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> 7mm-08 with 180gr ELD-M
7mm-08 with 180gr ELD-M
@ 10:35 pm (GMT) |
Jack DunrossJust out of curiosity, does anyone have any experience with 180gr eldms in the 7mm-08?I'm curious about the velocity and performance from a standard 22" barrel. Also what twist rate would you need to stabilise them? I'm deciding whether I would like to change over to 7mm-08 when I re-barrel my 308, but I quite like that the 308 can shoot the heavies. Cheers! |
Replies
@ 05:00 am (GMT) |
Scott StruifRe: 7mm-08 with 180gr ELD-MHi Jack. A similar question came up recently regarding the minimum twist needed for the .25 cal 134 grain ELD-M. Once you figure out the minimum muzzle velocity, you can use Hornady’s 4DOF calculator to determine the minimum twist rate needed.https://www.ballisticstudies.com/Resources/Discussion+Forums/x_forum/17/thread/24626.html |
@ 08:27 am (GMT) |
Nathan FosterRe: 7mm-08 with 180gr ELD-MHi Jack, I will try to break this down into practical blocks.The 7mm08 is a truly wonderful cartridge. It may not quite have the versatility of the .308 (e.g. 200gr bullets) but the combination of a long 160 - 162gr bullet combined with mild speeds helps this cartridge to obtain a very good balance of wounding, penetration and long range (low wind drift) performance. Of course, the 7mm-08 was never factory loaded in this manner and so to truly understand the virtues of this cartridge, one must hand load. (for the sake of other readers) - The 7mm-08 is no longer in vogue (versus the 6.5). Finding a factory rifle is currently very difficult in some locations. Of those listed, the twist rate is generally 1:9.5. Apart from the few factory rifle offerings (often listed but not available), building seems to be the only option. In light of current component shortages, it pays to back work such a project further than the back working presented in the cartridges book. At this time of writing, it is imperative that you first look to available components. If for example you have been using a medium (i.e. Varget) burn rate in your .308 and have some stock of this, then the transition may be easy. But if you have been using H4895 burn rate (not ideally suited to the 7mm-08), you might find it difficult to find stocks of the Varget burn rate powders. Projectiles are yet another factor. The 180gr ELD-M is a very long projectile. Seated to an OAL of 2.795 (71mm), the intersection of the ogive / bullet body is right at the case mouth with the bullet extending right down into the power column (looks much the same as the 208gr in .308). All that is to say - although the 180gr ELD-M fits, it can be nice to have a bit more mag space to seat the projectile out a bit (the 7mm-08 throat design is well suited to long seating) rather than encroaching on medium burn rate powder space. As is, don't expect much more than 2400fps. Selecting a twist rate for the 7mm08 is somewhat easier than selecting a twist rate for the magnums, though some thought should be given to how the rifle will be used. An 8 twist produces the highest BC's and optimum wounding performance at long ranges, especially if using heavy (175-180gr) projectiles. On the other hand, it can increase stress upon soft 160-162gr projectiles when used at close ranges with a resulting decrease in penetration. Those who have read the latest version of my book Long Range Rifles, will note that I have been taking a much closer look at this subject. The 9 twist is not completely ideal for the 175 to 180gr bullet weights. A 9 twist can produce good accuracy for general hunting plus extended range shooting (out to around 600 yards) but the low RPM does tend to diminish the BC and also decreases wounding potential (though penetration is excellent). The 9 twist may be quite OK if the general role of the rifle is for lighter bodied deer using the 162gr, using the 180gr only occasionally. From the field evidence I have gathered, wounding performance of the 180gr ELD-M is effected by twist. Long dead runs are less likely with a fast twist in the 7mm-08 as a result of increased wounding / bleeding. The compromise is of course the 1:8.5 twist. This does cover all of your needs. For what you are wanting, you could go either way with this - 8 or 8.5. The decision could be made purely based on expected ranges or on body weights. If you want to reach way out, you might choose the 8. If body weights (penetration) is a concern, the slightly slower 8.5 can help to enhance penetration, though the difference is less significant in comparison to using a much slower twist. Please understand that I have made some sweeping statements and gross generalizations here. There are plenty of caveats and contradictions that could be discussed. By the same token, I do not want to promote the idea that one must have X twist rate to be successful. There are a number of NZ shooters for example, using slow twist rates (Tikka 7mm-08's) to hunt large bodied deer out to relatively long ranges, achieving the excellent balance of wounding / penetration that I have previously spoken of in the KB and book series. I hope that helps a bit. |
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@ 08:23 pm (GMT) |
Jack DunrossRe: 7mm-08 with 180gr ELD-MThank you Nathan and Scott!Sorry for the slow reply, I've spent the last few days going down the rabbit hole with the with the information you've given me haha I've read the twist rate section of the long range hunting rifles book twice and have gone into the 4dof app and found where it states the gyroscopic stability figures in the table section. It struck me that the sg number goes up as the bullet travels down range, which is the opposite of what I thought it would do. I then watched the Hornady Podcast series on "exterior ballistics" with one of their ballisticians (thank you Scott), that was really eye opening and I thoroughly reccomend any one reading this to give it a watch. So given that the sg goes up as the bullet goes down range, does this mean that if you trial a long heavy bullet like the 180 eldm in 7mm-08 and you get good accuracy at 100 yards, then are you good to go for long range, or will something else cause it to wobble further down range? Also if you were to seat the projectiles out to the lands and single feed, what potential velocity could you expect from the 180eldm? Or is that 2400fps figure based off seating the projectiles out long? Cleaver firearms has a sale on SS Remington 700 long actions at the moment. $590aud, which seems like a sweet deal! What are your thoughts on using a long rem action for 7mm-08 to have the extra coal? Or would that be overkill? I've had a hard time finding a wyatt extended magazine box here is Aus. I have a good supply of 2206, 2208 and 2209, because I have a 30-06 as well as the 308. I love them both, but I feel like they both are capable of doing the same job, even though the 06 is a lightweight hunting rifle and not at all set up for long range. I mostly shoot roos and fallow deer, but there is a location not far from me that has red deer as well and up north of WA there is goats and donkeys. Plus I dream of hunting trips on the east coast of Aus and also over in NZ one day. The range I regularly shoot at is 800m, but I also have access to a 1000y range not far from me too and can potentially stretch out to 1km on my dads property about an hour away. I feel I may be cutting my potential range a bit short with the 308. Do you find that your skills easily transfer to other calibres? Like is it better to pick a calibre and learn it as best and as thorough as possible, or would I be just as well suited (and better financially) to stick with my 308 until the barrel is toast and then re-assess? Sorry, this is pretty long winded haha |
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@ 07:18 am (GMT) |
Nathan FosterRe: 7mm-08 with 180gr ELD-MHi Jack, generally speaking yes, if everything is fine at 100, it will remain fine (regarding hunting impact velocities well above the transonic barrier).Yes, skills are transferable but it can pay to stick with the one rifle for the sake of proficiency. I understand, its a tough call choosing between the two cartridges, both have their strengths within various applications. Yes a long action can work well though some actions may be a little sloppy with feeding. The Tikka T3 / T3X (only comes in medium length) is perhaps the smoothest when feeding short cartridges. Yes, it is possible to develop a little more power with a longer magazine / OAL simply because one can adopt a slightly bulky slower burning powder that could not otherwise be used with a shorter cartridge OAL. A 24" rather than 20 or 22" barrel also helps. But it pays to not set unrealistic goals. In such a rig, budget on 2650 to 2700fps with the 162gr and 2450 to 2500fps with the 180gr. Anything above this is simply icing on the cake. Sounds like the 1-8 twist will best suit your needs. |
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@ 02:15 am (GMT) |
Jack DunrossRe: 7mm-08 with 180gr ELD-MThanks Nathan, that's exactly what I needed to know!I think I'll stick with the 308 at least till this barrel is burned out and then decide from there. Definitely a tough choice! One benefit of the 308 for me at least, is that 95% of the people at my shooting club shoot 308, so I can compare my progression with my hack against the F class guys with their big heavy rifles and sleds. Currently they have me shooting in the "Hunter division" which is any calibre, but I have to shoot over a bipod and theres almost always no competition. The F Class guys are all 308, so I may be able to jump in with them and shoot over a pack instead of a sled. I think it would be a fun handicap. I'll keep dreaming of a 7mm-08! I haven't given up hope of getting a Wyatt's extended magazine over here for my Remington. Have you noticed any issues with feeding when using a Wyatt's extended magazine? |
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