some and give them a try.

Either way, the 130s and the 140s will get me to the supersonic at 1500+ yard goal.

Cheers,

Chris

 

[montanaearl]

thanks again chris, now i understand.

jerry, i've seen your post before and forgot to ask about the lee die. where exactly is the spacer you refer to?

 

[montanaearl]

just when i thought i was out of questions i was wondering how you got to the 215 primers rather than 210s or other non-mag?

 

[mysticplayer]

scan down the article and you see a pic with a Lee press. It should change through three or more images,doesn't work on some internet viewers). You are looking for the washer that is on the shellholder.

Super high tech aerospace design!!!!!

Or just get an approx 1/8" thick big steel washer with 1/2" hole from your local hardware store.

That washer activates the dies collet so it sizes the case sooner,higher up the neck). You could also just get a custom collet die set made by Lee for $50 but I had the 260R dies handy.

Jerry

 

[montanaearl]

jerry thanks. when i first looked at the article, my viewer did not show the closeup, now it does, so i can see the washer-spacer clearly. couple of questions i should have asked before. first, you say you use the 7mmBR FL die on the first,partial) neck pass. Is this a bushing die, and it doesn't seem like it would make any difference if it were a neck die? secnd, and more important, i would be interested in your reamer dimensions, particularly the throat. in his 260AI article, terry cross said he had not throated and was running 2.82" with the 139Scenars. Your 2.90" would indicate 0.080" more depth from the standard,JGS and PT&G prints) of 0.50" freebore for a total length of 0.130". does that sound about right?

Interestingly however, is his report of using 48.5gr H4831 or H4931SC in competition loads.

as you can see from my above posts, i am trying to get to as good a throat length as possible for the 140s on the first, and hopefully only, trip to the smith.

 

[mysticplayer]

Don't use any bushing dies. I prefer the collet neck sizer.

I do use a 7BR FL sizing die to form the secondary shoulder. I just set up the die to form the neck in the right spot when the press lever is at full down. Sizes in one pass.

I throat in a second step to adjust for the bullets used. I seat the bullet so that where the boattail joins the bullet body is at the case neck shoulder junction. This gives me the max case capacity and the highest amount of neck holding length.

I can then seat the bullet further out to chase the throat as it erodes.

The easiest way to help your smith is to send him a necked down case with a seated bullet at the OAL you want. Just ask him to throat so that the bullet engraves the lands.

Now you back off the bullet a smidge and go for it. Some bullets like to be seated on the lands, some off. This way you have the best of both worlds.

That loads sounds really hot compared to my loads but then lots do vary quite a bit.

Use any 40deg 260AI reamer you want. You will be changing the throat in the second step. I prefer a 1.5deg throater. The shallower the better.

Jerry

 

[techshooter]

Montanaearl:

I did a study a while back comparing mag vs. non-mag primers in my 6mm-22/250AI. You can see that here:

http://www.the-long-family.com/primer_study.htm

I have tried going back, but always seem to get the best performance with the 215Ms in the larger cases with slower powders,6.5-284 especially).

Hope that that helps.

Cheers,

 

[montanaearl]

chris, a fascinating article. so using the 215s was not a flight of intuitive genius but curiosity and carfeul experimentation. i suspect trying the 215s could be useful in any gun that is displaying some of the symptoms you describe. i tried comparing the cci400s vs. the cci450s in my 19 Badger last year but did not finish as prairie dog season interrupted my experimentation. I'll go back to where i left off.