Home Forums Hunting & Shooting Long Range Hunting Help me choose a 7mm Chambering......

At one point or another,we have likely run into a situation where pressure seemed too high and yet velocity was not up to par for the cartridge. Here we have "pressure",but not velocity equal to what is normal for the cartridge.I have seen this,and we even did the corrective work to the barrel, to bring velocties up to a more normal level...it was a PITA.

In about every instant,I have found that the answer to sub par velocities in a given case is......a larger case.

If you can't live without 3200 fps with a 130 gr bullet in your 270,then maybe you should buy a 270 WSM,and get the velocities easily......this has worked every single time I tried it.....and I spent a lot of time,components,barrels,and money trying to circumvent this basic rule. It can't be done predictably.

Hmmm, we're saying the same thing here, I think.

Let's try this another way- you said "In your example, the rifle making 3300 fps is running at considerably higher pressure than the one running 3100 fps." There is no question that the rifle that gets 3300fps is running higher pressure, but the question that I was answering, is "why?"

If both rifles are running the exact same load, then what accounts for the difference in pressure and velocity, if not for the dimensions of the chamber, throat, bore, etc?

Shooting Times West

Ifn the barrel's prior address was MT then I suspect it was a very good snag.
Some of the consideration comes down to the rifle action your using and how much hobby ya want. The Dakota would be great but pricey brass. The Ruger may be about the same price in the end-don't know for a fact.
I suspect a Lazzeroni firebird cartridge would fit and be a bunch of fun. Don't think it would be cheap but long range shooting rarely is.

To all the belted mag suggesting folks- ya missed the point.

I have a 7mm Dakota and I like it. I have bought most of my brass 2nd hand. Some new, some once fired. I have brass that has been shot 4 time and still in great shape. It seems to come up for sale from time to time here in the classifieds. I have bought 160 pieces here since 2009, enough to last a long time. I have not been able to get 3200 out of 160 bullets yet, mine has a Borden action, Lilja #4 barrel 26" lg. My bolt lift gets heavy at before I reach 3200. My hunting load is 160 NAB at 3120.
If I had it to do over again I would go with the 7 WSM probably and be happy at 2950 to 3050 with 160's. It depends on what velocity you are after and are willing to live with. I like my Dakota, just do not think I would do it again.

I have over twenty 7mm's and have built about every wildcat. The 7mm RUM eats barrels fast. I had two and throat errosion was swift. The 7mm stw and the 7mm Dakota have the best performance before getting into severe barrel burners. I like the 7mm Dakota best because the short case allows for seating the bullets out to the lands while still beeing able to feed through the magazine. Not much velocity difference between it and the 7 RUM. The 7 wsm is just to slow with the high bc bullets for me. The purpose is to get to long range with enough power to get the job done and the two best at that are the 7mm stw and 7 dakota before getting into a barrel eater.

I agree with this and would add the Mashburn in a wildcat because it is just like a Dakota,and made from easier to get and cheaper 300 WM brass.Bullet seating and cartridge length is similar to the Dakota as well.(You could fit the Mashburn in a 30/06 length action,but every standard M70 or M700 in the world is H&H length anyway,so no difference). I set the Mashburn up for 3.5-3.6 OAL.

I had the Dakota and it's nice;if it became a mainstream factory cartridge I'd be all over it again.In the meantime, the Mashburn will "do".

the Mashburn won't clean up the OP's 7/.300RCM chamber though.

How does the 7/.375Ruger compare for useable powder capacity ?

I think they'd be pretty close....the 375 Ruger might be a lot like the Dakota.

I know there is virtually no difference between a Dakota and a Mashburn.

Did we decide on the 7mm weatherby yet?

Always good...

But I would not want to build one with a 24" barrel,and depend on it to get any more velocity with a 175-180 gr bullet than a 7 Rem Mag built similarly,given that the two cartridges have about identical capacities.

No doubt some examples of rifles chambered for either cartridge will get a 175-180 gr bullet to over 3000 fps, but pressures would have to be pretty high,and vary rifle to rifle enough that I would not take a chance on a build....

I have noticed that the 7mm's of Dakota, Mashburn, and STW capacities do it all so much easier and routinely....this is confirmed over several rifles now, with velocities comfortably exceeding 3050-3100 fps with 175's and 180's,and from a variety of barrels....discussions of "fast barrels/slow barrels" being absent from the results.160's hit 3200 with little fanfare.

This is the reason, when I decided I wanted a rifle to do those things,I excluded the cases with capacities like the 7 Rem Mag,Weatherby,and WSM....all are too small for the job across the board IMHO.No substitute for capacity.

I think I'd go that way if I was going large.

700 WSM, it is doing well in the 1000 yard target competitions so there is a good chance your rifle would have good accuracy.

I have a 300 WSM in a M700 SPS and it feeds OK, sometimes getting the 3rd round down in the magazine is tight but can be done. Like some other M700s it is an accurate rifle.

The M70 short action is longer than the M700 short action so you could have a longer throat and load the bullets out farther for more powder capacity. Or an idea I have been contemplating in a future build, have a freebore throat built tight enough to help the bullet straighten itself before hitting the rifling.

Except you missed the point in the original question where the person explains that he has a barrel that is currently chambered as a 7mm RCM.

And the barrel length is only 23"...WSM or SAUM


W

Barrel lgth makes no difference in this case. The existing chamber WILL NOT clean up for conversion rechambering for a H&H based case. Magnum Man

Was referring to all the long action larger cases.. Seems a bit much with the slightest cleanup your into the 22" range...

W

I agree, not sure a 23 inch RUM would make much sense but a Dakota or Ruger might not be so bad. Then again it might be worth sticking with the RCM. All the rage over the 280AI, would be the same same.

Mashburn.....stop guessing....