Concentricity, accuracy, and neck turning

[davidreeves20]

Of course the goal is accuracy or small groups...currently getting 0.5" to 1.5" with 7 rem mag sporter barrel, rem 700 that has been pillar and action bedded, light trigger, and torqued. I'd like to get down to the 0.5" range consistently. Currently loading with Hornady ELD-x 175gr. Also working on load development, varying powder charges and seating depth.

Since Lapua brass is not available for 7 rem mag I got new Winchester. The concentricity of loaded rounds was terrible 0.015" sometimes a little less. The concentricity of fired rounds before anything was less than 0.001". After full length sizing with RCBS die was terrible so removed the deprimer/expander ball and problem solved. Added Sinclair mandrel die to expand and all still good - less than 0.002". When bullet seated still nearly 0.0100" and when went to Forster Micrometer Seating Die little better 0.0045"-0.0100".

One issue I think I have with the Winchester brass is neck thickness which varies between 0.011-0.015" . My question ...I have not tried neck turning. Do I need to turn the neck down to uniform thickness to correct concentricity and hopefully improve accuracy...or is it likely something else? Any thoughts on other brass brands?

Many Thanks!

 

[Steel head]

Honestly I’d look more at your dies than your brass.
I use a lot of Winchester brass, some neck turned and some not and both are easy to keep straight.

 

[hafejd30]

Neck turning can’t hurt. It’s always a gamble with a factory barrel whether the effort will pay off tho

 

[BullzeyeNJ]

Benchrest shooters neck turn because they have to because of the custom chambers they use. It will make the neck walls more consistent in thickness which is a good thing. With that said, most experienced BR shooters will admit that you really wont see the benefit on the target vs un-turned necks. IMHO, If its very good quality brass that is very consistent out of the box then it may be a waste of time.

 

[pabrousseau]

are you using powdered graphite to lube the neck before sizing with the rcbs die? the forster f l sizing die is the best in my opinion. it is designed in such a way that the expander is started into the neck while the case neck is still supported in the neck of the die. take the seating stem out of your seating die and make sure the point of the bullet is not hitting the top of the seating cone and check to see if it needs to be polished. some are rough. when seating the bullet you could try raising the ram and ever so lightly touch the seating stem with the bullet lower the ram enough to turn the case one third of a turn .touch the seating stem again and then one more time do this . it is difficult to feel with the sliding chambered seating dies like forster benchrest and redding competition seaters. I think sometimes it's necessary to get them strait but it is a little time consuming. the last three 7 rem mags I worked up loads for liked 7828, fed 215 primers and used Hornady and sierra bullets. all three shot very well. not what you asked I know but some things to look at. good luck with your rifle.

 

[davidreeves20]

Thanks all for a lot of great ideas.

First, I don't know if my new Winchester brass neck thickness variation of 4 thousands is "good" or "bad" quality but I don't think it contributes to concentricity. Wondering how much concentricity could be improved by a consistent neck thickness... I've seen a few tout Federal brass for 7 rem mag and Norma and Hornady are certainly more expensive.

I think what I was suggesting is just to neck turn the brass to a consistent thickness versus make especially thin however I guess if it is 11-15 thou I would have to turn to 11 thou to be consistent?

Second, on dies...perhaps I am wrong but since concentricity of the fired brass started out great and after resizing (once expander ball removed) was still great, I concluded there was no improvement possible by changing the sizing die.

pabrousseau - I have tried the graphite but thought that was primarily for the inside expander ball or mandrel. I'll have to check out the seater stem carefully. I called myself checking the point but not really for roughness yet. Will have to try the 7828 and other bullets. Thank you.

I'm hoping that more consistent neck thickness will lead to better concentricity.

Thanks again everyone!

 

[bourbonbent]

I’ve shot out 2 7mm RM barrels, and found some great loads. I’m not sharing those, but I will say this.

I weight sort brass and bullets, FL size enough to barely bump the shoulder, weigh charges to the individual kernel, and when I’m seating bullets, anything harder or softer seating (case neck tension), gets sat to the side. 7RM will shoot real small. I have a group in the .1’s downstairs I shot with a Savage during load development.

Neck turning helps most if you have a chamber cut for it, if you’re having brass flow in weird spots, or if you’re receiving brass with horribly uneven neck wall thickness, in which case it must be removed or the case discarded. I trim to length every single time, and deburr/chamfer. I use Forster dies, and a Dillon RL550B. I’ve had the best luck with Forster dies, and the Dillon loads great ammo. I use H1000 almost exclusively in 7RM, nothing else I’ve used has come close to it. H4831 for lighter weight bullets.

The guy that set the most recent 1k BR world record didn’t turn any necks if I remember correctly, and that group is nearly beyond belief even with witnesses.

 

[pabrousseau]

from sinclairs precision reloading and shooting handbook. if neck variance of more than .0015 are found they recommend neck turning. and they recommend cleaning up 75 to 80 % of the neck surface. I would think variations of .004 would indicate pretty poor brass.

 

[davidreeves20]

New to neck turning. Originally the Winchester brass varied between 0.011 and 0.015" so I trimmed until I thought I had around 3/4 of the neck surface trimmed. So now after trimming the max thickness is 0.012" with some measurements under 0.011". There was a huge improvement in concentricity to 0.003 or less. Accuracy possibly improved some but not as dramatically as I had hoped. Should I try trimming to 0.011" or possibly less?

 

[pabrousseau]

David with .003 or less run out at this point i would work on load development. seating depth, different bullet, powder . tangent ogive bullets seem to be easier to work with for accuracy, like sierras. tell us about the rifle. some don't like particular weight bullets. ive had a couple 30-06 rifles that only wanted 150gr bullets. yes the graphite is to keep the expender from pulling the neck out of alignment. you are correct .

 

[DownhillFromHere]

0.004" variation in neck brass thickness sounds excessive to me, but I've only handloaded Hornady and Prime/Norma brass (6.5CM). I use RCBS match dies with bushing resize (no expander) and micrometer seater coupled with Sinclair mandrel.

The seating die has a sliding sleeve that aligns the bullet with the case before seating. This seems effective, as almost all my rounds show 0.001-0.003" and the worst I've seen is 0.004" - 0.005" measured on both the neck and the bullet ogive (pretty much exclusively Hornday 147gr ELD-M).

I run the resize bushing about 3/4 of the way down the case neck as, especially with Hornady brass, I've found the neck to be thicker at the bottom by a thousandth or two. The Sinclair mandrel makes the inside diameter consistent, which I guess is the first priority.

I tried neck-turning brass for a heavy-barreled .25-06 I had back in the '70s. Royal pita. Won't do it again (famous last words, check my post history and I said I wasn't going to handload again either ). When the stars align, mirage is absent, and the wind is quiet, these loads give me 1/2MOA accuracy at 500 yards, 3/8" at 100. I'm fighting hard to resist the urge to throw money at the single-digit ES loads I read about here... in my youth, a 3/8" 100-yard group was amazing and I tell myself it's good enough today...

 

[davidreeves20]

The rifle is a Rem 700 wooden stocked 1970s 7mm Rem Mag that has been free floated, pillar and action bedded and torqued to 65 in lbs. It has a triggertech special trigger at just over 1 lb. I understand that at that time Remington 700s were 1:9 twist but have not checked it.

I have tried some 140gr nosler ballistic tips in addition to the 175gr ELD-x. I guess I'll try some Sierras and different powders next.

When do you decide its just time for a new barrel?

 

[918v]

Get a Lee collet neck die and a Redding body die. Your eccentricity will be reduced to insignificance.

 

[Steel head]

Get a Lee collet neck die and a Redding body die. Your eccentricity will be reduced to insignificance.

I use this die setup.
It really does work.

With neck turned Winchester brass it very rare to get runout greater than .002.

With regular Winchester Brass .004 is about the high limit and that’s only on few problem cases.

 

[pabrousseau]

nice rifle. I would choose a bullet and start .010 off the lands, start low enough with your powder charge and work up watching the pressure and see what will give you the accuracy you want. I have worked with a lot of factory 700 rifles and that forend pressure point is there to damp the light weight barrels. you can experiment with thin plastic shims, folded paper,business cards whatever. it does not take very much upward pressure. never seen a really tight shim produce good accuracy.

 

[JOE62]

I have a 700 Custom KS in 7mmRM and it has a very short freebore. I didn’t like the fact that new 7mmRM brass has to stretch .017 to .022 to fit the chamber the first firing. So I made my brass from 300WM brass and turned the necks down to all the same. I also use the LCD and get very low runout. Mine really likes the 150’s and the Hornady 150 ELD X is the most consistent bullet I have measured. Accurate too.

 

[davidreeves20]

I stated above:
New to neck turning. Originally the Winchester brass varied between 0.011 and 0.015" so I trimmed until I thought I had around 3/4 of the neck surface trimmed. So now after trimming the max thickness is 0.012" with some measurements under 0.011". There was a huge improvement in concentricity to 0.003 or less. Accuracy possibly improved some but not as dramatically as I had hoped. Should I try trimming to 0.011" or possibly less?

So what is the minimum neck thickness that you should turn to? To eliminate ALL of the variation in neck thickness, should I trim to 0.011 or even 0.010? While certainly not my idea of fun, the way I understand it, it should only be required once so is a tolerable effort IF it improves accuracy.

I started neck turning to improve concentricity and it clearly worked because that was the only thing that I changed. Is concentricity of 0.003 good or just good enough or do you think it needs to be better? Will even more consistent neck thickness possibly improve concentricity more? Certainly turning the necks down to 0.012 improved concentricity.

As I stated in the beginning post, concentricity after sizing and before seating was 0.002 or better, so my takeaway is that the sizing die approach was not the problem with concentricity. Is this correct?

DownhillFromHere
"0.004" variation in neck brass thickness sounds excessive to me, but I've only handloaded Hornady and Prime/Norma brass (6.5CM). "

Are you suggesting that I got a bad batch of Winchester brass or that I didn't measure correctly? But now since it's been turned down to 0.001-0.002 neck thickness variation it's fine right? Are you saying I should pitch the Winchester brass?

918v
"Get a Lee collet neck die and a Redding body die. Your eccentricity will be reduced to insignificance."

I appreciate the suggestion but as I stated in the beginning post, concentricity after sizing and before seating was 0.002, so my takeaway was that the sizing die approach was not the problem with concentricity but perhaps there is still some improvement possible. Are you saying that you get appreciably better than 0.002 after sizing? And does that improved concentricity improve accuracy?

Steel head
"With neck turned Winchester brass it very rare to get runout greater than .002.
With regular Winchester Brass .004 is about the high limit and that’s only on few problem cases."

So my question is am I neck turning correctly? What do you do with the problem cases ... turn them more or toss them?

pabrousseau
" I would choose a bullet and start .010 off the lands, start low enough with your powder charge and work up watching the pressure and see what will give you the accuracy you want."

Do you use Hornady OAL guage or similar or chamber a round and remove to measure seating ? I've been doing the latter but perhaps that is not accurate enough.

"I have worked with a lot of factory 700 rifles and that forend pressure point is there to damp the light weight barrels. you can experiment with thin plastic shims, folded paper,business cards whatever. it does not take very much upward pressure. never seen a really tight shim produce good accuracy."

Ouch! Well that is something else to test. After all the effort to free float and bed, etc... Perhaps it's time for a new heavier barrel?

 

[pabrousseau]

David I like to seat a bullet in a deprimed fully fire formed case. then I take fine steel wool and pinch the bullet and turn it in the steel wool. it removes any marks on the bullet, and produces a surface that will show the land marks well when chambered. if I happen to get land marks that measure .020 I will seat .030 deeper, check that and if no marks start load work there and adjust if I need to. measuring with a comparator we are just picking a starting point and we are able change seating depth in increments we desire and the target tells us what the rifle wants. as I do it or with the Hornady tool you are finding a place to start. I doubt the Hornady tool is as accurate because it's base to shoulder will more than likely not match your chamber. there is a good video on the net showing how to get the bolt face to lands measurement by totally disassembling the bolt. very accurate but I don't think I have to remove the ejector using a fully formed case.

 

[pabrousseau]

I hope your rifle is very accurate floated. some aren't but a little upward pressure on some produces great results.

 

[DownhillFromHere]

"0.004" variation in neck brass thickness sounds excessive to me, but I've only handloaded Hornady and Prime/Norma brass (6.5CM). "

Are you suggesting that I got a bad batch of Winchester brass or that I didn't measure correctly? But now since it's been turned down to 0.001-0.002 neck thickness variation it's fine right? Are you saying I should pitch the Winchester brass?

I'm not experienced enough to say whether 0.004" runout is unusual on a broad scale - I'm just saying I haven't seen anything like that in the several hundred Hornady and Prime cases I've loaded. If your brass is neck-turned to be concentric and the neck brass is thick enough all the way around, I see no reason not to use it - but with that said, there are many here with more experience is this aspect of reloading than me. I've reloaded heaven only knows how many hundreds of thousands of shells&cartridges over the last 50 years, but I'm relatively new to precision cartridge handloading.

 

[bax]

I would be surprised if a 1.5-inch group was caused by .004 concentricity variation. Work on headspace, jump, bullet, powder, and charge first.

About neck turning. First the issue. If you use the "clean up 80% of the surface" guideline, you end up with x cases with neck thickness A, y cases with neck thickness B, and z cases with neck thickness C. Suppose that you go to the range and shoot some A and some B. When you go to reload, first you have to decide if a case is A or B so you can use the correct neck button. You can probably use the same expander mandrel but you will have different neck tension because A has more or less brass than B.

Suggestion: pick a neck thickness and stick to it. You might pick .014 because you can always take more off - it's hard to put it back.

I have some 300 Win Mag Winchester cases with .010 necks, .011 necks, .012 necks, and .013 necks. And, since the brass flows, they don't stay that size so you get .0104 and .0105 and .0106 and so forth. Sorting is a pain. I also have some really wonderful Winchester ex-mil brass with pretty consistent neck thicknesses. I didn't turn any of it, I use the same neck button and a mandrel, I didn't even try to measure the concentricity, and it shoots great.

You might also consider your existing brass as education. Now go and buy some more consistent stuff that you don't have to turn. Turning necks is a pain the ass anyway - buy better brass and avoid the whole issue. There are no coolness points for being forced to turn brass.