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Holy Grail of Short Action 7mm Cartridges...?

turbo54

turbo54

Mr. 7mm
Full Member
Minuteman
Dec 10, 2010
4,995
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Michigan
NON MAGNUM

FITS AICS or AW magazines

Far as I can tell, there is really only 1 mainstream cartridge: the 7-08 or the 7-08AI.

I'm not opposed to either of them, but there has been some hubbub about the 7mm Creedmoor.

I've also been tossing around the concept of a 7mm SLR.

I want to rebarrel an M2008 short action in a 7mm of some flavor that feeds from AW magazines, with a max COAL of 2.900"-2.950".

I'm not interested in magnum recoil, muzzleblast, barrel life, or powder consumption.

I'm NOT opposed to wildcats, though "rigorous" wildcatting involving false shoulders, fireforming and neck turning is a bit much.

Let's get a discussion going of what can be done to achieve the highest performance 7mm cartridge in a short action.
 
Re: Holy Grail of Short Action 7mm Cartridges...?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: pwc001</div><div class="ubbcode-body">What about a .284? </div></div>

Don't think those will work so well with AW magazines...?
 
Re: Holy Grail of Short Action 7mm Cartridges...?

Just go 7-08 AI and push a 162 AMAX, alreday data about the round floating around too.
 
Re: Holy Grail of Short Action 7mm Cartridges...?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: pwc001</div><div class="ubbcode-body">What about a .284?</div></div>

I'd consider the .284 long action even though it could be run on a short action.

The 7mm bullets really hit their stride (BC wise) in the 180s and along with the introduction of berger's 195gr hybrid. Given the 168gr VLD has a good BC, i'm more favorable to the heavier projectiles. Which would lead me at a .284 and up as my preferences.

7mm SLR would be very interesting.
 
Re: Holy Grail of Short Action 7mm Cartridges...?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Blackops_2</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: pwc001</div><div class="ubbcode-body">What about a .284?</div></div>

I'd consider the .284 long action even though it could be run on a short action.

The 7mm bullets really hit their stride (BC wise) in the 180s and along with the introduction of berger's 195gr hybrid. Given the 168gr VLD has a good BC, i'm more favorable to the heavier projectiles. Which would lead me at a .284 and up as my preferences.

7mm SLR would be very interesting. </div></div>

I agree with the .284 and a long action, but I asked because it will fit in a short action.
 
Re: Holy Grail of Short Action 7mm Cartridges...?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: turbo54</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: pwc001</div><div class="ubbcode-body">What about a .284? </div></div>

Don't think those will work so well with AW magazines...? </div></div>

He sais AICS or AW mags.
 
Re: Holy Grail of Short Action 7mm Cartridges...?

7WSM using Alpha Type 3 or Type 4 AICS mags allowing COAL of 2.985".
wink.gif



I too would be interested in the 7mm SLR and/or the Creedmoor should it ever materialize.
 
Re: Holy Grail of Short Action 7mm Cartridges...?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: ORD</div><div class="ubbcode-body">7WSM using Alpha Type 3 or Type 4 AICS mags allowing COAL of 2.985".
wink.gif



I too would be interested in the 7mm SLR and/or the Creedmoor should it ever materialize. </div></div>

Ugh.

No magnums.

Also, Alpha magazines are advertised to handle 2.985", but they don't actually. 2.950" is the actual practical maximum. I own 3 type 3's and 4 type 4's. I know.

In regard to the 284. I have an FN SPR chambered in the cartridge. It feeds from the aforementioned Alpha mags. Honestly, it is performing very well. However, I want to try another chambering, and in particular...

One that fits and works from AW magazines.
 
Re: Holy Grail of Short Action 7mm Cartridges...?

Let me add some more direction to the thread:

I was hoping to get into a technical discussion regarding case design and cartridge efficiency...what can be done to what existing cartridge to optimize it with a 162-175gr 7mm bullet, loaded to ~2.9xx"?

For example, in the 7mm Creedmoor, it has been found IMR8208xbr is the "go to" powder. I find that strange because I've personally found 8208 to be too fast for ~175gr bullets in 308. 7-08 seems to work best with H4350, but Varget works pretty well too. Seems to me like 7-08 could really use a powder in between H4350 and Varget.

So... It seems really odd to me the 7CM would actually want a FASTER powder than 308 prefers. That is telling us something, though I don't know exactly what.

Would that same "efficiency" translate over to the 7SLR, which would be really quite similar to the CM case?
 
Re: Holy Grail of Short Action 7mm Cartridges...?

I'd say 7 SLR.

One good FL sizing on a 7-08 case, and you're done. Good case form with more capacity over the creedmoor case. Plus, I'd like to see how one performs.
 
Re: Holy Grail of Short Action 7mm Cartridges...?

I'm really interested in this thread. I'm somewhat in the same boat for my next build. Right now I have a couple 6.5x47 Lapuas, a 308 and a .284 win on a long action. I have an extra Rem700 s/a with .473 bf that I need to figure out caliber, and leaning to another 7 something.
 
Re: Holy Grail of Short Action 7mm Cartridges...?

6dasher and don't look back ! That's what I'm doing now ! You have 284 ! The dasher is winning in all classes of shooting right now ! Zipping 105 Berger hybrid right at 3k and smoking accurate
 
Re: Holy Grail of Short Action 7mm Cartridges...?

I've often wondered how the 7mm CM or 7-6.5x47 Lapua would do.

Seems they would be interesting cartridges to mess with and x47L would likely benefit from H4350.
 
Re: Holy Grail of Short Action 7mm Cartridges...?

I'm liking my 7mm-08 AI so far just need to find enough time to stretch it's legs out past 200. I'm getting the 162's to 2900 out of a 22" tube, my OAL is a little hampered since I'm using the accurate mag that came with my Manners Mini Chassis and from what I understand there aren't many other options that will work.
 
Re: Holy Grail of Short Action 7mm Cartridges...?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: captain zeke</div><div class="ubbcode-body">6dasher and don't look back ! That's what I'm doing now ! You have 284 ! The dasher is winning in all classes of shooting right now ! Zipping 105 Berger hybrid right at 3k and smoking accurate</div></div>
A dasher more than likely won't ever be reliable enough in terms of feeding for match shooting. Anyway that has nothing to do with the original post. I made some 7SLR dummy rounds a while back and it seems that with a 162 amax you can seat them at about 2.950'' and be right at the neck-shoulder junction. With the 180 Sierra you could actually be around 2.890''. I like the idea of a 7SLR more than a 7CM as I think you could easily run in to donuts by necking up the 7CM.
 
Re: Holy Grail of Short Action 7mm Cartridges...?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: bward</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: captain zeke</div><div class="ubbcode-body">6dasher and don't look back ! That's what I'm doing now ! You have 284 ! The dasher is winning in all classes of shooting right now ! Zipping 105 Berger hybrid right at 3k and smoking accurate</div></div>
A dasher more than likely won't ever be reliable enough in terms of feeding for match shooting. Anyway that has nothing to do with the original post. I made some 7SLR dummy rounds a while back and it seems that with a 162 amax you can seat them at about 2.950'' and be right at the neck-shoulder junction. With the 180 Sierra you could actually be around 2.890''. I like the idea of a 7SLR more than a 7CM as I think you could easily run in to donuts by necking up the 7CM. </div></div>

If you still have those 7SLR dummy rounds, could you measure the loaded neck diameter? Perhaps with several different headstamps? Perhaps even with a peice of Lapua brass?

...I'm pretty serious about having a reamer cut and need to figure out the chamber's neck dimension...
 
Re: Holy Grail of Short Action 7mm Cartridges...?

I made the 180 sierra round out of 243 win brass so I don't think you would want to use that neck measurement. I found the 162 amax round that was made from Lapua 308 palma brass. It measured .3165. I would be cautious of using Lapua brass in the SLR unless you are willing to turn your necks since it has been shown to create fairly severe donuts since it has different neck and shoulder thicknesses.
 
Re: Holy Grail of Short Action 7mm Cartridges...?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: bward</div><div class="ubbcode-body">I made the 180 sierra round out of 243 win brass so I don't think you would want to use that neck measurement. I found the 162 amax round that was made from Lapua 308 palma brass. It measured .3165. I would be cautious of using Lapua brass in the SLR unless you are willing to turn your necks since it has been shown to create fairly severe donuts since it has different neck and shoulder thicknesses. </div></div>

Out of curiousity, what is the measurement on the 243 one?
 
Re: Holy Grail of Short Action 7mm Cartridges...?

I couldn't find it. I'm doing a bunch of work on my reloading room so shit is piled all over the place. Just from past experience with Lapua vs. Winchester brass I'mm going to guess about .002 smaller. If I find it I'll send you a PM. I made those about 3 months ago when I was thinking about barreling my AW to 7SLR.
 
Re: Holy Grail of Short Action 7mm Cartridges...?

I think the 284 fits the bill nicely. If you use alpha mags you can load them out long enough, and it has plenty of horsepower to shoot anything up to the 180's well. In my experience, you can get around 150fps more out of the 284 than with the 7mm-08 out of any given bullet weight. I had to decide which 7mm I wanted to use (didn't want a magnum, but I was building on a long action), and I went with the 284 for these reasons, and the fact that it uses the same types of powders as my 300WSM (Reloader 17 is a godsend for the 284).
 
Re: Holy Grail of Short Action 7mm Cartridges...?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: rusty815</div><div class="ubbcode-body">I think the 284 fits the bill nicely. If you use alpha mags you can load them out long enough, and it has plenty of horsepower to shoot anything up to the 180's well. In my experience, you can get around 150fps more out of the 284 than with the 7mm-08 out of any given bullet weight. I had to decide which 7mm I wanted to use (didn't want a magnum, but I was building on a long action), and I went with the 284 for these reasons, and the fact that it uses the same types of powders as my 300WSM (Reloader 17 is a godsend for the 284). </div></div>

Kinda curious if you're going long action if you considered going 280 AI over the 284?
 
Re: Holy Grail of Short Action 7mm Cartridges...?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: nortex</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: rusty815</div><div class="ubbcode-body">I think the 284 fits the bill nicely. If you use alpha mags you can load them out long enough, and it has plenty of horsepower to shoot anything up to the 180's well. In my experience, you can get around 150fps more out of the 284 than with the 7mm-08 out of any given bullet weight. I had to decide which 7mm I wanted to use (didn't want a magnum, but I was building on a long action), and I went with the 284 for these reasons, and the fact that it uses the same types of powders as my 300WSM (Reloader 17 is a godsend for the 284). </div></div>

Kinda curious if you're going long action if you considered going 280 AI over the 284? </div></div>

I don't like AI's, I never did, so to me it was between the regular 280 and the 284, and I just felt the 284 fit me better, one of my main criteria was that I can use RL-17, and the 284 loves the stuff.
 
Re: Holy Grail of Short Action 7mm Cartridges...?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: rusty815</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: nortex</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: rusty815</div><div class="ubbcode-body">I think the 284 fits the bill nicely. If you use alpha mags you can load them out long enough, and it has plenty of horsepower to shoot anything up to the 180's well. In my experience, you can get around 150fps more out of the 284 than with the 7mm-08 out of any given bullet weight. I had to decide which 7mm I wanted to use (didn't want a magnum, but I was building on a long action), and I went with the 284 for these reasons, and the fact that it uses the same types of powders as my 300WSM (Reloader 17 is a godsend for the 284). </div></div>

Kinda curious if you're going long action if you considered going 280 AI over the 284? </div></div>

I don't like AI's, I never did, so to me it was between the regular 280 and the 284, and I just felt the 284 fit me better, one of my main criteria was that I can use RL-17, and the 284 loves the stuff. </div></div>

Understandable, most don't seem to like the AI stuff but with the Nosler SAAMII standardization of it and availablity of formed brass there has been a good bit more intrest
 
Re: Holy Grail of Short Action 7mm Cartridges...?

I think you would like the slr case. A friend of mine is runnning the 6slr and it has proven to be very easy to work with. It stands to reason that necking the case up to 7mm would make it even more user friendly.

If you're technically minded, the slr design stands up to scrutiny.
 
Re: Holy Grail of Short Action 7mm Cartridges...?

Since the 6SLR uses the 243 as a parent case couldn't one use the 7mm-08 for a 7SLR to avoid donuts when sizing?
 
Re: Holy Grail of Short Action 7mm Cartridges...?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: KYS338</div><div class="ubbcode-body">7mm Creedmoor </div></div>

Why do you advocate 7CM over any of the others, particularly 7SLR?
 
Re: Holy Grail of Short Action 7mm Cartridges...?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: nortex</div><div class="ubbcode-body">Since the 6SLR uses the 243 as a parent case couldn't one use the 7mm-08 for a 7SLR to avoid donuts when sizing?</div></div>
Same reason you can get donuts when necking up 243 to 260. You are turning part of the thicker shoulder into the neck, thus creating the donut.
 
Re: Holy Grail of Short Action 7mm Cartridges...?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: bward</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: nortex</div><div class="ubbcode-body">Since the 6SLR uses the 243 as a parent case couldn't one use the 7mm-08 for a 7SLR to avoid donuts when sizing?</div></div>
Same reason you can get donuts when necking up 243 to 260. You are turning part of the thicker shoulder into the neck, thus creating the donut. </div></div>

The creator of the 6.5SLR at 6mmar.com specifically states he prefers starting with 243 brass.

Thoughts on that?
 
Re: Holy Grail of Short Action 7mm Cartridges...?

.284 or .284 shehane is really growing on me, even in a short action. shooting side by side with my la .284 with 175 smks against a sa .284 shehane with 162 class bullets, i'm not seeing as much advantage as i once thought i would with the la.
 
Re: Holy Grail of Short Action 7mm Cartridges...?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: turbo54</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: bward</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: nortex</div><div class="ubbcode-body">Since the 6SLR uses the 243 as a parent case couldn't one use the 7mm-08 for a 7SLR to avoid donuts when sizing?</div></div>
Same reason you can get donuts when necking up 243 to 260. You are turning part of the thicker shoulder into the neck, thus creating the donut. </div></div>

The creator of the 6.5SLR at 6mmar.com specifically states he prefers starting with 243 brass.

Thoughts on that?</div></div>
I believe that's because he prefers to use Winchester brass because of it having similar neck and shoulder thickness. Since Winchester makes 7-08 brass I would think a 7 SLR would be better off starting with it. However I do see your point about him liking to neck up 243 brass as opposed to necking down 7-08.
 
Re: Holy Grail of Short Action 7mm Cartridges...?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: bward</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: turbo54</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: bward</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: nortex</div><div class="ubbcode-body">Since the 6SLR uses the 243 as a parent case couldn't one use the 7mm-08 for a 7SLR to avoid donuts when sizing?</div></div>
Same reason you can get donuts when necking up 243 to 260. You are turning part of the thicker shoulder into the neck, thus creating the donut. </div></div>

The creator of the 6.5SLR at 6mmar.com specifically states he prefers starting with 243 brass.

Thoughts on that?</div></div>
I believe that's because he prefers to use Winchester brass because of it having similar neck and shoulder thickness. Since Winchester makes 7-08 brass I would think a 7 SLR would be better off starting with it. However I do see your point about him liking to neck up 243 brass as opposed to necking down 7-08. </div></div>

That's what I was thinking just wasn't sure if that is the route that would be taken if one wanted to go to the 7SLR. It at least to me seems the easiest.
 
Re: Holy Grail of Short Action 7mm Cartridges...?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: turbo54</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: KYS338</div><div class="ubbcode-body">7mm Creedmoor </div></div>

Why do you advocate 7CM over any of the others, particularly 7SLR? </div></div>

Ease of loading, finding loading components is simple, barrel life is great, 2850 fps and up can be achieved depending on barrel length and twist. I shot a mild load thru mine and was getting 2860.

Its just a cool caliber.
 
Re: Holy Grail of Short Action 7mm Cartridges...?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: KYS338</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: turbo54</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: KYS338</div><div class="ubbcode-body">7mm Creedmoor </div></div>

Why do you advocate 7CM over any of the others, particularly 7SLR? </div></div>

Ease of loading, finding loading components is simple, barrel life is great, 2850 fps and up can be achieved depending on barrel length and twist. I shot a mild load thru mine and was getting 2860.

Its just a cool caliber. </div></div>


I second the 7mm Creedmore. Just because I want to see someone else shooting it so I can get more data before I decide if I need one.

What length barrel/twist/bullet weight are you using to get 2850 fps? Any load data out there that I could look through?
 
Re: Holy Grail of Short Action 7mm Cartridges...?

What is a 7SLR? I thought I remember seeing some info on it before but I thought it was a ling action cartridge, I guess not? I am interested in another 7mm something too, my gunsmith and were talking about it earlier tonight actually.
 
Re: Holy Grail of Short Action 7mm Cartridges...?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: lencomatt</div><div class="ubbcode-body">What is a 7SLR? I thought I remember seeing some info on it before but I thought it was a ling action cartridge, I guess not? I am interested in another 7mm something too, my gunsmith and were talking about it earlier tonight actually. </div></div>

7SLR is theoretical at this point. The concept is to neck up a 6.5SLR, which is actually a necked up 6SLR.

what's a 6.5SLR?

It's a 243/260/708/308 wildcat, though a simple one: http://6mmar.com/65_SuperLR.php
 
Re: Holy Grail of Short Action 7mm Cartridges...?

I would think that a 7 Creedmore, 7 Competition Match, 7 SLR would all be in the same neighborhood in case volume and potential velocity.

All are intriguing, and should produce similar results, especially with a mid-level projectile, as in 162-175 gr, from a AI or AW magazine.

Jeffvn
 
Re: Holy Grail of Short Action 7mm Cartridges...?

I have stated in some other threads that I am going to do a 7mm CM. I have the dies, and reamer on order. Both should be showing up in a week or two. It will be run in a DTA. The blank I have is a 1-8" twist.....the reason for this is that if the 7 CM doesn't live up to people's boasts, I intend to re ream to 7 RSAUM and run the heavy 180's and future 195's.

I intend to give unbiased results and post them all up. If anyone could give some load starting points with the 162s and 8208, I'd appreciate it.

Ty
 
Re: Holy Grail of Short Action 7mm Cartridges...?

How similar is the ballistics of the 7-08 vs the 7CM if they both are in a s/a and running the 162 Amax?
 
Re: Holy Grail of Short Action 7mm Cartridges...?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: mdesign</div><div class="ubbcode-body">How similar is the ballistics of the 7-08 vs the 7CM if they both are in a s/a and running the 162 Amax? </div></div>

It comes down to who got "lucky" with a faster barrel.

The useful capacity of them when both loaded to SA constrictions puts the water capacity within <1.0gr making it a +/-0.3gr load difference. Performance is pretty much identical.
 
Re: Holy Grail of Short Action 7mm Cartridges...?

Bohem, welcome. Was wondering how long before you'd join in.

What's your take on 7SLR?
 
Re: Holy Grail of Short Action 7mm Cartridges...?

If the AI mags will take up to 2.950" then the 7mm-08 would be your best choice. Or 7mm-08 AI.

The whole concept of this thread brings to mind quite a number of cartridges from the silhouette world. Now that we have uber high BC bullets in 7mm this could be an 'ultra light weight' 1k gun. Maybe not super competitive, but better than the .308 still.

Those are:
7mm TCU - (700 yd only)
7x30 Waters
7mm International Rimmed
7mm BR (I'm working on building one)
7mm International
7mm IHMSA
7mm/6XC
7mm Creedmoor
7mm Creedmoor IMP (30 deg. shoulder to 45 or anywhere in between)
7mm-08
7mm-08 IMP (20 deg. shoulder to 45 or anywhere in between)
7mmx53 (Belgian/Argentino necked down to 7mm)
7mmx53 IMP (20 deg. shoulder to 45 or anywhere in between)
Norma Makes great brass for these and you can load the 180 Bergers in them and not go too short. You are taking up case space though.
Now for the ones, that go faster but limited to 1k because of bullet weight/depth
7mm/6.5x55
7mm/6.5x55 IMP.
7x57
7x57 Imp

The last four configurations can seat a Sierra and I'm pretty sure a Berger 168 inside your magazine requirement length. And for Brass, Lapua and Norma both make excellent brass for those cartridges. Winchester makes (or at least made) good quality brass in both as well.

The last option is kind of iffy in a short action, but can be done. Turn down a .280 case to 2.350". There is a die to then form a 40 deg. shoulder from the 20 degree shoulder. That difference gets you back to almost .28 on the neck length. From that you can load a standard ogive .7mm 140 gr. bullet. Which from that case will get you to 1k at standard atm.

The single best performer of all of them is the 7mm/6.5x55 Ackley improved. You can safely load a 180 Berger to magazine length in that, you can't in a x57 case. You will have access to as good of brass as you wish in the Lapua 6.5x55. Remember to turn the heads down or open your bolt face as Lapua case heads for 6.5x55 are .480" not .473". At least they used to be, I don't know now.
 
Re: Holy Grail of Short Action 7mm Cartridges...?

We seek the same thing bro
First building on a short action is something i will not do again, thou my defiance action is actually a medium length action.
I have yet to contact GEO on this as i just ordered another 6.5 barrel, anyway he did an improved 6mm Rem i believe CooperCreek does brass. It has the right case cap and will run from a short action, i dont think the 162Amax is much longer than a 115DTAC.
So if it can run from a short action pushing a 115dtac should work equally as well re OAL for 162amax, difference in bullet length is .010.
Actually a 6.5x55 AI necked up would work equally as well IMHO
I may just buy a spare bolt with a mag face n run 7saum and be done, outside the bolt face issue it will work like a charm
 
Re: Holy Grail of Short Action 7mm Cartridges...?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: bohem</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: mdesign</div><div class="ubbcode-body">How similar is the ballistics of the 7-08 vs the 7CM if they both are in a s/a and running the 162 Amax? </div></div>

It comes down to who got "lucky" with a faster barrel.

The useful capacity of them when both loaded to SA constrictions puts the water capacity within <1.0gr making it a +/-0.3gr load difference. Performance is pretty much identical.</div></div>

While I definitely do agree with luck in a faster barrel blank, I don't totally agree with the rest. Here is why:

Everyone agrees that a 260 is faster than a 6.5 CM. I think this is the reason that everyone THINKS that the 7-08 will be equal if not faster than a 7 CM. The problem is when we try the same cases with 6mm. Everyone agrees that the 6 CM is faster than the 243 Winchester. How does this happen? I think it is due to the way that the cases deal with the powder and the bullet.

That is why I think there maybe something to do with the guys claiming 2900 with a 162 in the 7CM. They found the ideal powder in IMR 8208 XBR.

However, some guys refuse to admit when they make a mistake and so they are committed to their purchase (classic Ford vs Chevy gas milage argument) so they embellish the facts. Having buddies that turn barrels for me and work for whiskey makes my commitment only reamer, dies, and Glenlivet. A small price to pay for an experiment that if failed will turn into a 7 SAUM.

We shall see.

Ty
 
Re: Holy Grail of Short Action 7mm Cartridges...?

I have messed with the 708 and in aw mags and it feeds great. The key to getting good mag feeding with aw mags is to make sure your cartridge has similar body taper to the 308 case and to give your rounds enough room so the tips don't drag and cause misfeeds.

I know from experience the 243ai doesn't feed well which means the 708ai won't either and the 7 creedmoor may or may not 100% reliable.

If you are looking for ultimate in reliable feeding i vote 708, if you want top performance/reliability combo i would vote the 7 slr.

<span style="color: #CC0000">I can tell just from your previous experiments the 708 won't do it for you so you might as well get it over with and order the 7mm slr. you can probably just order 6.5slr fl neck bushing sizing die and replace the bushing and expander and be good to go seating with the standard 708 die.

DO IT!!!</span>
 
Re: Holy Grail of Short Action 7mm Cartridges...?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: TeamSendIt</div><div class="ubbcode-body">I have messed with the 708 and in aw mags and it feeds great. The key to getting good mag feeding with aw mags is to make sure your cartridge has similar body taper to the 308 case and to give your rounds enough room so the tips don't drag and cause misfeeds.

I know from experience the 243ai doesn't feed well which means the 708ai won't either and the 7 creedmoor may or may not 100% reliable.

If you are looking for ultimate in reliable feeding i vote 708, if you want top performance/reliability combo i would vote the 7 slr.

<span style="color: #CC0000">I can tell just from your previous experiments the 708 won't do it for you so you might as well get it over with and order the 7mm slr. you can probably just order 6.5slr fl neck bushing sizing die and replace the bushing and expander and be good to go seating with the standard 708 die.

DO IT!!!</span> </div></div>

That's good feedback in regard to AW feeding reliability.

That's also very insightful of you in regard to the 7SLR!

I'm about 95% on giving it a go... I'm trying to think through the particulars of it before pulling the trigger.

My die plan for 7SLR would be to buy the pre-existing 6.5SLR dieset and a 7mm seating stem from Redding. I think I'll have to hard-bore the sizing die(s) though, so the 7mm neck can pass through to make it to the bushing. I had to do that for my Forster 6.5-284 bushing/bump die to work with "straight" 284. In regard to the expander ball - I ditch those anyway, and always use a sinclair expander mandrel, so it's a non-issue.

Part of me would like to slightly "improve" the 7SLR by changing the body taper to match the Creedmoor cartridge(s), but then there would be fireforming and custom dies required, which is kind of a pain. I don't hate the concept of fireforming, but still, it's better to avoid it when possible.

I'm still trying to figure out what it is about the 7CM that allows it to use such a fast powder? 8208 is not a suitable powder for a 708 to hit top velocities in a 708...yet 7CM and 708 are very similar overall.

So will the 7SLR act like the 7CM with a little bit more horsepower?? Or, will the 7SLR act just like a 708?

I guess if I try it and don't like it, I could use the barrel as a replacement for my 284 when it shits the bed...

If I wasn't opposed to buying/paying for Lapua brass (for tactical rifles, anyway), I'd be looking closer at the aforementioned 7mm-6.5x55 Improved cartridge. That looks to have some promise. It's also the cheapest Lapua headstamp, I believe.
 
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