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260 AI load

shepherm

I built a 260 AI awhile back and I've just recently started working up a load. The reamer I used was PTG #165154 6.5MM-308 Win AI

I'm using:
Federal match primers
260 Lapua brass (COW formed)
139 OTM Scenar
COL 2.815

I've tried both H4831SC and H4350. It looks like my gun likes H4350 a little more.

43 gr of H4350 produces 2926-45 ft/s with very light extractor mark
43.5 has produces 2953-86 ft/s with a more noticeable extractor mark and heavier bolt lift

I'm seeing where there are a many people shooting the standard 260 rem with 43grs H4350??
So, I have a couple questions. First, how is the standard 260 shooting 43 grs, longer throats? I'm not sure how much freebore a have but I'm guessing not much.. Should I consider extending the freebore?

Thanks for all your advise
Mark
 
shepherm said:
I built a 260 AI awhile back and I've just recently started working up a load. The reamer I used was PTG #165154 6.5MM-308 Win AI

I'm using:
Federal match primers
260 Lapua brass (COW formed)
139 OTM Scenar
COL 2.815

I've tried both H4831SC and H4350. It looks like my gun likes H4350 a little more.

43 gr of H4350 produces 2926-45 ft/s with very light extractor mark
43.5 has produces 2953-86 ft/s with a more noticeable extractor mark and heavier bolt lift

I'm seeing where there are a many people shooting the standard 260 rem with 43grs H4350??
So, I have a couple questions. First, how is the standard 260 shooting 43 grs, longer throats? I'm not sure how much freebore a have but I'm guessing not much.. Should I consider extending the freebore?

Thanks for all your advise
Mark
Click to expand...
The best powder I found was Norma MRP with 140 GR bullets . RL 22 was good also.
Larry
 
shepherm said:
I built a 260 AI awhile back and I've just recently started working up a load. The reamer I used was PTG #165154 6.5MM-308 Win AI

I'm using:
Federal match primers
260 Lapua brass (COW formed)
139 OTM Scenar
COL 2.815

I've tried both H4831SC and H4350. It looks like my gun likes H4350 a little more.

43 gr of H4350 produces 2926-45 ft/s with very light extractor mark
43.5 has produces 2953-86 ft/s with a more noticeable extractor mark and heavier bolt lift

I'm seeing where there are a many people shooting the standard 260 rem with 43grs H4350??
So, I have a couple questions. First, how is the standard 260 shooting 43 grs, longer throats? I'm not sure how much freebore a have but I'm guessing not much.. Should I consider extending the freebore?

Thanks for all your advise
Mark
Click to expand...
With the 140 class bullets, you will need a .165-.170 freebore to adequately handle the longer bearing surfaces. H4350 is or I should say probably is the best powder for that cartridge. H4831SC is also very good. My current load is 43.2grs of H4350 with the Berger 140 Hybrid.. I was shooting the Berger 140 LRBT. It is a FANTASTIC bullet. It has a very short bearing surface and can be easily driven to 2900+ IF you have the longer freebore. If you want to shoot a 140 class bullet, you may want to try one with a shorter freebore. The Berger 140LRBT may very well be the ticket you're looking for. It is extremely easy to tune and VERY accurate. I have never seen a 6.5 cartridge that would not shoot that bullet well.. My "problem" is that I have a .170 freebore and after 800 rounds, the 140LRBT was barely in the case, due to it's short bearing surface, ergo I had to go to the Hybrid.. I was running 43.8grs of H4350 @ 2920f.p.s. with that bullet. So, instead of paying for the use of a unithroater, try the 140LRBT! You may be pleasantly surprised!
 
Last edited:
savagedasher said:
I loaded 47 GR of MRP and never had that problem. Primers stated to show near high pressure. That was with jamming bullets . Jumping I shot 48 GR. Larry
Click to expand...
I have NO doubt! Norma MRP, if it is not RL-22, it has virtually the same burn rate, which is MUCH slower than H4350. Norma MRP is right on top of IMR 7828.. So you could have probably done 48.0grs with no pressure issues..
 
ShootDots said:
I have NO doubt! Norma MRP, if it is not RL-22, it has virtually the same burn rate, which is MUCH slower than H4350. Norma MRP is right on top of IMR 7828.. So you could have probably done 48.0grs with no pressure issues..
Click to expand...
I would have to go several years back in my book to give powders and loads . But nothing beat MRP for me . Larry
 
savagedasher said:
I would have to go several years back in my book to give powders and loads . But nothing beat MRP for me . Larry
Click to expand...
It is an excellent powder. I would have no compunction about using it for hunting. However, in long shot strings and near 100 rounds in an F-Open match, I will stick with H4350. MRP is rather dirty and temp sensitive>>>not a good recipe for for an F-Open match.. But for hunting>>it would be tough to beat!
 
ShootDots said:
It is an excellent powder. I would have no compunction about using it for hunting. However, in long shot strings and near 100 rounds in an F-Open match, I will stick with H4350. MRP is rather dirty and temp sensitive>>>not a good recipe for for an F-Open match.. But for hunting>>it would be tough to beat!
Click to expand...
I never shot H4350 . Back then it was all about speed . I can say the 260 AI won most. I shoot H4350 I my Dasher. Nothing I have tried shoots better. Larry
 
savagedasher said:
I never shot H4350 . Back then it was all about speed . I can say the 260 AI won most. I shoot H4350 I my Dasher. Nothing I have tried shoots better. Larry
Click to expand...
I am in the process of developing a load with H4350 in my Dasher. So far, it looks to have some real promise! I will give it a good run.. Hopefully, it will do what I hope for. If not, I will go back to Varget and or VV N540..
 
ShootDots said:
I am in the process of developing a load with H4350 in my Dasher. So far, it looks to have some real promise! I will give it a good run.. Hopefully, it will do what I hope for. If not, I will go back to Varget and or VV N540..
Click to expand...
What bullet are you shooting? Larry in thd dasher
 
OP, your COAL is much shorter than most of us are running with that combo. I used to run the 139 scenar in my 260 w/H4350, but my COAL was 2.94". In my TRG mags, that length was not an issue. I don't know exactly what my freebore was (new barrel now), but it was in the .170-.180" range. Sounds like you have a much shorter freebore, which will limit your COAL, and by default your capacity.
 
I believe ShootDots and FTR both answered your question. When you have short freebore it uses up capacity. The pressure goes up quicker then when it is longer. Kind of like comparing an Ackley to a regular case. The Ackley can usually shoot more because it has more capacity. Matt
 
My current .260AI barrel on my savage is a McGoowan prefit 8 twist varmint contour at 26". My preferred load is 42.0gr of H4350 with a Berger 140 VLD running at 2940 according to my Chrony which also corresponds really well with actual drop data. My previous barrel which was the same setup only a Criterion preferred 44.0gr of H4350 with basically identical speed numbers. My C.B.T.O. on my current barrel is 2.120" at .025" jump, so that puts me at roughly 2.841" OAL according to Bergers measurements. I am running Lapua brass and at 42.0gr I am also seeing very slight ejector marks and it shoots lights out being very capable of 1/4 moa accuracy if I do my part. Long story short, who cares if you are using less powder as long as the velocity and accuracy are there.
 
I assume you are jumping the bullet because you get better accuracy. Some of my VLD's shoot a little better slightly in the rifling. What freebore are you running?


Bill
 
STOMP442 said:
My current .260AI barrel on my savage is a McGoowan prefit 8 twist varmint contour at 26". My preferred load is 42.0gr of H4350 with a Berger 140 VLD running at 2940 according to my Chrony which also corresponds really well with actual drop data. My previous barrel which was the same setup only a Criterion preferred 44.0gr of H4350 with basically identical speed numbers. My C.B.T.O. on my current barrel is 2.120" at .025" jump, so that puts me at roughly 2.841" OAL according to Bergers measurements. I am running Lapua brass and at 42.0gr I am also seeing very slight ejector marks and it shoots lights out being very capable of 1/4 moa accuracy if I do my part. Long story short, who cares if you are using less powder as long as the velocity and accuracy are there.
Click to expand...
It seems you have a big difference between the Base to ogive and OAL measurement. .721 is a big difference. That is almost 3/4 inch. Matt
 
I have no idea what the free bore is. The barrel was simply a prefit that was in stock when I ordered it so whatever standard Macgowen is using is what I have.

.721 is what Berger lists for nose length on their quick reference sheet, so I simply added that number to my ogive measurement. I am stuck at work so I can't give my actual OAL.

Yes I am jumping because I achieved better accuracy at that seating depth vs jammed into the lands. In fact, all but one of my rifles prefers about a .025" jump as opposed to running in the lands. My wifes 6BR with 105 VLDs prefers to just touch the lands.
 
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