Free-bore diameter

[AlanF]

Just wondering if anyone else has encountered this problem. I am trying Hornady ELD Match projectiles and believe they are too fat for the free-bore section of my 7mm Shehane chamber. They will slide home to the lands but only with a decent push, and when extracted, the part of the bearing surface that's been in the free-bore has much of the WS2 coating scraped off. My reamer diagram shows 0.2844" diameter in the free-bore. The ELDs are a secant ogive and with my limited measuring resources (dial gauge caliper) they are about 0.0003" fatter than Berger VLDs. Would be interesting to hear what the free-bore diameter is with other 7mm reamers?

[johnk]

.0005" is the standard precision freebore diameter from what I've experienced, but I've dealt with the same gun plumber most of the time.

[Matt P]

.0005" is the standard precision freebore diameter from what I've experienced, but I've dealt with the same gun plumber most of the time.

Agree that's the norm.
I think I have a 0.2848 throater with a 2.5 degree lead angle if you want to open it up.
Matt P

[Wal86]

Alan

I would be very surprised if the diametre of your eldm projectiles were greater than .28440". If so id like to know the batch number pls..
I just measured a few in a packet here that measured .28410 to .28420.

Is it possible that the reamer you have chambered that barrel with has seen a few barrels and worn slightly? Just a thought

Cheers

Alan

[pjifl]

PTG sell two very slightly different diameter throaters for 284.
I could never figure out why.

Then I found this statement which may be relevant. Where I found it who knows ???.
It is from a fragment of an old eMail that I sent to someone a few years ago.
I could never verify it but interesting.

======================================================
In bolt action rifles the .280 Remington is not popular in Europe, where it
competes with the 7×64mm, to which it is almost ballistically identical. But
does have a larger than expected number of European users in imported
self-loading rifles such as those by Remington. When compared to the .280
Remington the 7x64mm has a slightly higher maximum allowed chamber pressure
and as a European 7 mm cartridge has a slightly larger bore. European 7 mm
cartridges all have 7.24 mm (0.285 in) grooves Ø diameter. American 7 mm
cartridges have 7.21 mm (0.284 in) grooves Ø.
into the SSR’s.
=====================================================

Peter Smith.

[Brad Y]

My reamer diagram says .2845 and having no problem shooting 162eld bullets. Haven't measured my bullets though as I only have verniers here. 10 thou jam and first firing in hydroformed cases 52gr 2209 they hold great elevation.

[AlanF]

Thanks for the responses.

I've done more bearing surface diameter measurements of different projectiles, various batches, using a Lyman dial caliper which I can estimate to 0.0001". By doing multiple measurements, I'm confident the averages are +/- 0.0001". Not sure about the absolute values so will express all measurements in relation to the smallest diameter bullet, the SMK 183.

SMK 183 0.0000"

ELD 162 0.0006"
VLD 168 0.0002" (sealing ring 0.0004")
VLD 180 0.0003" (sealing ring 0.0007")
Hyb 180 0.0004" (sealing ring 0.0007")
EOL 195 0.0002" (sealing ring 0.0005")

ELD Lot #2161114

Only the Bergers seem to have "sealing rings" (larger diameter at the bearing surface / boat-tail junction). But of course this doesn't go into the throat during initial chambering.

Matt,

I may drop in a Krieger that is due for re-chamber, and ask you to open the throat to 0.2848".

[Wal86]

Alan

I ran a .00000" mititoyo micrometre over some 183gr SMK. Which measured up @ .28365" to .28375" largest i could find in that particular pack was .28380" but they were very few and far between..
Dont know if this helps
Cheers for Lot#

Alan

[AlanF]

...I ran a .00000" mititoyo micrometre over some 183gr SMK. Which measured up @ .28365" to .28375" largest i could find in that particular pack was .28380" but they were very few and far between...

Thanks Alan. So that would make the ELDs .2843" if my measurements are taken as correct. My reamer has only done 7 chambers, so I'd hope it hasn't worn. My impression is that there can be variations in chamber diameters using the same reamer - there must be times when the floating pilot isn't a perfect fit in the lands etc. So I won't complain about a small throat diameter, it indicates a very true chambering job .