7mm/300 lapua

[linksmechanic]

any gunsmith on here have experience with this cartridge? I have a limited amount of knowledge and just recently heard of it. What kind of performance could on expect with a 180 grain bullet? I would imagine you could build it on a 700 action. I meant 7mm/338 lapua.

 

[eddybo]

Not yet....but I just fnished making my seating die out of a barrel stub about 20 minutes ago, so maybe tomorrow I will get to shoot mine. It takes forever to run a reamer that size in a piece of steel. I am gaining more respect for the real smiths out there. I am planning on shooting the 180 bergers I will let you know how it goes.

 

[JeffVN]

Kirby Allen does something similar called the 7 AM.


7mm Allen Magnum - 338 Lapua Magnum parent case, necked down to 7mm and fireformed to min body taper and shoulder angle.

I suspect this beast is capable of launching the 180 bergers at speeds that can simply tear them apart - but they now have the thick jacketed 7mm 180s to handle such pressures - it sounds very interesting. I know Wildcat also makes some 7mm bullets that can handle these velocities.

enjoy

JeffVN

 

[linksmechanic]

Is it possible to rechamber a Rm chamber for this cartridge?

 

[ss7mm]

Kirby of APS, "Fiftydriver" on here, is the guy to get hold of. He makes the 7mm AM and I have one that I wouldn't part with. You can't believe what a 200 gr. Wildcat out of it can do at long range. Below is some info on it.

Best bet if you're interested is to contact Kirby at [email protected]. He will give you any info you want and ask any questions you might have.

7mm Allen Magnum[FONT=&quot]
[/FONT]338 Lapua Magnum parent case, necked down to 7mm and fireformed to min body taper and shoulder angle.[FONT=&quot]
[/FONT]140 gr.(3800 fps) up to 200 gr. ULD RBBT(.900 bc) 3200 to 3350 fps from 26" to 30" barrel lengths[FONT=&quot]
[/FONT]Designed for long range big game hunting up to and including elk and moose. Has been used effectively on elk out to 1300 yards and has also proven one of the most ballsitically potent rounds in use today including the 277 Allen Magnum and the 338 Allen Magnum. Has proven capable of ½ moa accurate out to 1000 yards and 1 moa accurate out to 2800 yards in good conditions.[FONT=&quot]
[/FONT]Appropriate powders: H-Retumbo, H-50BMG, H-870, H-US869, AA8700 and WC872

 

[linksmechanic]

I wonder if there is a way to get away from the fireforming. I figured you could just neck down a lapua case to 7mm but maybe not.

 

[ss7mm]

You could just go with a plain necked down version but the AM is soooo much fun.

If you were to decide to go the fireforming route, just remember that the fireforming rounds are very potent and fantastic long range practice. I've killed several animals with them.

You can also buy the already fireformed cases directly from Kirby so that eliminates you haveing to do any fireforming.

 

[Fiftydriver]

Capacity wise, the 7mm-338 Lapua has nearly identical case capacity to the 7mm RUM, within a grain or two in capacity. IF your going to stay with this class of capacity, you probably would be better with the RUM in a factory receiver.

Yes, the 7mm Lapua could be loaded to higher chamber pressure but the advantage would not be all that great over the RUM.

My AM is a dramatic change in the Lapua case. shoulder location is moved forward roughly 50 thou, shoulder angle sharpened and body taper set at min. Case capacity is easily 10% over the RUM or 7mm Lapua.

With any of these, your best served with heavy bullets. 160 is what I recommend as minimum to get these large capacity cases working consistantly. Heavier is even better. 180 grs are great, I have heard the 189 Caut bullets are very good also. The 200 gr ULD RBBT is the best I have used in my AM but only with the very slowest surplus ball powders.

 

[linksmechanic]

Thanks for the info, much appreciated.