6mm-284 lets hear it!

[cal30_sniper]

Jumping on this old thread to see if any perspectives or builds have been completed. I have a 6.5 WSM being built right now based on Tikka 6.5 PRC donor rifle. Yes, the 6.5 PRC is already a very capable cartridge, but I want 3,000+ MV out of a 18-20" barrel, and the 6.5 WSM has the case capacity to get there more easily than the PRC. Plus I just like to do things a little different. Factory cartridges are boring. LOL!!!

While researching this build, I've realized (finally) that there is nothing that my .25-284 can do that the 6.5 WSM won't do better. Bullet selection and variety are far superior as is velocity. Thus load options run the gammit of light and fast to heavy and still pretty fast with the WSM. If there were more bullets available between 110 and 130 for the .25s I'd have more hesitation.

After the 6.5 WSM build is complete (and assuming I find a load it shoots well), I will be removing my 25-284 barrel and starting a 6-284 build. I have 105 pieces of Lapua brass that have already been necked down to 25-284 and 6-284 dies are only $100. I plan to anneal and neck down my existing brass. At which point, my 25-284 barrel, Redding dies, and 134 ELDMs will be for sale.

I'm not a guy that keeps a ton of rifles around unless they're being used and I'll use the proceeds from the .25 barrel and components to support the 6-284 build.

Get 3 birds stoned at once and build a 25 Pronghorn (25-300 WSM). Dies available from Redding.

 

[jjohnsonElknewbie]

Get 3 birds stoned at once and build a 25 Pronghorn (25-300 WSM). Dies available from Redding.

Cool cartridge for sure, and although slightly better BC, it won't outrun the 6.5WSM with 130 class bullets (ELDM and TMK). The 6.5 also has 140s, 143, 147, and even 156 if you want to shoot super heavies.

 

[cal30_sniper]

Cool cartridge for sure, and although slightly better BC, it won't outrun the 6.5WSM with 130 class bullets (ELDM and TMK). The 6.5 also has 140s, 143, 147, and even 156 if you want to shoot super heavies.

More recoil and slower velocity with any of the 140+gr .264 bullets that will match the 134gr ELDM ballistics.

The 130 ELDM starts faster than the 134, but is quickly overtaken due to the significantly lower BC. The 130TMK is even worse.

No grass growing under the 6.5WSM feet for sure, but seems a shame to overlook the 25 since you have the bullets already

 

[jjohnsonElknewbie]

More recoil and slower velocity with any of the 140+gr .264 bullets that will match the 134gr ELDM ballistics.

The 130 ELDM starts faster than the 134, but is quickly overtaken due to the significantly lower BC. The 130TMK is even worse.

No grass growing under the 6.5WSM feet for sure, but seems a shame to overlook the 25 since you have the bullets already

The .257 134 ELDM has a .645 G1.

The .264 140 ELDM has a .646 G1.

The powder/recoil penalty for similar MV is marginal between these two and likely splitting hairs. 134 availability can also be hit or miss sometimes as well.

I'm not hating on the .25s, and my 25-284 is a sweet shooting rifle. The 25 creed, -06, -06AI, .257 WBY, etc..., are all great cartridges. However, the 6.5 is more versatile simply given the much larger catalog of quality heavy for caliber bullets, especially from 120-147gr.

From Hornady alone you have the 120 ELDM, 123 ELDM, 130 ELDM, 140 ELDM, 143 ELDX, and 147 ELDM. Berger, Sierra, and Nosler have several other good bullet options in this range as well.

Unfortunately, in this range today in .257 you have 5 choices-120 Grand Slam, 131 Sierra MK, 133 Berger, 134 ELDM, and 135 Berger.

 

[cal30_sniper]

The .257 134 ELDM has a .645 G1.

The .264 140 ELDM has a .646 G1.

The powder/recoil penalty for similar MV is marginal between these two and likely splitting hairs. 134 availability can also be hit or miss sometimes as well.

I'm not hating on the .25s, and my 25-284 is a sweet shooting rifle. The 25 creed, -06, -06AI, .257 WBY, etc..., are all great cartridges. However, the 6.5 is more versatile simply given the much larger catalog of quality heavy for caliber bullets, especially from 120-147gr.

From Hornady alone you have the 120 ELDM, 123 ELDM, 130 ELDM, 140 ELDM, 143 ELDX, and 147 ELDM. Berger, Sierra, and Nosler have several other good bullet options in this range as well.

Unfortunately, in this range today in .257 you have 5 choices-120 Grand Slam, 131 Sierra MK, 133 Berger, 134 ELDM, and 135 Berger.

We seem to be ignoring the .257 138gr A-tip at .695 G1. You’ve got to go to 147gr or 153gr to beat that in a .264, and even then just barely. Right now, .257 is the king of BCs vs weight, which is where you’re going to find long range performance when case size is fixed.

I guess I don’t place a huge amount of stock in versatility as a criteria. It’s like saying 7 Rem Mag is more versatile than 7 PRC because there are more factory loads available for it. How many loads/bullets does a guy need to be effective? 1 or 2?

I’d also point towards the resurgence in quarter bore stuff recently. Starting with the blackjack bullets and culminating in standardization of 25 Creedmoor this year, we’re seeing a large percentage growth in offerings for that caliber. I’d find it hard to believe that trend won’t continue at least for a while.

Now, if we could just get a 125ish grain ELDM in 6mm, we could put both of these heavier caliber options to bed as inferior choices. Until then, hopefully 115DTACs stay available.

 

[B23]

Now, if we could just get a 125ish grain ELDM in 6mm, we could put both of these heavier caliber options to bed as inferior choices.

Heck, even a 120gr ELD-M 6mm would probably make a lot folks happy.

But, at what point do they get so long and require such a fast twist that the velocities some of these hot rod 6's are capable of blow em up before the reach the target....

 

[jjohnsonElknewbie]

After looking around online at the usual vendors and Ammoseek, 6.5-284 brass is no longer readily available. This time last year I had no trouble finding it from multiple places and was able to shop around for the best deal (thank you Gunwerks).

Based on this, I think @Brandon.miller.4 is on to something with a 6 PRC instead. Hell, maybe a 6 WSM since I'll already have the brass. Maybe there's some dies out there somewhere...

On the more pragmatic side, 284 brass is still available in several places, and a two-step process from 284 to 6.5mm then 6mm is another option.

 

[cal30_sniper]

Yep, Lapua has been sporadic with brass and it probably won’t get better as long as the Slavs are at each others’ throats. 6PRC makes a lot of sense now, at least as long as Hornady has their weight behind it.

Then again, if you’ve got a good supply of 25-284 already formed, you can get scads of additional firings out of it as a 6mm-284 at reasonable pressure.

 

[wyosam]

I sure wouldn’t consider brass as a problem for any 284 variant, especially necking it smaller than 6.5. Buy 100 pieces of Peterson and it will outlast at least your first 2 6-284 barrels unless you’re intentionally bearing the crap out of it.


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[jjohnsonElknewbie]

I sure wouldn’t consider brass as a problem for any 284 variant, especially necking it smaller than 6.5. Buy 100 pieces of Peterson and it will outlast at least your first 2 6-284 barrels unless you’re intentionally bearing the crap out of it.


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I have 105 Lapua cases. 6-284 is my likely route so I don’t have to change bolt.

 

[jjohnsonElknewbie]

As a head's up, my .25-284 barrel and components are for sale in the classifieds.

 

[jjohnsonElknewbie]

Has anyone running a 6/284 in a Tikka action had the chamber custom throated? I am thinking I will get my chamber throated to suit a 108gn ELD-M seated out to fit a Tikka 30-06 length magazine.

I had UM chamber my 25-284 freebore to accomodate the 134 ELDM at 3.14" col. I will be doing the same with my 6-284 with the 115 DTAC seated out with BT close to shoulder/neck junction. This is an easy peasy method that won't require any changes to botl, bolt stop, or mags.

 

[TimberHunter]

I had UM chamber my 25-284 freebore to accomodate the 134 ELDM at 3.14" col. I will be doing the same with my 6-284 with the 115 DTAC seated out with BT close to shoulder/neck junction. This is an easy peasy method that won't require any changes to botl, bolt stop, or mags.

Curious, why the 6-284 instead of a 6-06?


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[jjohnsonElknewbie]

Curious, why the 6-284 instead of a 6-06?


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In my case, I already have 25-284 brass on hand. I also prefer the shoulder geometry with the 284 case over the -06 as it leads to less stretch and trimming. You could get the same benefit from a 6-06AI, but it’s an extra step.

I’m not certain with the 115 DTACs, but you may also run out of mag length in a standard L mag with the -06 case. If so, then you’re potentially looking at aftermarket DBM, mags, and extra long bolt stop which adds cost/complexity to the build.

 

[TimberHunter]

In my case, I already have 25-284 brass on hand. I also prefer the shoulder geometry with the 284 case over the -06 as it leads to less stretch and trimming. You could get the same benefit from a 6-06AI, but it’s an extra step.

I’m not certain with the 115 DTACs, but you may also run out of mag length in a standard L mag with the -06 case. If so, then you’re potentially looking at aftermarket DBM, mags, and extra long bolt stop which adds cost/complexity to the build.

Thanks for the info. This is something I’m kicking around doing on the next rifle. 25-06 would likely be the easy button but really looking to shoot the 108/115 bullets


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[cal30_sniper]

I’ve finished loading my development ladder. 115 DTACs seated long over a case full of Retumbo. Just waiting on the rifle to show up now:

 

[TimberHunter]

I’ve finished loading my development ladder. 115 DTACs seated long over a case full of Retumbo. Just waiting on the rifle to show up now:
View attachment 853664
View attachment 853665

Any idea what kind of velocity you’re expecting? And a case full is about how many grains? Trying to decide if I want to go 6/06 or 6/284


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[TimberHunter]

Any idea what kind of velocity you’re expecting? And a case full is about how many grains? Trying to decide if I want to go 6/06 or 6/284


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Just looked it up, looks like the 25-06 will push a 115 but to about 3100 so assuming the 6mm-06 does the same. Looks like the 284 has a bit less capacity so maybe a bit slower. Looks like a 243AI could do about the same as a 6mm-06 with less powder?

Edit:

Looking at the 30-06 nosler load data, 110 30 cal bullet shows getting up to 3400. I assuming me king it down to 6mm and shooting a 115, would result in a similar velocity, maybe 3350?

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[cal30_sniper]

Just looked it up, looks like the 25-06 will push a 115 but to about 3100 so assuming the 6mm-06 does the same. Looks like the 284 has a bit less capacity so maybe a bit slower. Looks like a 243AI could do about the same as a 6mm-06 with less powder?

Edit:

Looking at the 30-06 nosler load data, 110 30 cal bullet shows getting up to 3400. I assuming me king it down to 6mm and shooting a 115, would result in a similar velocity, maybe 3350?

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I would not assume that you'll hit the same velocities as a light .308 caliber bullet from a .30-06 with a similar weight 6mm bullet. Those two cartridges are going to prefer very different propellant burn rates due to the case capacity vs bore area relationship. Generally, a larger bore will allow the same case capacity to push a similar weight bullet significantly faster (or a heavier bullet at the same speed). If you ran one of those 110gr 30-06 loads in a 6mm-06, I bet you'd hit you'd hit big time pressure.

As an illustration of this point, Gordon's Reloading Tool shows the RL15 load listed above for a .30-06 would result in 127,000 psi in a .25-06. It would be even worse in a 6mm-06 with an even smaller bore area:



Editing to show the GRT data for the published .30-06 Nosler Varmageddon RL15 data. As you can see, the same charge of RL15 in a .30-06 shows very reasonable pressure values behind a 110gr bullet:

 

[cal30_sniper]

Any idea what kind of velocity you’re expecting? And a case full is about how many grains? Trying to decide if I want to go 6/06 or 6/284


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My first load ladder works up to 57.4gr of Retumbo at a COAL of 3.1". This is way over any book data you will find, but keep in mind that book data is almost always for a 2.8ish inch COAL, which has the bullet eating up a lot more volume inside the case.

GRT says at this COAL I should be able to work up to 60.4gr, for a 2900fps muzzle velocity (from an 18" barrel). For comparison, the 24" barrel that most reloading data muzzle velocities are based off of puts it at 3160fps:


I think I'm going to skip over some of my lower ladder rungs (I originally started at 50gr), which were based on load data with the much shorter short mag COALs. I'll probably fire a few at 53gr (book max for the short COAL) and then start heading up from there based on what I see. Lapua cases and a BAT action should tolerate any accidental higher pressure I might run into doing this, but I don't want to start too low, because that can actually cause even worse pressure issues to show up.

Retumbo in this case should like to run pretty close to slightly compressed based on everything I can find.