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Revised Dec 24/01

 

A Precision 7mmSSAI.

 

 This rifle is made up with quality components. Below is a list of items that went into making this rifle. The rifle has now a permanent scope. A 3-9x42 Kahles CT with a TDS Tri-factor reticle. I very much like this scope. It has extremely good quality optics.

The benefits of the TDS reticle system, is that this reticle provides the shooter with a straight line aim to their target compensating for various ammunition a shooter might select for extended ranges to the target. This reticle also provides an adjustment point for up to a 10mph cross wind at various ranges, an adjustment for an up or down angle shot and compensating reference point for running game. In short this reticle eliminates the need for hold over or lead to a target at extended ranges. (Kahles tech. note.)

For ammo testing I had installed a 4-12 B&L 3000. The rifle is quite heavy and produces very light recoil, which is compatible with my tender shoulder. The weight is 9 lbs. complete with scope.

 

Action: Blueprinted Short Remington 700 BDL.

Trigger: Jewell set at 24 oz.

Magazine box: Lengthened to handle cartridges OAL of 2.975"

Scope mounts: Leupold QD.

Stock: HS-Precision Sporter brown with black web c/w HS recoil pad.

Barrel: HS-Precision 1-11 twist med. Sporter # 7 contours 24" long.

The lack of detailed finishing on the action blue printing is a sore point. Either the gun smith shop don't know or they don't care by having inexperienced help doing precision work. Also the items are minor they should not be.

 Initial Load testing.

Four sets of three cases each were prepped. Three sets made from Remington 7x57 brass and one set from Winchester 30-06 brass. Previously I had used Winchester 7x57 brass but that is not available anymore in Canada. The Remington brass is about 21 grains heavier and has perhaps 2.5 grains less powder capacity. It is also much softer than other brass and expands primer pockets quite easy with less than maximum loads. I had hoped to use the Winchester brass in the new rifle, because I thought of using loads already developed.

This lot of 50 Rem. 7x57 was also the last in the store. Like the previous 7mmSSAI this one was to have a 0.311 chamber neck too but turned out to be 0.3114". The reamer was made by Pacific Precision and is first class. The only difference from one to the other is the shoulder diameter 0.461 this was done to better fit the Redding bushing die, which has a 0.461 shoulder.

Case dimensions: Base 0.469". Shoulder 0.461". Case trim length 2.050". Neck length 0.305". Neck diameter 0.310". Base to neck junction 1.750".

Hodgdon Varget seems like a winner for this case for set 1-2-3 at 100 meters.

46.0 gr Varget - 139 gr Hornady SST- 2975 MV- 3 shots 9/16"c/c- very mild.

46.0 gr Varget - 139 gr Hornady SP Int.- 2940 MV- 3 shots 3/8"c/c- very mild

47.0 gr Varget - 120 gr Nosler Bal.Tip- 3075 MV- 3 shots 5/8"c/c- mild

49.0 gr XMR 4350- 139 gr Hornady SP Int.- 2875 MV- 3 shots 7/8"c/c- too mild.

There is very little load work to do to bring this rifle up to par. The 139 Hornady SST did not perform too well in the other 7mmSSAI but looks pretty good here. The above loads were the first near full loads for the new cases. The cases are nearly fully stretched out and should with the next loads improve the performance and accuracy some more. Also the new cases will operate with less powder and a minor loss in velocity. I now use 30-06 Lapua cases. The Rem cases are used for load testing only or one use hunting loads. They will give up before a maximum load is reached.

It proves here that you don't need to fire 250 rounds of ammo to smooth out a barrel before it starts to group well. The best barrel is the way to go for a new rifle. But then we don't always get what we think we are getting.

Also the groups above were fired in a break in fashion. Shoot one and clean the bore with Kroil and Shooter Choice followed by short stroking with JB Paste and final clean with dry patches after each shot. 3 more sets of 5 and then clean will follow and that will complete the break in.

Before shooting the new barrel was first cleaned, and then treated with a moist moly paste made from Moly and Kroil applied to a tight patch and stroked 10-15 times. The break in bullets were all moly plated. Do not get Moly in the chamber use a Stony Point cleaning sleeve.

 All loads used Remington 9 1/2 primers, which never performed as well in other guns. Federal Match primers could mean another plus but they are not always available in Canada.

The Remington converted Brass holds 57.0 gr of water to top of case and 52.5 gr of Varget to the same level tapped in. Varget /Water volume = bulk density is .912 or .912 represents 100% loading density with 52.5gr of Varget. A load of 46.5 gr of Varget would be 88.6% loading density. Which so far has produced the best accuracy at .350" at 100 meters using the 139 gr Hornady SST bullet at 3004 ft/sec. A load of 47.5 expanded the primer pocket by 0.0003" and is too hot.

My loading density procedure is a little different from the proper one that fills the case with water to the underside of the bullet. But the outcome is only a few percentage points different. Loading density is used only for a starting guide and differs from one powder to another. 85% is a good starting point for most loads. This is a clear example that the 15% reduction in the powder charge is a valid assumption of prudence.

For the case preparation I used the new K&M carbide end cutting mandrel for my K&M outside neck reamer. No more worry about the dreaded doughnut this is a fine addition to the loading bench, in particular when converting brass where part of the case body becomes the new neck. Almost no lube is needed for the carbide mandrel. Ken from K&M exchanged my dull cutters for new ones at no charge. I had sent them to be sharpened. K&M not only make excellent tools but their service is extraordinary.

The conversion of brass is simple but laborious, and featured on my other pages. But here is a quick run down on the 30-06 Lapua brass conversion to the 7mmSSAI. 7x57 Winchester Brass would be easier to form but is not available. I will be testing 7x57 RWS cases when I get them later.

1. Move shoulder down with a 308 Win. sizing die. 2. Trim to 2.125". 3. Full size with a 7mm-08 die without expander button. 4. Inside neck ream with a .25 cal neck reamer 5. Lube inside neck and expand with 7mm K&M Expandrion. 6.Trim case to 2.073". 7. Outside neck ream neck walls to 0.0125" in two operations. One cut is too hard on the tool. 8. Chamfer outside neck. 8. Lapua cases do not need neck annealing. See note below. 9. Install primer. 10. Charge case with 14.5 gr IMR 700X. 11. Fill case tightly with Cream of Wheat. 12. Install Crisco plug. 13. Fire form with neck forced into the throat 0.018" to allow for case shortening. 14. Trim case to final 2.050" and chamfer in and out. 15. Polish inside case necks with 0000 Steel wool using a 30-cal brush and drill press. Primer pocket uniforming and flash hole deburring is not needed with the Lapua cases. Remember this brass has a 0.300" long neck at 2.050". I found the Lapua brass shortened 0.017" during fire forming rather then the usual 0.012".

Note: Outside neck reaming was hard due to the spring back of the tough brass. I used the new K&M end cutting pilot in the drill press and the Forester fixture to remove the spring back, which made outside turning much easier. I think the necks should have been annealed?

The175 gr semi pointed Remington load is the same as the previous one, not as accurate in this rifle as yet?

All Loads for the new7mmSSAI

Brass used

Primer

Powder

Grains

Bullet

Weight

Velocity

Group

Expand

Remark

Rem 7x57

Rem 9-1/2

Varget

46.0

Hornady SST

139gr

2975

9/16

non

.005 to Lands

same

same

same

same

Hornady SP Inter.

139 gr

2936

3/8

non

same

same

Same

same

47.0 gr

Nosler BT

120 gr

3071

5/8

Non

same

Win 30-06

same

XMR 4350

49.0 gr

Horn.SP Inter.

139 gr

2878

7/8

non

same.

Rem 7x57

same

Varget

47.5 gr

Hornady SP Inter

139 gr

3035

0ne shot

0.0009

Loose primer

Same

Same

Varget

47.5 gr

Hornady SST

139 gr

3089

One shot

0.0015

Loose primer

Same

Same

H414

51..5 gr

Hornady SST

139 gr

2949

3/4

non

0.005 to Lands

Win 30-06

Same

XMR 4350

51.. 5 gr

Hornady SST

139 gr

3097

One shot

0.0005

Too hot loose Primer

Rem 7x57

Same

Varget

46.5

Hornady SST

139gr

3012

0.350

0.0002

Max Load

same

same

Varget

46.5

Hornady SST

139 gr

2974

.700"

non

Max Load

Rem 7x57

Rem 9-1/2

XMR 4350

46.5 gr

Rem. Semi Pt.

175 gr

2580

1.25

non

Good Woods Load

Lapua 30-06

CCI 250 Mag

Varget

46.0 gr

Hornady SST

139 gr

3000

1.00"

 

Max Load

Lapua 30-06

CCI 250 Mag

Varget

46.5 gr

Hornady SST

139 gr

3020

3/8

 

Max Load

Lapua 30-06

CCI 250 Mag

Varget

47.0 gr

Hornady SST

139gr

3070

One shot

0.0008

Too Hot loose primer.

Lapua 30-06

CCI 250 Mag

XMR 4350

51.0 gr

Hornady SST

139 gr

3093

1/2"

0.0003

Reduce one gr

Pressure caution. All bullets above were Moly plated. Unplated bullets may show signs of high pressure with above loads. Also this is a custom chamber and loads are not interchangeable with other 7mm-08 AI loads. Reload with safety!

Note: Disclaimer. The above is a description of making modified cartridge cases for my own use for a specific rifle. The above description of making modified cartridge cases and loads is not guarantied to work satisfactory in other rifles and or chambers. Its use could result in bodily harm by unqualified producers with unsuitable tools, firearms and materials. The use of the description for making modified cartridge cases is free of charge and the user of it assumes full responsibility for his or her firearms and safety. Wear safety glasses at all times when shooting and handloading.

Fred The Re-Loader

zermel@shaw.ca

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