What chamber to order for Nelson or Marvel, standard or Bullseye

I am putting together a bullseye gun and wondering if the tighter bullseye chamber will be a problem with my Federal Auto Match, CCI Target ammo? I have had problems with my Clark 22LR Barrel on my Smith 41 not able to shoot a full 900 without problems. I am thinking of going with Nelson's standard chamber but would the Bullseye chamber provide smaller groups using the ammo I have. I am not a good enough shooter to buy Eley or other top notch. What is your experience with the two? Thanks Tod

Get the match/tight chamber. They typically shoot better. The crap shoot is how the muzzle was cut: indicated vs. not!
Jon

The Nelson conversions that I have shot have the match/bullseye chamber, they all have shot extremely well. Optimize the lower for the conversion and it should shoot well.

Most Nelson’s shoot around 1.5” at 50 yds with cci sv. After recutting the muzzle indicated off the bore they drop down to .75”ish. 
So you can still shoot 900/900 with cci sv.
Jon

Jon Eulette wrote:Most Nelson’s shoot around 1.5” at 50 yds with cci sv. After recutting the muzzle indicated off the bore they drop down to .75”ish. 
So you can still shoot 900/900 with cci sv.
Jon

I’m kind of dumb, but I’ll ask anyway.  How else can you cut a muzzle, if not indicating off the bore axis?  A hacksaw and speed square on an old shotgun to shorten it for “farm” purposes is one thing. 

I wish I had learned to be a machinist. The world is your oyster.

RodJ wrote:  How else can you cut a muzzle, if not indicating off the bore axis? 

Indicating off of the barrel OD, which is the wrong way.

RodJ wrote:
I wish I had learned to be a machinist. The world is your oyster.

And sometimes a rotting whale washes up on the beach ;-)

Amazing!

I have to say that it never ceases to amaze me how something as relatively simple as cutting the muzzle end of the barrel (presumably in a 4 jaw chuck or whatever on a reasonably accurate lathe) so that it is concentric with the bore can make such a huge difference to the accuracy.

AFAIK both Marvel and Nelson market their conversions primarily to target shooters who obviously want the crowns of their barrels to be machined correctly. Why don't they do it that way at their factories/workshops? We all know the answer to that!

I owned a Marvel briefly, did not shoot great and saw no point keeping it. Maybe it just needed the muzzle fixing?

Never mind, at least it keeps the likes of Jon and so many other experienced and skilled smith's busy with routine improvement work.

I really appreciate Jon (and others) sharing their valuable knowledge on this forum.

I had a 7.25 High Standard barrel recrowned by a smith.  The 50y ransom groups improved from over 2" to under 1"

Another barrel thing I have come to believe is the bore-chamber alignment.  If you look through the bore from the chamber end and see uniform "lands ends", that barrel will probably shoot better that one where the lands ends are not uniform, showing the chamber is skewed off center.

I’m not sure how the current owner of Marvel Precision cuts the crown. I quit paying attention to Marvels when the new owner stopped selling individual replacement  slides. The early 2005ish Marvel’s had Shilen barrels and were outstanding. I just picked up another old one  Nelson’s are machined by MacMillan. They are CNC cut in a large. The barrels are probably held in a collet and they are not indicated off the bore; time is money. They used to hand cut the crown with a hand held reamer that piloted off the bore. Both methods are not acceptable for a match grade barrel in my very opinionated opinion lol.
I wish they would take the time to do it correctly, they make a great conversion. I’m not trying to bash anyone, just speaking my mind.
Jon

I have a Nelson barrel and an Advantage Arms barrel both prepared by Bob Marvel.  If I ever get the time I will Ransom them compared to regular Nelson.

A bit baffling that you’re paying not a minor amount of $ and the machining of the crown is suspect.  How much more does it cost to do it right the first time? (Not a rhetorical question)

I have an older Marvel in the soft case with a serial number F4xxx. Is that supposed to be a good barrel?  Test target button is 0.9+ inches.

Thanks and interesting info, as always.

CNC time is a dollar a minute give or take... machinist time takes more than minutes to indicate in... and likely costs more...

Except that, in a production environment, the muzzle crown cutter can easily be a piloted bevel cutter in a “floating holder”.  Not any slower, really, than coming in with a rigid tool.

IMO, a Nelson conversion IS a minor amount of money, considering what you're getting. As for the barrel, the lug is a separate piece. I dont know how it's attached, but if it's threaded in and torqued, it's possible the bore could be constricted ahead of the chamber. That WILL affect accuracy big time.

Mine has a c'bored flat crown. The edge break on it looks even, but there's the possibility the crown itself isn't square to the bore (I really doubt its not). Something else to pull apart and check ...

Concentricity of the chamber, as well as the crown, is considered critical in rifles, smallbore and HP. I can't think of any reason it wouldn't also matter with a pistol ... unless you shake like I do ;-) One could argue the crown would be more critical on a pistol, given the higher gas pressure with a short barrel.

Thanks for all the input, I didn't realize the Nelson took short cuts on the crown I guess after I order mine and shoot it to decide if a recrown is warranted. I am ordering the bullseye chamber per suggestions. Again I learn from all who responded.

Remember, your quibbling over 1-1/2” at 50 yds.
Yeah, 3/4 would be nice, but, it will still make hi master if you do your part.

I like having the absolute best shooting firearms I can get my hands on. If they don’t shoot well they are worthless to me. 
I had gotten an almost new 208 from a friend way back in the day. I switched from my Ruger mkii government to the 208. I was shooting about 40k r funds a year through that pistol. I had shot an 895/900 50 something X’s just before going to the AMU from the All-Reserve team. The armorers were lot testing ammunition and I had my 208 tested. It barely held 1.5” with the best lot of ammunition the AMU had on hand. So 1.5 is good enough to shoot some great scores
Jon

I wouldn't describe the use of a piloted crowning tool as a "shortcut".  It is pretty standard practice for "production" arms.  It is very labor intensive to set up a barrel in a lathe, indicate it to zero on the bore, then crown it with a facing tool.  I do this to all the barrels I use, but I consider it custom work, not production work, and I would probably charge $75-$100 to do it if I were in business.  That would add about $100 to the price of a Marvel or Nelson conversion unit.

james r chapman wrote:Remember, your quibbling over 1-1/2” at 50 yds.
Yeah, 3/4 would be nice, but, it will still make hi master if you do your part.

Until I can consistently score AT LEAST FIVE POINTS  on every shot at 50 yards, conduct dry fire and other training rigorously (and regularly), lose weight, gain grip strength, mental out completely on Lanny B and the PST etc., and know all the rules or at least know where they are, then 1.5” seems to be plenty accurate for this clown. 

I should probably sell everything but my Ruger MkII until I can put them all in the black at 50 yards. Or restrict myself to the Ruger until I hit some milestones, and look at shooting anything else as a reward.

Or, go to Perry with a .22 and 45 and shoot and watch

Of course I’m only an hour and a half from there

We (whoever that is) should have a winter “Perry” at Ft. Hood or JB San Antonio. Or heck, right here in Austin at Camp Mabry or Camp Swift just outside of town.

You people up in the Midwest live the life with the Cardinal place and others.

I had Alex at tenring recrown my marvel for a very reasonable price. I think it was like $40… problem solved. No Ransom testing but noticeable improvement in shots being on call with CCI.

I guess I got a bit bored today. Set mine up and recut it. It looked to be about perfect as it was. But it looks custom now.