Gunsmithing 7 SAUM free bore ??

[stenger]

Anyone have any experience with 7 SAUM and the proper amount of free bore with the 180 berger bullets? Going to do a short action build and I am trying to find information. Anyone know if it's possible to get the bullet up past the neck shoulder junction and still fit in a mag system. ?

Thanks

 

[chipsfan]

You going single shot or feeding from a mag?

Edited. I'm a dumb ass. I see you are going mag length

 

[squin]

I had PTG cut me a custom 7mm Rem SAUM reamer from a few dummy rounds I loaded using Remmy brass and 180 hybrids. My freebore is .054. I built this on a Bighorn short action that I had available and a Krieger 28" HV contour barrel. 2.96 to 2.97 is about max OAL using Alpha mags if you want to feed reliably without trimming meplats. Jump to the lands is about .015. The base of the bullet is seated into the shoulder. I don't think you will get the bullet out past the neck shoulder junction using a short action. I give up some case capacity to load the 180 Hybrids short at 2.96 OAL, but it has worked very well for me.

I found Magpro and N560 to be the best powders for this shorter load. I don't believe there is enough boiler room for 4831SC or H1000 with the shorter OAL. Once I found the MagPro and N560 worked so well I quit searching for a load using other powders. Velocity for 180 Hybrid loaded to 2.96 in front of 62 gr of MagPro gives about 2850 fps, 59.2 gr of N560 gives about 2900 to 2930 fps shooting suppressed. A long action gives you a lot more room to play with, but the short action does work.

 

[stenger]

I kind of figured a short action is to small to get the bullets out far enough

 

[bjay]

Im with squin on this.. robert(rws) built me one on short action i told him im only goin be shootin 180s.with the hybrids its abvious a lot of bullet body below shoulder and taking away case capacity.altho it does shoot great i was having problem with some powder being close to compress load.it gives preasure sign specialy with 4831sc. I switched to h1000 and rl25 and still cant get fps i wanted even with 30" barrel due to limited case capacity with 180s. My short action fb .054..i decided to sell the action and replaced it long action, now with long action fb 188 dont have the problem seating bullet to deep just to mag feed them.. i can stretch load to creat more case cap get the fps i wanted and accuracy still there.. the way i look at it if you want to shoot 162 amax and 175 smk short action is perfect. With the 180s vld or hybrids go with LA.. ULL BE GLAD!
Above photo in SA 30" barrel
Below in long action bighorn barrel set back to re chamber its now 29" getin 3050-3112fps with rl25 no pressure sign