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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.
Question for you. I am trying to help a friend load for his .260. I started working with 140gr bullets. I have now found out that this rifle( GAP build from about 16 years ago) is running a 1:8.25" twist rate. This seems quite slow to me. Do I need to be working with lighter bullets? The reason I ask is I have had pretty poor results so far with 140gr bullets (Hornady and Berger).
Berger 130 AR. Shoot great out of my LMT 260. Tried heavier and was not great, good. With the 130 gr shoots lights out.
One to 8.5 is fine for 140 grain
BR shooters, use slower twists for maximum accuracy at short range - you can overspin a bullet and destableize it.
Inadequate twist can adversely affect the ballistic coefficient and the Tranzonic transition but with a 260 that usually won’t matter unless most of his work is out past 800 yards
BR shooters, use slower twists for maximum accuracy at short range - you can overspin a bullet and destableize it.
Inadequate twist can adversely affect the ballistic coefficient and the Tranzonic transition but with a 260 that usually won’t matter unless most of his work is out past 800 yards
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Even a GAP that is 16 years old may be in need of a new barrel. What's the round count?
It's actually a low round count rifle. I don't have the exact number but between 500-600 rounds. He got frustrated trying to load for it so I offered. Now I am feeling the same frustration! I load for many other calibers, this one just has me stumped. I have read quite a bit of this thread and what I was working with has been mentioned many times with success.
Well, that’s different than a typical good .260 barrel. I’ve no doubt that there’s something not right with the chamber or barrel. Even good brands can mess up now and then. Try 130s as mentioned, even 123s if you want to continue down the rabbit hole.
Then suck it up and put on a new barrel. Life’s too short.
good luck.So ironically there is a 130 Berger load that the rifle really likes. He was just hoping I could come up with something 140gr that would work well. So, I suppose it's best to just stay with the 130! You are right! Life is too short and all of us could more time shooting vs development or testing! Thanks for your advice!Well, that’s different than a typical good .260 barrel. I’ve no doubt that there’s something not right with the chamber or barrel. Even good brands can mess up now and then. Try 130s as mentioned, even 123s if you want to continue down the rabbit hole.
Then suck it up and put on a new barrel. Life’s too short.
41-44 grs. Of N160 or 560 with Hornady 140 sst’s grouped 1”@100yards for me with a 26” 1:8 twist barrel since 2003.
Interestingly, though mine shoots both 140s and 142s fine, I’ve been a fan of and using 136 Scenar Ls for now on three barrels. I’m very much of the opinion that .260 generally likes the 123-140 range, but is easiest to load for the 130 range.
Waiting on my .260 to get here, but I agree and will extend that to my couple of 6.5c47s.
For an 8.5 twist barrel at 260 rem speeds the Stability factor is 1.36 for a 140 RDF. Stability is considered effective either a stability factor 1.5 or greater. How unstable a bullet becomes if below 1.5 is dependent on a lot of factors. However in general it is not good. So an 8.5 twist barrel is probably not going to perform well with 140 class high BC bullets. Which in term I would limit the rifle to 130 class bullets.
Conversely 8 twist barrels are good up to 147 gr ELD M’s . With 150 SMK’s and 153 Berger’s 8 twist barrels have stability factors of 1.4 . This is why 7.5 twist barrels are recommended for these bullets.
It is the race for extreme perfection in all calibers that keep pushing longer heavier projectiles. It is why you can’t stabilize a .277 Berger 170 gr EOL bullet in a standard twist 1-10 270 Winchester. Never had these 30 years ago. Today you get a 1-8 twist barrel for your 270win and you are good to go.
Just realize that twist rate does in large part determine what class bullets you will be able to effectively maintain performance with.
Conversely 8 twist barrels are good up to 147 gr ELD M’s . With 150 SMK’s and 153 Berger’s 8 twist barrels have stability factors of 1.4 . This is why 7.5 twist barrels are recommended for these bullets.
It is the race for extreme perfection in all calibers that keep pushing longer heavier projectiles. It is why you can’t stabilize a .277 Berger 170 gr EOL bullet in a standard twist 1-10 270 Winchester. Never had these 30 years ago. Today you get a 1-8 twist barrel for your 270win and you are good to go.
Just realize that twist rate does in large part determine what class bullets you will be able to effectively maintain performance with.
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