Thread: AR2209 Lot Variations in the 6.5 x 55.

Originally Posted by Flyblown

However the new batch was laser accurate in both rifles so I got in touch with Rob at Workshop Innovations and he organised me a bulk shipment all from the same (new) lot, which will last me a good while. I now also use it in 6mm Creedmoor.

Funny that you say that.
Had exactly the same experience with the new batch of AR2209 - and the already accurate 6.5CM got even better:



What I can't get me head around is that the old, most accurate load was 40gr and so is the new one. I would have expected being around 100fps faster, to drop powder to get to the same speed and back into the old node for accuracy again. Or did I just find a new node by fluke?

Interesting thread and well suited to a campfire and beers. I have oft puzzled over poi changes between okd and new loads. I've decided that such things as slight changes in neck tension due to ageing brass or different brass lots or numbrr of times reloaded, primet batches. and seating depth are all potential factors. I have for instance measured up yo 5 thou" chsnge in seating depth simply between v cold winter temps and hot summer temps affecting expansion of the press itself. I have also measured differences in bullet dimensions like length, base to ogive, ogive to point, cannelure position between batches of same brand. Even weight variances within and outside lots. Nowdays I try to mitigate these variances by various simple means , often "dead reckoning" and then accept that a couple of medium range foulers to check zero before a serious hunting trip are a good idea. Of course, at a range comp you have two sighters anyway, and there are good basic reasons for that allowance.

Had significant velocity changes with different lots of 2206H and 2208. No trouble with 2209 so far.

Even with ADI powders you need to make sure you're ruling out extreme temperature variation in the powder. I get at least 50fs faster in summer vs the coldest days of winter. Maybe even 100fts.

Originally Posted by Dead is better

Even with ADI powders you need to make sure you're ruling out extreme temperature variation in the powder. I get at least 50fs faster in summer vs the coldest days of winter. Maybe even 100fts.

H4350 aka AR2209 has a 0.29fps increase per degree F.
I don't do F so in Celsius lets say in winter you go hunting at 0 Celsius and in summer you go out in 40 Celsius, the increase in speed will be 19fps

Source


In terms of the 6.5 x 55 it will mean you will go from -46in to -45.3in drop at 500m with the 120gr GMX bullet.

[QUOTE=JaSa;984132]H4350 aka AR2209 has a 0.29fps increase per degree F.
I don't do F so in Celsius lets say in winter you go hunting at 0 Celsius and in summer you go out in 40 Celsius, the increase in speed will be 19fps

Source

In terms of the 6.5 x 55 it will mean you will go from -46in to -45.3in drop at 500m with the 120gr GMX




Ok i get your point re seasonal variation probably not being greater than say 20. But i do shoot in strings in 12deg and then get my chamber/barrel too hot to touch so im assuming thats going from 12deg c up to + 50c or hotter. At 800m that is amounting to something of a substantial shift in MV. Given that change in MV i have witnessed over a chrony (and not a keyboard) might be the barrel / expansion / altered distance to lands i dont know. Always assumed it was the temp of the powder baking away in the chamber if i left it too long to shoot after a string.

Originally Posted by grandpamac

Greetings All,
A few months back I was developing some new loads for my 6.5 T3 and found some significant differences in burning speed between the current production and an earlier lot of AR2209. Sorting through some old loads some were found that contained AR2209 from an even earlier lot. It seemed a good opportunity to chronograph the three lots of powder with other variances eliminated as far as possible. I found the results interesting hence this post.

The three lots of powder were purchased in 1,993, called original, about 2,000, called old and 2,019, called new. Two different projectiles were tested, 120 grain Sierra flat base and 129 grain Hornady SST. The 120 grain projectiles were loaded in once fired Norma cases with Winchester W120 primers. These cases came from loads assembled in 1997 which were broken down to provide the powder. The cases, originally full length sized, were neck sized to restore neck tension. The 129 grain projectiles were loaded in new Lapua cases with Federal 210 primers. The shooting was done yesterday in cool overcast but breezy conditions at 60 metres. Mid chronograph screen was 3.0 metres from the bench. Loads for the 129 grain old and new lot powder were fired previously.

Velocities recorded are as follows:
120 grain projectiles 46 grains AR2209. Original lot 2,806 fps. Old Lot 2,798 fps. New lot 2,870 fps.
129 grain projectiles 45.5 grains AR2209. Original lot 2,763 fps. Old lot 2,720 fps. New lot 2805 fps.

The powder loads were max form the Hodgdon on line data which is limited to 46,000 CUP. The old lot of powder produced velocities close to Hodgdons. The new powder velocities are closer to the Nosler on line data. Nosler seems to have reduced the loads for their 129-130 grain data perhaps due to some harder projectiles in that range.

Results: There is a little less than 100 fps difference between the fastest and slowest lots of powder, equivalent to adding roughly 1.5 grains of powder in this case. A powder load adjustment would be needed with close to max loads. All loads other than the 120 grain new powder loads went into a 17 mm group with individual loads moving around in this group, a little less than 1 MoA. The errant loads went about 5 mm high.

Conclusions: Yes we do need to make adjustments when a new lot of powder is started but we shouldn't need to work up from start loads if you have a chronograph. Checking a start load of each lot of powder over the chronograph should tell you if the lots are similar or not. Adjustments can then be made. Velocity is the best measure of pressure we have as hand loaders.
Regards Grandpamac.

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