Freebore, COAL, and chambering specs a miss!

[BBob]

Is the sammi number you keep using the cartridge spec or the chamber spec, they won’t be the same

I don't think he's mixing anything up. SAAMI chamber drawing doesn't list an OAL, only the cartridge portion of the drawing does.

 

[Mike D Texas]

……Just having a long jump doesn't necessarily mean problems like others stated. weatherby cartridges are designed with jump like that.

I was about to say the same thing. Just because it has a lot of jump doesn’t mean it won’t be accurate and there may be additional benefits, much like Weatherby uses.

I have a factory Remington 700 5R in .308. SAAMI length is of course 2.800”. I don’t touch the lands with a 175 Berger VLDH until 3.028”. But it shoots 1/2” groups and gets 2800fps velocity in a 20” barrel with them.


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[SDHNTR]

If you were told you were getting a certain chamber spec and got a different one I can see being upset with the 'smith but that doesn't sound like the case. Beyond that, if it's a bad chamber job or a bad barrel, that could be another thing. Just having a long jump doesn't necessarily mean problems like others stated. weatherby cartridges are designed with jump like that.

So they can send a SAAMI print?

As a place to start yes, so I had specific numbers in which to call their BS, as necessary.

 

[Pickettpuncher]

I don't think he's mixing anything up. SAAMI chamber drawing doesn't list an OAL, only the cartridge portion of the drawing does.
View attachment 627180

But I’m the cartridge part, what’s the spec for freebore.

 

[Buelrdr29]

I was about to say the same thing. Just because it has a lot of jump doesn’t mean it won’t be accurate and there may be additional benefits, much like Weatherby uses.

I have a factory Remington 700 5R in .308. SAAMI length is of course 2.800”. I don’t touch the lands with a 175 Berger VLDH until 3.028”. But it shoots 1/2” groups and gets 2800fps velocity in a 20” barrel with them.


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Thanks for some input. I do appreciate the knowledge gained from others experiences.

I am trying to resolve some inconsistent groups and this is one element I am struggling to agree with on the gun. I have never shot such a big jump on any of my rifles. Even listening to many professional sources it is regular to find the jam length then back out .020 and then start a seating depth test in increments. In my case they wont even clear the chamber for ejection if you decide not to take a shot, let alone the mag length issue. I am not going to single load out hunting and be screwed for a timely 2nd shot.

 

[Mike D Texas]

Thanks for some input. I do appreciate the knowledge gained from others experiences.

I am trying to resolve some inconsistent groups and this is one element I am struggling to agree with on the gun. I have never shot such a big jump on any of my rifles. Even listening to many professional sources it is regular to find the jam length then back out .020 and then start a seating depth test in increments. In my case they wont even clear the chamber for ejection if you decide not to take a shot, let alone the mag length issue. I am not going to single load out hunting and be screwed for a timely 2nd shot.

Generally speaking it’s usually better to have short jump depending on bullet design. But most all bullets will have a long jump window they will shoot well in.

If you are opposed to single feeding then I would start at mag length and work back.


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[stanginthe11s]

im gonna be the odd one out and ask you this. have you considered that the lack of accuracy may be from something else? long jump doesnt always mean poor shooting. you stated you had a load that grouped good, but then it went bad, so maybe you have some other issue.
also, have you tried different bullets and powders or are you limiting yourself to 2 specific bullets/powders?

 

[Tmac]

Do the single shot loading of longer seated bullets as discussed above. If the shorter jump does it, ask them if they can set the barrel back, then rechamber with your desired spec.

 

[Buelrdr29]

im gonna be the odd one out and ask you this. have you considered that the lack of accuracy may be from something else? long jump doesnt always mean poor shooting. you stated you had a load that grouped good, but then it went bad, so maybe you have some other issue.
also, have you tried different bullets and powders or are you limiting yourself to 2 specific bullets/powders?

It has been an issue since the barrel swap. Been messing with it for far too long. I am open to it not being the jump but have chased my tail trying to eliminate everything else.

Yes had a .3" group at 100y and a 3.5 inch at 530y. But also some 3 inch groups at 200y that are not explained with the same ammo. And it is no way I am shooting that bad. I know myself and recognize when I pull a shot.

 

[VAHunter01]

How is the headspace on unfired vs fired brass in that chamber?

 

[stanginthe11s]

have you checked scope, mounts etc. or changed scope? possible bedding issue, torque issue or barrel channel? just thinking of little things that could be missed.

on the ammo side, I've seen strange things before. maybe get away from the 175 gn bullets and try some on either side of that weight? I can tell you my R700 in 308 is the only one that hates anything 168 gn, including FGM but jumping to 178 made a huge difference. maybe trying a 162 or 180 will net better results.​

on the reloading side, have you tried different primers? what's your runout? that may be an issue with the long jump. hate to see you change barrels and spend more money before being 100% sure.

 

[Buelrdr29]

How is the headspace on unfired vs fired brass in that chamber?

I will have to check that. Is there a good way to measure it?

 

[Buelrdr29]

have you checked scope, mounts etc. or changed scope? possible bedding issue, torque issue or barrel channel? just thinking of little things that could be missed.

on the ammo side, I've seen strange things before. maybe get away from the 175 gn bullets and try some on either side of that weight? I can tell you my R700 in 308 is the only one that hates anything 168 gn, including FGM but jumping to 178 made a huge difference. maybe trying a 162 or 180 will net better results.​

on the reloading side, have you tried different primers? what's your runout? that may be an issue with the long jump. hate to see you change barrels and spend more money before being 100% sure.

Have checked a lot of those issues. Also has an aluminum bedding system that has not been a problem before. Have not tried the lighter bullets but may need to give that a try again. Used to use 162s and 168s with the factory barrel.

For primers I cannot even find any so I am using the same old box I have had. Dang market shortages!

 

[VAHunter01]

I will have to check that. Is there a good way to measure it?

Comparators and a mic are the easiest.

Can be done with scotch tape as well, on the base of the brass.

 

[Harvey_NW]

So just did some testing and got different results than with the hornady case length modified case tool.

Made two dummy rounds. One was a resized case with a lubed bullet and the other a fired case and a loctited bullet. Kept the bullets seated too long and pushed them in with the bolt.

The lubed bullet is 3.395 and had about .060 of rifling marks. So probably touching at 3.455.

The loctite one was 3.367 with about the same marks. So touching at 3.427.

The action opening is only 3.344 and the rounds would not eject. Had to pull the bolt out to extract them.

So finding the jam length minus .020 gives about 3.43 ish. That gives a .140 jump to fit the mag.

Measuring those jam marks is inconclusive because of the leade angle in that throat, really doesn't tell you anything except you made contact with the lands. If you put loctite in the neck of a fired case and closed the bolt on it and let it set, that is your best reference measurement. So if it's 3.367" OAL - 3.29" COAL to fit mag = .077" jump.

It has been an issue since the barrel swap. Been messing with it for far too long. I am open to it not being the jump but have chased my tail trying to eliminate everything else.

Yes had a .3" group at 100y and a 3.5 inch at 530y. But also some 3 inch groups at 200y that are not explained with the same ammo. And it is no way I am shooting that bad. I know myself and recognize when I pull a shot.

How big is your sample size? Shoot 10 at 100 and see what it does, if it's around 1 MOA it's a shooter, if it's 2 or more try a new combo. Read this https://rokslide.com/forums/threads/painless-load-development-mine.238400/

 

[Buelrdr29]

Measuring those jam marks is inconclusive because of the leade angle in that throat, really doesn't tell you anything except you made contact with the lands. If you put loctite in the neck of a fired case and closed the bolt on it and let it set, that is your best reference measurement. So if it's 3.367" OAL - 3.29" COAL to fit mag = .077" jump.


How big is your sample size? Shoot 10 at 100 and see what it does, if it's around 1 MOA it's a shooter, if it's 2 or more try a new combo. Read this https://rokslide.com/forums/threads/painless-load-development-mine.238400/

Thanks for the link. I will read through and see if it sparks some new ideas.