Slow barrels and slow barrel makers

[SmokinJoe]

I was going to say about the same thing Boyd said, but he beat me to it. I have a 243AI long range varmint rifle that I started out using Norma brass, but was disappointed in results for pretty much same reasons as you. Then Lapua came out with 243 brass (this was quite a few years ago) & I switched - Wow, what a difference! So if your friends are using the Remington brass & it is tougher, that is probably the difference. Don't know much about this cartridge - who makes brass for it?

 

[Rustystud]

Not all barrels are equal. Land groove ratios have a dramatic effect on velocity and accuracy. I have had slow barrels and found that the barrel makers employee in charge of making barrels that day changed the dimensions on the cutter head and thereby changed the barrel land groove ratio. The rifle I chambered with one of those barrels developed pressure before it developed velocity. The barrel maker knew they had a problem and replaced the barrel as any good barrel maker would do.

I once had another barrel maker loose some of his experienced employees. He let out some barrels that were not properly lapped go to his customers and they had crazy extreme spreads due to tight and loose spots in the barrel, they would not shoot worth a dammed (flyers). The barrel maker denied he had any problems and refused to do anything about his lousy barrels. I know about a dozen gunsmiths who had the same problems and quit using this barrel makers barrels.

So I know not all barrels of a given caliber, bore diameter, land height and width, groove depth, width and twist rate are not the same.
Nat Lambeth

 

[fredo]

For whatever it's worth, I have a friend who built a 6.5SAUM on a Benchmark barrel and it's sucking eggs, too. Just can't get it to shoot ANYTHING. VLDs, Amax, JLKs...no consistency at all.

He used my GAP '4s' reamer, and every other rifle chambered by our mutual 'smith has been a hammer. Almost too easy to find a load, so we've not found the case to be inherently finicky to mess with.

That suspect rifle is now at a 3rd party, and he can't get it to shoot, either. Barring an extremely rare scope issue (its an ATACR), pretty sure that barrel is a turd. The BA is fully bedded & floated, so its either scope or barrel at this point...

Have read alot of good things about Benchmark barrels & not wanting to slam them, just passing some potentially relevant info along. I know your tales of woe with that rifle from another site, and load development shouldn't be that difficult. Something is wrong...

 

[clowdis]

This may be a stretch, but I think Benchmark may lap their barrels with a small amount of choke at the muzzle, I'm pretty sure they do their rimfire barrels that way. That would allow the bullet to start fast but slow down when it hits the choked part near the muzzle. Probably the only way to check this is to start cutting off the muzzle (not practical) to see what the speed does. Anybody have any thoughts on this?

 

[BoydAllen]

My friend has barrels that have choke (.0001 is all that you want.) and those that do not. The difference has hot shown up on the chronograph. I would not do the suggested experiment. Given that choked muzzles extend back several inches, you would be guaranteed to loose velocity. There is guessing, and there is measuring. It is better to know than to guess. When selecting a barrel brand, I suggest that you look at match equipment lists, for the kind of shooting and or similar caliber to what you plan on using.

 

[ebb]

I think that the powders you are using are too slow. I would think that powders ought to be close to what a 6.5-284 uses and those are all too slow for a 6.5-284. Ive had best results from H4831 and VV165.

 

[Shrek]

Powders are definitely not too slow. Can't even fill the case with h1000 or rl26 and there was good velocity gain when I tried Retumbo. With 140's H1000 is the go to powder and I'm pushing 150's. I'm suspecting the combination of a slow barrel and soft Norma brass being the culprits. I'm going to switch to 130-140 gr bullets for this rifle and use it on local deer and build a 6.5 WSM on the MRC 1999 action I bought and see what tough Winchester brass and more case can do with the 150 and 160 gr Matrix on my bench. Going to have to wait until January for that though. Hopefully my 7mm wsm gets barreled this weekend and I can get it going strong. Hopefully the Dan Muller cut rifled barrel is the ticket and I find shooting nirvana.

 

[Shrek]

The more I investigate the more I think it's tolerance stacking that's not stacking in my favor. I don't have an inside micrometer to measure the bore of my Benchmark barrel but talking to a couple of people they say that Benchmark makes their bores on the tight side of things and my Matrix bullets run to the fat and long bearing side of the equation and the Norma brass is soft and thick. All together it adds up to a slow rifle. Started another thread on bullets and barrels to explore it more. I'm going to look for some skinnier bullets to try in this rifle and maybe buy an inside micrometer to check the bore diameter.

 

[Shawnba67]

Buy a lead slug to measure your bore. Well cheaper.

 

[Raythemanroe]

Primers?


Ray

 

[JBT47]

A couple of years ago I woulda advised to try a Broughton 5C as I've had faster than expected MV's with Broughton barrels. However, I've recently replaced two of my Broughtons (which were shot out) with Bartleins. Well, both these Bartleins are faster than the Broughtons they replaced.

Bottom line seems to be that all the barrel makers make some that are fast and some not so fast. No measureable, objective way seems to exist which can predict this.

 

[butchlambert]

Dave,
What kind of inside mic will measure the bore? Slug it and measure or get a 25pin Deltronic pin set.

 

[ebb]

Try VV165 .

 

[KMart]

The more I investigate the more I think it's tolerance stacking that's not stacking in my favor. I don't have an inside micrometer to measure the bore of my Benchmark barrel but talking to a couple of people they say that Benchmark makes their bores on the tight side of things and my Matrix bullets run to the fat and long bearing side of the equation and the Norma brass is soft and thick. All together it adds up to a slow rifle. Started another thread on bullets and barrels to explore it more. I'm going to look for some skinnier bullets to try in this rifle and maybe buy an inside micrometer to check the bore diameter.

Dave, it has been a couple of years now.
It would be interesting to know how this project turned out for you and what were your findings

 

[Shrek]

I changed a couple of things at once so I don't know what fixed what but I'm getting 3050 now without any pressure signs now. I'm not home to look but off the top of my head I started using hBN to coat the bullets and bore , increased the jump , and turned the necks a thousandth thinner. All my pressure spikes went away and the velocity picked up. I got where I was ok with performance and have just been hunting with it. I think I could go back and wring a little more velocity out of it but it has been killing everything I shoot with it fine. I'm working very hard at building a shop to set up my lathe and mill in. When it's done I have a 6.5 Barrel and a 700 action that will be my first project. I'll be using the same reamer so I'll have something very close to compare sometime late this year or early next if all goes well.

 

[KMart]

I changed a couple of things at once so I don't know what fixed what but I'm getting 3050 now without any pressure signs now. I'm not home to look but off the top of my head I started using hBN to coat the bullets and bore , increased the jump , and turned the necks a thousandth thinner. All my pressure spikes went away and the velocity picked up. I got where I was ok with performance and have just been hunting with it. I think I could go back and wring a little more velocity out of it but it has been killing everything I shoot with it fine. I'm working very hard at building a shop to set up my lathe and mill in. When it's done I have a 6.5 Barrel and a 700 action that will be my first project. I'll be using the same reamer so I'll have something very close to compare sometime late this year or early next if all goes well.

Thanks for the update.

 

[Alex Wheeler]

What are you using for pressure sign? Some actions show ejector marks sooner than others and I recommend using heavy bolt lift as your main sign. Chamber finish has a huge role, freebore diameter and neck clearance also play a part. Un-true actions can show pressure signs sooner. All that aside, its bore area. I think barrels that are a little larger can shoot a little faster. 4 vs 5r does not seem to matter.

 

[ragsflh]

i just change my powders

 

[Shrek]

For pressure signs I use a number of things. Bolt lift , primer flatness, and ejector marks top the list. I really should go back and work the loading up again and see what I can get out of it.

 

[tvaught]

Daveinjax

What's the neck diameter of a fired case measure up as?