Spanish FR-7 Barrel Twist?

[Denny Gibson]

I recently purchased a very nice FR-7 and am getting ready to make up some rounds for load development. I’ve searched high and low for the barrel twist rate on this rifle and found nothing so I thought I’d check the High Road. Does anyone know the answer?

 

[desidog]

IIRC, 4 groove barrel with 1:12 right twist, it's the same barrel as a CETME.

 

[Denny Gibson]

Desidog ... thanks! Getting ready to do some lower-recoil load development ... how comfortable would you be (considering it’s a small-ring receiver) with shooting full power loads? I shoot 41.5g IMR 4895 in my M1A ... should I limit powder charge to something less?

 

[Jim Watson]

What bullet weight? 41.5 gr IMR 4895 is below the Hodgdon starting load for a 150 gr .308. Looks like it would be about .300 Savage ballistics, similar to 7mm Mauser pressures.

 

[desidog]

"how comfortable would you be (considering it’s a small-ring receiver) with shooting full power loads?"

LOL. I'm not. That's why i sold my FR-7. I got an FR-8; and no worries.

I used gas checked cast bullets in mine, but it's been a few years and i don't recall the powder.

This is the stuff i mainly shot in my FR-7.

 

[Denny Gibson]

Jim ... are you looking at 30-06 data? I’ve been shooting 168gr in the M1A but will use 150gr for the FR-7 (and in the M1A in the future) ... My Sierra Manual says 38.5/42.8gr is min/max load for 168g and 40.5/45.2 for 150gr bullet. Actually, it looks like my M1A is about in the middle of the range for 168gr bullets. Since this is a small ring receiver with no secondary bolt locking lug I’m being a bit cautious ... I just don’t have a feel for a good place to stop. Maybe the way to look at this is on a velocity basis (pressure is potential energy that converts to velocity in a dynamic sense) ... if I could identify a safe max velocity for the FR-7 I could find a charge that would yield that velocity ... maybe I’m making things too complicated here?

 

[Denny Gibson]

Desidog ... thanks again! If I can get a little info on those cartridges I can get a pretty good idea of where to limit myself.

 

[Denny Gibson]

Oh ... those are practice rounds ... wasn’t familiar with these but I don’t think I can relate their performance to a normal cartridge ... it does say you were cautious! Since, in the end, I’m looking for a reduced recoil load (shooting 50m matches 80 rounds total would make shooting full power loads with this carbine a painful prospect even if it was safe to do so) ... so maybe the best approach is to start at the minimum and work up to a good shooting load staying as far away from the maximum published load as possible ... at 50m it shouldn’t require a particularly large powder charge ... thoughts?

 

[Jim Watson]

Denny,
I was looking at Hodgdon data for .308 Win.
Sierra is 1. pretty conservative but 2. do not give pressures.
Either way, a starting load would be all I would care to put in a Spanish Mauser conversion. What more do you need at 50 meters? Or 300; the old .30-06 International load was the 173 gr military match boattail at 2200 fps, hardly more than a .30-30.

 

[Denny Gibson]

Jim ... good point ,,, hopefully a charge not too far from the minimum will give decent results at 50m ... so I’m off to the range ... thanks!