Shims...barrel vs bolt
- Thread starter Davehc130
- Start date
well since bolt shims will decrease head space and barrel shims will increase headspace I was wondering pros and cons of each. Going to try bolt shims on my 457MTR to run Eley. Used lilja barrel shims on another 457. Just wondered what people might think about using them both.
Well, since you never initially stated which gun it was, a shim at the barrel doesn't mean it can only increase headspace. If the gun came with a shim from factory, changing it for a thicker or thinner shim would directly increase or decrease headspace. No one can read your mind as to which gun is going to be shimmed. Alas, you have stated it's a CZ 457, so that helps.
Depending on the shims quality and tolerances, you could introduce greater error messing with the barrel compared to the bolt. At least with the bolt you won't affect alignment of the barrel to the receiver.
Depending on the shims quality and tolerances, you could introduce greater error messing with the barrel compared to the bolt. At least with the bolt you won't affect alignment of the barrel to the receiver.
6 of one half dozen of the other. If you're talking CZs and it fires Lapua but you have FTF with Eley then the barrel tenon was machined too short and Barrel shims will only make the problem worse. I believe CZs are slip fit so increasing tenon length is a easy fix . .043 headspacing will generally fire both Eley and Lapua. I would first check this to see what headspacing is. CZs reciever specks leave something to be desired. At one time Lilja cut their drop in CZ barrel tenon short and included shims to set headspacing simply because CZ tolerances were not held to the same standards as say Anschutz or Vudoo and others.
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Headspace in a rimfire???????? Isn't there some kind of tolerances for case length in RF or are the ammo companies making 22 long rifle cases different lengths? And rifle makers making the chambers different lengths?
There are "match chambers", I understand they are just a little tighter and, I presume, better machined to be symmetric with the bore. What are the dimensions for the chambers and bore of a 22 rf? I've been wandering around for 80 years thinking they were pretty much standard. The biggest change would be tool wear.
"too soon old, too late smart"
There are "match chambers", I understand they are just a little tighter and, I presume, better machined to be symmetric with the bore. What are the dimensions for the chambers and bore of a 22 rf? I've been wandering around for 80 years thinking they were pretty much standard. The biggest change would be tool wear.
"too soon old, too late smart"
22 remfire headspaces on the rim not the case. Eley rim thickness is a bit thinner than Lapua and many other ammo brands. It's not uncommon to have a gun fire Lapua with 100% reliability but get light strikes and FTF with Eley.
OK, that leaves me with 2 questions, 1. What is a match chamber? 2. Why doesn't the market force a standard rim thickness? Accuracy and 22rf ammo is a crap shoot to begin with and then when you add a major manufacture using a different case dimension. Thank you for the information, Eley is off my test list, but now I understand why guys are measuring the rim thickness.
The rabbit hole gets deeper!
The rabbit hole gets deeper!
Eley shouldn't be off your test list... It sounds like you're misunderstanding the previous comment on Lapua vs. Eley rim thickness. Eley and Lapua rimfire ammunition both win top international competitions.
Accuracy and Rimfire isn't a crap shoot either... good match grade rimfire ammo will generally shoot very well in most well made rimfire rifles. There are standard dimensions for cartridges and chambers, but there can also be minute differences between what CIP specifies and SAAMI specifies. Additionally, manufacturing methods, and tolerances will play a part in "Eley having a slightly less thick rim than Lapua." One doesn't make the other worse, it's just a minute difference due to a myriad of variables.
Match chambers in rimfire bolt rifles generally have a shorter distance from the headspace datum (where the rim seats against the mouth of the chamber) and where the throat/leade of the rifling commences. Match chambers allow the projectile to be lightly (or heavily depending on how tight it is) engraved by the rifling -- this can increase accuracy.
Most off the shelf rimfire rifles, especially semi-autos and general plinking guns will have a standard SAAMI chamber (or CIP if coming from a European manufacturer). There are plenty of other .22lr chambers out there, but generally a Match chamber in a bolt action rimfire will allow for some level of rifling engraving when the round is chambered and the action is locked in battery.
Measuring rim thickness is typically not worth while from a sorting perspective... the almost insignificant difference in that will not greatly affect the ability of a given gun to group well - not to mention the shooters capabilities, external variables, ammunition variables within the manufacturing Lot etc. all playing a much greater role.
Lots of more serious shooters will, if possible, set the headspace to the given rimfire ammunition they're using, which does mean measuring the rim thickness, or using headspace gauges to set the headspace closed to their ammunition, as having it be as tight as possible while still within specification (remember the headspace dimension is a plus/minus dimension) can improve ignition of the cartridge, and thus increase the consistency of powder burn and so on.... I won't get into too much more detail because quite frankly it very quickly turns into a huge lesson Internal Ballistics.
The original post was asking as to whether one method of increasing or decreasing headspace would be better than the other - arguably that remains to be seen, but my initial suggestion of changing it on the bolt was to avoid introducing as little error as possible between the barrel and the receiver interface, as that could theoretically create other problem areas (again, theoretically, it's an entirely valid method).
I hope the above information helps you better understand, at a very high level your two questions and also why you should not discount Eley. I have managed to shoot MOA groups @ 50 yards with Eley Sport (in a Bergara B14R) which is not their best match ammunition by a long shot -- proper accuracy testing of Eley, Lapua, SK etc. will show you which ammunition shoots the best for you.
B"N"F, thank you very much for the explanation. Never got into 22rf accuracy till lately. As a plinker, I just thought that there were SAAMI standards for case dimension for Caps, shorts, longs and long rifle. Never thought the manufactures would have their own. Does the rim thickness cause a change in accuracy or just ignition? I have been using CCI SF and sort by weight. I am using a TC Contender with a custom 20 inch barrel and trigger work and getting close to MOA out to 50 yards, then the wind gets me. Here in WNY it is nearly impossible to find match type 22rf ammo. The serious competitors are buying 5K lots and I've been begging a box or 2 to try.
Thank you again.
Bill
Thank you again.
Bill
g'day all,
I bought so called 'trigger-shims' which I installed in the bolt of my Lithgow 101 and the groups were that little bit tighter. an excellent buy IMO.
I got them from Lance Shivelly. They come colour coded so even a clod like me can fit them ok.
I bought so called 'trigger-shims' which I installed in the bolt of my Lithgow 101 and the groups were that little bit tighter. an excellent buy IMO.
I got them from Lance Shivelly. They come colour coded so even a clod like me can fit them ok.
I thought it was completely absurd to headspace a .22 until I started shooting competition. Until I shimmed the bolt just under moa was as good as I thought I could get. Now that I have taken the time and spent the money to have the gun ammo tested, I have amazed myself at the difference in the accuracy of me and my gun. I have a CZ 457 with a IBI 22" barrel set in KRG Bravo chassis. At 55 meters I shoot .250 or better very consistent. If the the wind is blowing not so much but still sub moa. Match grade ammo is not always what your gun is going to like. I have a buddy with a Vudoo that shoots sub moa using CCI standard. Rimfires are funny that way. They like what they like. Before someone ask, Lapua ammo tested it and SK long range and Lapua pistol king both shot about the same with the SK coming out on top.
