Which 7mm ??? picture of new case added
- Thread starter coyote
- Start date
Measure the difference in case capacity as a percentage and apply that to the number of rounds of useful life given in the previous post. Calculate the number of rounds that way. A very coarse determination (there are so many variables), but it will get you in the ballpark. - dan
I do not know how many a 7mm SAUM would go but a good SWAG would be about 1200 rounds. The Brits would chamber up 3 - 4 barrels at a time for each rifle when they were campaigning the 7-300WSM's (slightly smaller than a 7WSM-longer neck) just to make it through the season. I understand that they have dropped the 7-300WSM and returned to straight 284's. Another alternative would be 300 SAUM or WSM shooting 210's. Mine has shot 1700 rounds and is still a tackdriver. Steve
Mystic Precision
CGN Ultra frequent flyer
- Location
- Summerland, BC
The better the ballistics, the shorter the lifespan. I have chatted with shooters who are now seeing only 700rds before loosing match quality accuracy.
Barrels do not last long and bore life should only be considered from the perspective of making through a long match. In Open, they are very much a consumable and have to be budgeted that way.
The larger 30cal does offer a longer bore life no doubt but at higher recoil so there are always trade offs.
The smaller cases will last longer but you give up ballistics. See my first post. How important is ballistics in your strategy?
With the 6.5's, 270's and 7mm hotties, better keep a few barrels in the works if you plan to practise, shoot several matches a season and be as competitive as possible.
In my last year using the 260AI/ Mystic. I had 3 rifles going - one for development (hopefully 20 to 40rds), one for matches (up to 1200rds, more if I felt daring, less if the rifle was shot hot), one for practise (another 300 to 800rds of useful life, also used for fireforming work).
It gets expensive, time consuming and a logistical headache. I am much happier in FTR and my 223. Barrel 1 has crossed 3000rds and still shot in the 1's at 100yds last time I tested it. Now to see how it does at 300m and 500m.
Jerry
Barrels do not last long and bore life should only be considered from the perspective of making through a long match. In Open, they are very much a consumable and have to be budgeted that way.
The larger 30cal does offer a longer bore life no doubt but at higher recoil so there are always trade offs.
The smaller cases will last longer but you give up ballistics. See my first post. How important is ballistics in your strategy?
With the 6.5's, 270's and 7mm hotties, better keep a few barrels in the works if you plan to practise, shoot several matches a season and be as competitive as possible.
In my last year using the 260AI/ Mystic. I had 3 rifles going - one for development (hopefully 20 to 40rds), one for matches (up to 1200rds, more if I felt daring, less if the rifle was shot hot), one for practise (another 300 to 800rds of useful life, also used for fireforming work).
It gets expensive, time consuming and a logistical headache. I am much happier in FTR and my 223. Barrel 1 has crossed 3000rds and still shot in the 1's at 100yds last time I tested it. Now to see how it does at 300m and 500m.
Jerry
I am averaging 3140 fps with my 7wsm pushing 180gr bergers. This is from a PGW Coyote and 24" barrel. I would say maybe my chrony is out but the ballistics support it. My rifle is consistently in the .3s-.4s out to 300m and I regularly shoot 500-900m behind my house. Barrel life... I don't know, 600-800 seems a bit low. I figure 1000-1200 but I'm not an f-class shooter. I will find out early next year.
I like the 7wsm but load development was frustrating to say the least. I tried about 40 different combinations before I found the 180gr/reloader 25 load. I will try 175smks when I get a chance(probably next year), I have heard good things about them too.
162 Amaxs didn't work
160 Accubonds didn't work
150 Sciroccos were pretty good
168 Bergers were also pretty good
180 Bergers worked the best and were more consistent.
These are just my findings and of course individual to my rifle
I like the 7wsm but load development was frustrating to say the least. I tried about 40 different combinations before I found the 180gr/reloader 25 load. I will try 175smks when I get a chance(probably next year), I have heard good things about them too.
162 Amaxs didn't work
160 Accubonds didn't work
150 Sciroccos were pretty good
168 Bergers were also pretty good
180 Bergers worked the best and were more consistent.
These are just my findings and of course individual to my rifle
I am averaging 3140 fps with my 7wsm pushing 180gr bergers. This is from a PGW Coyote and 24" barrel. I would say maybe my chrony is out but the ballistics support it. My rifle is consistently in the .3s-.4s out to 300m and I regularly shoot 500-900m behind my house. Barrel life... I don't know, 600-800 seems a bit low. I figure 1000-1200 but I'm not an f-class shooter. I will find out early next year.
I like the 7wsm but load development was frustrating to say the least. I tried about 40 different combinations before I found the 180gr/reloader 25 load. I will try 175smks when I get a chance(probably next year), I have heard good things about them too.
162 Amaxs didn't work
160 Accubonds didn't work
150 Sciroccos were pretty good
168 Bergers were also pretty good
180 Bergers worked the best and were more consistent.
These are just my findings and of course individual to my rifle[/QUOTE
What is your zero and what are your drops out to 1000 yards?
Thanks
Elmer
I like the 7wsm but load development was frustrating to say the least. I tried about 40 different combinations before I found the 180gr/reloader 25 load. I will try 175smks when I get a chance(probably next year), I have heard good things about them too.
162 Amaxs didn't work
160 Accubonds didn't work
150 Sciroccos were pretty good
168 Bergers were also pretty good
180 Bergers worked the best and were more consistent.
These are just my findings and of course individual to my rifle[/QUOTE
What is your zero and what are your drops out to 1000 yards?
Thanks
Elmer
This has been an interesting meandering thread. I concur with Jerry that if you are looking to build a new rifle either based on an existing case or a wildcat (why you build a wildcat is up to you, its kind of like asking why climb a mountain… because its there) it is best to start with the bullet you want to use and then design your case to optimize its performance.
My first F-class 7mm was a 7mm WSM throated for the Berger 180gn vld, these bullets tend to have an accuracy note around 3000fps, If you cannot reliably get them near this node you are not likely to get maximum performance out of them.
The .284 is a great case, but it will be hard to get 180gn bullets to shoot consistently at 3000 fps with these. Don Nagel came in second in the recent US nationals shooting a straight 284 combined with Matrix ballistics 168gn 7mm VLD bullets. He told me his results were much better using these lighter bullets. He is of course a world class shooter, but his choice of a lighter bullet for this case should not be ignored.
When it came time to build a 7mm wildcat I chose Matrix ballistics 190gn 7mm VLD’s. I found that I could not reliably get these above 3000fps using my 7mm WSM setup. I looked at the Shehane but I did not think It has enough horsepower for 190gn bullets. I have seen several top shooters struggle with the Shehane using 180gn bullets so I decided not to pursue this.
The SAUM will handle the Berger 180's but I was not convinced that they would maximize the potential of the 190's
My final choice was a wildcat based on the 376 Steyr, using this case, a Kreiger 28 inch bbl, and Matrix Ballistics 7mm 190gn vld’s I was able to easily achieve an accuracy node at 3050 fps. After 800 rounds the borescope showed moderate cracking in the throat, I would put the life of this bbl at 1000 to 1200 rounds based on what I saw. My current bbl is 32 inches and I am now at an accuracy node at 3150fps, using a slower burning powder. At 600 rounds the throat shows fine cracking, the wear at this point is minimal.
FYI pic’s below
I have a 7mmstw reamer with a 310 neck [I think] that I only cut one chamber and one seater die with maybe I should build one of these and have all the boiler room I need .
My idea originaly was to build something semi durable but maybe going for maximum ballistics would be the way to go.
After looking for a bit of info on a 7stw barrel life on the net some guys are claiming 3000 rnds with heavy bullets and slow powders and some are saying 1000 what to beleive maybe 1500.
My idea originaly was to build something semi durable but maybe going for maximum ballistics would be the way to go.
After looking for a bit of info on a 7stw barrel life on the net some guys are claiming 3000 rnds with heavy bullets and slow powders and some are saying 1000 what to beleive maybe 1500.
It looks like an ultamag shortened up a bit with an improved shoulder.
It is not only shorter, but also narrower, the web measures .507 vs .551 for the ultramag. The case measures 1.954 at the shoulder. Part of the strategy was to keep the case volume (77gn) such that I would have close to 100% fill to achieve the accuracy node of 3150 fps. I started with N560, but this year my best results are with N570.
As far at the STW it is a great cartrige, I actully just picked one up for hunting, Depending on your use the belt may cause issues with brass life if you intend to shoot it alot and want to re-use your brass as much as possible. If you want uber case volume you could always go with a 7mm Booboo
A few things come to mind here.
The guy that builds a 7 STW for hunting out west might have 2000 rds through it and still get good accuracy, but he is not submitting the barrel to the same rigors as an f class shooter who might fire 400 rds over a few days, a few times a season. He also probably fires a 3 shot group and calls it good. I don't play the open game because I don't want to buy my barrels in threes, and I don't have the machining ability to do my own installs. If I was going to do this, I'd set the action up for simple, straightforward barrel swaps, and have three identical barrels done at the same time, find the best one to use to the most important matches, the second best for day to day competeing/backup, and the third for load development/experimenting.
Claimed velocities can also be misleading. I shoot .308 in F/TR. My barrels are 30-32", and I routinly get 155 bullets to 3000 fps, and 185's to 2750, and 210's to 2600+. The guy shooting a 24" barrel won't get those velocities, or will be really straining things to get there.
I think Jerry and Mark are spot on about choosing the performance standard that you want, and then chambering accordingly. I would add that brass quality needs your attention as well. Exhaustive case prep is bad enough for 100 pcs. I take 4-500 rounds to a big event like nationals. I'm very interested to hear how the Norma 300 rsaum brass works out. I think I'd be tempted to design a reamer around that brass w/ a skim neck turn is nessesary.
just the random thoughts of an F/Tr shooter loking through the fence...
The guy that builds a 7 STW for hunting out west might have 2000 rds through it and still get good accuracy, but he is not submitting the barrel to the same rigors as an f class shooter who might fire 400 rds over a few days, a few times a season. He also probably fires a 3 shot group and calls it good. I don't play the open game because I don't want to buy my barrels in threes, and I don't have the machining ability to do my own installs. If I was going to do this, I'd set the action up for simple, straightforward barrel swaps, and have three identical barrels done at the same time, find the best one to use to the most important matches, the second best for day to day competeing/backup, and the third for load development/experimenting.
Claimed velocities can also be misleading. I shoot .308 in F/TR. My barrels are 30-32", and I routinly get 155 bullets to 3000 fps, and 185's to 2750, and 210's to 2600+. The guy shooting a 24" barrel won't get those velocities, or will be really straining things to get there.
I think Jerry and Mark are spot on about choosing the performance standard that you want, and then chambering accordingly. I would add that brass quality needs your attention as well. Exhaustive case prep is bad enough for 100 pcs. I take 4-500 rounds to a big event like nationals. I'm very interested to hear how the Norma 300 rsaum brass works out. I think I'd be tempted to design a reamer around that brass w/ a skim neck turn is nessesary.
just the random thoughts of an F/Tr shooter loking through the fence...
Mystic Precision
CGN Ultra frequent flyer
- Location
- Summerland, BC
Please remember that F class competitors toss barrels that would make the average hunter smile for days and tell grand stories.
For an Open rig to toss all their shots into a 1" or smaller group at 300m, isn't a big deal. That IS the expected performance and that is for 17rds!.
Being able to hit a 5" circle at 1000yds means accuracy BETTER then that.
Tell a hunter that you can hit a coffee can at 1000yds after 2 sighters and they will think you are so full of it. But that is exactly what F class is all about.
When I hear or read "so many rds of accurate life", I always ask the question - what does accuracy mean to you?
There is simply no way an STW is going to give you 1500rds of F class accurate fire. I would be surprised if it would give you 800rds.
My max tolerable accuracy is 1/3 min for anything I would take to a match. 1/4 min or better is the goal.
Most hunting rifles are sub MOA once that hero group is excluded and many are shooting well over 1 MOA at distances we play at.
You can get a whole lot more barrel life when your groups are allowed to triple or quadruple in size.
If you want to play with the best ballistics, accept that this will require barrels and $$.
But when your total cost to get to a match is $1000, whats another $100 in barrel cost to have a chance at the plastic?
Jerry
It is not only shorter, but also narrower, the web measures .507 vs .551 for the ultramag. The case measures 1.954 at the shoulder. Part of the strategy was to keep the case volume (77gn) such that I would have close to 100% fill to achieve the accuracy node of 3150 fps. I started with N560, but this year my best results are with N570.
As far at the STW it is a great cartrige, I actully just picked one up for hunting, Depending on your use the belt may cause issues with brass life if you intend to shoot it alot and want to re-use your brass as much as possible. If you want uber case volume you could always go with a 7mm Booboo
Could you educate me a bit on the 7mm stair ,what case is it based on and are you getting over 3100fps out of 180's ?
Mystic Precision
CGN Ultra frequent flyer
- Location
- Summerland, BC
Of the various Norma brass I have seen and used, I am very impressed with the quality. I am shooting some 6PPC and it is dead on right out of the bag.
I am running them at a decent clip and the primer pockets have held up just fine. Can't say they will be old gen lapua tough but certainly enough for magnum pressures.
I think there may be some restructuring going on with corp Norma with the Norma brand getting the "good" stuff and the L brand maybe more a consumer product?
You should be very happy with the brass if you choose to go this route.
Jerry
I don't shoot competatively but easily could. My custom 7mm saum( 0.315 neck) is built on a Barnard action,Lilja barrel , Robertson Composited GBF stock and topped with a S&B 12-50x56 PMII is an absolute hammer.I have had sub 1 inch groups at 500 yards( but most are in the 1 3/8 to 1 1/2 area. I am still on my first barrel but have 2 more waiting in the wings already chambered and threaded. The Norma brass I got from you made things easier that's for sure.
The 7mm Stair is based on the 376 Steyr ( http://en.wikipedia.org/wiki/.376_Steyr), the name was a play on the phonetics of name of the host case.
The shoulder is pushed forward, most of the taper is removed and the shoulder angle changed to 40 degrees. Case capacity is 77gn.
The first year I used this I had a 28inch 1.25 inch straight bbl, with Berger 180gn VLD and Hybrids, with N560 I was able to get these to 3100fps. I never competed with these as I switched to Matrix Ballistics 190gn VLD's, my new bbl is 32 inches (Tapered) and I now use N570 and push the 190's to 3150 fps.
I have used Matrix Ballistics bullets for the last year and a half, I shoot both his 190's in my 7mm Stair and his 175's in my 6.8mm Stair. As far as I am concerned these Canadian made bullets are as good or better than anyone else's
Awesome. I'm really glad to hear that, I think I will try some as well. Any experience with the 30 cal bullets at all?
It is not only shorter, but also narrower, the web measures .507 vs .551 for the ultramag. The case measures 1.954 at the shoulder. Part of the strategy was to keep the case volume (77gn) such that I would have close to 100% fill to achieve the accuracy node of 3150 fps. I started with N560, but this year my best results are with N570.
As far at the STW it is a great cartrige, I actully just picked one up for hunting, Depending on your use the belt may cause issues with brass life if you intend to shoot it alot and want to re-use your brass as much as possible. If you want uber case volume you could always go with a 7mm Booboo
How certain are you that the web is .507 ,could it be .501 I searched the net for cartrge dimensions on the steyr case and only found one drawing that showed a .501 web.
The reason I ask is I might be able to short chamber using an stw reamer and come up with something interessting,just a thought.
