F T/R Competition Chamber setup question.

E

eracer

Private
Full Member
Minuteman
Mar 6, 2012
31
2
65
Tampa, FL
#1
I'm jumping whole hog, feet first, no experience necessary, into this F-class thing.

My action arrived, and my barrel is probably only a month out.

So it's off to the builder soon, and he wants a dummy round for chamber dimensions.

Here's the fun part - I own all the reloading gear (well, most of it...) but haven't set it up yet (and have never reloaded.) I know, I know, a lot on the plate. Don't worry, I plan to be meticulous, and careful. I'm reading a lot, and learning a lot, but I need to load a dummy round, and I need to do it RIGHT, since my chamber will be cut to this round's dimensions.

7mm SAUM, 180 VLD or 195 Hybrid bullets ONLY.
Single-shot Defiant Rebel X-medium length action.

Please help me build this dummy round. I obviously only have the 180 VLD to work with now, and I don't know what the 195 will look like. I'm guessing I could load the 180 (1.525") about 3/4 into the neck of a new case, and that would give me room for the longer (1.637" - I think) 195 hybrid when and if I use it.

I know the ogive length is the important thing, but the chamber reaming will take care of that. I just need to make sure I have enough bearing surface on the 180, and don't have to seat the 195 too deep. Right?

COAL doesn't really matter, since it's a single-shot, right? The X-medium action is supposed to allow for 3.200" COAL when bottom metal is used.

Hope I'm making sense. Any help is appreciated, as always.
 
#2
Re: Chamber setup question.

In general you will want at least 0.100 bearing surface in the neck. If it's hanging out much further than that you have a bullet that may not stay put (I know it's a generalization)

You don't want the tail of the bullet in the case, you want it no lower than the base of the neck.

That should give you a range to work with. I don't shoot open guns but I'd guess with a 7mm you will want some room to chase the lands as the throat erodes, so figure at least 0.110 of bearing surface at the lands?

I'm sure someone else will chime in.

Another option is to call PTG and talk to them, but be aware, if your barrel is only 4 months out it may get to you faster than your reamer if they don't have one on the shelf. I've been waiting for 2 since about March or April.
 
#3
Re: Chamber setup question.

XTR - that's why I was thinking of seating the 180gr VLD's 1/2 to 3/4 into the neck. Should be enough bearing surface without overpressuring the case (but here's where experience is lacking.) I've heard it both ways - seat as shallow as possible, and seat deep enough to give the bullet a little 'stick' during ignition.

Then when the longer 195gr bullets arrive, I'll have some room in the neck to work with. And as you pointed out, some room to load longer as the throat erodes.

I'm not reaming the chamber myself, I'm sending it and the action to a pro once I get the barrel.
 
#4
Re: Chamber setup question.

Interesting. I seat my bullet so the bottom of the bearing surface is a little forward of the neck/shoulder junction. My boat tail extends to the shoulder/body junction. Seems to work just fine for me. I know some people that have about blown up their rifle trying to get the speeds that I run.
 
#5
Re: Chamber setup question.

Well, I thought it was just me, but I do the same. I like to seat my bullets so the pressure ring at the end of the bearing surface is just above the shoulder/neck junction; the boat tail just hangs into the case a little bit. I feel happier with this setup because the bullet is tight and will not move around when I manipulate the cartridge. I also happen to believe it provides for a more consistent bullet release at ignition time.
 
#6
Re: Chamber setup question.

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: eracer</div><div class="ubbcode-body">...Then when the longer 195gr bullets arrive, I'll have some room in the neck to work with. And as you pointed out, some room to load longer as the throat erodes....
</div></div>

You do realize that a 7RSAUM barrel is good for somewhere over 1000 and less than 2000 rounds depending on who you ask? (I read 1500 bandied about pretty regularly) There is a fair chance you'll shoot your first barrel out before the 195s come to market. I wouldn't worry about them too much at this point.
 
#7
Re: Chamber setup question.

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: XTR</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: eracer</div><div class="ubbcode-body">...Then when the longer 195gr bullets arrive, I'll have some room in the neck to work with. And as you pointed out, some room to load longer as the throat erodes....
</div></div>

You do realize that a 7RSAUM barrel is good for somewhere over 1000 and less than 2000 rounds depending on who you ask? (I read 1500 bandied about pretty regularly) There is a fair chance you'll shoot your first barrel out before the 195s come to market. I wouldn't worry about them too much at this point.
</div></div>

+1. But I believe you are being generous with the estimated round count, especially if it's being run at its full velocity potential.
 
#8
Re: Chamber setup question.

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: eracer</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: XTR</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: eracer</div><div class="ubbcode-body">...Then when the longer 195gr bullets arrive, I'll have some room in the neck to work with. And as you pointed out, some room to load longer as the throat erodes....
</div></div>

You do realize that a 7RSAUM barrel is good for somewhere over 1000 and less than 2000 rounds depending on who you ask? (I read 1500 bandied about pretty regularly) There is a fair chance you'll shoot your first barrel out before the 195s come to market. I wouldn't worry about them too much at this point.




</div></div>Not if it's melonited.

But your point is taken. However, I doubt the first shot will be sent down the tube until the end of this year, and I suspect the 195's will be out before that.</div></div>
 
#9
Re: Chamber setup question.

Here is a friendly piece of advice. If you're new to F-Class, and to you're reloading, I'd start with a proven combination like a .284 Win, in a non-coated barrel, shooting the 180 Hybrid.

I've been shooting and reloading for some time now, would consider myself at least reasonably proficient at both, and there is no way I want to be the first to take on the 195s once they are available.

I guess, my point is get started with a proven combination, then go experiment. The 195s will be just that, and so is the melonited barrel. Neither are proven in actual competition, and you could be setting yourself up for much frustration right out of the gate...

Mark
 
#10
Quick update.

Greg Tannel (who is cutting my chamber) wanted the bullet to be seated with its widest part at the neck/shoulder junction. With Berger 180 VLD Hybrid Target that results in an OAL of 3.090", and the base of the bullet extends into the shoulder.

The Defiance REBEL XM action can handle a COAL of 3.200"

So I built two dummy rounds at 3.090" for him. They will be in the mail on Monday. Does that dimension sound about right to you guys?

It's been a long journey, but the gun is almost finished now.

No meloniting.
 
#12
In my opinion a dummy round is overkill/unnecessary. Buy some good brass. Measure the neck thickness (several pieces and at several places around the neck. Once you get a feel for how think the neck is, you have your loaded round diameter (bullet diameter + 2x neck thickness). Add about 5-6 thousandths to that and you have your chamber neck diameter.

Then tell the reamer maker to make you a reamer with that neck diameter and throated for whatever bullet you want to shoot. There is a good chance this reamer (or something very close to it) is already a stock item. It's not like you're doing anything new.

Of course, this is a little more complicated if you're not going to use off the shelf brass. That's a good reason to use off the shelf brass. Why not go with a straight .284?

(Personally, I would start with F T/R if I were to do it again. It's not much cheaper if at all, but you can focus on shooting rather than equipment. F open is "easy" enough so that you can progress to a point pretty quickly where you are tempted to buy points. F T/R keeps you honest. But to each his own.)

EDIT: Oops. Didn't see the OP's date. I guess I'll just leave this here for the benefit of future searchers.
 
#14
I think the concept of a dummy round has not been explained properly.

The OP's gunsmith wants a dummy round with the specific bullet that will be used seated in an optimum fashion so as to cut the chamber with the rifling very close to the bullet's ogive. It has little to do with the OD.
 
#16
I just met one of the guys from the Brux team this last weekend and he said he had to shoot the 7rsaum and he was seeing 600 rounds before it started to open up for him. I know you're already getting it built but something to consider?

Johnny Dunbar was his name. They got second at nationals this year I'm pretty sure.
 
Last edited:
#18
Denys said:
Well, I thought it was just me, but I do the same. I like to seat my bullets so the pressure ring at the end of the bearing surface is just above the shoulder/neck junction; the boat tail just hangs into the case a little bit. I feel happier with this setup because the bullet is tight and will not move around when I manipulate the cartridge. I also happen to believe it provides for a more consistent bullet release at ignition time.
Click to expand...

Put me in this group as well. Many cases can form a donut at the shoulder/neck junction and by inserting the bullet so the pressure ring is just above this points makes for more consistent pressures and thus velocities.
 
#19
damoncali said:
Even then, I'd say it's overkill. The reamer makers generally have a good idea of what freebore is needed for what bullet - any small differences can be made up with seating depth. And it's going to erode anyhow, so getting ultra precise about it seems nitpicky to me.
Click to expand...

Well, I disagree, obviously. The thing is that many F-class shooters like to use non-standard bullets, you know, the long ones with the better BC values. They also like to seat their bullets in a specific way; I happen to favor the pressure ring just above the neck/shoulder junction, but I know of others who like to seat them further out to provide more room for the powder.

It would be a pisser if you got back your expensive rifle throated too short to handle your cartridges with your choice bullet. Heck of a way to start, I would think.

By supplying to your gunsmith a dummy round, loaded just the way you like them, using you long boutique high BC bullet, you ensure this situation will not occur. You can then make whatever final adjustment you need and chase the lands as you see fit.
 
#20
Denys said:
I think the concept of a dummy round has not been explained properly.

The OP's gunsmith wants a dummy round with the specific bullet that will be used seated in an optimum fashion so as to cut the chamber with the rifling very close to the bullet's ogive. It has little to do with the OD.
Click to expand...

He did ask me to provide him with a neck-trimmed dummy round - but only if I planned to trim the neck. I have a neck trimmer lathe setup from 21st Century, and used it to take a very small amount of the OD of the case neck. He said he will cut the chamber .00x larger than that (don't know the exact number.)
 
#21
damoncali said:
Even then, I'd say it's overkill. The reamer makers generally have a good idea of what freebore is needed for what bullet - any small differences can be made up with seating depth. And it's going to erode anyhow, so getting ultra precise about it seems nitpicky to me.
Click to expand...

That's why he told me to seat the bullet as deep as I did - so that as the throat erodes I'll have plenty of bearing surface.
 
#25
I used a Hornady New Dimension, and an expander arbor from 21st Century.

The dummy was made from a new Norma .300 SAUM case, full-length resized in the Hornady die.
 
Last edited:
#26
I'm in this same boat with Greg Tannel. My problem is that I have new Norma brass and no chamber to form them in then bump the shoulder back a hair. In other words if the factory brass is a hair shorter then my die then running my dummy round thru it won't do any good. Right? Then if the chamber is reamed to that shoulder length it will be impossible to ever recreate it. I haven't run my new brass thru my FL die yet so this is just a "what if".
 
#28
Chad44 said:
I'm in this same boat with Greg Tannel. My problem is that I have new Norma brass and no chamber to form them in then bump the shoulder back a hair. In other words if the factory brass is a hair shorter then my die then running my dummy round thru it won't do any good. Right? Then if the chamber is reamed to that shoulder length it will be impossible to ever recreate it. I haven't run my new brass thru my FL die yet so this is just a "what if".
Click to expand...

I'm not very smart about this stuff, but it seems logical to me that Greg knows what he is doing. He knows that I gave him new resized brass. Why would he cut a chamber that would cause problems down the road? Every piece of brass that runs through the chamber he cuts will be resized, and should fit, regardless of whether it's new or fired. The only issue might be that my neck OD trim might change, and if he cuts the chamber to fit a smaller OD than I end up with, I could have chambering problems. Fortunately, that would be an easy fix. He did tell me that he will cut the neck area a few tenths over.

And you wouldn't send him a dummy round that hasn't been resized.

Right?
 
Last edited:
#29
I would. I never resize virgin brass, what could I possibly gain by doing that? I just shove a mandrel through the mouth to round it out nicely and voila, it's ready. I only use Lapua brass in my match rifles.
 
#32
Lots of back and forth on this. It would seem to me that if chamber and cartridge match are that important and all the standard practices of just neck sizing and shoulder bumping are inadequate, then just have the chamber cut using a "no turn Match reamer". Then fire a few cases at least 3-4 times and send them off to Hornady (or die maker of your choice) and have them make a custom sizing die. Under $200 and far fewer damaged brain cells.
 
#34
damoncali said:
I'd go even simpler. Spec a chamber for neck diameter (turn or no turn, up to you) and freebore and use off the shelf bushing dies. You are good to go and should be able to theoretically clean an F Class target with room to spare if you have a good rifle/barrel.
Click to expand...

That works (for me anyway) as long as the reamer isn't at the high end of spec for body diameter(s). I hate the "muffin top" that tends to grow just above the web. My last barrel was reamed with a nice "tight" reamer and fired cases show little or no bulge. This part isn't all about accuracy but case life. Less working of the brass and I've found fired cases are a lot straighter.
 
#35
Which is exactly why I use a full length, small base bushing die to resize all my Lapua brass after every firing. The body does not grow a muffin top and even 9 times fired brass fits nicely in the guage, even before resizing. I use SB dies for my .223 and .308 F-TR rigs.
 
#36
Denys said:
Which is exactly why I use a full length, small base bushing die to resize all my Lapua brass after every firing. .
Click to expand...


Surprisingly enough, one does not always have to purchase a Small Base Die to do this. I recently found that Hornady Custom Grade New Dimenison F/L sizing die, Forster F/L Sizing Die, and Redding F/L sizing die, also size the cases down below the top of the case web. Perhaps others do as well but these are the ones I own. I don't own a single S/B die and haven't had any issues, even with 5.56mm "Machine Gun Brass" I've sized and loaded for my 3 AR's.

Now one "could" have an issue if they have extra headspace and they're adjusting their F/L sizing die out to only bump the shoulders the usual .002" or so. That could leave a "muffin top" as the die is no longer passing down over this area with enough "squeeze" to eliminate it.

Just sharing my experiences
 
#37
Your ARs may well have Wylde or NATO chambers, which will swallow whatever .223/5.56 cases you feed them. My NM AR has a Wylde and it takes everything. My F-TR Match AR has a tight match chamber and it needs the small base resized cases or else the cases do not come out, don't ask how or rather, when I found that out.

My other ARs swallow anything. (NATO chambers.)

My F-TR .308s have very tight chambers, by design and as I specified them. I use SB dies for their ammo and I don't even try to chamber a cartridge fired in another .308 and then resized with a non-SB die; I hate to shove cleaning rods from the muzzle to push out fired cases.

My match ammo gets reloaded a lot (8-10 times). My hunting or blasting ammo, not so much or not anywhere near as much.
 
#39
Yeah, I got some of those comments 5 years ago when I discovered the issue. "Geez Denys, I didn't know you were shooting a musket," and other similar smart-donkey comments. I was able to finish the match somehow. I switched to Winchester for my .223 right after that because I had a few thousand virgin Winchester cases and had to retire all my now-unusable Lapua .223 brass, when I discovered that even SB body or F/L dies can fix that "muffin top." I wanted to cry.
 
You must log in or register to reply here.

Similar threads

Rommel Garcia
Reloading Tikka T3x 308 - Fires when chambered after bolt lock
Replies
11
Views
303
RandyM72
R
D
.223 Wylde Chamber in Trainer?? I don't get it. . . or do I?
Replies
13
Views
634
msgriff
M
MtnCur1
SOLD 300 RUM carbon barrel
Replies
3
Views
159
TicTacTex
TicTacTex
Highplainsdakota
Bullets, not ammo, in carry on luggage?
Replies
8
Views
418
Franko
F
L
Bergara B14R: Failure to eject
Replies
11
Views
374
jpp3g
J
Top Bottom
Back
Home
Forums
Merch
Alerts