Short Action 6mm Questions

Have been pondering this for a while but looking at options for a 6mm build that would allow me to take advantage of the high BC 100gr+ bullets but still utilise a factory short action Sako Finnlight. Currently have the rifle in 243 and really like it. Handles well and is a quality build. Have a 7RM T3 that I was looking to replace with a Sako in 7RM but after thinking for a while, most of my hunting is <500m and I'm not a fan of carrying a heavy rifle. I've come to the conclusion that, pending advice, I would be better off selling the 7RM and having my 243 reamed/rebarreled in to something that can take full advantage of the 6mm projectiles. Keeps the rifle light, recoil down, and sufficient energy at 500M to do the business. There are some good 105gr projectiles out there and if I can push them to just over 3000fps sounds like a win for me and I have a rifle that's light and handy to take in to the bush but still capable on the tops.

Any suggestions on calibers to look at? Pros and Cons? Seriously considering just doing a 243AI however with the Sako 1:10 twist would likely need to rebarrel to 1:8 regardless of caliber. Saves a bolt face mod I guess. Prefer to keep barrel at 22" or less.

If you feel you have to be able to cleanly kill animals out to 500m all the time with 6mm, you better start with a long action and go 6mm06, 6mm284, 6mm RemAi or .240 Weatherby and you are still stretching it, more so if the animals targeted are large high density animals. Keep it to 400yds and run the 95 Berger or Tmk, no money spent, job done. Get a hold of @Flyblown for comment.

No expert in this at all, but I have used a 1:8" twist .243AI Win shooting the 105gr A-Max in Colorado, which was an excellent rifle, shooting winter coyotes with ease past 600m. Very very accurate, effective chambering.

The other option is the 6mm Creedmoor, which achieves pretty much the same outcome.

There are some fast wildcat alternatives, maybe @Wingman can comment because I believe he's been looking at this in the last few days. @Kiwi Greg too, he'll be well clued up.

I would second @257weatherby on the matter of game weights - I'd be a bit skeptical of shooting deer with a 105gr 6mm past 400m. To me, past 350-400m, a fast heavy 6mm is a great varmint option but a poor deer option.

Cheers guys, thanks for the advice. Primary purpose would be around the Kaimanawas for sika. Hmmm, now the mind wonders if I should go 6.5. Still prefer to mod my SA if possible Vs buying another rifle but shall see how we go.

Despite being a massive fan of the .243 Win, with which I've taken more deer than all the others put together, I would advise you to step up to a 6.5mm or 7mm and shoot something in the 140-150gr range.

For me, the .243 is a precision rifle I use in quite open country where I can line up a shot with time on my side, so I don't tend to take it into the Kaimanawas or similar type environments. I go with my .308 Win, because I've learnt the hard way over the years that in tighter environments, more weight tends to deliver a more reliable outcome... more forgiving of snap shots, shot placement, intervening vegetation, harder hitting.

Others are sure to disagree! But overall, on the balance of pros and cons, I'd probably select a 7mm-08 for that job. It's a great mid-range option for sika sized animals, you can push a 140-150gr pill at 2800fps+ no worries and that will deal to a deer at 500m assuming you know what you're doing, and you're confident you can find the bastard if it runs.

The three other sensible options include the 6.5 Creedmoor, .260 Rem and of course the .308 Win. Don't discount the .308, I've recently been using mine again after a barrel shortening / suppression / chassis revamp, and I absolutely love it. Any of these four options mentioned will do the job with practically nil observable difference with a 140-150gr hunting bullet.

I second Flyblown's comments, as a keen Sika hunter myself I think the 6.5 Creedmoor with 143 ELD-X is just about the perfect Sika medicine for your intended range. It has a good combination of low recoil, flat shooting and the ability to load high BC bullets at short action mag length. The 260 and 7mm08 are right there with the 6.5-CM but to get the best from them with high BC bullets you really need to load them longer than short action mag length. My 7mm08 for example shoots 150ELD's best loaded 50 thou off the land's which equals a cartridge length of 2.936 inch in my rifle. Thats 0.130 inches or 2.69mm longer than my mag so I am going to convert it to a long action which is quite easy in a Tikka.
The 308 is also good but if you want low recoil a 6.5CM would be the way to go.

Want to shoot the long slippery bullets in a short action.. cant go past the 6 or 6.5X47 Lapua or Creedmoor case. Whether it be 6mm or 6.5mm it will do the job.
Also loving my .308 again.. does it all with the 175gr bullets with a tad more recoil than the fore mentioned cartridges.

According at alliants load date RL26 will push 105gr bullets to over 3000 fps from a standard 243.
I'm getting just on 3000 fps from mine and 0.7 gr under their max. will note that it's a cheap crony I'm using.
That will give you over 2100 fps and just over 1000 fpe at 500 mtr.

that put you above the 17-1800 fps velocity where bullet expansion performance drops off.
Not going to say that there are not better options for shooting deer at 500 mtr but it can be done.
mate had a large hind get up and bolt after a short range hit from his 7m08 using a 139 SST Hornady last year.

all about bullet placement
Zq

re the bullet placement , you need to add "and a bit of luck". Years ago I shot two nanny Tahr at 220/250ish with 6mm 105 amaxs at 3000fps and both were only wounded despite reasonable shot placement. One shot right on the shoulder went down but by the time I'd finished the other one it had got away - I followed a good blood trial for ages but had to give up when it got into a very steep dangerous gully. Heartbreaking.

I know amaxs are a thing of the past but the jackets in the ELD-M's and other bullets of the same type are pretty similar.

I'd love a 6mm build like the OP is suggesting but I'd be taking other rifles if it was Deer or Tahr I was hunting (maybe unless I was using a partition or monolithic or the like projectile). If something turns up close its a crap shoot in my opinion.

Using the ELD-M or Berger hunting bullets I don't tend to aim for the foreleg/shoulder, I aim just a bit further back into the ribs as in my experience these bullets penetrate a 2" (87gr) -4" (105gr) and then it's like a grenade went of in the chest, heart & lungs shot up. They are dead but yes they can still do a dead run.
I'm not that confident on anatomy and placement to date that I have tried for the nerve centers or neck shots.
87gr will exit a goat but not a fallow deer. 105 is still opening up on a goat side on when it exits so is very messy.
Must admit that my 358 will anchor a red deer better than the 243 at shorter ranges. (They don't go anywhere with 2 broken shoulders but the front end is stuffed for eating.)
Z
Ps yes I have had a close in failure to expand as has a mate with 7mm SST so yes for the close in stuff an ELD-X or Partition would make sense.

An alternative to the .243 would be the 6xc which was designed for the heavier projectiles. Not a hell of a lot of difference once you give a .243 a 1in8 twist.
But out to 500m I would be looking to something bigger.

Thanks again guys. Looking at the 6.5 shift. Just to be difficult seriously considering a 260ai.