Gunsmithing 308win Match Reamer?

NorCal Vu

NorCal Vu

Gunny Sergeant
Full Member
Minuteman
Dec 20, 2004
1,154
164
Sacramento Area
#1
Guys,

What reamers would you want to use for a match spec chamber for 308win?

Is there one with the lead already set for 168s and 175 match ammo?

Is there an industry standard reamer that outfits like GAP, KMW, R&D would use for their 308 builds? Or does each outfit have their own flavor on reamers?

Thanks,

Vu
 
#5
Re: 308win Match Reamer?

The '95 Palma reamer has a straight section length of .050" at a diameter of .3083". This is too short for 175 GMM factory ammo from our local testing results, though fine for handloads or if one wants to seat the GMM bullets a tad bit further into the case.

Vu, if 175 GMM is not on your list of must-shoot ammo, then the '95 Palma reamer is fine. Otherwise, go with some other "match" dimension reamer with a tad longer straight section.

The critical "match" dimensions are the straight section length, straight section diameter, and leade angle. Length needs to be somewhere between .050" and .100", diameter at .3083" or so, and leade angle at 1 degree 30 min. Body dimensions are not all that critical. For a "match" rifle have the smithy cut the headspace between GO and .002" over GO maximum.

If the smith won't show you when asked the reamer blueprint or if shown does not know how to read it, then find another gunsmith. I know some of the big smiths that are on this site like to hold their dimensions in confidence, so if you want to use them then the "trust me" approach will have to be accepted. Your call on what you do about that one.
 
#7
Re: 308win Match Reamer?

Thanks guys.

Since everyone has a match chamber in their custom 308win I was wondering if there was an industry standard on this.

I have heard Terry mention a Palma 95 chamber before.
 
#10
Re: 308win Match Reamer?

a while back someone/builder on a similar Thread posted a good Reamer to use. (i think this reamer). I think (maybe You) or one of the other site sponsored builders posted it.
I know that dave kiff is a pretty good source for info on choices for reamers if you are seeking.

308jpg.jpg

.
 
#12
Re: 308win Match Reamer?

PTG start out with a Palma reamer and it's modified for the 168's and 175's. Not sure if it was a Palma 95 or not but I would bet it is or was. Dave Kiff could tell you.
 
#15
Re: 308win Match Reamer?

My latest 308 is chambered with a 308 Palma 95 reamer and it shoots FGMM 175's fine as well as several other factory loaded 175gr Match King loads. It does shoot the 168 FGMM best but everything else is still under .500" at 100yds.
100_1066.jpg

100_1067.jpg

Phoenix2.jpg
 
#16
Re: 308win Match Reamer?

The Bisley is the short one OAL 2.775. Both of mine OAL to touch the lands is 2.815 I load to 2.800 and wear the barrel out. Works with most dies where a lot of the "match" reamers will not.

Get a 95 Palma with the freebore set for a 2.800 OAL and your GTG.
 
#17
Re: 308win Match Reamer?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Two Shoes</div><div class="ubbcode-body">+1, esp if it is a 5R , 5C/P..............
You will get bad pressure issues, spikes like a bitch. </div></div>

TS,

Is this with the Palma Match chamber you are talking about?

 
#18
Re: 308win Match Reamer?

Had a 308 built at Rock Creek using a JGS live pilot 308 Obermeyer reamer I'd bought for the project. It's designed by Boots explicitly for the 175SMK, has a cylindrical leade and a 3deg included angle throat. Used with a 5R barrel, 26" finish, shallow conical crown, pillar bedded in a McM A1-3 blind mag stock and yields one ragged hole with three rounds at 100yds off the bench with 'pod and bag for what that's worth. Will put rounds right on the dot with the SH Practical Tactical target until my old eyes start to get annoyed. I think JGS will send you the print if you ask, it's #3519.
 
#19
Re: 308win Match Reamer?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: justpete</div><div class="ubbcode-body">Had a 308 built at Rock Creek using a JGS live pilot 308 Obermeyer reamer I'd bought for the project. It's designed by Boots explicitly for the 175SMK, has a cylindrical leade and a 3deg included angle throat. Used with a 5R barrel, 26" finish, shallow conical crown, pillar bedded in a McM A1-3 blind mag stock and yields one ragged hole with three rounds at 100yds off the bench with 'pod and bag for what that's worth. Will put rounds right on the dot with the SH Practical Tactical target until my old eyes start to get annoyed. I think JGS will send you the print if you ask, it's #3519. </div></div>

+1
 
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#22
Re: 308win Match Reamer?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Vu</div><div class="ubbcode-body">I sent an email to JGS for the specs mentioned above. Will post when i get more info.

Thanks,

Vu </div></div>

Careful, there's a statement on the print requiring written permission to copy or distribute. Turns out it was ok to send it to the 'smith but I doublechecked with them to be certain. The print is sufficiently complete to make a reamer from so it'd be considered proprietary I think. You'll know when you see it. Geometric Tolerancing fun and games...
 
#23
Re: 308win Match Reamer?

My latest tube is a Rock 5R 1:10 308 and the chamber is cut with a 308 Obermeyer reamer.
2.800 COAL with Nosler 168BTHP's have me .012" off the lands.
168 SMK's have their ogive about .015" more towards the base of the bullet, so with the reamer used on mine there's a .027" jump with Fed GMM 168's (2.800" +/-).
 
#24
Re: 308win Match Reamer?

Checked the 308 Obermeyer with two 175 SMKs on the LNL gage with three measurements each averaging 2.226" from casehead to the 0.3000" diameter on the ogive. Or whatever the real diameter is given the very slight chamfer on the ID of the bullet comparator insert.

Checked four loaded rounds without disturbing the LNL comparator on the calipers and got an average of 2.215" yielding a jump of 0.011", nominal. Which is about what I set up the seating die for, more or less.

The COAL of the four loaded rounds measures 2.814", 2.813", 2.813", and 2.809" for reference.
 
#25
Re: 308win Match Reamer?

Justpete,

Thanks for the heads up. I wouldnt want to do anything like that.

Could a guy launch 155gn scenars using this reamer? Or would you want to go with a different setup?

Thanks,

Vu
 
#26
Re: 308win Match Reamer?

I have a KMW with a '95 Palma chamber and found the readings (avg) to be the following to reach lands:

175 SMK:
Comparator reading: 3.202
COAL: 2.783

168 SMK:
Comparator reading: 3.215
COAL: 2.811
 
#28
Re: 308win Match Reamer?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Vu</div><div class="ubbcode-body">Justpete,

Thanks for the heads up. I wouldnt want to do anything like that.

Could a guy launch 155gn scenars using this reamer? Or would you want to go with a different setup?

Thanks,

Vu </div></div>

Honestly couldn't tell you. Depends on how deep the heel of the bullet sits I guess, I don't have any experience with the Scenars, sorry. You might be able to calculate it from the print though, it's pretty comprehensive.
 
#31
Re: 308win Match Reamer?

When Terry built my rifle couple yrs back he used the Palma 95 Match reamer. I had specifically told him I was wanting it set up to shoot FGGM in 175gr. It would shoot them like a laser, but the FGMM would engagae the riflings so much you could not eject a live round. Had to send it back to Terry and he had to throat it so it would handle the round. Funny thing is it is still way under a 1/2" rifle but it does not shoot like it did the first time. My 2 bits krw
 
#32
Re: 308win Match Reamer?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Vu</div><div class="ubbcode-body">Justpete,

Thanks for the heads up. I wouldnt want to do anything like that.

Could a guy launch 155gn scenars using this reamer? Or would you want to go with a different setup?

Thanks,

Vu </div></div>

I've requested some samples of this bullet from Lapua USA and will make the same measurements available. I should also record the 0.3000" dia ogive to base dimension and the Hornady test case OAL so we can work backwards to where the heel of the bullet resides for a given jump. I need to do that as well with the SMKs come to think of it. I don't remember if I did or where I would've scribbled it down if I had.

So I just went ahead and did it rather than dig through the data to see if I could find it:

Using the same two 175 SMKs as used in the previous measurements I get an average of 0.654" ogive-base making three measurements rotating the bullet roughly 120deg between them.

The Hornady case measures right at 2.005", exactly what I trim cases to, plus or minus a thou or two.

Using the Hornaday LNL headspace insert the Hornady reference case measures 1.621", the JGS Go-Gage measures 1.623", and the same four loaded rounds as before measure 1.621", 1.620", 1.621", and 1.622" respectively yielding an average of 1.621". The loaded rounds are made with non-fire-formed new Lapua brass, FL sized in a Forster NM 308 die, and individually gaged to min headspace on a Wilson cartridge gage.

These same four rounds have an average ogive-casehead dimension of 2.215" from the previous data so the average bullet base to casehead dimension would be 1.563" or 0.442" below the case mouth given the above trimmed case length dimension. According to the SAAMI print for the 308Win round the neck length is 0.2934" with the case trimmed to 2.005" leaving 0.1486" of the bullet heel below the neck/shoulder junction. The length of the boattail on the 175SMKs looks to be about 0.170" meaning the bullet's bearing surface sits about 0.020" or so ahead of the junction satisfying the requirement that it not extend into the case beyond this point.

How much this really matters I don't know but it'll be interesting to see what this particular chamber will yield with the 155gr Scenar in terms of jump relative to how close the end of the bearing surface will be to the neck/shoulder junction and what COAL results with similar numbers to the SMKs.

If it looks useable I gotta get me some of them Scenars, Powder Valley has 'em at a decent price at the moment. Come to think of it I haven't run these numbers on the 178 A-Max or the Nosler Custom Competition 155s. Guess I better get around to that eventually since there's a thousand of the first and two thousand of the second sitting around.

Tnx for the heads up on the Scenars, I haven't been paying attention to all the discussion about 'em.
 
#34
Re: 308win Match Reamer?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: justpete</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Vu</div><div class="ubbcode-body">Justpete,

Thanks for the heads up. I wouldnt want to do anything like that.

Could a guy launch 155gn scenars using this reamer? Or would you want to go with a different setup?

Thanks,

Vu </div></div>

Honestly couldn't tell you. Depends on how deep the heel of the bullet sits I guess, I don't have any experience with the Scenars, sorry. You might be able to calculate it from the print though, it's pretty comprehensive. </div></div>

Vu,

Got three samples of the 155gr 30cal Lapua Scenars today. The base to ogive dimension is much more uniform than that of the 175SMKs I tested but the sample size is too small to know if this is actually meaningful.

Casehead to bore diameter intersection with the ogive surface came out to be 2.205" on average with the bullets into the lands enough they had to be bumped out. Bullet base to the same point on the ogive came out to be 0.653" on average and the boattail length is very close to 0.195" from what I can tell.

Using the numbers from before the bearing surface ends about 0.035" ahead of the neck-shoulder junction with zero jump, on average. And with this small sample the variance is only a few thousandths, if that. So you could set up for as much as 0.035" jump and still have the bearing surface above the neck-shoulder junction. Setting the jump to match the 175SMKs at about 0.010" puts the bearing surface about 0.025" ahead of the junction. So there's plenty of play with this chamber to use the Scenar in the same way as you'd use the 175SMK, at least from my limited testing.

Hope this is of some help,
Pete

Added: Reviewed my 175SMK loaded jump data earlier in this thread and the sum of the jump and the bearing surface to neck-shoulder junction is essentially the same as the Scenar so it can be treated the same in terms of chasing the lands with this chamber. Dunno where the optimum for either is but with a 3deg included throat maybe it doesn't really matter all that much, IMHO.

I forgot to check the COAL so I re-setup the 2.205" case/bullet dimension and got 2.845" for a COAL, 0.035" greater than the SAAMI max. So obviously to not exceed SAAMI max the jump has to be set to 0.035", nominal, with the bearing surface just at the neck-shouulder junction. OTOH, if feeding and/or mag length isn't an issue, the COAL difference from SAAMI max probably doesn't matter. For example, to have the same 0.010" jump as the 175SMKs (by not having to dink with the seating die) the COAL would be 0.020", or so, longer than the SMK rounds but their bearing surfaces would be seated to equal depths in the necks of their respective cases. Looks to me like it's going to work fine so I've ordered a box of a hundred to try out. Thanks for the tip.
 
#35
Re: 308win Match Reamer?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Two Shoes</div><div class="ubbcode-body">+1, esp if it is a 5R , 5C/P..............
You will get bad pressure issues, spikes like a bitch. </div></div>

With the Palma Match reamer? Reason I'm asking is I'm thinking of going the 5P route.

What causes the spikes?
 
#36
Re: 308win Match Reamer?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Two Shoes</div><div class="ubbcode-body">+1, esp if it is a 5R , 5C/P..............
You will get bad pressure issues, spikes like a bitch. </div></div>

I cannot agree the 5R, 5C or 5P barrels will somehow generate pressure spikes when a conventional rifled barrel will not, in fact the 5R, 5C or 5P (polygon) types of rifling are generally considered to be easier on pressures than the conventional (English rifling) rifled barrels.
 
#38
Re: 308win Match Reamer?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Goatman007</div><div class="ubbcode-body">Brownells has a pull through chamber reamer. Supposedly used by the Military armorers to get an accuracy advantage
Part # is 184-300-308
Phone is 800-741-0015 </div></div>

Pull Through reamers are used to cut the last few thousandths of the chamber on fixed breach rifles like the M1 and M14.
 
#39
Re: 308win Match Reamer?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: rcw3</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Two Shoes</div><div class="ubbcode-body">+1, esp if it is a 5R , 5C/P..............
You will get bad pressure issues, spikes like a bitch. </div></div>

I cannot agree the 5R, 5C or 5P barrels will somehow generate pressure spikes when a conventional rifled barrel will not, in fact the 5R, 5C or 5P (polygon) types of rifling are generally considered to be easier on pressures than the conventional (English rifling) rifled barrels.

</div></div>

Frankly after thinking about it I really couldn't come up with a good 'hypothesis' in my head as to why they WOULD cause pressure spikes. So, thanks for your confirmation. Perhaps someone else will chime in with their thoughts.
 
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