Home Forums Reloading Big Game Rifles Neck sizing in 'springy' break open single shots

I set out to check the accuracy of a cva hunter in 7mm 08 and get it ready for field use. I have a fair amount of experience reloading for several rifles (223, 243, 270) and handguns (38, 357, 44 mag). I think I'm pretty familiar with many reloading techniques for bottleneck carts and bolt guns. Having said that I'll jump right in.

The first session with the cva was bbl break-in using Hornady factory loaded 139 interlocks to get some brass. The only thing out of the ordinary from that session was I suspected two distinct poi depending on my firmness of hold. OK. Once I realized this, I shot some off of sticks (since that's how the rifle would be used in the field) and noticed a 6� average poi shift up. OK, no red flags yet, although I was beginning to get the feelings this might be only a 150 yard rifle after all.

I measured the brass oal after neck sizing only and found a huge variation (2.028 to 2.042). Could the Hornady brass be that inconsistent? Apparently. Trimmed all to length (2.030 -0.0 +0.002). Selected a couple of powders (Bl-C(2) and H380) and loaded some pretty mild 150 partitions at 'to touch' and '-0.030). Results were disappointing, almost demoralizing. The dreaded vertical stringing. It was very difficult to manage muzzle jump on a typical benchrest setup. I never did get the straight back recoil I'm used to on my 700's, 700V, etc.

So, measured brass oal again and all had grown by avg 0.004. Recall these were fire formed cases. Neck sizing added another 0.001 to 0.002. So, on average the prepped brass grew 0.005 on mild charges when re-fired in the same chamber. I didn't catch on yet... so jumped to a slower powder (4350) and repeated with not so good results, except for a pair of about 1� 3 shot 'groups' at 41.0 gr.

Time for more net research (just so none think I am claiming I discovered this all myself). I closed the action on an empty chamber... no visible light between bbl and breech. Same on fresh Hornady round AND once reloaded round. However, after the second reload the cart head protruded 0.008/0.009 from the bbl face and upon closing the action light was visible at the top of the breech. Measured the factory and once reloaded rounds and got 0.004 and 0.005 protrusion. So, the action is springy enough to allow a neck sized only fire formed mild load to grow almost 0.004 on subsequent firings. Don't know exactly why this didn't show up after the fire forming.

Which brings me to the obvious questions:

Is neck sizing only (typically) inappropriate for break action rifles?

Does the same thing happen, albeit to a lesser degree on bolt guns, but the camming action of the bolt mask the effect?

Who has solved this vertical stringing problem on the CVA hunter/scout series of rifles (bottleneck, not straight walled calibers)? (I've read about the o-rings, the forend tit, etc. but am willing to listen again)

AND, unless it seems that I am dissing Hornady, I have to say that I fired 9 rounds at a single poa, and 5 of those had a horizontal dispersion of less than 1/4� @100 yards. So those inexpensive American Whitetail loads aren't all bad.

Thanks all

Well....I've been living and learning with a 708 scout rifle for 2 years. The EXACT same happenings you describe are what I went through. And one day depending on how you hold it the gun will put 5 shots into an inch and the next day the same reloads will be all over a 4" vertical but tight horizontal.
Heres what I've come up with.
My chamber has alot of headspace...brass can grow from base to midline on the shoulder by .0065". Its my belief this gun will never shoot consistantly with loads over approx 45k pressure. Those loads will expand the brass out the chamber and agaist the frame causing flexing. BTW..the chamber is pretty smooth on mine...kind of wish it was a little rougher.
So heres where I'm at now. I've run a pile of loads with 140-160 bullets using quickload to predict pressure at 45k. The gun is behaving pretty nicely. My best load to date is the 160 accubond fueled by 37 grain varget at 2300fps. This load will shot moa consistantly at 100 and I'm gonna start trying it at 200. When I bought the gun I only wanted a lightwt compact toy for dragging through the wisconsin brush for deer season. That load will get me pretty much point blank to 200 yds so I guess its what I was looking for. Its been a pain in the ass but at the same time a little fun and rewarding.
Oh...and I would recomend that you fl size your brass down to virgin dimension so the shell can move forward at the firing pin strike and stay "in the chamber" during combustion if that makes sense. Light loads will only grow the brass about .003" and it can go back to virgin dimensions nicely. Resizing full power loads got me about 3 reloads before case head separations started in.
If you are interested in a history of my reloading for this send a pm with your email address and i'll copy it back to you.
I3031 at starting levels and I 4895 are also good powders but the gun loves varget and longer bullets.

thanks to kraky for inspiration. I dug out the fl dies and did some experimenting. Note that this applies to cva hunter/scout in 7mm 08.

First off, the chamber might be on the tight side. I say this not so much because factory loads protrude approx 0.005 from bbl face, but because the action starts to not close 'properly' (the same) when that 0.005 becomes about 0.009. If i baby it shut with a 0.009 protruding (neck sized) cartridge i can start to see light between the breech face and the bbl. Also, I found a way using calipers to measure the amount of engagement of the breeching lever. I measure from the inside of the front of the trigger guard to the front of the lever.

When the action is closed normally on an empty chamber, factory or fl sized round this is about 0.862". When the light just starts to appear it is more like 0.848" and with a noticeably protruding cart head it can be on the order of 0.825", or less.

So, thinking of bolt rifles we take great pains to square the action (bolt face). But with the way the cva locks up, any resistance in closing destroys the alignment. Seems like a strong argument for full length sizing for this rifle, and perhaps other break action rifles.

And, to also ensure you use a consistent technique when closing the action... OR...

I guess i could quickly solve the vertical stringing by laying the rifle on it's side.

More to come, no doubt.

more research on chambers/cart dimensioning turned up this little gem. quoting from a wiki search (http://en.wikipedia.org/wiki/Delta_L_problem)

"...With most European cartridges, the dimension "S" is always identical. On the other hand, many American cartridge designs exhibit an oversize designated as delta L (ΔL). This leads to the situation that a cartridge manufactured at the upper tolerance limit can not be loaded into a chamber that was manufactured at the lower tolerance limit. Because cartridges are often manufactured in the lower dimensional tolerance limits and chambers tend to be manufactured in the higher dimensional tolerance limits, these problems are often avoided with (semi) automatic and repeating arms. The locking mechanism normally compensates a light oversize of 0.02 mm � 0.03 mm without any problems.

On the other hand this oversize is a major problem with break action and combination guns, which are less common in the United States than in Europe, because correct cartridges cannot be loaded into correct weapons in the event ΔL was not considered during manufacturing. Break barrel arms will not simply close when the cartridges and chamber dimensions are not in concert. For this reason the chambers of break barrel arms are generally manufactured with reamers that take ΔL into account.[1]

Generally bolt-action and break barrel hunting rifles in C.I.P. regulated countries are not cut to the minimum C.I.P. chamber dimensions so this problem is mostly theoretical. The arms manufacturer SIG SAUER brands Blaser and Mauser are however known for hammer forging tight (but still C.I.P. conform) chambers in their Blaser R93 straight pull bolt-action and Mauser M03 bolt-action switch barrel rifles and some rifle owners reported ΔL problems with those rifles. These problems can also occur with other European made rifle brands. ..."

Interesting of note is that the CVA hunter/scout (and I assume muzzleloaders also) are manufactured in Bergara Spain, then imported through Black Powder Industries in Atlanta.

Might explain some privi partisan 308 brass I bought years ago that wouldnt chamber in virgin form till i pushed the shoulders back about .002".

this will show my age, but i dug up and scanned this article from my files. american hunter, sept 1985. Ed Matunas concluded over years of record keeping for several HUNTING rifles, that neck sizing's only clear advantage was to not have to deal with case lube. For you benchrest peeps with tightly controlled concentric chambers, i don't think his data/rationale applies to you.

the quick summary is that in almost every instance accuracy was BETTER with fl size, and case life virtually the same.

this thread is discussing 7mm 08 specifically, and it may be a coincidence but his data shows the case life to be significantly lower than other calibers, and groups also larger. quick guess would be that his particular rifle had a generously sized chamber.

WELL, dang. my scan is wrong format to allow upload. I'll post this, then add the file link in a bit....

ok, sorry about the resolution. file size limit seems to be 97k and if this isn't readable pm me and i'll send a high res version.

tagging this thread for continued reading and learning.

Thanks to both of you for posting your experiences and for sharing your knowledge. Much appreciated!

i full length sized some starting loads using h380 and magnum primers. since it's spherical powder and the load density is so low, i selected mags to ensure uniform ignition. this is not the end of the work, but at least shows there's hope. these are hornady 154 interlocks.

kraky has found 160 accubonds and varget are the ticket for his cva scout. he too is keeping the pressures down, and shot a fine 10+ shot group at 200 yards.

Why are you guys using the CVA scouts? Is it required by your laws or something?

heehee... good one.

10. i like to not worry alot about the conditions my expensive rifles are subject to.
9. i crawl around in the thickets, ducking under crap and like the idea of a rifle i can carry, cock and fire one handed at wild hogs.
8. i almost got eaten by a hog once 'cuz i don't hear well and it got on me before i could get my 700 on it.
7. we're not talking wheat fields, power line cuts, and soybeans here.
6. i love the beautiful robotic tig weld mating the bbl and locking lug
5. lifetime warranty.
4. $ - it's not out of the question to own one for each vehicle - once you get up the learning curve on the first one.
3. loading and unloading is a breeze.
2. grandkids
1. i enjoy a challenge.

All of the above...cheap (under $300) for a good looking stainless rifle.
I love an "underdog" lol!
Really compact for deer drives in heavy brush.
Lastly......just a bit more "sporting" carrying a single shot.
No one else ( till now) has one...lol!
After having a 7-30 waters contender I always thought I 'wanted ' a 7-30 carbine. Now that I have to download my 708 I got my wish...

Read Mike Belm's website and read it again. It will save you alot of hassle. I went through this with an Encore and Bellm's work saved the day. I even spoke to him on the phone and he was a super nice and helpful fella.

To answer your question, neck sizing does not work well for break actions.

My 350 Rem Mag Encore stretches brass terribly resulting in negative headspace every firing. I have to size it for quite a bit of shoulder bump with a FL die before proper headspace is achieved. So much so that brass last at the very most 3X before the heads start to form the bright seperation line and have to be tossed. Mike does a good job of explaining how all of this works in his web pages.

Have a good one,

loder

Reloader...I think you gave me this same.....very correct advice.....a while back when i was "guessing" this is what was happening. Playing with this has been a pain in the arse but at the same time rewarding. I've got 20 more identical "fresh" 2x loaded shells to run through my gun tommorrow.
Hoping the "gods" are on my side and points of impact the same as the last visit to the range!

Good luck Kraky. Let us know how she does.

It did pretty good....200 yds.
There's 12 shots under this folded bill. I had one called flyer that I taped off just to the right. Being this gun has been fussy I actually tried not to be particularily consistant on my hold. 37 grains varget under 160 accubonds launched at 2300. The remaining rounds I shot at 100 to get a point of impact reference between the two.

chop house, I see you are making progress. Something stood out in the post both you and kraky made about keeping the pressure lower in the break action rifle. I experienced the same problems both of you did with my cva break action rifle with verticle stringing and inconsistent shot to shot performance.

At the time that I owned the 7-08 cva, I had six H&R topper rifle barrels in 30-30 that I mated to modern receivers that shot lights out with LE powder and 170 grain Sierra FN bullets. and not so consistent with pointed bullets so I decided to just shoot the FN's when my supply of pointy bullets ran out. Hodgdon lists the 170 grain Sierra FN pressure at 34,700 cup with a WW case and a WLR primer and 36.3 grains of LE powder. So the lower pressure round gave the best accuracy. You are probably onto something.

Another example are my two Handi-rifles in 30-06 shooting 180 grain Sierra or Hornady round nose bullets over 60 grains of H4831sc with RP components. Hodgdon lists the pressure at 44,300 cup and these are very accurate in both of these rifles. I FL resize for both loads and don't worry about case life but I can fire the cases at least twice before having to trim with accuracy unaffected.

As for cva or h&r single shots I give(for me) the edge to the h&r simply because of where the breeching lever is as I have a Sidekick mzldr as well and several topper and pardner shotguns and they all "operate" the same. Also the fact that I'm left handed keeps me coming back to single shots.

Good Research you have come up with.

That'll work kraky.