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Can anybody tell me how crush fit chambering works. I was told it was more accurate. Does anybody have any experiences with crush fit chambering in .223 Remington caliber? Regards, Bob. | ||
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One of Us |
"Crush fit" means -0 headspace. It is used to hold a "parent" cartridge case firmly in an improved chamber during fireforming. Once that round is fire formed to that chamber there is no longer a "crush" factor. With a standard cartidge case, you can get the same effect by firing your standard brass and then neck sizing, holding short of the shoulder. Fire formed and neck sized ammo has less tendency to shift when fired, providing a better opportunity for the bullet to stay aligned with the bore. That helps accuracy. _______________________________________________________________________________ This is my rifle, there are many like it but this one is mine. My rifle is my best friend, it is my life. | |||
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Yep For a target or varmint rifle I neck size and bump the shoulder back when it gets to tight for easy cahmbering. As usual just my $.02 Paul K | |||
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Funny, this is another one of those terms that seems to have taken on diiferent meanings over the years. That or I just plain got it wrong from the git-go.  I always took it to mean that when you cinched up the barrel the shank compresses a little. So, I chamber such that the go gage is .002" too deep and when the barrel is tightened and the shank compresses the gage will read zero as Malm said. Chambering in this way gives the zero headspace he mentions. But, the way the term was splained to be had nothing to do with the "crush" on the case, it was alledgedly the crush of the barrel against the torque shoulder. Lately when I hear this term being used people are taking it quite litterally and torquing the hell out of the barrels. This I think is taking the concept too far.  Aut vincere aut mori | |||
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Humm, so what would you call my Mauser that's set to -.001 on the headspace (bolt stops short of closing on a NO-GO gauge? | |||
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Within specs? Aut vincere aut mori | |||
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It had better not close on a NOGO gage. Did you mean that it doesn't close on a Go gage, that would be tighter heaspace than spec. Rusty's Action Works Montross VA. Action work for Cowboy Shooters & Manufacturer of Stylized Rigby rifle sights. http://i61.photobucket.com/alb.../th_isofrontleft.jpg | |||
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The accepted "crush" headspace for improved chambers is -.004, allowing for different headstamps to chamber with the little bit of crush. The reason for it is mainly safety, so that the headspace isn't excessive the first time you pull the trigger on a new piece of brass. As was pointed out earlier, after the initial firing, their in no more crush fit. A straight 223 doesn't need a crush fit and may even cause FL sizing issues for the brass. | |||
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One small problem with all this "CRUSH FIT" stuff has to do with the sizing die....If the die doesn't fit the chamber the rest is squat doodly. I don't use a standard headspace gauge to set my barrels and chambers, I use a case sized with the sizing die AND the marked, standard shell holder I will be using...both kept together is the die box so they won't get mixed up with all the other shell holders I have collected over the years. I set my reloading press tight with the sizing die screwed down tight against against the shell holder so all the play is taken out of the press linkage. I take the sizer button out of the die and turn the case around a quarter turn as is size at least 6 times so I know most of the brass spring has been reduced to a minimum, then usually use a Wilson case holder or make one, to hold the case while I check the base with a dial indicator. I pick the case with the least run-out as the heaspace gauge. I also do the "blueprint thing" with the bolt face, and any shoulders on the barrel or receiver. I use 0.002" for brass spring spec, and 0.004"-0.006" for bolt nose to barrel clearance. When I do everything right I can hand screw the barrel and receiver together and snap the last half turn together and end up with zero "crush", the brass headspace gauge just touching the bolt and chamber shoulder...Not always easy to do. When everything is right I have to use a barrel wrench to remove the barrel from the receiver done this way. By the time I've finished working up a good load, the barrel and receiver have locked together so tight it is very difficult to get them apart when the barrel is used up. This means the chamber and the sizing die are as close as possible to a "custom fit" but still use readily available and much cheaper standard dies, shell holders and brass. Depending on what the rifle will be used for and the expected case life and the expected barrel life, I buy enough brass to last the cycle. So far this has worked extremely well for me. Brass, in tests, has lasted far beyond my normal "5 reloads-then-toss" for anything 30 cal and above. Varmint cal brass get used until the case it totally used up. I also use custom adjusted shell holders...i.e., either Redding Custom shell holders or shell holders I've ground a few thousands off the surface to either allow the case to be "fitted snug" against the chamber shoulder or to give a few thousandths clearance, depending on what the application is...hunting varmints, edible or dangerous game or targets. Another problem is factory chambers run the gamet between SAMMI minimun to over SAMMI maximum and even custom chambers are subject to maximum ecomony as far as the reamers are concerned. Many 'smiths start with a maximum sized reamer so they can resharpen it as needed until the reamer is SAMMI minimun or under...at least in the "old days". Not saying there anything is wrong with this proceedure...'smiths have to eat too...it just introduces variation and the concept of "CRUSH FIT" becomes nothing more than something to wave about...like name dropping at a party. The difference in the way I do a chamber or build a rifle and a 'smith does it, is I do it for myself only...I don't have to contend with being sure a custom rifle can be used with off the shelf ammo. I won't ever go overseas to hunt and even with my way of chambering the use of standard dies allows the use of factory ammo most of the time, although that old argument is just than...OLD...I've never lost any ammo because I plan for contingencies, making sure there is ammo with the rifle, in my coat pockets, my pants pockets and several places in my truck, etc. My problem is remembering where I've ratholed it all...after the hunt. It is always interesting to me to read the thoughts and experiences of others in this sport and I guarantee I learn a lesson a minute and it opens up another avenue of thought, every time I read something relatively "new" in a post. I add my small contribution even though I get ragged on many times. I've never claimed to be a gunsmith, just highly motivated and interested in this sport and as most of us, have my own way of doing and looking at things related to shooting and reloading. 'Njoy | |||
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I don't claim to be a gunsmith either and I'm not gonna argue with the method you use for chambering. I will say this however, I do use a steel Go Gage for most chambers for one reason, I want all the chambers I cut with a specific reamer to be the same lengh...and they are. I use an unfired case from the parent round for doing an improved chamber though. Then set the headspace for the previously mentioned .004" crush. The dies for these cases should be set up so that this is taken into account anyway. The one Ackley Improved headspace gage I have is just a 6mmRem gage shortened by .004". As I stated in my first post, there can be sizing issues if a crush headspace is used on a standard chamber. | |||
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Hey Bob,I'm able to get a "Crush Fit" on all my Bottleneck Cases by using Partial-Full Length Resizing(P-FLR). I do not have a Custom Barrel or Chamber at the moment and have no problem at all creating the Crush Fit(Zero Headspace) condition. The above Link will tell you how to do it by adjusting your Reloading Dies. And the other folks explained about setting the Go No-Go Gauges up. Best of luck to you. | |||
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Partial-Full Length Resizing. Sounds like "a little bit pregnant" | |||
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Opps, sorry guys, I ment that it won't close fully on a GO gauge. With a factory round in the chamber, you can just feel it just touch the shoulder of the case in the last few deg of rotation. Rusty, That's what I ment by -.001 on the headspace setting. As this rifle is so far averaging 1/2 MOA (not bad for a 30cal hunting stick) I don't feel like changing anything. | |||
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Pointblank...As I said, I do my chambering for myself only and not for economic reasons...nothing inherently right or wrong with using a standard steel headspace gauge vs using a piece of sized brass. You can mess up using steel also if you get ham fisted. Determining the drag of the bolt closing on a steel headspace gauge as to whether it is a rough bolt face, rough recoil lug and which one or even if the lugs are abutting equally even if polished or just drag on the bolt length generaly is like trying to determine the future by scratching around in the entrails of a goat or reading the fall of a handfull of "special bones".    Since I started using Redding Competition shell holders over homebuilt and shimmed shell holders and understood the whys of modifying a standard shell holder and started using cases sized in the sizing die (be it wildcat or standard dies) that would be used for the future sizing operation, the precision of my ammo and the accuracy of those systems, has risen considerably. I can always adjust in or out any variation in chamber vs sizing die dimensions to a small range. Once set and there isn't any change in dies or shell holders, the range is locked in...barring any wear in the components. I've never had any problems in the sizing operation...everything fits a priori, before the fact, not after the fact. I fit the chamber to the sized case, not the other way around. It works for me for individual chambers but if I were doing it for a living I would have to know that the individual using the rifle would understand the total ramifications of reloading for that specific rifle or I wouldn't do it at all that way...just the "normal, within SAMMI specs" way...one of the reasons I don't claim to be a gunsmith or gunsmith professionaly...it is very difficult to teach an old dog new tricks, so to speak. I also ran some test years back on partial FL and neck sizing only and again once the Redding Bushing style dies came out, using .223 and .308 caliber cases. I found that using a Redding bushing FL sizing die that closely fit the chamber kept runout to the very minimm, usually in the 0.000" to 0.001" range, while using the Redding bushing NK sizing die resulted in more total runout, up to 0.003" and partial resizing with either FK or NK standard dies, RCBS, Lyman, Hornady, and Forster mostly, resulted in the most runout, up to 0.006" and brand didn't play into the equation...they all had a certain range of runout to a greater or lesser degree. Taking a resized case with a large runout and running it back through a Redding Bushinhg FL die adjusted to have all the backlash taken out of the ram links, then the die turned down at least another full turn and a half, "locked" in other words, would...in most cases...size the case back and remove most of the runout. Just using a "locked" ram would do the same for other cartridges that I had been "partially" resizing, 338-06 and 375 H&H which I had been partially resizing for years. It also increase the accuracy of those cartridges for bullets that were'nt doing as well as I had wanted. FL resizing with a "locked" ram isn't something that is usually done and relatively unknown to many reloaders I've talked to...and isn't something many who do know chose to do. Many don't fully understand the hows, whys and whatfors of reloading, what can be done to increase accuracy in a rifle systemm, i.e., all the individual components including the ammo, nor even care to expend the energy required to achieve that level of accuracy...if it goes boom and hits a pie plate at 100 yds...it's goodnuff. This is NOT a denigration of anyones methods, just acceptance of each persons needs and requirements. We all do what we do best for our own reasons. I'm not trying to change any minds or push my agenda here or in any of my other posts...just postulate other information and methods for those who might find the information useful. My results could be different than yours and may be a result of my equipment and methods. Lots of variation in this sport. 'Njoy | |||
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WOW.... I really don't think their was much thought put into choosing his ID/HANDLE name, so he just used one he had EARNED, Foobar. Extreme Custom Gunsmithing LLC, ecg@wheatstate.com | |||
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Thanks for all the information. I appreciate it. Regards, Bob. | |||
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