7mm SAUM Rechamber/Barrel Life

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Marty
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Joined: Mon Jun 18, 2007 5:53 pm

7mm SAUM Rechamber/Barrel Life

#1 Postby Marty » Sun Aug 05, 2018 6:38 pm

Howdy.

In the past, running 284 Win (reaching back to Raton, 2013), I would have said that (for me at least) a rechamber would be in order for a straight 284 around the 2000 round mark.

For Connaught we moved to 7mm SAUMs and in preparation of going to that FCWC I got 4 new 7mm barrels to build up and trial to take the best two. This meant that I then had a few left in the cupboard when coming home. Therefore in the interim the shot count has been fairly evenly distributed between a number of barrels.

At this stage, of all the barrels that either did or didn't make the cut for Connaught, the highest shot count is at 1200. As you know, when you shoot the same equipment consistently you get a very good feel for what it is doing. This barrel at that shot count doesn't seem to be going quite as good as it once was. Certainly not as good as when it was younger between 300 and 800.

What I would like get is some background data as to when/if you are seeing similar patterns and barrel life for the 7SAUM? In the same way that we got a pretty good reloading road-map together for accurate loads for this caliber from everyone's separate individual testing in all corners of the country in the lead up to 2017 (which was incredibly consistent across the board and therefore arguably quite statistically significant), I am now also very interested to know what the empirical data says about accurate 7SAUM barrel life before a rechamber is necessary.

Making a science of the art is what accurate F Class is all about.

Cheers,
Marty.

bruce moulds
Posts: 2402
Joined: Sun Jun 19, 2005 4:07 pm

Re: 7mm SAUM Rechamber/Barrel Life

#2 Postby bruce moulds » Sun Aug 05, 2018 7:31 pm

marty,
the 284 is an honest workhorse.
keep safe,
bruce.
"SUCH IS LIFE" Edward Kelly 11 nov 1880
http://youtu.be/YRaRCCZjdTM

Marty
Posts: 29
Joined: Mon Jun 18, 2007 5:53 pm

Re: 7mm SAUM Rechamber/Barrel Life

#3 Postby Marty » Sun Aug 05, 2018 9:11 pm

Hmm yes, I see your point.
So just to gather further detailed and specific data and to help me more clearly understand, would a fair analogy be that when the moon is fullest and power lines are aquamarine, that the boiling billy makes cement reflect back to the hey days of life in the roaring 20's before prohibition?

Josh Cox
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Joined: Sun Jan 12, 2014 10:00 pm
Location: Cairns QLD

Re: 7mm SAUM Rechamber/Barrel Life

#4 Postby Josh Cox » Sun Aug 05, 2018 9:25 pm

Marty,

Purple monkey dishwasher,,,,, well it works for me.

RDavies
Posts: 1934
Joined: Sun Feb 12, 2006 7:23 pm
Location: Singleton NSW

Re: 7mm SAUM Rechamber/Barrel Life

#5 Postby RDavies » Sun Aug 05, 2018 10:27 pm

I have only put highish round counts through 2 SAUM barrels. One was used to fire 100 new cases at 2840fps before shooting about 750-800 rounds with 2209 and about 2960 fps. At this stage it started to lose its edge. I tried to tweek loads a bit more, but it just wasn't as good as it was. It was able to shoot 60s in good condition, but X count wasn't high. I then turned it into a 284 where I got another 350 -400 accurate rounds before it to lost its edge.

The next barrel was a different brand, known to last longer than some. I used it for approx. 600 shots with 2213sc at around 2960-2970fps for about 500 rounds. The barrel was OK, but not spectacular so I used it to fire another 600 rounds with new brass at a reduced load, around 2840 fps. After this I returned to 2960 fps loads for approx. 200 shots. By this stage it was losing its edge and starting to give a few erratic shots into the 5 ring and not as high X count.
From what I have heard from others and from what I have seen, I intend to rechamber back to 284 at around 800 rounds of 2209 and around 2960fps/
My 284s I used to run for around 1500 rounds or so, maybe up to 1800 max before they started to go off.

Matt P
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Joined: Mon Nov 14, 2005 8:22 pm

Re: 7mm SAUM Rechamber/Barrel Life

#6 Postby Matt P » Mon Aug 06, 2018 7:53 am

Hi Marty
I've only run 1 barrel out completely and it was Brux that was very accurate and it fell apart at around 1400, and my gut tells me that this probably isn't the norm. I think this one went a bit longer. From looking down a few barrels I think if you're paying someone to rechamber around the 800 mark, is as long as I'd go.
Matt P

bruce moulds
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Joined: Sun Jun 19, 2005 4:07 pm

Re: 7mm SAUM Rechamber/Barrel Life

#7 Postby bruce moulds » Mon Aug 06, 2018 9:42 am

Marty wrote:Hmm yes, I see your point.
So just to gather further detailed and specific data and to help me more clearly understand, would a fair analogy be that when the moon is fullest and power lines are aquamarine, that the boiling billy makes cement reflect back to the hey days of life in the roaring 20's before prohibition?


also, to quote a very famous and well known man.
"let the b.c. do the work"
keep safe,
bruce.
"SUCH IS LIFE" Edward Kelly 11 nov 1880

http://youtu.be/YRaRCCZjdTM

ajvanwyk
Posts: 243
Joined: Tue May 17, 2016 5:50 pm

Re: 7mm SAUM Rechamber/Barrel Life

#8 Postby ajvanwyk » Mon Aug 06, 2018 10:46 am

In the interest of statistical analysis here is my x3..

Barrel 1:
Bartlein 1:9 / 2209 / 180gn Bergers / Node velocity:2880 / Peak performance: 1,100 rounds
Barrel 2:
Bartlein 1:8.5 / 2209 / 180gn Bergers - Node velocity 2940 & 162gn Hornady ELD-M - Node velocity 2970 / Peak performance 700 / barrel showed 90thou runout when flyers were commonly noticed within a string. Possible cause: unrelieved heat stress? , dropped? don't recall this but who knows
Barrel 3:
Bartlein 1:8.25 / 2209 / 183gn Sierra - Node velocity 2780 / Peak performance 1,400 rounds

Barrel4&5 is Bartlein and Broughton and either just chambered or about to be, but will likely run 183gn Sierra and 2209... I am fairly certain that I'll be looking to run these at the top end, but time and the tea leaves will determine.
Albert
Rosedale Rifle Club
Victorian Rifle Association

BRETT B
Posts: 208
Joined: Fri Sep 30, 2005 2:37 pm
Location: PERTH

Re: 7mm SAUM Rechamber/Barrel Life

#9 Postby BRETT B » Mon Aug 06, 2018 1:13 pm

Marty , I have run a few Saum barrels out and found that with 2209 and 2940 avg I go for between 900-1000 rounds before I re chamber. I have gone to 1400 but found by then it was not worth the rechamber as the throat erosion was too great .
I have done 3 re chambers in the 900-1000 round mark , set them back 2 inches to 28 inch and found them to clean up like a new barrel. They also returned to excellent accuracy and would run the same load as previous but just slightly slower (20 fps) than when 30 inch.
I used one of these 28 inch barrels at S.A. Queens and the Nationals (used in the leadup)and it was as good maybe even better than my newer 30 inch. I have since put 860 on the second chamber and its still going well , is showing some firecracking so will be retired soon from Queens shoots but it was worth doing the re chamber at 1000 IMO.

I also just got 1 of my Canada barrels re chambered this week from 30 to 28 ( 920 rds) and tested it yesterday at 800m . Gave it the same load as previous and it shot 59.8/60.5/60.6/60.8 so thats ready for the next queens..
BRETT BUNYAN F CLASS OPEN SHOOTER W.A.

pjifl
Posts: 614
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Location: Innisfail, Far North QLD.

Re: 7mm SAUM Rechamber/Barrel Life

#10 Postby pjifl » Mon Aug 06, 2018 3:35 pm

I cannot answer the question because I have not run both my Saum barrels past 800 shots each. My policy has been to use a standard 284 back to 800y, then the Saum at 900, 1000y although enthusiasm did get the better of me the last Queens I shot and I used the Saum right through.

I reckon that going to a Queens with a Saum with 800 shots on it is not wise. Must get out the borescope and have a closer look. I am shooting a 6.5 these days !

Changing barrels half way through a Queens is always a worry with only 2 sighters. 3 would change the odds hugely but I will not labor that now. So in my opinion you really need 2 rifles set up.

The one thing I really wanted to say is that in the Worlds there are more 15 and 20 shot strings which complicate comparisons of barrel life. Probably worth keeping in mind.

Peter Smith.

BATattack
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Joined: Mon Dec 29, 2008 10:29 pm

Re: 7mm SAUM Rechamber/Barrel Life

#11 Postby BATattack » Mon Aug 06, 2018 5:00 pm

I reckon you need to be prepaired to do a re chamber around 900. If it looks and shoots great then leave it but I see my x count tapering at around 800.

Some say they get WAY more than that but as Phil says, I wouldnt want to be attending a major event. Club shoots you can afford to roll the dice and see how far it goes.

To me the SAUM is easy to get to shoot "well" but it takes more than some others to keep shooting at its best.

williada
Posts: 739
Joined: Wed Jul 22, 2009 12:37 am

Re: 7mm SAUM Rechamber/Barrel Life

#12 Postby williada » Mon Aug 06, 2018 5:02 pm

Similar question was asked of me a few years ago and current information is bearing out my reply at that time - a chamber nip 700-800 rounds to maintain peak accuracy. That being said, I used Bartman's 7 SAUM which was let go to 1700 rounds (I think from memory, Mike may be able to clarify that) before it was re-chambered. I gave it a remedial lap, coated lighter projectiles and changed the powder and it still performs superbly at 1000 yards. It does not have canted lands. It was going to be cut back for test purposes to examine vibration changes and velocity, but another 7 SAUM with 5R lands has been donated for that and I will see how Mikes barrel will last at circa 3030 fps as a separate test.

In my humble opinion, it is the bore that drives accuracy i.e. the top of the lands. There is no doubt the barrels with canted lands perform but standard lands may well be more consistent for a greater round count because it has a greater exposed surface area to heat and wear down. On the other hand, a canted land has a narrower top leading edge by way of design and therefore less surface area to resist wear where it counts with bore size which flows on to variable bore size in the length of the tube which does not assist grouping ability. It is much easier to do a remedial lap on standard lands by way of copper lap to tidy up the lands after lead lapping to penetrate the groove. Leveling up the land height gives new life. Of course the groove is less likely to wear as fast as the lands.

In the 1980's, I experimented with different land heights produced on test barrels for a manufacturer. I won a regional championship with a barrel which had a land height of .0015". It shot brilliantly for several hundred rounds but the wear factor soon killed it. But it did prove while fresh you only need land height that is sufficient to prevent bullet stripping. Bullet stripping is a separated issue from variable bore diameter.

Always been a advocate of a specialist long range rifle and now for practical purposes, with regards to wear and tear this makes sense too unless you can afford to burn steel.

bruce moulds
Posts: 2402
Joined: Sun Jun 19, 2005 4:07 pm

Re: 7mm SAUM Rechamber/Barrel Life

#13 Postby bruce moulds » Mon Aug 06, 2018 5:42 pm

and so the wheel goes round.
lee metford barrels were found to erode quickly with cordite, and william metford redesigned the rifling to be deeper, which became known as enfield rifling.
wear/erosion is probably the same, but more stuff to wear/erode takes longer.
keep safe,
bruce.
"SUCH IS LIFE" Edward Kelly 11 nov 1880

http://youtu.be/YRaRCCZjdTM

pjifl
Posts: 614
Joined: Fri Jun 17, 2005 12:15 pm
Location: Innisfail, Far North QLD.

Re: 7mm SAUM Rechamber/Barrel Life

#14 Postby pjifl » Mon Aug 06, 2018 6:17 pm

And when the US adopted the M17 (the US Enfield) in ww1 with British style rifling, there was much criticism. But it distinctly outlasted the US type rifling favored at the time. Perhaps not quite as accurate but more practical in a battle weapon.

But I am not sure this has much bearing on a solidly loaded SAUM blasting a high intensity Plasma into the barrel when one is after exquisite accuracy. Once this has etched between the steel crystals and found weaknesses and started pits and begins to form a rough surface, mechanical damage follows at an increased rate.

Peter Smith.

macguru
Posts: 1289
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Re: 7mm SAUM Rechamber/Barrel Life

#15 Postby macguru » Mon Aug 06, 2018 6:49 pm

You know , when some dude wrote a few posts back that he was only getting 8-900 rounds out of a saum before a rechamber , i was about to type that maybe he needed a few cleaning tips, ie carbon removal etc, but than i noticed that it was Rod and decided that he probably knew what he was talking about :)

still its a bit depressing to realise that just after you get a good shooter you have to plan for its demise and think about a replacement. sad but true !


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