Opinion on Benchmark 2 grooves barrel

Evelio said:
Kevin
The PTG Myers reamer have a 1.5 degree leade as you stated, It has spiral flutes, and no build in stop, but I do have and adjustable stop on it, so I can change the amount of engraving. Right now the barrel in question shows .115" from the face of the cone to the inner face of the rim with the Lapua round nose, and .090" with the Eley EPS bullet. As I stated before, it shoots the Lapua great.
I also have two other reamers, PTG for the LILJA tight bore barrels with a 2 degree leade, they have a build in stop, and are the ones that I used for the Silhouette rifles that I have re-barreled with LILJA barrels, which by the way, are winning Nationals, and State championships. Must of them use SK Standard Plus ammo. but the Eley still shoots great on them.
Do you think that the 2 groove barrel is more sensitive to the amount of engraving in the bullet versus the 6 grooves ?
I also tried a Rock Creek barrel 4 grooves, and encounter the same problem with the EPS bullets, I went ahead and run the Lilja reamer with the 2 degree leade, and it started shooting bug holes.
I am tempted to either go another .030" deeper on the existing chamber, or take a chance, and run the Lilja reamer thru it with a .216" bushing. The flyers that I am getting now are driving me crazy, I do not thrust the gun as is for serious competition.
What do you recommend ?
I can always just shoot Lapua ammo. on it, but I still think that it should be able to handle both brands competitive.
Evelio
PS did you ever work for NOV.???
Click to expand...

Evelio:

Thanks for the reply!

The internal bore dimensions control engagement IMHO, I have not noticed any perticular preference regarding groove counts and engraving depth, but each barrel is a story on itself!

Personally, when I fit a barrel I look for the consistency a properly setup chamber provides. After I get that, I begin to set the crown position back incrementally in an effort to get good baseline accuracy for fine tuning (with a muzzle device or extension tube). It is labor intensive, but I have not found a better way to get the most from the system. If I had to guess, I would bet the inconsistency you see is a function of too much engraving (which the 1.5 degree seems more sensitive to). I would indicate the barel back in, and go in another .030" and retest. Typically, I setup the chambers deep for the initial testing. If I need to, I can use the trued datum surfaces I turn on the barrel OD to set back the cone breech and choulder positions to get additional engraving (without rechambering).

Regarding your question..........I don't know what NOV is? Could you please elaborate?

Thanks,

kev
 
Evelio said:
Kevin
I was just thinking about the previous posting, and remember that when slugging the 2 groove barrel it took a lot more pressure to push the slug than it did with a 6 groove barrel, and it makes sense, since there is a lot more lead being displaced in the 2 groove.
Even not being official, my understanding is that the average speed in the Lapua ammo. is around 1072 and I have been shooting the ELY anywhere from 1054 to 1061, maybe I should try something over 1070 which I think I do have some Tenex at 1078. I will try it next week.
Evelio.
Click to expand...

Sorry..........just noticed the second post..........

Lapua speed varies just as any manufacturer's ammunition does. The latest shipment had factory velocities from 324mps all the way to 332mps (1062 to 1089fps). These velocities are always a little faster than what I see in my rifles (I am not sure what their testing protocall is, or what the barrel specifics are). I typically see speeds about 10 to 15 fps slower in my rifles.

Good luck with your testing!

kev
 
Kevin,
With any 2 groove work you might have done, have you always used a reamer?
 
tim said:
Kevin,
With any 2 groove work you might have done, have you always used a reamer?
Click to expand...

Tim:

I have, although it is pretty tedious work!

I was amazed many months ago when Mr. Gorham posted pictures chambering with a small boring bar. I purchased the best I could find, and tried to replicate his results (setting the cross feed at 2 degrees). My bar uses a very small precise carbide insert - which is part of the problem I think. You need to run carbide at higher rpm's. but with that small radius it's hard to develop any tool speed.

Additionally, it's hard to limit deflection in the boring bar (the tool diameter is small too).

Anyhow - I worked with it over several weeks and finally gave up, I could get good concentricity, but the surface finish was terrible (for me at least!).

If you don't push the reamer hard (go very slowly), at low rpm, with a good cutting fluid you can get good chambers in 2 groove barrels. A reamer by design wants to follow center, especially once some cutting length has been established.

I would love to watch Mr. Gorham cut a chamber (just once!) LOL

All the best,

kev
 
I wouldn't be surprised if there's two involved, a different one for the throat.
 
Get a small, solid bar

kevinnevius said:
Tim:

I have, although it is pretty tedious work!

I was amazed many months ago when Mr. Gorham posted pictures chambering with a small boring bar. I purchased the best I could find, and tried to replicate his results (setting the cross feed at 2 degrees). My bar uses a very small precise carbide insert - which is part of the problem I think. You need to run carbide at higher rpm's. but with that small radius it's hard to develop any tool speed.

Additionally, it's hard to limit deflection in the boring bar (the tool diameter is small too).

Anyhow - I worked with it over several weeks and finally gave up, I could get good concentricity, but the surface finish was terrible (for me at least!).

If you don't push the reamer hard (go very slowly), at low rpm, with a good cutting fluid you can get good chambers in 2 groove barrels. A reamer by design wants to follow center, especially once some cutting length has been established.

I would love to watch Mr. Gorham cut a chamber (just once!) LOL

All the best,

kev
Click to expand...

I got one that is both small and rigid. Not that much materiel has to be removed so with a rigid bar, and lite cuts, finish seems pretty good. I have done a few test chambers with it and they look OK to me. Every Rimfire chamber I have looked at have circular grooves at the leade and done with reamers, and, not by me! How much worse cold it be? Chamber finish, within reason, isn't a big issue, from my experience with CF rifles, at least. Real smooth ones will cause cases to stick when they shouldn't.

What I believe I am seeing is the same as is seen wit CF rifles, how much Jam is what makes a bunch of the difference in how rifles shoot. Finding and shooting ammo that is exactly the same length in a chamber that likes that amount of jam seems to be what to strive for. The jury seems to still be out, however, although there has been quite a bit written lately that makes this conclusion seem somewhat true.

Pete
 
Using collets for re-chambering, etc?

I have been wondering if it is feasible to true up a section of the barrel as one does the machine work for chamber and crown work, to be concentric with the trued bore so that a collet could be used for future work on the barrels(s). I don't know if collets are accurate enough so that not having to re-zero every time would be necessary. Does anyone have any experience with this?

Thanks,

Pete
 
Last edited:
Kevin,
NOV stands for National Oilwell Varco, the company I retired from, one of the vice presidents had the same name as yours, and was a Canadian, Just checking it was not you.
The weather have been horrible, no chance to do any further testing. I do have another Benchmark 2 grooves barrel chambered for a Stillers/Myers action, not being used, it has a 6" bloop tube, I am going to re-chamber it for the Turbo with a 2 degree leade and see if it will shoot the Ely EPS ammo. with no flyers.
Evelio.
 
Evilio

Evelio said:
Kevin
The PTG Myers reamer have a 1.5 degree leade as you stated, It has spiral flutes, and no build in stop, but I do have and adjustable stop on it, so I can change the amount of engraving. Right now the barrel in question shows .115" from the face of the cone to the inner face of the rim with the Lapua round nose, and .090" with the Eley EPS bullet. As I stated before, it shoots the Lapua great.
I also have two other reamers, PTG for the LILJA tight bore barrels with a 2 degree leade, they have a build in stop, and are the ones that I used for the Silhouette rifles that I have re-barreled with LILJA barrels, which by the way, are winning Nationals, and State championships. Must of them use SK Standard Plus ammo. but the Eley still shoots great on them.
Do you think that the 2 groove barrel is more sensitive to the amount of engraving in the bullet versus the 6 grooves ?
I also tried a Rock Creek barrel 4 grooves, and encounter the same problem with the EPS bullets, I went ahead and run the Lilja reamer with the 2 degree leade, and it started shooting bug holes.
I am tempted to either go another .030" deeper on the existing chamber, or take a chance, and run the Lilja reamer thru it with a .216" bushing. The flyers that I am getting now are driving me crazy, I do not thrust the gun as is for serious competition.
What do you recommend ?
I can always just shoot Lapua ammo. on it, but I still think that it should be able to handle both brands competitive.
Evelio
PS did you ever work for NOV.???
Click to expand...

If the rifle shoots center-x really good why not just shoot it and save the 4 dollars a box on your ammo,LOL.

Mike Cameron
 
MIKECAMERON said:
Yes it was.
Click to expand...

Mike:

I also wanted to congratulate you on your National title. Although I don't shoot BR competitively, I have an idea of the comittment and skill it takes to win at that level.......that was some amazing shooting!

Personally, I have been very happy with the Lapua ammunition I have used / tested thru the years. in my equipment, it is second to none.

It looks to me like I should be testing more Center X!!

Again, congratulations on your win, all the very best in the future!!!

kev
 
Mike

Congratulations on your win...

It was my first match and had a great time.

A question to you and Kevin..Where can you purchase Lapua and be assured you are getting the newest lots.

Tom Wilkinson
 
Tom W said:
Mike

Congratulations on your win...

It was my first match and had a great time.

A question to you and Kevin..Where can you purchase Lapua and be assured you are getting the newest lots.

Tom Wilkinson
Click to expand...

Kevin, thank you for the congrats coming from a national champ that has made my day, thanks again.

Tom, get in touch with Bob Collins, e-mail Bob@22rf.com Thank you as well

Mike Cameron
 
Lapua chamber debth

A couple of years ago I pulled a BM 2gr that was beginning to loose it's edge after about 8 or 9 cases of ammo and switched to the BM 3gr. I had been using Eley at the time and so I put a short chamber in it and it shot pretty well. Last year I decided to try Lapua since I could take the short 1250 mile drive to the test center. Who doesn't like a road trip?! I found the Lapua shot great for about 15 or so shots then started to throw shots. Checking with the bore scope showed that with the short chamber the carbon fouling was building up in front of the leade in the rifling. I deepened the chamber about .010 and it moved back into the leade area. I continued to deepen the chamber until it engraves just to the back of the second canalure or knurling, which ever you want to call the little dimples. Since then I have added 2 other 3 grooves to other rifles and all have done quite well. 2 have .2255, 2 degree and the last one is a .224, 2 degree. I think the .224 fouls slightly less but otherwise see no difference.

I've tried a boring bar to chamber but found I get a better finish with a really sharp (hand honed) reamer. Guess my machining skills aren't quite up to it. The one down side is the three gr. is a bit tedious to dial in!

Dennis
 
Maybe Soft

The only BM 2G I have had, seemed soft. One squib round of Eley was all it took to ruin it. Be sure and watch your target after every round to be sure it left the barrel. If not, the next one will ruin it. Other wise, several local competitors swear by them and beat me constantly.
 
I have been investigating different barrels for my next build. I have gotten as many different answers as there are barrels. For no particular reason I decided to go with a Muller. I kind of wanted a Shilen Ratchet, but the wait time is at least 8 months.
 
Fred J said:
The only BM 2G I have had, seemed soft. One squib round of Eley was all it took to ruin it. Be sure and watch your target after every round to be sure it left the barrel. If not, the next one will ruin it. Other wise, several local competitors swear by them and beat me constantly.
Click to expand...

What kind of ammo did you get a squib from Fred??
 
Kevin,

On another forum, in a faw away place some of the recent discussion involving Lapua suggests possible changes to bullet design that might benefit performance. Any thoughts on the matter?
 
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