how much cant would this round have with no ejector acting on it? maybe the same amount due to gravity?
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Gunsmithing Why do you need to true the bolt face?
- Thread starter MarineMD
- Start date
how much cant would this round have with no ejector acting on it? maybe the same amount due to gravity?
Krieger put an add in May 1997 issue of Precision Shooting magazine, claiming that Bart Bobbitt used one of their barrels to shoot a 3.325" 20 shot group at 800 yards with a 308.
David Tubb may have doped the wind better than Bart at Camp Perry, but Bart has a history of phenomenal shooting in low wind.
In 1992 -2000 Bart posted at rec.guns on the usenet part of the internet.
Since the world wide web part of the the internet got gun forums,
Bart posts at Long range hunting forum and The Firing Line Forum.
Bart does not weigh each charge.
Bart does not de burr flash holes.
Bart does not weigh brass.
But he is adamant that truing the bolt face has a big effect on long range accuracy.
David Tubb may have doped the wind better than Bart at Camp Perry, but Bart has a history of phenomenal shooting in low wind.
In 1992 -2000 Bart posted at rec.guns on the usenet part of the internet.
Since the world wide web part of the the internet got gun forums,
Bart posts at Long range hunting forum and The Firing Line Forum.
Bart does not weigh each charge.
Bart does not de burr flash holes.
Bart does not weigh brass.
But he is adamant that truing the bolt face has a big effect on long range accuracy.
Wow, I thought this thread was dead!? I was away doing my 2 week annual reserve training... Anyway, I am not suggesting that truing the bolt face will make it significantly weaker. I am suggesting that truing the bolt face beyond factory spec will not affect accuracy since there are so many other variables as mentioned above. The explosion comment was superfluous, I think...
There are a myriad of things that we do to make our guns shoot better. Some of these things might even be worthwhile for some of us. One person's experience might be anecdotal. This does not mean it is not correct, just that it might not be statistically significant.
I'll stray into the world of high end bicycles and hopefully make a point. All riders, professional and recreational, place a premium on weight. This is despite the fact that it is much easier for the rider himself to lose weight than to take weight off the bike. The world of professionals is different than the world of recreational cyclist. Professionals can sometimes win by the width of a tire. In this world, an ounce of weight on the bicycle can cost you calories going up some hill in the middle of the race leaving just that little bit less energy at the end of the race when a tire width might make a difference.
The recreational rider will never notice this difference: never (just ask old guys on their $7000 bikes that get beat going up hills by delivery boys on their 30 pound bicycles). Yet, they will insist on taking that ounce off the bike paying great expense to do so.
Having said that riding a 15 pound bike is a way nicer experience that riding a 20 pound bike.
Most of us will never shoot like Bart, ever, so what is correct for him may not be correct for all of us. Also, Bart may be adamant about truing the bolt face, but he still might be wrong. In the 80's, professional cyclists were convinced that narrower tires were better. Now, we understand that these tires are actually detrimental to end performance. The world was once flat, etc... Just like bike though, shooting a $4500 custom rifle is a hell of a different experience than shooting the $400 Walmart special.
I wish we could line up 100 shooters from this site, have them shoot a 700 based rifle that has been all trued up except of bolt face. We can average those groups. Then, we would true the bolt face, without telling the shooter that this had been done, then have them all shoot groups again. For those of you with research backgrounds, I know there are lots of other things we'd have to do in order to get statistically significant results, but I think a little pilot study like this would be fun.
One could take several ( one hundred is a bit much-in fact 10 would deliver a statistically significant solution) very good shooting rifles, remove the bolts, place a small strip of "tape" to one side of the bolt fact, thus creating the "out of square" condtion. and fire another group (10 round groups). Repeat with the tape place on the opposite side. I believe we would see accuracy drop off, in both cases, but less for one side than the other (as there might be a counter action for spring tension) in all cases I would place the tape from 0 degrees to180 degrees , then doing the opposite 180 to 360 ( the right side then the left side). One offs seldom prove anything, but sometimes they do, anyone can do this with one rifle, and see for themselves-rather than arguing about how many teeth a camel has, go open a camels mouth and count!. The more true, and more square an action is, the better it shoots, I'm fairly sure most gun smiths and those that have had actions trued over the years will agree with that statement. Most world records (the accuracy kind-real targets measured holes) are held with trued actions, albeit custom or factory-the straighter and more square actions have delivered the goods. Those that want to argue that is doesn't work, are making an extraordinary claim, one that flies in the face of historical evidence, therefore the burden of proof is on them. Those producing and using square and true actions have their proof-in the form of world records.
I love this idea! We can come up with a difference we're trying to find and then power the study accordingly. We'd have to get guys to do it, then this would be the equivalent of a multi-center study. We can get people who've had Remington 700s with actions and bolt faces trued. How do we know the tape will work? Compressibility?
We'd need to find out the average deviation of a factory bolt face and show that the tape will reproduce this condition. I like it.
I think all you'd need are trued bolts to start with, then using the same tape, same caliber, same load, measuring the compressibility of the tape would be nice to know, but would only become important, if in fact, the purposeful and deliberate act of making the bolt out of square showed up in the results, as my hypothesis would lead me to believe. How much out of square leads to reduced accuracy, and the amount of reduction could be interpolated at a latter time. I don't believe the need for the 10 shooters to be in the same place at the same time is necessary. Each could do the experiment on their own, if they found a reduction in accuracy, then it would warrant further testing. Brass life would also be an easy "extra" piece of data that could be collected, although much more time consuming, as they brass lot, sizing die etc. would all be a variable. I too, believe there would be a difference in brass life, when comparing square bolt faces to out of square bolt faces-but that would be a far more entailed set of trials, not one an individual could do with good quality reporting in a couple of hours. If, and I believe it would, the out of square bolt face shows a reliable loss in accuracy, then the question of factory bolt face's degree of 'out of square' would be worthy of investigation. The entire exercise would be to demonstrate the efficacy of trueing, or squaring. The ability to quantify the maximum allowable etc. would be a much longer exercise-one that has most likely been done, I wouldn't be surprised if FN has done so. I don't think to many large companies add an expensive and time consuming operation to a product without demonstrating to themselves that for dollar spent, the results are worth the effort. Have they or will they publish this info-I Doubt it! This is the type of research that keeps one companies rifles on top, why give up this info to your competition? Nonetheless, I'll bet it has been done, and has been quantified.
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pawprint2- what I was thinking is that a "trial protocol" would be developed. This protocol could then be published and whoever wants to participate could. The problem is that I, like most of us, have to make a living. I agree with you, I bet that data is out there.
You could always use a x-ray to see the cant and the difference in it from trued to factory. This could be done with the same barreled action and two different bolts. The accuracy would still need to be tested though.
Does the man doing the chambering not take this into consideration like he should with the bolt being pushed up in the rear?
Does the man doing the chambering not take this into consideration like he should with the bolt being pushed up in the rear?
Lots of words, but very few numbers. We did get at least one attempt at a DOE (Design Of Experiment), but unless some testing occurs, this is just yet another exercise in mental masturbation. I don't even see the point of the whole mess, since it's highly unlikely that anyone would true an action except for the bolt face, or would true the bolt face without performing any other work. If you're in there doing a bunch of other work, might as well true the face; otherwise, just leave it alone and stop worrying.
On the topic of ejector influence - yeah, the ejector plunger provides an off-axis force, but it's serving to push the angled shoulder of the cartridge into the angled recess of the chamber. Even if the ejector is trying to cock over the neck of the cartridge to the opposite side by providing a moment about the Z-axis, the geometry of the mating surfaces is serving to keep the cartridge centered (at least to the extent that the brass and chamber are of similar dimension in this area, such as with fireformed cases). The neck clearance would seem to have little effect on cartridge alignment.
On the topic of ejector influence - yeah, the ejector plunger provides an off-axis force, but it's serving to push the angled shoulder of the cartridge into the angled recess of the chamber. Even if the ejector is trying to cock over the neck of the cartridge to the opposite side by providing a moment about the Z-axis, the geometry of the mating surfaces is serving to keep the cartridge centered (at least to the extent that the brass and chamber are of similar dimension in this area, such as with fireformed cases). The neck clearance would seem to have little effect on cartridge alignment.
PTG, makes lots of great stuff, one of the things they make are new bolts for Savage rifles (and others), if they[PTG bolts] are anything like the rest of the high quality stuff that PTG makes, I'm betting they are very "true", I can think of at least one example, where someone would build with a true bolt face without trueing the rest of the action. In fact, I'd bet there are a large number of people, when installing a new tube on their Savage rifles, in fact up grade to the PTG bolts. How much slop is okay, has always been my question, many have commented on it, but none seem to have a number, or a percent. I'm still betting there is such a number, and the really good mfgs know it. They've done the work, they also know on average what the effect will have on accuracy. The could also quantify the cost effectiveness from their standpoint. Fancy paint with skulls don't really make rifles shoot better, but I'm guessing trueing the bolt fact has a measureable effect.
Way to find an ever-so-small hole, and then needledick it to death. Well done.
"Slop" where? Bolt body to bolt bore clearance? I know at least one well-known 'smith here has weighed in on the topic. Or are you talking about the sloppy joes you had for lunch?
And without numbers, all you are doing is guessing.
PTG and Savage are both well respected, old, established companies, your crude and uninformed comments regarding these two- speak for themselves. As we were discussing bolt face trueing, as in PTG's bolts, I believe, one, with a modicum of reading skills, could surmise that the "slop" I referred to was the out of square condition of a bolt face, as in one that was true vs one that was out of true, how much out- makes a difference- was the topic. As far as what I had for lunch, I don't see where that could have any bearing on the subject, but based on your comments, may I suggest you take another midol. Regarding "without numbers, all you are doing is guessing", how true, if you had read the entire string-you would see that is in fact the crux of the conversation, reading comprehension and retention, from post to post, does not seem to be your strong suit. Perhaps you should wait until a better time of the month before commenting further.
"Slop" is not normally how one would describe the condition of two planes deviating from perpendicular, but whatever - we live in the era of using words however the hell someone wishes, regardless of whether it is correct or not.
I've installed a few PTG bolts on my personal Rem700s, so I'm somewhat familiar with them in that application (never used 'em in a Savage, so I can't comment about those). Have you performed any gunsmithing with them yourself, or are you just making chatter based upon what you've read or heard?
I believe we do live in a era where fools make up word usage, you are a case in point, regarding perpendicular planes, I think you mean "slope". But as you must come on the "Hide" in order to understand English, allow me to help. Intransitive verb, SLOP: To pass beyond or exceed a boundary or limit. Of course this is what was being discussed, the boundary or limit to out of square, or out of true as it pertained to a bolt face and that effect on accuracy. Could you supply a reference to where the word 'slop' is used to describe two planes deviating from perpendicular? Or based on the time of the month, are you just irritable? It is fairly obvious to any reader of the entire string, you've just decided to post slop (as in food for pigs) in order be a horses ass, and add nothing. You state, " Never used a PTG bolt in a Savage so you can't comment about those", however; you do in fact comment about the PTG bolt and Savage rifles by way of inference in post #64, again may I suggest you take a Midol and give it a rest for a few days?
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Even in fire-formed and neck sized brass there is still several thousandths clearance entirely around the cartridge. The brass expands to chamber dimensions when fired due to heat but when it cools it contracts as that is the only way it can be extracted
^^Right on! Not only is it the only way it could be easily extracted, but without the necessary clearance I don't think it would chamber very easily to start with. I believe if the chamber is out of round, or the bolt face is out of square, the "flow" of the brass when fired will show up, not just on the target, but in the brass itself, what's been your experience? I've found a well cut chamber delivers longer brass life, the barrel itself does not determine the brass life, or shape of the brass after firing, but rather the chamber and bolt face. Thanks for the insightful comment!
Damn, PP2.
Sounds like you need to quit jacking off the press and get some puss. Since you are so versed on the content of this thread and the English language, maybe you should consider brushing up on your comprehension skills.
Purely speculation on my part but I believe Mr. Bryant is referring to the "slop" in the action which results in the bolt face issue.
As far as fire formed cases and alignment, I have some LC's that would beg to differ. Loaded them a little hot and wouldn't want to use them under timed fire or a firefight.
I won't argue with .001" "slop" on normal FF cases but more raises a flag.
You might want to rethink this. I guarantee you mine are .0005" or less. Closing the bolt is perfection. Like a tight patch on a Tipton rod.
Thanks for the challenge Kills.
I agree there are a lot of bs statements here. I've never been too much on BC. I tell folks like you that it doesn't matter what the bc is if you don't hit your target. Some day I may reread the article.
Consider there may be a gap between his wording and your understanding of what he's saying about the bullet tilt. The fact is the phenomenon exists.
.003" off on a chamber would exhibit a solid pilot (undersise) reamer pushing away from the hard land.
How do you align your projectiles with the bore axis? Muzzle loader, fire formed cases or the FGMM crap shoot?
I agree there are a lot of bs statements here. I've never been too much on BC. I tell folks like you that it doesn't matter what the bc is if you don't hit your target. Some day I may reread the article.
Consider there may be a gap between his wording and your understanding of what he's saying about the bullet tilt. The fact is the phenomenon exists.
.003" off on a chamber would exhibit a solid pilot (undersise) reamer pushing away from the hard land.
How do you align your projectiles with the bore axis? Muzzle loader, fire formed cases or the FGMM crap shoot?
Might need to cerrosafe your chamber and measure the casting then bump the shoulders back on your brass before you gall the lugs
Cerrosafe Chamber Casting Alloy 1/2 lb
By all means get some cerrosafe and post the results of your chamber cast and the dimensions of your fired brass then come back and call me a tard until then your words have no meaning
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Due to heat or due to pressure? Does the brass expand to seal the chamber and then relax once the pressure is gone?
And due to the tapered shape of the chamber/cartridge, I don't think one needs .006"+ of diameter difference between the brass and chamber. The brass needs to travel very little distance before it is completely free of the chamber. sure, you don't want it the exact size or larger than the chamber when in battery.
And my opinion is this, if someone is claiming there is an improvement in accuracy by squaring the bolt face, the burden of proof is on them, not the people that are skeptical.
I have cerrosafe. I don't see the need to use it though. I have hundreds of brass chamber castings. Galling the lugs only becomes an issue if you loan a rig to an amateur. Grease is a wonderful thing.
There is no guarantee that any amount of clearance exists after firing. The brass expands both elastically and plastically; the chamber (hopefully!) expands slightly and (really hopefully!) in a purely elastic manner, and then you've got whatever influence heat happens to play (although keep in mind that the brass normally comes out much hotter than it went in, which does not help).
The hardness of the brass has a large influence on how much of expansion is elastic, and how much is plastic. If you have "soft" brass, you could get a lot of plastic deformation, and if you put that into a relatively non-rigid chamber, then there is no guarantee that the brass will shrink back to a dimension smaller than the chamber - just look at all the posts around here concerning "sticky extraction" (noting that this isn't just an issue with overly-hot handloads, as there is a least one combination of factory rifle and factory .338LM ammo that does not play well together).
Can someone remind me how does this relates to bolt face perpendicularity and its effect on accuracy?
