Rem 783 and Savage Barrel Differences?

[hoz53]

Thanks guys , sometimes I just have to vent !

Thanks again Ggmac. You helped me alot on this topic. Jarhead got me thinking a little more

 

[GrocMax]

Mossberg MVP 308 (and I believe 4x4 but not positive) has the same pitch diameter and thread count (20tpi) and similar thread depth as a small shank Savage. The bolt recess is similar, in the .115" range. With stock modification a Sav small shank barrel/nut fits, but with any situation like this you can get a stack up tolerance issue, check everything.

Problem with prefits of ANY type is they are often chambered too deep, with worn out, rental (or in dire need of resharpening) reamers. You are much better off being too shallow (increased bolt head to bbl clearance when properly headspaced) than too deep. How much clearance you prefer is up to you, but case support isn't the reason, gas escape clearance due to a ruptured primer/case head separation is the reason.

 

[Ggmac]

Mossberg seems to have 3 different shank sizes , 223 is , can't find my shop notes , but it's less than 1" , ATR is 1"x20 tpi , 308 mvp is reported to be 1.06 x20 and early ones ( maybe based on ATR receivers ) is 1" x20
It stinks getting old !
Gary

 

[hoz53]

Mossberg MVP 308 (and I believe 4x4 but not positive) has the same pitch diameter and thread count (20tpi) and similar thread depth as a small shank Savage. The bolt recess is similar, in the .115" range. With stock modification a Sav small shank barrel/nut fits, but with any situation like this you can get a stack up tolerance issue, check everything.

Problem with prefits of ANY type is they are often chambered too deep, with worn out, rental (or in dire need of resharpening) reamers. You are much better off being too shallow (increased bolt head to bbl clearance when properly headspaced) than too deep. How much clearance you prefer is up to you, but case support isn't the reason, gas escape clearance due to a ruptured primer/case head separation is the reason.

Hi GrocMax. Let's see none of the small shank savage barrels I have seen have a bolt counterbore right? I am not sure I follow your comments on deep or shallow chambers. The bolt head to barrel clearance doesn't necessarily control the chamber depth right? My understanding is when you headspace correctly and the bolt doesn't run into the barrel when you close it you have some bolt nose to barrel clearance. I guess you mean better off having increased bolt to barrel clearance with correct headspace instead of smaller bolt head to barrel clearance on excessive headspace? I will always make sure my headspace is set right. Then the clearance will be what it is. I agree with you on the questionable prefit quality though the Shilen one I have is a good one. I'm at the point now of no more prefits as I have a lathe now and so my idea using a 783 is I can use barrels I have that are to small in diameter to provide a shoulder on a 700 but large enough to thread and use a barrel nut on A 783. I don't want to use a Savage that is one reason I'm interested in the 783. I was planning on re chambering these barrels so I can set chamber depth and bolt clearance to what I want. I need to figure out how deep to chamber at a certain bolt to barrel clearance. Or in other words I need to know ideal bolt to barrel clearance dimension and then I can set headspace at that point. Your comment on the most important reason to have clearance is for gas escape is something I wasn't thinking about Thanks. What is the range of bolt to barrel clearance I can have without causing case failure but allowing enough for gas escape? I will probably set this same as factory inless I find out something better. Thanks for your Reply Hoz

 

[GrocMax]

I guess poor choice of words- bolt head recess/counterbore, the counterbore in the bolt head itself. Savage bolt heads can vary a bit but normal is ~.115" for .378"/.473" bolt heads, normal case head/gauge protrusion from a chamber is in the .125" range BUT many prefits can be quite a bit less than that as error tends to be cut more, not less.

5.56 MVP is 7/8 x 28 thread, and bolt head counterbore depth (on mine at least) is .125". So having a chamber cut to 'normal' Savage spec is not good, on headspacing, you'll touch bolt head to barrel before 0 headspace on the gauge has been found and may not realize it.

More prefits will be cut .005" deeper than spec than .005" shallower but its better to err shallower, then you get a tolerance stackup issue and you headspace a bolt head to a barrel instead of to a gauge and once everything is tight it moves forward one or two thou and you have a long headspaced chamber that felt 'right' on assembly and test cycling.

Always best to check go gauge protrusion from barrel, bolt head counterbore depth, subtract that from go gauge protrusion that is theoretical bolt head to barrel clearance, .010" is about normal for a Savage and leaves room for gas escape and the case is fully supported. What you wish to set for clearance is a personal preference but leave room for dust/dirt/trash clearance at least doncha think?

Now with all that being said, I've had TWO prefits delivered that the chambers were cut too deep and the bolt head hit the barrel at zero headspace. I've had a chamber that had .012" runout compared to the threads at the breech. Multiple well respected companies were responsible for those errors. I quit buying prefits, bought a bunch of tooling, and buy contoured blanks now, they get delivered instantly compared to a prefit as well.

 

[hoz53]

I guess poor choice of words- bolt head recess/counterbore, the counterbore in the bolt head itself. Savage bolt heads can vary a bit but normal is ~.115" for .378"/.473" bolt heads, normal case head/gauge protrusion from a chamber is in the .125" range BUT many prefits can be quite a bit less than that as error tends to be cut more, not less.

5.56 MVP is 7/8 x 28 thread, and bolt head counterbore depth (on mine at least) is .125". So having a chamber cut to 'normal' Savage spec is not good, on headspacing, you'll touch bolt head to barrel before 0 headspace on the gauge has been found and may not realize it.

More prefits will be cut .005" deeper than spec than .005" shallower but its better to err shallower, then you get a tolerance stackup issue and you headspace a bolt head to a barrel instead of to a gauge and once everything is tight it moves forward one or two thou and you have a long headspaced chamber that felt 'right' on assembly and test cycling.

Always best to check go gauge protrusion from barrel, bolt head counterbore depth, subtract that from go gauge protrusion that is theoretical bolt head to barrel clearance, .010" is about normal for a Savage and leaves room for gas escape and the case is fully supported. What you wish to set for clearance is a personal preference but leave room for dust/dirt/trash clearance at least doncha think?

Now with all that being said, I've had TWO prefits delivered that the chambers were cut too deep and the bolt head hit the barrel at zero headspace. I've had a chamber that had .012" runout compared to the threads at the breech. Multiple well respected companies were responsible for those errors. I quit buying prefits, bought a bunch of tooling, and buy contoured blanks now, they get delivered instantly compared to a prefit as well.

Wow GrocMax Thats a lot of good info-some I'm still digesting Thanks

Well Dont think Ill buy a Mossberg so I dont have to be concerned about them

The counterbore depth,gauge protusion and head to barrel dimensions help alot.

I now see how subtracting bolt counterbore depth from go gage protusion gives you barrel/bolt clearance.

I will make sure im headspacing on the gauge and not the barrel/bolt.

Its good to know your experience with prefits as it confirms my thinking on them. Id rather chamber my own and not take a chance on them same as you are doing. For the price of a prefit i gotta believe they dont take much time/care in the setup. I guess i got lucky with the Shilen Its on a savage and i think ill fit it to a 783. All the barrels I plan on buying from now on will be blanks, some strait and some contoured. All of them will probably be fit to Rem 700s though. Mabie not if I like the 783 well enough Ill probably try a new barrel on it. Anyway I plan on fitting quite a few 783 barrels.

Thanks for all the good info-- It got me the rest of the info I needed. Hoz

 

[GrocMax]

Someone was asking about Mossberg MVP 5.56 threads, just sayin', they're 7/8" x 28 UN 2B to be exact.

Tenon diameter is 1.00", inside diameter of nut for tenon clearance is ~1.030", tenon length 1.400", last .075" next to face of tenon unthreaded, .825" diameter. So max barrel diameter unless the nut goes away is 1.00" plus a few thou.

I want to say action diameter is 1.200" but not positive. Bolt body is 5/8". Factory varmint barrels are 1.00" diameter for about 1.25" then taper from there, stocks are pretty tight so any change in profile requires some relief work.

Factory replacement parts are non-existant.

Recoil lug is not pinned, need to make/buy a jig to align recoil lug during assy.

PTG makes a 12 flat nut that a not worn out 12 pt 1 1/16" socket will fit about perfect.

Aftermarket aluminum trigger guards and mag wells are available. Some aftermarket bolt parts (extractor, springs etc.) are out there.

With a barrel and a trigger (Jard, Timney) makes a decent lightweight varminter ideal for smallbore (22, 20, 19, 17) 223 based rounds that can use the mag capacity and OAL restrictions of an AR mag. Them 20 round mags come in handy at times in a target rich environment.

783 probably a better choice of a cheap repeater for most people, unless the mag capacity is a strong positive point for you.

 

[hoz53]

Someone was asking about Mossberg MVP 5.56 threads, just sayin', they're 7/8" x 28 UN 2B to be exact.

Tenon diameter is 1.00", inside diameter of nut for tenon clearance is ~1.030", tenon length 1.400", last .075" next to face of tenon unthreaded, .825" diameter. So max barrel diameter unless the nut goes away is 1.00" plus a few thou.

I want to say action diameter is 1.200" but not positive. Bolt body is 5/8". Factory varmint barrels are 1.00" diameter for about 1.25" then taper from there, stocks are pretty tight so any change in profile requires some relief work.

Factory replacement parts are non-existant.

Recoil lug is not pinned, need to make/buy a jig to align recoil lug during assy.

PTG makes a 12 flat nut that a not worn out 12 pt 1 1/16" socket will fit about perfect.

Aftermarket aluminum trigger guards and mag wells are available. Some aftermarket bolt parts (extractor, springs etc.) are out there.

With a barrel and a trigger (Jard, Timney) makes a decent lightweight varminter ideal for smallbore (22, 20, 19, 17) 223 based rounds that can use the mag capacity and OAL restrictions of an AR mag. Them 20 round mags come in handy at times in a target rich environment.

783 probably a better choice of a cheap repeater for most people, unless the mag capacity is a strong positive point for you.

Thanks for the additional info on the Mossberg Groc. Never hurts to have it for sure. The AR mag would be handy. I'll look at one of those MVPs at the store.

 

[JarheadAZ]

Cool...

 

[GrocMax]

Thanks for the additional info on the Mossberg Groc. Never hurts to have it for sure. The AR mag would be handy. I'll look at one of those MVPs at the store.

AR mag is not really very good for 223-up (6x45, 6TCU etc.) and varminting, works better for 20 cal and under due to the 2.260"ish OAL restriction. PERFECT for 20 Prac. Lots of 223 chambers you can't get close to the lands at 2.260" and 55g-under varmint bullets. MVP is light, be better in my opinion as a 223 based 20 or 17.

 

[hoz53]

AR mag is not really very good for 223-up (6x45, 6TCU etc.) and varminting, works better for 20 cal and under due to the 2.260"ish OAL restriction. PERFECT for 20 Prac. Lots of 223 chambers you can't get close to the lands at 2.260" and 55g-under varmint bullets. MVP is light, be better in my opinion as a 223 based 20 or 17.

Thanks for the info Groc. I don't think I'll be buying a MVP anytime soon but I've got to deal with the mag length in my ar15s.

 

[mbappe]

All this and not one direct reference to the term Chamber Protrusion...

The term refers to the distance a chambered cartridge extends out from the chambered barrel's breech face. This protrusion distance is based on the cartridge base recess in the bolt face and a factor for bolt to barrel clearance.

I watched a heated battle proceed on another site some years back about whether or not a Savage drop-in barrel would work with a Mossberg receiver and bolt. They will thread together, but the protrusion mismatch could result in a case rupture at the gap where the case is actually unsupported for a small portion of its length in that application.

Protrusion is a key measurement, and must be correct.

Greg

I'm not a gunsmith. I'm not even a very experienced hobbyist. So please take it easy on me for what I'm about to ask. Doesn't the gap between the bolt nose and the barrel match up with the extractor groove in the case? How can that part of the case ever rely on any support from the barrel or bolt since it doesn't touch either? Isn't this precisely why the barrel nut method is a viable way to set headspace? Furthermore, is it not safe to use the same bolt head for a cartridge with a rim diameter of .473 and another cartridge with a rim diameter of .467? Doesn't this imply that the only support provided for the case by the bolt is provided by the face itself? Seems like the purpose of the ring around the bolt face is simply to prevent the case from running away from the spring loaded extractor.