F T/R Competition Dumb Reamer Question

[clmayfield]

I was looking for F-class reamers for a dedicated F/TR build and I noticed that most of what is available is minimum SAAMI spec. Given the velocity limitations of the 308 cartridge, wouldn't the smart way to go with a custom rig is to go with maximum SAAMI spec to give a little extra room for powder?

Given the fact that we are going to reload for the rifle anyway, it seems like bigger is better. Am I missing something?

 

[memilanuk]

Re: Dumb Reamer Question

In theory... as long as fired cases pass freely in and out of a SAAMI case gauge from Wilson or Dillon, bigger would be (marginally) better, theoretically. You'd probably need to get some custom dies made as well, to minimize the sizing of the brass, as I think most commercial dies would over-work your cases. I'm guessing that nobody has wanted to re-invent the wheel that far yet. The amount of gain in volume would likely be fairly small (maybe a percent or so).

 

[9H_Cracka]

Re: Dumb Reamer Question

Sounds like you need to get one of each made, do your own testing, and post the results for others to learn from.

I would test it with LC brass in the minimum chamber and WIN in the max chamber as part of your testing - that would also take into account the thickest and thinnest brass you can readily get your hands on.

You will also want a custom made die for the maximum chamber so that you are not overworking your brass, shortening its life, as standard dies will overwork that max spec brass.

 

[clmayfield]

Re: Dumb Reamer Question

I would go with a custom die either way, so that's no biggie.

There is already a pretty substantial difference in powder capacity between Winny and Lapua. I imagine going with a big chamber would change things up quite a bit. The only problem is that I just finished switching over to Lapua Palma Brass (small primer). It will mess up my reloading set-up.

I heard there was a movement in FTR towards these bigger chambers, but I think people have been cheating and using non-SAAMI chambers like 308AI. I want to stay well within the rules.

 

[9H_Cracka]

Re: Dumb Reamer Question

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Carter Mayfield</div><div class="ubbcode-body">

There is already a pretty substantial difference in powder capacity between Winny and Lapua.

</div></div>

My chrono tells me .2 gr of Varget or RL15 difference between Lapua and WIN cases to achieve the same (within SAMMI spec pressure) velocity.

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Carter Mayfield</div><div class="ubbcode-body">

I heard there was a movement in FTR towards these bigger chambers, but I think people have been cheating and using non-SAAMI chambers like 308AI. I want to stay well within the rules. </div></div>

Are you someone "inside" the sport today? How have you come upon this knowledge the "people" have been cheating and using AI chambers? Got any specific places and times to back this claim up? I'm sure the F-Class principles that are watching this thread would like to see specifics.

 

[clmayfield]

Re: Dumb Reamer Question

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: _9H_Cracka</div><div class="ubbcode-body">
Are you someone "inside" the sport today? How have you come upon this knowledge the "people" have been cheating and using AI chambers? Got any specific places and times to back this claim up? I'm sure the F-Class principles that are watching this thread would like to see specifics.
</div></div>

Now hold on here. I worded it poorly. I am not accusing anyone of anything. I have just read about it here and there.

Here's a thread on it:
http://benchrest.com/showthread.php?65411-Chamber-dimensions-allowed-in-F-TR

I also remember reading about it here somewhere. It could just be shooters complaining about a bugaboo that doesn't exist.

I shoot non-sanctioned stuff here at mid-range, just because I have to drive all the way to Houston to shoot an NRA-sanctioned match. I don't have the time on my hands to do that, but I am hoping there will be a day when my kids are grown up a little more and I will have the free time to make it out to those matches. It would be a bummer if I had a rifle built and then found out it wasn't legal.

So there we are.

And then, out of curiosity, I was wondering why bigger isn't better. Lots of min spec reamers out there. Not a lot of bigger ones.

I have found that when I push my 308 hard enough to do decent at 1,000, I am over pressure. I was hoping that with a large enough chamber, I would have enough room to hit that last accuracy node at sane pressures. I guess I should also note that my current 308 is just a hair under SAAMI. I guess another reason that I would like to move in the opposite direction.

 

[XTR]

Re: Dumb Reamer Question

Carter, one of the things you may run into with a bigger chamber is losing the primer pockets faster. That's the typical mode of failure for brass for F class shooters. We shoot hot loads, the brass takes a beating and in a few reloadings. Typically I read people getting as many as 6 or 8 but I've had conditions combine (high temperatures and switching lots of Varget w/o getting to do testing) to cause soft seating primers in as few as two or three uses. I think A large chamber is going exacerbate that failure rate.