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Discussion in 'Reloading' started by joe30007, Mar 21, 2010.
Been reading about this gun. What kind of loads are being used? What preformance does it get?
200 grain Wildcat bullets (high bc) @ around 3300 out of about a 30" bbl. 1/2 MOA or better @ 100 and if you do your part better than 1/2 MOA @ 1500 but you had best do your part. This is for an APS built 7mm AM.
W/160 SMKs Its even faster but not as much oomph way out there......
What powders are being used? Must be very slow ones.
Very Slow.......WC 870 and US-869.
Also, all powders are the only ones recommend for it, I believe. Powder bridging potential with stick powders, overbore case and steep shoulder.
The great thing about it is that it uses the Lapua case........
I shoot a 270 AM w/a 300/7mm RUM case.
Also only ball powders except for 7828ss with 277 bullets @ 150 gr and below.
Do u turn ur necks before r after necking down? Thanks
Don't turn necks at all as recommended by the builder...... Just fire form, using cream of wheat/corn meal, etc method) or just a bit reduced load with a bullet.
The fire form loads, with bullets, have been good enough or as accurate as worked up loads, for zeroing and some drop chart generation.
Full tilt loads are barrel burners so whatever method that is used should consider barrel live.
Barrel life expectancy of the 270 or 7mm AMs are possibly 1200 rounds. My 270AM is at almost 900 round count and still going strong. That is, with a 3 groove 8 twist Lilja barrel.
For a game hunting cartridge this would amount to several person's lifetimes......
I had my reamer made with a .315 neck so I will have to turn some
So, the reamer is actually for a 7mm-338 Lapua Improved........Not actually a 7mm Allen Magnum????
Its the same thing
Hmmmmmm, I would think that it could be designated as and loaded the same an Allen Magnum only if the reamer is ground to the APS design dimensions?
It doesn't seem to be like the "Edge" where the the 300 RUM is simply necked up to 338 and nothing else changed. And 338 RUM dies used to size 338 Edge cases.....
The 7mm AM is not the same as the 7mm-338 Lapua Improved. Performance is similiar but certainly not the same.
Also, the 1200 round barrel life is a bit optomistic. Possible but you would really baby the barrel and it would greatly depend on what bullet is being used. A thin jacketed match bullet would likely loose accuracy well before this point. A hard bullet such as a 160 gr Accubond or the heavier jacketed SMK in 175 gr weights can usually handle a worn barrel just fine.
I do not recommend fireforming with corn meal in a good barrel. Over time it WILL cause extra throat wear. This is why I set up to offer formed cases to my customers with 7mm AM rifles. My Dad is in charge of this and he charges $85 per 100 cases for labor and componants.
Just for everyones information, the 7mm AM reamers are not available to the public at this time. Again the 7mm-338 Lapua is very similiar but certainly not the same as the 7mm AM.
Performance size, in a 30" barrel length you can expect to see 3300 fps with the 200 gr ULD RBBT(bullets velocity ceiling), +3500 fps with the 175 gr SMK with a custom receiver designed for the Lapua(not Rem 700), and pushing 3600 fps with the 160 gr Accubond.
My personal light weight 7mm AM is one of my very early rifles built on a converted Rem 700 which I do not offer any more. That said, its currently driving the 175 gr SMK to 3450 fps.
Not to hijack this thread, but... How do you determine the difference in pressure handling ability between a Remington action and a custom? Does it take higher pressure to show the normal pressure signs when doing load development?. I'll start another thread for this discussion.
When I do load development with any of my wildcats based on the Lapua case, I do so using Norma brass. The reason being is that Norma brass is MUCH softer then the Lapua brass. In fact, I have found its very similiar to the same strength as remington RUM brass in that both will start to loosen primer pockets around the 65,000 psi level of chamber pressure.
When using this brass in a rifle based on a Rem 700 and chambered in 7mm AM, you will see primer pockets start to loosen at around 3450 fps or a bit more with the 175 gr SMK. In a full custom receiver, say BAT, Nesika, or my soon to be released Raptor, primer pockets hold solid well over this. WHY?
Brass fails, to some degree because it is not being supported well enough to prevent case stretching and case head expansion. What gives pressure signs is this case expansion. Thats why you get sticky bolt lift all things being equal in a rem 700 based rifle compared to a full custom that is much stronger. If the brass expands to much, you get sticky bolt lift and extraction, the more this case expansion is controled, that being by a stronger receiver, the less you will see pressure signs.
Does this mean you can run the presssures through the roof, certainly not, that is why I use the Norma brass for a base line in reading pressures. I load it up to where you just start to see some change in primer pocket fit and then switch over to the Lapua case and consider that load max and you will never see any problems when using the Lapua case.
The reason I do not recommend the Rem 700 anymore is not because it will not easily handle any sane pressures that the Lapua case should be loaded to, its simply because to the unexperienced or ego bound handloader, the Lapua case can support MUCH more pressure then any factory receiver should ever be loaded to. When loaded correctly, you will NEVER have a problem. I have loaded my lightweight 7mm AM very hot at times and I have used it for 7 hunting seasons now with no issues at all but I know its practical limits.
Many out there may not have that ability to "stop" before getting pressure signs. In all honesty, if you are getting pressure signs with the Lapua case, your WAY over where you should be playing!!!
If one runs the numbers on this, the conclusion is this has got be about the finest ballistics you can obtain in a sub 12 lb rifle. Holy moley.