7 FCP. Before I pull the trigger on this......literally

[PeteFox]

This project has been on the go for a long time and is a bit of a saga, including at one stage the action disappeared in transit, reamers became unavailable and then a lot of waiting. A year later I'm ready to pull the trigger - almost.
I purchased a 7FCP kit from F Class Products. That is a reamer, dies and gauges.
A 7FCP is a blown out, necked up 6.5PRC case, see image.
Due to brass not turning up and me then re-ordering from another supplier, and then it all turned up together, I now have 800 pieces of brass. sorry, not selling.
I've had three barrels chambered up using the reamer and go gauge supplied, the smithing is perfect, thanks Keith.
I have an 8T Kreiger, a 9T Bartlein and a resurrected Swan barrel which will be for fire-forming the brass.

I intend to use random projectiles (197 Sierra), loose primers and some old 2209 I have on hand to get the brass formed. Just going to put them into the backstop.

My question relates to:
1. The brass is headspacing 0.035" short of the target of 2.100" using the supplied gauge. Yes I know the shoulder angles are all different etc and I'm not comparing apples with apples but I have to start somewhere.
So in theory I'm going to need 35 thou jam plus some more to get the base of the case against the bolt. So calculating the jam will be by closing the bolt on a dummy round and then adding some. The question is how much more?

2. Any idea on a starting load for this that will get the brass formed?

Parent case and 7FCP

images (2).jpg

[saum2]

1: I’d use 61gns of 2217 as it’s cooler burning to save your throat a bit.
2: fire form similar to BR to Dasher hard jam and shoot it and if possible expand the neck larger to use the false shoulder method as well as jam

[PeteFox]

Thanks Saum2, Just to be clear
The Swan barrel is sacrificial, not trying to save the throat. I don't have 2217 and want to use the old 2209 I have.
The 197 Sierras are also sacrificial, I'm not wasting Bergers fireforming. I think that the heavy projectile will a good proposition for fire-forming as opposed to some 168s I have.
According to Brian Blake of FCP , false shoulder fireforming is not necessary and doesn't stretch the brass at the base. I'm looking for someone who has done this already with this calibre.
Pete

[willow]

Dave Piddington runs one of these Pete.

[BATattack]

I can't see how it's going to be different to any other improved case.

Use enough neck tension so that hard jam doesn't push the bullet back in the case. Seat the bullet out and gradually move it in until you can JUST close the bolt with some firm pressure. Like 1 to 2 fingers firm, not full fist / rubber mallet firm! Your not calculating jam, you go by feel.

Pick a powder charger half way between min and max of the non improved cartridge. In your case it's going to be the 7-6.5PRC.

[Matt P]

Hi Pete,
Don’t drink the US cool aid, I would strongly recommend using the false shoulder method. I had customer who was told the same as you and had issues getting consistently formed cases, went to the false shoulder method and never looked back.
Matt P

[KHGS]

Hi Pete,
Don’t drink the US cool aid, I would strongly recommend using the false shoulder method. I had customer who was told the same as you and had issues getting consistently formed cases, went to the false shoulder method and never looked back.
Matt P

I agree with Matt 100%, any other method is hit and miss at best.
Keith H.

[Dan81]

Agree with Matt,
I have 7FCP and found the false shoulder method work best when fire forming brass,
58gn of 2213SC is comp load, I fire formed using 55gn of 2213sc and false shoulder method, after trying the jam method it just wasn't consistent.. Considering you have 2209 I would still see it a good idea to buy a small tub of SC for fire forming as 2209 hammers the throat in these.
Comp load in 7fcp using 2209 is 55gn, 7PRCW comp load is about 52.6gn of 09, If you were to fireform using 09 I would start at this..
Some things to look out for when bumping shoulders, It takes approx 2 firings to really get fired shoulders consistent, If I had of bumped my shoulder 2 thou after first firing the brass would have had approx 6 thou shoulder bump. I tried bumping up the fireform load to fix this and ended up splitting 2-3 cases.
Good luck with it

[PeteFox]

Warning, long post.

First up, thanks to those who have taken the time to reply to the topic, including those via PM. I have also had a couple of calls wanting to share info.

Feedback from those actually using the 7FCP it was about even between jam-bullet and false-shoulder. I was warned not to use hard primers (CCI) as that would cause issues.

At the time I posted the question I already had 25 cases loaded, so I decided to try jam-bullet first.

I wasn't interested in accuracy at his stage so I used the excess/throwaway components I had.
Very old 2209 blended from a few batches, I have about a kilo
Federal 210 primers that were odd ones leftover from weight sorting
197 Sierras that I was never going to waste more time trying to get shooting
The barrel was a Swan 7T that I bought because I couldn't get any other fast twist barrel at the time I was mucking about with the 197 Sierras. I had it re-chambered. It is purely for fire forming.
So, I wasn't eating into any stashes here.

I necked up cases using a .283 mandrel
I set the bullet seating depth by closing the bolt on a dummy round and adding 0.008"
The cases were annealed after necking up
I didn't use any neck lube. The bullets were quite tight to seat (arbor press)
I used 49.5 gn 2209 which is a light load. MV was around 2450fps
The 197 is a big heavy bullet to get moving and my theory was the brass would fully form before the inertia of the bullet was overcome.

All 25 cases appeared to form perfectly. I have run all the fired cases back through the action without the firing pin.. The bolt handle closes easily with the slightest hint of interference. So, to be clear, it doesn't fall by itself, but It doesn't warrant a shoulder bump. Cortina fans might disagree, to each his own. This may change with more reloads.

FCP supply a Go Gauge and a case gauge to compare sized rounds against.

I have measured all the cases after firing, because I want to get this right, the brass is dear enough but there is also a big investment in time, so I want to get as many reloads as I can from the brass, so working the brass to a minimum is the way to go IMO.

Headspace is the same as the go gauge at 1.711", using 0.420" as the reference point.
However, none of the rounds would fit in the case gauge.
I initially thought I may be able to correct this by roll-sizing the case and then neck sizing.
In the photo there are three cases:
-- The left case is is a 6.5PRC necked to 7mm (7/6.5PRC)
-- The centre case is sized to fit in the case gauge, it has been run through the roll sizer and then in the resizing die but not shoulder bumped. The arrow points to the upper limit that the roll-sizer works on, so clearly the interference in the gauge is further along the case, as roll-sizing only does not allow the the case to fit the gauge.
-- The right case shows the depth of fit into the cartridge gauge, which is about 0.035" short of the target depth.

cases1.jpg

The .200" line measurement of a new Lapua case is 0.529",
A fired case is 0.532",
I roll sized to 0.530".
A case run through the resizing die without roll-sizing is 0.531" at the 0.200" line. but obviously the die does not reach below this.
I have an Area419 press. It's a big press with lots of leverage, but his was nearly a two handed job and I could feel the bench lifting, extracting the case from the die. On this basis alone I will continue to roll-size as I don't want a stuck case in a die that will take weeks to get a replacement if I damage it.

Unfortunately FCP are not publishing case dimension or reamer print data, they say to limit copying, but from a users point of view it is a PITA.

I may be wrong in this thinking but:
I have been caught out with cartridges before with almost parallel sides. After a couple of firings using neck sizing, extraction become a real problem. So I am theorising that body sizing without shoulder bumping will help reduce case stretch and eventual head separation, as shoulder bumping allows the brass to flow to the shoulder but if not bumped there is limited flow..

[PeteFox]

Replying to myself, it's a bad sign.

As I said, I thought that using a heavy projectile with a light load would use the inertia of the bullet as a plus in aiding case forming.
Explanation.
I have always thought that brass was relatively easy to fireform and this runs contrary to some beliefs that it will take a few firings to fully form a case. I'm not a believer.
Reason being that a case can be pretty well formed by filling a case with water in a special die and then striking a piston with a hammer. Same for the 'cream of wheat" method.
This is a total guess, not backed by any data, but I theorized that giving the case the time to form before projectile movement was the way to go. Once the projectile moves, pressure is reduced and the case ceases to form. Delay the projectile moving and the case forms before projectile movement. That's the theory anyway. I realize that we are talking milli-seconds, as I said it's only a guess.
Evidence that the case is fully formed can be seen in the photo. The photo shows that the case was fully formed because the die sizing marking is along its full length, and measurement of the headspace confirms that the shoulder is fully forward..
There are two distinct lines towards the base. The upper one is the extent of roll-sizing. the lower one is the remnants of the Texta mark.

sized cases.jpg

[Matt P]

Pete,
Before you go and form the rest of those cases using the bullet jam method, do yourself a favour and do a simple check to see if the fire forming is stretching the web area.
Do the cases (once FF) come out longer, shorter or the same overall length ?? If they come out shorter you're good to go as the shoulder is being blown out and reducing the length, if they come out the same or longer this is a sign that you're stretching the case from the bottom. I use this check to make sure I'm not hurting the case. I had issues with cases when shooting Dasher and after doing a lot of testing and dissecting of cases I found that jamming the bullet (no matter the neck tension) wasn't enough.
Regards
Matt

[PeteFox]

Thanks for that advice Matt

I've just measured five cases each, pre and post fire-forming

Average pre fire-forming 2.012"
Average post fire-forming 2.001"

The average difference is 0.010" (rounded). So the fire-formed cases appear to be shorter.

However this is not exactly comparing apples with apples, and measuring individual cases pre and post forming would be a better measure.
Also the formed cases I have, have been through the sizing die. I suspect that I haven't altered the length, not by 10 thou anyway but I'll do it again.
I'll number some cases and measure them pre and post fire-forming to get a definitive answer.

Pete

[PeteFox]

Here we go again

So I don't think the cases aren't getting longer. If I can get some range time I'll do the measurements this weekend to verify.

Another way of looking at this is: The case neck and the shoulder are being reduced in surface area, but overall the surface area of the case is increased. So the bulk of the increased surface area is coming from the body of the case and therefore the case must be thinning somewhere.

How do I know this? Well a cartridge case can be reduced to three basic geometric shapes (all measurements made above the 0.200" line)
The neck - a cylinder
the shoulder - a frustum (a part of a cone)
the body - a frustum

The surface area of each of these can be calculated and can give some idea of where the movement of brass is occurring.
This website >> https://www.calculatorsoup.com/calculat ... rustum.php
has a fairly decent calculator, or the maths can be done longhand.
Both the neck and shoulder are losing surface area -some of the neck is transformed into the shoulder and some of the shoulder is moved into the body.
Overall approx 0.6 sq inch is added to the surface area of the body, of which approx 0.5 sq inch comes from the body itself. See table.

areaof cases.jpg

Next I decided to sacrifice a couple of cases and milled a slot in them so I could measure the wall thickness. One new 6.5PRC and one fire formed 7FCP.

case-slotted.jpg

case-measure.jpg

Using the micrometer as shown I measured at the base, roughly the middle and near the shoulder for each case. The fired case was fairly clean, but I could be measuring a tiny amount of carbon
Results are in the table.

wall thicjness.jpg

I realise this is a sample of 2 cases and is statistically meaningless, however there is no visible or significant measurable difference between the two cases. Given that these are not a precision product I wouldn't be putting too much meaning into the 1 thou difference.

[antunkov]

Pete, I'm reviewing everything you've written and trying to understand your main concern.

I was using FCP, and now I’m testing PRCW.

With FCP, to form the cases, I used the false shoulder method:

1. 0.284 and 0.30 cal carbide mandrel to expand the neck.
2. AMP annealing.
3. Full-length sizing (bumping just enough to chamber with light resistance when closing the bolt).
4. Seating the bullet wherever it provided the best accuracy.

This method gave me excellent accuracy, even at 800/900 meters, during fireforming.

How are your groups on target?
Antun

[PeteFox]

Pete, I'm reviewing everything you've written and trying to understand your main concern.

Antun

Antun, I've received three calls and PMs from people wondering the same stuff as I am, that is, is jamming the bullet a satisfactory way of fireforming 7FCP brass, I said that I would post what I found.

Pete