PT&G custom 7mm SAUM reamer specs

[Tondar15]

Looking for some help/guidance/double checking on my approach for determining the specs for a custom reamer. I am building a 7mm SAUM on a Savage short action, planning to shoot the 168 Berger VLD's, mag fed.

I have ~500 pieces of Remington brass (unfired). I took 33 of them to FL size and then take measurements. Here is what I found:

Case length Avg. = 2.0273 (does this seem short? SAAMI spec is 2.035)
Case length St dev. = .0008
So if my sample of 33 measurements represents the population I set the overall length to Avg - 3*StDev = ~2.025 (This would be the maximum length I could use and ensure all cases are trimmed)

Neck thickness Avg. = .0158
Neck thickness StDev. = .00037
mean - 3*StDev = .0147 So max neck thickness of .0145 would ensure all cases are turned (I may just go to .014)

Maximum OAL for the magazine according to Alpha is ~2.985" I would probably stay less than or equal to 2.975"

I plan to load my dummy rounds then to 2.975". The question is at this length what should I specify in terms of distance into or from the lands? I think because I will hunt with this rifle I will not plan on jamming much into the lands due to the problems with extracting a live round. So should I specify at the max length to just touch the lands? be .005" off the lands? I could always single feed for competition and jam into the lands then. Thoughts?

Any thoughts on any of the above info?

Thanks
Tony

 

[Tondar15]

Another question:

After neck turning do I need to resize the necks with my bushing die before seating a bullet (this is for a dummy round)

thanks

 

[1967spud]

yes you do

 

[rcw3]

Tondar15

Please do not take offense, but there's a little more info there than perhaps is needed when you are thinking of setting up a reamer.

How about this:

1. Specify what you will have for your loaded neck diameter (since you are suggesting you will be neck turning) and then set the neck diameter of your reamer from there (you cannot go wrong around .003" over loaded neck diameter for a 7mm chamber).

2. Unless you know what dimensions your re-size die will resize your fired cases to, you are just guessing trying to dicker with the body dimensions, so you probably should just run with a Minimum SAAMI body for the reamer and head space.

3. For throating, you are not really clear what you want to do as I see magazine feed hunting and single load competition mentioned as intended uses. Bear in mind VLD's may shoot well jumping, and they may not, so I would not bank on jumping them and I would tend to stay short enough, if you can, to be in the lands .015" or so at a certain magazine length (i.e. a little shorter than your max mag length). You can typically always load the projectiles back in the case a little more, but you can't go any longer than magazine length if you are working out of a magazine.

Good luck!

Robert

 

[expiper]

Tondar-15....ask Kiff if .040" FB is close...I did some hillbilly math and came up with that as a working solution for your bullet/magazine combo......you picked a good bullet to push waaayyyy in ,because that particular (168 VLD) has a very short bearing surface compared to the 175-180 class of big uns that are becoming popular .....and the Hornaday 162's (A-max and the new HPBT match ) should work also,,,(I have shot em and they are VERY good bullets).....let us know what Dave at PTG comes up with....Roger

 

[lurcher]

I can email you a reamer print for a 7mm saum match reamer that might help if you wanted it. I am getting a barrel reamed at the moment with a short throat reamer. The print for that reamer was based off this print except the throat is shorter to feed out of a model 7 magazine (about 2.830 length I think) from memory. Unfortunately my friend who had this 2nd short throat reamer made has lost the print :

 

[Tondar15]

I can email you a reamer print for a 7mm saum match reamer that might help if you wanted it.

I'll send you a PM with my email address. Thank you!!

Tondar-15....ask Kiff if .040" FB is close...I did some hillbilly math and came up with that as a working solution for your bullet/magazine combo......you picked a good bullet to push waaayyyy in

Sorry can you clarify "push way in"?

1. Specify what you will have for your loaded neck diameter (since you are suggesting you will be neck turning) and then set the neck diameter of your reamer from there (you cannot go wrong around .003" over loaded neck diameter for a 7mm chamber).

do you think .003" clearance is enough for a magazine fed gun? (i.e. won't cause any feeding issues)

2. Unless you know what dimensions your re-size die will resize your fired cases to, you are just guessing trying to dicker with the body dimensions, so you probably should just run with a Minimum SAAMI body for the reamer and head space.

Are you referring to my comments on case length? True I am using virgin brass to make this dummy round how much should I expect the case length to grow after being fired?

3. For throating, you are not really clear what you want to do as I see magazine feed hunting and single load competition mentioned as intended uses. Bear in mind VLD's may shoot well jumping, and they may not, so I would not bank on jumping them and I would tend to stay short enough, if you can, to be in the lands .015" or so at a certain magazine length (i.e. a little shorter than your max mag length). You can typically always load the projectiles back in the case a little more, but you can't go any longer than magazine length if you are working out of a magazine.

The gun will be used for hunting and is mag fed, because of that I didn't think jamming was an option due to the mess that could be created with ejecting a live round. Am I wrong in this opinion? How much of a jam could I get away with and still be safe ejecting? I figured I could set up the chamber so mag fed rounds would be jumped and then for any competition style shooting if jammed produced better results those could be single fed.

Thank you all for the assistance, I am trying to learn as much as I can.
Tony