7mm-08 barrel twist

[simgre]

My 7mm-08 is nearly 20 years old now, and still wears the original Archer 1:9.5" twist. My preferred bullet, as only used for target work, is the Sierra Matchking in 168gn. It's a long bullet, which is really the consideration with rifling twist, not weight. 1:9.5" stabilises this long bullet perfectly.

 

[7Miller]

Picked up my 7mm-08 last week from Mike Norris of Brock and Norris rifles.

I told him I will be shooting the lighter end of the range, around the 120gr region. Although, 2 mates use 100gr Sierra Varminters in their 7mm-08 but I don't know what twist rate they have but Mike Norris also built both of thier rifles.
Mike fitted mine with a 22" IBI barrel with a 1:8.5 twist.
I've done an initial batch of homelaods with 120gr Nosler BT, with N150 and have produced some half MOA groups at 100 yards, but I've still got plenty of work to choose and tune my chosen load. I also put 3 of my mates 100gr through and again got half MOA group. He's getting a single hole through his own rifle but that load was obviously developed for his rifle.

So 1:8.5 seems a decent twist rate in my 7mm-08

 

[MountainStalker2]

A std 1:8 to 9.5 twist should be fine. I question you wanting to shoot 150/160 gn copper pills in a 7/08. Normal practice with copper is to drop back 1 to 2 weights and increase MV to get consistent expansion at all ranges. A 120 - 140 gn copper pill gives you the velocity required for penetration and expansion at ranges to 300+ meters, on red deer and pigs. These shorter projectiles wont have to be seated as deep into the case (reducing powder capacity) as a 150 or 160 gn pill.

 

[Penyard]

I agree with @MountainStalker2 , copper needs to be a bit lighter and a bit faster in my experience. I’m shooting 110gr TTSX in my 7-08 and they are brilliant and would be very happy taking on any deer in the UK out to 300m. It’s a 1:9 twist and works fine with 150gr Swift Sirocco, 120gr Nosler BT, 120gr and 110gr TTSX.

1:8 will work just fine but I would suggest 1:9 will do everything you want

 

[KimE]

Hello

Interesting discussion. Well I think the old european 7mm cartridges have been using 1/8,5 twist rates to stabilize even the 173 gr lead bullets, and they did so fine i assume, to taken into consideration the lower density of copper of arround 20% and the longer and sleeker Low drag designs of some of todays coppers, well yeah, 1/7 or 8 might be a good number for being able to shoot sleek 140 something grn copper.

But when one is considering twist rate (to accomodate the use of longer bullets) in the 7mm08, and "future proof it", Should one perhaps consider the length of the neck of the case that one is using too? I say this in a context of being able to seat those longer bullets, without giving up too much powder capacity.
In that case, an older, but ballistically very similar cartridge, like the 7x57, might actually be more "future proof", might it not?

This said, i am only starting to reload myself, so more expert members on this board on reloading might be able to correct me here, (which i hope they do, if needed!).

Good luck with the new build!

PS. Regarding potentially going to fast on twist rates, i think Ron Spomer raised this topic once, so it might be a good idea to have a look for it on YT or spotify or similar. Found it:

Yes old 7mm*57/64 are used with 173gr roundnose bullets with a long throat for the tubular shape, it might be different with a VLD plastic tipped bullet. Mag length might be an issue with long bullets in .308w action lenght rifles. Modern cartridges are often throated for match shaped bullets. European barrels might have different dimentions on rifle groves so US manufactorers may be tighter more sensitive of what kind of bullets you are using.

 

[Scipio]

Yes old 7mm*57/64 are used with 173gr roundnose bullets with a long throat for the tubular shape, it might be different with a VLD plastic tipped bullet. Mag length might be an issue with long bullets in .308w action lenght rifles. Modern cartridges are often throated for match shaped bullets. European barrels might have different dimentions on rifle groves so US manufactorers may be tighter more sensitive of what kind of bullets you are using.

Good point about US vs European threading practice @KimE , would this also apply for the older classic US cartridges, like the 30-06 and it's derived kin? Because like the classic European cartridges, those were originally intended for war and/or hunting use?

Interesting thread this, and i hope the thread starter will let us know which path he takes, and how it goes

 

[suburban bushwacker]

I have 1/8 16" and it's fine with non lead 120s
I also have a 22" 1/7.5 that will stabilise 162g and probably longer projectiles.

1/8 will be totally fine.

What sort of speeds are you seeing?

 

[Tubby10]

What sort of speeds are you seeing?

22" 2600 with 162 eldx
16" 2850 with 120 Merlin's

 

[suburban bushwacker]

22" 2600 with 162 eldx
16" 2850 with 120 Merlin's

that's interesting, have you tried the 162 in the short barrel?

 

[Tubby10]

Yes they wouldn't stabilise

 

[MountainStalker2]

Good point about US vs European threading practice @KimE , would this also apply for the older classic US cartridges, like the 30-06 and it's derived kin? Because like the classic European cartridges, those were originally intended for war and/or hunting use?

No, American made sporting cartridge chambers in factory rifles are cut to a standardized specification set out by SAAMI.
The .30-06 was designed with a lighter spitzer shaped loading in mind. The precursors to the 06, the .30 krag and .30-03 may differ.
European manufactures have a similar organization (abbreviated to CIP) that sets the specs for them.

 

[MountainStalker2]

"Yes they wouldn't stabilise"
Lots of folks shooting long 162 grain ELDm in short barrels with suppressors in factory rifles and barrels in (7/08, .284W, 7 mags) in NZ and having good results.

 

[Tubby10]

"Yes they wouldn't stabilise"
Lots of folks shooting long 162 grain ELDm in short barrels with suppressors in factory rifles and barrels in (7/08, .284W, 7 mags) in NZ and having good results.

I did try, but I think 16 inches was just a bit too short, I've not bothered with trying something in between but 120grain copper bullets are totally fine.