Idea for a new cartridge: 7mm Practical; 180 VLD

[stiletto raggio]

I have been researching options for an upcoming build in .284. I really wanted to be able to use a short action, but 162s are the heaviest bullets I can load to mag length without severely encroaching on powder capacity. .284 loads pushing 180 VLDs are usualy loaded at 3.1-3.2 inches OAL while max standard length, even for the Alpha mags, is 2.985.

It occurred to me that a WSM case could be cut back about .4 and given the same shoulder and neck as the standard case (perhaps even a slightly longer neck) and retain roughly the same powder capacity as the .284. I'd call it the 7mm Practical. This would allow the long VLD bullets to fit in standard-length magazines while retaining enough powder to get the heavy bullets in the 3000 FPS range with long target barrels but with far less barrel wear than a WSM. Short, fat cases are in vogue (hence the WSM family) and have a reputation for great internal ballistics. I am sure some wildcatter or another has tried this, but I think the concept is sound.

The 7mm seems to be the new 6.5 in terms of interest for practical and F-Class shooting, and this "compromise" would have superior ballistics to the .260/6.5CM/6.5x47 without the barrel-burning of the 7WSM. The only issues I could predict without having the ability to actually fabricate and try these cases out is that they might have some feeding issues.

Anyone want to weigh in on the practicality of this concept? I am not in a position to give this a try right now so I will likely end up with a long-action .284 to get the same ballistics, but the prevalence of short-action DBM and magazines combined with improved ballistics and barrel life would seem like a winning combination.

 

[Adam B]

Re: Idea for a new cartridge: 7mm Practical; 180 VLD

why dont you run a 7m08AI?

 

[ranger1183]

Re: Idea for a new cartridge: 7mm Practical; 180 VLD

7mm Remington SAUM.

http://www.accurateshooter.com/cartridge-guides/7mm/

 

[BobinNC]

Re: Idea for a new cartridge: 7mm Practical; 180 VLD

.284 Win 66 grains CC Case length 2.17
7mm WSM 81 grains CC Case length 2.10

7mm SAUM 74 Grains CC Case length 2.035

So basically your reinventing a shorter 7mm SAUM. Are you aware that Seekins Precision makes a WSM DBM system that allows 3.14" MAX COAL. It does not use AICS mags, however.

None of this is to deter you from your quest to build a better Short Mag. Just wanted you to understand your options.

Bob

 

[bohem]

Re: Idea for a new cartridge: 7mm Practical; 180 VLD

7mm WSSM?

 

[ranger1183]

Re: Idea for a new cartridge: 7mm Practical; 180 VLD

That is some seriously short, fat brass. I hope you figure out a way to make it feed reliablely.

 

[Clark]

Re: Idea for a new cartridge: 7mm Practical; 180 VLD

7mmRemMag, 70 gr Re22 180 gr VLD moly 3.48" jammed into lands, 26" barrel, 3025 fps average.

I killed 3 mule deer with this in 2010.
Flat shooting, but still needs compensation for 500 yard shots, just not much.

 

[Bacarrat]

Re: Idea for a new cartridge: 7mm Practical; 180 VLD

Its been proven that that 7WSM or SAUM will worth without a problem and get a decent amount of barrel life (around 3k rounds. I am currently pushing 182gr Bergers at 3000 FPS with a 25" barrel with the bullets seated in a AICS mag. So why the need to reinvent the wheel?

 

[stiletto raggio]

Re: Idea for a new cartridge: 7mm Practical; 180 VLD

Bacarrat,

I am not doubting that there are barrels going strong at 3k rounds, but for every guy who can say that, several more are having to replace barrels at 1000-1500. I don't know enough to pin down the variables, but everything I read says that large powder charges relative to bore size (ie, being "overbore") is the culprit for fast-burning barrels. A smaller powder charge certainly isn't going to speed up barrel wear and I think the savings in powder and barrels more than offsets the need for a few more inches of barrel.

Ranger,

That looks very close to what I had in mind. I read that early on some people had trouble even getting the WSM to feed right out of AI mags, but that seems to have been rectified. Is it a lack of taper at the shoulder or in the case body, or it is just the sheer width of the case that causes trouble? I know putting much taper in the case would cause its own set of problems for mag-feeding, but I have not worked with a WSM myself so I haven't seen the associated problems.

Bob,

I checked out the Seekins DBM and it looks really nice. I am not sure I want to go with a completely proprietary magazine system and Seekins only makes it for the 700 (though I am sure it works with similar-footprint customs, too).

Based on what I am seeing about the .284--especially with RE17--I don't think the cartridge even needs as much powder as the SAUM holds. Again, I am not in a position to put this thing into production or even make wildcat cases, but I think if it can be made to feed reliably, it will offer some benefits.

I appreciate the feedback, even the "I have no idea why you would do that" type. I was really hoping to find a suitable cartridge out there, but the WSSM cases are way too small and most of the full short-action cartridges are either under-capacity (.308) or really overbore (WSM) and neither give a solution.

 

[Rich Coyle]

Re: Idea for a new cartridge: 7mm Practical; 180 VLD

If you go with a .378 Weatherby case you can make it extremely short and still have a huge powder capacity. I did one and used a short action Remington. The case was shortened to 2 1/4 including a 1/4" neck going down to a 45 degree shoulder. It held the same amount of powder as a .300 Weatherby.

I fired 130 Barnes at 3,300 feet per second and got about ten loads per case. In fact I don't remember ever having a case that would not hold a primer.

 

[stiletto raggio]

Re: Idea for a new cartridge: 7mm Practical; 180 VLD

OMN,

That is pretty impressive. How long did the barrel last?

I am sort of fixated on barrel life since it varies so dramatically depending on the cartridge and is a major factor in the cost of actually shooting the rifle.

 

[Rich Coyle]

Re: Idea for a new cartridge: 7mm Practical; 180 VLD

Long about 500 rounds I took it to a guy for some more work. When I went ot pick it up..... He looked at that large case in that Remington action and cut it in two right in front of the trigger gaurd<span style="font-size: 11pt"><span style="font-weight: bold">!</span></span> He said it was dangerous.


I have since learned longer necked cases extend barrel life compared to shorter necks.

 

[bohem]

Re: Idea for a new cartridge: 7mm Practical; 180 VLD

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Old man now</div><div class="ubbcode-body">Long about 500 rounds I took it to a guy for some more work. When I went ot pick it up..... He looked at that large case in that Remington action and cut it in two right in front of the trigger gaurd<span style="font-size: 11pt"><span style="font-weight: bold">!</span></span> He said it was dangerous.


I have since learned longer necked cases extend barrel life compared to shorter necks. </div></div>

The guy cut your receiver in half?

 

[Bacarrat]

Re: Idea for a new cartridge: 7mm Practical; 180 VLD

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: stiletto raggio</div><div class="ubbcode-body">Bacarrat,

I am not doubting that there are barrels going strong at 3k rounds, but for every guy who can say that, several more are having to replace barrels at 1000-1500. I don't know enough to pin down the variables, but everything I read says that large powder charges relative to bore size (ie, being "overbore") is the culprit for fast-burning barrels. A smaller powder charge certainly isn't going to speed up barrel wear and I think the savings in powder and barrels more than offsets the need for a few more inches of barrel.

</div></div>

If you want benchrest accuracy and not chasing lands then yeah, maybe. I know of several people that 2500-3000 rounds through their 7WSM before rebarreling. My old barrel went 3300 rounds of nothing but moly 180gr Bergers going 2950+fps. I think George at GAP was close to 3k, Jered at APA went 2700ish rounds and I think Jacob or Frank has close to 3K rounds through theirs, not sure they rebarreled yet.

There is a compromise on performance vs barrel life. Especially with the 7s. You are not going to get magnum performance without going to a magnum. If I have to rebarrel every other year, then so be it. If I really cared about barrel life, I would shoot a 223 or a 308, but then again, both of those have mediocre ballistics. lol That is why I am thinking about yanking my 308 barrel off and going with a 6mm. I like shooting lasers!

 

[9H_Cracka]

Re: Idea for a new cartridge: 7mm Practical; 180 VLD

Alex, Dtubb told me he was going to produce exactly what you described here but in 6.5 mm. He also told me he was developing a new 150 gr 6.5 mm bullet to go with it.

That was going on 2 years ago; it was supposed to be out late 2009. Didn't happen.

To be completely honest, once you've spent time with a LA, you'll throw rocks at an SA. SA is a bunch of hype. The LA gives you a lot more finger room under the scope for putting rounds in.

Yea mag feed makes it a non-issue, but why go through all these gyrations just to say it is an SA?

The custom actions are plenty stiff in an LA 700 footprint, and for stock remmy 700 actions just bed the first inch of the barrel (I do that anyway on my heavy barrel SAs) and it won't matter.

Stick with the 284 my friend.

 

[223ai]

Re: Idea for a new cartridge: 7mm Practical; 180 VLD

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Bacarrat</div><div class="ubbcode-body"> both of those have mediocre ballistics. </div></div>

You sure about that? Run the numbers on a 80 or 90 gr jlk in a straight .223 at 2950 and 2850 respectively...

 

[bigbeargos]

Re: Idea for a new cartridge: 7mm Practical; 180 VLD

I'm building 2 rifles in 7mm WSM and plan on shooting 180 VLD's in both. One for 1000 yard match and one for hunting. I'm utilizing 700 Remington L/A. I will be able to use the factory mag box and nothing custom to make the rounds fit. I believe a few others are doing the same for their builds. Would this be an answer to what you are trying to do?

 

[Bacarrat]

Re: Idea for a new cartridge: 7mm Practical; 180 VLD

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: JPipes</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Bacarrat</div><div class="ubbcode-body"> both of those have mediocre ballistics. </div></div>

You sure about that? Run the numbers on a 80 or 90 gr jlk in a straight .223 at 2950 and 2850 respectively... </div></div>

I did, that is why I shoot a 7WSM.

 

[Rich Coyle]

Re: Idea for a new cartridge: 7mm Practical; 180 VLD

<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: Old man now</div><div class="ubbcode-body">Long about 500 rounds I took it to a guy for some more work. When I went ot pick it up..... He looked at that large case in that Remington action and cut it in two right in front of the trigger gaurd<span style="font-size: 11pt"><span style="font-weight: bold">!</span></span> He said it was dangerous.


I have since learned longer necked cases extend barrel life compared to shorter necks. </div></div>

The guy cut your receiver in half? </div></div>

Yes<span style="font-size: 17pt"><span style="color: #FF0000">!</span></span>

 

[hexades1]

Re: Idea for a new cartridge: 7mm Practical; 180 VLD

Load .284 Win long i.e. around 3.15-3.25" and you are all set. The "I need/want to use short action" is a solution to a nonexistent problem. The longer action does not weaken the rifle or decrease to any relevant measure the accuracy oof the rifle n the field. We are talking about mag fed field rifles rigth ?

All M24s for example are LA even though they shoot 7.62 Nato which is a short action round. Still targets are hit at +1000m ranges.

My .284 Win duplicates 338LM trajectories out to 1500m easy. No muzzle brake needed, 4-5 pounds less weight on the rifle and a decent barrell life. 180 VLD or 175 MK are all you need. Lapua brass and Fed 210 primers. 215s were too fast and muzzle velocities actually decreased with them.

 

[Rich Coyle]

Re: Idea for a new cartridge: 7mm Practical; 180 VLD

TA,

You mentioned velocities went down when you used 215's. Have you tried other hot primers?

I found different primers give different velocities for no apparent reason.