Post by: 7mmfan on January 24, 2020, 09:17:15 AM
I.E. - slower twist rate for heavier/longer bullets, faster twist rate for lighter/shorter bullets.
I'm developing a new load for both my 7 mag and 7mm-08 and came across some info suggesting the twist rate for the 7 mag is designed for heavier bullets, specifically 160 gr and above.
The 7mm-08 I own has only a slightly faster twist making me wonder if a heavier bullet would group better than the lighter bullets I continue to try and develop loads with.
Post by: hunter399 on January 24, 2020, 09:32:30 AM
Post by: JimmyHoffa on January 24, 2020, 09:38:29 AM
With powder options and bullet designs, you should be able to counter was in the past was twist limitation.
Post by: BULLBLASTER on January 24, 2020, 09:39:01 AM
Post by: Karl Blanchard on January 24, 2020, 09:54:49 AM
Post by: HawkCreek on January 24, 2020, 10:04:41 AM
https://bergerbullets.com/twist-rate-calculator/
Post by: buckfvr on January 24, 2020, 10:05:30 AM
In general a faster twist rate is required for longer, heavier bullets.
This is the correct answer.......also, when considering heavy for caliber (which by necessity will be longer), check mfg recommended twist rate and as in Berger bullets, it clearly states OR FASTER. Its better to run a 7 twist rather than a 9 when the box says 8 or faster.
With Bergers stabilty calculator, it is simple to check the bullets probable stability by entering down range velocities, not just going by muzzle velocities. For hunting, I make sure I am shooting at ranges that dont exceed the stability of the bullet. For practicle hunting ranges, of say 400-500 yards or less, it really doesnt make much difference unless you are doing something similar to shooting the 180/190 class bullets from a 9.5 twist 7mm rm.
Deficient twist rate wont show huge in 100 yard groups sighting in.....even 200.
Not knowing your rifles twist rates are, just for grins, check out Bergers calculator. https://bergerbullets.com/twist-rate-calculator/
Post by: Karl Blanchard on January 24, 2020, 10:20:23 AM
Post by: Buckjunkie on January 24, 2020, 12:24:38 PM
I will admit that I do enter many loads into my Shooter App and pay close attention to the stability factor. “Almost” every stable load I shoot has a stability factor higher than 1.80. The Shooter app is $10 to download on your Phone.
Post by: 7mmfan on January 24, 2020, 12:33:56 PM
What twists do you have in each?
I was under the assumption the 7 mag was 1:9.5 but I just reviewed Ruger's website and the current model is 1:8.5 sooo....?
The current Remington Mtn Rifle in 7mm-08 is 1:9.25
Post by: Karl Blanchard on January 24, 2020, 01:21:50 PM
Post by: buckfvr on January 24, 2020, 01:27:24 PM
180 and under in the mag and 160 and under in the 08 and you'll have nothing to worry about
:yeah:
Post by: 7mmfan on January 24, 2020, 01:29:07 PM
I'm working on Barnes 145 TTSX LRX for the 7 mag and Barnes 110 TTSX in the -08. If anyone has any firsthand experience loading either of these, I'd be happy to hear about it.
Post by: buckfvr on January 24, 2020, 01:41:40 PM
Well that was easy.
I'm working on Barnes 145 TTSX LRX for the 7 mag and Barnes 110 TTSX in the -08. If anyone has any firsthand experience loading either of these, I'd be happy to hear about it.
Im a couple months out on starting a 7mm 08 but it will be with 120gr ttsx as I want to get 400 yards with enough energy for mules.......pure woods deer rifle is my thought.....Im at 168gr with my 7mag and its limitations are ethical, as its ding dong to 1200 yards, far beyond perfect world 800 yard shot. Farthest so far with 7mag is 650 one shot drt. May never see farther.
Post by: JimmyHoffa on January 24, 2020, 02:06:08 PM
Post by: 7mmfan on January 24, 2020, 02:08:25 PM
Well that was easy.
I'm working on Barnes 145 TTSX LRX for the 7 mag and Barnes 110 TTSX in the -08. If anyone has any firsthand experience loading either of these, I'd be happy to hear about it.
Im a couple months out on starting a 7mm 08 but it will be with 120gr ttsx as I want to get 400 yards with enough energy for mules.......pure woods deer rifle is my thought.....Im at 168gr with my 7mag and its limitations are ethical, as its ding dong to 1200 yards, far beyond perfect world 800 yard shot. Farthest so far with 7mag is 650 one shot drt. May never see farther.
I loaded the 120 TTSX in my -08 last year with good results, but these 110's have been pestering me for a while so I'm going to develop a load and test them out. If I can get them pushing 3200-3300 fps they should be a rocking deer load too 400+ which is my self imposed limitation.
I've been shooting 154 gr Interbonds in the 7 mag for years and have a 3/4 MOA load for it. I can hit milk jugs to 700 every time. But that bullet is no longer available, and if I'm going to develop a new load, I'm going to go mono as I think that's where the market will be going eventually. I don't see taking a shot at more than 500 yards unless it's a hail mary followup shot, so I'm not to worried about ballistic performance at 700-800-900 yards.
Post by: 7mmfan on January 24, 2020, 02:10:06 PM
Barnes are a little different when going solely on weight. The copper bullets are longer than a lead core bullet of the same length.
Yes, the 145 LRX is the exact same length as a 160 Accubond. That information is what got me on this twist rate project. The information I read is that the twist rate isn't actually designed based on weight, but length of bullet. Since virtually no one categorizes their bullets based on length, weight is the easiest and most common reference.
Post by: Caseknife on January 25, 2020, 07:47:52 AM