The club I will be shooting at for the next few months mainly shoot 20 shot strings when I have been doing the usual 15 shot strings most times. How have you found 20 shot strings go with the 284s and SAUMs? Does barrel life go backward quickly? Does accuracy fall off for you at the end of a 20 shot string?
How do 20 shot matches effect 7MMs?
- Thread starter 1KBR
- Start date
From my experience, NO on both questions. Takes my guns 35-50 shots before I notice( if even that few shots) a slight change in accuracy. Think it depends on the barrel. Obviously barrel temp does affect accuracy. Depending how warm air temps are and how fast the 20 shots are executed. I do have a 30 Cal factory barrel that only takes 30 shots before the fouling affects accuracy.
Heat, friction and pressure will all ill-effect a barrels longevity, especially under the stress of long shot strings. The more powder you burn, the higher the pressures and the longer the bearing surface is on a bullet, are all contributing factors in how long a barrel will last. The more the "overbore", generally speaking, the faster the throat will wear. Let's use an example to illustrate that point. A .284 Winchester has become "standard fare" at long range F-Open matches. You can neck it up to .33 cal and have a wonderful deer and elk cartridge. The expansion ratio is far different from that of the same cartridge necked down to 6mm. A .338-284, because of the "larger hole" coming out of the case, would not be considered an "overbore" by anyone's definition. The case capacities are the same, due to them being the same parent .284 case. However, all that powder being burned, exiting a considerably smaller hole, as in the 6mm x .284, will eat up a throat quickly compared to a .338 bore. That's why if you have a .300 R.U.M. shooting 200+ grain bullets with nearly 100 grains of powder, will burn up a barrel at a frightening rate compared to a .308 shooting the same bullets.
There are always trade-offs. If you want to shoot a 180-195 class 7mm bullet at 2825+, you have little choice but to use a case with enough powder capacity to push a heavy-for-caliber bullet at that speed. The more the powder capacity, the greater the heat, the more the wear on the barrel. However, as they say, there are always mitigating circumstances. If you use H4350 in your .284 with about 51.5 grs, you will be at about max pressure and the heat will be substantial. On the other hand, slower powders, like IMR 7828, VV N165 or even H1000 will produce less pressure due to the slower burn of the powder which in that case should create less heat. Whether or not your particular barrel will like those powders, only your barrel can tell you. H4350 is a well established powder in the .284 with 180 class bullets, however, it is about as fast of a powder you can reasonably use. By the same token, H1000, if your barrel likes it, will be about as slow of a powder you can reasonably use. So if you are worried about barrel replacement fairly often, and still want the benefit of H-I-G-H B.C. 7mm projectiles, try the slower powders. But remember, the instant you pull the trigger for the first time on a new barrel, you have started down the road to the eventual demise of the barrel. You might as well get used to that, it is a fact of F-Open life..
There are always trade-offs. If you want to shoot a 180-195 class 7mm bullet at 2825+, you have little choice but to use a case with enough powder capacity to push a heavy-for-caliber bullet at that speed. The more the powder capacity, the greater the heat, the more the wear on the barrel. However, as they say, there are always mitigating circumstances. If you use H4350 in your .284 with about 51.5 grs, you will be at about max pressure and the heat will be substantial. On the other hand, slower powders, like IMR 7828, VV N165 or even H1000 will produce less pressure due to the slower burn of the powder which in that case should create less heat. Whether or not your particular barrel will like those powders, only your barrel can tell you. H4350 is a well established powder in the .284 with 180 class bullets, however, it is about as fast of a powder you can reasonably use. By the same token, H1000, if your barrel likes it, will be about as slow of a powder you can reasonably use. So if you are worried about barrel replacement fairly often, and still want the benefit of H-I-G-H B.C. 7mm projectiles, try the slower powders. But remember, the instant you pull the trigger for the first time on a new barrel, you have started down the road to the eventual demise of the barrel. You might as well get used to that, it is a fact of F-Open life..
My buddies and I have shot a number of overbore cartridges in 20 shot matches over the years. In addition to extending barrel life using slow burning powders in moderate loads, we extend barrel life beyond what a lot of other shooters report by using all or most of the allotted time for the 20 record shots. Repeated shooting of 20 record shots in 10-15 minutes will wear a barrel much faster than 18-20 minutes.
So, you mean 30-50 shots in a string before accuracy goes out? I am not too concerned about 20 shot strings in the cooler months but when spring and summer comes around again I was wondering if the heat from reasonably fast 20 shot strings start causing accuracy issues?
I sometimes set out to shoot slowly, especially on practice days but in the heat of competition, when a condition holds it is mighty tempting to rattle them down range quickly.
I realise that burning out barrels is a fact of life in F Open, they are a consumable in my opinion. I was just wondering how much the extra 5 shots in a string cause, in both accuracy and throat movement?
CJ6
Silver $$ Contributor
I doubt there's a definative answer (number wise) for that,except to say the longer the string ,the faster the wear
Not sure if you are the gent I was discussing this with at Lodi, but yes I certainly had one barrel which ever reliably started to leak shots out after 16 shots or so string fire. I could usually scrape in a 15 shot match plus sighters but sure did not want to use unlimited sighters with it. I tried different powders etc as we discussed but it more or less stayed the same. I fixed it by only using that barrel in 15 shot matches were it went fine.
That said, I tried my 300WSM which I thought was immune from hot barrel accuracy loss. In perfect conditions last week, even it started to lose its edge toward the end, just not as badly as the SAUM I discussed with you.
That said, I tried my 300WSM which I thought was immune from hot barrel accuracy loss. In perfect conditions last week, even it started to lose its edge toward the end, just not as badly as the SAUM I discussed with you.
I've put up to a 100 rounds on my .284win. barrel with no problems/loss in accuracy. I've seen 7 short mags go as long in between cleanings with no issues. 7 short mags are toast between 600-800 rounds. Maybe you can squeeze close to 900 but they're done. The .284win. I've seen barrels go 1500+ on round count.
Keep in mind as the barrel wears it will change over the course of it's life. You have to learn how to pay attention to it. It will tell you what's going on you just have to learn how to read it.
As has been mentioned......how hot you get it, the type of powder the type of bullet etc...all have an effect on barrel life. The bullets jacket material will vary from lot to lot and can effect fouling and the accuracy etc...there are more variables then just the barrel itself. Also how the barrel is made can have an effect on barrel life as well. How you clean, what you clean with, how often you clean etc...all are variables as well that can have an effect.
If you cannot get more then 15 rounds thru the barrel and the accuracy starts going sour......then the first question I ask is how many rounds are on it and what is it chambered in? If it's a low round count and your have accuracy problems after 15 shots being fired then there is something some where causing an issue in my opinion. Then you got to start digging into it. If it's got a high round count on it then it's probably time to pull the stick and get a new one on.
Later, Frank
Bartlein Barrels
I shoot a 7mm saum In F open. I tend to shoot fast when things are good. I have had no problem with shots leaking out at the end of a string(only shoot 20 shot strings). I believe powder choice in the larger cases will help barrel life. I have tried H4350= short barrel life(500-800)H-4831 a little better.1000-1400. And N-165 or H-1000 will give you the best barrel life in these larger cases. My choice is H1000. you will only loose .001" of the lands per 100 rounds(tested over 650 rounds on current barrel). I have been keeping a close record of my last barrel. I will post pics of the numbers and bore pics showing fire crackling at the end of the life of the barrel. The plus to the 7mm saum 1.)primer pockets hold up 2.)You can run a comfortable 2950fps with 180 class bullets. And 2850fps with 195 bergers. Whats not to love about the 7mm SAUM!!!! remember As many have said F-Open barrels get replaced more often.
Oh yeah I shoot Bartlein 5R barrels
Oh yeah I shoot Bartlein 5R barrels
Thanks for the reply Frank. The main barrel I have the issue with is a 7 SAUM running H4831sc and 180 VLDs and I have recently started using 183 Sierras with same results. The barrel started showing this loss of accuracy when hot at around 100 rounds old and has continued up until now, approx. 1000 rounds old. I am about to have 2" cut off and have it re-chambered to give it a new lease of life. The barrel does not foul. After letting it cool down from a 20 shot string, it is straight back to peak accuracy and if I do 3x 15 shot matches, the last target is as good as the first. I suppose it could just be how the barrel is as my 30 cal is not quite as bad and my newest 7mm SAUM is only 150 rounds old but appears to hold great accuracy up to 25-27 shots during load development when I got a bit rushed and could give it a cool down period.
I'm hearing you on the extra heat in SAUMs with H4350, it is why I moved to H4831sc. The accuracy loss with H4350 also started by shot 15 while with H4831sc I was able to shoot a few more rounds before it opened up. I never did try H1000 in this barrel. After talking to others, I will try N165 when I get this barrel re-chambered.
Yes. When my personal gun (308) get around 50 shots thru it, the accuracy starts to fall off. It's a factory barrel and fouls relatively fast. Not an issue because I know it occurs. No, 20 shot strings in warm weather and even when the barrel heats up will not throw my accuracy off. Just seems to be the fouling.
Hmmmm.....if the barrel shoots good and you are not pounding it/getting it really hot....but if you shoot it fast/get it hot you lose accuracy? Is that what your saying?
If so then I would like to throw something at ya. If while you shoot it and it gets really hot and you see the group/accuracy wonder but you then let it cool and it starts out at the original point of aim etc....then I would say the barrel has a lot of residual stress in the blank or it's a barrel that has a bad bow in it. The steel has a memory and when it cools the barrel will go back to where it started. This might be what your seeing.
Your not cleaning it in between stings are you?
Later, Frank
Yes, that's right Frank. I shoot it at regular F class speed so not rapid fire. I don't think the zero shifts, the lost shots go in any direction, the group just grows (not shocking, but not 10 ring). Once I let it cool for 30 minutes or so (in shade in summer), it shoots at more or less same POI. No I don't clean between strings, I clean at the end of the day. Once it cools for a bit, without cleaning, the X ring accuracy returns. I have not had this issue before so I think it could just be a barrel glitch.
Yes, I think I am the one you were talking to. It seems we have the same. Was your 300 WSM the same brand barrel as the main one you had issues with?
Not really. But, our F-Class Open mindset is not on just a "20-shot string"!! Most of our competitions, we will be shooting three 20-shot strings in one day. I do not sense any degradation in accuracy after 60 records shots, and some 20 sighter shots in one day using either the Win .284 or the 7mm RSAUM. Barrel life will wane, but that's just a cost of doing business!
Dan
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