Alternate method for determining rifling contact

[Pres100]

Oh, and you can't "feel" .001"!

You absolutely can feel 0.001" when it's done the way I described. When done the way that you have described it I'm sure you can't.

 

[Pres100]

Butch,I use the same gauge to measure my sholder bump. They are excellent.

 

[butchlambert]

Erik,
I will have to disagree. Depending on your neck tension, you could be pushing your bullets into the rifling. Yes, I have done and kept pushing my bullets back with the seater to help get the right seating depth.

 

[Erik Cortina]

Oh, and you can't "feel" .001"!

You absolutely can feel 0.001" when it's done the way I described. When done the way that you have described it I'm sure you can't.

:-X

 

[Pres100]

Eric, I'm not trying to turn this into a pissing match. You are a knowledgeable shooter and forum member who I do respect. But please tell me what the minimum tolerance fit that I can feel. What is it that I do feel dragging in the rifling ( and marking the bullet) when twisting it lightly by hand. When I bump the bullet down .001" at a time with my micrometer die and verifying it (COAL) with calipers until I don't feel it.
I fully uderstand the concept of throat erosion but here we are talking about the gauge. Please tell me the human capabilities when comparing verified measurements.

 

[Erik Cortina]

Erik, I'm not trying to turn this into a pissing match.

Me neither.

 

[gotcha]

Erick, No dissing intended here but there are many ways to skin a cat. No sense over simplifying either. Removing & replacing firing pin requires an additional tool also and varies in complication depending on firearm type. Our discussion is addressing the frustrations of obtaining precise measurements for bump & bullet seating. There's nothing simpler or more precise than a gizzy/stub for establishing bump that I've found. NOT saying there isn't a better way. Nothing simpler for seating depth on NEW bbl either and precisely establishes starting point of throat erosion. We've tried the slip fit route and found the method less than accurate. In the past I've gone w/ several operations of the bolt (eight or more) and gone w/ the measurement that most often repeated itself. I've also gone with a rectangular or square impression of lands on buffed bullet. Once the lands become rounded from erosion/wear THEN what do you look for??????

 

[Erik Cortina]

Let't not forget that all we are looking for is a reference point. Whether it's .020" in the lands or .100" off the lands. As long as you can accurately measure that same point again after the barrel has a few hundred rounds through it to keep lands/bullet relationship the same is all that matters.

If you run .003" or .001" neck tension does not matter, as long as the reference point is accurately obtained.

Gotcha, you can actually do this with firing pin in gun, all the bolt is doing is acting like a press.

Anyway, I agree there is more than one way to skin a cat, I just happen to like the easy way.

 

[gotcha]

Thanks Eric & Donovan, Judging by # of views this is all worth while. I agree w/ most of what you say. Maybe I don't fully understand the rest. It would seem that your method of measuring distance to lands is actually an estimate as opposed to a precise reading. Dependent on # of lands, Jacket alloy and thickness (compressability) and ogive shape & maybe other variables I've over looked. I know that if my bullet is imprinted by the lands I'm ITL. The actual amount is just a wild guess w/o a way to measure the depth of the imprint. I'm REALLY trying to get a better grasp of the bullet seating issue & have wrestled w/ it for some time now....................... Its better to be accurate than easy

 

[Erik Cortina]

Thanks Eric & Donovan, Judging by # of views this is all worth while. I agree w/ most of what you say. Maybe I don't fully understand the rest. It would seem that your method of measuring distance to lands is actually an estimate as opposed to a precise reading. Dependent on # of lands, Jacket alloy and thickness (compressability) and ogive shape & maybe other variables I've over looked. I know that if my bullet is imprinted by the lands I'm ITL. The actual amount is just a wild guess w/o a way to measure the depth of the imprint. I'm REALLY trying to get a better grasp of the bullet seating issue & have wrestled w/ it for some time now....................... Its better to be accurate than easy

Gotcha, the way I do it is not a wild guess, it's very accurate.

Like I said, all we are doing is finding a reference point, since seating depth testing will be done as part of barrel tuning.

 

[Nomad47]

I have found the simplest AND most accurate way is with the Stoney Point (now Hornady) tool. I will take ~5 measurements and almost always the measurements are within +/-.001" - close enough.

When I first started using the tool about 8 or 9 years ago, my measurements were all over the place and I also used the split case & cleaning rod down the muzzle methods, then averaged all three. But I guess I have developed a better 'feel' over the years and now the Stoney Point measurement is all I need.

 

[savagedasher]

I feel if you don't make your own from a case that has Ben fire formed in you gun you can be off.
Drop method hard touch soft touch don't make any difference. It is a reference and if done by the same person the same way the results will be the same. Good Shooting Larry

 

[mikecr]

I feel if you don't make your own from a case that has Ben fire formed in you gun you can be off.

That's a good point Larry, and it contributes to the Stoney Point inconsistencies. It's an issue whenever taking datum from shoulders, and with lower angle shoulders wedging muddles up accurate measure.

I'll throw in another method posted before for contrast:
I use an 'R-P tool' which is a purpose built cleaning rod really(with flat end & stops). Works very well.
In this thread WOODS talks about it with pics:
http://www.reloadersnest.com/forum/t...?TOPIC_ID=9027
This takes the measurement to the actual boltface(with it's slop removed), which makes sense -while you control headspace.

Then I make the dummy round with the matching OAL(to THAT bullet's tip), and measure Max OgvOAL(initial) with a Sinclair nut & log it. I keep the dummy round in a jag tube marked by bullet/chamber for setting up my seating die.
From that point all adjustments are w/resp to that OgvOAL using the nut.

If you go to setting seating depths off shoulders, you're adding shoulder variances to the measure. That's one too many variances to be valid(especially if you FL size).
The only thing I use my gizzys for is headspace measure(every one) while bumping.

 

[mikecr]

Wanted to add another view,,
Many arbitrarily choose jammed(~20thou from touching). In a practical sense, I think is more about reaching a pressure curve unobtainable without jam, in underbore cartridges, and at mother of all holy pressures(6PPC, 30BR, etc). And this is a significant work-around for reloading variances.
But I've yet to find this as best or even viable in longer range, normal capacity for bore cartridges.
Many LR people who are finally testing for best seating(to get the most from Berger VLDs) are finding that jam is not best -as assumed for so long. These shooters must balance wind drift with tune potentials, so their not using tiny flat base BR bullets in underbore cartridges. Their using long heavy boat tails with difficult to make in matching ogives, and larger cartridges burning slower powder.

I can imagine that jammed, and the need for it, follows erosion(I don't know that).
But I haven't found a need to 'chase the lands' when best seating is off the lands to begin.
My barrels have shot well, until they didn't, and this wasn't fixed with seating adjustments. It was because of throat constriction with erosion that could be temporarily fixed with JB paste & finally barrel setback. Wasn't a matter of seating.
I tested one barrel/load that was very particular in seating reqs. This was a 6.5wssm/139Laps with best seating 8thou off (+/-3).
At 850rnds, I measured 7thou change in MaxOgivOAL(combo of receding/angle changing leade) and wondered if seating adjustment was in order, so I re-tested. What I found was that best seating was still exactly where I had determined to begin(during brass fireformings).
I know this isn't much to go on, but it put me at ease about erosion & seating. So I thought I'd pass it on.

 

[Pres100]

Gotcha, Mikecr,Donovan, sacagedasher, Butch, Erik and everyone else.... Very good discussion, perspectives and experiences shared. We have a lot of differing opinions, experiences and approaches to doing things. Even though we may not all agree with each other on every topic, it makes for interesting discussion and a great place for sharing it.
Thanks and I look forward to more.

 

[lawrence97]

I have done what Erik mentions but my most recent barrel will leave the 5 rectangular/square impressions on the lightly polished bullet and as I back off from the lands I am still getting 5 very faint and long marks on the bullet but no defined square impressions.

So my question for the gurus is my baseline should be the the 5 very distinct rectangular impressions or when I stop seeing 0 marks on the bullet?

 

[Erik Cortina]

I have done what Erik mentions but my most recent barrel will leave the 5 rectangular/square impressions on the lightly polished bullet and as I back off from the lands I am still getting 5 very faint and long marks on the bullet but no defined square impressions.

So my question for the gurus is my baseline should be the the 5 very distinct rectangular impressions or when I stop seeing 0 marks on the bullet?

The 5 marks as I assume that will be the most cinsistent of the two. Use it as a reference point and go from there.

 

[Jnewman]

The way Erik does it is very simple and very accurate works well for me