Testing chambers for Lapua use............

750k22 said:
Any updates??
Click to expand...

I have not had a chance to revisit this testing yet (my apologies), life has been getting in the way of the shooting recently!

I do plan to complete the evaluation of the barrels I started with - and have two additional blanks I wanted to run thru the paces too (just to see if the behavior was somewhat predictable).

I have also had some conversations recently with Gordon Eck (which I have found really interesting) - it isn't often you get to compare notes with someone about what is working and what isn't. I really hope we can compare notes more often (shooters and smiths) - we might get some of this figured out after alL! LOL

For those who have not tried any of the Lapua ammunition yet there are some very good lots out there right now. I am still (until I can quantify the testing) using a 2 degree leade chamber with great results - engraving just past the second band (using a barrel datum face to leade tangent of around .570" in .2215" x .2170" barrels).

My apologies for the delay, I really wanted to post some additional data way before now, but have found it just impossible (so far!!)

More later,

kev
 
Hi Kevin

Just to throw in some measurements,
I have an Octagon and it was shooting ok, but occasional flyers were teasing.
Of course one is to blame the ammunition...
But since I´m still experimenting with it, we changed the engraving by lenghtening the chamber. Now the chamber is .675 and in Lapua bullet shows engraving of .059, so just to the back edge of first grease groove. Looks promising.
I also checked some of my good shooting sporter barrells and they have something in common, .02 engraving.
I also checked what kind of difference would variations in ammo lenght make, went through good lot of Center X and I shot the shortest ones into same hole, @25m, then took the longest ones, length difference about .008 and shot those through the same hole. Looks to me as when you get your chamber in the ballpark to your barrels internal dimensions, you can stop worrying about the ammo length at least.
Looks by the results in 2012 you have found good lots from Lapua.

BR Taavetti
 
Taavetti said:
Just to throw in some measurements,
I have an Octagon and it was shooting ok, but occasional flyers were teasing.
Of course one is to blame the ammunition...
But since I´m still experimenting with it, we changed the engraving by lenghtening the chamber. Now the chamber is .675 and in Lapua bullet shows engraving of .059, so just to the back edge of first grease groove. Looks promising.
I also checked some of my good shooting sporter barrells and they have something in common, .02 engraving.
I also checked what kind of difference would variations in ammo lenght make, went through good lot of Center X and I shot the shortest ones into same hole, @25m, then took the longest ones, length difference about .008 and shot those through the same hole. Looks to me as when you get your chamber in the ballpark to your barrels internal dimensions, you can stop worrying about the ammo length at least.
Looks by the results in 2012 you have found good lots from Lapua.

BR Taavetti
Click to expand...

Taavetti:

Thanks for the reply - its great to hear from you!

My apologies for not posting on this thread - I have had so little time to do any meaningful testing. I was using a new three groove Hart last season - after I got it setup in the spring, I spent time training (and stopped any additional development). The blank was intentionally long, and I initially tried several configurations of 1.5 degree leade chambers without much promise. I went back to my old standard 2 degree, and ended up with a "C" dimension (from the datum face to the tangent of the leade) of .600".

In the spring I chambered several barrels for my 2000 action (and several barrels for others) - for my blanks, I conducted the same test (two Shilen ratchets, and four harts - 3 and 6 grooves). I guess my only conclusion is that (for me) the 2 degree leade is the most consistently good chamber profile (in most all cases) - with Eley and Lapua ammunition. I can certainly get the 1.5 degree leade to work - but in almost every case, when I set the barrel back and rechamber with a 2 degree, base accuracy is better.

I am still trying to develop an opinion regarding depth - dimensions from .580 to .620 of so work well (that I am pretty sure of!).

It is very difficult to do any meaningful testing because you change a barrels overall behavior when you set it back - so I never know if the improvement was chamber related, or just a node shift from the small change in length. I have just tried to look for some consistant behavior displayed by sample size.

The shift in leade placement does seem to be much more effective with the 1.5 degree leade. Not only did it imptove accuracy, but it also extended accuracy between cleanings (which is fairly important shooting SB prone - unless you want to clean between matches). In every case (which is only a few barrels) this was true - for me.

Thanks again for the post,

kev
 
Gentleman,
I hope I can add something here worth your time. This has been a very good conversation about Lupua ammo and the chambering it likes. I have a Bill Myers built benchrest rifle. It has a benchmark two grove reverse taper barrel. Bill set this rifle up to shoot lupua ammo that was requested by the customer. I’m the second owner. I’m wanting to rebarrel a tubro action that I have with a barrel that shoots lupua ammo. The reason, I live in Arizona and have a lupua testing facility 125 miles from me. I made a mold of the existing chamber .It was inspected on a smart scope built by O.P.G. This is what I found. Chamber dia.2245 , lead 1.5 deg. Chamber length appears to be around .675/678.The chamber has a very slight taper less than a deg. That may be part of the tolerance used by the reamer manufacturer. I don’t know. The bullet is engraved very little .010 at most. The worst part about that gun is it has a time action. But it does shoot lupua ammo and shoots it very well. The time is just a pain in the ***. Hope this adds a little to the discussion.
Russ
 
Last edited:
clarification of findings?

Hello Kevin,
I am very interested in your chambering experiments and was wondering what your findings are. I think a reamer with a 2 degree lead and straight sides is the way to go but as you have said the depth makes a difference. I read an article about bill myers chambering ideas and he does not believe in a lot of engraving.

regards,
Andrew
 
George Stidworthy

Kevin, I was googling up George Stidworthy and yall have a common thread,he won the NRA-U.S. Cartridge Company Trophy in `68,`69,&`71;you won it `08. I `m buying his 2- Karl Kenyon 37`s he won them with and was researching his past ,his daughter won it `77 &`82 do you think she used his rifles also ? Hey was you shooting Lupua in `08 and was that a rifle you built?
 
Last edited:
SLICK WILLY said:
Kevin, I was googling up George Stidworthy and yall have a common thread,he won the NRA-U.S. Cartridge Company Trophy in `68,`69,&`71;you won it `08. I `m buying his 2- Karl Kenyon 37`s he won them with and was researching his past ,his daughter won it `77 &`82 do you think she used his rifles also ? Hey was you shooting Lupua in `08 and was that a rifle you built?
Click to expand...

Slick:

Thanks for the post, it has been really quiet here!

George and his daughter were some of the very best prone shooters this sport will ever know. If you look at the records (unbroken) they have, it is just amazing. I honestly don't think we will see them challenged in our lifetime, and I have spent a lot of time wondering why. I believe we have better rifles / barrels (generally) - and I refuse to believe that the old "Paper Box" Eley was as legendary as I have heard.

I do know that Karl Kenyon did all of George's (and probably Mary's too) gunsmithing. Karl is another person who will never be replaced - what an amazing craftsman he was.

I probably helped that George (for many years) was an Eley distributor - I have heard the story told over and over among the older shooters regarding the extensive testing George did (all rumors, mind you!).

I would love to see someone of the upper levels of BR today, shoot (from a bench) an equal record score to Mary's in 1987 - 400-40x's with an additional 40 consecutive x's, same target, same distance, in even mild Perry winds. That is no slight to BR (you guys are amazing) - it is a tribute to just how amazing Mary was.

Yes (to answer your question), I have always built my own rifles. The rifle I used in 2008 was an Anschutz 2000 series action, Hart 17 twist barrel and Eley ammunition (my sponsorship with Lapua started just after Perry in 2008). I did win the Metric National title in 2010 with Lapua ammunition though! The Tenex lot number was 1006-01159 (of which I still have a case in storage!! LOL)

I have been building rifles (rimfire is almost all I do) since about 1995 - I just got really tired of waiting a year to have a rifle built! I am REALLY impatient! I found a great lathe and a mill and never looked back.

I don't have time to do it in quantity, but have always built guns for my friends (Paul Gideon won his titles in 2003 and 2006 with some of my work). Some people using Palma rifles I have built have also done well. In recent years, I find myself getting beaten by something I worked on on a VERY regular basis! LOL

Thanks again for the post, have a great 2013 season!

kev
 
general said:
Hello Kevin,
I am very interested in your chambering experiments and was wondering what your findings are. I think a reamer with a 2 degree lead and straight sides is the way to go but as you have said the depth makes a difference. I read an article about bill myers chambering ideas and he does not believe in a lot of engraving.

regards,
Andrew
Click to expand...

Andrew:

I am currently using 2 degree straight sided chambers, setup at about .580" in depth. To be honest, this is the same chamber I have used for years (for both Eley and Lapua ammunition).

I just have not had a chance to revisit my testing, and do not have enough data collected to be confident enough in another chamber (to use it in competition). I will, and when I do I promise I will post additional data.

On the Lapua bullet, this setup engraves just past the second band FYI.

Thanks again for the post,

kev
 
1006-1159 Tenex

Kevin, that lot is 7 years old,I have some 1008 lots that was pretty good at one time, many people have told me that the ammo falls off considerably after a couple of years and I`m spinning my wheels saving it. Not just the waxing properties but the internal compontents . Now Craig Young of RBA fame says injest that he has nothing but some old bullets and he`s gonna shoot them up before he buys any thing and will just have to take what is given because of the old ammo. (Craig is one of the cheapest a$$ on earth) Have you shot any of that old 06 lot lately to see if it has fallen off any?
 
Last edited:
Benchrest Rifle

Kevin have you ever built a BR rifle ? The Turbo is the king and it`s Clones(Diorio New Turbo, X-III,& Falcon ) are having success in BR ,have you ever played around with one of these ? Camp Perry is coming up ....are you competing this year?
 
SLICK WILLY said:
Kevin have you ever built a BR rifle ? The Turbo is the king and it`s Clones(Diorio New Turbo, X-III,& Falcon ) are having success in BR ,have you ever played around with one of these ? Camp Perry is coming up ....are you competing this year?
Click to expand...

Hi Slick - thanks for the post!

I do have some experience with what you might call BR actions. I have barreled several Swindlehurst actions for others and myself (two of my personal prone rifles are build on them). I have also barreled some 10X actions since their introduction.

No Turbos (or clones).............yet!

I also have a G&E Racer now, which will get a few new barrels turned for it this fall. That should be interesting - the configuration of turned sections and O rings (in the chamber and forward shank sections) should be challenging.

And yes, I will be at Perry. This year is a big one - the Pershing team is selected from the top 10 (from the first two days iron sights aggregate). The UK team has already been selected - the match will be shot shoulder to shoulder at Perry.

Have a great summer,

kev
 
SLICK WILLY said:
What countries send Teams other than the UK ,.... China? What are the dates for the competition?
Click to expand...

The Pershing match is just between the UK and USA - it happens every 8 years, and is held in the states.

The Roberts team match is also held every 8 years, between the UK and USA, but is shot at Bisley during their National Matches (the matches overlap on 4 year cycles).

Both are represented by the top (10) from each country - selected by their respective processes (the US selects their team from the top 10 in our Nationals iron sights aggregate).

The Pershing will be shot on a special day - cleared for this event at the SB prone Nationals. It is scheduled for July 23rd, 2013.

Are you planning to visit?

kev
 
Hello Kevin

Hello Kevin,
any more experimenting with chamber length?

Regards,
Andrew
 
the general said:
Hello Kevin,
any more experimenting with chamber length?

Regards,
Andrew
Click to expand...

Andrew:

Thanks for the post, I had forgotten about this thread!

The last post was over a year ago, and yes, I have continued testing and tuning in an effort to optimize round nosed ammunition (specifically Lapua offerings, due to my involvement with them).

I have a chamber profile that I really like, a refined version of which I used at the NRA smallbore National Matches this year. For $25,000 I will tell you about it (just kidding!).

It is a 1.5 degree leade angle reamer, with a small amount of taper - about .0005" (I believe in a lot of unconventional wisdom these days it seems - a small amount of taper in a chamber is one of them). I have also found that engraving depths of around .030" have tested consistently well with this ammunition (another unconventional idea). I have read that engraving amounts this small are only useful with non-concentric chambers machined by bungling gunsmiths (unless they are at 6 o'clock I guess) - but I can assure you it works very well with something reasonably centered too! LOL.

Running testing protocall on many barrels thru the past few years has been really interesting - there are so many "false positives" with RF ammunition and the optimization of it. I just continued to experiment until I found some consistency. I know this is not perfect by any stretch, but I would chamber the barrel at initial fitting deep - document the engraving amount and test it (with all mass in place as it would be during use). I would then set the datum face and shoulder back (for my threaded actions) and re-test.

I admit I don't fully realize all that is happening here - you are adjusting length and harmonics as well as chamber engraving as you go, but it was repeatable to the point that it could not be ignored.

The chamber in this configuration also seems to shoot well longer (which is important to prone shooters like me).

I also like to finish the chambers (no chamber should EVER be un-finished) with a #5 bastard file - but that is just between you and I (again, just kidding!).

As a side note...........I also love cut rifled barrels (oh, the humanity!).

All the best, thanks for the post!

kev
 
trying to figure it out

Hi Kevin,
i check out a few sites and do a little posting every now and then on them. I am just about to get my custom gun back and ready to play with. It is a new turbo with rc muller 4mi barrel chambered by Brett here in Australia. Brett communicates with BC a fair bit and i am pretty sure that the chamber is a 2 degree leade straight sided one. I am building another custom based on an Anschutz 1413 54 action. i notice of all my 22's that my two 54's are very forgiving with ammo choice. They are both early models pre 1968. i am wonderind if you know the chamber specs on the early 54's. I am pushed for time right now but will post here again in the next day or two. Good to see that you are still experimenting.

Regards,
Andrew
 
The .030 depth figure is how I set up my chamber for Eley. On a comparison check, the Lapua front band is about .015 engraving depth on the same chamber. I have not checked how much lot to lot variation there is with either brand. That may be more than .015. When I ran experiments on engagement depth, I found that .030 or .125 were about the best accuracy wise. Anything that engaged deeper into the third band was bad. In between those 2 depths were OK. 1.5 and 2 degree didn't seem to be any different.
 
Last edited:
still collating info

Hello Kevin,
i do a lot of researching on the internet and have created a file on my computer where i stick it all. i keep adding to it and read over it every so often to see what is conflicting or supporting. It seems that chamber info is a very hotly debated subject. I think that a small amount of taper and consistent twist rate are basic requirements and if you dont have those to start with you are bound to fail. Going over my file i read that Bill Myers and Chet Amick both thought that bore diameter was important also. Bill appears to have had a lot of input into the benchmark two groove barrels. I am trying to get my head around the idea of why bore diameter would be so important. I know that the lead bullet must be swaged down from the chamber into the barrel so it is being being squeezed down in diameter anyway. I know that a gentleman here in Australia many years ago created a rifle with a 20 cal barrel, i believe it was called the extruder. The bullet was squeezed down to 20 cal and i believe the theory was to gain velocity but they were not super accurate because the bullet became too long to stabilse properly. Lilja tight bore barrels have always been very good shooting barrels. There must be a range of bore diameters that are good to use. I am still learning a lot and must say that i still do not fully understand the whole picture. For instance everyone is worried about where the bullet is engaged in the rifling and alignment etc. but i am a little uneducated about how the bolt holds the base of the case so that it is centred with the bore, if it is not then isn't that a problem? Or maybe the alignment is close enough because the bullet is being swaged into the bore and then must follow the path of the barrel? Maybe i just over think some things. I really enjoy this thread and the way everyone is actually offering up information, maybe one day we will have it figured out. I have started using the prx tuning method and find that it works for me and makes sense to me in one way but if positive compensation rather than a stopped muzzle is the actual reason for tuners working then i cant see why it works. i still have so much to learn (lol). Another aspect that i don't understand is i have read several times that a rimfire barrel when lapped only uses a certain grit compound, i would have thought that the smoother the surface finish of the bore the better. Surely the rougher the finish the more spots on the bore for leading and other crud to stick to.

Also Kevin i found an interesting article on testing using two shot groups and statistical analysis that can be used to give you a very good measurable level of confidence in the data. The article also shows you how to do it all in an excel spreadsheet very easily. www.public.iastate.edu/~jessie/PPB/Stats/Testing loads.htm is the link. A very interesting read.

thank you everyone for the conversation on this thread i am thoroughly enjoying it.

Regards,
Andrew
 
Last edited:
You must log in or register to reply here.
Top Bottom
Back