.17 HMR round not fitting real snug in a Lilja barrel

[M116]

I just received my Lilja .17 HMR bull barrel the other day and noted the Hornady V-max round wiggles a bit in the chamber which doesn't seem right. The cartridge OD is .238" and the chamber measures .244 which is giving me .006 slop. A seated bullet just falls out of the barrel. Is that suppose to happen? The documentation that came with the barrel stated that a misfired round can easily be extracted but this seems a bit excessive. Being a match barrel you would think they would want to keep the brass well seated in the chamber. What gives?

 

[djdilliodon]

That's pretty much as tight of a chamber you want on the hmr. If you go tighter ruptured cases will happen.

 

[justin amateur]

I asked the same question a while back.

I was wondering why the chamber on the new Lilja 17 hmr was not as tight a fit
as the chamber on the Lilja 22lr, found a notification on the Lilja site regarding
the match chambers as cut...

http://www.riflebarrels.com/products/chamber_info.htm

The 17 hmr chamber is not cut to allow the bullet to engage the rifling.
The Lilja chamber diameter appears to be 0.245"...explains the wiggle I felt
when a round is dropped into the upended barrel, as a 17 hmr brass is 0.238".
The CZ 17 hmr chamber measured 0.247"...two thousandths larger.

Was given an answer by "The Canuck"

First of all the 17 HMR round is headspaced from the neck on the casing (like most CF) as opposed to the rim base on 22LR. Clearance on the rim thickness must also be done to the + side. They are quite liberal on this compared to heavy hitting CF rounds because they want to stay on the + side of manufacturing tolerances and the shooter(like in 22LR) does not have the option to size down the brass to conform more closely.

Secondly, the rim base to bullet ogive length varies a bit on commercial .17HMR ammo. In this respect again, Lilja is forced to stay on the + size of maximum length since the shooter does not have the option with hand loading the round seating depth themselves. A little bit of bullet jump will be enevitable because of this since the alternative is a dangerous spike in pressures if a round engraves heavily. Copper is springy compared to lead, it will position itself a bit better on a jump and will handle bore irregularities a bit better also. You cannot engrave a copper clad round like you can a lead one without spiking the pressure incredibly.

 

[M116]

That's pretty much as tight of a chamber you want on the hmr. If you go tighter ruptured cases will happen.

I would think the case would be less apt to rupture if it had a tighter fit in the chamber and not allowed to expand but I don't have a lot of experience at this level and am trying to figure this out. A friend of mine stated the reason for a loose chamber was from the possibility of the round "hanging up" in too tight a chamber where the resistance could set-off the round from the bolt getting slammed into the chamber. Not sure it that's valid but it seems plausible. What prompted me to pose this question was a photo of a Lilja barrel upended with a .17 round sitting face down on the chamber where the cartridge would need to be pushed into the chamber to seat the round. If I recall correctly the owner stated the light press fit was how it should fit in the barrel. When you consider the lengths the owners of rifles go thru to nail everything down to minimize movement having the bullet wiggling inside the chamber seems counterintuitive.

Do all .17 HMR rounds have a loose fit in the chamber? That answer would clear a lot of things up for me.

gras

 

[djdilliodon]

You probably saw a pic of a 22 LR lilja with the round not all the way in the chamber. The reason for not going tighter on the hmr is due to case ruptures. If a slam fire was a problem from going too tight, see how tight it is to push a 22 LR round into an eps match chamber! Never had one go off yet .

 

[M116]

I asked the same question a while back.


Was given an answer by "The Canuck"

First of all the 17 HMR round is headspaced from the neck on the casing (like most CF) as opposed to the rim base on 22LR. Clearance on the rim thickness must also be done to the + side. They are quite liberal on this compared to heavy hitting CF rounds because they want to stay on the + side of manufacturing tolerances and the shooter(like in 22LR) does not have the option to size down the brass to conform more closely.

Secondly, the rim base to bullet ogive length varies a bit on commercial .17HMR ammo. In this respect again, Lilja is forced to stay on the + size of maximum length since the shooter does not have the option with hand loading the round seating depth themselves. A little bit of bullet jump will be enevitable because of this since the alternative is a dangerous spike in pressures if a round engraves heavily. Copper is springy compared to lead, it will position itself a bit better on a jump and will handle bore irregularities a bit better also. You cannot engrave a copper clad round like you can a lead one without spiking the pressure incredibly.

If I'm reading this right what he's basically saying is they open up the chamber to allow for sloppy tolerances. The rim of the cartridge seats flush with the end of the barrel so any tolerance associated with rim thickness takes place on the bolt side not the barrel. Not sure what he was referring to the regarding engraving the copper in the bore but I guess it's another topic since as I am only asking about the case fit in the chamber.

 

[M116]

You probably saw a pic of a 22 LR lilja with the round not all the way in the chamber. The reason for not going tighter on the hmr is due to case ruptures. If a slam fire was a problem from going too tight, see how tight it is to push a 22 LR round into an eps match chamber! Never had one go off yet .

The picture show the bullet resting in the barrel right at the neck of the case under gravity. My bullet just falls into the hole. I looked for the photo to link it but didn't find it (it may be on another forum, I'll looked but haven't found it yet).

Why does a match grade 22 fit so snuggly yet a match grade .17 doesn't? ..................interesting!

That's kinda what I'm getting at. I think my Marlin 995 .22 has a better fit.

 

[justin amateur]

Might have been these images

CZ factory 22lr barrel showing how a round drops in.
Chamber is cut so the bullet doesn't reach the rifling.
Sloppy fit to allow for easy feeding and extraction
even when the action is fouled with gsr.

The Lilja 22lr chamber showing that when a round is pushed in
the bullet engages the rifling the last bit, ensuring that the round
seats firmly in the brass and aligned with the bore as best it can be.

The Canuck explained that due to the production variances in 17 hmr ammo
the chamber has to be cut slightly looser to fit those variances and the
round not engage the rifling so as to prevent overpressure in the chamber.

 

[M116]

Might have been these images

CZ factory 22lr barrel showing how a round drops in.
Chamber is cut so the bullet doesn't reach the rifling.
Sloppy fit to allow for easy feeding and extraction
even when the action is fouled with gsr.

The Lilja 22lr chamber showing that when a round is pushed in
the bullet engages the rifling the last bit, ensuring that the round
seats firmly in the brass and aligned with the bore as best it can be.

I with mine did that. This thing is not sealing the bullet anywhere and will likely outgas in the chamber.

This is kinda what I was expected from the Lilja barrel. I wonder if perhaps I got a bad barrel this doesn't seem right having it so loose

. Who knows how much of a gap I have between the bullet and the barrel and the neck of the round on this barrel. If something is out of kilt I would want the barrel exchanged. Spending $400 on a match barrel with a chamber with slop is counterproductive.

 

[justin amateur]

The important part that you need to comprehend, is that a 22lr (as shown)
can be engraved safely, and provide better accuracy due to the engraving.
The 17 hmr can not be engraved due to overpressure concerns.
This has to do with the round seating depth in the case of the factory loads.
The 17 hmr has to drop in and fit flush to the face of the breach.
Your 17 hmr Lilja barrel is exactly like mine. Take it to the range
and compare the results against your CZ factory barrel. The results
at the target will show you why you paid more for the Lilja.

That 400 dollar expense is mostly due to hand lapping the bore.
It saves you a brick of 17 hmr needed for barrel break in
as Lilja has already taken care of the bore polishing for you.

Definitely made a difference in my targets. Worth the expense
as now I can tell it's me when I miss and can't blame it on the rifle.

btw M116, if you look, you'll find I included the chamber dimensions
of my Lilja and CZ hmr barrels with my initial response to your query.
My Lilja 17 hmr has the same dimensions as yours.

One other thing to be aware of, there is no such thing as a match chamber
for 17 hmr. The reason being: no one manufactures match grade 17 hmr ammo.
Do a search on line and check for yourself.

 

[M116]

The important part that you need to comprehend, is that a 22lr (as shown)
can be engraved safely, and provide better accuracy due to the engraving.
The 17 hmr can not be engraved due to overpressure concerns.
This has to do with the round seating depth in the case of the factory loads.
The 17 hmr has to drop in and fit flush to the face of the breach.
Your 17 hmr Lilja barrel is exactly like mine. Take it to the range
and compare the results against your CZ factory barrel. The results
at the target will show you why you paid more for the Lilja.

That 400 dollar expense is mostly due to hand lapping the bore.
It saves you a brick of 17 hmr needed for barrel break in
as Lilja has already taken care of the bore polishing for you.

Definitely made a difference in my targets. Worth the expense
as now I can tell it's me when I miss and can't blame it on the rifle.

btw M116, if you look, you'll find I included the chamber dimensions
of my Lilja and CZ hmr barrels with my initial response to your query.
My Lilja 17 hmr has the same dimensions as yours.

One other thing to be aware of, there is no such thing as a match chamber
for 17 hmr. The reason being: no one manufactures match grade 17 hmr ammo.
Do a search on line and check for yourself.

Justin

I have no doubt regarding the precision of the Lilja barrel. Having the round fit so loose just doesn't seem right but I understand there is usually more to the story then what it appears to be. But as you stated as I outlined (in red) about Lilja having the "bullet engage the rifling at the last moment" as shown in your photo where it appears that is not the case with my barrel (none that I can tell at least).

This is a good topic to discuss. I would image next to the actual rifle bore itself the chamber design is probably the next most important aspect of the gun.

 

[justin amateur]

But as you stated as I outlined (in red) about Lilja having the "bullet engage the rifling at the last moment"

M116....only the 22lr engages the rifling.

Nowhere will you find a picture of the 17 hmr engaging the rifling.

It does not exist. Why? It would be unsafe due to overpressure when fired.

As to the loose fit of the round in the chamber
If you do not have match grade ammunition,
there can be no match cut chamber.

So, the only chamber that can be cut is one to fit the existing ammo supply.

Ergo: There is no further discussion to be had.

Now, if you can find a supplier of match grade 17 hmr ammunition,
then you have reason to complain about the tolerances your Lilja is machined to.
Until then, the chamber as cut is the only one that will fit the ammo supply.

If you don't believe me, wait until you run into some factory second Winchester 17 hmr ammo.
Then you'll understand why Lilja had to machine the chamber as they did.

 

[djdilliodon]

As justin has already stated going with to tight or short of a chamber in the hmr will result in ruptured cases or worse from over pressure. The smallest you can go I believe is .004" smaller than a factory chamber which is what I believe lilja has done. Justin, I don't have a factory barrel on hand right now (just Lilja's). Can you measure the factory chamber and measure the lilja to see if my number above is correct?

 

[justin amateur]

From my initial response:

The 17 hmr chamber is not cut to allow the bullet to engage the rifling.
The Lilja chamber diameter appears to be 0.245"...explains the wiggle I felt
when a round is dropped into the upended barrel, as a 17 hmr brass is 0.238".
The CZ 17 hmr chamber measured 0.247"...two thousandths larger.


I used a cheap plastic caliper to measure with.
That's why I said "It appears".

 

[Redmanss]

.17 HMR uses jacketed rounds, has ~25k PSI chamber pressures and have the same characteristics as a centerfire. You cannot compare it to .22LR with low chamber pressures and bare lubricated or copper washed projectiles. It's like comparing a minie ball with a SMK.