260 Rem/260 AI advice needed

[Hengehold]

I have a 6.5-284 with a 30" bbl and have considered switching to the 260AI if I could match the velocity of a 6.5-284 with a 30" bbl. My understanding at this point is ...

260: velocity=2850fps w/ 140gr bullet, barrel life 1500-2000 rds

260 AI: vel=2950fps w/ 140gr bullet,
Barrel life 1000-1500 rds

Am I close with my understanding of these two cartridges?

-Trevor

 

[ShootDots]

I have a 6.5-284 with a 30" bbl and have considered switching to the 260AI if I could match the velocity of a 6.5-284 with a 30" bbl. My understanding at this point is ...

260: velocity=2850fps w/ 140gr bullet, barrel life 1500-2000 rds

260 AI: vel=2950fps w/ 140gr bullet,
Barrel life 1000-1500 rds

Am I close with my understanding of these two cartridges?

-Trevor

My personal experience with the .260A.I. is I can get 2930f.p.s. out of a 30" barrel with ONLY the Berger 140 LRBT. It has a V-E-R-Y short bearing surface and can attain higher velocities without excessive pressure, using H4350. If you use H4350 and go with a 140 Hybrid, you will be down in the 2850-2870f.p.s. range.. Now if you go to H4831SC or better yet IMR 7828SSC, you can top 2900 f.p.s., using Hybrids, but I have found that neither of them powders can reach my accuracy goals. But in YOUR barrel they might!

 

[MattPeetz]

Use slower powder with longer barrels. I am pushing a 155gr in my AI with 30" barrel at 2805. It is not excessive pressure. Primer pockets in cheap federal brass are still tight after 4 firings.
I am using IMR7977 but will be switching back to H1000. 7977 burns very hot. H1000 burned cooler.
I also have a longer COAL as i single feed but use 4831sc and H1000 in my straight 260 with 32" barrel and get mid 2900's with the 140's in remington brass

 

[taliv]

i have had eleven 260AI barrels on two actions, 9 of which are shot out. I've tried each of these lengths 24" 25.5" 26" 28.5" 29". all rounds fired with a thunderbeast suppressor. never used anything but 140g berger hybrids and VLD. my reamer is .060 fb and .296 nk and i load to mag length on AICS mags, which is short of the lands.

my experience is 1500 rounds of barrel life running "max".

in every case except the 24" (my current barrel which only has about 200 rounds on it) the shorter barrels get HIGHER velocity than the longer barrel before i see pressure signs. 2930 fps was about all i could get out of the 29" barrel. I easily get 3000 fps out of a 25-26" barrel using R17 and am close to that with H4350. i have run as high as 3050 fps on a 26" barrel which definitely was some pressure, but 2980-3000 is comfortable.

after trying 24", all future barrels will be 25 or 25.5"

 

[Sniper338]

I have a 260 Tac that drives berger 140s at 2950 with h4350, 28 inch barrel.

 

[Hengehold]

I have a 260 Tac that drives berger 140s at 2950 with h4350, 28 inch barrel.

Is 260 TAC an improved version of the 260?

 

[Hengehold]

i have had eleven 260AI barrels on two actions, 9 of which are shot out. I've tried each of these lengths 24" 25.5" 26" 28.5" 29". all rounds fired with a thunderbeast suppressor. never used anything but 140g berger hybrids and VLD. my reamer is .060 fb and .296 nk and i load to mag length on AICS mags, which is short of the lands.

my experience is 1500 rounds of barrel life running "max".

in every case except the 24" (my current barrel which only has about 200 rounds on it) the shorter barrels get HIGHER velocity than the longer barrel before i see pressure signs. 2930 fps was about all i could get out of the 29" barrel. I easily get 3000 fps out of a 25-26" barrel using R17 and am close to that with H4350. i have run as high as 3050 fps on a 26" barrel which definitely was some pressure, but 2980-3000 is comfortable.

after trying 24", all future barrels will be 25 or 25.5"

Thanks for the detailed reply.

 

[Alex Wheeler]

I had no problem getting over 3000 fps in a 30" 260ai with 140s and RL22 or Norma MRP. Freebore in the .180" region. Now with the Lapua small primer 308 brass you could get even higher, too bad they all seemed to shoot best at 2850 fps.

 

[Hengehold]

I had no problem getting over 3000 fps in a 30" 260ai with 140s and RL22 or Norma MRP. Freebore in the .180" region. Now with the Lapua small primer 308 brass you could get even higher, too bad they all seemed to shoot best at 2850 fps.

My understanding of the 6.5-284 is that there is an accuracy node that usually falls around the 2950 range with the 140gr class bullets. Is that not the case for the 260AI?

I wonder why the accuracy node would be different?

 

[alphapygmy]

I had no problem getting over 3000 fps in a 30" 260ai with 140s and RL22 or Norma MRP. Freebore in the .180" region. Now with the Lapua small primer 308 brass you could get even higher, too bad they all seemed to shoot best at 2850 fps.

+1. I got mine in the 3100 region with Palma brass, RL17 and 140 Berger LRBT. I shoot a local summer 600 yard league and won my class shooting the LRBT and 142 SMK around 2850, way under max for both bullets.

 

[Hengehold]

+1. I got mine in the 3100 region with Palma brass, RL17 and 140 Berger LRBT. I shoot a local summer 600 yard league and won my class shooting the LRBT and 142 SMK around 2850, way under max for both bullets.

You did not find a node in the 2950 range?

 

[alphapygmy]

My understanding of the 6.5-284 is that there is an accuracy node that usually falls around the 2950 range with the 140gr class bullets. Is that not the case for the 260AI?

I wonder why the accuracy node would be different?

I could only get to about 2910 with H4831SC and it shot better at 2850 anyway. With the RL17 I could get there but accuracy wasn't as good and I occasionally had a flyer that I didn't seem to get with H4831SC. Never tried H4350, couldn't get any at the time. I have a new 260AI I'm going to try and get the 130 Berger AR Hybrid to 2950 and work around there and see what happens.

 

[daj]

berger 140s at 2950 with h4350, 28 inch barrel.

Ditto.

 

[bheadboy]

my personal experience with the 260 was a "forget it" and I did, went with the 7-80AI went over 3000 with 140s and 2900 with 150's out of a 24" bbl. if you question accuracy, don't, it will shoot very tight as other have found - bbl life is very good
Bob

 

[Alex Wheeler]

You did not find a node in the 2950 range?

Yes, but the 2850 node was better. I wold look at a 6.5 saum if you want a hot 6.5mm. I ould also take te260ai over the 6.5x284 for the efficacy.

 

[taliv]

i never had any accuracy issues necking up 243 brass from lapua, hornady and RP. why did you guys choose to neck 308 down? to get smaller primer pockets?

 

[DennisH]

i never had any accuracy issues necking up 243 brass from lapua, hornady and RP. why did you guys choose to neck 308 down? to get smaller primer pockets?

I am interested in seeing opinions on this as well.

 

[alphapygmy]

i never had any accuracy issues necking up 243 brass from lapua, hornady and RP. why did you guys choose to neck 308 down? to get smaller primer pockets?

Couple reasons I chose Palma 308. 1- The small primer pocket stays tight longer and is a generally stronger case. 2-Since the necks are too thick after sizing down to .264 I have to turn the necks down and can get a nice fit in the chamber and very even consistent neck tension. I do mine in batches of 52, 50 to shoot and 2 for spares if something doesn't form right or I mess one up. If you don't shoot crazy pressures 50 will last a long time. I have a batch that has 10 firings and the pockets are still tight running 140's around 2850 fps.
In my opinion a down side is they don't show over pressure as soon as large primer brass so when they do you're probably way over max. Use a chrono and common sense when working loads up.

 

[thomasholbrook43]

Well I agree with shootdots. Tried H4831sc,imr7828ssc. They both got me up there into the 2950 range out of 28" Krieger 8 twist. But in the end of testing H-4350 prevailed. Accuracy could not be matched. My velocities are high 2800 range and fireforming brass in match shooting a pair of 199/12X &199/9x is hard to beat. Once fire formed these 260AI are hard t o beat for shear accuracy.2850-2870fps seems to be the node.

 

[Evlshnngns]

Hengehold, What did you end up with?