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Not all is lost. You have two data point temps and their respective velocities. They show an average of 2fps per degree of change. An easy calculation that can even be entered in many ballistic calculators.
You can even verify this by shooting at another data point temp and seeing how close that gets you.
So I bought a Tikka 260 CTR with the ideal of building a 280 AI. However I threw some loads together (139 Scenars/ 42 grns H4250) and after a quick zero, shot a .4 group. I decided I would postpone the 280 build and use it for deer hunting this season. I have been trying to work up a load with some 142 grn ABLR's. I've been to the range a couple times and the last 3 rounds I fired were 43.2 grns of H4350 averaged around 2550 fps ...slower than expected. I plan to bump the charge up to 43.6 - 44. I'm hoping for 2750 - 2800 fps.....am I asking too much for the CTR's 20in barrel and does anyone know of another powder that might get me speed.
Why don’t you just use the 139 Scenars for hunting? I’m pretty sure that @coldboremiracle was using them successfully on many hunts.
You should be able to easily get 2750-2800 with those and they are very consistent shot to shot.
You should be able to easily get 2750-2800 with those and they are very consistent shot to shot.
I could use the 139's but I have about 190 of the 142 g ABLR's. Anyone killed a deer with a 139 Scenars ?
I was wrong above and meant to reference @psinclair as the person who used 139s for a long time with numerous kills every year. He spoke highly of them.
If you want to check out this 10+ year long thread on 24hour campfire, you’ll see the consistency I’m referencing.
Also search here on SH as there are a number of threads discussing similar.
This one very briefly:
Hunting & Fishing - 6.5 139 grain Lapua Scenar for hunting?
Anyone use this bullet with success (or failure)? Was thinking about using it for an upcoming Coues deer hunt in AZ - since these shoot so well in my DT SRSA1.
www.snipershide.com
Thanks....really enjoyed the 24 hr thread,I was wrong above and meant to reference @psinclair as the person who used 139s for a long time with numerous kills every year. He spoke highly of them.
If you want to check out this 10+ year long thread on 24hour campfire, you’ll see the consistency I’m referencing.
Also search here on SH as there are a number of threads discussing similar.
This one very briefly:
Hunting & Fishing - 6.5 139 grain Lapua Scenar for hunting?
Anyone use this bullet with success (or failure)? Was thinking about using it for an upcoming Coues deer hunt in AZ - since these shoot so well in my DT SRSA1.
Ive used Scenars for hunting, but not the 139. I'd have zero issues trying them though based on my experience with other Scenars as well as other hunters experiences.
I've used a variety of other 140 glass match bullets, like the Barnes Match Burner, Hornady BTHP, and Sierra Match Kings.
I’ve had similar results, but did incorrectly reference you when I meant @psinclair . I’m actually most fond of the 136g Scenar Ls, though they are not inexpensive at all.
Got 2575 today with 43.5 gr, H4350 / 142 ABLR no signs of pressure, Just loaded 2 @ 43.7 & 2@ 43.8 gonna try them tomorrow.
The max SAAMI pressure for the 260R is 60,000psi.
I ran your loads in QuickLoad and every one of them is significantly over pressure for a 20" barrel, but I don't know your seating depth. I initially ran the loads at a seating depth of 0.680 and each was over pressure. I understand QL is conservative, but you should be getting faster speeds with your loads if you're using that seating depth and charge:
43.2grs of H4350 with the 142 ABLR is calculating overpressure @ 68,495psi, but speed should be in the 2723fps range. You're only getting 2550ish so something else is slowing you down or your seating depth is higher.
43.5grs is calculating 70,070psi @ 2741fps.
43.7grs is showing 71,451psi @ 2751fps.
43.8grs is showing 71,683psi @ 2760fps.
I re-ran the calculations using a seating depth of 0.50 and the pressures were significantly lower, but you're still not getting the speeds you should:
43.2grs was 60,483psi @ 2648fps.
43.5grs was 62,152psi @ 2665fps.
43.7grs was 63,044psi @2671fps.
43.8grs was 63,494psi @2683fps.
If your seating depth is reduced from 0.50 to 0.40, then each of your loads is under pressure but even your 43.8gr load is calculating 2683fps.
Good info....Before loading I checked the OAL with a Hornady OAL gauge the 142 it was 2.99 touching the lands. I loaded the ammo to 2.82
2 things:
Did you account for the particular brass he's using to get an idea what the average case volume might be, or . . . did he already provide the case volume?
Being a new gun, new barrels tend to be slow, where it take 150+ rounds down the tube before the velocity settles in at 100 fps or more higher.
Prime Brass (New) ....Starting to wonder about my Garmin. For reference I loaded some 142 ABLRs for my 6.5 CM w/41.5, 41.6, 41.7, 41.8, & 41.9 H4350...they shot 2680 - 2730 FPS...the last couple were on the hot side.
When one is using QuickLoad, to get a more accurate rendition of a load, it's best to input the case volume of the particular brass being used after they've been fired. It can make a significant difference in the QuickLoad calculation as the default case volume it uses is not always close the what's being used.
This is why I asked.
My point was to gently suggest you may be loading too hot. Nosler load data caps out below what you tested for the 142s, and they tested in a 24" barrel, which adds about 20fps in speed per inch over your 20" barrel as the powder has more time to be fully consumed.
There are several variables affecting QuickLoad outputs, and the QL data tends to be conservative, but I'd suggest you're chasing speeds you may not attain in a 20" barrel (even after it speeds up) and to offer that your loads could be overpressure.
Recheck your Garmin settings as there are probably tens of thousands in the field and I've not seen any reports of faulty speed captures. You could move the unit from one side of the rifle to the other, or over the barrel to try to confirm consistency.
