Velocity/Powder question

Hello Reloading Gurus,

I am working on reloading for a 280 Ackley Improved Kimber Mountain Ascent rifle which is 24" barrel and twist rate of 9 - with a DPT Suppressor.

I am using Hornady 139SST 7mm projectiles and Nosler brass. I am using AR2209 powder and note that if I use 140gr projectiles, the starting load is 52.2grains @ 2,895fps and the max is 55.5grains @ 3,010fps.

I am using 54.5 grains AR2209 and expected (guessed as 139SST projectile isnt listed so went for 140gr) the velocity to be between 2900 and 3000fps with the 139gr SST projectile.

I tested with a chronograph yesterday and found out of 12 shots, the high was 2845fps, Low was 2775fps with 2820fps being the average. This was allot lower than I expected.

Just wondered if this velocity should be allot higher that what it actually was and if there is anything I should be looking for? Or is this normal and I shouldn't be concerned?

Cheers Alan

I have found alot of times published speeds have been 100 odd fps faster than what my chrono has said, also if the barrel is new it should gain abit of speed after 150 odd rounds down it

Firstly - dont believe all that is written in books re velocity, often it is close, but sometimes it aint. Secondly - your crony may not be exact, many aren't, but they are close. It gives you a ball park figure to start with and then use another source to verify your speeds. Such as shooting your chosen load at 400-600 metres and recording the actual drop. A 139SSt at 2820 is certainly gonna drop an animal no problem. If you want to chase speed, then Superformance seems to add another 100-200fps to a number of cartridges based on the 270/30-06 parent case.

You can certainly beat that speed with other powders I’m not familiar with 2209 though but all at the same time theirs nothing wrong with that speed either , id be looking to tighten up the ES depending on your use for the load though

I would recommend slower powders and heavier pills to get the best from your 280ai.
I found VHT N560 gave best results with 162 AMAX at 2980 fps from 24in bbl 1:8.7 twist. ADI 2217 is worth trying and so is RL26 - LOL, if you could get it. Was originally running AMAXs with RL22, very accurate but about 100fps slower than N560. RL23 is also worth a look. For 150gn Scirrocco pills I’m running 2213SC powder, very accurate load but haven’t chronied this load as I use it for bush load out to 200-250 yards. It will be somewhere around 2900fps which is plenty.
I’d be wary of pushing the 139SSts too fast, they are very frangible & have been known to grenade up close even in the humble 7-08. At 280ai speeds I’d personally not use these on big reds or anything up close where you are shoulder shooting.

H4350 is same as 2209. Below is 139gn. Reloading tables are guides only, hence reduce loads and work up with caution. Tight barrels and/or tight chamber and vice versa determine your rifle's performance.

Kimber chambers are typically tight. Your one may not be...but according to the Hornady table you're not a mile out.

A slower powder might be better...just checking your barrel is 24" cos the Kimber has a funny factory thread that won't take a DPT unless an adapter fitted. Might be 22"?!https://uploads.tapatalk-cdn.com/202...6701a7f401.jpg

Sent from my SM-G998B using Tapatalk

Quote:

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Originally Posted by Tikka7mm08

H4350 is same as 2209. Below is 139gn. Reloading tables are guides only, hence reduce loads and work up with caution. Tight barrels and/or tight chamber and vice versa determine your rifle's performance.

Kimber chambers are typically tight. Your one may not be...but according to the Hornady table you're not a mile out.

A slower powder might be better...just checking your barrel is 24" cos the Kimber has a funny factory thread that won't take a DPT unless an adapter fitted. Might be 22"?!https://uploads.tapatalk-cdn.com/202...6701a7f401.jpg

Sent from my SM-G998B using Tapatalk

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Cheers, yeah looking at your chart your are right not too far off and it could be any factor with the rifle (still newish - 30ish rounds). For my DPT suppressor I had to get an adapter from NZ Asia which sorted that side, so still 24".

Quote:

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Originally Posted by chainsaw

I would recommend slower powders and heavier pills to get the best from your 280ai.
I found VHT N560 gave best results with 162 AMAX at 2980 fps from 24in bbl 1:8.7 twist. ADI 2217 is worth trying and so is RL26 - LOL, if you could get it. Was originally running AMAXs with RL22, very accurate but about 100fps slower than N560. RL23 is also worth a look. For 150gn Scirrocco pills I’m running 2213SC powder, very accurate load but haven’t chronied this load as I use it for bush load out to 200-250 yards. It will be somewhere around 2900fps which is plenty.
I’d be wary of pushing the 139SSts too fast, they are very frangible & have been known to grenade up close even in the humble 7-08. At 280ai speeds I’d personally not use these on big reds or anything up close where you are shoulder shooting.

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Cheers - Im happy with the grouping with this load seems to work well for me - as it happened I had the bits and pieces to make this recipe work (powder etc). Yeah I also use the 139sst in my 7-08 and have done for years - has been my go to with all NZ game, does the job well. I think with this speed in the 280ai should be ok.

Greetings @alanimal,
The components that go into a handload all vary as do the rifles that they are fired in. Generally data for pressure tested loads will show similar top velocities but sometimes with different charges of powder and this is what is shown by the two data sets quoted. Both top out at around 3,000 fps in velocity but the Hornady takes about 1.5 grains more powder to get there. Your rifle seems to need a bit more still. Some older lots of AR2209 were quite a bit slower than current production so take care if you move on to them. This is not unusual with a factory rifles compared to pressure barrels. Your rifle is also new so any extensive load development should be left until the barrel is run in. You are happy with the load so need to change nothing but you could work up to the Hodgdon/ ADI max should you feel so inclined. It is now spring so go shoot some stuff with it and think again about your next step in early winter.
Regards Grandpamac.

My Ackley happily runs way over listed book max with -no- pressure signs. 3130 with 150 LRABs using 2209 in 26" bbl. If you're not getting any either, slowly work up.