Ol'Kirby has an XP of mine now making a LR handgun but seeing some of the results fellas are posting about APS guns has me interested in the next project already!! My interest for this go-round is in the 270AM. Correct me if I am wrong on any of the following assumptions
The 270AM is based from the 300 RUM case?? Whereas the .277AM is based on the 338 LM case which is nearly too large for the Rem or Savage action.
It will fit/feed from any standard magnum length action...Rem 700, Savage three digit action (112, 116, etc)??
A 30" barrel would be plenty-o-tube for the 270AM??
I have one of the 270AM's, I absolutley love the gun. I can tell you that I will never not own a 270AM. For simple power, accuracy, and ease of loading it is a awesome cartridge.
The 30" bbl is great and optimal I imagine. I have a fairly heavyweight bbl but I am gonna have it re-barreld after this fall to something similiar to Kirby's sporter weight gun.
I used a Savage action in mine. DIes come from Kirby, or at least that is the easiest way I know to get them. The 277 AM is a pwerhouse but its only downfall is the added difficulty in prepping brass, this is a trade off for added case life. I think 4 firings with full tilt loads is probably close to done for the rem brass.
With the 270AM all you do is neck down 7mm RUM brass to 270 and leave about 1/4 of the neck unsized for a crush fit, fire and BAM, you got AM brass. The 277 requires several stages of necking down and additional annealing, I think. The trade off is good when you figure in the added brass life and edge in power, just kinda a pain.
I guess I cant say it is too much of a pain since I am fixing to have to do it for the 7mm AM anyway!!!
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I would like to add that 30" of barrel is not a requirement. I recommend at least 27" of barrel length but for a walking big game rifle, this will work. You will drop around 30-32 fps per inch under 30" down to 27". Is this enough to worry about, personally I do not believe so but I also load my 270 AM to a relatively mild 3275 fps with the 169.5 gr ULD RBBT. The boys on here that have my 270 AM are getting up to 3400 fps with the same bullet.
A shorter barrel length will easily be capable of the load level I am using and I have proven this load and velocity out to 2000 yards with consistancy and taken rock chucks with one shot kills out to just shy of 1250 yards.
The 270 AM can be loaded in either 7mm RUM or 300 RUM cases. I have seen a few lots of 7mm RUM brass that had a headspace measurement that was a bit less then it should be. As a result, initial fireforming will cause some minor case stretching. After fireforming this is a non issue.
I tried some 300 RUM brass and just necked the case neck down until the round would just snuggly fit in the chamber. This took care of the initial case stretching. Again, its not a real problem but using 300 RUM cases eliminates all case stretching when sized properly for fireforming loads. IT can still be formed by just using the 270 AM FL die and no annealing is needed either.
The 277 AM is much more involved to form cases. Only need a Redding Comp Bushing neck sizing die in 338 Lapua and a set of four step down bushings but it is an added cost. Performance advantage is 75 to 100 fps. As Lerch mentioned the main advantage is brass quality and strength.
The 277 AM also requires the use of an H-S Precision DM system for a repeater when chambered in a Rem 700 receiver. Works beautifully but there is the added cost as well as the added cost to the bolt for the larger round.
The only thing I would like to correct is that the 270 AM will not feed though the long action Savage receivers. The shoulder diameter is to wide to allow it to be pressed through the mag box lips. All of the Savage rifles I build chambered for the Allen Magnums are single shots.
I also remove the barrel lock nut and fit the barrel in the same fashion as a Rem 700 for added strength and safety.
If you want alot of performance in a wildcat that is no harder to load for then a 7mm RUM or any other factory round. The 270 Allen Mag is very hard to beat.
Add to that the new 185 gr ULD RBBT that is due out this summer from Wildcat Bullets and it will put this round in the same or nearly the same class as the 7mm Allen Mag loaded with the 200 gr ULD RBBT!!!
Not only that, but you also have the option to rip the 140 gr accubonds out at 3625 fps in a 30" barrel. Now for a 500 yard deer and pronghorn rifle, that trajectory is very hard to beat!!! For longer range the lighter bullet can not compete with the heavy wildcats but for moderate ranges, they are the definition of flat shooting!!
Richard Graves makes some 120 gr Bonded Core HPFB bullets that I have been tempted to order in and see how fast they will fly. I have driven 130 gr BTs to well past 3800 fps so who knows with the 120 gr.
All this said, I think your really just playing with the 270 AM unless your throwing at least 150 gr of bullet out there and the 169.5 gr ULD RBBTs are so impressive its hard to justify any other bullet besides simply testing for fun!!
I supply dies for all the rifles I ship out if my customers want. If they want to get their own that is fine with me but that can be a hassle!!
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Home of the Allen Magnum, Allen Xpress and Allen Tactical Wildcats and the Painkiller Muzzle brakes.
BB...single shots are my favorites! All I've hunted with for the last 10 years are T/C Contenders, Savage Strikers (can be a repeater but I feed single shot)and XP-100's. In the rare occurance that I have carried a long gun it has been fed single shot due to OAL.